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64. Agriculture and Natural Resources Based Industries

64. Agriculture and Natural Resources Based Industries (34)

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64. Agriculture and Natural Resources Based Industries

Chapter Editor: Melvin L. Myers

Table of Contents

Tables and Figures

General Profile
Melvin L. Myers

     Case Study: Family Farms
     Ted Scharf, David E. Baker and Joyce Salg

Farming  Systems

Melvin L. Myers and I.T. Cabrera

Migrant and Seasonal Farmworkers
Marc B. Schenker

Urban Agriculture
Melvin L. Myers

Greenhouse and Nursery Operations
Mark M. Methner and John A. Miles

Samuel H. Henao

Farmworker Education about Pesticides: A Case Study
Merri Weinger

Planting and Growing Operations
Yuri Kundiev and V.I. Chernyuk

Harvesting Operations
William E. Field

Storing and Transportation Operations
Thomas L. Bean

Manual Operations in Farming
Pranab Kumar Nag

Dennis Murphy

     Case Study: Agricultural Machinery
     L. W. Knapp, Jr.

Food  and Fibre Crops

Malinee Wongphanich

Agricultural Grains and Oilseeds
Charles Schwab

Sugar Cane Cultivation and Processing
R.A. Munoz, E.A. Suchman, J.M. Baztarrica and Carol J. Lehtola

Potato Harvesting
Steven Johnson

Vegetables and Melons
B.H. Xu and Toshio Matsushita   

Tree,  Bramble and Vine Crops

Berries and Grapes
William E. Steinke

Orchard Crops
Melvin L. Myers

Tropical Tree and Palm Crops
Melvin L. Myers

Bark and Sap Production
Melvin L. Myers

Bamboo and Cane
Melvin L. Myers and Y.C. Ko

Specialty  Crops

Tobacco Cultivation
Gerald F. Peedin

Ginseng, Mint and Other Herbs
Larry J. Chapman

L.J.L.D. Van Griensven

Aquatic Plants
Melvin L. Myers and J.W.G. Lund

Beverage Crops

Coffee Cultivation
Jorge da Rocha Gomes and Bernardo Bedrikow

Tea Cultivation
L.V.R. Fernando

Thomas Karsky and William B. Symons

Health  and Environmental Issues

Health Problems and Disease Patterns in Agriculture
Melvin L. Myers

     Case Study: Agromedicine
     Stanley H. Schuman and Jere A. Brittain

Environmental and Public Health Issues in Agriculture
Melvin L. Myers


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1. Sources of nutrients
2. Ten steps for a plantation work risk survey
3. Farming systems in urban areas
4. Safety advice for lawn & garden equipment
5. Categorization of farm activities
6. Common tractor hazards & how they occur
7. Common machinery hazards & where they occur
8. Safety precautions
9. Tropical & subtropical trees, fruits & palms
10. Palm products
11. Bark & sap products & uses
12. Respiratory hazards
13. Dermatological hazards
14. Toxic & neoplastic hazards
15. Injury hazards
16. Lost time injuries, United States, 1993
17. Mechanical & thermal stress hazards
18. Behavioural hazards
19. Comparison of two agromedicine programmes
20. Genetically engineered crops
21. Illicit drug cultivation, 1987, 1991 & 1995


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65. Beverage Industry

65. Beverage Industry (10)

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65. Beverage Industry

Chapter Editor: Lance A. Ward

Table of Contents

Tables and Figures

General Profile
David Franson

Soft Drink Concentrate Manufacturing
Zaida Colon

Soft Drink Bottling and Canning
Matthew Hirsheimer

Coffee Industry
Jorge da Rocha Gomes and Bernardo Bedrikow

Tea Industry
Lou Piombino

Distilled Spirits Industry
R.G. Aldi and Rita Seguin

Wine Industry
Alvaro Durao

Brewing Industry
J.F. Eustace

Health and Environmental Concerns
Lance A. Ward


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1. Selected coffee importers (in tonnes)


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66. Fishing

66. Fishing (10)

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66. Fishing

Chapter Editors: Hulda Ólafsdóttir and Vilhjálmur Rafnsson

Table of Contents

Tables and Figures

General Profile
Ragnar Arnason

     Case Study: Indigenous Divers
     David Gold

Major Sectors and Processes
Hjálmar R. Bárdarson

Psychosocial Characteristics of the Workforce at Sea
Eva Munk-Madsen

     Case Study: Fishing Women

Psychosocial Characteristics of the Workforce in On-Shore Fish Processing
Marit Husmo

Social Effects of One-Industry Fishery Villages
Barbara Neis

Health Problems and Disease Patterns
Vilhjálmur Rafnsson

Musculoskeletal Disorders Among Fishermen and Workers in the Fish Processing Industry
Hulda Ólafsdóttir

Commercial Fisheries: Environmental and Public Health Issues
Bruce McKay and Kieran Mulvaney


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1. Mortality figures on fatal injuries among fishermen
2. The most important jobs or places related to risk of injuries


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67. Food Industry

67. Food Industry (11)

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67. Food Industry

Chapter Editor: Deborah E. Berkowitz

Table of Contents

Tables and Figures

Overview and Health Effects

Food Industry Processes
M. Malagié, G. Jensen, J.C. Graham and Donald L. Smith

Health Effects and Disease Patterns
John J. Svagr

Environmental Protection and Public Health Issues
Jerry Spiegel

Food Processing Sectors

Deborah E. Berkowitz and Michael J. Fagel

Poultry Processing
Tony Ashdown

Dairy Products Industry
Marianne Smukowski and Norman Brusk

Cocoa Production and the Chocolate Industry
Anaide Vilasboas de Andrade

Grain, Grain Milling and Grain-Based Consumer Products
Thomas E. Hawkinson, James J. Collins and Gary W. Olmstead

R.F. Villard

Sugar-Beet Industry
Carol J. Lehtola

Oil and Fat
N.M. Pant


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1. The food industries, their raw materials & processes
2. Common occupational diseases in the food & drink industries
3. Types of infections reported in food & drink industries
4. Examples of uses for by-products from the food industry
5. Typical water reuse ratios for different industry sub-sectors


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68. Forestry

68. Forestry (17)

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68. Forestry

Chapter Editor: Peter Poschen

Table of Contents

Tables and Figures

General Profile
Peter Poschen

Wood Harvesting
Dennis Dykstra and Peter Poschen

Timber Transport
Olli Eeronheimo

Harvesting of Non-wood Forest Products
Rudolf Heinrich

Tree Planting
Denis Giguère

Forest Fire Management and Control
Mike Jurvélius

Physical Safety Hazards
Bengt Pontén

Physical Load
Bengt Pontén

Psychosocial Factors
Peter Poschen and Marja-Liisa Juntunen

Chemical Hazards
Juhani Kangas

Biological Hazards among Forestry Workers
Jörg Augusta

Rules, Legislation, Regulations and Codes of Forest Practices
Othmar Wettmann

Personal Protective Equipment
Eero Korhonen

Working Conditions and Safety in Forestry Work
Lucie Laflamme and Esther Cloutier

Skills and Training
Peter Poschen

Living Conditions
Elías Apud

Environmental Health Issues
Shane McMahon


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1. Forest area by region (1990)
2. Non-wood forest product categories & examples
3. Non-wood harvesting hazards & examples
4. Typical load carried while planting
5. Grouping of tree-planting accidents by body parts affected
6. Energy expenditure in forestry work
7. Chemicals used in forestry in Europe & North America in the 1980s
8. Selection of infections common in forestry
9. Personal protective equipment appropriate for forestry operations
10. Potential benefits to environmental health


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69. Hunting

69. Hunting (2)

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69. Hunting

Chapter Editor: George A. Conway

Table of Contents


A Profile of Hunting and Trapping in the 1990s
John N. Trent

Diseases Associated with Hunting and Trapping
Mary E. Brown


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1. Examples of diseases potentially significant to hunters & trappers

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70. Livestock Rearing

70. Livestock Rearing (21)

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70. Livestock Rearing

Chapter Editor: Melvin L. Myers

Table of Contents

Tables and Figures

Livestock Rearing: Its Extent and Health Effects
Melvin L. Myers

Health Problems and Disease Patterns
Kendall Thu, Craig Zwerling and Kelley Donham

     Case Study: Arthopod-related Occupational Health Problems
     Donald Barnard

Forage Crops
Lorann Stallones

Livestock Confinement
Kelley Donham

Animal Husbandry
Dean T. Stueland and Paul D. Gunderson

     Case Study: Animal Behaviour
     David L. Hard

Manure and Waste Handling
William Popendorf

     A Checklist for Livestock Rearing Safety Practice
     Melvin L. Myers

John May

Cattle, Sheep and Goats
Melvin L. Myers

Melvin L. Myers

Poultry and Egg Production
Steven W. Lenhart

     Case Study: Poultry Catching, Live Hauling and Processing
     Tony Ashdown

Horses and Other Equines
Lynn Barroby

     Case Study: Elephants
     Melvin L. Myers

Draught Animals in Asia
D.D. Joshi

Bull Raising
David L. Hard

Pet, Furbearer and Laboratory Animal Production
Christian E. Newcomer

Fish Farming and Aquaculture
George A. Conway and Ray RaLonde

Beekeeping, Insect Raising and Silk Production
Melvin L. Myers and Donald Barnard


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1. Livestock uses
2. International livestock production (1,000 tonnes)
3. Annual US livestock faeces & urine production
4. Types of human health problems associated with livestock
5. Primary zoonoses by world region
6. Different occupations & health & safety
7. Potential arthropod hazards in the workplace
8. Normal & allergic reactions to insect sting
9. Compounds identified in swine confinement
10. Ambient levels of various gases in swine confinement
11. Respiratory diseases associated with swine production
12. Zoonotic diseases of livestock handlers
13. Physical properties of manure
14. Some important toxicologic benchmarks for hydrogen sulphide
15. Some safety procedures related to manure spreaders
16. Types of ruminants domesticated as livestock
17. Livestock rearing processes & potential hazards
18. Respiratory illnesses from exposures on livestock farms
19. Zoonoses associated with horses
20. Normal draught power of various animals


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71. Lumber

71. Lumber (4)

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71. Lumber

Chapter Editors: Paul Demers and Kay Teschke

Table of Contents

Tables and Figures

General Profile
Paul Demers

Major Sectors and Processes: Occupational Hazards and Controls
Hugh Davies, Paul Demers, Timo Kauppinen and Kay Teschke

Disease and Injury Patterns
Paul Demers

Environmental and Public Health Issues
Kay Teschke and Anya Keefe


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1. Estimated wood production in 1990
2. Estimated production of lumber for the 10 largest world producers
3. OHS hazards by lumber industry process area


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72. Paper and Pulp Industry

72. Paper and Pulp Industry (13)

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72. Paper and Pulp Industry

Chapter Editors: Kay Teschke and Paul Demers

Table of Contents

Tables and Figures

General Profile
Kay Teschke

Major Sectors and Processes

Fibre Sources for Pulp and Paper
Anya Keefe and Kay Teschke

Wood Handling
Anya Keefe and Kay Teschke

Anya Keefe, George Astrakianakis and Judith Anderson

George Astrakianakis and Judith Anderson

Recycled Paper Operations
Dick Heederik

Sheet Production and Converting: Market Pulp, Paper, Paperboard
George Astrakianakis and Judith Anderson

Power Generation and Water Treatment
George Astrakianakis and Judith Anderson

Chemical and By-product Production
George Astrakianakis and Judith Anderson

Occupational Hazards and Controls
Kay Teschke, George Astrakianakis, Judith Anderson, Anya Keefe and Dick Heederik

Disease and Injury Patterns

Injuries and Non-malignant Diseases
Susan Kennedy and Kjell Torén

Kjell Torén and Kay Teschke

Environmental and Public Health Issues
Anya Keefe and Kay Teschke


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1. Employment & production in selected countries (1994)
2. Chemical constituents of pulp & paper fibre sources
3. Bleaching agents & their conditions of use
4. Papermaking additives
5. Potential health & safety hazards by process area
6. Studies on lung & stomach cancer, lymphoma & leukaemia
7. Suspensions & biological oxygen demand in pulping


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Thursday, 10 March 2011 15:48


The world’s most widely cultivated edible fungi are: the common white button mushroom, Agaricus bisporus, with an annual production in 1991 of approximately 1.6 million tonnes; the oyster mushroom, Pleurotus spp. (about 1 million tonnes); and the shiitake, Lentinus edodes (about 0.6 million tonnes) (Chang 1993). Agaricus is mainly grown in the western hemisphere, whereas oyster mushrooms, shiitake and a number of other fungi of lesser production are mostly produced in East Asia.

The production of Agaricus and the preparation of its substrate, compost, are for a large part strongly mechanized. This is generally not the case for the other edible fungi, although exceptions exist.

The Common Mushroom

The common white button mushroom, Agaricus bisporus, is grown on compost consisting of a fermented mixture of horse manure, wheat straw, poultry manure and gypsum. The materials are wetted, mixed and set in large heaps when fermented outdoors, or brought into special fermentation rooms, called tunnels. Compost is usually made in quantities of up to several hundred tonnes per batch, and large, heavy equipment is used for mixing heaps and for filling and emptying the tunnels. Composting is a biological process that is guided by a temperature regime and that requires thorough mixing of the ingredients. Before being used as a substrate for growth, compost should be pasteurized by heat treatment and conditioned to get rid of the ammonia. During composting, a considerable amount of sulphur-containing organic volatiles evaporates, which can cause odour problems in the surroundings. When tunnels are used, the ammonia in the air can be cleaned by acid washing, and odour escape can be prevented by either biological or chemical oxidation of the air (Gerrits and Van Griensven 1990).

