Long-Term Air Pollution Linked to Emphysema and Lung Function

by | Mar 2, 2020 | 2019, Environmental Health, Lung Health, Pollution

Written by Joyce Smith, BS. Exposure to long-term ambient air pollution, especially ozone (O3) was significantly associated with increases in emphysema and worsening lung function in a well-characterized, multiethnic cohort of adults.

Environmental HealthAmbient air pollution is a major risk factor for poor health 1. Ground level O3 is an oxidizing agent and common air pollutant worldwide. Toxicological studies have shown that O3 causes persistent pulmonary inflammation and structural alterations throughout the lung that may play a role in chronic lower respiratory disease, including emphysema 2. In animals, fine particulate matter (PM2.5) exposure leads to neutrophilic pulmonary inflammation and oxidative stress 3, and in healthy adults, controlled exposure to PM2.5 leads to increased systemic inflammation and endothelial microparticles, including those of lung origin 4.

A study 5 by Wang and colleagues, was conducted between 2000 and 2018, to assess whether exposure to existing air pollutant concentrations is associated with progression of emphysema. The study cohort consisted of 7,071 participants from the Multi-Ethnic study of Atherosclerosis (MESA) Air and Lung Studies. Adult participants, aged 45-84 years, and from six metropolitan regions in the United States were tested for baseline air pollution concentrations and followed up for a period of 18 years. Each participant had up to five computer tomographic images (CT scans) and 2,772 had one to three follow-up spirometric measurements to determine lung function over a median of 10 years.

Of the 7,071 participants at baseline, 3,126 (46%) were lifelong nonsmokers, 2,595 (38%) were white, 4,344 (63%) had some college education and 3,330 were men. CT scans revealed a statistically significant association between greater increases in emphysema and higher residential baseline concentrations of ambient O3, PM2.5, and oxides of nitrogen (NOx) and black carbon. When comparing all of the pollutants, the association for O3 was the most robust and of the greatest magnitude. However, over the 18-year study follow-up, the research team found that higher residential concentrations of O3 and NOx were also significantly associated with increases in emphysema progression, but not concentrations of PM2.5.

Development of emphysema can be a slow, lifelong process. Median emphysema was 3% at baseline and increased a mean of 0.58 percentage points per 10 years. In fact, in this cohort each 10 years of smoking a pack a day was significantly associated with an increased progression of 0.06 percentage points [95% CI, 0.02-0.11] of emphysema (the equivalent of 3 years of aging). Among the subset of participants who, at baseline, demonstrated limited air flow, baseline ambient O3 was significantly associated with a faster progression of emphysema and a decline in forced expiratory volume in the first second (FEV1). Also, among current smokers, researchers found a greater association between O3 and loss of lung function, perhaps because smoking increases airway inflammation and oxidative stress 6.

The annual averages of O3 levels in the six study areas were between 10 and 25 ppb. Unless new control strategies are implemented, these levels are not expected to decline as climate change advances 7. This contrasts with the observed trends in which PM2.5 and NOx levels were controlled and even declined because of past government regulatory initiatives that were implemented to control these two pollutants.

Study limitations include the inability to assess air pollution in residential homes and the workplace 8 since most individuals spend their time indoors 9. Also, emphysema was measured in only the lower two-thirds of the lung. Also, advancements in CT technologies occurred during the course of the study which may have impacted the data, and lastly, no volume correction on CT data was performed.

In this study, long-term concentrations of O3 at current levels were strongly and consistently associated with both progression of emphysema and decline in lung function, prompting researchers to recommend more effective control strategies to reduce O3 concentrations that may be necessary to protect future lung health.

Source:  Wang, Meng, Carrie Pistenmaa Aaron, Jaime Madrigano, Eric A. Hoffman, Elsa Angelini, Jie Yang, Andrew Laine et al. “Association between long-term exposure to ambient air pollution and change in quantitatively assessed emphysema and lung function.” Jama 322, no. 6 (2019): 546-556.

2019 American Medical Association. All rights reserved.

Posted March 2, 2020.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

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