Framework for assessing risk under the Air Toxics Program

This report describes the general framework the EPA will use to assess any residual public health and environmental risk which may remain after industrial sources have implemented technology-based air toxic regulations required under the Clean Air Act. The report does not have any regulatory consequences.

Under the Clean Air Act Amendments of 1990, Congress required EPA to regulate, by industrial category, major sources of 188 toxic air pollutants (‘major’ is defined by the CAA as those facilities emitting 10 tons/year or more of one pollutant or 25 tons/year or more of a combination of pollutants).

In the initial round of regulation under the Act, EPA air toxics standards have been technology-based; the limits must reflect maximum achievable control technology (MACT), meaning newly-regulated sources must control emissions as well as the cleanest facilities in the US.

However, Congress also required EPA to assess any residual risk remaining after facilities have implemented the MACT technology-based standards.

If necessary, EPA must issue additional regulations to reduce any residual threats to the public and environment, taking into consideration costs, energy, safety and other relevant factors. If additional regulations are needed for a particular industry, EPA must issue them within eight years after setting the technology-based standards for that same industry. The first of these additional regulations would be due in 2001.

The report does not speculate on which industries might be subject to residual risk controls; its main purpose is to describe the methods and the framework that EPA will use to make residual risk determinations. The report also discusses, in general terms, the available methods of reducing residual risks – including pollution prevention, add-on controls, and voluntary approaches – and factors relevant to costs of these methods; the current state of knowledge regarding health effects of air toxics on humans; and the EPA’s current methods for collecting and assessing health effects data.

The study does not specify a particular method for conducting risk assessments, stressing that the EPA has the flexibility to use current techniques along with new methods as they are developed.

The report also states that the Clean Air Act gives the EPA adequate authority to address any residual risk and provides a comprehensive and flexible strategy for addressing a variety of air toxic concerns. Therefore, the Agency is not recommending any legislative changes.