Prediction of lung function response for populations exposed to a wide range of ozone conditions

Abstract

Context: A human exposure–response (E–R) model previously demonstrated to accurately predict population mean FEV₁ response to ozone exposure has been proposed as the foundation for future risk assessments for ambient ozone.Objective: Fit the original and related models to a larger data set with a wider range of exposure conditions and assess agreement between observed and population mean predicted values.

Materials and methods: Existing individual E–R data for 23 human controlled ozone exposure studies with a wide range of concentrations, activity levels, and exposure patterns have been obtained. The data were fit to the original model and to a version of the model that contains a threshold below which no response occurs using a statistical program for fitting nonlinear mixed models.

Results: Mean predicted FEV₁ responses and the predicted proportions of individuals experiencing FEV₁ responses greater than 10, 15, and 20% were found to be in agreement with observed responses across a wide range of exposure conditions for both models. The threshold model, however, provided a better fit to the data than the original, particularly at the lowest levels of exposure.

Conclusion: The models identified in this manuscript predict population FEV₁ response characteristics for 18–35-year-old individuals exposed to ozone over a wide range of conditions and represent a substantial improvement over earlier E–R models. Because of its better fit to the data, particularly at low levels of exposure, the threshold model is likely to provide more accurate estimates of risk in future risk assessments of ozone-induced FEV₁ effects.

Keywords::

• Ozone
• lung function
• exposure–response
• air pollution
• risk assessment
• model evaluation

Acknowledgements

The authors thank Dr. William C. Adams of the University of California, Davis, for providing the individual exposure and response data for studies conducted by him.

Declaration of interest

Dr. McDonnell and Dr. Stewart conducted this modeling research under contract to American Petroleum Institute, and Dr. Schelegle has received funding from American Petroleum Institute to conduct other research to assess the effects of ozone on lung function in humans and to develop ozone exposure–response models in the recent past. Dr. Smith and Dr. Kim have no potential conflicts of interest. American Petroleum Institute, Washington, D.C. provided funding for this modeling effort. Although the research described in this article has been supported in part by the United States Environmental Protection Agency, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.