Smog hurts boys, girls differently, south state study finds
By Chris Bowman
Bee Staff Writer
(Published Feb. 4, 1999)
The nation's first comprehensive look at the health effects of air pollution on children has an unexpected find: Boys respond differently than girls to common air pollutants.
Not as surprising, but perhaps more critical, results from the first four years of the University of Southern California study also show lung growth about 5 percent lower among children living in America's smoggiest communities, compared with their peers in cleaner environments.
Children with weaker lungs are more prone to colds and coughs and are more likely to develop chronic respiratory diseases as adults, health experts say.
Though the $15 million investigation is confined to Southern California, the trends suggest that youths growing up in the nation's other smoggy regions like Sacramento, Houston and Philadelphia are at greater health risk, California air pollution officials said.
"Any of the long-term, adverse effects seen in Los Angeles are likely to be observed in other dirty cities as well," said Helene Margolis, who oversees the study for the state Air Resources Board, California's pioneering smog-fighting agency. "They are the same pollutants, somewhat lower but not a lot."
Members of the air board, who recently got a preview of the state-funded study, said the findings reinforced their resolve to keep tightening California pollution controls on industry and automobiles, which are already the toughest and most controversial in the nation.
An investigation of the long-term health effects of air pollution on Southern California children is yielding some surprising results. The $15 million state-funded study tracks the respiratory symptoms, breathing capacity and school absenteeism among children in the 4th, 7th and 10th grades. Here are some of the key preliminary findings:
Boys and girls are responding differently to certain common air pollutants.
Wheezing in boys increases in communities with higher levels of nitrogen oxides of nitrogen, or NOx, a smog-forming pollutant.
Breathing capacity in girls diminishes in communities with higher levels of NOx and tiny particle pollutants, such as diesel soot.
Breathing capacity in boys spending more time outdoors and in girls with asthma diminishes in communities with higher levels of ozone gas, the main component of smog.
Lung growth in children is about 5 percent lower in the most polluted communities.
Coughing and wheezing among asthmatics increases dramatically in communities with higher levels of NOx and particle pollution.
Childrens exposure to smog is reduced by at least 40 percent when they move indoors. Air conditioning and carpets further reduce exposure.
Contrary to expectations, NOx and particle pollutants appears to be at least as harmful to children as ozone gas.
Source: California Air Resources Board
"If they turn out to be correct, these provocative findings are going to remove the arguments that we should leave things (air pollution controls) the way they are," said board member William Friedman, a pediatrician and academic dean at the University of California, Los Angeles, medical school.
"I am very gratified . . . that children, whom we give a lot of lip service to, are participating in a study that will help them and eventually everybody's children," Friedman said.
The study, commissioned by the Air Resources Board in 1991, has drawn interest around the world because it is one of the few such investigations that focuses on a young population and tracks its respiratory health over several years.
The team of USC researchers will have followed 5,000 children at 52 schools over the course of nine years, from 1993 through 2001. Analysis of the data will take another two years.
The study is tracking respiratory symptoms, breathing capacity and school absenteeism among children in the fourth, seventh and 10th grades -- ages 9 to 18 -- in a dozen Southern California cities.
Not surprisingly, researchers said, the study shows children living in the relatively cleaner coastal Santa Barbara and San Luis Obispo counties faring better than their peers in the smoggier San Gabriel Valley and farther inland to Riverside and San Bernardino counties.
Nor is it surprising that coughing and wheezing among asthmatics increases dramatically in communities with higher levels of nitrogen oxides, or NOx, and particle pollution, researchers said.
But the scientists did not expect that children's gender would make any difference.
"This is something no one has observed before," said Jerry Martin, an air board spokesman. "But there have been very few such studies that have concentrated on children."
The study shows a pronounced increase in wheezing among boys living in communities that are more heavily polluted with NOx, a smog-forming contaminant that turns the sky brown and comes mainly from vehicle exhaust.
And girls, more than boys, had lower breathing capacity in areas with higher levels of NOx and tiny particle pollutants, such as diesel soot.
"When we looked at lung function, we were again surprised," John Peters, the lead USC researcher, told the air board.
Peters' team also found lower lung volumes among girls with asthma and boys who spent more time outdoors in communities with higher levels of ozone gas, the main component of smog.
Peters did not offer an explanation for the difference in health effects between boys and girls; the researchers have considerable more testing and analysis to conduct.
The study also found that the children's exposure to harmful ozone is reduced by at least 40 percent when they move inside classrooms, validating school policies that call for keeping pupils indoors during smog alerts.
Ozone kills cells and causes structural changes in the deep lung, inviting respiratory illness that can cause further damage.
But, contrary to researchers' expectations, NOx and particle pollutants appear to be at least as harmful to children as ozone gas, Peters told the board.
This comes as good news to California air pollution regulators who began cracking down on NOx long before the rest of the country. Those controls kicked in as early as 20 years ago on vehicles sold in California and have accelerated ever since.
"Our policies have probably resulted in less damage to kids, and the findings of the USC study certainly give us reason to continue in that direction," Martin said.
Board member Friedman said one of the benefits of studying children is that the results are not confounded by effects of long-term smoking and exposure to pollutants on the job as experienced with adults.
The investigation also departs from previous air pollution studies that have focused mostly on the effects of short-term exposure -- a few hours or less -- to relatively high concentrations of pollutants.
In the remaining years of the study, Peters said, researchers hope to better link specific pollutants with health effects and look more closely at more localized effects, such as living next to freeways.
The study is scheduled to continue through June 2003. Its preliminary findings are to be published in March in The American Review of Respiratory and Critical Care Medicine, Peters said.
Air board members said they hoped the USC researchers will find other financial backers to continue following the study group into early adulthood to learn whether smog continues to stunt lung growth.