Air Pollution and Percent Emphysema Identified by Computed Tomography in the Multi-Ethnic Study of Atherosclerosis

Oct 11, 2014Environmental health perspectives

Air pollution linked to lung damage measured by CT scans in a diverse population study

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Abstract

Among 6,515 participants, higher concentrations of PM2.5 (5 μg/m3) and NOx (25 ppb) were associated with a 0.6% and 0.5% increase in average percent emphysema, respectively.

Long-term exposure to particulate matter and nitrogen oxides may correlate with increased emphysema-like lung characteristics as measured by CT scans.
Percent emphysema was defined using a specific threshold on cardiac CT scans, identifying lung regions with low density.
After adjusting for study site, the associations between PM2.5 and NOx with percent emphysema were not statistically significant.
Reduced lung function measures, such as FEV1 and FVC, were linked to higher levels of PM2.5 and NOx in a subset of participants.
Most associations between air pollution and lung function were not statistically significant, indicating potential variability in results.

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BACKGROUND: Air pollution is linked to low lung function and to respiratory events, yet little is known of associations with lung structure.

OBJECTIVES: We examined associations of particulate matter (PM2.5, PM10) and nitrogen oxides (NOx) with percent emphysema-like lung on computed tomography (CT).

METHODS: The Multi-Ethnic Study of Atherosclerosis (MESA) recruited participants (45-84 years of age) in six U.S. states. Percent emphysema was defined as lung regions < -910 Hounsfield Units on cardiac CT scans acquired following a highly standardized protocol. Spirometry was also conducted on a subset. Individual-level 1- and 20-year average air pollution exposures were estimated using spatiotemporal models that included cohort-specific measurements. Multivariable regression was conducted to adjust for traditional risk factors and study location.

RESULTS: Among 6,515 participants, we found evidence of an association between percent emphysema and long-term pollution concentrations in an analysis leveraging between-city exposure contrasts. Higher concentrations of PM2.5 (5 μg/m3) and NOx (25 ppb) over the previous year were associated with 0.6 (95% CI: 0.1, 1.2%) and 0.5 (95% CI: 0.1, 0.9%) higher average percent emphysema, respectively. However, after adjustment for study site the associations were -0.6% (95% CI: -1.5, 0.3%) for PM2.5 and -0.5% (95% CI: -1.1, 0.02%) for NOx. Lower lung function measures (FEV1 and FVC) were associated with higher PM2.5 and NOx levels in 3,791 participants before and after adjustment for study site, though most associations were not statistically significant.

CONCLUSIONS: Associations between ambient air pollution and percentage of emphysema-like lung were inconclusive in this cross-sectional study, thus longitudinal analyses may better clarify these associations with percent emphysema.

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Air Pollution and Percent Emphysema Identified by Computed Tomography in the Multi-Ethnic Study of Atherosclerosis

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