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

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 (O ₃), fine particulate matter (PM _2.5), oxides of nitrogen (NO _x), and black carbon with greater increases in emphysema assessed quantitatively using computed tomographic (CT) imaging. Concentrations of O ₃ and NO _x, but not concentrations of PM _2.5, over study follow-up were also associated with increases in emphysema. Baseline ambient O ₃ was significantly associated with a faster decline in forced expiratory volume in the first second (FEV ₁).

Meaning

Long-term exposure to ambient air pollutants, especially O ₃, 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 (O ₃), fine particulate matter (PM _2.5), oxides of nitrogen (NO _x), 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 (O ₃, PM _2.5, NO _x, 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 PM _2.5 and NO _x, but not O ₃, decreased substantially during follow-up. Ambient concentrations of O ₃, PM _2.5, NO _x, and black carbon at study baseline were significantly associated with greater increases in percent emphysema per 10 years (O ₃: 0.13 per 3 parts per billion [95% CI, 0.03-0.24]; PM _2.5: 0.11 per 2 μg/m ³ [95% CI, 0.03-0.19]; NO _x: 0.06 per 10 parts per billion [95% CI, 0.01-0.12]; black carbon: 0.10 per 0.2 μg/m ³ [95% CI, 0.01-0.18]). Ambient O ₃ and NO _x concentrations, but not PM _2.5 concentrations, during follow-up were also significantly associated with greater increases in percent emphysema. Ambient O ₃ 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.

Abstract

This cohort study examines the association between long-term exposure to ambient ozone, black carbon, and other air pollutants and progression of CT-defined percent emphysema and decline in lung function in adults in 6 US metropolitan regions.