Smog Study of Children Yields Ominous Results
Air pollution in Southern California appears to have subtle long-term effects on children’s lungs and may cut into girls’ breathing capacity more than boys’, according to early results from the most comprehensive study ever undertaken in the region.
Findings from the first year of a 10-year smog study by USC researchers suggest that high smog levels most markedly restrict the wind of girls who spend a lot of time outdoors.
Boys, on the other hand, are more likely to develop respiratory illnesses, as are children of either sex who live in houses with indoor pollution caused by pets, pests, mildew and water damage or cigarette smoke.
While impaired breathing capacity--reduced volume or flow of air in the lungs--can leave children vulnerable to respiratory disease and underdeveloped lungs, it is not the same as an illness like asthma or bronchitis. Why boys would be more prone to such diseases is unclear, said the researchers, who published their preliminary data today in the American Journal of Respiratory and Critical Care Medicine.
“It’s not good news,” said Helene Margolis, an epidemiologist with the California Air Resources Board, principal sponsor of the $16-million research.
The study, which began in 1993, is one of the few to focus on pollution’s long-term effects on children--a population considered especially vulnerable because they spend so much time exercising and out of doors.
Of unprecedented scope, it involves more than 3,600 children in the fourth, seventh and 10th grades in 12 communities in the southern half of the state. A wide mix of communities was selected, from those with relatively clean air, such as Santa Maria and Atascadero, to more smoggy cities like Upland and San Dimas.
The initial findings are based on questionnaires and lung function tests. Researchers plan in the future to also include school absences.
Unpublished results from later years in the study, which researchers reported to the Air Resources Board in January, suggest that the link between high levels of pollution and chronic respiratory problems holds steady over a period of several years.
It is the promise of finding such long-term patterns that most intrigues pollution experts.
“That will be unique” to this study, said David Bates, a professor emeritus of medicine at the University of British Columbia who has advised USC researchers on their approach. “Everyone will be interested in that.”
The preliminary findings of chronic lung effects on children come in the wake of another alarming--but unrelated--study this month showing that despite the Los Angeles Basin’s improved air quality, residents still are breathing unusually dangerous levels of cancer-causing toxins produced mainly by motor vehicles.
The children’s study, by contrast, focused on more commonplace byproducts of vehicles and industrial emissions--ozone, microscopic elements known as particulates, nitrogen dioxide and acid vapors. The immediate effects of such substances have been well-studied but their long-term impact on youngsters remains somewhat of a mystery.
Although billions of dollars are spent in this region each year to fight smog on the assumption that dirty air has short- and long-term health effects, Southern California still exceeds federal and state health standards for ozone and particulates, researchers said.
Yet one of the study’s surprising findings was that “ozone was not the big hitter,” said Dr. Morton Lippmann, professor of environmental medicine at the New York University School of Medicine and a member of the study’s advisory board. “The fine particles and acid and nitrogen dioxide seemed to be playing a bigger role.”
That was striking because other studies have shown that ozone--formed when hydrocarbons and nitrogen oxides react with sunlight--is more clearly associated with short-term ill effects of pollution such as shortness of breath, chest pain and watery eyes.
Most remarkable in the first year’s findings were consistent, but as yet unexplained, gender differences.
“There is [not just] a difference between boys and girls; there is a difference between the pollutants most affecting boys and girls,” Margolis said.
Researchers clearly linked elevated pollution levels to reduced breathing capacity in girls. Nitrogen dioxide and particulates apparently were the greatest culprits, although high ozone exposure played a significant role in girls with asthma.
Boys’ breathing capacity was affected by high ozone exposure too, but only in those who spent a lot of time outdoors.
Boys tended to be more affected by respiratory illnesses. In their case, wheezing was linked to nitrogen dioxide and acid vapor.
But researchers noted that although boys initially suffered more from asthma, girls essentially caught up with them in that regard by the time they reached high school.
Researchers hope to tease out the reasons for the gender differences as the study progresses. Possible explanations include variations in boys’ and girls’ lung volume and airflow, growth rates and hormonal effects.
There were other findings that stumped researchers. For example, they could not explain why the incidence of excessive respiratory disease did not correlate with the highest levels of outdoor air pollution. This contrasts with the separate finding of girls’ reduced lung capacity in highly polluted areas.
Whatever the answer, the investigators say the findings underline the importance of indoor pollutants such as mildew and cigarette smoke. Researchers argued for “a broad-based campaign to abate airborne hazards inside homes.”
Other remaining challenges are to determine which pollutants are responsible for which physiological effects and how pollution affects asthma.
Whether reductions in lung capacity and aggravated respiratory illnesses will translate into lifelong health problems remains an open question, but such findings in the young do not bode well, researchers said.
“This is just a snapshot. . . . The real answer is going to come from finishing this study,” said Dr. John M. Peters, lead author of the research.
Peters said the children will be followed for eight years, with the final two years reserved for analysis--meaning that the fourth-graders’ health will be studied at least through high school.
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Breathing Problems
Asthma is more prevalent among boys than girls until the high school years, according to a study of respiratory disease-prevalence rates among Southern California children.
Boys
*--*
Severe Grade Asthma Asthma Wheeze Bronchitis Cough Pneumonia 4 17% 9% 25% 14% 8% 2% 7 17 12 22 14 6 2 10 16 8 21 11 8 1
*--*
Girls
*--*
Severe Grade Asthma Asthma Wheeze Bronchitis Cough Pneumonia 4 9 5 22 11 5 2 7 13 7 22 12 8 1 10 16 7 26 15 8 2
*--*
Both genders
*--*
Severe Grade Asthma Asthma Wheeze Bronchitis Cough Pneumonia 4 13 7 23 13 7 2 7 15 10 22 13 7 2 10 16 8 23 13 8 1
*--*
Source: American Journal of Respiratory and Critical Care Medicine
