Hot, stagnant air left Augusta under an "orange alert" Friday, in which outdoor air could be unhealthy for children, the elderly and people with respiratory ailments. Today's forecast calls for "moderate" pollution levels, with no health advisory.
The primary concern is ground-level ozone, which is formed by chemical reactions of nitrogen oxides and hydrocarbons, also called volatile organic compounds. They are produced when fuels such as gas or coal are burned or when chemicals evaporate. They combine with heat and sunlight to form smog.
Metro Atlanta has already recorded six days this year in which levels exceeded federal standards. Augusta has no violations so far, although there were four violations in 2008, three in 2007, four in 2006 and one in 2005.
The number of violations could increase this summer. The reason is a new federal ozone standard unveiled last year that reduced the allowable concentration in the air to no more than 0.075 parts per million -- the old standard was 0.085.
Today's forecast calls for a high of 98 degrees, according to the National Weather Service.
Reach Rob Pavey at (706) 868-1222, ext. 119 or firstname.lastname@example.org.
ALL ABOUT OZONE
Ozone is a gas composed of three atoms of oxygen. Ozone occurs both in Earth's upper atmosphere and at ground level. Ozone can be good or bad, depending on where it is found:
GOOD OZONE: Ozone occurs naturally in Earth's upper atmosphere 6 to 30 miles above the surface, where it forms a protective layer that shields us from the sun's harmful ultraviolet rays. Manmade chemicals are known to destroy this beneficial ozone. EPA has established regulations to phase out ozone-depleting chemicals in the United States.
BAD OZONE: In Earth's lower atmosphere, near ground level, ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants and other sources react chemically in the presence of sunlight. Ozone at ground level is a harmful air pollutant.
Source: EPA, NOAA
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