Evaluation of Bioaerosols in a Municipal Solid Waste Recycling and Composting Plant

Abstract

Both the processing of solid waste and the composting of organic matter generate airborne biological contaminants. For this type of environment, some authors have proposed Threshold Limit Values (TLV) of 10,000 Colony Forming Units per cubic meter (CFU/m³) of air for total bacteria, and 1,000 CFU/m³ of air for Gram-negative bacteria. Endotoxins produced by Gram-negative bacteria can cause fever and respiratory problems. Diarrhea and gastrointestinal problems can also be caused by Gram-negative bacteria. Other researchers have found Aspergillus fumigatus, which is considered an opportunistic pathogenic fungus, in the nose and throat of people exposed to compost. The objectives of this study were to evaluate the microbiological content of indoor and outdoor air, to detect concentrations of total and Gram-negative bacteria exceeding their proposed TLV, and to suggest corrective measures based on the technical and scientific literature. Air sampling was carried out twice in one day using Andersen samplers. The culture media used were trypticase soya agar for total bacteria, MacConkey for Gram-negative bacteria, and Sabouraud dextrose agar for the fungi. In at least one sample from each work station, the air concentrations of total bacteria exceeded 10,000 CFU/m³. The air concentrations of Gram-negative bacteria were above 1,000 CFU/m³ of air at six of the nine work stations. Indoor concentrations of fungi exceeded outdoor concentrations at eight of the nine work stations studied. To reduce exposure to biological contaminants, it is suggested that ventilation be modified in the separating area, and protective and hygienic measures be initiated at the other work stations.