The most common form of occupational dermatosis to be found among construction workers is caused by exposure to cement. Depending on the country, 5 to 15% of construction workers—most of them masons—acquire dermatosis during their work lives. Two types of dermatosis are caused by exposure to cement: (1) toxic contact dermatitis, which is local irritation of skin exposed to wet cement and is caused mainly by the alkalinity of the cement; and (2) allergic contact dermatitis, which is a generalized allergic skin reaction to exposure to the water-soluble chromium compound found in most cement. One kilogramme of normal cement dust contains 5 to 10 mg of water-soluble chromium. The chromium originates both in the raw material and the production process (mainly from steel structures used in production).

Allergic contact dermatitis is chronic and debilitating. If not properly treated, it can lead to decreased worker productivity and, in some cases, early retirement. In the 1960s and 1970s, cement dermatitis was the most common reported cause of early retirement among construction workers in Scandinavia. Therefore, technical and hygienic procedures were undertaken to prevent cement dermatitis. In 1979, Danish scientists suggested that reducing hexavalent water-soluble chromium to trivalent insoluble chromium by adding ferrous sulphate during production would prevent chromium-induced dermatitis (Fregert, Gruvberger and Sandahl 1979).

Denmark passed legislation requiring the use of cement with lower levels of hexavalent chromium in 1983. Finland followed with a legislative decision at the beginning of 1987, and Sweden and Germany adopted administrative decisions in 1989 and 1993, respectively. For the four countries, the accepted level of water-soluble chromium in cement was determined to be less than 2 mg/kg.

Before Finland’s action in 1987, the Board of Labour Protection wanted to evaluate the occurrence of chromium dermatitis in Finland. The Board asked the Finnish Institute of Occupational Health to monitor the incidence of occupational dermatosis among construction workers to assess the effectiveness of adding ferrous sulphate to cement in order to prevent chromium-induced dermatitis. The Institute monitored the incidence of occupational dermatitis through the Finnish Register of Occupational Diseases from 1978 through 1992. The results indicated that chromium-induced hand dermatitis practically disappeared among construction workers, whereas the incidence of toxic contact dermatitis remained unchanged during the study period (Roto et al. 1996).

In Denmark, chromate sensitization from cement was detected in only one case among 4,511 patch tests conducted between 1989 and 1994 among patients of a large dermatological clinic, 34 of whom were construction workers. The expected number of chromate-positive construction workers was 10 of 34 subjects (Zachariae, Agner and Menn J1996).

There seems to be increasing evidence that the addition of ferrous sulphate to cement prevents chromate sensitization among construction workers. In addition, there has been no indication that, when added to cement, ferrous sulphate has negative effects on the health of exposed workers. The process is economically feasible, and the properties of the cement do not change. It has been calculated that adding ferrous sulphate to cement increases the production costs by US$1.00 per tonne. The reductive effect of ferrous sulphate lasts 6 months; the product must be kept dry before mixing because humidity neutralizes the effect of the ferrous sulphate.

The addition of ferrous sulphate to cement does not change its alkalinity. Therefore workers should use proper skin protection. In all circumstances, construction workers should avoid touching wet cement with unprotected skin. This precaution is especially important in initial cement production, where minor adjustments to moulded elements are made manually.

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

In the production and refining of metals, valuable components are separated from worthless material in a series of different physical and chemical reactions. The end-product is metal containing controlled amounts of impurities. Primary smelting and refining produces metals directly from ore concentrates, while secondary smelting and refining produces metals from scrap and process waste. Scrap includes bits and pieces of metal parts, bars, turnings, sheets and wire that are off-specification or worn-out but are capable of being recycled (see the article “Metal reclamation” in this chapter).

