U.S. EPA Proposes New Smog Standards

On January 19, 2010, the U.S. Environmental Protection Agency published in the Federal Register a proposed rule that would set more stringent standards for ground-level ozone, more commonly known as smog.  U.S. EPA is proposing these new standards after reconsideration of limits set by the Bush administration in 2008.

Specifically, "EPA proposes that the level of the 8-hour primary standard, which was set at 0.075 ppm in the 2008 final rule, should instead be set at a lower level within the range of 0.060 to 0.070 parts per million (ppm), to provide increased protection for children and other ‘‘at risk’’ populations against an array of O3-related adverse health effects that range from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes, and possibly cardiovascular-related morbidity as well as total nonaccidental and cardiopulmonary mortality."

U.S. EPA also proposes that the "secondary O3 standard, which was set identical to the revised primary standard in the 2008 final rule, should instead be a new cumulative, seasonal standard expressed as an annual index of the sum of weighted hourly concentrations, cumulated over 12 hours per day (8 am to 8 pm) during the consecutive 3-month period within the O3 season with the maximum index value, set at a level within the range of 7 to 15 ppm-hours, to provide increased protection against O3-related adverse impacts on vegetation and forested ecosystems."

According to a fact sheet prepared by U.S. EPA, "ozone is found in two regions of the Earth’s atmosphere – at ground level and in the upper regions of the atmosphere.  Both types of ozone have the same chemical composition (O3).  While upper atmospheric ozone forms a protective layer from the sun’s harmful rays, ground level ozone is the main component of smog.  Ground-level ozone is not emitted directly into the air, but forms through a reaction of nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO) and methane (CH4) in the presence of sunlight.  Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are the major man-made sources of NOx and VOCs."

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