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Monday, 14 March 2011 17:21

Chemical Hazards

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Fuel and Oils for Portable Machines

Portable forestry machines such as chain-saws, brush saws and mobile machines are sources of exhaust emissions of gasoline in logging operations. Gasoline contains mainly aromatic (including up to 5% benzene in some countries) and aliphatic hydrocarbons, additives and some impurities. During the cold season gasoline contains more lightweight and easily evaporating hydrocarbons than during warm season. Additives are organic lead compounds, alcohols and ethers which are used to increase the octane number of gasoline. In many cases, lead has been totally replaced by ethers and alcohols.

The portable machines used in forestry are powered by two-stroke engines, where lubricating oil is mixed with gasoline. Lubrication oils as well as chain oils are mineral oils, synthetic oils or vegetable oils. The exposure to gasoline and lubrication and chain oil may occur during mixing fuel and filling as well as during logging. Fuels are also a fire hazard, of course, and require careful storage and handling.

Oil aerosols may create health hazards such as irritation of the upper respiratory tract and eyes, as well as skin problems. The exposure of lumberjacks to oil aerosols was studied during manual logging. Both mineral and vegetable oils were investigated. The exposure of forestry workers to oil aerosols was on the average 0.3 mg/m3 for mineral oil and even less for vegetable oil.

The mechanization of forestry work is increasing rapidly. The machines in logging operations use large amounts of fuel oil, lubricants and hydraulic oils in their engines and hydraulic systems. During maintenance and repair operations, the hands of machine operators are exposed to lubricants, hydraulic oils and fuel oils, which may cause irritant dermatitis. Mineral oils with short-chain hydrocarbons (C14–C21) are the most irritant. To avoid irritation, the skin must be protected from oil contact by protective gloves and good personal hygiene.


Exhaust Gases

The main component of chain-saw exhaust gases is unburned gasoline. Usually about 30% of the gasoline consumed by a chain-saw engine is emitted unburned. The main components of exhaust emission are hydrocarbons which are typical constituents of gasoline. Aromatic hydrocarbons, particularly toluene, are usually identified among them, but even benzene is found. Some of the exhaust gases are formed during combustion, and the main toxic product among them is carbon monoxide. As a result of combustion there are also aldehydes, mainly formaldehyde, and nitrogen oxides.

The exposure of workers to exhaust gases from chain-saws has been studied in Sweden. Operator exposure to chain-saw exhaust was evaluated under various logging situations. Measurements revealed no difference in average levels of exposure when logging in the presence or in the absence of snow. The felling operation, however, results in short-term high exposure levels, especially when the operation is performed while there is deep snow on the ground. This is judged to be the main cause of the discomfort experienced by loggers. Average exposure levels for loggers engaged only in felling were twice as high as those for cutters who also perform delimbing, bucking and manual skidding of timber. The latter operations involved considerably lower exposure. Typical average levels of exposure are as follows: hydrocarbons, 20 mg/m3; benzene, 0.6 mg/m3; formaldehyde, 0.1 mg/m3; carbon monoxide, 20 mg/m3.

These values are clearly below the 8-hour occupational exposure limit values in industrialized countries. However, loggers often complain about irritation of the upper respiratory tract and eyes, headache, nausea and fatigue, which can be at least partly explained by these exposure levels.

Pesticides and Herbicides

Pesticides are used in forests and forest nurseries to control fungi, insects and rodents. The overall quantities used are typically small when compared with agricultural use. In forests herbicides are used to control hardwood brush, weeds and grass in young softwood sapling stands. Phenoxy herbicides, glyphosate or triazines are used for this purpose. For occasional needs, insecticides, mainly organophosphorus compounds, organochlorine compounds or synthetic pyredroids may also be used. In forest nurseries dithiocarbamates are used regularly to protect softwood seedlings against fungus of pines. An overview of chemicals used in Europe and North America in the 1980s is provided in table 1. Many countries have taken measures to find alternatives to pesticides or to restrict their use. For more detail on the chemistry, chemical symptoms of intoxication and treatment see the chemicals section of this Encyclopaedia.

Table 1.  Examples of chemicals used in forestry in Europe and North America in the 1980s.




Benomyl, Borax, Carbendazim, Chlorothalonil, Dicropropene, Endosulphaani, Gamma-HCH, Mancozeb, Maneb, Methyl bromide, Metiram, Thiuram, Zineb

Game control

Polyvinyl acetate

Game damage control


Game repellents

Fish oil, tall oil


Allyl alcohol, Cyanazin, Dachtal, Dalapon, Dicamba, Dichlobenil, Diuron, Fosamine, Glyphosate, Hexazinone, MCPA, MCPB, Mecoprop (MCPP), MSMA, Oxyfluorten, Paraquat, Phenoxy herbicides (e.g., 2,4,5-T*, 2,4-D), Picloram, Pronoamide, Simazine, Sulphur, TCA, Terbuthiuron, Terbuthylazine, Trichlopyr, Trifluralin


Azinphos, Bacillus thuringiens, Bendiocarpanate, Carbaryl, Cypermethrin, Deltamethrin, Diflubenzuron, Ethylene dibromide, Fenitrothion, Fenvalerate, Lindane, Lindane+promecarb, Malathion, Parathion, Parathionmethyl, Pyrethrin, Permethrin, Propoxur, Propyzamide, Tetrachlorphinos, Trichlorfon


Captan, Chlorpyrifos, Diazinon, Metalyxyl, Napropamide, Sethoxydim, Traiadimefon, Sodium cyanide (rabbits)


Aluminium phosphide, Strychnine, Warfarin, Zinc phosphide, Ziram

Soil sterilant


Stump protection


Fuels and oils

Mineral oils, synthetic oils, vegetable oils, gasoline, diesel oil

Other chemicals

Fertilizers (e.g., urea), solvents (e.g., glycol ethers, long-chain alcohols), Desmetryn

* Restricted in some countries.

Source: Adapted from Patosaari 1987.

A wide variety of techniques are used for the application of pesticides to their intended target in forests and forestry nurseries. Common methods are aerial spraying, application from tractor-driven equipment, knapsack spraying, ULV spraying and the use of sprayers connected to brush saws.

The risk of exposure is similar to that in other pesticide applications. To avoid exposure to pesticides, forestry workers should use personal protective equipment (PPE) (e.g., cap, coveralls, boots and gloves). If toxic pesticides are applied, a respiratory device should also be worn during applications. Effective PPE often leads to heat build-up and excessive sweating. Applications should be planned for the coolest hours of the day and when it is not too windy. It is also important to wash all spills immediately with water and to avoid smoking and eating during spray operations.

The symptoms caused by excessive exposure to pesticides vary greatly depending on the compound used for application, but most often occupational exposure to pesticides will cause skin disorders. (For a more detailed discussion of pesticides used in forestry in Europe and northern America see FAO/ECE/ILO 1991.)


Other chemicals commonly used in forestry work are fertilizers and colourants used for timber marking. Timber marking is done either with a marking hammer or a spray bottle. The colourants contain glycol ethers, alcohols and other organic solvents, but the exposure level during the work is probably low. The fertilizers used in forestry have low toxicity, and the use of them is seldom a problem in respect of occupational hygiene.



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