Ozone is the major component of summertime smog in the Mid-Atlantic Region. Ozone in the upper atmosphere is beneficial to life, shielding the earth from harmful ultraviolet radiation from the sun. In contrast, a high concentration of ozone in the air we breathe is a major health and environmental concern.

Ozone is formed when sunlight provides energy for chemical reactions between airborne volatile organic compounds and nitrogen oxides. Ozone can be formed miles downwind from sources of these pollutants, and high concentrations of ozone can occur over large areas.

Comparison of 8-hr and 1-hr Ozone Exceedances in the Mid-Atlantic Region, July 1999, S.H. Alcorn, P.T. Roberts, H.H. Main, Sonoma Technology, Inc.

This report evaluates Mid-Atlantic air quality in 1997 using both the 1-hour and 8-hour ozone standards. The report concludes:

    • The 8-hour standard is exceeded more often than the 1-hour standard. In 1997, 8-hour ozone pollution levels were higher than 85 ppb on four times as many days as 1-hour levels were over 125 ppb.

    • The 8-hour standard is exceeded more widely than the 1-hour standard. In 1997, 89% of monitoring sites in the Mid-Atlantic region recorded 8-hr values over 85 ppb, while only 36% had 1-hr values over 125 ppb.

    • The 8-hr standard is exceeded both earlier and later in the summer. All of the days in 1997 when the 1-hour ozone level exceeded 125 ppm occurred in June and July. On the other hand, a significant number of days when 8-hour ozone exceeded 85 ppb occurred in May, August, and September.

In addition, the report reviewed 1986-1997 data in comparison to the 8-hour standard. This review used 3-year averages of the annual fourth-highest daily maximum 8-hour values, so that the data is consistent with the form of the 8-hour ozone standard. The report concluded that there was no clear regional trend in 8-hour ozone values. Even looking at the sites with the most extreme changes, there was no improvement in air quality with respect to the new standard.

This analysis could be updated using 1998 and 1999 data when they become available. It could also be integrated with a recent MARAMA staff report summarized below.

1995 Ozone Atlas for the Mid-Atlantic Region (June 1997)

This Atlas presents basic information about ozone air pollution in the Mid-Atlantic Region in the form of maps, charts, and tables accompanied by brief explanations.

The highest ozone levels in the ten years between 1986 and 1995 were recorded in 1988. Nationally, 1988 was the third hottest summer in 100 years. After 1988, peak ozone levels declined, and there were fewer days with ozone levels above the national health standard in place at the time. However 1995 was also a record hot summer, and ozone levels in most of the Mid-Atlantic Region were higher in 1995 than they had been in many years. In addition to combustion related emissions of nitrogen oxides, measurement of target volatile organic compounds at PAMS monitoring stations indicated motor vehicle exhaust and gasoline vapors, natural gas use and transport, natural emissions, and graphic arts/surface coating industries were contributing to ozone formation. Cleaner cars, reformulated gasoline, and reductions in nitrogen oxide emissions at some major sources had improved air quality by 1995.

Summary of Mid-Atlantic 8-Hour Ozone Data, 1986-1997, October 1999, S.S.G. Wierman, S. Kayin, and E. Belyaev, Mid-Atlantic Regional Air Management Association.

This report reviews 12 years of 8-hour ozone data for the Mid-Atlantic region. The data were obtained from EPA's AIRS system for each monitoring site in the region for 1986 through 1997.

The data show continued widespread violations of the 8-hour ozone standard in all Mid-Atlantic States. Since the late 1980s, there has been a reduction in the number of very high exceedances, even though the total number of 8-hour exceedances remains high. At the state level, it is impossible to observe any obvious trend in recent data. Most of the monitors that continue to violate the standard have 3-year averages between 85 and 104 ppb, which EPA's Air Quality Index defines as "Unhealthy for Sensitive Groups."