The ammonia-free compost is then spawned (i.e., inoculated with a pure culture of Agaricus growing on sterilized grain). Mycelial growth is carried out during a 2-week incubation at 25 °C in a special room or in a tunnel, after which the grown compost is placed in growing rooms in trays or in shelves (i.e., a scaffold system with 4 to 6 beds or tiers above each other with a distance of 25 to 40 cm in between), covered with a special casing consisting of peat and calcium carbonate. After a further incubation, mushroom production is induced by a temperature change combined with strong ventilation. Mushrooms appear in flushes with weekly intervals. They are either harvested mechanically or hand-picked. After 3 to 6 flushes, the growing room is cooked out (i.e., steam pasteurized), emptied, cleaned and disinfected, and the next growing cycle can be started.

Success in mushroom cultivation depends heavily on cleanliness and prevention of pests and diseases. Although management and farm hygiene are key factors in disease prevention, a number of disinfectants and a limited number of pesticides and fungicides are still used in the industry.

Health Risks

Electrical and mechanical equipment

A pre-eminent risk in mushroom farms is the accidental exposure to electricity. Often high voltage and amperage is used in humid environments. Ground fault circuit interrupters and other electrical precautions are necessary. National labour legislation usually sets rules for the protection of labourers; this should be strictly followed.

Also, mechanical equipment may pose dangerous threats by its damaging weight or function, or by the combination of both. Composting machines with their large moving parts require care and attention to prevent accidents. Equipment used in cultivation and harvesting often has rotating parts used as grabbers or harvesting knives; their use and transport require great care. Again, this holds for all machines that are moving, whether they be self-propelled or pulled over beds, shelves or rows of trays. All such equipment should be properly guarded. All personnel whose duties include handling electrical or mechanical equipment in mushroom farms should be carefully trained before work is started and safety rules should be adhered to. Maintenance ordinances of equipment and machines should be taken very seriously. A proper lockout/tagout programme is needed as well. Lack of maintenance causes mechanical equipment to become extremely dangerous. For example, breaking pull chains have caused several deaths in mushroom farms.

Physical factors

Physical factors such as climate, lighting, noise, muscle load and posture strongly influence the health of workers. The difference between ambient outside temperature and that of a growing room can be considerable, especially in the winter. One should allow the body to adapt to a new temperature with every change of location; not doing so may lead to diseases of the airways and eventually to a susceptibility to bacterial and viral infections. Further, exposure to excessive temperature changes may cause muscles and joints to become stiff and inflamed. This may lead to a stiff neck and back, a painful condition causing unfitness for work.

Insufficient lighting in mushroom-growing rooms not only causes dangerous working conditions but also slows down picking, and it prevents pickers from seeing the possible symptoms of disease in the crop. The lighting intensity should be at least 500 lux.

Muscle load and posture largely determine the weight of labour. Unnatural body positions are often required in manual cultivation and picking tasks due to the limited space in many growing rooms. Those positions may damage joints and cause static overload of the muscles; prolonged static loading of muscles, such as that which occurs during picking, can even cause inflammation of joints and muscles, eventually leading to partial or total loss of function. This can be prevented by regular breaks, physical exercises and ergonomic measures (i.e., adaptation of the actions to the dimensions and possibilities of the human body).

Chemical factors

Chemical factors such as exposure to hazardous substances create possible health risks. The large-scale preparation of compost has a number of processes that can pose lethal risks. Gully pits in which recirculation water and drainage from compost is collected are usually devoid of oxygen, and the water contains high concentrations of hydrogen sulphide and ammonia. A change in acidity (pH) of the water may cause a lethal concentration of hydrogen sulphide to occur in the areas surrounding the pit. Piling wet poultry or horse manure in a closed hall may cause the hall to become an essentially lethal environment, due to the high concentrations of carbon dioxide, hydrogen sulphide and ammonia which are generated. Hydrogen sulphide has a powerful odour at low concentrations and is especially threatening, since at lethal concentrations this compound appears to be odourless because it inactivates human olfactory nerves. Indoor compost tunnels do not have sufficient oxygen to support human life. They are confined spaces, and testing of air for oxygen content and toxic gases, wearing of appropriate PPE, having an outside guard and proper training of involved personnel are essential.

Acid washers used for removal of ammonia from the air of compost tunnels require special care because of the large quantities of strong sulphuric or phosphoric acid that are present. Local exhaust ventilation should be provided.

Exposure to disinfectants, fungicides and pesticides can take place through the skin by exposure, through the lungs by breathing, and through the mouth by swallowing. Usually fungicides are applied by a high-volume technique such as by spray lorries, spray guns and drenching. Pesticides are applied with low-volume techniques such as misters, dynafogs, turbofogs and by fumigation. The small particles that are created remain in the air for hours. The right protective clothing and a respirator that has been certified as appropriate for the chemicals involved should be worn. Although the effects of acute poisoning are very dramatic, it should not be forgotten that the effects of chronic poisoning, although less dramatic at first glance, also always require occupational health surveillance.

Biological factors

Biological agents can cause infectious diseases as well as severe allergic reactions (Pepys 1967). No human infectious disease cases caused by the presence of human pathogens in compost have been reported. However, mushroom worker’s lung (MWL) is a severe respiratory disease that is associated with handling the compost for Agaricus (Bringhurst, Byrne and Gershon-Cohen 1959). MWL, which belongs to the group of diseases designated extrinsic allergic alveolitis (EAA), arise from exposure to spores of the thermophilic actinomycetes Excellospora flexuosa, Thermomonospora alba, T. curvata and T. fusca that have grown during the conditioning phase in compost. They can be present in high concentrations in the air during spawning of phase 2 compost (i.e., over 109 colony-forming units (CFU) per cubic metre of air) (Van den Bogart et al. 1993); for causation of EAA symptoms, 108 spores per cubic metre of air are sufficient (Rylander 1986). The symptoms of EAA and thus MWL are fever, difficult respiration, cough, malaise, increase in number of leukocytes and restrictive changes of lung function, starting only 3 to 6 hours after exposure (Sakula 1967; Stolz, Arger and Benson 1976). After a prolonged period of exposure, irreparable damage is done to the lung due to inflammation and reactive fibrosis. In one study in the Netherlands, 19 MWL patients were identified among a group of 1,122 workers (Van den Bogart 1990). Each patient demonstrated a positive response to inhalation provocation and possessed circulating antibodies against spore antigens of one or more of the actinomycetes mentioned above. No allergic reaction had been found with Agaricus spores (Stewart 1974), which may indicate low antigenicity of the mushroom itself or low exposure. MWL can easily be prevented by providing workers with powered air-purifying respirators equipped with a fine dust filter as part of their normal work gear during spawning of compost.

Some pickers have been found to suffer from damaged skin of finger tips, caused by exogenous glucanases and proteases of Agaricus. Wearing gloves during picking prevents this.


Mushroom growing has a short and complicated growing cycle. Thus managing a mushroom farm brings worries and tensions which may extend to the workforce. Stress and its management are discussed elsewhere in this Encyclopaedia.

The Oyster Mushroom

Oyster mushrooms, Pleurotus spp., can be grown on a number of different lignocellulose-containing substrates, even on cellulose itself. The substrate is wetted and usually pasteurized and conditioned. After spawning, mycelial growth takes place in trays, shelves, special containers or in plastic bags. Fructification takes place when the ambient carbon dioxide concentration is decreased by ventilation or by opening the container or bag.

Health risks

Health risks associated with the cultivation of oyster mushrooms are comparable to those linked to Agaricus as described above, with one major exception. All Pleurotus species have naked lamellae (i.e., not covered by a veil), which results in the early shedding of a large number of spores. Sonnenberg, Van Loon and Van Griensven (1996) have counted spore production in Pleurotus spp. and found up to a billion spores produced per gram of tissue per day, depending on species and developmental stage. The so-called sporeless varieties of Pleurotus ostreatus produced about 100 million spores. Many reports have described the occurrence of EAA symptoms after exposure to Pleurotus spores (Hausen, Schulz and Noster 1974; Horner et al. 1988; Olson 1987). Cox, Folgering and Van Griensven (1988) have established the causal relation between exposure to Pleurotus spores and occurrence of EAA symptoms caused by inhalation. Because of the serious nature of the disease and the high sensitivity of humans, all workers should be protected with dust respirators. Spores in the growing room should at least partially be removed before workers enter the room. This can be done by directing the circulation air over a wet filter or by setting ventilation at full power 10 minutes before workers enter the room. Weighing and packing of mushrooms can be done under a hood, and during storage the trays should be covered by foil to prevent release of spores into the working environment.

Shiitake Mushrooms

In Asia this tasty mushroom, Lentinus edodes, has been grown on wood logs in the open air for centuries. The development of a low-cost cultivation technique on artificial substrate in growing rooms rendered its culture economically feasible in the western world. The artificial substrates usually consist of a wetted mixture of hardwood sawdust, wheat straw and high-concentration protein meal, which is pasteurized or sterilized before spawning. Mycelial growth takes place in bags, or in trays or shelves, depending on the system used. Fruiting is commonly induced by temperature shock or by immersion in ice-cold water, as is done to induce production on wood logs. Due to its high acidity (low pH), the substrate is susceptible to infection by green moulds such as Penicillium spp. and Trichoderma spp. Prevention of the growth of those heavy sporulators requires either sterilization of the substrate or use of fungicides.

Health risks

The health risks associated with the cultivation of shiitake are comparable with those of Agaricus and Pleurotus. Many strains of shiitake sporulate easily, leading to concentrations of up to 40 million spores per cubic metre of air (Sastre et al. 1990).

Indoor cultivation of shiitake has regularly led to EAA symptoms in workers (Cox, Folgering and Van Griensven 1988, 1989; Nakazawa, Kanatani and Umegae 1981; Sastre et al. 1990) and inhalation of spores of shiitake is the cause of the disease (Cox, Folgering and Van Griensven 1989). Van Loon et al. (1992) have shown that in a group of 5 patients tested, all had circulating IgG-type antibodies against shiitake spore antigens. Despite the use of protective mouth masks, a group of 14 workers experienced a rise in antibody titres with increased duration of employment, indicating the need for better prevention, such as powered air-purifying respirators and appropriate engineering controls.

Acknowledgement: The view and results presented here are strongly influenced by the late Jef Van Haaren, M.D., a fine person and gifted occupational health physician, whose humane approach to the effects of human labour was best reflected in Van Haaren (1988), his chapter in my textbook that formed the basis of the present article.



Thursday, 10 March 2011 15:50

Aquatic Plants

Adapted from J.W.G. Lund’s article, “Algae”, “Encyclopaedia of Occupational Health and Safety,” 3rd edition.

Worldwide aquaculture production totalled 19.3 million tonnes in 1992, of which 5.4 million tonnes came from plants. In addition, much of the feed used on fish farms is water plants and algae, contributing to their growth as a part of aquaculture.

Water plants that are grown commercially include water spinach, watercress, water chestnuts, lotus stems and various seaweeds, which are grown as low-cost foods in Asia and Africa. Floating water plants that have commercial potential are duckweed and water hyacinth (FAO 1995).

Algae are a diverse group of organisms; if the cyanobacteria (blue-green algae) are included, they come in a range of sizes from bacteria (0.2 to 2 microns) to giant kelps (40 m). All algae are capable of photosynthesis and can liberate oxygen.

Algae are nearly all aquatic, but they may also live as a dual organism with fungi as lichens on drier rocks and on trees. Algae are found wherever there is moisture. Plant plankton consists almost exclusively of algae. Algae abound in lakes and rivers, and on the seashore. The slipperiness of stones and rocks, the slimes and discolourations of water usually are formed by aggregations of microscopic algae. They are found in hot springs, snowfields and Antarctic ice. On mountains they can form dark slippery streaks (Tintenstriche) that are dangerous to climbers.

There is no general agreement about algae classification, but they are commonly divided into 13 major groups whose members may differ markedly from one group to another in colour. The blue-green algae (Cyanophyta) are also considered by many microbiologists to be bacteria (Cyanobacteria) because they are procaryotes, which lack the membrane-bounded nuclei and other organelles of eukaryotic organisms. They are probably descendants of the earliest photosynthetic organisms, and their fossils have been found in rocks some 2 billion years old. Green algae (Chlorophyta), to which Chlorella belongs, has many of the characteristics of other green plants. Some are seaweeds, as are most of the red (Rhodophyta) and brown (Phaeophyta) algae. Chrysophyta, usually yellow or brownish in colour, include the diatoms, algae with walls made of polymerized silicon dioxide. Their fossil remains form industrially valuable deposits (Kieselguhr, diatomite, diatomaceous earth). Diatoms are the main basis of life in the oceans and contribute about 20 to 25% of the world’s plant production. Dinoflagellates (Dinophyta) are free-swimming algae especially common in the sea; some are toxic.


Water culture can vary greatly from the traditional 2-month to annual growing cycle of planting, then fertilizing and plant maintenance, followed by harvesting, processing, storage and sale. Sometimes the cycle is compressed to 1 day, such as in duckweed farming. Duckweed is the smallest flowering plant.

