Smog Blamed for an Increase in Asthma Cases
Researchers who conducted separate studies in New York, Connecticut, New Jersey and Georgia think they’ve found one explanation for the national upsurge in asthma, and that reason is smog.
For papers slated for presentation soon at medical conferences and in journals, they charted hospital visits, hospital admissions and asthma symptoms. In each case, they demonstrated that asthma got worse when the air showed higher levels of ozone--a sharp-smelling, colorless gas that is the main component of smog.
The conclusions reached at various locations by different investigators “are good evidence of what many physicians who actually talk with patients have been worried about for a long time,” said Thomas J. Godar, a former president of the American Lung Assn. who treats pulmonary patients in Hartford, Conn. “Not everyone has been willing to admit this. I think that sort of information will have a lot of clout.”
Asthma, a chronic inflammation of the airways, affects an estimated 9.9 million people in the United States, among them disproportionate numbers of children, blacks and the poor. Its prevalence and severity appear to be steadily rising, a development that alarms health professionals. Similar increases have been noted in other countries, including Canada, Great Britain, France, Denmark and Germany.
George D. Thurston, an assistant professor of environmental medicine at New York University, found that asthma admissions to 87 hospitals in New York City and 35 in Buffalo increased by 25% to 30% on the days that ozone levels were highest during the summer of 1988.
This past summer, he logged ozone levels and the number of asthma attacks every day during a weeklong camp for asthmatic children in the Connecticut River Valley. He discovered “a strong association,” he said. On days when ozone concentrations were above the federal standard of .12 parts per million, he said, there were 30% more asthma attacks than on days when the pollution was below the standard.
He expects to present his findings in May to the American Thoracic Society.
Similarly, Mary C. White, an epidemiologist at the Centers for Disease Control in Atlanta, found that asthma cases increased by a third on high-ozone days--defined in her study as above .11 parts per million--at the pediatric emergency clinic of an Atlanta public hospital. She based her findings on a study of 609 visits to Grady Hospital during the summer of 1990.
Paul J. Lioy, a professor of environmental and community medicine at the Robert Wood Johnson Medical School in Piscataway, N.J., found that 7% to 10% of asthma admissions at nine hospitals in north-central New Jersey were related to ozone in the summers of 1988 and 1989. He is revising a report on his work for the journal Environmental Research.
Plans are also under way for a study next summer in the nation’s smog capital, Los Angeles. The state hopes to monitor 150 asthmatic minority children here, said Bart Ostro, who heads the air pollution epidemiology unit for the California Environmental Protection Agency. He said researchers will log the frequency of children’s physician visits, their wheezing and coughing and medication use. They also will measure lung function.
“If you’re going to find an effect, you’re going to find it in L.A.,” Ostro said.
Although the amount of ozone in the Los Angeles skies has been declining over the past decade, the air still contains more ozone more often than anywhere else in the United States. From May to September this year, federal ozone standards were violated on 107 days in the four counties under the jurisdiction of the South Coast Air Quality Management District.
Ozone is formed when pollutants from cars, paints, factory stacks and consumer products mix and bake in the sun. Stagnant air, which peaks in the summer months, traps the ozone close to the ground, keeping it from being diluted in the upper atmosphere.
The chemical is a powerful lung irritant. Recent studies have linked ozone to impeded lung development and to permanent lung damage.
Ozone is thought to inflame air passages--and swollen airways are one symptom of asthma.
“As long as 15 or 20 years ago, my patients would describe leaving Connecticut to go to Vermont for the weekend,” Godar said. “They would get to Vermont and discover they needed almost none of their medication. Driving back, halfway through Massachusetts they would feel the wheeze coming back.
“I heard three or four of these (cases) independently and it became very clear to me that they were responding to pollution. But this was all anecdotal.”
Earlier research had raised suspicions that smog might be a factor in causing or worsening asthma. But one study did not take into account the proper use of medication and another did not isolate ozone from other pollutants, such as sulfates, which are more common on the East Coast than in the West, Ostro said.
The spate of recent studies “is making use of better air-monitoring information,” Ostro said. “And there’s a weight-of-evidence argument. After you see more and more studies showing relatively similar effects, it is harder to reject them.”
The researchers note, however, that ozone is clearly not the only cause of increased asthma. “But air pollution happens to be something we can do something about,” Thurston said.
In his New York state study, which also included hospitals in the Albany and White Plains areas, Thurston found stronger links between ozone levels and asthma in cities than in the suburbs. “The people in the suburbs are being stressed by air pollution and there was still an association,” he said, “but the urban cores seemed to have the greatest correlation.”
He said he can only speculate as to why inner-city asthmatics appeared more sensitive to ozone. “Perhaps there’s a difference in racial sensitivity. Perhaps it’s the health care that they get, because they don’t have health insurance,” he said. “Perhaps it’s nutrition.”
Other explanations for the increase in asthma include better diagnoses than in the past, changes in temperature and a recently identified microorganism, chlamydia pneumoniae.
“Ozone is just one of the participants,” Lioy said. “It may be a synergism that’s more important.”
For example, a Canadian study published in the July 27 issue of The Lancet suggests that ozone can increase the lung’s responsiveness to allergens, such as ragweed or grass.
Based on the recent research, Godar recommended that, during periods of high ozone, asthmatics “should be inactive, stay inside (and) use air conditioning.”