Acute Ozone Exposure-Response Relationships for Use in Health Risk Assessment

Abstract

The U.S. Clean Air Act requires that primary national ambient air quality standards (NAAQS) be set to protect the public health, with an adequate margin of safety. As one input to its current review of the NAAQS for ozone, the U.S. Environmental Protection Agency (EPA) has sponsored an ozone health risk assessment. The first part of the assessment is directed at the effects of acute (1–2 hour) ozone exposure and estimates the risk of acute ozone-induced lung function impairment and lower respiratory symptoms in heavy exercisers, the group thought to be at highest risk from acute ozone exposure due to high dosage rates. Latter parts of the risk assessment, aimed at the effects of multihour and chronic ozone exposure, are underway. This paper describes development of the exposure-response relationships used in the acute effects part of EPA’s ozone health risk assessment. Relationships are derived from human clinical exposure studies in which heavily exercising subjects were exposed to ozone under controlled conditions. Data set comparisons are presented, along with a description of final exposure-response relationships and their derivation.