Some seaweeds are valuable commercially as sources of alginates, carrageenin and agar, which are used in industry and medicine (textiles, food additives, cosmetics, pharmaceuticals, emulsifiers and so on). Agar is the standard solid medium on which bacteria and other micro-organisms are cultivated. In the Far East, especially in Japan, a variety of seaweeds are used as human food. Seaweeds are good fertilizers, but their use is decreasing because of the labour costs and the availability of relatively cheap artificial fertilizers. Algae play an important part in tropical fish farms and in rice fields. The latter are commonly rich in Cyanophyta, some species of which can utilize nitrogen gas as their sole source of nitrogenous nutrient. As rice is the staple diet of the majority of the human race, the growth of algae in rice fields is under intensive study in countries such as India and Japan. Certain algae have been employed as a source of iodine and bromine.

The use of industrially cultivated microscopic algae has often been advocated for human food and has a potential for very high yields per unit area. However, the cost of dewatering has been a barrier.

Where there is a good climate and inexpensive land, algae can be used as part of the process of sewage purification and harvested as animal food. While a useful part of the living world of reservoirs, too much algae can seriously impede, or increase the cost of water supply. In swimming pools, algal poisons (algicides) can be used to control algal growth, but, apart from copper in low concentrations, such substances cannot be added to water or domestic supplies. Over-enrichment of water with nutrients, notably phosphorus, with consequent excessive growth of algae, is a major problem in some regions and has led to bans on the use of phosphorus-rich detergents. The best solution is to remove the excess phosphorus chemically in a sewage plant.

Duckweed and a water hyacinth are potential livestock feeds, compost input or fuel. Aquatic plants are also used as feed for noncarnivorous fish. Fish farms produce three primary commodities: finfish, shrimp and mollusc. Of the finfish portion, 85% are made up of noncarnivorous species, primarily the carp. Both the shrimp and mollusc depend upon algae (FAO 1995).


Abundant growths of freshwater algae often contain potentially toxic blue-green algae. Such “water blooms” are unlikely to harm humans because the water is so unpleasant to drink that swallowing a large and hence dangerous amount of algae is unlikely. On the other hand, cattle may be killed, especially in hot, dry areas where no other source of water may be available to them. Paralytic shellfish poisoning is caused by algae (dinoflagellates) on which the shellfish feed and whose powerful toxin they concentrate in their bodies with no apparent harm to themselves. Humans, as well as marine animals, can be harmed or killed by the toxin.

Prymnesium (Chrysophyta) is very toxic to fish and flourishes in weakly or moderately saline water. It presented a major threat to fish farming in Israel until research provided a practical method of detecting the presence of the toxin before it reached lethal proportions. A colourless member of the green algae (Prototheca) infects humans and other mammals from time to time.

There have been a few reports of algae causing skin irritations. Oscillatoria nigroviridis are known to cause dermatitis. In freshwater, Anaebaena, Lyngbya majuscula and Schizothrix can cause contact dermatitis. Red algae are known to cause breathing distress. Diatoms contain silica, so they could pose a silicosis hazard as a dust. Drowning is a hazard when working in deeper water while cultivating and harvesting water plants and algae. The use of algicides also poses hazards, and precautions provided on the pesticide label should be followed.



Thursday, 10 March 2011 16:03

Tea Cultivation

Adapted from 3rd edition, “Encyclopaedia of Occupational Health and Safety”.

Tea (Camellia sinensis) was originally cultivated in China, and most of the world’s tea still comes from Asia, with lesser quantities from Africa and South America. Ceylon and India are now the largest producers, but sizeable quantities also come from China, Japan, the former USSR, Indonesia and Pakistan. The Islamic Republic of Iran, Turkey, Viet Nam and Malaysia are small-scale growers. Since the Second World War, the area under tea cultivation in Africa has been expanding rapidly, particularly in Kenya, Mozambique, Congo, Malawi, Uganda and the United Republic of Tanzania. Mauritius, Rwanda, Cameroon, Zambia and Zimbabwe also have small acreages. The main South American producers are Argentina, Brazil and Peru.


Tea is most efficiently and economically produced in large plantations, although it is also grown as a smallholder crop. In Southeast Asia, the tea plantation is a self-contained unit, providing accommodation and all facilities for its workers and their families, each unit forming a virtually closed community. Women form a large proportion of the workers in India and Ceylon, but the pattern is somewhat different in Africa, where mainly male migrant and seasonal labour is employed and families do not have to be housed. See also the article “Plantations” [AGR03AE] in this chapter.


Land is cleared and prepared for new planting, or areas of old, poor-quality tea are uprooted and replanted with high-yielding vegetatively propagated cuttings. New fields take a couple of years to come into full bearing. Regular programmes of manuring, weeding and pesticide application are carried on throughout the year.

The plucking of the young tea leaves—the famous “two leaves and a bud”—takes place the year round in most of Southeast Asia, but is restricted in areas with a marked cold season (see figure 1). After a cycle of plucking which lasts about 3 to 4 years, bushes are pruned back fairly drastically and the area weeded. Hand weeding is now widely giving way to the use of chemical herbicides. The plucked tea is collected in baskets carried on the backs of the pluckers and taken down to centrally located weighing sheds, and from these to the factories for processing. In some countries, notably Japan and the former USSR, mechanical plucking has been carried out with some success, but this requires a reasonably flat terrain and bushes grown in set rows.

Figure 1. Tea pluckers at work on a plantation in Uganda


Hazards and Their Prevention

Falls and injuries caused by agricultural implements of the cutting and digging type are the most common types of accidents. This is not unexpected, considering the steep slopes on which tea is generally grown and the type of work involved in the processes of clearing, uprooting and pruning. Apart from exposure to natural hazards like lightning, workers are liable to be bitten by snakes or stung by hornets, spiders, wasps or bees, although highly venomous snakes are seldom found at the high altitudes at which the best tea grows. An allergic condition caused by contact with a certain species of caterpillar has been recorded in Assam, India.

The exposure of workers to ever-increasing quantities of highly toxic pesticides requires careful control. Substitution with less-toxic pesticides and attention to personal hygiene are necessary measures here. Mechanization has been fairly slow, but an increasing number of tractors, powered vehicles and implements are coming into use, with a concomitant increase in accidents from these causes (see figure 2). Well-designed tractors with safety cabs, operated by trained, competent drivers will eliminate many accidents.

Figure 2. Mechanical harvesting on a tea plantation near the Black Sea


In Asia, where the non-working population resident on the tea estates is almost as great as the workforce itself, the total number of accidents in the home is equal to that of accidents in the field.

Housing is generally substandard. The most common diseases are those of the respiratory system, closely followed by enteric diseases, anaemia and substandard nutrition. The former are mainly the outcome of working and living conditions at high altitudes and exposure to low temperatures and inclement weather. The intestinal diseases are due to poor sanitation and low standards of hygiene among the labour force. These are mainly preventable conditions, which underlines the need for better sanitary facilities and improved health education. Anaemia, particularly among working mothers of child-bearing age, is all too common; it is partly the result of ankylostomiasis, but is due mainly to protein-deficient diets. However, the principal causes of lost work time are generally from the more minor ailments and not serious diseases. Medical supervision of both housing and working conditions is an essential preventive measure, and official inspection, either at local or national level, is also necessary to ensure that proper health facilities are maintained.



Saturday, 12 March 2011 16:38

General Profile

Forestry—A Definition

For the purposes of the present chapter, forestry is understood to embrace all the fieldwork required to establish, regenerate, manage and protect forests and to harvest their products. The last step in the production chain covered by this chapter is the transport of raw forest products. Further processing, such as into sawnwood, furniture or paper is dealt with in the Lumber, Woodworking and Pulp and paper industries chapters in this Encyclopaedia.

The forests may be natural, human-made or tree plantations. Forest products considered in this chapter are both wood and other products, but emphasis is on the former, because of its relevance for safety and health.

Evolution of the Forest Resource and the Sector

The utilization and management of forests are as old as the human being. Initially forests were almost exclusively used for subsistence: food, fuelwood and building materials. Early management consisted mostly of burning and clearing to make room for other land uses—in particular, agriculture, but later also for settlements and infrastructure. The pressure on forests was aggravated by early industrialization. The combined effect of conversion and over-utilization was a sharp reduction in forest area in Europe, the Middle East, India, China and later in parts of North America. Presently, forests cover about one-quarter of the land surface of the earth.

The deforestation process has come to a halt in industrialized countries, and forest areas are actually increasing in these countries, albeit slowly. In most tropical and subtropical countries, however, forests are shrinking at a rate of 15 to 20 million hectares (ha), or 0.8%, per year. In spite of continuing deforestation, developing countries still account for about 60% of the world forest area, as can be seen in table 1. The countries with the largest forest areas by far are the Russian Federation, Brazil, Canada and the United States. Asia has the lowest forest cover in terms of percentage of land area under forest and hectares per capita.

Table 1.  Forest area by region (1990).


  Area (million hectares)         

 % total   




North/Central America



South America












Former USSR



Industrialized (all)



Developing (all)






Source: FAO 1995b.

Forest resources vary significantly in different parts of the world. These differences have a direct impact on the working environment, on the technology used in forestry operations and on the level of risk associated with them. Boreal forests in northern parts of Europe, Russia and Canada are mostly made up of conifers and have a relatively small number of trees per hectare. Most of these forests are natural. Moreover, the individual trees are small in size. Because of the long winters, trees grow slowly and wood increment ranges from less than 0.5 to 3 m3/ha/y.

The temperate forests of southern Canada, the United States, Central Europe, southern Russia, China and Japan are made up of a wide range of coniferous and broad-leaved tree species. Tree densities are high and individual trees can be very large, with diameters of more than 1 m and tree height of more than 50 m. Forests may be natural or human-made (i.e., intensively managed with more uniform tree sizes and fewer tree species). Standing volumes per hectare and increment are high. The latter range typically from 5 to greater than 20 m3/ha/y.

Tropical and subtropical forests are mostly broad-leaved. Tree sizes and standing volumes vary greatly, but tropical timber harvested for industrial purposes is typically in the form of large trees with big crowns. Average dimensions of harvested trees are highest in the tropics, with logs of more than 2 m3 being the rule. Standing trees with crowns routinely weigh more than 20 tonnes before felling and debranching. Dense undergrowth and tree climbers make work even more cumbersome and dangerous.

An increasingly important type of forest in terms of wood production and employment is tree plantations. Tropical plantations are thought to cover about 35 million hectares, with about 2 million hectares added per year (FAO 1995). They usually consist of only one very fast growing species. Increment mostly ranges from 15 to 30 m3/ha/y. Various pines (Pinus spp.) and eucalyptus (Eucalyptus spp.) are the most common species for industrial uses. Plantations are managed intensively and in short rotations (from 6 to 30 years), while most temperate forests take 80, sometimes up to 200 years, to mature. Trees are fairly uniform, and small to medium in size, with approximately 0.05 to 0.5 m3/tree. There is typically little undergrowth.

Prompted by wood scarcity and natural disasters like landslides, floods and avalanches, more and more forests have come under some form of management over the last 500 years. Most industrialized countries apply the “sustained yield principle”, according to which present uses of the forest may not reduce its potential to produce goods and benefits for later generations. Wood utilization levels in most industrialized countries are below the growth rates. This is not true for many tropical countries.

Economic Importance

Globally, wood is by far the most important forest product. World roundwood production is approaching 3.5 billion m3 annually. Wood production grew by 1.6% a year in the 1960s and 1970s and by 1.8% a year in the 1980s, and is projected to increase by 2.1% a year well into the 21st century, with much higher rates in developing countries than in industrialized ones.

Industrialized countries’ share of world roundwood production is 42% (i.e., roughly proportional to the share of forest area). There is, however, a major difference in the nature of the wood products harvested in industrialized and in developing countries. While in the former more than 85% consists of industrial roundwood to be used for sawnwood, panel or pulp, in the latter 80% is used for fuelwood and charcoal. This is why the list of the ten biggest producers of industrial roundwood in figure 1 includes only four developing countries. Non-wood forest products are still very significant for subsistence in many countries. They account for only 1.5% of traded unprocessed forest products, but products like cork, rattan, resins, nuts and gums are major exports in some countries.

Figure 1.  Ten biggest producers of industrial roundwood, 1993 (former USSR 1991).


Worldwide, the value of production in forestry was US$96,000 million in 1991, compared to US$322,000 million in downstream forest-based industries. Forestry alone accounted for 0.4% of world GDP. The share of forestry production in GDP tends to be much higher in developing countries, with an average of 2.2%, than in industrialized ones, where it represents only 0.14% of GDP. In a number of countries forestry is far more important than the averages suggest. In 51 countries the forestry and forest-based industries sector combined generated 5% or more of the respective GDP in 1991.

In several industrialized and developing countries, forest products are a significant export. The total value of forestry exports from developing countries increased from about US$7,000 million in 1982 to over US$19,000 million in 1993 (1996 dollars). Large exporters among industrialized countries include Canada, the United States, Russia, Sweden, Finland and New Zealand. Among tropical countries Indonesia (US$5,000 million), Malaysia (US$4,000 million), Chile and Brazil (about US$2,000 million each) are the most important.

While they cannot be readily expressed in monetary terms, the value of non-commercial goods and benefits generated by forests may well exceed their commercial output. According to estimates, some 140 to 300 million people live in or depend on forests for their livelihood. Forests are also home to three-quarters of all species of living beings. They are a significant sink of carbon dioxide and serve to stabilize climates and water regimes. They reduce erosion, landslides and avalanches, and produce clean drinking water. They are also fundamental for recreation and tourism.


