A Screening Level Risk Assessment of the Indirect Impacts from the Columbus Waste to Energy Facility in Columbus, Ohio
Testing for emissions of dioxins from the stack of the Columbus, Ohio Waste to Energy (WTE) municipal solid waste combustion facility in 1992 implied that dioxin concentrations in stack gas averaged 328 ng TEQ/m3. The incinerator had been in operation since the early 1980s. In mid-1994, US EPA's Office of Research and Development (ORD) and EPA's Region 5 Office collaborated on a screening risk assessment to evaluate the potential indirect impacts of these emissions. This paper describes this assessment. The exposure setting is a hypothetical dairy farm where individuals on the farm obtain their beef, milk, and vegetables from home sources. A 70-year exposure scenario is considered, which includes 45 years of facility operation, with MACT coming on-line 15 years after the incinerator has been operating, followed by 25 years of impact due to residual soil concentrations. Soil dermal contact, inhalation, and breast milk exposures were also considered for this assessment. The "source" term, or dioxin loadings to this setting, were derived from air dispersion modeling of emissions from the Columbus WTE. A key finding of the assessment was that exposures to dioxin in beef and milk dominated the estimated risks, with excess cancer risk from these two pathways estimated at 2.8*10-4. A second key finding was that over 90% of a lifetime of impact from these two pathways, and the inhalation and vegetable ingestion pathways, has already occurred due to pre-MACT emissions.
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