A new study brings new revelations about the link between exposure to air pollution in early life and lung health later in life. A research team led by the Keck School of Medicine of USC has shown that exposure to air pollution during childhood is directly linked to symptoms of bronchitis in adulthood.
To date, much of the research in the field has made intuitive connections that are less direct than that: exposure to air pollution early in life is consistently associated with lung problems in childhood – and lung problems in childhood are consistently associated with lung problems as an adult.
The current study, published in the American Journal of Respiratory and Clinical Care Medicineis one of the few to show a direct link between childhood air pollution exposure and adult lung health, a link that is not fully explained by the impact of air pollution on lung health during childhood. It opens the possibility of yet-to-be-understood factors that explain the path from early air pollution exposure to respiratory disease many years later.
The team drew on the USC Children’s Health Study, a large-scale, multi-decade study that followed cohorts of Southern Californians starting in school age and, for many participants, into adulthood. Importantly, the link between childhood air pollution exposure and adult bronchitis symptoms persisted even when the researchers adjusted for asthma or bronchitis symptoms early in life — a finding that came as a surprise.
“We would expect that these observable effects on respiratory health in childhood would explain the relationship between air pollution exposure in childhood and respiratory health in adulthood,” said corresponding author Erika Garcia, PhD, MPH, assistant professor -professor of population and public health sciences at the Keck School of Medicine. “Our results suggest that exposure to air pollution in childhood has more subtle effects on our respiratory system that continue to affect us in adulthood.”
Protecting lung health, now and in the future
The focus on childhood exposure is motivated in part by the fact that children are particularly vulnerable to the effects of air pollution. Their respiratory and immune systems are still developing, and they breathe more air relative to their body mass than adults.
Ultimately, the concern is twofold: for the health of young people today and for their future health as they grow up. Strikingly, among study participants with recent bronchitis symptoms as adults, the average childhood exposure to a pollutant called nitrogen dioxide was well below the Environmental Protection Agency's annual standards — just over half the limit set in 1971 was established and is still in force today.
“This study highlights the importance of reducing air pollution, especially exposure during the critical period of childhood,” Garcia said. “Because we as individuals can only do so much to control our exposure, the need to protect children from the adverse effects of air pollution is better addressed at the policy level.”
The study population consisted of 1,308 participants in the Children's Health Study with a mean adult age of 32 years. The researchers asked about recent bouts of bronchitis symptoms — bronchitis, chronic cough or congestion or mucus production not associated with a cold. A quarter of participants had experienced bronchitis symptoms in the past twelve months.
The presence of bronchitis symptoms was associated with exposure between birth and age 17 to two types of pollutants. One type groups together small particles in the air such as dust, pollen, ash from forest fires, industrial emissions and vehicle exhaust products. The other type, nitrogen dioxide, is a byproduct of combustion in cars, planes, boats and power plants that is known to impair lung function.
Long-term health research proves crucial for fueling discoveries
To provide the most comprehensive analysis possible, average childhood exposure to pollutants was based on month-by-month estimates. At each time point, the researchers linked the household's home address to concurrent local air quality measurements conducted by the EPA and through the Children's Health Study.
“We are fortunate to have this fantastic and nuanced longitudinal study,” Garcia said. “We can learn a lot about how past experiences influence adult health. This is due to the long-term team effort of the participants themselves, their families, the schools they attended, and all the research staff and researchers who conducted interviews and generated and analyzed data. over the years.”
The current study included additional analyses to exclude factors such as prenatal exposure to nitrogen dioxide, current exposure to air pollution as an adult, and the effects of socioeconomic status in childhood or adulthood as drivers of adult bronchitis symptoms.
Pollution exposure in young people can harm lung health more for some than for others
Garcia and her colleagues also found that the effect of exposure to nitrogen dioxide and particulate matter during childhood on bronchitis symptoms in adults was stronger in those who had been diagnosed with asthma as children.
“There may be a subpopulation that is more susceptible to the effects of air pollution,” Garcia said. “We may want to be extra careful to protect them from exposure so that we can improve their outcomes later in life. Reducing air pollution would not only have benefits for current childhood asthma, but also for their respiratory health as they grow into adults.”
She and her colleagues are investigating how the level of exposure to air pollution at different ages during childhood affects respiratory problems as an adult. Other future research directions that build on the results of the current study could include investigating other markers of respiratory health in children and adults, such as how well asthma was controlled, or investigating a potential genetic component.
About this study
The study's co-authors are Zoe Birnhak, Scott West, Steve Howland, Rob McConnell, Shohreh. Farzan, Theresa Bastain, Rima Habre and Carrie Breton, all from the Keck School of Medicine; and Frederick Lurmann and Nathan Pavlovic of the environmental consultancy Sonoma Technology.
This research was supported by the National Institutes of Health (UH3OD023287, P30ES007048).
