Tuesday, November 18, 2014

What is the Health Impact from Short Term Exposure to a Combination of Air Pollutants?

A Comparison of Risk Estimates for the Effect of Short-Term Exposure to PM, NO2 and CO on Cardiovascular Hospitalizations and Emergency Department Visits: Effect Size Modeling of Study Findings (14 page pdf, Ellen Kirrane, David Svendsgaard, Mary Ross, Barbara Buckley, Allen Davis, Doug Johns 1, Dennis Kotchmar, Thomas C. Long, Thomas J. Luben, Genee Smith and Lindsay Wichers Stanek, Atmopshere, Dec. 6, 2011)

Today we review research that statistically examines the degree to which one pollutant in combination with one or two others (CO, NO2 and PM) on a short term basis (a few days after exposure) affects health impacts and how much correlation exists between pollutants in causing these impacts. Results indicate that there is an association between NO2 and PM as one might expect this from transportation emissions and also the association between NO2 and cardiovascular diseases. The authors recommend a greater density of monitors to measure the pollutant concentrations and to isolate the influence of each. PM CO and NO2 correlations  

Key Quotes:

 “The objective of this analysis was to use meta-regression methods to model effect estimates for several individual yet correlated NAAQS pollutants in an effort to identify factors that explain differences in the effect sizes across studies and across pollutants.”

“One previous multicity analysis conducted in Europe reported that 84% of the heterogeneity in the PM10 estimates across the cities examined could be explained by the PM10-NO2 correlation.”

“Associations between short term NO2 exposure and cardiovascular hospitalizations were also consistently observed”

“the suggestion that NO2 effect estimates are higher when PM10 concentrations are also elevated may suggest a joint effect of these pollutants, or that PM is an indicator for poor air quality in general. “

“we present preliminary results suggesting that study methodology, concentrations of other pollutants, and monitor density may influence the observed effect estimates in single-city studies of air pollution and cardiovascular hospitalizations or ED visits. Our results may be useful in the design of future studies or aid in interpreting health effects in a multipollutant context. “

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