But maybe they should. The Southland is heading into its roughest air quality season, when heat, sun, air pollution and smoke from wildfires can cause lung irritation and shortness of breath in even healthy people. Northern California is in the throes of several wildfires that are sending plumes of smoke into the atmosphere, and Southern California has already racked up a few fires, with more likely.
Sure, the South Coast Air Quality Management District offers a daily air quality index available online and in this newspaper, and usually broadcast in television weather reports, but not everyone heeds the agency's advice to stop exercising vigorously outdoors when pollution levels reach "unhealthy." Smog season, according to the agency, spans from May 1 to Oct. 31.
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"I think the public needs a little better education about the seriousness of the potential effects," says Dr. John Balmes, professor of environmental health sciences at UC Berkeley's School of Public Health and a spokesman for the American Lung Assn. of California.
Those effects, which can include coughing, a burning sensation in the lungs and shortness of breath, come from inhaling various particles from smoke and exhaust that make lung tissues swell and airway passages narrow. Brisk exercise exacerbates the effects (when and how severe those are vary from person to person). Because muscles need more oxygen to work, breathing rates increase by about seven times, Balmes says. As a result, the lungs take in and expel double to triple the normal amount of air -- dramatically increasing their exposure to pollutants, says Richard Ford, director of respiratory services at the UC San Diego Medical Center.
This can be especially dangerous for people with coronary artery disease. "Bad things in the air impact the pulmonary system," Ford says. "The only way the body can compensate for lung damage is to increase the heart rate, which means the heart has to work harder." More stress on the heart could result in a heart attack.
What we're breathing is pretty nasty stuff. One component of smog is ground-level ozone, which is "ready to react with virtually anything," according to Balmes (it's different from stratospheric ozone, which protects the planet from harmful ultraviolet rays). That includes the fluid lining of the respiratory tract. "This causes inflammation," he says, "that leads to reduced lung function and respiratory symptoms," although those acute symptoms usually go away. Balmes says there's conflicting evidence on whether permanent damage results from ozone exposure.
Fine particles in the smog also become irritants; those are mostly made up of carbon-based particles from combustion of fossil fuel and output from industrial plants, Balmes says. But those carbon particles don't travel alone -- hitching a ride are polyaromatic hydrocarbons, which have been shown to cause tumors in lab animals and may be a human carcinogen. The carbon-based particles cause damage to lung tissue cells, in turn triggering acute but transitory inflammation.
Ultra-fine versions of those same particles are small enough to enter the circulatory system, Balmes says, but it's not known how toxic they are or how long they stay.
Of course, most jaded Angelenos don't bother to pay too much attention to air quality until they experience symptoms -- or can smell smoke. "People become very aware when there's a fire," Ford says. "They're aware of it because they can see it, but on many days it's bad and people aren't paying attention."
That smoke contains coarser particles, also carbon-based.
"Those particles settle on the sensitive mucous membranes of the nose and throat and act as irritants," says Kenneth Rundell, director of respiratory research in the Human Performance Laboratory at Marywood University in Scranton, Penn., and a fellow of the American College of Sports Medicine. "That's when you sneeze and cough and have watery eyes and a scratchy throat" -- the body's reaction to trying to rid itself of foreign matter.
Smoke can turn a mildly smoggy day into an air quality nightmare. "On a fire day," says Joe Cassmassi, meteorologist and planning and rules manager for the air quality board, "we can see our air quality go from moderate to almost to the point of being hazardous if you're in the proximity of the plume itself."
Jocks take note
Even healthy recreational athletes should pay attention to air quality levels.
The air quality board issues health warnings based on ozone and pollutant levels; an index of 101 to 150 is unhealthy for sensitive groups, which comes with a recommendation that those with heart or lung disease should minimize outdoor activity. An index of 151 to 200 is considered unhealthy, meaning everyone should discontinue prolonged, vigorous exercise outdoors that lasts more than an hour.
Very unhealthy air, with an index of 201 and above, comes with a warning that all vigorous outdoor activity should be stopped.
When the air quality index tops 200, Ford says, "everyone should be more aware. Probably the healthy person is not going to change their habits, but the wise healthy person would. They may come down with minor symptoms and not realize it's because of the air. When it gets above 300, people will start to notice -- they'll cough, have watery eyes, and may have difficulty breathing."
So if the air looks dirty or the air quality board warns about the pollutant level, just take that workout indoors -- to where the air is filtered. Those who have asthma or other ailments should especially heed warnings. If venturing outside, be sure to have medication nearby.
Ozone levels are highest in the afternoon and low in the mornings, so if you can't give up that outdoors exercise, do it early in the day -- and near the coast. The beach will usually have healthier air than inland, since ocean breezes bring fresh air and blow the smoggy stuff farther inland. Of course, on days when westerly winds are scant, smog can hang over the coast as well.
While doing normal activity, breathe through your nose, says Ford, since it provides a natural filtration system for the lungs. But when exercising, go with what feels best, even if that means breathing in and out through the mouth.