Possible climate change impacts on ozone in the Great Lakes region: Some implications for respiratory illness

Many long-range climate and air quality projections suggest that concentrations of certain atmospheric pollutants at ground level will increase. Local levels of gases such as sulfur dioxide, nitrogen oxides, and ozone, as well as various kinds of aerosolized particulate matter are already increasing in some areas. Some of these may cause or exacerbate asthma, respiratory distress, and ultimately cardiopulmonary function. While links to respiratory diseases often involve additional factors, the mechanism for increased risk is well established. However, possible links between air pollution and respiratory disease have not been well studied in the Great Lakes region. Certain results suggest that air pollutants are but some of the many factors that are involved in the etiology of respiratory diseases. Furthermore, different studies have produced results that are inconsistent. Indeed, a simple link between air pollution and climate change has not been well studied at all for any part of the world. Ozone and meteorological data were examined for the period May through September 1986 to 1995 for southeastern lower Michigan. Each day was cataloged as one of nine different synoptic types defined in terms of sea-level pressure, surface vorticity, and windspeed. Ozone concentrations and exceedences (maximum 8-h average concentrations > 80 ppb) for each of the nine synoptic types were also determined. This synoptic ozone climatology revealed that southwesterly anticyclonic flow occurred 16% of the time and accounted for 40% of the ozone exceedences. A linear regression formula was also developed using 13 meteorological variables that are typically linked to high ozone levels in general. This formula reproduced ozone values that agreed well with observed ones [r = 0.76]. The synoptic climatology procedure and the linear regression formula were then applied to output from the Canadian and Hadley models, two General Circulation Models used during the First U.S. National Assessment, to evaluate how conditions that are favorable for high ozone levels may change by the end of this century. Results from both models suggest that southwesterly flow cases, which correlate with high ozone levels at the present time, may become more frequent and lead to decreased air quality and a possible increase in the reported incidence of respiratory disease.