Assessing and managing worker's exposures to bioaerosols during the treatment of organic waste (20m Lecture)

Background: Workers exposures to bioaerosols and the potential health implications arising from these exposures are poorly characterized in the organic waste sector. As compost emissions comprise of biological agents that may cause occupational asthma, employees’ exposure should be prevented or reduces ‘so far as is reasonably practicable’. Consequently the effective use and maintenance of control measures that reduce operator’s exposures are of key importance in reducing the potential risk of occupational illness in this sector. This paper presents research findings that characterize employee exposure levels to dust and endotoxin and discusses risk mitigation measures that reduce employee exposure levels in accordance with the legal framework.
 
Methods: Personal exposure levels to inhalable dust and endotoxin was assessed at four large-scale composting facilities to determine task-related exposure data that would inform the development of evidence-based risk control measures. Furthermore, vehicle operators’ exposure levels were investigated to determine the impact that cab cleaning and maintenance of the vehicle filtration system had on operator exposure levels.
Inhalable dust fractions were determined by gravimetric analysis in accordance with MDHS 14/3 (HSE, 2000) using IOM Inhalable samplers. Endotoxin levels were determined using Limulus Amebocyte Lysate assay (LAL) (Wouters, 2005, HSE, 2007).
 
Findings: Employees exposure to dust was generally low (GM 0.99 mg/m3, GSD 2.99 mg/m3, n=117), however endotoxin concentrations were elevated (GM 35.10 EU/m3, GSD 9.97 EU/m3, n=117). A third of all samples taken exceeded the 90 EU/m3 occupational exposure limit recently adopted in the Netherlands (DECOS, 2010). Any activities involving the movement of waste gave rise to high peak exposure levels.
Vehicle operator exposures to endotoxin were consistently high despite working in air conditioned cabs with vehicle filtration systems fitted. The cleaning and maintenance of vehicle cabs had a significant reduction on operators’ exposure (p<0.05, 2 sample t-test) but these improvements were not maintained.
 
Conclusions: Multifaceted controls are needed to reduce employee exposures to as low as reasonably practicable in accordance with the legal framework. Consideration should be given to vehicle cab cleaning and maintenance, zoning of high exposure areas and high risk activities, health surveillance and provision of appropriate RPE.