Noncriteria air pollutants are synonymous with hazardous air pollutants (HAPs), air toxics or toxic air pollutants (TAPs). The term noncriteria pollutants refers to all air pollutants except for the criteria pollutants (SOx, PM, NOx, CO, O3, and Pb). Air toxics are pervasive in our environment worldwide in varying degrees. Uses of these chemicals are varied and numerous; their emissions are ubiquitous, and they include organic compounds such as chlorinated hydrocarbons, dioxins, aldehydes, polynuclear aromatic hydrocarbons, and heavy metals such as chromium, nickel, cadmium, and mercury. There are more than 70,000 chemicals that are in use commercially in the United States, and we know relatively little about their ambient concentrations, persistence, transport and transformation as well as their effects on health and the environment, many of which take decades to emerge. The United States Environmental Protection Agency, under the authority of Section 112 of the Clean Air Act, is mandated to regulate any air pollutant which, in the Administrator's judgment, “causes, or contributes to, air pollution which may reasonably be anticipated to result in an increase in serious irreversible or incapacitating reversible illness.” For such regulatory decision-making, EPA's Office of Health and Environmental Assessment (OHEA) provides scientific assessment of health effects for potentially hazardous air pollutants. In accordance with risk assessment guidelines developed by OHEA over the years, Health Assessment Documents (HADs) containing risk assessment information were prepared and were subjected to critical review and careful revision to produce Final Draft HADs which serve as scientific databases for regulatory decision-making by the Office of Air Quality Planning and Standards (OAQPS) in its risk management process. EPA developed databases such as the Integrated Risk Information System (IRIS) and the National Air Toxics Information Clearinghouse (NATICH) and a technical assistance response system called the Air Risk Information Support Center (AIR RISC), in addition, to help in implementation of the National Air Toxics Program by state and local regulators.
Ranking Cancer Risks of Organic Hazardous Air Pollutants in the United States