Don’t breathe! It may put you at risk for this chronic disease

By Melissa Sammy, MDLinx
Published July 25, 2019

Key Takeaways

In a recent study published in the European Respiratory Journal, researchers demonstrated the association of ambient air pollution with accelerated lung aging, reduced lung function, and increased risk of developing chronic obstructive pulmonary disease (COPD).

COPD is a progressive, long-term, life-threatening lung disease that causes breathlessness and has been associated with decreased lung function, which can lead to inflammation in the lungs and a narrowing of the airways, making breathing difficult. Of note, there is no cure for COPD, although some treatments such as bronchodilators and inhaled steroids may alleviate symptoms and improve quality of life.

COPD is the third leading cause of death worldwide, having claimed approximately 3 million lives in 2016, and the number of global deaths due to COPD are expected to rise over the next decade, according to the World Health Organization (WHO). In the United States alone, about 12 million adults receive COPD diagnoses each year, and another 12 million adults are thought to have undiagnosed COPD. Although age-adjusted death rates for COPD have decline among US men from 1999 to 2014, these rates have remained relatively steady among US women. In all, approximately 120,000 deaths are attributed to COPD annually in the United States.

The primary cause of COPD is exposure to tobacco smoke from either active or secondhand smoking. However, some experts have suggested that indoor and outdoor air pollution, as well as occupational dust and fumes, may all be disease risk factors, although the evidence regarding this association is lacking.

“There are surprisingly few studies that look at how air pollution affects lung health,” noted senior author Anna L. Hansell, MD, PhD, professor, Environmental Epidemiology, Centre for Environmental Health and Sustainability, University of Leicester, Leicester, United Kingdom.

To address this paucity in data, Dr. Hansell and fellow researchers sought to determine the impact of ambient air pollution on lung function and COPD risk, and assess possible vulnerability factors. The study sample consisted of 303,887 individuals aged 40-69 years from the UK Biobank study. Eligible participants had complete covariate data from health questionnaires and valid lung function measures obtained from spirometry tests between 2006 and 2010.

Pollution levels that participants may have been exposed to at their homes were estimated using a validated air pollution model. Evaluated pollutant types included particulate matter (PM10), fine particulate matter (PM2.5), and nitrogen dioxide (NO2)—all of which are byproducts of burned fossil fuels from vehicle exhausts, power plants, and industrial emissions.

Dr. Hansell and colleagues conducted multiple analyses, factoring in participants’ age, sex, body mass index, household income, education level, smoking status, and exposure to secondhand smoke. They also investigated the impact of working in occupations associated with increased COPD risk on disease prevalence. In all, they found that for each additional 5 µg/m3 of PM2.5 that a participant was exposed to on average annually at home, their lungs demonstrated an equivalent of 2 years of aging, as well as diminished function.

Furthermore, the researchers found that among participants residing in areas with PM2.5 levels above the WHO annual average guidelines of 10 µg/m3, the prevalence of COPD was four times greater compared with individuals exposed to secondhand smoking at home, and the prevalence was one-half of that among individuals who had ever been smokers.

Of note, the current air quality limit for PM2.5 is 25 µg/m3 in the European Union—higher than the concentrations associated with decreased lung function in this study.

“In one of the largest analyses to date, we found that outdoor air pollution exposure is directly linked to lower lung function and increased COPD prevalence. We found that people exposed to higher levels of pollutants had lower lung function equivalent to at least a year of ageing,” Dr. Hansell explained.

She continued: “Worryingly, we found that air pollution had much larger effects on people from lower income households. Air pollution had approximately twice the impact on lung function decline and three times the increased COPD risk on lower-income participants compared to higher-income participants who had the same air pollution exposure.”

“We accounted for participants’ smoking status and if their occupation might affect lung health, and think this disparity could be related to poorer housing conditions or diet, worse access to healthcare or long-term effects of poverty affecting lung growth in childhood. However, further research is needed to investigate the differences in effects between people from lower- and higher-income homes,” she noted.

The authors acknowledged that their study did have some limitations. Notably, they were unable to track participants’ exposure to pollutants in their daily lives. They also noted that study participants were largely healthier and wealthier than the general public, which could have confounded estimates regarding the strength of the association of air pollution exposure with diminished lung function.

“The findings of this large study reinforce that exposure to polluted air seriously harms human health by reducing life expectancy and making people more prone to developing chronic lung disease,” said European Respiratory Society president Professor Tobias Welte, who was not involved in the study.

 “Access to clean air is a fundamental need and right…Governments have a responsibility to protect this right by ensuring that maximum pollutant levels indicated by the [WHO] are not breached…Breathing is the most basic human function required to sustain life, which is why we must continue to fight for the right to breathe clean air,” he added.

Dr. Hansell and fellow researchers are currently conducting additional studies to determine whether genetic factors interact with air pollution and the potential impact it may have on health.

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