Introduction: In the past decade, we studied occupational bioaerosol exposures in various sites of the waste management chain. In this paper we present an overview of exposure levels of inhalable dust, endotoxin, beta(1 -> 3)-glucan (known or probable inducers of airways inflammation), and extracellular polysaccharide antigens of Aspergillus and Penicillium species (EPS-Pen/Asp; a common and probably more specific marker of fungal exposure). Methods: Over 450 personal bioaerosol samples were taken. Mixed regression analyses were performed to estimate exposure determinants, between- and within-worker variance of exposure, and determinants of these variances. Furthermore, we explored whether the type of waste affected the bioaerosol composition of the dust. Results: Endotoxin and glucan exposure levels were relatively low and comparable for waste collection and transferral, green waste composting and use of biomass in power plants. Exposure levels were 5-20 times higher in domestic waste transferral with sorting, and composting of both domestic and domestic and green waste (similar to 300-1000 EU m(-3) for endotoxin, and 5-10 mu g m(-3) for glucan). Observed exposure exceeded Dutch occupational exposure limits at all sites. EPS-Pen/Asp exposure was detected in 20% of waste collectors and 49% of compost workers. Exposure variability within tasks was large (geometric standard deviation > 2), with smaller between-worker than within-worker variance. Type of company and waste largely explained between-worker variance (40-90%), although within companies no major task-related determinants could be established. Markers of exposure correlated moderately to strongly. Relative endotoxin and glucan content in the dust was only weakly associated with handled waste. Conclusions: Occupational bioaerosol exposure in the waste management chain is lowest for outdoor handling of waste and highest when waste is handled indoors. However, exposure variability is large, with greater within-worker than between-worker variance. Occupational exposure limits for organic dust and endotoxins are frequently exceeded, suggesting workers are at risk of developing adverse health effects.
