An Assessment of Surface-Level Ozone Trends In Southeastern Cities, 1981–1993

Southeastern Geographer Vol. XXXVIII, No. 1, May 1998, pp. 41-57 AN ASSESSMENT OF SURFACE-LEVEL OZONE TRENDS IN SOUTHEASTERN CITIES, 1981-19931 Walter Martin Trends in the level of ozone pollution have been obscured by short-term changes in meteoro­ logical conditions and by long-term changes in levels of fossil fuel combustion and evaporative emissions. The relatively hot, dry summer of 1993 witnessed a return to elevated ambient ozone concentrations in several locations across the Southeast and provides an opportunity to make a comparison with similarly high ozone episodes more common during the 1980s. Meteorologi­ cally adjusted ozone trends for 12 cities across the southeastern United States from 1981 through 1993 are identified. Analysis of covariance models were used to reduce the effect of se­ lected meteorological variables and calculate annual least-squares means for ozone concentra­ tions. Results indicate that ozone levels have improved in four cities, worsened in three cities, and demonstrated no trend in five cities. The risks to forest, agriculture, and human health that are associated with ex­ posure to oxidant air pollutants and particulates emphasize the importance of ade­ quate pollutant standards and trend assessment. Prominent contributions by Bruck (1989), Heck (1989), Lefohn and Foley (1993), and Chameides (1994) ad­ dress the current and potential threats to forest and agriculture. Samet et al. (1994) have called for further research to understand better the risks posed by oxidants and particulates to human health.2Although results from animal studies and stud­ ies using test subjects have implicated ozone and other air pollutants (Bartlett etal., 1974; Lastetal., 1979; Linnetal., 1982; Last etal., 1984; Tyler etal., 1988), the strongest evidence of health effects from air pollution is epidemiological.3 One of the leading pollutants responsible for degrading air quality in the southeastern United States is ozone. Trends in the level of ozone pollution have been obscured by short-term changes in meteorological conditions and by long­ term changes in levels of fossil fuel combustion and evaporative emissions. The influence ofmeteorology on levels ofpollution and specifically on ozone levels is widely acknowledged. Meteorological variables alone can account for much of the day-to-day and site-to-site variations of the daily maximum one-hour average ozone concentrations in the United States (Clark and Karl, 1982). Emissioncontrol strategies based simply upon time series of hourly ozone maxima ignore the potential effect of weather on these somewhat rare and extreme events. Even though ozone densities greater than 120 ppb are used as the National Ambient Air Quality Standard (NAAQS) for ozone, these extreme values have Dr. Martin is Assistant Professor o f Geography at the University o f North Carolina at Charlotte, Charlotte, NC 28223. 42 S o u t h e a s t e r n G e o g r a p h e r larger statistical uncertainties than annual means. The limitations of inferring trends and standards from rare and extreme statistics have been identified by Chock and Heuss (1987) and Yosie et al. (1993), who suggested that, because of their large fluctuations, extreme values should not be used to ascertain long-term trends in ozone levels. In light of recent findings, the U.S. Environmental Protec­ tion Agency (EPA) recently proposed new standards for ozone and fine (F R2 F ratio Prob >F Atlanta 0.03 0.43 0.53 0.15 1.93 0.19 Charlotte 0.01 0.05 0.83 -0.26 3.87 0.08 Greensboro 0.10 1.15 0.31 0.05 0.63 0.45 Louisville 0.00 0.00 0.97 -0.10 1.15 0.31 Memphis 0.08 1.00 0.34 0.01 0.05 0.83 Miami 0.34 5.61 0.04a 0.44 8.49 0.01a Nashville -0.02 0.17 0.69 -0.08 0.91 0.36 New Orleans 0.02 0.24 0.64 0.01 0.07 0.80 Norfolk 0.03 0.35 0.57 0.00 0.02 0.89 Orlando 0.09 1.13 0.31 0.07 0.85 0.38 Tampa 0.00 0.04 0.85 -0.15 1.95 0.19 Washington, DC -0.01 0.16 0...