Modelling of individual subject ozone exposure response kinetics

Abstract

Context: A better understanding of individual subject ozone (O₃) exposure response kinetics will provide insight into how to improve models used in the risk assessment of ambient ozone exposure.

Objective: To develop a simple two compartment exposure–response model that describes individual subject decrements in forced expiratory volume in one second (FEV₁) induced by the acute inhalation of O₃ lasting up to 8 h.

Methods: FEV₁ measurements of 220 subjects who participated in 14 previously completed studies were fit to the model using both particle swarm and nonlinear least squares optimization techniques to identify three subject-specific coefficients producing minimum “global” and local errors, respectively. Observed and predicted decrements in FEV₁ of the 220 subjects were used for validation of the model. Further validation was provided by comparing the observed O₃-induced FEV₁ decrements in an additional eight studies with predicted values obtained using model coefficients estimated from the 220 subjects used in cross validation.

Results: Overall the individual subject measured and modeled FEV₁ decrements were highly correlated (mean R² of 0.69 ± 0.24). In addition, it was shown that a matrix of individual subject model coefficients can be used to predict the mean and variance of group decrements in FEV₁.

Conclusion: This modeling approach provides insight into individual subject O₃ exposure response kinetics and provides a potential starting point for improving the risk assessment of environmental O₃ exposure.

Keywords::

• Ozone
• exposure–response model
• human

Acknowledgements

The authors thank William McDonnell for sharing the EPA data base with us and providing insights into his modelling this data set. The authors thank Will Olison and William McDonnell for reading an early version of the manuscript and providing their comments and insights.

Declaration of interest

This research was funded by an unrestricted gift from the American Petroleum Institute.