US to revise air quality standards for ozone

the us Environmental Protection Agency (epa) has proposed to revise the national ambient air quality standards for ozone for the first time since 1997. The proposal recommends an ozone standard within a range of 0.07-0.075 ppm (parts per million). At the same time, it has asked for comments on a range of alternative levels of standards between 0.06 ppm and 0.08 ppm (the current standards). Although the proposed level is tighter than the existing level, it has drawn criticism from environmental and health groups.

"While the revisions are a step towards cleaner air, epa's plan falls short of the goal recommended by its own experts. It barely touches the most protective levels recommended by the Clean Air Scientific Advisory Committee (casac) scientists. They had recommended that standards should be between 0.060 and 0.070 ppm,' said Norman Edelman, chief medical officer of the American Lung Association. Besides, he says the plan leaves the door open to the option of not making any improvements at all.

In October 2006, the casac ozone review panel had said that there is no scientific justification for retaining the current ozone standards and it needs to be substantially reduced to protect human health. The team had then unanimously recommended a range of 0.060-0.070 ppm for new standards.

But epa says the proposed standards will provide appropriate protection against a variety of health effects associated with ozone exposure and that standards below 0.07 ppm or above 0.075 ppm will not be appropriate.

"A standard below 0.07 ppm will not be appropriate because evidence linking ozone exposure to specific health effects becomes increasingly uncertain at lower levels of exposure and above 0.075 ppm, evidence of public health risks exist,' says epa.

But environmental groups want further tightening of standards. The final decision is expected to be taken by March 12, 2008.

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