LOS ANGELES - Air pollution could be causing emphysema, even in people who have never smoked, a study published Tuesday in the journal JAMA found.
A long-term increase of just three parts per billion of ground-level ozone (O3) — which is considered by the Environmental Protection Agency to be the “main ingredient in smog” — outside a person’s home opens them up to a level of lung damage that is effectively the same as that which would occur after smoking a pack of cigarettes every day for 29 years.
Air pollution has historically been associated with cardiovascular and respiratory diseases, but connections between long-term air pollution exposure and emphysema, which has long been thought of as a smoker’s disease, have been unclear.
The new cohort study monitored the progression of lung damage in relation to air pollution exposure for 6,860 adults living in six specific metropolitan areas of the U.S. — Chicago, Los Angeles, Baltimore, St. Paul, Minn., New York City and Winston-Salem, N.C. — between 2000 and 2018. On average, participants in the study were exposed to concentrations of 10-25 parts per billion of ground-level ozone annually outside their homes.
All participants underwent a baseline CT scan at the beginning of the study to determine lung health, and they were assigned an outdoor residential air pollution concentration, which served as a measure of the types and amounts of air pollution outside their homes. Researchers were interested in levels of ambient ozone (O3), fine particulate matter (PM2.5), oxides of nitrogen (NOx) and black carbon.
Downtown Los Angeles with an inversion layer of smog. (Ted Soqui/Corbis via Getty Images)
In 2000 when baseline measurements were taken, 46 percent of all participants were lifelong non-smokers.
Over the course of the study, participants underwent up to five additional CT scans to monitor the changes that occurred in their lungs, and researchers periodically measured the amount of air pollution around the participants’ homes.
Researchers found that greater exposures to ground-level ozone, particulate matter and oxides of nitrogen assessed at study baseline, to black carbon averaged through 2006 to 2008, as well as to ground-level ozone and oxides of nitrogen throughout the follow-up period of the study were all significantly associated with an increased progression of emphysema over 10 years. Out of all the pollutants, ground-level ozone had the most significant impact.
Ground-level ozone is a powerful oxidizing agent and is a common air pollutant all over the world. In this study, ground-level ozone was the only air pollutant determined to have a significant association with the decline in lung function.
“Because long-term concentrations of O3 at current levels were strongly and consistently associated with both progression of emphysema and decline in lung function in this study, more effective control strategies to reduce O3 concentrations may be needed to protect lung health,” the study concludes.