DETERMINATION OF ATMOSPHERIC WORKPLACE CO NCENTRATIONS OF BIOLOGICAL AGENTS - FIRST INTERLABORATORY TRIAL MOLDS

Biological agents (moulds, bacteria etc.) can be found at many workpla ces, e.g. in the waste industry or where cooling lubricants are used. Standardised measuring methods are indispensable for ensuring a harmon ised evaluation of microbiological workplace exposure. The first inter laboratory trial was intended to gather information on the efficiency of the ''Method for determining mould/yeast concentrations in workplac e air''. Coordinated by the Berufsgenossenschaftliches Institut fur Ar beitssicherheit - BIA, the trial was carried out by the project group 4 ''Workplace assessment'' (former task force ''Measuring methods, mea suring strategy'') of the Committee for Biological Agents at Work. The method includes sampling with separation on a membrane filter and det ermination after culturing on nutrient media. A total of eight institu tions participated in the interlaboratory trial. Samples were taken in a composting plant, both outdoors near the entrance of the administra tion building (Direct method) and indoors in the sorting cabin, where organic waste is prepared for composting (Indirect method). The sampli ng method made its proof under the given sampling conditions. If outli ers (highest and lowest individual value) are excluded, mould concentr ation values determined in one filter series vary by the factor simila r to 2 as far as the Indirect method is concerned. The relative standa rd deviation comes to 30 to 41% for DG-18-Agar and 45 to 48% for MEA. Variance of values is not only due to laboratory conditions, but also to heterogeneous spore distribution at the sampling place. Compared to other approaches (e.g. impaction), the investigated sampling system o ffers several advantages: determination of the inhalable fraction, per sonal sampling, quantitative determination of high mould concentration s with long sampling times and variable preparation of loaded filters (direct, indirect). On account of the results obtained in exhaustive m easuring series and in the described interlaboratory trial, a revised version of the measuring protocol was elaborated. Further interlaborat ory trials (moulds, bacteria) are planned.