Figures on wage employment in forestry are difficult to obtain and can be unreliable even for industrialized countries. The reasons are the high share of the self-employed and farmers, who do not get recorded in many cases, and the seasonality of many forestry jobs. Statistics in most developing countries simply absorb forestry into the much larger agricultural sector, with no separate figures available. The biggest problem, however, is the fact that most forestry work is not wage employment, but subsistence. The main item here is the production of fuelwood, particularly in developing countries. Bearing these limitations in mind, figure 2 below provides a very conservative estimate of global forestry employment.

Figure 2.  Employment in forestry (full-time equivalents).


World wage employment in forestry is in the order of 2.6 million, of which about 1 million is in industrialized countries. This is a fraction of the downstream employment: wood industries and pulp and paper have at least 12 million employees in the formal sector. The bulk of forestry employment is unpaid subsistence work—some 12.8 million full-time equivalents in developing and some 0.3 million in industrialized countries. Total forestry employment can thus be estimated at some 16 million person years. This is equivalent to about 3% of world agricultural employment and to about 1% of total world employment.


In most industrialized countries the size of the forestry workforce has been shrinking. This is a result of a shift from seasonal to full-time, professional forest workers, compounded by rapid mechanization, particularly of wood harvesting. Figure 3 illustrates the enormous differences in productivity in major wood-producing countries. These differences are to some extent due to natural conditions, silvicultural systems and statistical error. Even allowing for these, significant gaps persist. The transformation in the workforce is likely to continue: mechanization is spreading to more countries, and new forms of work organization, namely team work concepts, are boosting productivity, while harvesting levels remain by and large constant. It should be noted that in many countries seasonal and part-time work in forestry are unrecorded, but remain very common among farmers and small woodland owners. In a number of developing countries the industrial forestry workforce is likely to grow as a result of more intensive forest management and tree plantations. Subsistence employment, on the other hand, is likely to decline gradually, as fuelwood is slowly replaced by other forms of energy.

Figure 3Countries with highest wage employment in forestry and industrial roundwood production (late 1980s to early 1990s).


Characteristics of the Workforce

Industrial forestry work has largely remained a male domain. The proportion of women in the formal workforce rarely exceeds 10%. There are, however, jobs that tend to be predominantly carried out by women, such as planting or tending of young stands and raising seedlings in tree nurseries. In subsistence employment women are a majority in many developing countries, because they are usually responsible for fuelwood gathering.

The largest share of all industrial and subsistence forestry work is related to the harvesting of wood products. Even in human-made forests and plantations, where substantial silvicultural work is required, harvesting accounts for more than 50% of the workdays per hectare. In harvesting in developing countries the ratios of supervisor/technician to foremen and to workers are 1 to 3 and 1 to 40, respectively. The ratio is smaller in most industrialized countries.

Broadly, there are two groups of forestry jobs: those related to silviculture and those related to harvesting. Typical occupations in silviculture include tree planting, fertilization, weed and pest control, and pruning. Tree planting is very seasonal, and in some countries involves a separate group of workers exclusively dedicated to this activity. In harvesting, the most common occupations are chain-saw operation, in tropical forests often with an assistant; choker setters who attach cables to tractors or skylines pulling logs to roadside; helpers who measure, move, load or debranch logs; and machine operators for tractors, loaders, cable cranes, harvesters and logging trucks.

There are major differences between segments of the forestry workforce with respect to the form of employment, which have a direct bearing on their exposure to safety and health hazards. The share of forest workers directly employed by the forest owner or industry has been declining even in those countries where it used to be the rule. More and more work is done through contractors (i.e., relatively small, geographically mobile service firms employed for a particular job). The contractors may be owner-operators (i.e., single-person firms or family businesses) or they have a number of employees. Both the contractors and their employees often have very unstable employment. Under pressure to cut costs in a very competitive market, contractors sometimes resort to illegal practices such as moonlighting and hiring undeclared immigrants. While the move to contracting has in many cases helped to cut costs, to advance mechanization and specialization as well as to adjust the workforce to changing demands, some traditional ailments of the profession have been aggravated through the increased reliance on contract labour. These include accident rates and health complaints, both of which tend to be more frequent among contract labour.

Contract labour has also contributed to further increasing the high rate of turnover in the forestry workforce. Some countries report rates of almost 50% per year for those changing employers and more than 10% per year leaving the forestry sector altogether. This aggravates the skill problem already looming large among much of the forestry workforce. Most skill acquisition is still by experience, usually meaning trial and error. Lack of structured training, and short periods of experience due to high turnover or seasonal work, are major contributing factors to the significant safety and health problems facing the forestry sector (see the article “Skills and training” [FOR15AE] in this chapter).

The dominant wage system in forestry by far continues to be piece-rates (i.e., remuneration solely based on output). Piece-rates tend to lead to a rapid pace of work and are widely believed to increase the number of accidents. There is, however, no scientific evidence to back this contention. One undisputed side effect is that earnings fall once workers have reached a certain age because their physical abilities decline. In countries where mechanization plays a major role, time-based wages have been on the increase, because the work rhythm is largely determined by the machine. Various bonus wage systems are also in use.

Forestry wages are generally well below the industrial average in the same country. Workers, the self-employed and contractors often try to compensate by working 50 or even 60 hours per week. Such situations increase strain on the body and the risk of accidents because of fatigue.

Organized labour and trade unions are rather rare in the forestry sector. The traditional problems of organizing geographically dispersed, mobile, sometimes seasonal workers have been compounded by the fragmentation of the workforce into small contractor firms. At the same time, the number of workers in categories that are typically unionized, such as those directly employed in larger forest enterprises, is falling steadily. Labour inspectorates attempting to cover the forestry sector are faced with problems similar in nature to those of trade union organizers. As a result there is very little inspection in most countries. In the absence of institutions whose mission is to protect worker rights, forest workers often have little knowledge of their rights, including those laid down in existing safety and health regulations, and experience great difficulties in exercising such rights.

Health and Safety Problems

The popular notion in many countries is that forestry work is a 3-D job: dirty, difficult and dangerous. A host of natural, technical and organizational factors contribute to that reputation. Forestry work has to be done outdoors. Workers are thus exposed to the extremes of weather: heat, cold, snow, rain and ultraviolet (UV) radiation. Work even often proceeds in bad weather and, in mechanized operations, it increasingly continues at night. Workers are exposed to natural hazards such as broken terrain or mud, dense vegetation and a series of biological agents.

Worksites tend to be remote, with poor communication and difficulties in rescue and evacuation. Life in camps with extended periods of isolation from family and friends is still common in many countries.

The difficulties are compounded by the nature of the work—trees may fall unpredictably, dangerous tools are used and often there is a heavy physical workload. Other factors like work organization, employment patterns and training also play a significant role in increasing or reducing hazards associated with forestry work. In most countries the net result of the above influences are very high accident risks and serious health problems.

Fatalities in Forest Work

In most countries forest work is one of the most dangerous occupations, with great human and financial losses. In the United States accident insurance costs amount to 40% of payroll.

A cautious interpretation of the available evidence suggests that accident trends are more often upward than downward. Encouragingly, there are countries that have a long-standing record in bringing down accident frequencies (e.g., Sweden and Finland). Switzerland represents the more common situation of increasing, or at best stagnating, accident rates. The scarce data available for developing countries indicate little improvement and usually excessively high accident levels. A study of safety in pulpwood logging in plantation forests in Nigeria, for example, found that on average a worker had 2 accidents per year. Between 1 in 4 and 1 in 10 workers suffered a serious accident in a given year (Udo 1987).

A closer inspection of accidents reveals that harvesting is far more hazardous than other forest operations (ILO 1991). Within forest harvesting, tree felling and cross-cutting are the jobs with the most accidents, particularly serious or fatal ones. In some countries, such as in the Mediterranean area, firefighting can also be a major cause of fatalities, claiming up to 13 lives a year in Spain in some years (Rodero 1987). Road transport can also account for a large share of serious accidents, particularly in tropical countries.

The chain-saw is clearly the single most dangerous tool in forestry, and the chain-saw operator the most exposed worker. The situation depicted in figure 4 for a territory of Malaysia is found with minor variations in most other countries as well. In spite of increasing mechanization, the chain-saw is likely to remain the key problem in industrialized countries. In developing countries, its use can be expected to expand as plantations account for an increasing share of the wood harvest.

Figure 4.  Distribution of logging fatalities among jobs, Malaysia (Sarawak), 1989.


Virtually all parts of the body can be injured in forest work, but there tends to be a concentration of injuries to the legs, feet, back and hands, in roughly that order. Cuts and open wounds are the most common type of injury in chain-saw work while bruises dominate in skidding, but there are also fractures and dislocations.

Two situations under which the already high risk of serious accidents in forest harvesting multiplies severalfold are “hung-up” trees and wind-blown timber. Windblow tends to produce timber under tension, which requires specially adapted cutting techniques (for guidance see FAO/ECE/ILO 1996a; FAO/ILO 1980; and ILO 1998). Hung-up trees are those that have been severed from the stump but did not fall to the ground because the crown became entangled with other trees. Hung-up trees are extremely dangerous and referred to as “widow-makers” in some countries, because of the high number of fatalities they cause. Aid tools, such as turning hooks and winches, are required to bring such trees down safely. In no case should it be permitted that other trees be felled onto a hung-up one in the hope of bringing it down. This practice, known as “driving” in some countries, is extremely hazardous.

Accident risks vary not only with technology and exposure due to the job, but with other factors as well. In almost all cases for which data are available, there is a very significant difference between segments of the workforce. Full-time, professional forest workers directly employed by a forest enterprise are far less affected than farmers, self-employed or contract labour. In Austria, farmers seasonally engaged in logging suffer twice as many accidents per million cubic metres harvested as professional workers (Sozialversicherung der Bauern 1990), in Sweden, even four times as many. In Switzerland, workers employed in public forests have only half as many accidents as those employed by contractors, particularly where workers are hired only seasonally and in the case of migrant labour (Wettmann 1992).

The increasing mechanization of tree harvesting has had very positive consequences for work safety. Machine operators are well protected in guarded cabins, and accident risks have dropped very significantly. Machine operators experience less than 15% of the accidents of chain-saw operators to harvest the same amount of timber. In Sweden operators have one-quarter of the accidents of professional chain-saw operators.

Growing Occupational Disease Problems

The reverse side of the mechanization coin is an emerging problem of neck and shoulder strain injuries among machine operators. These can be as incapacitating as serious accidents.

The above problems add to the traditional health complaints of chain-saw operators—namely, back injuries and hearing loss. Back pain due to physically heavy work and unfavourable working postures is very common among chain-saw operators and workers doing manual loading of logs. There is a high incidence of premature loss of working capacity and of early retirement among forest workers as a result. A traditional ailment of chain-saw operators that has largely been overcome in recent years through improved saw design is vibration-induced “white finger” disease.

The physical, chemical and biological hazards causing health problems in forestry are discussed in the following articles of this chapter.

Special Risks for Women

Safety risks are by and large the same for men and women in forestry. Women are often involved in planting and tending work, including the application of pesticides. However, women who have smaller body size, lung volume, heart and muscles may have a work capacity on average that is about one-third lower than that of men. Correspondingly, legislation in many countries limits the weight to be lifted and carried by women to about 20 kg (ILO 1988), although such sex-based differences in exposure limits are illegal in many countries. These limits are often exceeded by women working in forestry. Studies in British Columbia, where separate standards do not apply, among planting workers showed full loads of plants carried by men and women to average 30.5 kg, often in steep terrain with heavy ground cover (Smith 1987).

Excessive loads are also common in many developing countries where women work as fuelwood carriers. A survey in Addis Ababa, Ethiopia, for example, found that an estimated 10,000 women and children eke out a livelihood from hauling fuelwood into town on their backs (see figure 5 ). The average bundle weighs 30 kg and is carried over a distance of 10 km. The work is highly debilitating and results in numerous serious health complaints, including frequent miscarriages (Haile 1991).

Figure 5.  Woman fuelwood carrier, Addis Ababa, Ethiopia.


The relationship between the specific working conditions in forestry, workforce characteristics, form of employment, training and other similar factors and safety and health in the sector has been a recurrent theme of this introductory article. In forestry, even more than in other sectors, safety and health cannot be analysed, let alone promoted, in isolation. This theme will also be the leitmotiv for the remainder of the chapter.




Thursday, 10 March 2011 16:05


Hops are used in brewing and are commonly grown in the Pacific Northwest of the United States, Europe (especially Germany and the United Kingdom), Australia and New Zealand.

Hops grow from rhizome cuttings of female hop plants. Hop vines grow up to 4.5 to 7.5 m or more during the growing season. These vines are trained to climb up heavy trellis wire or heavy cords. Hops are traditionally spaced 2 m apart in each direction with two cords per plant going to the overhead trellis wire at about 45° angles. Trellises are about 5.5 m high and are made from 10 ´ 10 cm pressure-treated timbers or poles sunk 0.6 to 1 m into the ground.

Manual labour is used to train the vines after the vines reach about a third of a metre in length; additionally, the lowest metre is pruned to allow air circulation to reduce disease development.

Hops vines are harvested in the fall. In the United Kingdom, some hops are grown in trellises 3 m high and harvested with an over-the-row mechanical harvester. In the United States, hop combines are available to harvest 5.5-m-high trellises. The areas that the harvesters (field strippers) are unable to get are harvested by hand with a machete. Newly harvested hops are then kiln dried from 80% moisture to about 10%. Hops are cooled, then baled and taken to cold storage for end use.

Safety Concerns

Workers need to wear long sleeves and gloves when working near the vines, because hooked hairs of the plant may cause a rash on the skin. Some individuals become more sensitized to the vines than others.

