Comparative investigations of airborne culturable microorganisms in selected waste treatment facilities and in neighbouring residential areas

The evaluation of airborne microorganisms in waste treatment facilities is complicated by different measuring systems, a lack of measuring standards a nd large variations between individual counts. In the present study, differ ent sectors of the waste management industry were compared by determining m edian values of airborne culturable microorganisms from numerous parallel c ounts over a prolonged time period. The samples were taken during the warm season using the six-stage Andersen volumetric sampler in a large compostin g plant and its immediate vicinity, in an agricultural composting plant, a waste disposal site, and a sorting facility for recyclable materials. Contr ol samples were taken at a site not influenced by the waste management indu stry in an open and largely uninhabited area. The highest median values for culturable bacteria (37 degrees C) found were 1,1 x 10(5) CFU/m(3), for mo ulds (25 degrees C) 1,4 x 10(4) CFU/m(3), and for A. fumigatus (37 degrees C) 1,7 x 10(4) CFU/m(3) in the sorting cabins of the sorting facility (p < 0.001). The highest median values for thermophilic bacteria (actinomycetes and bacillaceae, 50 degrees C) were 7,3 x 10(3) CFU/m(3) in the large compo sting facility. In all other facilities as well as in the neighbouring resi dential areas of all facilities investigated, all median values were signif icantly lower and corresponded to the naturally occurring levels: approx. 1 0(2) CFU/m(3) for bacteria, approx. 103 CFU/m(3) for moulds and approx. 10( 1) CFU/m(3) for A. fumigatus and thermophilic bacteria. Only in the neighbo uring residential area of the large composting plant, the median values for thermophilic bacteria were approx. 10(2) CFU/m(3), but an additional impac t from Farms cannot be excluded in this case. These results show permanent increased loads of the investigated microorganisms inside large composting facilities and especially in the sorting cabins for recyclable materials. T he increasing number of reports on potential health hazards in these areas require adequate measures on the part of occupational medicine in order to limit the health risk to a minimum. The most important task is the automati zation of the sorting process for recyclable materials.