Overview of Processes

Two metal recovery technologies are generally used to produce refined metals, pyrometallurgical and hydrometallurgical. Pyrometallurgical processes use heat to separate desired metals from other materials. These processes use differences between oxidation potentials, melting points, vapour pressures, densities and/or miscibility of the ore components when melted. Hydrometallurgical technologies differ from pyrometallurgical processes in that the desired metals are separated from other materials using techniques that capitalize on differences between constituent solubilities and/or electrochemical properties while in aqueous solutions.

Pyrometallurgy

 During pyrometallic processing, an ore, after being beneficiated (concentrated by crushing, grinding, floating and drying), is sintered or roasted (calcined) with other materials such as baghouse dust and flux. The concentrate is then smelted, or melted, in a blast furnace in order to fuse the desired metals into an impure molten bullion. This bullion then undergoes a third pyrometallic process to refine the metal to the desired level of purity. Each time the ore or bullion is heated, waste materials are created. Dust from ventilation and process gases may be captured in a baghouse and are either disposed of or returned to the process, depending upon the residual metal content. Sulphur in the gas is also captured, and when concentrations are above 4% it can be turned into sulphuric acid. Depending upon the origin of the ore and its residual metals content, various metals such as gold and silver may also be produced as by-products.

Roasting is an important pyrometallurgical process. Sulphating roasting is used in the production of cobalt and zinc. Its purpose is to separate the metals so that they can be transformed into a water-soluble form for further hydrometallurgical processing.

The smelting of sulphidic ores produces a partially oxidized metal concentrate (matte). In smelting, the worthless material, usually iron, forms a slag with fluxing material and is converted into the oxide. The valuable metals acquire the metallic form at the converting stage, which takes place in converting furnaces. This method is used in copper and nickel production. Iron, ferrochromium, lead, magnesium and ferrous compounds are produced by reduction of the ore with charcoal and a flux (limestone), the smelting process usually taking place in an electric furnace. (See also the Iron and steel industry chapter.) Fused salt electrolysis, used in aluminium production, is another example of a pyrometallurgical process.

The high temperature required for the pyrometallurgical treatment of metals is obtained by burning fossil fuels or by using the exothermic reaction of the ore itself (e.g., in the flash smelting process). The flash smelting process is an example of an energy-saving pyrometallurgical process in which iron and sulphur of the ore concentrate are oxidized. The exothermic reaction coupled with a heat recovery system saves a lot of energy for smelting. The high sulphur recovery of the process is also beneficial for environmental protection. Most of the recently built copper and nickel smelters use this process.

Hydrometallurgy

Examples of hydrometallurgical processes are leaching, precipitation, electrolytic reduction, ion exchange, membrane separation and solvent extraction. The first stage of hydrometallurgical processes is the leaching of valuable metals from less valuable material, for example, with sulphuric acid. Leaching is often preceded by pre-treatment (e.g., sulphating roasting). The leaching process often requires high pressure, the addition of oxygen or high temperatures. Leaching may also be carried out with electricity. From the leaching solution the desired metal or its compound is recovered by precipitation or reduction using different methods. Reduction is carried out, for example, in cobalt and nickel production with gas.

Electrolysis of metals in aqueous solutions is also considered to be a hydrometallurgical process. In the process of electrolysis the metallic ion is reduced to the metal. The metal is in a weak acid solution from which it precipitates on cathodes under the influence of an electrical current. Most non-ferrous metals can also be refined by electrolysis.

Often metallurgical processes are a combination of pyro- and hydrometallurgical processes, depending on the ore concentrate to be treated and the type of metal to be refined. An example is nickel production.

Hazards and Their Prevention

Prevention of health risks and accidents in the metallurgical industry is primarily an educational and technical question. Medical examinations are secondary and have only a complementary role in the prevention of health risks. A harmonious exchange of information and collaboration between the planning, line, safety and occupational health departments within the company give the most efficient result in the prevention of health risks.

