Three Meta-Analyses Find Short-Term Ozone Exposures Increase the Risk of Death
The U.S. Environmental Protection Agency commissioned 3 meta-analyses of studies of ozone and mortality. Three separate research groups were asked to conduct a meta-analysis, using their own methods and study selection criteria. All three studies report a small but substantial association between daily ozone levels and total mortality.
Researchers from Johns Hopkins University looked at 144 effect estimates from 39 time-series studies and estimated pooled effects by lags, age groups, cause-specific morality, and concentration metrics. They compared the results with pooled estimates from the National Morbidity, Mortality, and Air Pollution Study (NMMAPS) a time-series study of 95 large U.S. urban centers from 1987 to 2000. They found that the meta-analysis and NMMAPS results provided strong evidence of a short-term association between ozone and mortality, with large effects for cardiovascular and respiratory deaths, the elderly, and current-day ozone exposure.
Harvard University scientists gathered 71 time-series studies relating ozone to all-cause mortality, and selected 48 estimates from 28 studies for the analysis. They found a greater effect in the summer, and concluded that the “relationship between ozone and mortality should be considered for future regulatory impact analyses.”
New York University researchers conducted a review of 43 short-term ozone mortality studies from around the world 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. Their results suggest short-term associations between ozone and mortality, although the estimates vary from city to city.
A commentary on the meta-analyses by Dr. David Bates concludes: “The 3 new meta-analyses … along with the recent European study, each have unique features and appear to resolve the question of whether ambient ozone levels are associated with increased mortality. It seems unlikely that PM2.5 is an important confounder, and the effect of ozone appears to be independent of temperature. A final question — that of biologic plausibility — is in some ways the easiest to answer. Ozone is capable of causing inflammation in the lung at lower concentrations than any other gas. Such an effect would be a hazard to anyone with heart failure and pulmonary congestion, and would worsen the function of anyone with advanced lung disease.”
Bell ML, Dominici F, and Samet JM. A Meta-Analysis of Time-Series Studies of Ozone and Mortality with Comparison to the National Morbidity, Mortality, and Air Pollution Study. Epidemiology 2005; 16:436-445.
For a copy of the study click here.
Levy JI, Chermerynski SM, Sarnat JA. Ozone Exposure and Mortality: An Empiric Bayes Metaregression Analysis. Epidemiology 2005: 16:458-468.
For a copy of the abstract click here.
Ito K, De Leon SF, Lippmann M. Associations Between Ozone and Daily Mortality: Analysis and Meta-Analysis. Epidemiology 2005; 16:446-429.
For a copy of the abstract click here.
Bates DV. Ambient Ozone and Mortality. Epidemiology 2005; 16:427-429.
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Goodman SN. The Methodologic Ozone Effect. Epidemiology 2005; 16:430-435.
For a copy of the article click here.
