The Environmental Protection Agency (EPA) is considering imposing a new air quality standard for metropolitan areas requiring lower levels of ozone measured over a longer time. The current standard defines an area to be in "nonattainment" if, on just four days of a three-year period, any monitor registers a concentration of ozone above 0.12 parts per million (ppm) for one hour. The proposed standard would be 0.08 ppm measured over eight hours. The health benefits, if any, of such a change are unknown.

• At low levels of exposure to ozone, most people suffer no effects and any measurable effects usually disappear after a few hours.

• Unless they are heavily exercising outdoors, even the most sensitive individuals do not experience statistically significant declines in lung function after one to three hours of exposure around the current permissible level of 0.12 ppm.

• Although there have been fewer studies of prolonged exposure to ozone, those that have been completed have shown no cases of irreversible or life-threatening physiological changes at 0.12 ppm - or even higher levels.

The costs of complying with the current ozone standard are high, and attempting to meet a lower standard would cost even more.

• Based on estimates from the Office of Technology Assessment, every dollar of benefit derived from compliance with the current ozone standard costs consumers and taxpayers between $3.30 and $5.10.

• Further reducing some of the reactive gases from automobiles and industrial sources that produce ozone by 40 percent by the year 2005 would cost approximately $10.9 billion annually, in 1994 dollars.

• The National Research Council estimates that under the right weather conditions, vegetation alone forms enough ozone on some days to exceed the current standard in some areas.

The number of days that cities are in violation of the current ozone standard has declined over the last decade by 57 percent. But under the proposed standard, the EPA estimates that 67 additional cities would be defined as having dirty air and one-third would record 10 or more violations of the standard each year.

Source: Kenneth Chilton and Christopher Boerner, "Smog in America: The High Cost of Hysteria," Policy Study No. 128, January 1996, Center for the Study of American Business, Washington University, Campus Box 1208, One Brookings Drive, St. Louis, MO 63130, (314) 935-5630.

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