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Title: Risk of infection related to biological aerosols from Class A and B biosolid practices

item Brooks, John

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/13/2007
Publication Date: 10/13/2007
Citation: Brooks, J.P. 2007. Risk of Infection Related to Biological Aerosols from Class A and B Biosolid Practices [abstract]. Proceedings Water Environment Research Conference. #W203.

Interpretive Summary:

Technical Abstract: Biosolids land application can involve risks of infection associated with biological aerosols (bioaerosols) generated during the application process. These risks can be from biosolids-borne pathogenic bacteria or viruses. A series of studies were conducted since 2001 involving biosolids land application(s) operations across the country to quantify the risks associated with them. It was concluded that, depending on conditions, biosolids land application can generate biological aerosol concentrations as high as 109 CFU (colony forming unit) per m3. It appeared that these concentrations were due more to the onsite soil particulate aerosolization, than the biosolids particles. From these results, an empirically designed transport model was created to extrapolate off-site transport of these microorganisms, and determine risk of infection to the surrounding populations. Off-site risk of infection was determined using transport of surrogate microorganisms (Escherichia coli, coliphage) to model the transport of the more difficult to detect pathogenic microorganisms. Annual risks of infection associated with Class B biosolids land application ranged from 10-4 to below 10-10 for the general populace, however biosolids-handlers were exposed to greater concentrations and exposure times, thus their risk ranged from 10-1 to below 10-2 on an annual basis. Class A biosolids operations were also studied, and were determined to be safe provided that the biosolids were protected from rain, preventing any regrowth of pathogenic populations. If a regrowth event were to have occurred, it was hypothesized that concentrations of any one pathogenic bacteria could reach as high as 106 cfu per g, and thus could pose a risk of aerosol infection if land applied. Overall biosolids land application operations were concluded to be safe with regard to risk of infection to the general populace provided that adequate land buffers were in place and that the biosolids were kept from re-wetting. It is recommended that biosolids workers wear appropriate protective equipment such as gloves and respiratory masks, while also practicing simple hygienic measures.