An alternative form and level of the human health ozone standard

Abstract

Controlled human laboratory studies have shown that there is a disproportionately greater pulmonary function response from higher hourly average ozone (O₃) concentrations than from lower hourly average values and thus, a nonlinear relationship exists between O₃ dose and pulmonary function (FEV₁) response. The nonlinear dose–response relationship affects the efficacy of the current 8-h O₃ standard to describe adequately the observed spirometric response to typical diurnal O₃ exposure patterns. We have reanalyzed data from five controlled human response to O₃ health laboratory experiments as reported by , Adams (), and . These investigators exposed subjects to multi-hour variable/stepwise O₃ concentration profiles that mimicked typical diurnal patterns of ambient O₃ concentrations. Our findings indicate a common response pattern across most of the studies that provides valuable information for the development of a lung function (FEV₁)–based alternate form for the O₃ standard. Based on our reanalysis of the realistic exposure profiles used in these experiments, we suggest that an alternative form of the human health standard, similar to the proposed secondary (i.e., vegetation) standard form, be considered. The suggested form is an adjusted 5-h cumulative concentration weighted O₃ exposure index, which addresses both the delay associated with the onset of response (FEV₁ decrement) and the nonlinearity of response (i.e., the greater effect of higher concentrations over the mid- and low-range values) on an hourly basis.

Keywords::

• Human studies
• nonlinear dose response
• ozone standard
• sigmoidally weighted exposure index
• spirometry

Acknowledgements

We wish to acknowledge Dr. Edward Schelegle, Department of Anatomy, Physiology, and Cell Biology, University of California Davis School of Veterinary Medicine, for making available the data that were used in our analysis and his helpful discussions concerning the data. In addition, we wish to acknowledge the excellent quality of comments that we received from the peer reviewers. Their comments allowed us to present our analysis with greater clarity.

Declaration of interest

This work was partially funded by API, Washington, DC, with the remaining funds provided by the company (A.S.L. & Associates) of one of the authors (A.S. Lefohn).