Human and Ecological Risk Assessment - Earthjustice

Section 4.0Risk CharacterizationModeled 90th and 50th Percentile Risk Results vs.Reported Groundwater Exceedences (continued)ConsistentHuman Cosmetic/2007 Risk Assessment a Damage Cases bConstituent 90th %ile 50th %ileHealthEffects cAestheticEffects dStateStandard eResults as of2007 fZinc Screened – – YesaNot Screened = Constituent was not considered due to lack of health-based benchmarks.Screened = Constituent showed no risk potential in the screening assessment.RAF = Constituent showed risk potential in the screening assessment, and was analyzed with riskattenuation factors.= Constituent underwent full probabilistic modeling and was shown to pose a risk to humanhealth in the landfill scenario, the surface impoundment scenario, or both.– = Constituent underwent full probabilistic modeling and was not shown to pose a risk to humanhealthb = At least one proven damage case showed an exceedence of this constituent.– = No proven damage cases have yet shown an exceedence of this constituent.c = Exceedences of primary maximum contaminant levels (MCLs) or other health-based numberspublished by EPA.d = Exceedences of secondary MCLs, which would not result in harm to human health.e = Exceedences of a relevant state standard.f Yes = Results of risk assessment and damage cases either both indicated a risk to human health orboth indicated no risk to human health.No= The risk assessment indicated risks where none have yet been found in a proven damage case.Uncertain = It is possible that the results were consistent, but due to lack of probabilistic modeling, nodefinitive conclusion can be made.N/A = Constituent was not examined at any stage in the 2007 risk assessment, so it was not possibleto draw any conclusions as to consistency.The first category of constituents is those for which the risk assessment and the damagecases agree, either because both the risk assessment results and the damage cases indicated risks,or because both the risk assessment results and damage cases did not indicate risks. The formergroup had model results exceeding the cancer risk range or an HQ of 1, and also appeared in thedamage cases with exceedances of maximum contaminant levels (MCLs), state groundwaterstandards, or other health-based numbers (arsenic, boron, cadmium, lead, molybdenum, andselenium). The latter group did not show the potential for risks above an HQ of 1 from the riskassessment and did not appear in the damage case literature (aluminum, barium, beryllium,copper, silver, and zinc).The second category of constituents is those for which the risk assessment and thedamage cases did not agree. Four modeled constituents (antimony, cobalt, thallium, andnitrate/nitrite) showed risk at the 90th percentile but no damage cases had been proven as of2007. This could indicate that (1) the risk assessment was conservative for these constituents, (2)not enough time has passed to see the remaining constituents appear in damage cases, (3)corrective action was taken when the first constituent(s) was observed, so further constituentsthat would have appeared at the same site were never seen, or (4) these constituents are nottested for as frequently as the constituents found in the proven damage cases.April 2010–Draft EPA document. 4-24