Overview
Residual risk regulations are laid down in the 1990 Clean Air Act (CAA) Amendments, Section 112(f): Hazardous Air Pollutants – Standard to Protect Health and the Environment.
The 1970 Clean Air Act established National Emission Standards for Hazardous Air Pollutants (NESHAPS) and the EPA was directed to regulate HAPs on a health risk basis. In the following 20 years the EPA listed only eight HAPs and set regulations for only seven.
To address this deficiency, the 1990 Amendments to the Clean Air Act took a totally new approach for regulating HAPs. The Amendments listed 189 HAPs, one of which has since been removed. The EPA is required to identify source categories of hazardous air pollutants and to establish NESHAPS based on the "maximum available control technology" (MACT). NESHAPs are commonly referred to as MACT standards.
After the promulgation of a MACT standard, the EPA has to evaluate remaining risks from HAP emissions for public health and environment. If a residual risk remains, more stringent standards have to be established within 8 years after the MACT standard was released. The residual risk standard should provide an ample margin of safety to protect public health and should prevent adverse environmental effects, taking into consideration costs, energy, safety, and other relevant factors. Standards addressing the residual risk should reduce the lifetime excess cancer risk for the individual most exposed to emissions from a source to less than one in one million.
Within 6 years after the enactment of the 1990 CAA Amendments, the EPA had to prepare a report to Congress on the methods to be used to assess the risk after MACT standards have been promulgated and applied. The "Residual Risk Report to Congress", was completed in March 1999.
Current Situation
To date more than 90 MACT standards have been promulgated by the EPA.
On April 15, 2005, the first final residual risk rule "National Emission Standards for Coke Oven Batteries" was publicized in the Federal Register. Further emission standards for Dry Cleaning, HON, and Halogenated Solvents are expected to follow in 2006.
Residual Risk Determination
To assess residual risk of HAPs, the EPA uses the following steps:
- Assessment of the public's exposure level
- Assessment of type and severity of adverse effects
- Dose-Response Assessment
- Overall Risk Characterization
Links
List of MACT Standards: http://www.epa.gov/ttn/atw/mactfnlalph.html
Residual Risk Standards: http://www.epa.gov/ttn/atw/rrisk/residriskpg.html
Residual Risk Report to Congress |
