Asthma is a chronic disease in which airflow in the lungs is periodically restricted by narrowing of the airways. Asthma attacks are generally caused by environmental factors called triggers. In response to a trigger, a child’s airways become inflamed and constricted, resulting in symptoms of wheezing and/or coughing.

Some children with asthma need medications to control their asthma only when symptoms occur (rescue therapy). Others, who have more severe asthma, must take medication on a regular basis to control their symptoms (maintenance therapy). When their symptoms are particularly bad, these children must also use rescue therapy.

Past research has shown that the risk of asthma symptoms and the need for rescue medication increases significantly when children with asthma are exposed to levels of pollution exceeding those recommended by the Environmental Protection Agency (EPA). Recently, a group of researchers set out to determine the effect of lower levels of air pollution on this vulnerable population.

The results of their study were published in the October 8, 2003 issue of the Journal of the American Medical Association. The researchers found that among children on maintenance therapy for their asthma, exposure to air pollution, even at levels below EPA standards, resulted in a significant increase in respiratory symptoms and need for rescue medication.

About the study

The researchers enrolled 271 children age 12 or younger who had been diagnosed by their physicians as having active asthma. They divided the children into two groups: those who used maintenance therapy and those who did not.

For a period of six months (April 1 to September 30), the researchers examined the number and severity of the children’s daily respiratory symptoms and their level of medication use and compared this data to the levels of environmental pollutants (ozone and fine particles) to which the children were exposed.

The findings

The researchers found that among children who took medication for their asthma on a regular basis, ozone level, but not fine particles, was significantly associated with the severity of the their symptoms and the amount of rescue medication they required. In particular, higher levels of ozone increased the occurrence of wheezing by 35% and of chest tightness by 47%. The highest levels of ozone were also associated with increased shortness of breath and increased use of rescue therapy. Among children who did not use maintenance therapy, the researchers found no significant associations for any pollutant exposure.

Current EPA air quality standards are for 120 parts per billion (ppb) for a one-hour average and 80 ppb for an eight-hour average of ozone and 65 micrograms per cubic meter (µg/m3) for 24-hour fine particles. During the course of the 183-day study, the one-hour standard was exceeded on only three days, the eight-hour standard was exceeded on only 10 days, and the standard for fine particles remained below the current EPA recommendations.

How does this affect you?

The study concluded that children with severe asthma are particularly vulnerable to environmental pollutants such as ozone and fine particles, even at levels below current EPA standards.

Based on these results, it is evident that current EPA air quality standards do not protect the most vulnerable members of our population. Fortunately, air pollution is one of the few environmental triggers for asthma over which we can exercise some control. An editorial published in this same issue of JAMA calls for policy makers and regulatory agencies governing air quality to increase their efforts to reduce emissions that lead to ozone formation and help improve the health of adults and children with asthma. In the meantime, parents of children with moderate to severe asthma should consider keeping their children indoors when conditions outside approach, but do not exceed, EPA standards for poor air quality.

A second study, published in the October 9, 2003 issue of the New England Journal of Medicine followed children from the age of nine until they were 26 years old. It found that approximately 25% of the study participants developed symptoms of asthma in childhood that continued into adulthood. The study concluded that the only way to reduce rates of asthma in adults was to find ways of identifying and treating these children aggressively in childhood. Certainly, improving the quality of the air these children breathe is an essential first step.