A study conducted in China revealed that exposure to fine particulate air pollution is more strongly linked to deaths among people with cardiovascular and respiratory diseases, including chronic obstructive pulmonary disease (COPD), than in the overall population.
The study, “Fine Particulate Air Pollution and Daily Mortality: A Nationwide Analysis in 272 Chinese Cities,” published in the American Journal of Respiratory and Critical Care Medicine, focused on data from 272 cities collected from 2013 to 2015.
According to the authors, this is the largest epidemiological study conducted in the developing world assessing air pollution and mortality.
“Fine particulate [PM2.5] air pollution is one of the key public health concerns in developing countries including China, but the epidemiological evidence about its health effects is scarce,” Maigeng Zhou, PhD, the study’s senior author, said in a news release.
“A new monitoring network allowed us to conduct a nationwide study to evaluate short-term associations between PM2.5 and daily cause-specific mortality in China,” said Zhou, the deputy director of the National Center for Chronic and Non-communicable Disease Control and Prevention at the Chinese Center for Disease Control and Prevention.
The study revealed that the average annual mean concentration of fine particulate (PM2.5) in 272 Chinese cities was 56 micrograms per cubic meter (μg/m3), well over the World Health Organization (WHO) air quality maximum concentration guidelines of 10 μg/m3.
Researchers also found that an increase of 10 μg/m3 in air pollution was linked to a 0.22% increase in mortality due to non-accident related causes, a 0.29% increase in all respiratory mortality, and a 0.38% increase in mortality among patients with COPD.
In addition, a significant increase in mortality was found in people with lower levels of education, in the elderly (ages 75 and older), and also in warmer cities.
The team suggests that educational differences may indirectly have an impact on healthcare access, possibly justifying the higher mortality seen among people with lower education levels.
Concerning warmer climates, researchers surmise that residents spend more time outside or with open windows, which can increase their exposure to fine particulate pollution.
Compared to U.S. and European studies, however, the link between an increase in PM2.5 and mortality in China appears to be weaker. The team believes that a possible explanation might be that there is a plateau (a state of little or no change) of mortality rates at the highest levels of pollution; moreover, PM2.5 components in China may be less toxic than the components in the U.S. and Europe.
“Our findings may be helpful to formulate public health policies and ambient air quality standards in developing countries to reduce the disease burden associated with PM2.5 air pollution,” said study co-author Haidong Kan, MD, professor of public health at Fudan University in China. “Further massive investigations, especially looking at the long-term effect studies, are needed to confirm our results and to identify the most toxic components of PM2.5 in China.”