A majority of the injuries involve strains and sprains due to lifting materials such as irrigation pipes and bales, and over-reaching when working on trellises. Workers should be trained in lifting or mechanical aids should be used.

Workers need to wear chaps at the knee and below to protect the leg from cuts while cutting the vines by hand. Eye protection is a must while working with the vines.

Many injuries occur while workers tie twine to the wire trellis wire. Most work is performed while standing on high trailers or platforms on tractors. Accidents have been reduced by providing safety belts or guard rails to prevent falls, and by wearing eye protection. Because there is much movement with the hands, carpal tunnel syndrome may be a problem.

Since hops are often treated with fungicides during the season, proper posting of re-entry intervals is needed.

Worker’s compensation claims in Washington State (US) tend to indicate that injury incidence ranges between 30 and 40 injuries per 100 person years worked. Growers through their association have safety committees that actively work to lower injury rates. Injury rates in Washington are similar to those found in the tree fruit industry and dairy. Highest injury incidence tends to occur in August and September.

The industry has unique practices in the production of the product, where much of the machinery and equipment is locally manufactured. By the vigilance of the safety committees to provide adequate machine guarding, they are able to reduce “caught in” type injuries within the harvesting and processing operations. Training should focus on proper use of knives, PPE and prevention of falls from vehicles and other machines.



Saturday, 12 March 2011 16:50

Wood Harvesting

The present article draws heavily on two publications: FAO 1996 and FAO/ILO 1980. This article is an overview; numerous other references are available. For specific guidance on preventive measures, see ILO 1998.

Wood harvesting is the preparation of logs in a forest or tree plantation according to the requirements of a user, and delivery of logs to a consumer. It includes the cutting of trees, their conversion into logs, extraction and long distance transport to a consumer or processing plant. The terms forest harvesting, wood harvesting or logging are often used synonymously. Long-distance transport and the harvesting of non-wood forest products are dealt with in separate articles in this chapter.


While many different methods are used for wood harvesting, they all involve a similar sequence of operations:

  • tree felling: severing a tree from the stump and bringing it down
  • topping and debranching (delimbing): cutting off the unusable tree crown and the branches
  • debarking: removing the bark from the stem; this operation is often done at the processing plant rather than in the forest; in fuelwood harvesting it is not done at all
  • extraction: moving the stems or logs from the stump to a place close to a forest road where they can be sorted, piled and often stored temporarily, awaiting long distance transport
  • log making/cross-cutting (bucking): cutting the stem to the length specified by the intended use of the log
  • scaling: determining the quantity of logs produced, usually by measuring volume (for small dimension timber also by weight; the latter is common for pulpwood; weighing is done at the processing plant in that case)
  • sorting, piling and temporary storage: logs are usually of variable dimensions and quality, and are therefore classified into assortments according to their potential use as pulpwood, sawlogs and so on, and piled until a full load, usually a truckload, has been assembled; the cleared area where these operations, as well as scaling and loading, take place is called a “landing”
  • loading: moving the logs onto the transport medium, typically a truck, and attaching the load.


These operations are not necessarily carried out in the above sequence. Depending on the forest type, the kind of product desired and the technology available, it may be more advantageous to carry out an operation either earlier (i.e., closer to the stump) or later (i.e., at the landing or even at the processing plant). One common classification of harvesting methods is based on distinguishing between:

  • full-tree systems, where trees are extracted to the roadside, the landing or the processing plant with the full crown
  • short-wood systems, where topping, debranching and cross-cutting is done close to the stump (logs are usually not longer than 4 to 6 m)
  • tree-length systems, where tops and branches are removed before extraction.


The most important group of harvesting methods for industrial wood is based on tree length. Short-wood systems are standard in northern Europe and also common for small-dimension timber and fuelwood in many other parts of the world. Their share is likely to increase. Full-tree systems are the least common in industrial wood harvesting, and are used in only a limited number of countries (e.g., Canada, the Russian Federation and the United States). There they account for less than 10% of volume. The importance of this method is diminishing.

For work organization, safety analysis and inspection, it is useful to conceive of three distinct work areas in a wood harvesting operation:

  1. the felling site or stump
  2. the forest terrain between the stump and the forest road
  3. the landing.


It is also worthwhile to examine whether the operations take place largely independently in space and time or whether they are closely related and interdependent. The latter is often the case in harvesting systems where all steps are synchronized. Any disturbance thus disrupts the entire chain, from felling to transport. These so-called hot-logging systems can create extra pressure and strain if not carefully balanced.

The stage in the life cycle of a forest during which wood harvesting takes place, and the harvesting pattern, will affect both the technical process and its associated hazards. Wood harvesting occurs either as thinning or as final cut. Thinning is the removal of some, usually undesirable, trees from a young stand to improve the growth and quality of the remaining trees. It is usually selective (i.e., individual trees are removed without creating major gaps). The spatial pattern generated is similar to that in selective final cutting. In the latter case, however, the trees are mature and often large. Even so, only some of the trees are removed and a significant tree cover remains. In both cases orientation on the worksite is difficult because remaining trees and vegetation block the view. It can be very difficult to bring trees down because their crowns tend to be intercepted by the crowns of remaining trees. There is a high risk of falling debris from the crowns. Both situations are difficult to mechanize. Thinning and selective cutting therefore require more planning and skill to be done safely.

The alternative to selective felling for final harvest is the removal of all trees from a site, called “clear cutting”. Clearcuts can be small, say 1 to 5 hectares, or very large, covering several square kilometres. Large clearcuts are severely criticized on environmental and scenic grounds in many countries. Whatever the pattern of the cut, harvesting old growth and natural forest usually involves greater risk than harvesting younger stands or human-made forests because trees are large and have tremendous inertia when falling. Their branches may be intertwined with the crowns of other trees and climbers, causing them to break off branches of other trees as they fall. Many trees are dead or have internal rot which may not be apparent until late in the felling process. Their behaviour during felling is often unpredictable. Rotten trees may break off and fall in unexpected directions. Unlike green trees, dead and dry trees, called snags in North America, fall quickly.

Technological developments

Technological development in wood harvesting has been very rapid over the second half of the 20th century. Average productivity has been soaring in the process. Today, many different harvesting methods are in use, sometimes side by side in the same country. An overview of systems in use in Germany in the mid-1980s, for example, describes almost 40 different configurations of equipment and methods (Dummel and Branz 1986).

While some harvesting methods are technologically far more complex than others, no single method is inherently superior. The choice will usually depend on the customer specifications for the logs, on forest conditions and terrain, on environmental considerations, and often decisively on cost. Some methods are also technically limited to small and medium-size trees and relatively gentle terrain, with slopes not exceeding 15 to 20°.

Cost and performance of a harvesting system can vary over a wide range, depending on how well the system fits the conditions of the site and, equally important, on the skill of the workers and how well the operation is organized. Hand tools and manual extraction, for example, make perfect economic and social sense in countries with high unemployment, low labour and high capital cost, or in small-scale operations. Fully mechanized methods can achieve very high daily outputs but involve large capital investments. Modern harvesters under favourable conditions can produce upwards of 200 m3 of logs per 8-hour day. A chain-saw operator is unlikely to produce more than 10% of that. A harvester or big cable yarder costs around US$500,000 compared to US$1,000 to US$2,000 for a chain-saw and US$200 for a good quality cross-cut handsaw.

Common Methods, Equipment and Hazards

Felling and preparation for extraction

This stage includes felling and removal of crown and branches; it may include debarking, cross-cutting and scaling. It is one of the most hazardous industrial occupations. Hand tools and chain-saws or machines are used in felling and debranching trees and crosscutting trees into logs. Hand tools include cutting tools such as axes, splitting hammers, bush hooks and bush knives, and hand saws such as cross-cut saws and bow saws. Chain-saws are widely used in most countries. In spite of major efforts and progress by regulators and manufacturers to improve chain-saws, they remain the single most dangerous type of machine in forestry. Most serious accidents and many health problems are associated with their use.

The first activity to be carried out is felling, or severing the tree from the stump as close to the ground as conditions permit. The lower part of the stem is typically the most valuable part, as it contains a high volume, and has no knots and an even wood texture. It should therefore not split, and no fibre should be torn out from the butt. Controlling the direction of the fall is important, not only to protect the tree and those to be left standing, but also to protect the workers and to make extraction easier. In manual felling, this control is achieved by a special sequence and configuration of cuts.

The standard method for chain-saws is depicted in figure 1. After determining the felling direction (1) and clearing the tree’s base and escape routes, sawing starts with the undercut (2), which should penetrate approximately one-fifth to one-quarter of the diameter into the tree. The opening of the undercut should be at an angle of about 45°. The oblique cut (3) is made prior to the horizontal cut (4), which must meet the oblique cut in a straight line facing the felling direction at a 90o angle. If stumps are liable to tear splinters from the tree, as is common with softer woods, the undercut should be terminated with small lateral cuts (5) on both sides of the hinge (6). The back cut (7) must also be horizontal . It should be made 2.5 to 5 cm higher than the base of the undercut. If the tree’s diameter is smaller than the guide bar, the back cut can be made in a single movement (8). Otherwise, the saw must be moved several times (9). The standard method is used for trees with more than 15 cm butt diameter. The standard technique is modified if trees have one-side crowns, are leaning in one direction or have a diameter more than twice the length of the chain-saw blade. Detailed instructions are included in FAO/ILO (1980) and many other training manuals for chain-saw operators.

Figure 1.  Chain-saw felling: Sequence of cuts.


Using standard methods, skilled workers can fell a tree with a high degree of precision. Trees that have symmetrical crowns or those leaning a little in a direction other than the intended direction of fall may not fall at all or may fall at an angle from the intended direction. In these cases, tools such as felling levers for small trees or hammers and wedges for big trees need to be used to shift the tree’s natural centre of gravity in the desired direction.

Except for very small trees, axes are not suitable for felling and cross-cutting. With handsaws the process is relatively slow and errors can be detected and repaired. With chain-saws cuts are fast and the noise blocks out the signals from the tree, such as the sound of breaking fibre before it falls. If the tree does start to fall but is intercepted by other trees, a “hang-up” results, which is extremely dangerous, and must be dealt with immediately and professionally. Turning hooks and levers for smaller trees and manual or tractor-mounted winches for larger trees are used to bring hung-up trees down effectively and safely.

Hazards involved with felling include falling or rolling trees; falling or snapping branches; cutting tools; and noise, vibration and exhaust gases with chain-saws. Windfall is especially hazardous with wood and partially severed root systems under tension; hung-up trees are a frequent cause of severe and fatal accidents. All workers involved in felling should have received specific training. Tools for felling and for dealing with hung-up trees need to be onsite. Hazards associated with cross-cutting include the cutting tools as well as snapping wood and rolling stems or bolts, particularly on slopes.

Once a tree has been brought down, it is usually topped and debranched. In the majority of cases, this is still done with hand tools or chain-saws at the stump. Axes can be very effective for debranching. Where possible, trees are felled across a stem already on the ground. This stem thus serves as a natural workbench, raising the tree to be debranched to a more convenient height and allowing for complete debranching without having to turn the tree. The branches and the crown are cut from the stem and left on the site. The crowns of large, broad-leaved trees may have to be cut into smaller pieces or pulled aside because they would otherwise obstruct extraction to the roadside or landing.

Hazards involved with debranching include cuts with tools or chain-saws; high risk of chain-saw kick-back (see figure 2); snapping branches under tension; rolling logs; trips and falls; awkward work postures; and static work load if poor technique is used.

Figure 2. Chain-saw Kick-back.


In mechanized operations, the directional fall is achieved by holding the tree with a boom mounted on a sufficiently heavy base machine, and cutting the stem with a shear, circular saw or chain-saw integrated into the boom. To do this, the machine has to be driven rather close to the tree to be felled. The tree is then lowered into the desired direction by movements of the boom or of the base of the machine. The most common types of machines are feller-bunchers and harvesters.

Feller-bunchers are mostly mounted on machines with tracks, but they can also be equipped with tyres. The felling boom usually allows them to fell and collect a number of small trees (a bunch), which is then deposited along a skid trail. Some have a clam bunk to collect a load. When feller-bunchers are used, topping and debranching are usually done by machines at the landing.


With good machine design and careful operation, accident risk with feller-bunchers is relatively low, except when chain-saw operators work along with the machine. Health hazards, such as vibration, noise, dust and fumes, are significant, since base machines often are not built for forestry purposes. Feller-bunchers should not be used on excessive slopes, and the boom should not be overloaded, as felling direction becomes uncontrollable.

Harvesters are machines which integrate all felling operations except debarking. They usually have six to eight wheels, hydraulic traction and suspension, and articulated steering. They have booms with a reach of 6 to 10 m when loaded. A distinction is made between one-grip and two-grip harvesters. One-grip harvesters have one boom with a felling head fitted with devices for felling, debranching, topping and cross-cutting. They are used for small trees up to 40 cm butt diameter, mostly in thinnings but increasingly also in final cutting. A two-grip harvester has separate felling and processing heads. The latter is mounted on the base machine rather than on the boom. It can handle trees up to a stump diameter of 60 cm. Modern harvesters have an integrated, computer-assisted measuring device that can be programmed to make decisions about optimum cross-cutting depending on the assortments needed.

Harvesters are the dominant technology in large-scale harvesting in northern Europe, but presently account for a rather small share of harvesting worldwide. Their importance is, however, likely to rise fast as second growth, human-made forests and plantations become more important as sources of raw material.

