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PETITIONED PUBLIC HEALTH ASSESSMENT
CABOT-WROUGHT PRODUCTS - DIVISION OF CABOT CORPORATION
(a/k/a NGK METALS/CABOT BERYLCO, INCORPORATED)
MUHLENBERG, BERKS COUNTY, PENNSYLVANIA


APPENDIX C

Comparison Values

Comparison values for ATSDR public health assessments are media-specific concentrations used to select contaminants for further evaluation. Comparison values are not thresholds of toxicity; therefore, it does not necessarily follow that adverse health effects will occur when environmental concentrations exceed comparison values. These values are used in the preliminary identification of contaminants of concern at a site. The probability of adverse health outcomes will depend on site-specific conditions that affect the route and duration of actual exposure, and not on environmental concentrations alone. Comparison values used in the Environmental Contamination and Other Hazards and the Public Health Implications sections of this petitioned public health assessment are listed and described.

    CREG    = Cancer Risk Evaluation Guides
    EMEG    = Environmental Media Evaluation Guides
    EPAIII    = EPA Region III
    IEMEG    = Intermediate Environmental Media Evaluation Guides
    LTHA    = Drinking Water Lifetime Health Advisory
    MCL    = Maximum Contaminant Level
    MCLA    = Maximum Contaminant Level Action
    MRL    = Minimal Risk Level
    RfD    = Reference Dose
    RMEG    = Reference Dose Media Evaluation Guide
    PEL    = Permissible Exposure Limit

Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations expected to cause no more than one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors.

Environmental Media Evaluation Guides (EMEGs) are calculated from ATSDR minimal risk levels; they factor in body weight and ingestion rates.

Environmental Protection Agency Region III (EPAIII) are risk-based concentrations which take into account factors such as body weight, toxicity, and exposure duration and frequency for non-carcinogens and carcinogens, when applicable.

Intermediate Environmental Media Evaluation Guides (IEMEG) are calculated from ATSDR minimal risk levels; they factor in body weight and ingestion rates for intermediate exposures (greater than 14 day and less than 1 year).

Lifetime Health Advisories (LTHAs) are contaminant concentrations that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day.

Maximum Contaminant Levels (MCLs) represent contaminant concentrations in drinking water that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day (for an adult).

Maximum Contaminant Level Action (MCLA) are action levels set by EPA under Superfund that trigger a response or action when contaminant concentration exceed this value.

Minimal Risk Levels (MRL) are estimates of daily human exposure to a chemical (in mg/kg/day) likely to occur without an appreciable risk of deleterious effects (noncancer) over a specified duration of exposure. MRLs are calculated using data from human and animal studies and are reported for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures. MRLs are published in ATSDR Toxicological Profiles for specific chemicals.

EPA's Reference Dose (RfD) is an estimate of the daily exposure to a contaminant unlikely to cause adverse health effects. However, RfDs do not consider cancer effects.

Reference Dose Media Evaluation Guide (RMEG) is a concentration derived from an EPA reference dose with assumed body and ingestion rates factored into the calculation.

The Occupational Safety and Health Administration's Permissible Exposure Limit (PEL) for air is an 8-hour, time-weighted average developed for the workplace. The level of exposure may be exceeded (for brief periods), but the sum of the exposure levels averaged over 8 hours must not exceed the limit.


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