Science Advisory Board, Office of Air and Radiation, Office of Research and Development Notification of Public Workshop

Notice is hereby given that the US EPA Offices of Research and Development (ORD) and Air and Radiation (OAR), along with the US EPA Science Advisory Board (SAB), will jointly host a public workshop on the Benefits of Reductions in Exposure to Hazardous Air Pollutants: Developing Best Estimates of Dose-Response Functions on the date and time noted below. The meeting is open to the public, however, seating is limited and available on a first come basis.

SAB/EPA Workshop on the Benefits of Reductions in Exposure to Hazardous Air Pollutants (HAPs Workshop): Developing Best Estimates of Dose-Response Functions—June 22-23, 2000

The Workshop will be held on June 22 and 23, 2000 at the Westin Grand Hotel, West 2350 M Street, NW, Washington DC 20037, Telephone 202-429-0100. The meeting will begin by 9 a.m. on June 22, 2000 and adjourn no later than 12 p.m. on June 23, 2000.

Purpose of the Meeting—The workshop will convene experts from different disciplines and different backgrounds to discuss ideas for dose response assessment methods for hazardous air pollutants (HAPs) that are appropriate for use in assessing benefits associated with HAP emission control measures. Such benefits assessments are not only required by statute to support EPA's Report to Congress under section 812 of the Clean Air Act Amendments, but they are also required as part of the regulatory activities associated with HAPs. EPA is seeking a wide spectrum of views at the workshop and is not seeking a consensus recommendation from workshop participants.

Expected outcomes from this workshop will include a report documenting: (1) Proposed approaches for hazard assessments for selected HAPs that would facilitate benefit assessments for those chemicals; (2) expert discussants' views on whether it is possible to produce a methodology for developing central tendencies and distributions in hazard assessments for HAPs for use in benefits analyses and how that might best be done; (3) how best to identify limitations and uncertainties in both risk assessment methods and economic models; and (4) suggestions and priorities for a research agenda to address identified gaps in available data and methods needed to conduct HAPs related benefit analyses.

Background—Hazardous air pollutants (HAPs) have been the focus of a number of EPA regulatory actions, which have resulted in significant reductions in emissions of HAPs. EPA has been unable to adequately assess the economic benefits associated with health improvements from these HAP reductions due to a lack of best estimate dose-response functions for health endpoints associated with exposure to HAPs and also due to the air quality and exposure models for HAPs available for use in benefits analysis. EPA is conducting two activities to develop a proposed methodology to generate estimates of the quantified and monetized benefits of reductions in exposure to HAPs. The first will be a workshop focusing on developing best estimates of dose-response functions that relate changes in HAP exposure to changes in health outcomes. The second activity will focus on (1) integrating these dose-response functions with appropriate models of HAP concentrations and human exposure and (2) translating these into economic benefits that would estimate changes in health risks resulting from regulations that reduce HAP emissions.

The overall goal of these two activities is to identify methods for the Agency to consider using in estimating changes in health risks resulting from HAP regulations that can be combined with valuation functions to estimate monetized benefits of HAP reductions.

Risk assessments for HAPs have been developed to help decision makers set health-based standards that are consistent with EPA's mission to protect human health. The quantitative toxicity values from these assessments (that is, the cancer slope factors and the noncancer reference concentrations and reference doses) are typically based on animal and epidemiologic studies that involve higher exposures than those encountered in the environment. The gap between environmental doses and study doses has led to toxicity values that can put a bound on the actual risk without being able to provide a reliable central estimate or distribution of risks. It is these latter terms (central estimates and distributions) that economists have traditionally used to estimate the economic value of potential changes in risks.

In contrast, risk assessments for criteria pollutants have been based on epidemiologic and clinical studies of exposures similar to those encountered in the environment. This has allowed development of standard statistical confidence intervals and distributions. With this information, economists have been able to develop economic benefit estimates for many health endpoints related to criteria pollutants. Criteria pollutant benefit estimates have been feasible because of the availability of: (a) Well-defined health endpoints such as hospital admissions or premature mortality; (b) dose-response functions from epidemiological and clinical studies which support estimates of risk reductions in terms amenable to economic valuation; (c) reliable estimates of ambient concentration and population exposure change; and (d) dose-response functions available from epidemiological and clinical studies in which the exposures were similar to those being experienced in the ambient environment. Uncertainties related to the health benefits of criteria pollutants have generally been represented by standard confidence intervals based on measures of within and between study variation in the estimated health effects.

While mortality from HAP-related cancer is a well-defined endpoint, there are very few validated exposure-response relationships. For the many other potential health effects from exposure to HAPs, such as changes in reproductive functions or mutagenic effects, there are major information gaps in all aspects of risk assessment, as well as in exposure-response and valuation. The focus of this workshop will be the development of best-estimates and uncertainty characterizations for hazard and dose response functions for use in benefits analyses of HAP regulations, with a focus on providing potentially useful data and tools to support HAP-related benefit assessments, including national-scale program evaluations.

For Further Information—Any member of the public wishing further information concerning this workshop should consult the website for this workshop at http://www.epa.gov/ttn/ecas/meetings/coverhap.html or contact Ms. Heather Hodgeman in EPA's Office of Air and Radiation via email at hodgeman.heather@epa.gov or by telephone at (919) 541-5668.