The best and least costly preventive measures are those taken at the planning stage of a new plant or process. In planning of new production facilities, the following aspects should be taken into account as a minimum:

• The potential sources of air contaminants should be enclosed and isolated.
• The design and placement of the process equipment should allow easy access for maintenance purposes.
• Areas in which a sudden and unexpected hazard may occur should be monitored continuously. Adequate warning notices should be included. For example, areas in which arsine or hydrogen cyanide exposure might be possible should be under continuous monitoring.
• Addition and handling of poisonous process chemicals should be planned so that manual handling can be avoided.
• Personal occupational hygiene sampling devices should be used in order to evaluate the real exposure of the individual worker, whenever possible. Regular fixed monitoring of gases, dusts and noise gives an overview of exposure but has only a complementary role in the evaluation of exposure dose.
• In space planning, the requirements of future changes or extensions of the process should be taken into account so that the occupational hygiene standards of the plant will not worsen.
• There should be a continuous system of training and education for safety and health personnel, as well as for foremen and workers. New workers in particular should be thoroughly informed about potential health risks and how to prevent them in their own working environments. In addition, training should be done whenever a new process is introduced.
• Work practices are important. For example, poor personal hygiene by eating and smoking in the worksite may considerably increase personal exposure.
• The management should have a health and safety monitoring system which produces adequate data for technical and economic decision making.

The following are some of the specific hazards and precautions that are found in smelting and refining.

Injuries

The smelting and refining industry has a higher rate of injuries than most other industries. Sources of these injuries include: splattering and spills of molten metal and slag resulting in burns; gas explosions and explosions from contact of molten metal with water; collisions with moving locomotives, wagons, travelling cranes and other mobile equipment; falls of heavy objects; falls from a height (e.g., while accessing a crane cab); and slipping and tripping injuries from obstruction of floors and passageways.

Precautions include: adequate training, appropriate personal protective equipment (PPE) (e.g., hard hats, safety shoes, work gloves and protective clothing); good storage, housekeeping and equipment maintenance; traffic rules for moving equipment (including defined routes and an effective signal and warning system); and a fall protection programme.

Heat

Heat stress illnesses such as heat stroke are a common hazard, primarily due to infrared radiation from furnaces and molten metal. This is especially a problem when strenuous work must be done in hot environments.

Prevention of heat illnesses can involve water screens or air curtains in front of furnaces, spot cooling, enclosed air-conditioned booths, heat-protective clothing and air-cooled suits, allowing sufficient time for acclimatization, work breaks in cool areas and an adequate supply of beverages for frequent drinking.

Chemical hazards

Exposure to a wide variety of hazardous dusts, fumes, gases and other chemicals can occur during smelting and refining operations. Crushing and grinding ore in particular can result in high exposures to silica and toxic metal dusts (e.g., containing lead, arsenic and cadmium). There can also be dust exposures during furnace maintenance operations. During smelting operations, metal fumes can be a major problem.

Dust and fume emissions can be controlled by enclosure, automation of processes, local and dilution exhaust ventilation, wetting down of materials, reduced handling of materials and other process changes. Where these are not adequate, respiratory protection would be needed.

Many smelting operations involve the production of large amounts of sulphur dioxide from sulphide ores and carbon monoxide from combustion processes. Dilution and local exhaust ventilation (LEV) are essential.

Sulphuric acid is produced as a by-product of smelting operations and is used in electrolytic refining and leaching of metals. Exposure can occur both to the liquid and to sulphuric acid mists. Skin and eye protection and LEV is needed.

The smelting and refining of some metals can have special hazards. Examples include nickel carbonyl in nickel refining, fluorides in aluminium smelting, arsenic in copper and lead smelting and refining, and mercury and cyanide exposures during gold refining. These processes require their own special precautions.

Other hazards

Glare and infrared radiation from furnaces and molten metal can cause eye damage including cataracts. Proper goggles and face shields should be worn. High levels of infrared radiation may also cause skin burns unless protective clothing is worn.

High noise levels from crushing and grinding ore, gas discharge blowers and high-power electric furnaces can cause hearing loss. If the source of the noise cannot be enclosed or isolated, then hearing protectors should be worn. A hearing conservation program including audiometric testing and training should be instituted.

