ABSTRACT
Most environmental problems that concern the public deal with exposures to toxic chemicals (by inhaling air, by ingestion of water or food, or by dermal exposure) originating from chemical or other industries, power plants, road vehicles, agriculture, etc. There are two types of noncancer chemical risk analysis uses: (1) to derive criteria and standards for various environmental media and (2) to characterize risks posed by a specific exposure scenario (e.g., at the Superfund site by drinking contaminated water; by consuming contaminated food; by performing some manufacturing operations; by accidental or deliberate spill or release of chemicals, etc.). Usually such exposure scenarios are complex and vary with each individual case, and, thus, methods in risk analysis must be modified to account for all possible exposures in a given situation.
Chemical risk analysis used for criteria development generally does not determine the probability of an adverse effect. Rather, it establishes concentrations of chemicals that could be tolerated by most people in our food, water, or air without experiencing adverse health effects either in short-term or long-term exposures (depending on the type of a derived criterion). These levels (either concentrations of chemicals in environmental media or total intake of a chemical by one or all routes of exposure) are derived by using point estimates of the average consumption of food and drink and body parameters such as weight, skin surface, metabolic rate, etc. Risk analysis is then applied to derive “criteria” for particular pollutants, 14which are then modified by risk management considerations to derive standards. There are numerous criteria and standards established for various chemicals by the U.S. Environmental Protection Agency (EPA), the U.S. Food and Drug Administration (FDA), the National Institute for Occupational Safety and Health (NIOSH), and the Occupational Safety and Health Administration (OSHA). Since many of them were established before formal risk analysis techniques became available, they are undergoing revision, based on better risk analysis methods. For a particular pollution situation, one can measure or estimate exposures to a contaminant and compare them to the previously established criteria and/or standards. The likelihood of harm increases if the exposure levels exceed the derived “safe” levels. The exposure assessments could follow a deterministic model by assuming average parameter values (air, water, food consumptions, dermal intake, etc.) or could follow the Monte Carlo method, which uses real-world distribution data on various exposures, thus potentially giving more accurate and informative estimates of risk.
