On this day last year, the Susquehanna Valley region had its first red-level "ozone action day'' of the season in which the air quality was considered unhealthy.
Yet, as the region was starting its long summer broil, there had already been several orange-level days in which the air was approaching unhealthful conditions.
Today, the level of ground-level ozone is at the yellow, or "moderate,'' level because of the recently rare appearance of the sun. This is only the second day which the forecast for air quality reached outside the green -- or "good'' -- level since the state began the season's monitoring last month.
"It's been so gray and rainy and damp that it has been green,'' John Repetz, a state Department of Environmental Protection information specialist, said of the air-quality level.
"What causes the ozone to form is the pollutants -- the air emissions. The ozone bakes in the hot sunshine. Since we haven't had the sunshine this year, we just haven't had the conditions for ground-level ozone to form,'' Repetz said.
The state DEP measures air quality based on the levels of five major air pollutants: ozone, particulate matter, sulfur dioxide, carbon monoxide and nitrogen dioxide. Exposure to these pollutants can make it difficult for some people to breathe, especially people with asthma and other respiratory problems.
As levels of any or all of these air pollutants rise beyond health standards, the state issues precautionary warnings.
The warnings serve two purposes, said Ann Meyers, a spokeswoman for the DEP's air-quality campaign. They are intended for people who are sensitive to air pollution to be cautious about their outdoor activity on hot days in which the air quality is poor.
The warnings are also intended to remind people to take action to curb air pollution on those days. About half of the pollution comes from auto and truck emissions, so motorists are urged to carpool or take the bus on those days, rather than drive.
Emissions from small gasoline engines such as lawn-mowers, weed-wackers and chain saws contribute as much as 15 to 20 percent of unhealthy pollution in cities across the United States.
People are asked to wait until late in the day, when the sun is not as strong, to cut their grass. That reduces the time the air pollutants are in the hot air.
Unlike last year, Repetz said, the state DEP will adhere to federal Environmental Protection Agency color-code levels this year. Because there is a higher threshold for red-level unhealthy air in the national standard, the state will call for ozone action days on both orange- and red-level days this year.
Because the parts-per-billion level will remain the same, the number of ozone action days for both orange and red levels combined should be normal for the level of red days last year, he said.
There were 22 ozone action days forecast during last year's hot, dry summer, said Repetz. This year, although it has been a cooler spring, DEP meteorologists are predicating a normal summer, with warmer temperatures and a normal number of ozone action days -- about 20.
"As cloudy and damp as the month of May has been, things can turn around quickly,'' he said.
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