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who work at compost facilities is low. Individuals who have asthma, diabetes or suppressed immune systems, however, should not work at a compost facility. The following guidelines are necessary to prevent illness: • workers must maintain high standards of hygiene such as washing hands before meals/breaks and before going home; • during dry weather, the composting area should be sprinkled with water to prevent dust; • to reduce dust inhalation, workers should wear masks or respirators at all times; • workers should wear safety shoes and safety glasses when operating the shredder; and • the composting facility should be located at a 41, considerable distance from hospitals and residential areas. Workers should be aware that disease producing microorganisms are common in the work environment. In order to reduce the risk of disease, uniforms should be provided to employees and time should be given to wash up before breaks and lunch and at the end of the work shift. Shower facilities should be available and clean clothing and shoes should be worn home by each employee. Cuts and bruises should receive prompt attention to prevent contact with the waste materials or feedstock. As mentioned, a potential risk to workers at composting sites may occur from exposure to Aspergillus fumigatus spores, which are pathogenic in susceptible individuals. The following cases of work -related illness have been reported: • Throat and nasal cultures indicated exposure to -_ Aspergillus fumigatus and one worker had a serious ear infection caused by exposure to Aspergillus fumigatus in a compost -exposed worker study (Clark et al). • Workers exposed to compost at plants in Philadelphia, Pennsylvania and Washington, D.C. between 1979 and 1981 were found to have an excess of nasal, ear and skin disorders compared to non -exposed workers. Symptoms of burning eyes and skin irritation were also reported more often in exposed workers. • In a study of workers at a household refuse and wastewater sludge compost facility in Sweden; nausea, headache, fever and diarrhea symptoms were more common than in controls. Heavy Metals Metals are essential to the normal growth of plants, animals and humans but in excess can be toxic. Heavy metals exist in mixed municipal solid waste and compost. An additional source of metals in sewage sludge derived co -compost is the metal content of the sewage sludge. if the wastewater treatment plant receives industrial effluents containing heavy metals, industrial pretreatment is necessary to reduce the source. It is difficult to remove the metals once they are in the sewage sludge therefore, it is advisable to control the problem at the source. The metals of major concern from compost are: • cadmium - ready bioaccumulates in leafy vegetables, grain products and fruit, toxic to man; • zinc - phytotoxic (toxic to plants) damage to the plant occurs before plant tissue levels reach human toxic levels; • nickel - extremely phytotoxic, accumulates in leafy vegetables, grasses and legumes; • copper - extremely phytotoxic, bioaccumulates in roots; • mercury - toxic to both man and plants, toxicity in plants occurs at .04 parts per million and fatal doses in man occur at 3 parts per million; and • lead - toxic to man, does not bioaccumulate in plants. Table 15 shows the concentrations of metals in soils and plants. TABLE 15 Typical Figures and Toxic Limits for Concentrations of Heavy Metals in Soils and Plants (parts per million, dry matter) SOIL PLANTS Common Toxic Metal Typical Range Range Limits Cadmium 0.06 0.01-0.7 0.2-0.8 100 Cobalt 8 1-40 0.05-0.5 — Copper 20 2-100 4-15 30 Lead 10 2-200 0.1-10 Manganese 850 1,000-4,000 15-100 500 Nickel 40 10-1,000 1 25 Zinc 50 10-300 8-15 500 Advanced Agronomy, W.H. Allaway, 20:235-271 1968. IV-4