ARCHIVED REPORTS XR0000211 - Laserfiche WebLink

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SECT10MSIX Risk Chazoot®zizotioE waste sites Current EPA guidance, however, states that where the cumulative site risk to an individual based on reasonable maximum exposure is less that 1 x 10'4, remedial action is generally not warranted (EPA, 1991c) EPA guidance to evaluate cancer risk from simultaneous exposure to several carcinogens assumes that incremental cancer risks are additive The concept that cancer risks are additive is based on a number of assumptions If these assumptions are incorrect, over-or under-estimation of the actual nsk could result (EPA., 1989b) The total cancer risk is estimated by summing the risk estimated for each chemical of concern and for each pathway 6.3 RISK CHARACTERIZATION RESULTS Chemical-specific, pathway specific, and cumulative carcinogenic risks and noncarcinogeiuc Hazard Indexes "s) were calculated for each exposure scenario evaluated in the risk assessment Results of the risk characterization are discussed in the sections below Table 6-1 and Table 6-2 summarizes carcinogenic risk and Table 6-3 and Table 6-4 summarizes noncarcnnogennc risks 6.3.1 Carcinogenic Risk USEPA has established a target cancer risk range of 1E-06 to 1E-04 (1 in 1,000,000 to 1 in 10,000) for evaluating the need for remedial action to protect public health from exposure to releases of hazardous chemicals EPA guidance states that if the cumulative cancer risk does not exceed 1E-04, and noncarcinogenic effects are not of concern, then remedial action is generally not warranted to protect public health(EPA,199 1) Review of the cancer risk results summarized in Table 6-1 shows that the estimated cumulative cancer risk for all receptors did not exceed the EPA target risk range Review of the cancer risk estimates for current and future occupational employees were within the EPA target risk range using all ' groundwater data evaluations(Tables 3-3 through 3-7) The pathways with the highest risk were from ingestion of soil, dermal exposure, and outdoor air inhalation which assume that the concrete and ' asphalt paving are not present The pathway with the lowest carcinogenic risk was groundwater ingestion at the hypothetical wells located at 500 feet and 1,000 feet downgradient of the site This assumption assumed that the wells would be the only source of groundwater for 30 years and 2 liters per day would be ingested The total residential carcinogenic risks which included groundwater ingestion and outdoor air inhalation for adult and child residents were all significantly below the EPA target risk range When it was assumed that the resident was located 500 feet downgradient in both the wind and groundwater ' direction, the highest carcinogenic risk was 2 4E-08 The pathway that had the highest contribution to � ° ® T%19en9r3WgNAZTOCKTON%REPOR7%.VHOREPOI D0CWFEE�.9wa73o0BNAW4A 6-3