Air pollution - especially ozone air pollution, which is increasing with climate change - can speed up lung disease as much as a pack a day of cigarettes.
According to researchers, long-term exposure to all major outdoor air pollutants, especially the pollutant ozone, increases the development of chronic lung disease emphysema, and age-related decline in lung function, even among people who have never smoked.
Emphysema is a condition in which destruction of lung tissue leads to wheezing, coughing, and shortness of breath, and increases the risk of death.
Ambient ozone exposure, but not the other pollutants, was associated with a decline in lung function. The increase in emphysema observed by the team was relatively large, similar to the lung damage caused by 29 pack-years of smoking and three years of aging, says the study published in the Journal of the American Medical Association (JAMA). One pack-year is equal to smoking a pack a day for a year, explains the research team from the University of Washington, Columbia University and the University at Buffalo.
“Increasingly, it is recognized that chronic lung diseases like emphysema occur in non-smokers, and rates of these diseases are continuing to increase. We really need to understand what’s causing chronic lung disease, and it appears that air pollution exposures that are common and hard to avoid might be a major contributor. Ozone concentrations are increasing as a result of climate change and fossil fuel use - these are things that need to be addressed by changes at the community, national, and global scale in order to prevent health impacts like these,” the study’s senior co-author, Dr. Joel Kaufman from the University of Washington professor of environmental and occupational health sciences and epidemiology in the School of Public Health, told MEA WorldWide (MEAWW).
Dr. Kaufman further says, “We were surprised to see how strong air pollution’s impact was on the progression of emphysema on lung scans, in the same league as the effects of cigarette smoking, which is by far the best-known cause of emphysema.”
The results are based on an extensive, 18-year study involving more than 7,000 people (45 to 84 age group) and a detailed examination of the air pollution they encountered between 2000 and 2018 in six metropolitan regions across the US — New York City, Chicago, Baltimore, Los Angeles, St. Paul, and Winston-Salem.
According to the researchers, chronic lower respiratory disease -- a catchall term for emphysema, chronic obstructive pulmonary disease (COPD), chronic bronchitis, and asthma -- is the fourth-leading cause of death in the US and the third-leading cause of death worldwide.
While short-term exposure to air pollutants is a major risk factor for poor lung health, the long-term effects of air pollutants on the lungs have not been well understood until now.
The study, the largest and longest of its kind, looked at whether exposures to four major pollutants - ground-level ozone, fine particulate matter (PM), nitrogen oxide, and black carbon - were associated with the development of emphysema, measured by CT scan, and decline in lung function, measured by spirometry.
The research team estimated the levels of outdoor air pollutants at each participant’s home.
The researchers found that exposure to each of the pollutants at the beginning of the study was independently linked to the development of emphysema during the study period.
The strongest association was seen with ozone. Only ozone, at baseline and during follow-up, was associated with a decline in lung function.
Ambient concentrations of fine particulates and nitrous oxide, but not ozone, decreased significantly over the study period, says the study. Ground-level ozone is mostly produced when ultraviolet light reacts with pollutants from fossil fuels.
“Living in areas with higher levels of air pollution is associated with faster development of emphysema-like changes in the lung on repeated chest CT scans over up to 18 years of follow-up,” Dr. Kaufman told MEAWW.
Further explaining their findings, the researchers state, if the ambient ozone level was three parts per billion (ppb) higher where one lived compared to another location over 10 years, that was associated with an increase in emphysema, equivalent to smoking a pack of cigarettes a day for 29 years.
The study determined that ozone levels in some major US cities are increasing by that amount, due in part to climate change. The annual averages of ozone levels in study areas were between about 10 and 25 ppb.
The findings could help explain why emphysema is relatively common in non-smokers.
The participants were drawn from the Multi-Ethnic Study of Atherosclerosis Air Pollution (MESA Air) Air and MESA Lung studies.
The study involved a state-of-the-art analysis of more than 15,000 CT scans repeated on thousands of people for 18 years.
Emphysema was measured from CT scans that identify holes in the small air sacs of the participants’ lungs, and lung function tests, which measure the speed and amount of air breathed in and out.
“Emphysema is a very serious disease. Chronic lower respiratory disease is the third leading cause of death worldwide. Most of this mortality is due to chronic obstructive pulmonary disease (COPD), which is what we are studying here - it is a disease characterized by destruction of the lung tissue, and what we see on scans are more holes in the lung,” Dr. Kaufman told MEAWW.
“This study adds to growing evidence of a link between air pollution and emphysema. A better understanding of the impact of pollutants on the lung could lead to more effective ways of preventing and treating this devastating disease,” says James Kiley, director of the Division of Lung Diseases at the National Heart, Lung, and Blood Institute, part of the National Institutes of Health.
According to the research team, these findings matter since ground-level ozone levels are rising, and the amount of emphysema on CT scans predicts hospitalization from and deaths due to chronic lung disease.
“As temperatures rise with climate change, ground-level ozone will continue to increase unless steps are taken to reduce this pollutant. But it’s not clear what level of the air pollutants, if any, is safe for human health,” says Dr. R. Graham Barr, professor of medicine and epidemiology at Columbia University, who led the MESA Lung study and is a senior author of the paper.