Workers' exposure to dust, endotoxin and β-(1-3) glucan at four large-scale composting facilities.

Objectives: To characterise compost workers' exposure to dust, endotoxin and β-(1-3) glucan during various operational practices and investigate whether dust concentrations are a useful indicator of endotoxin exposure in compost workers.

Methods: This study assessed inhalable dust fractions, bacterial endotoxin and β-(1-3) glucan in 117 personal samples and 88 ambient samples from four large-scale composting facilities.

Results: Employees' exposures to inhalable dust, endotoxin and β-(1-3) glucan exhibited a large range. Inhalable dust was found to be generally low (GM 0.99 mg/m(3), GSD 2.99 mg/m(3)). Analysis of the biological component of the dust showed that employees' exposures to endotoxin were elevated (GM 35.10 EU/m(3), GSD 9.97 EU/m(3)). Employees' exposure to β-(1-3) glucan was low (GM 0.98 ng/m(3), GSD 13.39 ng/m(3)). Dust levels were elevated during manual sorting and screening of waste and high levels of endotoxin and β-(1-3) glucan were observed during all practices involving the movement of waste. A significant correlation was observed between the personal dust levels and personal endotoxin concentrations (r=0.783, p<0.05) and that personal inhalable dust concentration may be a valuable predictor for personal endotoxin concentration in the sites studied.

Conclusions: Workers at composting sites are exposed to high levels of bacterial endotoxin consistent with adverse respiratory outcomes even though in most cases, their personal dust exposure is below the suggested regulatory levels. Dose-response data for the biological components present in the dust encountered at composting sites are not well established at this time and site operators should adopt precautionary measures when assessing and managing these potential risks.