Recovery of Aspergillus fumigatus aerospora from municipal sewage sludge composting operations in the state of Maine

An investigation was conducted to determine the effect of composting activity on ambient and transient viable Aspergillus fumigatus aerospora at three composting operations (Westbrook, Bangor, Old Town) in the State of Maine. Meteorological conditions and seasonality were also considered. The purpose of the study was to determine whether composting operations caused increased public health risks due to the generation and dispersal of elevated A. fumigatus aerospora concentrations. Ambient aerospora concentrations at the Westbrook facility did not change during the first year of operation, nor did they differ from concentrations recovered before the composting facility was constructed. Ambient aerospora at Bangor and Old Town were also present at background concentrations. Background aerospora concentrations (less than 50 CFU/m3) were determined at control sites. Spatially and temporally restricted increases in transient A. fumigatus aerospora concentrations were observed. The greatest increases (up to 1 X 10(4) CFU/m3) were associated with wood chip manipulation activities. Aerospora concentrations always returned to background levels within 1 hr after the monitored activities ceased. Meteorological conditions which tended to reduce dust concentrations also decreased A. fumigatus aerospora yields. Evidence regarding seasonality as a factor affecting aerospora concentrations was equivocal. The results of the study demonstrated that residents in the vicinity of the Westbrook, Bangor and Old Town composting operations were not exposed to increased concentrations of A. fumigatus aerospora.