Electrical hazards can occur during electrolytic processes. Precautions include proper electrical maintenance with lockout/tagout procedures; insulated gloves, clothing and tools; and ground fault circuit interrupters where needed.

Manual lifting and handling of materials can cause back and upper extremity injuries. Mechanical lifting aids and proper training in lifting methods can reduce this problem.

Pollution and Environmental Protection

Emissions of irritant and corrosive gases like sulphur dioxide, hydrogen sulphide and hydrogen chloride may contribute to air pollution and cause corrosion of metals and concrete within the plant and in the surrounding environment. The tolerance of vegetation to sulphur dioxide varies depending on the type of forest and soil. In general, evergreen trees tolerate lower concentrations of sulphur dioxide than deciduous ones. Particulate emissions may contain non-specific particulates, fluorides, lead, arsenic, cadmium and many other toxic metals. Wastewater effluent may contain a variety of toxic metals, sulphuric acid and other impurities. Solid wastes can be contaminated with arsenic, lead, iron sulphides, silica and other pollutants.

Smelter management should include evaluation and control of emissions from the plant. This is specialized work which should be carried out only by personnel thoroughly familiar with the chemical properties and toxicities of the materials discharged from the plant processes. The physical state of the material, the temperature at which it leaves the process, other materials in the gas stream and other factors must all be considered when planning measures to control air pollution. It is also desirable to maintain a weather station, to keep meteorological records and to be prepared to reduce output when weather conditions are unfavourable for dispersal of stack effluents. Field trips are necessary to observe the effect of air pollution on residential and farming areas.

Sulphur dioxide, one of the major contaminants, is recovered as sulphuric acid when present in sufficient quantity. Otherwise, to meet emission standards, sulphur dioxide and other hazardous gaseous wastes are controlled by scrubbing. Particulate emissions are commonly controlled by fabric filters and electrostatic precipitators.

Large amounts of water are used in flotation processes such as copper concentration. Most of this water is recycled back into the process. Tailings from the flotation process are pumped as slurry into sedimentation ponds. Water is recycled in the process. Metal-containing process water and rainwater are cleaned in water-treatment plants before discharging or recycling.

Solid-phase wastes include slags from smelting, blowdown slurries from sulphur dioxide conversion to sulphuric acid and sludges from surface impoundments (e.g., sedimentation ponds). Some slags can be reconcentrated and returned to smelters for reprocessing or recovery of other metals present. Many of these solid-phase wastes are hazardous wastes that must be stored according to environmental regulations.

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The construction industry forms 5 to 15% of the national economy of most countries and is usually one of the three industries having the highest rate of work-related injury risks. The following chronic occupational health risks are pervasive (Commission of the European Communities 1993):

• Musculoskeletal disorders, occupational hearing loss, dermatitis and lung disorders are the most common occupational diseases.
• An increased risk of respiratory tract carcinomas and mesothelioma caused by asbestos exposure has been observed in all countries where occupational mortality and morbidity statistics are available.
• Disorders resulting from improper nutrition, smoking or use of alcohol and drugs are associated especially with migrant workers, a substantial portion of construction employment in many countries.

Preventive health services for construction workers should be planned with these risks as priorities.

Types of Occupational Health Services

Occupational health services for construction workers consist of three main models:

1. specialized services for construction workers
2. occupational health care for construction workers rendered by providers of broad-based occupational health services
3. health services provided voluntarily by the employer.

Specialized services are the most effective but also the most expensive in terms of direct costs. Experiences from Sweden indicate that the lowest injury rates on construction sites worldwide and a very low risk for occupational diseases among construction workers are associated with extensive preventive work through specialized service systems. In the Swedish model, called Bygghälsan, technical and medical prevention have been combined. Bygghälsan operates through regional centres and mobile units. During the severe economic recession of the late 1980s, however, Bygghälsan severely cut back its health service activities.

