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Open Access Research

Associations between ozone and morbidity using the Spatial Synoptic Classification system

Adel F Hanna1*, Karin B Yeatts2, Aijun Xiu1, Zhengyuan Zhu3, Richard L Smith4, Neil N Davis1, Kevin D Talgo1, Gurmeet Arora5, Peter J Robinson6, Qingyu Meng7 and Joseph P Pinto8

Author Affiliations

1 Institute for the Environment, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA

2 Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA

3 Department of Statistics, Iowa State University, Ames, Iowa, 50011, USA

4 Department of Statistics and Operations Research, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA

5 HSBC Finance Corporation, Elmhurst, Illinois, 60126, USA

6 Department of Geography, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, USA

7 School of Public Health, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, 08854, USA

8 U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27711, USA

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Environmental Health 2011, 10:49  doi:10.1186/1476-069X-10-49

Published: 24 May 2011

Abstract

Background

Synoptic circulation patterns (large-scale tropospheric motion systems) affect air pollution and, potentially, air-pollution-morbidity associations. We evaluated the effect of synoptic circulation patterns (air masses) on the association between ozone and hospital admissions for asthma and myocardial infarction (MI) among adults in North Carolina.

Methods

Daily surface meteorology data (including precipitation, wind speed, and dew point) for five selected cities in North Carolina were obtained from the U.S. EPA Air Quality System (AQS), which were in turn based on data from the National Climatic Data Center of the National Oceanic and Atmospheric Administration. We used the Spatial Synoptic Classification system to classify each day of the 9-year period from 1996 through 2004 into one of seven different air mass types: dry polar, dry moderate, dry tropical, moist polar, moist moderate, moist tropical, or transitional. Daily 24-hour maximum 1-hour ambient concentrations of ozone were obtained from the AQS. Asthma and MI hospital admissions data for the 9-year period were obtained from the North Carolina Department of Health and Human Services. Generalized linear models were used to assess the association of the hospitalizations with ozone concentrations and specific air mass types, using pollutant lags of 0 to 5 days. We examined the effect across cities on days with the same air mass type. In all models we adjusted for dew point and day-of-the-week effects related to hospital admissions.

Results

Ozone was associated with asthma under dry tropical (1- to 5-day lags), transitional (3- and 4-day lags), and extreme moist tropical (0-day lag) air masses. Ozone was associated with MI only under the extreme moist tropical (5-day lag) air masses.

Conclusions

Elevated ozone levels are associated with dry tropical, dry moderate, and moist tropical air masses, with the highest ozone levels being associated with the dry tropical air mass. Certain synoptic circulation patterns/air masses in conjunction with ambient ozone levels were associated with increased asthma and MI hospitalizations.