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Associations Between Ozone and Daily Mortality: Analysis and Meta-Analysis

Ito, Kazuhiko; De Leon, Samantha F.; Lippmann, Morton

doi: 10.1097/01.ede.0000165821.90114.7f
Original Article

Background: There is ample evidence that short-term ozone exposure is associated with transient decrements in lung functions and increased respiratory symptoms, but the short-term mortality effect of such exposures has not been established.

Methods: We conducted a review and meta-analysis of short-term ozone mortality studies, identified unresolved issues, and conducted an additional time-series analysis for 7 U.S. cities (Chicago, Detroit, Houston, Minneapolis–St. Paul, New York City, Philadelphia, and St. Louis).

Results: Our review found a combined estimate of 0.39% (95% confidence interval = 0.26–0.51%) per 10-ppb increase in 1-hour daily maximum ozone for the all-age nonaccidental cause/single pollutant model (43 studies). Adjusting for the funnel plot asymmetry resulted in a slightly reduced estimate (0.35%; 0.23–0.47%). In a subset for which particulate matter (PM) data were available (15 studies), the corresponding estimates were 0.40% (0.27–0.53%) for ozone alone and 0.37% (0.20–0.54%) with PM in model. The estimates for warm seasons were generally larger than those for cold seasons. Our additional time-series analysis found that including PM in the model did not substantially reduce the ozone risk estimates. However, the difference in the weather adjustment model could result in a 2-fold difference in risk estimates (eg, 0.24% to 0.49% in multicity combined estimates across alternative weather models for the ozone-only all-year case).

Conclusions: Overall, the results suggest short-term associations between ozone and daily mortality in the majority of the cities, although the estimates appear to be heterogeneous across cities.

From the Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo Park, NY.

Submitted 12 August 2004; final version accepted 18 February 2005.

Funding provided by contract 3D-6866-YTSX and grant R827997010 from the U.S. Environmental Protection Agency and NIEHS Environmental Health Center grant ES002260.

Publication costs for the paper have been paid by EPA.

Editors’ note: An editorial and commentaries on this article appear on pages 425–435.

Correspondence: Kazuhiko Ito, Nelson Institute of Environmental Medicine, NYU School of Medicine, 57 Old Forge Road, Tuxedo Park, NY. E-mail:

© 2005 Lippincott Williams & Wilkins, Inc.