Accident rates in harvester operation are typically low, though accident risk rises when chain-saw operators work along with harvesters. Maintenance of harvesters is hazardous; repairs are always under high work pressure, increasingly at night; there is high risk of slipping and falling, uncomfortable and awkward working postures, heavy lifting, contact with hydraulic oils and hot oils under pressure. The biggest hazards are static muscle tension and repetitive strain from operating controls and psychological stress.


Extraction involves moving the stems or logs from the stump to a landing or roadside where they can be processed or piled into assortments. Extraction can be very heavy and hazardous work. It can also inflict substantial environmental damage to the forest and its regeneration, to soils and to watercourses. The major types of extraction systems commonly recognized are:

  • ground-skidding systems: The stems or logs are dragged on the ground by machines, draught animals or humans.
  • forwarders: The stems or logs are carried on a machine (in the case of fuelwood, also by humans).
  • cable systems: The logs are conveyed from the stump to the landing by one or more suspended cables.
  • aerial systems: Helicopters or balloons are used to airlift the logs.


Ground skidding, by far the most important extraction system both for industrial wood and fuelwood, is usually done with wheeled skidders specially designed for forestry operations. Crawler tractors and, especially, farm tractors can be cost effective in small private forests or for the extraction of small trees from tree plantations, but adaptations are needed to protect both the operators and the machines. Tractors are less robust, less well balanced and less protected than purpose-built machines. As with all machines used in forestry, hazards include over-turning, falling objects, penetrating objects, fire, whole-body vibration and noise. All-wheel drive is preferable, and a minimum of 20% of the machine weight should be maintained as load on the steered axle during operation, which may require attaching additional weight to the front of the machine. The engine and transmission may need extra mechanical protection. Minimum engine power should be 35 kW for small-dimension timber; 50 kW is usually adequate for normal-size logs.

Grapple skidders drive directly to the individual or the pre-bunched stems, lift the front end of the load and drag it to the landing. Skidders with cable winches can operate from skid roads. Their loads are usually assembled through chokers, straps, chains or short cables that are attached to individual logs. A choker setter prepares the logs to be hooked up and, when the skidder returns from the landing, a number of chokers is attached to the main line and winched into the skidder. Most skidders have an arch onto which the front end of the load can be lifted to reduce friction during skidding. When skidders with powered winches are used, good communication between crew members through two-way radios or optical or acoustic signals is essential. Clear signals need to be agreed upon; any signal that is not understood means “Stop!”. Figure 3  shows proposed hand signals for skidders with powered winches.

Figure 3.  International conventions for hand signals to be used for skidders with powered winches.


As a rule of thumb, ground skidding equipment should not be used on slopes of more than 15°. Crawler tractors may be used to extract large trees from relatively steep terrain, but they can cause substantial damage to soils if used carelessly. For environmental and safety reasons, all skidding operations should be suspended during exceptionally wet weather.

Extraction with draught animals is an economically viable option for small logs, particularly in thinning operations. Skidding distances must be short (typically 200 m or less) and slopes gentle. It is important to use appropriate harnesses providing maximum pulling power, and devices like skidding pans, sulkies or sledges that reduce skidding resistance.

Manual skidding is increasingly rare in industrial logging but continues to be practised in subsistence logging, particularly for fuelwood. It is limited to short distances and usually downhill, making use of gravity to move logs. While logs are typically small, this is very heavy work and can be hazardous on steep slopes. Efficiency and safety can be increased by using hooks, levers and other hand tools for lifting and pulling logs. Chutes, traditionally made from timber but also available as polyethylene half-tubes, can be an alternative to manual ground skidding of short logs in steep terrain.

Forwarders are extraction machines that carry a load of logs completely off the ground, either within their own frame or on a trailer. They usually have a mechanical or hydraulic crane for self-loading and unloading of logs. They tend to be used in combination with mechanized felling and processing equipment. The economic extraction distance is 2 to 4 times that of ground-skidders. Forwarders work best when logs are approximately uniform in size.

Accidents involving forwarders are typically similar to those of tractors and other forestry machines: overturning, penetrating and falling objects, electric power lines and maintenance problems. Health hazards include vibration, noise and hydraulic oils.

Using human beings to carry loads is still done for short logs like pulpwood or pit props in some industrial harvesting, and is the rule in fuelwood harvesting. Loads carried often exceed all recommended limits, particularly for women, who are often responsible for fuelwood gathering. Training in proper techniques that would avoid extreme strain on the spine and using devices like back packs that give a better weight distribution would ease their burden.

Cable extraction systems are fundamentally different from other extraction systems in that the machine itself does not travel. Logs are conveyed with a carriage moving along suspended cables. The cables are operated by a winching machine, also referred to as a yarder or hauler. The machine is installed either at the landing or at the opposite end of the cableway, often on a ridgetop. The cables are suspended above the ground on one or more “spar” trees, which may either be trees or steel towers. Many different types of cable systems are in use. Skylines or cable cranes have a carriage that can be moved along the mainline, and the cable can be released to allow lateral pulling of logs to the line, before they are lifted and forwarded to the landing. If the system permits full suspension of the load during hauling, soil disturbance is minimal. Because the machine is fixed, cable systems can be used in steep terrain and on wet soils. Cable systems in general are substantially more expensive than ground skidding and require careful planning and skilled operators.

Hazards occur during installation, operation and dismantling of the cable system, and include mechanical impact by deformation of the cabin or stand; breaking of cables, anchors, spars or supports; inadvertent or uncontrollable movements of cables, carriages, chokers and loads; and squeezes, abrasions and so on from moving parts. Health hazards include noise, vibration and awkward working postures.

Aerial extraction systems are those which fully suspend logs in the air throughout the extraction process. The two types currently in use are balloon systems and helicopters, but only helicopters are widely used. Helicopters with a lifting capacity of about 11 tonnes are commercially available. The loads are suspended under the helicopter on a tether line (also called “tagline”). The tether lines are typically between 30 and 100 m long, depending both upon topography and the height of trees above which the helicopter must hover. The loads are attached with long chokers and are flown to the landing, where the chokers are released by remote control from the aircraft. When large logs are being extracted, an electrically operated grapple system may be used instead of chokers. Round-trip times are typically two to five minutes. Helicopters have a very high direct cost, but can also achieve high production rates and reduce or eliminate the need for expensive road construction. They also cause low environmental impact. In practice their use is limited to high-value timber in otherwise inaccessible regions or other special circumstances.

Because of the high production rates required to make the use of such equipment economical, the number of workers employed on helicopter operations is much larger than for other systems. This is true for landings, but also for workers in cutting operations. Helicopter logging can create major safety problems, including fatalities, if precautions are disregarded and crews ill prepared.

Log making and loading

Log making, if it takes place at the landing, is mostly done by chain-saw operators. It can also be carried out by a processor (i.e., a machine that delimbs, tops and cuts to length). Scaling is mostly done manually using measuring tape. For sorting and piling, logs are usually handled by machines like skidders, which use their front blade to push and lift logs, or by grapple loaders. Helpers with hand tools like levers often assist the machine operators. In fuelwood harvesting or where small logs are involved, loading onto trucks is usually done manually or by using a small winch. Loading large logs manually is very arduous and dangerous; these are usually handled by grapple or knuckle boom loaders. In some countries the logging trucks are equipped for self-loading. The logs are secured on the truck by lateral supports and cables that can be pulled tight.

In manual loading of timber, physical strain and workloads are extremely high. In both manual and mechanized loading, there is danger of getting hit by moving logs or equipment. Mechanized loading hazards include noise, dust, vibration, high mental workload, repetitive strain, overturning, penetrating or falling objects and hydraulic oils.

Standards and Regulations

At present most international safety standards applicable to forestry machinery are general—for example, roll-over protection. However, work is under way on specialized standards at the International Organization for Standardization (ISO). (See the article “Rules, legislation, regulations and codes of forest practice” in this chapter.)

Chain-saws are one of the few pieces of forestry equipment for which specific international regulations on safety features exist. Various ISO norms are relevant. They were incorporated and supplemented in 1994 in European Norm 608, Agricultural and forest machinery: Portable chain-saws—Safety. This standard contains detailed indications on design features. It also stipulates that manufacturers are required to provide comprehensive instructions and information on all aspects of operator/user maintenance and the safe use of the saw. This is to include safety clothing and personal protective equipment requirements as well as the need for training. All saws sold within the European Union have to be marked “Warning, see instruction handbook”. The standard lists the items to be included in the handbook.

Forestry machines are less well covered by international standards, and there is often no specific national regulation about required safety features. Forestry machines may also have significant ergonomic deficiencies. These play a major role in the development of serious health complaints among operators. In other cases, machines have a good design for a particular worker population, but are less suitable when imported into countries where workers have different body sizes, communication routines and so on. In the worst case machines are stripped of essential safety and health features to reduce prices for exports.

In order to guide testing organizations and those responsible for machine acquisition, specialized ergonomic checklists have been developed in various countries. Checklists usually address the following machine characteristics:

  • access and exit areas like steps, ladders and doors
  • cabin space and position of controls
  • seat, arms, back and footrest of operator’s chair
  • visibility when performing main operations
  • “worker-machine interface”: type and arrangement of indicators and controls of machine functions
  • physical environment, including vibration noise, gases and climatic factors
  • safety, including roll-over, penetrating objects, fire and so on
  • maintenance.


Specific examples of such checklists can be found in Golsse (1994) and Apud and Valdés (1995). Recommendations for machines and equipment as well as a list of existing ILO standards are included in ILO 1998.



Saturday, 12 March 2011 17:00

Timber Transport

Timber transport provides the link between the forest harvesting and the mill. This operation is of great economic importance: in the northern hemisphere it accounts for 40 to 60% of the total wood procurement cost at the mill (excluding stumpage), and in the tropics the proportion is even higher. The basic factors affecting timber transport include: the size of the operation; the geographic locations of the forest and the mill as well as the distance between them; the assortment of timber for which the mill is designed; and the kinds of transportation that are available and suitable. The main timber assortments are full trees with branches, delimbed tree lengths, long logs (typically 10 to 16m in length), shortwood (typically 2 to 6m logs), chips and hog fuel. Many mills can accept varied assortments of timber; some can accept only specific types—for example, shortwood by road. Transport can be by road, rail, ship, floating down a waterway or, depending on the geography and the distance, various combinations of these. Road transport by truck, however, has become the primary form of timber transportation.

In many cases timber transport, especially road transport, is an integrated part of the harvesting operation. Thus, any problem in timber transport may stop the entire harvesting operation. The time pressure can lead to a demand for overtime work and a tendency to cut corners that may compromise the workers’ safety.

Both forest harvesting and timber transport are often contracted out. Particularly when there are multiple contractors and subcontractors, there may be a question of who has the responsibility for protecting particular workers’ safety and health.

Timber Handling and Loading

When circumstances permit, timber may be loaded directly onto trucks at the stump, eliminating the need for a separate forest transport phase. When distances are short, forest transport equipment (e.g., an agricultural tractor with a trailer or semi-trailer) may convey the timber directly to the mill. Normally, however, the timber is first taken to the forest roadside landing for long-distance transport.

Manual loading is often practised in developing countries and in poorly capitalized operations. Small logs can be lifted and the large ones rolled with the help of ramps (see figure 1). Simple hand tools like hooks, levers, sappies, pulleys and so on may be used, and draught animals may be involved.

Figure 1.  Manual loading (with and without ramps).


In most instances, however, loading is mechanized, usually with swing-boom, knuckle-boom or front-end loaders. Swing-boom and knuckle-boom loaders may be mounted on wheeled or tracked carriers or on trucks, and are usually equipped with grapples. Front-end loaders usually have forks or grapples and are mounted on crawler tractors or articulated four-wheel-drive tractors. In semi-mechanized loading, logs may be lifted or rolled up the loading skids by cables and different kinds of tractors and winches (see figure 2) . Semi-mechanized loading often requires workers to be on the ground attaching and releasing cables, guiding the load and so on, often using hooks, levers and other hand tools. In chipping operations, the chipper usually blows the chips directly into the truck, trailer or semi-trailer.

Figure 2.  Mechanized and semi-mechanized loading.


Landing Operations

Landings are busy, noisy places where many different operations are conducted simultaneously. Depending on the harvesting system, these include loading and unloading, delimbing, debarking, bucking, sorting, storing and chipping. One or more large machines may be moving and operating at the same time while chain saws are in use close by. During and after rain, snow and frost, the logs may be very slippery and the ground may be very muddy and slick. The area may be littered with debris, and in dry weather it may be very dusty. Logs may be stored in unsecured piles several metres high. All this makes the landing one of the most dangerous working areas in the forestry industry.

Road Transport

Road transport of timber is carried by vehicles the size of which depends on the dimensions of the timber, road conditions and traffic regulations, and the availability of capital to purchase or lease the equipment. Two- or three-axle trucks with a carrying capacity of 5 to 6 tonnes are commonly used in tropical countries. In Scandinavia, for example, the typical logging truck is a 4-axle truck with a 3-axle trailer or vice versa—with a carrying capacity of 20 to 22 tonnes. On private roads in North America, one can encounter rigs with a total weight of 100 to 130 tonnes or more.

Water Transport

The use of waterways for timber transport has been declining as road transport has been increasing, but it still remains important in Canada, the United States, Finland and Russia in the northern hemisphere, in the watersheds of the Amazon, Paraguay and Parana rivers in Latin America, in many rivers and lakes in Western Africa and in most countries in Southeast Asia.

