Linda Brown loves to play tennis, but the tanned, athletic-looking Columbia woman says she was huffing and puffing whenever she hit the courts this summer.
She has asthmatic bronchitis, a chronic breathing problem that has plagued her for the past 10 years.
But Brown never has had as much trouble getting her breath as in the past few months, just a year after moving to the Baltimore area from New York.
Brown says she thought that the summer's wilting humidity might be causing her fits of hacking. But her doctor, Rebecca Bascom, a pulmonologist at the University of Maryland, suggested another possible culprit: air pollution.
"She told me she likes to play tennis in the middle of the day," says Bascom, who treats people with breathing problems. At midday, the smog that fouls Baltimore's summertime air is at its worst, she notes.
To Bascom, smog is a sneak thief of health. Few people realize it may be robbing them of vitality. The symptoms are vague, resembling a cold or flu, and even doctors would tend to treat it as such.
"If you scrape your hand, people would say that's bad," Bascom says. "But we may be scraping our lungs without knowing it."
Two decades after Congress passed the Clean Air Act, federal officials estimate that 133 million people in 96 metropolitan areas, including more than 2 million people in Baltimore, are still breathing unhealthful levels of smog every summer.
The Baltimore area has the eighth worst urban smog problem in the country, according to the U.S. Environmental Protection Agency. That may not be surprising to anyone who sees the yellowish pall that obscures the downtown skyline on sun-baked, windless days.The other "smoggiest" metropolitan areas are Los Angeles, Bakersfield, Fresno, Sacramento and San Diego, all in California; New York, Chicago, Houston and Boston.
Now, as summer fades away, lawmakers in Washington are struggling to agree on new legislation to rid Baltimore, Washington and other metropolitan areas of smog and of another harmful pollutant, carbon monoxide, which poses health problems in colder months.
The measure also would mandate reductions in toxic air pollution and in power-plant emissions that cause acid rain, which research indi-cates is degrading Northeast lakes and the Chesapeake Bay.
Much of the bill's focus, though, is on smog, which has proven to be one of the nation's most intractable pollution problems.
The air here and elsewhere around the country is somewhat cleaner today than it was 20 years ago, thanks to automobile-emission limits and pollution controls imposed on industries as a result of the original clean air law.
But while levels of many air pol-lutants have dropped, smog has been especially tough to eliminate. Auto-emission controls have been largely offset by the growth in traffic during the past decade, and by the use of new blends of gasoline that produce more pollutants through evaporation.
Ozone, the chief component of smog, is formed when sunlight re-acts with hydrocarbons and nitrogen oxides from automobiles, industry and a variety of other sources, such as paints, cleaning solvents and even bakeries.
Though ozone in the upper atmosphere shields people from the sun's harmful ultraviolet rays, ground-level ozone irritates the lungs and reduces their ability to take in air. It also can injure ani-mals and damage crops, forests and man-made materials.
Those most vulnerable to ozone pollution are the elderly, infants and people with chronic breathing problems, such as Brown. But studies have shown that even healthy people can suffer impaired breathing if they exercise or work outdoors when smog is intense.
A recent study by EPA scientists also has found that people exposed to high levels of ozone experienced inflammation of their lower air-ways. The inflammation showed up within an hour of exposure and lasted at least a day, says Dr. Hillel Koren, a researcher at EPA's health effects laboratory in North Carolina.
And, in a newly published study by University of Maryland researchers, allergic people had more and different types of inflammation in their upper respiratory tracts after being exposed to high levels of ozone than did non-allergic subjects in previous ozone studies.
Victims are not easy to find, however. Ozone affects people differently. Some apparently are un-fazed by thick smog, while others are "coughing their brains out," as one EPA scientist put it, after pro-longed exposure to ozone at levels at or below the official health standard of 124 parts per billion.
"We don't know what makes one healthy, normal person more susceptible than the next," Bascom says.
Many may suffer without knowing it. One study of children in summer camps found that they experienced temporary loss of lung capacity without experiencing the usual symptoms of wheezing, coughing, burning eyes and throat and chest pain. Their breathing remained impaired for many days after the ozone episode passed.