Biological hazards of composting

Abstract

The biological process of composting involves the aerobic breakdown of complex organic substrates by means of a succession of microorganisms to give an end product with properties similar to those of humus found in soils. The initial heating up stage involves a succession of bacteria whilst the final maturation stages of the compost are carried out by thermophilic actinomycetes and fungi, mainly Aspergillus fumigatus. This wide range of organisms, however can cause health problems to the people directly involved in the process. These hazards can range from irritations caused by dust dispersal, to Organic Dust Toxic Syndrome ( also referred to as Monday morning fever ) caused by bacterial endotoxins present in the respirable portion of the dust clouds; to the more serious but less frequent hypersensitivity reactions like extrinsic allergic alveolitis due to both the actinomycetes and Aspergillus fumigatus. The aim of this study is twofold. The first part is a quantitative assessment of Gram negative bacteria, their endotoxins, thermophilic actinomycetes and Aspergillus fumigatus at five selected points within the Municipal Solid Waste composting plant at Marsascala as compared to an uncontaminated background point. The second part studies the responses of plant operators to dust and bacterial insults using both a subjective questionnaire and simple lung function tests. Their questionnaire

responses are then compared to an unexposed control group. Statistical analysis are carried out to assess the levels of contaminants within the plant vs the background and the responses of the more exposed employees to their environmental insults. Finally, a brief review is given on suitable protection measures that should be taken to reduce adverse health effects on the employees.