In mangrove and tidal forests, water transport usually starts directly from the stump; otherwise the logs have to be transported to the waterfront, usually by truck. Loose logs or bundles can be drifted downstream in rivers. They can be bound into rafts which can be towed or pushed in rivers, lakes and along coasts, or they may be loaded onto boats and barges of varying size. Ocean-going ships play a large role in the international timber trade.

Rail Transport

In North America and in the tropics, railway transport, like water transport, is giving way to road transport. However, it remains very important in countries like Canada, Finland, Russia and China, where there are good railway networks with suitable intermediate landing areas. In some large-scale operations, temporary narrow-gauge railways may be used. The timber may be carried in standard freight cars, or specially constructed timber-carrying cars may be used. In some terminals, large fixed cranes may be used for loading and unloading, but, as a rule, the loading methods described above are used.


Loading and unloading, which sometimes must be done several times as timber travels from the forest to where it will be used, is often a particularly hazardous operation in the timber industry. Even when fully mechanized, workers on foot and using hand tools may be involved and may be at risk. Some larger operators and contractors recognize this, maintain their equipment properly and provide their workers with personal protective equipment (PPE) such as shoes, gloves, helmets, glasses and noise protectors. Even then, trained and diligent supervisors are required, to ensure that safety concerns are not overlooked. Safety often becomes problematic in smaller operations and particularly in developing countries. (For an example see figure 3 , which shows workers without PPE loading logs in Nigeria.)

Figure 3.  Logging operations in Nigeria with unprotected workers.




Saturday, 12 March 2011 17:08

Harvesting of Non-Wood Forest Products

Operational Environment

There are many hazards associated with the harvest of non-wood forest products because of the wide variety of non-wood products themselves. In order better to define these hazards, non-wood products may be grouped by category, with a few representative examples. Then the hazards associated with their harvest can be more easily identified (see table 1).

Table 1.  Non-wood forest product categories and examples.



Food products

Animal products, bamboo shoots, berries, beverages, forage, fruits, herbs, mushrooms, nuts, oils, palm hearts, roots, seeds, starches

Chemical and pharmacological products and derivatives

Aromatics, gums and resins, latex and other exudates, medicinal extracts, tans and dyes, toxins

Decorative materials

Bark, foliage, flowers, grasses, potpourri

Non-wood fibre for plaiting, structural purposes, and padding

Bamboo, bark, cork, kapok, palm leaves, rattan, reeds, thatching grasses


Non-wood products are harvested for several reasons (subsistence, commercial or hobby/recreational purposes) and for a range of needs. This in turn affects the relative hazard associated with their collection. For example, the hobbyist mushroom picker is much less likely to remain in the open risking exposure to severe climatic conditions than is the commercial picker, dependent on picking for income and competing for a limited supply of seasonally available mushrooms.

The scale of non-wood harvesting operations is variable, with associated positive and negative effects on potential hazards. By its nature non-wood harvesting is often a small, subsistence or entrepreneurial effort. The safety of the lone worker in remote locations can be more problematic than for the non-isolated worker. Individual experience will affect the situation. There may be an emergency or other situation possibly calling for the direct intervention of outside consultative sources of safety and health information. Certain specific non-wood products have, however, been significantly commercialized, even lending themselves to plantation cultivation, such as bamboo, mushrooms, gum naval stores, certain nuts and rubber, to name just a few. Commercialized operations, theoretically, may be more likely to provide and emphasize systematic health and safety information in the course of work.

Collectively, the listed products, the forest environment in which they exist and the methods required to harvest them can be linked with certain inherent health and safety hazards. These hazards are quite elementary because they derive from very common actions, such as climbing, cutting with hand tools, digging, gathering, picking and manual transport. In addition, harvest of a certain food product might include exposure to biological agents (a poisonous plant surface or poisonous snake), biomechanical hazards (e.g., due to a repetitive movement or carrying a heavy load), climatological conditions, safety hazards from tools and techniques (such as a laceration due to careless cutting technique) and other hazards (perhaps due to difficult terrain, river crossings or working off the ground).

Because non-wood products often do not lend themselves to mechanization, and because its cost is frequently prohibitive, there is a disproportionate emphasis on manual harvest or using draught animals for harvest and transport compared to other industries.

Hazard Control and Prevention

A special word about cutting operations is warranted, since cutting is arguably the most recognizable and common source of hazard associated with the harvest of non-wood forest products. Potential cutting hazards are linked to appropriate tool selection and tool quality, size/type of the cut required, the force needed to make the cut, positioning of the worker and worker attitude.

In general, cutting hazards can be reduced or mitigated by:

  • direct training for the work tasks: proper tool selection, tool maintenance and sharpening, and training of the worker with respect to proper biomechanical technique
  • training in work organization: job planning, safety/hazard assessment, site preparation and continual worker awareness with respect to work task and surroundings.


The goal of successful training in work technique and philosophy should be: implementation of proper work planning and precautionary measures, hazard recognition, active hazard avoidance and minimization of injury in the event of accident.

Factors Related to Harvesting Hazards

Because non-wood harvesting, by its nature, occurs in the open, subject to changing weather conditions and other natural factors, and because it is predominantly non-mechanized, workers are particularly subject to the environmental effects of geography, topography, climate and season. After considerable physical efforts and fatigue, weather conditions can contribute to work-related health problems and accidents (see table 2).

Table 2.  Non-wood harvesting hazards and examples.

Non-wood harvesting hazards


Biological agents

Bites and stings (external vector, systemic poisons)

Plant contact (external vector, topical poisons)

Ingestion (internal vector, systemic poisons)

Biomechanical action

Improper technique or repetitive-use injury related to bending, carrying, cutting, lifting, loading

Climatological conditions

Excessive heat and cold effects, either externally induced (environment) or due to work effort

Tools and techniques

Cuts, mechanical hazards, draught animal handling, small vehicle operation


Altercation, animal attack, difficult terrain, fatigue, loss of orientation, working at heights, working in remote locations, working on or crossing waterways


Non-wood harvesting operations tend to be in remote areas. This poses a form of hazard due to a lack of proximity to medical care in the event of accident. This would not be expected to increase accident frequency but certainly may increase the potential severity of any injury.



Saturday, 12 March 2011 17:14

Tree Planting

Tree planting consists of putting seedlings or young trees into the soil. It is mainly done to re-grow a new forest after harvesting, to establish a woodlot or to change the use of a piece of land (e.g., from a pasture to a woodlot or to control erosion on a steep slope). Planting projects can amount to several million plants. Projects may be executed by the forest owners’ private contractors, pulp and paper companies, the government’s forest service, non-governmental organizations or cooperatives. In some countries, tree planting has become a veritable industry. Excluded here is the planting of large individual trees, which is considered more the domain of landscaping than forestry.

The workforce includes the actual tree planters as well as tree nursery staff, workers involved in transporting and maintaining the plants, support and logistics (e.g., managing, cooking, driving and maintaining vehicles and so on) and quality control inspectors. Women comprise 10 to 15% of the tree-planter workforce. As an indication of the importance of the industry and the scale of activities in regions where forestry is of economic importance, the provincial government in Quebec, Canada, set an objective of planting 250 million seedlings in 1988.

Planting Stock

Several technologies are available to produce seedlings or small trees, and the ergonomics of tree planting will vary accordingly. Tree planting on flat land can be done by planting machines. The role of the worker is then limited to feeding the machine manually or merely to controlling quality. In most countries and situations, however, site preparation may be mechanized, but actual planting is still done manually.

In most reforestation, following a forest fire or clear cutting, for example, or in afforestation, seedlings varying from 25 to 50 cm in height are used. The seedlings are either bare-rooted or have been grown in containers. The most common containers in tropical countries are 600 to 1,000 cm3. Containers may be arranged in plastic or styrofoam trays which usually hold from 40 to 70 identical units. For some purposes, larger plants, 80 to 200 cm, may be needed. They are usually bare-rooted.

Tree planting is seasonal because it depends on rainy and/or cool weather. The season lasts 30 to 90 days in most regions. Although it may seem a lesser seasonal occupation, tree planting must be considered a major long-term strategic activity, both for the environment and for revenue where forestry is an important industry.

Information presented here is based mainly on the Canadian experience, but many of the issues can be extrapolated to other countries with a similar geographical and economic context. Specific practices and health and safety considerations for developing countries are also addressed.

Planting Strategy

Careful evaluation of the site is important for setting adequate planting targets. A superficial approach can hide field difficulties that will slow down the planting and overburden the planters. Several strategies exist for planting large areas. One common approach is to have a team of 10 to 15 planters equally spaced in a row, who progress at the same pace; a designated worker then has the task of bringing in enough seedlings for the whole team, usually by means of small off-road vehicles. One other common method is to work with several pairs of planters, each pair being responsible for fetching and carrying their own small stock of plants. Experienced planters will know how to space out their stock to avoid losing time carrying plants back and forth. Planting alone is not recommended.

Seedling Transport

Planting relies on the steady supply of seedlings to the planters. They are brought in several thousands at a time from the nurseries, on trucks or pick-ups as far as the road will go. The seedlings must be unloaded rapidly and watered regularly. Modified logging machinery or small off-road vehicles can be used to carry the seedlings from the main depot to the planting sites. Where seedlings have to be carried by workers, such as in many developing countries, the workload is very heavy. Suitable back-packs should be used to reduce fatigue and risk of injuries. Individual planters will carry from four to six trays to their respective lots. Since most planters are paid at a piece rate, it is important for them to minimize unproductive time spent travelling, or fetching or carrying seedlings.

Equipment and Tools

The typical equipment carried by a tree planter includes a planting shovel or a dibble (a slightly conical metal cylinder at the end of a stick, used to make holes closely fitting the dimensions of containerized seedlings), two or three plant container trays carried by a harness, and safety equipment such as toe-capped boots and protective gloves. When planting bare-rooted seedlings, a pail containing enough water to cover the seedling’s roots is used instead of the harness, and is carried by hand. Various types of tree-planting hoes are also widely used for bare-rooted seedlings in Europe and North America. Some planting tools are manufactured by specialized tool companies, but many are made in local shops or are intended for gardening and agriculture, and present some design deficiencies such as excess weight and improper length. The weight typically carried is presented in table 1.

Table 1. Typical load carried while planting.


 Weight in kg    

Commercially available harness


Three 45-seedling container trays, full   


Typical planting tool (dibble)





Planting Cycle

One tree-planting cycle is defined as the series of steps necessary to put one seedling into the ground. Site conditions, such as slope, soil and ground cover, have a strong influence on productivity. In Canada the production of a planter can vary from 600 plants per day for a novice to 3,000 plants per day for an experienced individual. The cycle may be subdivided as follows:

Selection of a micro-site. This step is fundamental for the survival of the young trees and depends on several criteria taken into account by quality control inspectors, including distance from preceding plant and natural offspring, closeness to organic material, absence of surrounding debris and avoidance of dry or flooded spots. All these criteria must be applied by the planter for each and every tree planted, since their non-observance can lead to a financial penalty.

Ground perforation. A hole is made in the ground with the planting tool. Two operating modes are observed, depending on the type of handle and the length of the shaft. One consists of using the mass of the body applied to a step bar located at the lower extremity of the tool to force it into the ground, while the other one involves raising the tool at arm’s length and forcefully plunging it into the ground. To avoid soil particles falling into the hole when the tool is removed, planters have the habit of smoothing its walls either by turning the tool around its long axis with a movement of the hand, or by flaring it with a circular motion of the arm.

Insertion of the plant into the cavity. If the planter is not yet holding a seedling, he or she grabs one from the container, bends down, inserts it into the hole and straightens up. The plant must be straight, firmly inserted into the soil, and the roots must be completely covered. It is interesting to note here that the tool plays an important secondary role by supplying a support for the planter as he or she bends down and straightens up, thus relieving the back muscles. Back movements can be straight or flexed, depending on the length of the shaft and the type of handle.

Soil compaction. Soil is compacted around the newly planted seedling to set it in the hole and to eliminate air that could dry the roots. Even though a trampling action is recommended, a forceful stamping of the feet or heel is more often observed.

Moving to the next micro-site. The planter proceeds to the next micro-site, generally 1.8 m away. This distance is usually evaluated by sight by experienced planters. While proceeding to the site, he or she must identify hazards on the way, plan a path around them, or determine another evasive strategy. In figure 1, the planter in the foreground is about to insert the seedling in the hole. The planter in the background is about to make a hole with a straight-handle planting tool. Both carry the seedlings in containers attached to a harness. Seedlings and equipment can weigh up to 16.8 kg (see table 1). Also note that the planters are fully covered by clothes to protect themselves against insects and the sun.

Figure 1. Tree planters in action in Canada


Hazards, Outcomes and Preventive Measures

Few studies worldwide have been devoted to the health and safety of tree planters. Although bucolic in appearance, tree planting carried out on an industrial basis can be strenuous and hazardous. In a pioneering study conducted by Smith (1987) in British Columbia, it was found that 90% of the 65 planters interviewed had suffered an illness, injury or accident during life-time tree-planting activities. In a similar study conducted by IRSST, the Quebec Institute of Occupational Health and Safety (Giguère et al. 1991, 1993), 24 out of 48 tree planters reported having suffered from a work-related injury during the course of their planting careers. In Canada, 15 tree planters died between 1987 and 1991 of the following work-related causes: road accidents (7), wild animals (3), lightning (2), lodging incidents (fire, asphyxia—2) and heat stroke (1).

