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Government Toughens Smog Standards

Environmental Protection Agency Cuts Allowable Levels of Ozone; Critics Say It's Not Enough
WebMD Health News
Reviewed by Louise Chang, MD

March 12, 2008 -- The Environmental Protection Agency (EPA) has toughened its smog regulations by lowering the allowable level of ozone in the air. But some health groups say the new standards aren't strict enough to protect the public's health.

The agency lowered the legally acceptable level of ozone, the main component of smog, from 0.084 to 0.075 parts per million (ppm). That would mean that counties nationwide with higher ozone levels per eight-hour period would be required to take cleanup steps.

Ozone is formed when emissions of nitrogen oxides and volatile organic compounds (mainly from power plants and car tailpipes) are exposed to sunlight and heat. It can cause lung irritation and worsen human lung diseases, including asthma and emphysema. Ozone pollution is generally worse during warm summer months, when the majority of poor air-quality days occur.

Scientists Urge Stricter Standard

Health and environmental groups have lobbied for years for a stricter ozone standard. EPA Administrator Steven Johnson said Wednesday that lowering allowable ozone to 0.075 ppm would protect the public health and was "based on the science."

"I concluded that 0.075 was health protective," Johnson told reporters in a conference call Wednesday.

In 2006, the EPA's Clean Air Science Advisory Committee (CASAC) concluded a significantly lower ozone level was needed to prevent ill health effects.

"The primary 8-hr (standard) needs to be substantially reduced to protect human health, particularly in sensitive subpopulations. Therefore, the CASAC unanimously recommends a range of 0.060 to 0.070 ppm for the primary ozone (standard)," the panel concluded in an October 2006 report.

Johnson said he had tightened ozone standards in accordance with the Clean Air Act, the 38-year-old law that gave rise to ozone regulation. He said lower standards would not be practical and may not even be achievable in some cities. Johnson pointed to 85 counties that he said have not yet met 1996 ozone standards.

"Bottom line -- I adhered to the law and I certainly also considered the most recent scientific evidence in making the decision," he said. 

Counties don't have to start meeting the standard until 2013.

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