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INITIAL RELEASE DDJC Tracy <br /> APPENDIX B: Comparison Values <br /> The conclusion that a contaminant exceeds the comparison value does not mean that it will cause <br /> adverse health effects, rather they represent media specific contaminant concentrations that are <br /> used to select contaminants for further evaluation to determine the possibility of adverse public <br /> health effects. <br /> Cancer Risk Evaluation Guides (CREGs) <br /> CREGS are estimated contaminant concentrations that would be expected to cause no more than <br /> one excess cancer in a million (10') persons exposed over lifetime. ATSDR's CREGs are <br /> calculated from EPA's cancer potency factors (CPFs). <br /> Environmental Media Evaluation Guides (EMEGs) <br /> EMEGs are based on ATSDR minimal risk levels (1vIRLs) and factors in body weight and <br /> ingestion rates. An EMEG is an estimate of daily human exposure to a chemical (in mg/kg/day) <br /> that is likely to be without noncarcinogenic health effects over a specified duration of exposure to <br /> include acute, intermediate, and chronic exposures. <br /> Maximum Contaminant Level (MCL) <br /> The MCL is the drinking water standard established by EPA. It is the maximum permissible level <br /> of a contaminant in water that is delivered to the free-flowing outlet. MCLS are considered <br /> protective of public health over a lifetime (70 years) for individuals consuming 2 liters of water <br /> per day. <br /> Reference Media Evaluation Guides (RMEGs) <br /> ATSDR derives RMEGs from EPA's oral reference doses. The RMEG represents the <br /> concentration in water or soil at which daily human exposure is unlikely to result in adverse <br /> noncarcinogenic effects. <br /> B-1 <br />