Residual Risk Assessment and Standards for Hazardous Air Pollutants

2. Section 112(f) Background • The 1970 CAA mandated a health-based program that required EPA to identify and list HAPs based on human health criteria. • USEPA was to promulgate standards

3. (national emission standards for hazardous air pollutants, or NESHAPs) for each pollutant at a level that would ensure the protection of public health with “an ample margin of safety.”

4. In the 20 years following enactment of the 1970 legislation, USEPA identified eight pollutants as HAPs and regulated sources of seven of them. • USEPA was to promulgate standards

5. that shifted the focus from individual pollutants to industrial and commercial source categories, and a phased approach to controlling air toxics emissions was developed.

6. The fundamental approach is the use of available control technologies or work practice changes to achieve emission reductions in a timely manner for as many of the listed HAPs as possible, without

7. explicit consideration of a HAP’s inherent toxicity and potential risk. This technology-based program is commonly referred to as the maximum achievable control technology (MACT) program.

8. In the 13 years following the enactment of the 1990 legislation, USEPA has identified 188 HAPs and regulated 174 source categories and sub-categories that are sources of the listed HAPs.

9. In the first regulatory phase, EPA must promulgate national, technology-based emission standards for source categories emitting any of the 188 currently listed HAPs in amounts exceeding specific

10. emission thresholds. • As of August 2003, 174 source categories and sub-categories have been subjected to MACT standards, resulting in estimated emission reductions of more than

11. 1.5 million tons of HAPs per year. • The implementation of the MACT standards also results in significant reductions in emissions of criteria pollutants through co-control.

13. Section 112(f) Overview • Section 112(f) of the Clean Air Act (CAA), as amended, directs USEPA to prepare the residual risk after control technology standards applicable to emission sources

14. of hazardous air pollutants (HAPs) have been promulgated and applied. • USEPA shall determine the necessity to promulgate residual risk standards, and shall promulgate the standards 8 years

15. after promulgation of the original MACT standards for each source category or subcategory concerned. • The USEPA issued the Residual Risk Report in 1999 that presents a discussion of its

16. residual risk assessment framework for addressing the requirements under section 112(f)(2) to promulgate standards, if required, and “toprovide an ample margin of safety to protect public health” or to set

17. more stringent standards, if necessary, to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect.” • USEPA ecological risk assessment methods

18. are also described in the Report. • USEPA is expected to provide Industry and the States/Locals/Tribes with a protocol for performing risk assessment under 40 CFR Part 63 by the Fall of 2003.

20. Return to a Risked-based Format • In the second regulatory phase, the 1990 Amendments provide for a human health risk-and adverse environmental effects-based “needs test.”

21. In this phase, referred to as residual risk standard setting, USEPA will consider the need for additional standards following regulation under section 112(d) to protect public health and the environment.

22. Section 112(f) of the CAA specifies that such residual risk standards “provide an ample margin of safety to protect public health.” • Section 112(f) also requires USEPA to

23. determine whether residual risk standards are necessary to prevent “an adverse environmental effect,” taking into consideration “costs, energy, safety, and other relevant factors” in deciding what

24. level is protective. There is uncertainty and variability in the estimation of residual risks. The Agency has published several guidance documents addressing this issue, which will be used to guide each analysis.

25. While the exact approach to be taken has not been finalized and may differ from source category to source category, a number of general approaches will be considered for addressing uncertainty and

26. variability in residual risk assessments, including: (1) qualitative assessment; (2) multi-scenario approaches and limited sensitivity analysis;

27. (3) systematic sensitivity analysis; and, (4) Monte Carlo simulation and related probabilistic methods.

28. EPA intends, as part of the section 112(f) standard-setting process, to the extent feasible, to identify potential negative health and environmental consequences and consider the risk-risk tradeoffs

29. associated with any standards established under the residual risk program. Where deemed necessary, USEPA will conduct analyses of these trade-offs and provide appropriate level of detail.

31. Residual Risk Status & Process • Initially, USEPA plans to set priorities for analyzing the more than 170 source categories based on a number of considerations, including any available

32. information bearing on the relative level of residual risks attributable to various source categories. • The purpose of a screening analysis is to identify those situations or HAPS for which

33. no further action is needed and those for which further analysis is needed. • USEPA has published a list of current findings; these are:

34. PERC Dry Cleaning: • not low risk; proposal by 12/04 • Magnetic Tape: • expect low risk

35. Halogenated Solvents: • not low risk; past due (12/02) • Wood Furniture: • pending

36. Ship Building: • not low risk; proposal by 12/03 • Printing/Publishing: • pending; proposal 05/04;

37. Coke Ovens: • not low risk; proposal 8/03 • Secondary Lead: • not low risk; past due (06/03)

38. IP Cooling Towers: • low risk • Chrome Electroplating: • low risk

39. HON: • not low risk; passed due (04/04) • Polymers & Resins II: • expect low risk

40. Polymers & Resins I: • not low risk; proposal 09/04 • EO Sterilizers: • not low risk; past due (12/02)

41. Polymers & Resins IV: • not low risk; proposal (09/04) • Aerospace: • not low risk; proposal (09/03)

42. Marine Vessel Loading: • expect low risk • Petroleum Refineries: • not low risk; proposal 08/03

43. Gasoline Distribution: • not low risk; past due (12/02) • Off-Site Waste: • not low risk; proposal (07/04)

44. Although the screening analysis can serve as a basis for a decision to eliminate low-risk source categories from further consideration under section 112(f), it is not adequate to serve as a basis for

45. establishing additional emission reduction requirements. • The results of a more refined assessment can support either a conclusion of “no further

46. action” or “additional emissions reductions may be needed,” and will be used by EPA to make decisions on whether additional emission reductions are needed for individual source categories.

47. For public health risk management decision-making in the residual risk program, EPA considers the two-step process culminating with an “ample margin of safety” determination, as

48. established in the 1989 benzene NESHAP and endorsed by Congress in the 1990 CAA Amendments as a reasonable approach. • In the first step, a “safe” or “acceptable

49. risk” level is established considering all health information including risk estimation uncertainty. • As stated in the preamble to the rule for benzene, which is a carcinogen,

50. “an MIR (maximum individual risk) of approximately 1 in 10 thousand should ordinarily be the upper-end of the range of acceptability.”