I niled Siiiics I'n\iioiiiucii 1 ;il I'rolcclion .\»enc\ Office ol" Research :ind Dcxclopmcnl National Hxposure Research Laboratory KY02 Research Abstract Government Perfonnance Results Act (GPRA) Goal 1 APM26 Significant Research Findings: Research Plan for Human Exposure Measurements and Modeling of Air Toxics The U.S. Environmental Protection Agency's (EPA) air toxics program is currently in a transition to a risk-based approach to develop and implement additional federal, state, and local regulatory and voluntary measures to reduce risk. One of the main components of EPA's risk-based air toxics program is the National Air Toxics Assessment (NATA) of human exposure to hazardous air pollutants. Assessments conducted as part of NATA help EPA identify areas of concern, characterize risks, and track progress toward meeting overall air toxics program goals, one of which includes the reduction in uncertainty and variability in exposure model predictions. In order to achieve this and other goals of EPA's air toxics program, the National Exposure Research Laboratory (NERL) is developing new methods, collecting current measurement data, and creating relevant models for evaluating human exposure to air toxics that provide a scientific basis for EPA to move towards a risk-based program and to support the needs of various EPA Program Offices. Research The overall approach in developing EPA's human exposure research Approach program is to integrate modeling and measurements research iteratively. Existing data are used for the model development process and, upon completion of historical data collection efforts, are then used to identify gaps in knowledge and key sources of variability and uncertainty that may potentially influence exposure and dose model predictions. Those model parameters that represent the greatest uncertainty are identified as critical research needs. Laboratory and field measurement studies are then designed and conducted to address these prioritized needs. The first generation model is refined and evaluated based on the new measurement data. Where needed, new methods are developed that would allow for the appropriate data to be collected and employed for further model development. Because of the iterative nature of the measurement/modeling process and to provide high quality output for end users of the measurement data and/or model, it is necessary to perform a needs analysis and coordinate the research efforts of both research groups through the development of a research plan. During the Scientific Problem and Policy Issues National Exposure Research Laboratory November 2002 ------- research plan implementation phase, proposed studies will be designed and conducted, and model parameters and algorithms will be refined to ultimately reduce uncertainties in estimates of human exposure to air toxics. Results and Existing data, acquired from previous research studies, have been reviewed, Implications compiled, and evaluated. Meetings were conducted with various EPA Program Offices, scientific workshops were attended, and, in addition, NATA estimated exposures and risks for various cohorts and population groups were evaluated. Results of this initial investigation have directed the initial phase of the research towards specific air toxics to address and identify data gaps and areas requiring additional research by NERL. These needs have been compiled and presented in a peer-reviewed Research Plan for Human Exposure Measurements and Modeling of Air Toxics, jointly prepared by NERL's human exposure measurements and modeling groups. The research plan addresses the following needs: additional microenvironmental exposure data specifically including mobile source exposures; additional exposure data for benzene, formaldehyde, acetaldehyde, acrolein, 1,3 butadiene, perchloroethylene, and diesel particulate matter; method development for compounds such as acrolein for which current methods are considered unacceptable; method development for compounds such as 1,3- butadiene to improve recoveries and lower limits of detection to reduce non-detects during monitoring; better spatial/temporal data for allocation of area source emissions; updated concentrations of pollutants found in homes and microenvironments to reflect current lifestyles, product formulations and use; better time and activity data for groups such as children and non- English speaking persons; "hot spot" exposure data from specific sources to provide information on highly exposed individuals; develop aggregate (multipathway) model for air toxics; consider indoor source contribution to exposure; explicitly address uncertainty and variability in model predictions; perform a method evaluation for assessing longitudinal exposure; improve estimates of mobile source exposure; and refine commuter pattern algorithms. The Research Plan outlines the types of studies necessary to acquire the most critical air toxics exposure data and the model development needed for improved prediction of human exposure to air toxics. The Stochastic Human Exposure and Dose Simulation model (SHEDS) has been previously developed by NERL to evaluate, both realistically and reliably, population exposures to a wide variety of environmental pollutants using a probabilistic National Exposure Research Laboratory November 2002 ------- approach. The SHEDS methodology will serve as the core of NERL's exposure modeling research on air toxics. The Research Plan was reviewed by a panel that consisted of researchers from EPA's Office of Pollution Prevention and Toxics (OPPT), Office of Transportation and Air Quality (OTAQ), National Center for Environmental Assessment (NCEA), Office of Air Quality Planning and Standards (OAQPS), and National Health and Environmental Effects Research Lab (NHEERL). The Research Plan satisfies Annual Performance Measures (APM) 26 and 219 and proposes an integrated research program that will provide exposure data and modeling tools in support of EPA Program Office needs and future NATA assessments. The research plan, entitled "NERL Human Exposure to Air Toxics Measurements and Modeling Research Plan," was a collaborative effort between NERL Human Exposure and Atmospheric Sciences Division staff in the Human Exposure Analysis Branch (HEAB) and Atmospheric Chemistry and Physics Branch (ACPB). Future Research Future measurement research will involve implementation of the research plan by designing and performing targeted field measurement studies to collect data to meet the research needs identified in the plan. Work to be performed on the SHEDS-Air Toxics model is part of a larger on-going effort to develop models to improve our understanding of the routes, pathways, and factors that contribute to pollutant exposure and dose. In addition, work is being done to refine the dose aspects of the model using the exposure related dose estimating model (ERDEM) being developed in NERL. The ERDEM research will help SHEDS to better simulate the body's uptake, metabolism, and elimination of air toxics. Research Collaboration and Publications National Exposure Research Laboratory November 2002 ------- Contacts for Questions and inquiries on NERL's human exposure measurements research Additional for ajr toxics can be directed to: Information Donald A. Whitaker US EPA, Office of Research and Development National Exposure Research Laboratory, D205-04 Research Triangle Park, NC 27711 Phone: 919/541-1571 E-mail: whitaker.donald@epamail.epa.gov Questions and inquiries on NERL's human exposure and dose modeling research can be directed to: Haluk Ozkaynak, Ph.D. US EPA Headquarters, 8601D Ariel Rios Building 1200 Pennsylvania Avenue, N. W. Washington, DC 20460 Phone: 202/564-1531 E-mail: ozkaynak.haluk@epa.gov National Exposure Research Laboratory November 2002 ------- |