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Improved air quality aids children's lung function
Long-term improvements in air quality benefited lung-function growth among children in Southern California, according to study findings in the New England Journal of Medicine.
“Adverse effects of air pollution on the lungs in childhood can potentially have long-term effects,” study researcher W. James Gauderman, PhD, professor of preventive medicine at the Keck School of Medicine, University of Southern California, Los Angeles, and colleagues wrote. “Although progress has been made throughout the United States to reduce outdoor levels of several air pollutants, it is not known whether these reductions have been associated with improvements in children’s respiratory health.”
Researchers measured lung function in 2,120 children from three study cohorts representing three calendar periods. Two cohorts enrolled fourth-graders in 1992 to 1993 and 1995 to 1996, respectively. The third cohort enrolled children in kindergarten and first grade in 2002 to 2003. Pulmonary function testing was conducted annually from fourth to 12th grades or every other year, at ages 11, 13 and 15 years. Regional air pollutants were tracked by monitoring stations in each study community since 1994.
Regional air quality significantly improved during the study, according to researchers. Mira Loma, the community with the highest levels of particulate matter, experienced a 43% reduction in the 4-year mean PM2.5 level. All communities experienced significant declines in nitrogen dioxide and PM2.5. PM10 and ozone changed moderately.
Among girls, the mean forced expiratory volume in 1 second (FEV1) increased from 2,274 mL at age 11 years to 3,150 mL at age 15 years, a mean 4-year increase of 876 mL.
The mean 4-year increase for boys was 1,520 mL in FEV1; from 2,311 mL at age 11 years to 3,831 mL at age 15 years.
Increases in FEV1 and forced vital capacity (FVC), which showed similar improvement, were associated with reduced levels of nitrogen dioxide, PM10 and PM2.5. This association remained true in sensitivity analyses. Sensitivity analyses further indicated air pollution had a greater effect on FEV1 (P = .04) and FVC (P =.001) among boys compared with girls.
Nitrogen dioxide affected increases in FEV1 and FVC among children with asthma almost twice as much as children without asthma, but the difference was not significant.
“This study shows an association between secular improvements in air quality in Southern California and measurable improvements in lung-function development in children,” the researchers wrote. “Improved lung function was most strongly associated with lower levels of particulate pollution (PM2.5 and PM10) and nitrogen dioxide.
“These associations were observed in boys and girls, Hispanic white and non-Hispanic white children, and children with asthma and children without asthma, which suggests all children have the potential to benefit from improvements in air quality.”
Disclosure: Gauderman reports no relevant financial disclosures. McConnell reports financial ties with South Coast Air Quality Management District, a California state regulatory agency and BP.
Perspective
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This study demonstrates unequivocally that improvement of outdoor air pollution, capping emissions from cars and factories, has a positive effect on lung function in children, and by extension, adults with asthma as well as adults with other respiratory diseases.
There has always been an association between outdoor pollution and the worsening of asthma. Since I started in 1972 (in terms of my involvement with asthma) when ozone levels were high there was an association of increased emergency room visits and hospitalizations related to the worsening of outpatient asthma. Instead of doing cross-sectional studies, looking at emergency room visits and what the pollution count was, researchers in this study examined not just ozone but also other emissions that come from cars and trucks.
What the researchers were looking at was overall improvement in pulmonary function in children, both with and without asthma from 1994 to 2011, which showed that there is a significant increase in the measures of spirometry, a very important parameter of airway obstruction correlated with asthma severity. The study demonstrated that there was a direct correlation with a reduction in air pollution and an improvement in pulmonary function.
The important thing to note is that there was a positive change in pulmonary function, not only among asthmatics, but also among normal children. The message here is that we should continue to restrict emissions, not just in California but nationwide, which would not only have a significant positive effect on patients with asthma but also those with COPD.
