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Detection of Aerosolized Endotoxin from a Land Application of Biosolids Site

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Throughout the United States, it has been estimated that approximately 6.5 million tons of biosolids are produced and that 60% of this is land applied. Class B biosolids are land applied in locations typically devoid of communities, but as populations increase and the line between urban and suburban areas begin to blur, biosolids land application is increasingly coming into contact with neighboring communities. Endotoxin (Gram-negative bacteria derived lipopolysaccharide) has been associated with pulmonary ailments, asthma, and fever depending on length of exposure and susceptibility. Aerosol samples were collected from sites in southeastern Arizona from biosolids land application sites. Three SKC Biosamplers were utilized simultaneously, operating at an airflow rate of 12.5 L/min for duration of 10 minutes. Samples were collected at multiple downwind distances either from “loading”, “slinging”, or “total operation” procedures. All were assayed utilizing the commercially available Limulus amebocyte lysate assay. Aerosol samples collected downwind from biosolids loading situations consistently averaged endotoxin concentrations less than half of the maximum recommended endotoxin air concentration, 0.1 μg/m3 as suggested by other studies. These levels were similar to endotoxin concentrations during tractor operation on a dry field. At distances greater than 10m downwind of the point source (land application operations), levels of endotoxin began to decrease, approaching background levels beyond 100 m. Biosolids slinging samples contained aerosol endotoxin concentrations greater than background levels, but were significantly less than loading samples. Overall the amount of endotoxin aerosolized during biosolids operations was below recommended occupational exposure levels for indoor environments, and decreased to background levels beyond 100 m, thus occupational exposure is of greatest concern. When compared to concentrations of aerosolized indicator microorganisms, and subsequently assumed concentrations of pathogens detected at biosolids application sites, endotoxin may be of greater concern to the occupationally exposed.

Document Type: Research Article


Publication date: 2005-01-01

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