A report critical of US Environmental Protection Agency efforts to reduce ground-level ozone pollution can create a faulty impression.
The Sept. 29 report by EPA's inspector general points out that more than 159 million Americans live in areas not meeting the recently adopted 8-hr ozone standard and that "most polluted metropolitan areas are still struggling to attain EPA's [less strict] 1-hr ozone standard established over 25 years ago."
The report focuses on the failure of many cities to cut emissions of ozone precursors by the 3%/year required by clean-air laws and points out ways EPA can toughen enforcement.
Findings like these feed the widespread impression that air quality in the US is deteriorating.
Indeed, ozone pollution remains a tough problem in many of the 56 areas that in 2003 failed to meet federal air-quality standards for the substance.
But ozone is just one of six pollutants subject to federal regulation under the Clean Air Act. And it, like the other five pollutants, is in long-term decline.
Aggregate emissions of all six so-called criteria pollutants in 2003 were down 51% from their levels of 1970, and the trend is steadily downward.
The only emissions increase between 2002 and 2003 was that of sulfur dioxide�up 500,000 tons to 15.8 million tons but still half the level of 1970.
Concentrations of ozone in 2003 were down 16% from 1990's level and 29% from 1980's level by the 1-hr standard. By the 8-hr standard, the declines were 9% and 21%.
Emissions of the main ozone precursors, nitrogen oxides and volatile organic compounds, were down in 2003, as well.
In fact, ozone concentrations in 2003 were the lowest since 2003, partly because of weather.
For ozone and the other criteria pollutants, the improvements result from clean-air statutes, EPA regulation, and technical innovation such as reformulated gasoline. They have occurred despite increases in population, economic output, vehicle use, and energy consumption.
In many cities, especially those with lots of cars and sunshine, ozone is a chronic problem. But it's not the whole story on US air quality. And air quality is not deteriorating.
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