In the first study of its kind, researchers have found that improved air quality in southern California had a direct effect on children’s respiratory health. The findings point to the effectiveness of smart public health policy — in other words, even as southern California experienced increases in traffic and commerce, aggressive air pollution policies resulted in cleaner air and healthier kids.
Published earlier this month in the New England Journal of Medicine, the study concluded that air quality improvements in the southern California communities studied were associated with significantly positive effects on lung function growth in children. In even simpler terms, as pollution declined, children’s lungs actually grew stronger.
“The most surprising part was the magnitude of improvements over a relatively short period of time,” study co-author W. James Gauderman, professor of preventive medicine at the University of Southern California (USC) Keck School of Medicine, told me. “It’s really an amazing turnaround to have had these improvements even with increased sources of emissions.”
To conduct the study, researchers measured annual lung function among more than 2,100 children in three different cohorts and during three separate time periods: 1994-1998, 1997-2001 and 2007-2011. The children, who were 11 years old at the beginning of each time period and 15 years old at the end, hailed from the communities of Long Beach, Mira Loma, Riverside, San Dimas and Upland. Lung function growth over the four-year intervals was measured via forced expiratory volume in one second (also known as FEV and defined as the amount of air exhaled in the first second of a forced exhalation) and forced vital capacity (known as FVC and defined as the amount of air exhaled after taking the deepest breath possible). Pollutant levels were gleaned from data collected via outdoor monitoring stations.
Researchers found that lung growth between ages 11 and 15 was more than 10 percent greater for the children exposed to lower levels of nitrogen dioxide from 2007 to 2011 compared to children breathing higher levels of the air pollutant from 1994 to 1998. Also, the percentage of 15-year-old children with abnormally low lung function dropped from about 8 percent within the 1994-1998 study cohort to 6.3 percent in the 1997-2001 cohort to 3.6 percent in the 2007-2011 cohort. Those improvements coincided with the enactment of health-driven air quality policies and vehicle emissions standards, which have produced dramatic air quality results. The study found that combined exposure to two pollutants harmful to human health — nitrogen dioxide and particulate matter less than 2.5 microns (PM2.5) — declined by about 40 percent for the 2007-2011 cohort when compared to the 1994-1998 cohort.
What’s even more impressive is that the positive gains in children’s lung function were documented even after researchers adjusted for confounding variables, such as tobacco smoke exposure, health insurance status, parental educational attainment, asthma and indoor pollutants, such as pets and mold. Indeed, both children with and without asthma experienced better lung function growth as air quality improved. Study authors Gauderman, Robert Urman, Edward Avol, Kiros Berhane, Rob McConnell, Edward Rappaport, Roger Chang, Fred Lurmann and Frank Gilliland wrote:
This study shows an association between secular improvements in air quality in southern California and measurable improvements in lung-function development in children. 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 that all children have the potential to benefit from improvements in air quality.
Gauderman told me that while we’ve known for some time that breathing dirty air is bad for kids via studies that compare polluted and unpolluted communities, this is the first study to start with a polluted community and follows its young residents over time as air pollutants decline. He noted that the study caught kids at a time of rapid lung development. By age 15, lung function development in girls is about finished and boys’ development is slowing down, Gauderman said, and so by the time adolescents transition into adulthood, they have the lungs they’ll have for life. That’s why it’s so important to encourage respiratory health in the early years, as reduced lung capacity and function is a primary risk factor for lung disease in adulthood as well as reduced lifespan. In other words, kids who grow up breathing cleaner air may have a jumpstart on becoming healthier adults, he said.
Gauderman added that among the pollutants studied, declines in nitrogen dioxide and particulate matter, which are products of fuel combustion, were most associated with improvements in kids’ health. And because such pollutants are common in urban areas, Gauderman said similar health improvements could be expected in other communities that pursue stricter clean air policies.
“In an urban environment, you obviously can’t make decisions about breathing the air or not, so it really does take societal decisions to change those exposures,” Gauderman told me. “Given the projections we have for even more cars, more people and more economic activity, we definitely do not want to lose the gains we’ve made. It’s going to take continued vigilance — we certainly don’t want to get complacent as if the job is done.”
Marlon Boarnet, professor and senior associate dean for academic affairs as well as director of graduate programs in urban planning and development at the USC Sol Price School of Public Policy, told me that the children’s lung study is a reminder that air quality protections and a robust economy can coexist. But he added that a strong regulatory regime, political support and decades-long commitment were “absolutely necessary” to achieving the clean air and health gains documented in the study.
“This was absolutely a result of public policy, there’s no question about it — end of story,” he said. “This would not have happened without policy. …If you want to have reduced lung capacity in our children, then by all means, leave it to the market.”
To read a full copy of the children’s lung study, visit the New England Journal of Medicine.
Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.