Although scarce and conducted on a small number of workers, the few investigations of physiological indicators of physical strain (heart rate, blood haematology parameters, elevated serum enzymes activity) all concluded that tree planting is a highly strenuous occupation both in terms of cardiovascular and musculoskeletal strain (Trites, Robinson and Banister 1993; Robinson, Trites and Banister 1993; Giguère et al. 1991; Smith 1987). Banister, Robinson and Trites (1990) defined “tree-planter burnout”, a condition originating from haematological deficiency and characterized by the presence of lethargy, weakness and light-headedness similar to the “adrenal exhaustion syndrome” or “sport anaemia” developed by training athletes. (For data on workload in Chile, see Apud and Valdés 1995; for Pakistan, see Saarilahti and Asghar 1994).

Organizational factors. Long workdays, commuting and strict quality control, coupled with the piece-work incentive (which is a widespread practice among tree-planting contractors), may strain the physiological and psychological equilibrium of the worker and lead to chronic fatigue and stress (Trites, Robinson and Banister 1993). A good working technique and regular short pauses improve daily output and help to avoid burnout.

Accidents and injuries. Data presented in table 2 provide an indication of the nature and causes of accidents and injuries as they were reported by the tree-planter population participating in the Quebec study. The relative importance of accidents by body part affected shows that injuries to the lower extremities are more frequently reported than those to the upper extremities, if the percentages for knees, feet, legs and ankles are added together. The environmental setting is favourable to tripping and falling accidents. Injuries associated with forceful movements and lesions caused by tools, cutting scraps or soil debris are also of relevance.

Table 2. Frequency grouping of tree-planting accidents by body parts affected (in percentage of 122 reports by 48 subjects in Quebec).


 Body part  

 % total  

 Related causes




 Falls, contact with tool, soil compaction




 Equipment contact, biting and stinging insects, sunburn, chapping




 Insects, insect repellent, twigs




 Frequent bending, load carrying




 Soil compaction, blisters




 Chapping, scratches from contact with soil




 Falls, contact with tool




 Hidden rocks




 Trips and falls, hidden obstacles, contact with tool





Source: Giguere et al. 1991, 1993.

A well-prepared planting site, free of bushes and obstacles, will speed up planting and reduce accidents. Scrap should be disposed of in piles instead of furrows to allow easy circulation of the planters on the site. Tools should have straight handles to avoid injuries, and be of a contrasting colour. Shoes or boots should be sturdy enough to protect the feet during the repeated contact with the planting tool and while trampling the soil; sizes should be available for male and female planters, and the sole, sized properly for both men and women, should have a good grip on wet rocks or stumps. Gloves are useful to reduce the occurrence of blistering and of cuts and bruises from inserting the seedling into the soil. They also make the handling of conifer or thorny seedlings more comfortable.

Camp life and outdoor work. In Canada and a number of other countries, planters often have to live in camps. Working in the open requires protection against the sun (sun glasses, hats, sun block) and against biting and stinging insects. Heat stress can also be significant, and prevention calls for the possibility of adjusting the work-rest regimen and the availability of potable liquids to avoid dehydration.

It is important to have first aid equipment and some of the personnel trained as paramedics. Training should include emergency treatment of heat stroke and allergy caused by the venom of wasps or snakes. Planters should be checked for tetanus vaccination and for allergy before being sent to remote sites. Emergency communication systems, evacuation procedures and assembly signal (in case of a forest fire, sudden wind or sudden thunderstorm, or the presence of dangerous wild animals and so on) are essential.

Chemical hazards. The use of pesticides and fungicides to protect the seedlings (during cultivation or storage) is a potential risk when handling freshly sprayed plants (Robinson, Trites and Banister 1993). Eye irritation may occur due to the constant need to apply insect-repelling lotions or sprays.

Musculoskeletal and physiological load. Although there is no specific epidemiological literature linking musculoskeletal problems and tree planting, the forceful movements associated with load carrying, as well as the range of postures and muscular work involved in the planting cycle, undoubtedly constitute risk factors, which are exacerbated by the repetitive nature of the work.

Extreme flexions and extensions of the wrists, in grabbing seedlings in the trays, for example, and shock transmission to the hands and arms occurring when the planting tool hits a hidden rock, are among the possible biomechanical hazards to the upper limbs. The overall weight carried, the frequency of lifting, the repetitive and physical nature of the work, especially the intensive muscular effort required when plunging the dibble into the ground, contribute to the muscular strain exerted on upper limbs.

Low-back problems could be related to the frequency of bending. Handling of seedling trays (3.0 to 4.1 kg each when full) when unloading delivery trucks is also a potential risk. Carrying loads with harnesses, especially if the weight is not properly distributed on the shoulders and around the waist, is also likely to engender back pain.

The muscular load on lower limbs is obviously extensive. Walking several kilometres a day while carrying a load on rough terrain, sometimes going uphill, can rapidly become strenuous. Additionally, the work involves frequent knee flexions, and the feet are used continuously. Most tree planters use their feet to clear local debris with a lateral movement before making a hole. They also use their feet in putting weight on the tool’s footrest to aid penetration into the soil and to compact the soil around the seedling after it has been inserted.

Prevention of musculoskeletal strain relies on the minimization of carried loads, in terms of weight, frequency and distance, in conjunction with the optimization of working postures, which implies proper working tools and practices.

If seedlings must be carried in a pail, for instance, water can be replaced by wet peat moss to reduce carried weight. In Chile, replacing heavy wooden boxes for carrying seedlings by lighter cardboard ones increased output by 50% (Apud and Valdés 1995). Tools also have to be well adapted to the job. Replacing a pickaxe and shovel with a specially designed pick-hoe reduced workload by 50% and improved output by up to 100% in reforestation in Pakistan (Saarilahti and Asghar 1994). The weight of the planting tool is also crucial. For example, in a field survey of planting tools conducted in Quebec, variations ranged from 1.7 to 3.1 kg, meaning that choosing the lightest model may save 1,400 kg of lifted weight daily based on 1,000 lifts per day.

Planting tools with long, straight handles are preferred since if the tool hits a hidden rock, the hand will slip on the handle instead of absorbing the shock. A smooth, tapered handle allows an optimum grip for a greater percentage of the population. The Forest Engineering Research Institute of Canada recommends adjustable tools with shock-absorbing properties, but reports that none were available at the time of their 1988 survey (Stjernberg 1988).

Planters should also be educated about optimal working postures. Using the body weight to insert the dibble instead of using muscular effort, avoiding back twisting or exertion of the arms while they are fully extended, avoiding planting downhill and using the planting tool as a support when bending, for example, can all help minimize musculoskeletal strain. Novice planters should not be paid piece rate until they are fully trained.



Saturday, 12 March 2011 17:22

Forest Fire Management and Control

The Relevance of Forest Fires

One important task for forest management is the protection of the forest resource base.

Out of many sources of attacks against the forest, fire is often the most dangerous. This danger is also a real threat for the people living inside or adjacent to the forest area. Each year thousands of people lose their homes due to wildfires, and hundreds of people die in these accidents; additionally tens of thousands of domestic animals perish. Fire destroys agricultural crops and leads to soil erosion, which in the long run is even more disastrous than the accidents described before. When the soil is barren after the fire, and heavy rains soak the soil, huge mud- or landslides can occur.

It is estimated that every year:

  • 10 to 15 million hectares of boreal or temperate forest burn.
  • 20 to 40 million hectares of tropical rain forest burn.
  • 500 to 1,000 million hectares of tropical and subtropical savannahs, woodlands and open forests burn.


More than 90% of all this burning is caused by human activity. Therefore, it is quite clear that fire prevention and control should receive top priority among forest management activities.

Risk Factors in Forest Fires

The following factors make fire-control work particularly difficult and dangerous:

  • excessive heat radiated by the fire (fires always occur during hot weather)
  • poor visibility (due to smoke and dust)
  • difficult terrain (fires always follow wind patterns and generally move uphill)
  • difficulty getting supplies to the fire-fighters (food, water, tools, fuel)
  • often obligatory to work at night (easiest time to “kill” the fire)
  • impossibility of outrunning a fire during strong winds (fires move faster than any person can run)
  • sudden changes in the wind direction, so that no one can exactly predict the spread of the fire
  • stress and fatigue, causing people to make disastrous judgement errors, often with fatal results.


Activities in Forest Fire Management

The activities in forest fire management can be divided into three different categories with different objectives:

  • fire prevention (how to prevent fires from happening)
  • fire detection (how to report the fires as fast as possible)
  • fire suppression (the work to put out the fire, actually fighting the fire).


Occupational dangers

Fire prevention work is generally a very safe activity.

Fire detection safety is mostly a question of safe driving of vehicles, unless aircraft are used. Fixed-wing aircraft are especially vulnerable to strong uplifting air streams caused by the hot air and gases. Each year tens of air crews are lost due to pilot errors, especially in mountainous conditions.

Fire suppression, or actual fighting of the fire, is a very specialized operation. It has to be organized like a military operation, because negligence, non-obedience and other human errors may not only endanger the firefighter, but may also cause the death of many others as well as extensive property damage. The whole organization has to be clearly structured with good coordination between forestry staff, emergency services, fire brigades, police and, in large fires, the armed forces. There has to be a single line of command, centrally and onsite.

Fire suppression mostly involves the establishment or maintenance of a network of fire-breaks. These are typically 10- to 20-metre-wide strips cleared of all vegetation and burnable material. Accidents are mostly caused by cutting tools.

Major wildfires are, of course, the most hazardous, but similar problems arise with prescribed burning or “cold fires”, when mild burns are allowed to reduce the amount of inflammable material without damaging the vegetation. The same precautions apply in all cases.

Early intervention

Detecting the fire early, when it is still weak, will make its control easier and safer. Previously, detection was based on observations from the ground. Now, however, infrared and microwave equipment attached to aircraft can detect an early fire. The information is relayed to a computer on the ground, which can process it and give the precise location and temperature of the fire, even when there are clouds. This allows ground crews and/or smoke jumpers to attack the fire before it spreads widely.

Tools and equipment

Many rules are applicable to the firefighter, who may be a forest worker, a volunteer from the community, a government employee or a member of a military unit ordered to the area. The most important is: never go to fight a fire without your own personal cutting tool. The only way to escape the fire may be to use the tool to remove one of the components of the “fire triangle”, as shown in figure 1. The quality of that tool is critical: if it breaks, the fire fighter may lose his or her life.

Figure 1. Forest firefighter safert equipment


This also puts a very special emphasis on the quality of the tool; bluntly put, if the metal part of the tool breaks, the fire-fighter may lose his or her life. Forest firefighter safety equipment is shown in figure 2.

Figure 2. Forest firefighter safety equipment


Terrestrial firefighting

The preparation of fire breaks during an actual fire is especially dangerous because of the urgency of controlling the advance of the fire. The danger may be multiplied by poor visibility and changing wind direction. In fighting fires with heavy smoke (e.g., peat-land fires), lessons learned from such a fire in Finland in 1995 include:

  • Only experienced and physically very fit people should be sent out in heavy smoke conditions.
  • Each person should have a radio to receive directions from an hovering aircraft.
  • Only people with breathing apparatus or gas masks should be included.


The problems are related to poor visibility and changing wind directions.

When an advancing fire threatens dwellings, the inhabitants may have to be evacuated. This presents an opportunity for thieves and vandals, and calls for diligent policing activities.

The most dangerous work task is the making of backfires: hurriedly cutting through the trees and underbrush to form a path parallel to the advancing line of fire and setting it afire at just the right moment to produce a strong draught of air heading toward the advancing fire, so that the two fires meet. The draught from the advancing fire is caused by the need of the advancing fire to pull oxygen from all sides of the fire. It is very clear that if the timing fails, then the whole crew will be engulfed by strong smoke and exhausting heat and then will suffer a lack of oxygen. Only the most experienced people should set backfires, and they should prepare escape routes in advance to either side of the fire. This backfiring system should always be practised in advance of the fire season; this practice should include the use of equipment like torches for lighting the backfire. Ordinary matches are too slow!

As a last effort for self-preservation, a firefighter can scrape all burning materials in a 5 m diameter, dig a pit in the centre, cover him or herself with soil, soak headgear or jacket and put it over his or her head. Oxygen is often available only at 1 to 2 centimetres from ground level.

Water bombing by aircraft

The use of aircraft for fighting fires is not new (the dangers in aviation are described elsewhere in this Encyclopaedia). There are, however, some activities that are very dangerous for the ground crew in a forest fire. The first is related to the official sign language used in aircraft operations—this has to be practised during training.

The second is how to mark all areas where the aircraft is going to load water for its tanks. To make this operation as safe as possible, these areas should be marked off with floating buoys to obviate the pilot’s need to use guesswork.

The third important matter is to keep constant radio contact between the ground crew and the aircraft as it prepares to release its water. The release from small heli-buckets of 500 to 800 litres is not that dangerous. Large helicopters, however, like the MI-6, carry 2,500 litres, while the C-120 aircraft takes 8,000 litres and the IL-76 can drop 42,000 litres in one sweep. If, by chance, one of these big loads of water lands on crew members on the ground, the impact could kill them.

Training and organization

One essential requirement in firefighting is to line up all firefighters, villagers and forest workers to organize joint firefighting exercises before the beginning of fire season. This is the best way to secure successful and safe firefighting. At the same time, all the work functions of the various levels of command should be practised in the field.

The selected fire chief and leaders should be the ones with the best knowledge of local conditions and of government and private organizations. It is obviously dangerous to assign somebody either too high up the hierarchy (no local knowledge) or too low down the hierarchy (often lacking authority).



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Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides