Spatial and temporal variation of endotoxin concentrations at composting facilities in one of the largest solid waste management facilities in the Middle East

Abstract

Composting activities at open-air facilities can be a source of contaminants including bioaerosols. Exposure to bioaerosols and their constituents can have a potential impact on those involved in waste management and those living in the vicinity of such facilities. This study aims to investigate the temporal and spatial variation in endotoxin concentrations as a biohazard at waste composting facilities in one of the largest municipal solid waste management complexes in the Middle East. The total suspended solids (TSP) and airborne endotoxin were collected by the active method using a pump with an airflow rate of 2 L/min, and 37-mm glass fiber filters. TSP was determined by gravimetry, and then extraction was done in pyrogen-free containers by adding 0.05% Tween 20 in 10 ml of PFW (Pyrogen Free Water), and the endotoxin concentration was determined by the Limulus amebocyte lysate (LAL) method. The results showed high concentrations of endotoxins in composting processes. The highest mean concentrations of ambient air TSP were found in granulation sites (2937 µg/m3) and preprocessing halls (998 µg/m3) and the lowest in the windrow sites (302 µg/m3). The average concentration of endotoxin in the ambient air of granulation, pre-processing and post-processing sites were 48.3, 17.8, and 10.6 times the mean concentrations in the windrow sites, respectively. A significant difference was found in endotoxin and TSP levels between five locations (P = 0.001 and 0.008 respectively), and spatial variation was observed in this study. A good correlation was observed between reported endotoxin concentration and airborne dust (r = 0.797) in composting plant. The evidence provided by this study will help the operators of facilities to be aware of the pollution of different locations involved in composting, and regulators to focus on improving risk assessments at these facilities and also take precautions where a high level of contaminants is reported.