Maryland experienced record-low levels of smog this year, making it a little easier to breathe in the Baltimore-Washington area, mostly because of the mild, rainy summer.
A string of 17 air quality monitors from Charles to Cecil counties recorded only four days since May 1 in which smog reached unhealthful levels, a low achieved only two other times in the past 17 years. And it is unlikely that number will change, given the forecast for partly cloudy, cool weather through today, the last day of the smog season.
Moreover, the average annual number of days with unhealthful levels of smog has been more than halved, from 22 in the 1980s to fewer than 10 in the 1990s. Smog reached unhealthful levels 43 days in 1983, the earliest year for which the Maryland Department of the Environment has records, 23 days in 1987 and 36 days in 1988. The most since then was 17 days in 1991.
Yet Maryland's air remains among the worst on the East Coast, matching Connecticut, New York and Pennsylvania for the number of bad-air days in 1999, according to the Department of the Environment. And the daily average smog levels "are creeping upward," said Russell Dickerson, an atmospheric chemist in the meteorology department at the University of Maryland.
"We've been successful in shaving off the peaks. The trend in the worst days is improving," he said, "but the average is not improving."
Smog, or ground-level ozone, is a colorless, odorless gas created when a mix of fumes from vehicle and lawn mower exhaust pipes, industrial smokestacks and boats cook in the heat and sunlight of midsummer days. It can cause lung damage, eye irritation, breathing difficulties, coughing and chest pains.
This summer, temperatures reached 90 degrees or higher only five times in June and once each in July and August, the three months the U.S. Weather Service considers summer.
More than 5 inches of rain fell in June and again in July, for a total of 11.2 inches, 3.83 inches more than the normal total. Although rainfall last month was almost an inch below normal, only 37 days were without rain from June 1 to Aug. 31, compared with 58 dry days during the summer of 1999.
As a result, state smog forecasters recorded a steady stream of good and moderate air quality days, in which smog levels stayed well below the 125 parts per billion that trigger Code Red air quality warnings under the federal Clean Air Act. July and August saw an improbable, for the summer, string of 45 consecutive good and moderately good air quality days.
The national weather pattern that brought scorching heat and drought to parts of Texas and the Midwest this summer also was responsible for the cloudy skies, low temperatures and record-low smog levels throughout the Northeast, said Charles Piety, the ozone forecaster at UM.
While the weather has been primarily responsible for the lowest smog level in Maryland in four years, pollution-control programs have played a significant role in reducing the number of smoggy days in general, Randy Mosier, an MDE planner said. "We're starting to see some impact from the more strict regulations and the vehicle emissions program."