In countries that have occupational health legislation, construction companies usually buy the needed health services from companies serving general industries. In such cases, the training of occupational health personnel is important. Without special knowledge of the circumstances surrounding construction, medical personnel cannot provide effective preventive occupational health programmes for construction companies.

Some large multinational companies have well-developed occupational safety and health programmes that are part of the culture of the enterprise. The cost-benefit calculations have proved these activities economically profitable. Nowadays, occupational safety programmes are included in quality management of most international companies.

Mobile health clinics

Because construction sites are often situated far from any established providers of health services, mobile health service units may be necessary. Practically all countries that have specialized occupational health services for construction workers use mobile units for delivering the services. The mobile unit’s advantage is the saving of work time by bringing the services to worksites. Mobile health centres are contained in a specially equipped bus or trailer and are especially suitable for all types of screening procedures, such as periodic health examinations. Mobile services should be careful to arrange in advance for collaboration with local providers of health services in order to secure follow-up evaluation and treatment for workers whose test results suggest a health problem.

Standard equipment for a mobile unit includes a basic laboratory with a spirometer and an audiometer, an interview room and x-ray equipment, when needed. It is best to design module units as multipurpose spaces so they can be used for different types of projects. The Finnish experience indicates that mobile units are also suitable for epidemiological studies, which can be incorporated into occupational health programmes, if properly planned in advance.

Contents of preventive occupational health services

Identification of risk at construction sites should guide medical activity, although this is secondary to prevention through proper design, engineering and work organization. Risk identification requires a multidisciplinary approach; this requires close collaboration between the occupational health personnel and the enterprise. A systematic workplace survey of risks using standardized checklists is one option.

Preplacement and periodic health examinations are usually conducted according to requirements set by legislation or guidance provided by authorities. The examination’s content depends on the exposure history of each worker. Short work contracts and frequent turnover of the construction workforce can result in “missed” or “inappropriate” health examinations, a failure to follow up on findings or unwarranted duplication of health examinations. Therefore, regular standard periodic examinations are recommended for all workers. A standard health examination should contain: an exposure history; symptom and illness histories with special emphasis on musculoskeletal and allergic diseases; a basic physical examination; and audiometry, vision, spirometry and blood pressure tests. The examinations should also provide health education and information on how to avoid occupational risks known to be common.

Surveillance and Prevention of Key Construction-related Problems

Musculoskeletal disorders and their prevention

Musculoskeletal disorders have multiple origins. Lifestyle, hereditary susceptibility and ageing, combined with improper physical strain and minor injuries, are commonly accepted risk factors for musculoskeletal disorders. The types of musculoskeletal problems have different exposure patterns in different construction professions.

There is no reliable test to predict an individual’s risk for acquiring a musculoskeletal disorder. Medical prevention of musculoskeletal disorders is based on guidance in ergonomic matters and lifestyles. Preplacement and periodic examinations can be used for this purpose. Non-specific strength testing and routine x rays of the skeletal system have no specific value for prevention. Instead, early detection of symptoms and a detailed work history of musculoskeletal symptoms can be used as a basis for medical counselling. A programme that performs periodic symptom surveys to identify work factors that can be changed has been shown to be effective.

Often, workers who have been exposed to heavy physical loads or strain think the work keeps them fit. Several studies have proved that this is not the case. Therefore, it is important that, in the context of health examinations, the examinees be informed about proper ways to maintain their physical fitness. Smoking has also been associated with lumbar disk degeneration and low-back pain. Therefore, anti-smoking information and therapy should be included in the periodic health examinations, too (Workplace Hazard and Tobacco Education Project 1993).

