Long-term Fine Particle Pollution Exposure Declines Lung Function, Progresses COPD

Xiang Qian Lao, PhD

Exposure to fine particle pollution matter over long periods of time increases the risk of reduced lung function and could result in the development of chronic obstructive pulmonary disease (COPD), according to a new study.

The findings reinforce expressed urgency to mitigate air pollution through global strategies, at least for the sake of improving people’s pulmonary health, study author Xiang Qian Lao, PhD, Assistant Professor at The Chinese University of Hong Kong, told MD Magazine.

Many studies have already shown that short-term exposure to fine particle pollution can have a negative effect on lung function, but any impairment that occurs might be reversible. Just 2 studies on the long-term effect on adults have focused on fine particle pollution, with inconsistent results. Past research was also focused on white populations with comparatively low concentrations of air pollution.

Lao said their goal was to get clearer results by studying the long-term effects of fine particle pollution exposure and COPD development in a longitudinal cohort in Taiwan.

Between 2001 and 2014, researchers recruited 285,046 participants from the Taiwan MJ Health Management Institution cohort. All were of Chinese descent, residents of Taiwan, and aged 20 years or older. During each medical visit, subjects were given a physical exam, including spirometry tests (strictly following the protocol of the American Thorax Society), blood and urine tests, and a self-administered questionnaire.

The final analysis included 91,709 subjects who had more than 1 medical visit, did not have a previous diagnosis of COPD, and had a follow-up duration 2 years or more (those with a follow-up duration of less than 2 years were excluded because COPD was unlikely caused by fine particle pollution exposure).

Results showed that for every 5 mcg increase in fine particulate matter (PM2.5), lung function declined in 4 areas: 1.18% in forced vital capacity (FVC), 1.46% in forced expiratory volume in 1 second (FEV1), 1.65% in maximum mid-expiratory flow 9MMEF) and 0.21% in Fev1: FVC ratio. The decline also accelerated over time: 0.14% for FVC, 0.24% for FEV1, 0.44% for MMEF, and 0.09% for FEV1: FVC.

Compared to subjects exposed to PM2.5 in the first quartile, those exposed in the second, third and fourth quartiles had a hazard ratio for developing COPD of 1.39 (95% CI 1.24 to 1.56), 1.30 (1.16 to 1.46), and 1.23 (1.09 to 1.39).

“To the best of our knowledge, this is the largest longitudinal cohort to date,” researchers wrote. “The large sample size and long follow-up period provided strong power to detect the clinically significant adverse effects on pulmonary health.”

Lao said he and his team were not able to investigate the effects of other gaseous pollutants, such as NOx and ozone. In addition, links between air pollution and other organs/systems are unclear and need further investigation.

“The best way individuals can address this issue is to increase public awareness, inspire people and urge governments to take actions to reduce air pollution,” Lao said.

The study, "Effect of long-term exposure to fine particulate matter on lung function decline and risk of chronic obstructive pulmonary disease in Taiwan: a longitudinal, cohort study," was published online in The Lancet Planetary Health.