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Bioaerosol concentrations were investigated in a totally indoor composting facility processing fermentable household and green wastes to assess their variability. Stationary samples were collected by filtration close to specific composting operations and then were analysed for cultivable mesophilic bacteria, thermophilic bacteria, mesophilic fungi, thermophilic fungi, endotoxins and total airborne bacteria (DAPI-staining). Indoor concentrations exceeded the background levels, between 500 and 5400 EU m(-3) for endotoxins, 10(4) and 10(6) CFU m(-3) for cultivable bacteria and generally below 10(5) CFU m(-3) for airborne cultivable fungi. No significant (p > 0.05) differences were observed between the indoor composting operations. Successive 30 minute bioaerosol samples were collected to investigate the variation of cultivable mesophilic microorganisms over the work shift. Concentrations of mesophilic bacteria and fungi varied up to 1 log unit depending on the time at which they were collected in the day. Total airborne particles, counted using an optical particle counter, were present at up to 10(8) particles m(-3) and several concentration peaks were noted. Values for total airborne bacteria were roughly 70-fold higher than cultivable bacteria. These results raise the question of the sampling strategy (duration of sampling; number of samples to be collected) used in similar studies. They provide new bioaerosol concentration data in a composting facility and suggest that the filtration sampling method might be a useful tool for exposure measurements in that occupational environment.

The presence of actinomycetes in many workplaces and their role in the incidence of various respiratory symptoms remains poorly understood and underestimated. A sampling and cultureindependent analysis method to measure airborne actinomycetes has yet to be developed and controlled bioaerosols are needed for laboratory investigations. In this article, the performances of a single-pass bubbling aerosolizer were characterized to evaluate the feasibility of generating actinomycetes from a liquid source and to confirm that viability of aerosolized entities was preserved. Six preparation protocols for liquid Thermoactinomycetes vulgaris cultures were compared in terms of culturable flora and total spores concentrations (culture and epifluorescence microscopy) and size distributions (optical counter and cascade impactor) of the bioaerosols generated. Using the best protocol, the generator's performances were then validated using three species: Thermoactinomyces vulgaris, Thermobifida fusca, and Streptomyces californicus. Bioaerosols contained a mixture of spores and mycelium and their properties were stable throughout generation (120 min) and were satisfactorily reproducible between runs. Depending on the species generated, the culturable concentrations measured were between 10 4 and 10 8 CFU.m −3 , with corresponding total spore concentrations between 10 5 and 10 9 Spores.m −3. These concentrations cover the ranges measured in the workplace. The generator's flexibility should make it possible to produce bioaerosols with other actinomycetes species, and use them in laboratory trials with various objectives and constraints.

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