From the Journals

Exposure to outdoor air pollutants linked to increased emphysema



Long-term exposure to ambient air pollutants was significantly associated with increases in emphysema and decreases in lung function, according to a diverse cohort study of six U.S. metropolitan areas.

“These associations in a community-based population demonstrate novel evidence that air pollution contributes to worsening lung health,” wrote Meng Wang, PhD, of the University of Washington, Seattle, and coauthors. The study was published in JAMA.

To determine whether exposure to outdoor air pollutants was associated with emphysema progression and change in lung function, the Multiethnic Study of Atherosclerosis (MESA) assessed 6,860 participants from six areas: Winston-Salem, N.C.; New York City; Baltimore; St. Paul, Minn.; Chicago; and Los Angeles. Percent emphysema was calculated based on all available CT scans; lung function was assessed via spirometry.

Spatiotemporal exposure models were developed for ozone, fine particulate matter less than 2.5 mcm in aerodynamic diameter, and oxides of nitrogen in each area based on Environmental Protection Agency measurements and the study’s cohort-specific monitoring. Annual mean concentrations of fine particulate matter and nitrogen decreased during follow-up, while ozone concentrations did not.

All participants underwent a cardiac CT scan at baseline, and 5,780 had at least one follow-up CT scan over a median period of 10 years. At baseline, median percent emphysema was 3% and it increased 0.58 percentage points (95% confidence interval, 0.38-0.78) over 10 years. Ambient concentrations of ozone, fine particulate matter, nitrogen, and black carbon at baseline were significantly associated with greater increases in percent emphysema per 10 years, as were concentrations of zone and nitrogen during follow-up, reported Dr. Wang, formerly with the State University of New York at Buffalo.

Of the 3,636 participants who had at least one spirometric assessment, there was a mean decline in forced expiratory volume in 1 second (FEV1) of 309 mL (95% CI, 299-319 mL) and in forced vital capacity of 331 mL (95% CI, 317-345 mL) over 10 years. Ambient concentrations of ozone were significantly associated with a decline in FEV1, both at baseline and during follow-up.

The coauthors acknowledged their study’s limitations, including that general outdoor air pollution concentrations might not reflect individual exposure or concentrations indoors, where people spend most of their time. In addition, percent emphysema was only measured in the lower two-thirds of the lung, though they noted that “percent emphysema measured in the lower two-thirds of the lung correlates well with full-lung percent emphysema in this cohort and a cohort of smokers.”

This article was developed by the EPA and the University of Washington Center for Clean Air Research. MESA was funded by the National Institutes of Health and the National Heart, Lung, and Blood Institute, and supported by the National Institute of Environmental Health Sciences. The authors reported numerous conflicts of interest, including receiving grants and fees from the University of Washington, the EPA, the NIH, and various other pharmaceutical companies, foundations, and governmental entities.

SOURCE: Wang M et al. JAMA. 2019 Aug 13. doi: 10.1001/jama.2019.10255

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