Comparing Three Approaches for Deriving Potency Estimates for Acute Noncancer Health Effects: Phosgene-A Case Study.* S. Sigethy, I. L. Cote, D. Costa, M. J. Selgrade and J. J. Vandenberg, Duke University, School of the Environment, Durham, NC 27708; and U.S. EPA Health Effects Research Laboratory, Research Triangle Park, NC 27711
The Environmental Protection Agency (EPA) is evaluating adverse noncancer health effects resulting from acute and repeated acute exposures to hazardous air pollutants (HAPs). Currently, the EPA does not have an approved methodology for evaluating short-term air exposures to HAPs. Using phosgene as a prototype air pollutant, this paper presents and compares three alternative methods which the EPA could use to assess acute and repeated acute exposures to toxic air pollutants. Pulmonary and immunotoxicology data are evaluated. The three methods, a modified acute inhalation reference concentration (RfC) approach, the benchmark dose approach, and the biologically-based dose-response modeling approach are described and the advantages and limitations of each are discussed. Reference levels are calculated for the first two approaches and the resulting values compared. Key risk assessment issues critical to the evaluation of each approach such as the concentration-duration-response relationship, severity of effects, low dose extrapolation, rat to human risk extrapolation, mechanism of action, and implications for disease induction in humans are discussed.
*Work supported by fellowship #U-914332-01-0.
This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.