Occupational noise-induced hearing loss

The prevalence of noise-induced hearing loss varies among construction occupations, depending on levels and duration of exposure. In 1974, less than 20% of Swedish construction workers at age 41 had normal hearing in both ears. Implementation of a comprehensive hearing conservation programme increased the proportion in that age group having normal hearing to almost 40% by the late 1980s. Statistics from British Columbia, Canada, show that construction workers generally suffer significant loss of hearing after working more than 15 years in the trades (Schneider et al. 1995). Some factors are thought to increase susceptibility to occupational hearing loss (e.g., diabetic neuropathy, hypercholesterolemia and exposure to certain ototoxic solvents). Whole-body vibration and smoking may have an additive effect.

A large-scale programme for hearing conservation is advisable for the construction industry. This type of programme requires not only collaboration at the worksite level, but also supportive legislation. Hearing conservation programmes should be specific in work contracts.

Occupational hearing loss is reversible in the first 3 or 4 years after initial exposure. Early detection of hearing loss will provide opportunities for prevention. Regular testing is recommended to detect the earliest possible changes and to motivate workers to protect themselves. At the time of testing, the exposed workers should be educated in the principles of personal protection, as well as the maintenance and proper use of protection devices.

Occupational dermatitis

Occupational dermatitis is prevented mainly by hygienic measures. The proper handling of wet cement and skin protection are effective in promoting hygiene. During health examinations, it is important to stress the importance of avoiding skin contact with wet cement.

Occupational lung diseases

Asbestosis, silicosis, occupational asthma and occupational bronchitis can be found among construction workers, depending on their past work exposures (Finnish Institute of Occupational Health 1987).

There is no medical method to prevent the development of carcinomas after someone has been sufficiently exposed to asbestos. Regular chest x rays, every third year, are the most common recommendation for medical surveillance; there is some evidence that x-ray screening improves the outcome in lung cancer (Strauss, Gleanson and Sugarbaker 1995). Spirometry and anti-smoking information are usually included in the periodic health examination. Diagnostic tests for the early diagnosis of asbestos-related malignant tumours are not available.

Malignant tumours and other lung diseases related to asbestos exposure are widely underdiagnosed. Therefore, many construction workers eligible for compensation remain without benefits. In the late 1980s and early 1990s, Finland conducted a nationwide screening of workers exposed to asbestos. The screening revealed that only one-third of the workers with asbestos-related diseases and who had access to occupational health services had been diagnosed earlier (Finnish Institute of Occupational Health 1994).

Special needs of migrant workers

Depending on the construction site, the social context, sanitary conditions and climate may present important risks to construction workers. Migrant workers often suffer from psychosocial problems. They have a higher risk of work-related injuries than native workers. Their risk of carrying infectious diseases, such as HIV/AIDS, tuberculosis, and parasitic diseases must be taken into account. Malaria and other tropical diseases are problems for workers in areas where they are endemic.

In many large construction projects, a foreign workforce is used. A preplacement medical examination should be conducted in the home country. Also, the spreading of contagious diseases must be prevented through proper vaccination programmes. In the host countries, proper vocational training, health and safety education, and housing should be organized. Migrant workers should be provided the same access to health care and social security as native workers (El Batawi 1992).

In addition to preventing construction-related ailments, the health practitioner should work to promote positive changes in lifestyle, which can improve a worker’s health overall. Avoiding alcohol and smoking are the most important and fruitful themes for health promotion for construction workers. It has been estimated that a smoker costs the employer 20 to 30% more than a non-smoking worker. Investments in anti-smoking campaigns pay not only in the short term, with lower accident risks and shorter sick leaves, but also in the long term, with lower risks of cardiovascular pulmonary diseases and cancer. In addition, tobacco smoke has harmful multiplier effects with most dusts, especially with asbestos.

Economic benefits

It is difficult to prove any direct economic benefit of occupational health services to an individual construction company, especially if the company is small. Indirect cost-benefit calculations show, however, that accident prevention and health promotion are economically beneficial. Cost-benefit calculations of investments in preventive programmes are available for companies to use internally. (For a model used extensively in Scandinavia, see Oxenburg 1991.)

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