Long-term exposure to ambient air pollutants, especially O₃ (ozone), is significantly associated with increasing emphysema, according to a new study led by the University of Washington, Columbia University and the University at Buffalo.

While previous studies have shown a clear connection of air pollutants with some heart and lung diseases, the new research published in the Journal of the American Medical Association (JAMA) demonstrates an association between long-term exposure to all major air pollutants with an increase in emphysema seen on lung scans. Emphysema is a condition in which destruction of lung tissue leads to wheezing, coughing and shortness of breath, and increases the risk of death.

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.

—Dr. Joel Kaufman, senior co-author

The researchers found that if the ambient ozone level was 3 parts per billion higher where you live compared to another location over 10 years, that was associated with an increase in emphysema roughly the equivalent of 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.

Rates of chronic lung disease in this country are going up and increasingly it is recognized that this disease occurs in nonsmokers. 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.

—Dr. Kaufman

The cohort study included participants from the Multi-Ethnic Study of Atherosclerosis (MESA) Air and Lung Studies conducted in 6 metropolitan regions of the United States, which included 6,814 adults aged 45 to 84 years recruited between July 2000 and August 2002, and an additional 257 participants recruited from February 2005 to May 2007, with follow-up through November 2018.

To our knowledge, this is the first longitudinal study to assess the association between long-term exposure to air pollutants and progression of percent emphysema in a large, community-based, multi-ethnic cohort.

—first author Meng Wang

The authors developed novel and accurate exposure assessment methods for air pollution levels at the homes of study participants, collecting detailed measurement of exposures over years in these metropolitan regions, and measurements at the homes of many of the participants. This work in the MESA Air study was led at the University of Washington. While most of the airborne pollutants are in decline because of successful efforts to reduce them, ozone has been increasing, the study found. Ground-level ozone is mostly produced when ultraviolet light reacts with pollutants from fossil fuels.

This is a big study with state-of-the-art analysis of more than 15,000 CT scans repeated on thousands of people over as long as 18 years. 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.

—Dr. R. Graham Barr, a senior author

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.

The MESA Air study was funded by the US Environmental Protection Agency. MESA and MESA Lung Study were funded by the National Heart, Lung, and Blood Institute. The work was also supported by the National Institute of Environmental Health Sciences.

Resources

• Wang M, Aaron CP, Madrigano J, et al. (2019) “Association Between Long-term Exposure to Ambient Air Pollution and Change in Quantitatively Assessed Emphysema and Lung Function.” JAMA 322(6):546–556 doi: 10.1001/jama.2019.10255