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As Air Pollution Declines, Kids Breathe Better
[2015-03-06]
by Molly Walker
Contributing Write
LAST UPDATED 03.06.2015http://www.medpagetoday.com/Pediatrics/GeneralPediatrics/50321
Lung function improved in tandem with air quality in California children entering their teen years.
Improvement in older children's lung function was seen in conjunction with declines in ambient air pollutant levels, according to combined results from three population-based, longitudinal studies in Southern California.
Among children with mean age 11 at enrollment and followed over the course of 4 years in three separate epochs going back to the mid-1990s, maximal forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) both increased significantly in correlation with declining levels of nitrogen dioxide (P<0.001 for FEV1 and FVC) and particulates smaller than 2.5 mcm or PM2.5 (P=0.008 for FEV1 and P<0.001 for FVC), reported W. James Gauderman, PhD, a preventive medicine specialist at the University of Southern California in Los Angeles, and colleagues in the New England Journal of Medicine.
"When the effects were averaged across communities, we found that the mean 4-year growth in FEV1 increased by 91.4 ml per decrease of 14.1 ppb in nitrogen dioxide level (P<0.001), by 65.5 ml per decrease of 8.7 mcg per cubic meter in PM10 [particulates smaller than 10 mcm] level (P<0.001), and by 65.5 ml per decrease of 12.6 mcg per cubic meter at PM2.5 level (P=0.008)," the authors wrote.
The study also examined ozone concentration changes, but found no association with lung function.
Improvements varied by demographic group, as boys were associated with a higher mean 4-year growth in FEV1 (1520 ml) than girls (876 ml), with FVC showing similar results. Both Hispanic and non-Hispanic white children also experienced "lung-function growth" due to pollution effects. But while declining levels of nitrogen dioxide were associated with a larger increased 4-year growth in FEV1 in children with asthma, the authors said it was not a significant difference in lung function measure compared with children without asthma.
Researchers saw an increase in the number of children with healthier lung function over the three study periods (1994-1998, 1997-2001 and 2007-2011). "The proportions of children with clinically low FEV1 (defined as <80% of the predicted value) at 15 years of age declined significantly, from 7.9% to 6.3% to 3.6% across the three periods as the air quality improved (P=0.001)," they wrote.
In California, nitrogen dioxide, PM2.5, and PM10 are mainly found in motor vehicle emissions, and researchers said that stricter emission standards in the state have likely contributed to the decline in these pollutants.
Peter Thorne, PhD, professor and head of occupational and environmental health at the University of Iowa College of Public Health in Iowa City, who was not affiliated with the study, said this study "provides convincing evidence that reducing ambient air pollutants such as nitrogen dioxide and fine particulate matter improves lung function growth during adolescence."
"Very Important Policy Implications"
Susanna McColley, MD, division head, pulmonology at Lurie Children's Hospital in Chicago and professor of pediatrics at Northwestern University Feinberg School of Medicine, noted that given that poor air quality is associated with worse lung health and with exacerbations of chronic diseases like cystic fibrosis and asthma, its overall impact may be even greater. "Improving air quality not only reduces illness, but promises to improve health," she said. "This has very important public policy implications."
As part of the Children's Health Study in California, researchers examined three separate 4-year cohorts in the communities of Long Beach, Mira Lorna, Riverside, San Dimas, and Upland. Children in the study were given a pulmonary function test, and a parent or guardian filled out a health questionnaire. Of the 2,120 children participating, 74.8% completed a pulmonary function test at the beginning and end of the study and were included in the current analysis.
The sample comprised 52% girls, with one cohort containing a greater proportion of Hispanic children as well as a lower exposure to passive smoke and pets and a higher proportion of parents with health insurance compared with the other two cohorts.
Gauderman and colleagues noted the demographic shift in Southern California to a more Hispanic population over the course of 13 years, and said that could potentially be an ethnic background confounder. They also acknowledged that the study was observational and lacked a "control group" for whom air pollution remained unchanged.
Another limitation was that air pollution data came from community-level monitors that may not reflect the actual exposures of individual children in the cohort.
Shipra Singh, MD, MPH, assistant professor, pediatric pulmonology, State University of New York at Buffalo School of Medicine and Biomedical Sciences, Women and Children's Hospital of Buffalo, pointed out yet another limitation of the study. "They haven't reported the forced expiratory flow between 25% and 75% of forced vital capacity (FEF25-75), which is thought by many to be a more sensitive indicator of small airways disease," she said. "It would be interesting to see the trends in FEF25-75 predicted."
Though change in ozone was not associated with any significant improvements, Thorne wondered if it might be worth exploring in a future study. "This study lays the foundation for future investigations of the effects of ozone on children's health as the U.S. strives to bring ozone levels down in our major cities," he said.
The authors concluded that nitrogen dioxide, PM2.5, and PM10 were "among those effectively reduced through targeted policy strategies," which leads to a "not-unreasonable assumption of causality" on the improvements in children's lung function.
But McConnell urged caution when interpreting the results, adding that other factors improving lung health may not have been measured.
"Exposure to air pollution and other environmental and social factors that can affect lung function tend to be local (for example, some neighborhoods in my home city of Chicago have better air quality than others), so we are not sure that all children are benefiting equally from reductions in air pollution," she said.
The study was supported in part by contracts with the Health Effects Institute and the California Air Resources Board and by grants from the National Institute of Environmental Health Sciences.
Dr. McConnell reports holding a research contract from funds from an air-quality-violations settlement between the South Coast Air Quality Management District, a California state regulatory agency, and BP. No other potential conflicts of interest relevant to this article are reported.
Discussant Peter Thorne, PhD, reports he has previously collaborated with study authors on research 8 to 10 years ago.
