CHEMICAL PROFILES|Risk Assessment Value Availability

In assessing the availability of risk assessment values that could be used for safety assessment, Scorecard counts all risk assessment values that have undergone sufficient scientific or administrative review to be used in regulatory risk assessments by either state or federal agencies. Scorecard's complete set of risk assessment values are compiled from both EPA and other federal agencies (such as ATSDR), as well as state agencies. EPA risk assessment values are compiled from four major agency databases: the Integrated Risk Information System, the Health Effects Assessment Summary Tables, the Office of Pesticide Programs Reference Dose and Cancer Potency tracking systems, and the Superfund Chemical Data Matrix. Only one state, California, has made a major contribution to the development of risk assessment values for toxic chemicals.

Note that risk assessment values are calculated for specific exposure routes (ingestion and inhalation). In evaluating whether a safety assessment can be conducted for a chemical, Scorecard requires inhalation risk assessment values for air exposures and ingestion risk assessment values for water exposures.

Scorecard assumes its complete set of risk assessment values are available for assessing chemical safety anywhere in the U.S., even though many values have only been officially adopted in California (or by a specific regulatory agency). Many of Scorecard's RAVs are not available nationally to support safety assessment or risk regulation by U.S. EPA (or other state governments). This assumption results in an overstatement of the availability of toxicity data in the regulatory arena, and thus an understatement of the degree of ignorance about exposures to the chemical in question.

In some cases, chemicals lack risk assessment values but possess national media quality standards. These standards define legally allowable levels of chemical contamination in various media, such as air or water. National standards are established by the EPA pursuant to the mandate of federal environmental statutes, and can be based on a variety of criteria, including health risks, economic costs and technological feasibility. While most national standards are based on EPA risk assessment values, some are not. Lead, for example, has a national ambient air quality standard, but no inhalation reference concentration, and a maximum contaminant level in drinking water, but no ingestion reference dose.

In its profiles of safety data availability, Scorecard assumes that the existence of a national standard provides the ability to conduct a safety assessment on a chemical for unspecified health effects if exposed via the relevant media (i.e., an air standard supports safety assessment of inhalation exposures). However, such standards do not support assessments of cancer risks or developmental or reproductive toxicity risk. This is because national standards that are not based on risk assessment values cannot be used to characterize risks at different exposure levels, and have generally not been derived to protect against these specific health effects.

In assessing the availability of media quality standards, state standards for chemicals were not included. This is because such standards are not applicable nationally, are generally unavailable via electronic sources, and are usually not derived from risk assessment values. Some states, for example Texas and Michigan, have large numbers of screening guidelines that they use in air toxics permitting processes, but such standards are usually based on the application of an arbitrary factor to occupational exposure guidelines, which are rarely protective of human health.

Scorecard does not consider workplace exposure standards or guidelines to be scientifically defensible risk assessment values. Neither Permissible Exposure Limits (PELs) (developed by the Occupational Safety and Health Administration) nor Threshold Limit Values (TLVs)(developed by the American Conference of Governmental Industrial Hygienists) define safe levels of exposure based on analyses of animal or human toxicity data. PELs and TLVs are exposure limits that are primarily based on considerations of economic cost and technical feasibility. While some states have divided workplace limits by uncertainty factors to derive community exposure guidelines, these values are generally not scientifically defensible. More on the limits of occupational exposure guidelines.