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Original Investigation
August 13, 2019

Association Between Long-term Exposure to Ambient Air Pollution and Change in Quantitatively Assessed Emphysema and Lung Function

Author Affiliations
  • 1Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle
  • 2Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York
  • 3Research and Education in Energy, Environment and Water Institute, University at Buffalo, Buffalo, New York
  • 4Department of Medicine, Columbia University Medical Center, New York, New York
  • 5Department of Environmental Health Sciences, Epidemiology, Mailman School of Public Health; Columbia University, New York, New York
  • 6RAND Corporation, Arlington, Virginia
  • 7Department of Radiology, University of Iowa, Iowa City
  • 8Department of Biomedical Engineering, Columbia University, New York, New York
  • 9Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts
  • 10Department of Statistics, University of Washington, Seattle
  • 11Department of Biostatistics, School of Public Health, University of Washington, Seattle
  • 12Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor
  • 13Department of Medicine, McGill University Health Centre, Montréal, Canada
  • 14Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York
  • 15Department of Epidemiology, School of Public Health, Drexel University, Philadelphia, Pennsylvania
  • 16Departments of Medicine and Epidemiology, University of Washington, Seattle
JAMA. 2019;322(6):546-556. doi:10.1001/jama.2019.10255
Key Points

Question  Is there an association between ambient air pollutants and progression of emphysema and changes in lung function in the general population?

Findings  In this cohort study conducted between 2000 and 2018 that included 5780 participants in 6 US metropolitan regions followed up for a median of 10 years, there was a statistically significant association between baseline ambient concentrations of ambient ozone (O3), fine particulate matter (PM2.5), oxides of nitrogen (NOx), and black carbon with greater increases in emphysema assessed quantitatively using computed tomographic (CT) imaging. Concentrations of O3 and NOx, but not concentrations of PM2.5, over study follow-up were also associated with increases in emphysema. Baseline ambient O3 was significantly associated with a faster decline in forced expiratory volume in the first second (FEV1).

Meaning  Long-term exposure to ambient air pollutants, especially O3, was significantly associated with increasing emphysema assessed quantitatively using CT imaging and with worsening lung function.

Abstract

Importance  While air pollutants at historical levels have been associated with cardiovascular and respiratory diseases, it is not known whether exposure to contemporary air pollutant concentrations is associated with progression of emphysema.

Objective  To assess the longitudinal association of ambient ozone (O3), fine particulate matter (PM2.5), oxides of nitrogen (NOx), and black carbon exposure with change in percent emphysema assessed via computed tomographic (CT) imaging and lung function.

Design, Setting, and Participants  This 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 6814 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.

Exposures  Residence-specific air pollutant concentrations (O3, PM2.5, NOx, and black carbon) were estimated by validated spatiotemporal models incorporating cohort-specific monitoring, determined from 1999 through the end of follow-up.

Main Outcomes and Measures  Percent emphysema, defined as the percent of lung pixels less than −950 Hounsfield units, was assessed up to 5 times per participant via cardiac CT scan (2000-2007) and equivalent regions on lung CT scans (2010-2018). Spirometry was performed up to 3 times per participant (2004-2018).

Results  Among 7071 study participants (mean [range] age at recruitment, 60 [45-84] years; 3330 [47.1%] were men), 5780 were assigned outdoor residential air pollution concentrations in the year of their baseline examination and during the follow-up period and had at least 1 follow-up CT scan, and 2772 had at least 1 follow-up spirometric assessment, over a median of 10 years. Median percent emphysema was 3% at baseline and increased a mean of 0.58 percentage points per 10 years. Mean ambient concentrations of PM2.5 and NOx, but not O3, decreased substantially during follow-up. Ambient concentrations of O3, PM2.5, NOx, and black carbon at study baseline were significantly associated with greater increases in percent emphysema per 10 years (O3: 0.13 per 3 parts per billion [95% CI, 0.03-0.24]; PM2.5: 0.11 per 2 μg/m3 [95% CI, 0.03-0.19]; NOx: 0.06 per 10 parts per billion [95% CI, 0.01-0.12]; black carbon: 0.10 per 0.2 μg/m3 [95% CI, 0.01-0.18]). Ambient O3 and NOx concentrations, but not PM2.5 concentrations, during follow-up were also significantly associated with greater increases in percent emphysema. Ambient O3 concentrations, but not other pollutants, at baseline and during follow-up were significantly associated with a greater decline in forced expiratory volume in 1 second per 10 years (baseline: 13.41 mL per 3 parts per billion [95% CI, 0.7-26.1]; follow-up: 18.15 mL per 3 parts per billion [95% CI, 1.59-34.71]).

Conclusions and Relevance  In this cohort study conducted between 2000 and 2018 in 6 US metropolitan regions, long-term exposure to ambient air pollutants was significantly associated with increasing emphysema assessed quantitatively using CT imaging and lung function.

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