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Does one size fit all? The suitability of standard ozone exposure metric conversion ratios and implications for epidemiology

Journal of Exposure Science & Environmental Epidemiology volume 20, pages 2–11 (2010)Cite this article

Abstract

Several exposure metrics have been applied in health research and policy settings to represent ozone exposure, such as the 24 h average and daily 8 h maximum. Frequently, results calculated using one exposure metric are converted using a simple ratio to compare or combine findings with results using a different metric. This conversion, however, assumes that such a ratio is constant across locations and time periods. We investigated the appropriateness of this conversion method by examining the relationships among various forms of ozone concentrations (24 h average, daily 1 h maximum, and daily 8 h maximum) within and between communities for 78 US communities from 2000 to 2004 and compared results to commonly used conversion ratios. We explored whether the relationships between ozone exposure metrics differ by region, weather, season, and city-specific characteristics. Analysis revealed variation in the relationship among ozone metrics, both across communities and across time within individual communities, indicating that conversion of ozone exposure metrics with a standard ratio introduces uncertainty. For example, the average ratio of the daily 8 h maximum to the daily concentration ranged from 1.23 to 1.83. Within a community, days with higher ozone levels had lower ratios. Relationships among metrics within a community were associated with daily temperature. The community-average exposure metric ratios were lower for communities with higher long-term ozone levels. Ozone metric ratios differed by season because of the different rate of change of ozone metrics throughout the year. We recommend that health effects studies present results from multiple ozone exposure metrics, if possible. When conversions are necessary, more accurate estimates can be obtained using summaries of data for a given location and time period if available, or by basing conversion ratios on data from a similar city and season, such as the results provided in this study.

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Acknowledgements

We thank Keita Ebisu of Yale University, Tom Dessent of the US EPA, and Joseph Pinto of the US EPA. Funding for Ms. Anderson was provided by the National Science Foundation through an NSF Graduate Fellowship and by the EPA through an EPA STAR Fellowship (91689201-0). Funding for Dr. Bell was provided by the Health Effects Institute through the Walter A. Rosenblith New Investigator Award (4720-RFA04-2/04-16) and the NIEHS Outstanding New Environmental Scientist (ONES) Award (RO1 ES015028). Views expressed in this paper do not necessarily reflect views of the sponsoring agencies.

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  1. Environmental Engineering, Yale University, New Haven, Connecticut, USA

    G Brooke Anderson

  2. School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA

    Michelle L Bell

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Correspondence to Michelle L Bell.

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Supplementary Information accompanies the paper on the Journal of Exposure Science and Environmental Epidemiology website (http://www.nature.com/jes)

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Anderson, G., Bell, M. Does one size fit all? The suitability of standard ozone exposure metric conversion ratios and implications for epidemiology. J Expo Sci Environ Epidemiol 20, 2–11 (2010). https://doi.org/10.1038/jes.2008.69

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