Exposure to toxic air contaminants may produce or increase the risk of various adverse health impacts. Potential adverse health impacts include cancer and non-cancer health impacts, and the non-cancer health impacts can be characterized as chronic and acute risks.
South Coast AQMD staff uses the risk assessment health values prepared by the California Office of Environmental Health Hazard Assessment (OEHHA) for regulatory purposes such as risk analysis, rule making, permitting, public notice, and risk reduction. Please note that the health values used by various special-purpose agencies may vary due to particular mandates, guidelines, models, assumptions, and safety considerations. The values may also differ due to differences in scientific opinion or more recent evaluation utilizing more recent literature.
Health Values
The term “health value” specifically references a regulatory threshold used for planning and health risk assessment purposes. Health values are used in the calculations which are the basis of facility risk assessments. The U.S. Environmental Protection Agency (U.S. EPA) develops and adopts health values for risk analysis purposes such as “Cancer Potency” and “Reference Exposure Level” for the entire nation (which includes South Coast AQMD jurisdiction). The Office of Environmental Health Hazard Assessment (OEHHA) develops and adopts health values for risk analysis purposes for the State of California (which includes South Coast AQMD jurisdiction).
South Coast AQMD often employs the health values developed by OEHHA, as they are designed to be equal to or more stringent than those developed by the U.S. EPA. The U.S. EPA and OEHHA employ the best available scientific evidence and rationale (which includes extrapolations, computer simulations, and safety factors) at that point in time to establish health values. Both agencies will occasionally revise their health values as better data become available.
Cancer Potency is an estimated quantitative measure of excess cancer risk (expressed as probability of contracting cancer) to human health resulting from incidental exposure to a certain chemical. Reference Exposure Level is a chemical concentration where no adverse non-cancer risk to human health is expected.
For more information about adverse health effects, please contact AB 2588 Staff.