Oct. 7, 2003 -- Even days deemed "safe" by the EPA for having lower-than-average levels of air pollution can cause breathing problems in children with asthma who need regular medication to control it.
A new study shows that those children have an increased rate of respiratory symptoms -- and greater need for medications -- even on days with lower levels of EPA air quality standards. Ozone, the harmful gas resulting from car exhaust, gasoline vapors, and other pollutants, was found to be associated with an increase in reported asthma symptoms and medication use. Symptoms worsened as ozone levels climbed higher, though levels were still in the "safe" zone.
However, no additional problems were seen on these low-level days in children with asthma who don't require maintenance drugs.
Theoretically, this makes sense because children with asthma who require maintenance drug therapy are those that require daily therapy to prevent (rather than treat) an attack and typically have more severe disease and are more vulnerable to attacks. But previous findings indicate that maintenance medications such as inhaled steroids seem to protect from attacks caused by air pollution.
Additionally, the new findings suggest that federal guidelines predicting a comfortable measure of respiratory safety on low-ozone days in children with asthma may not be as safe as previously believed.
"Parents should interpret this as an alert," lead researcher Janneane F. Gent, PhD, tells WebMD. "Kids with more disease who require drugs for their asthma should consider low levels of ozone as a problem. On those days, they should be kept inside whenever possible, with windows closed and the air conditioner on, and reduce their activity levels."
But another expert not connected with the study says that indoor triggers may aggravate childhood asthma even more.
"Basically, the stuff indoors can be worse than what is outdoors," says Nathan Rabinovitch, MD, a childhood asthma specialist at the National Jewish Medical and Research Center in Denver. "If there's tobacco smoke indoors or there are indoor allergens like dogs and cats, it may cause even more of the problem. It's really important to know what triggers asthma attacks in your child."
Rabinovitch expressed surprise at Gent's findings, published in this week's issue of TheJournal of the American Medical Association.
"Other studies have shown the opposite effect -- that people who take asthma maintenance medications like inhaled steroids have fewer symptoms and pulmonary dysfunction from ozone compared to people who don't take maintenance drugs," he tells WebMD. "That's because the drugs are doing their job -- and why we tell people to take their medications."
Focus on Ozone
Gent's study measured respiratory symptoms, such as wheezing, persistent cough, chest tightness, and shortness of breath in 271 asthmatic children under age 12 during the spring and summer. The asthmatic children taking maintenance medication seemed to react specifically to ozone but not to other sources of pollution.
"What's interesting about our report is we happened to study the children during the summer, when fine particles weren't really a player -- there wasn't a single day when fine particle levels were anywhere near high levels," says Gent, of Yale University's Center for Perinatal, Pediatric, and Environmental Epidemiology. "So this was a chance to specifically look at ozone."
One explanation: Fine particle pollutants result from the burning of coal, wood, and oil, releasing tiny particles invisible to the eye that are usually found in smoke or haze. Since they largely come from heating fuels, fine particles are usually higher in the winter. However, ozone is often worse in the summer because sunlight and hot weather form it and increase its concentration in the air.
However, her study did not examine the specific maintenance medications the children were taking.
The bottom line: "Patients and parents of children with asthma should be aware of the ozone alert forecast, which is widely publicized in news reports," write George D. Thurston, ScD, and David V. Bates, MD, in an accompanying editorial.
"Of the many triggers of asthma in the environment, air pollution is one of the few that can be legislated and regulated. Therefore, policy makers and regulatory agencies governing air quality necessarily have an important responsibility in ensuring that greater efforts are made to clean the air by reducing the emissions that lead to ozone formation, thereby helping to improve the health of adults and children with asthma."