• Frequent Heavy Pollution Events in Developing Countries Cause Substantial CV Risk – Wide-Scale Chinese Observational Study

    Heavy pollution events with fine particulate matter – frequent in developing countries – cause substantial increases in cardiovascular disease hospital admissions, according to a new large observational study from the Chinese Center for Disease Control and Prevention.

    The worse the pollution event, the greater the associated risk, researchers led by Yi Zhang, MPH, noted.

    The findings were published Monday online ahead of the Sept. 7 issue of the Journal of the American College of Cardiology.

    Fine particle matter with an aerodynamic diameter of 2.5 μm or less – known as PM2.5 pollution events – “continue to occur frequently in developing countries” in South Asia, western sub-Saharan Africa, North Africa, the Middle East and East Asia, the researchers noted, citing the U.S. Health Effects Institute’s (HEI) State of Global Air/2019 report.

    Previous data have demonstrated links between heavy pollution events and cardiovascular risk, the researchers said; however, they stressed that the focus has been extremely heavy PM2.5, which cannot be generalized to other heavy PM2.5 pollution events.

    “However, because of the lack of research on the health risks of frequently occurring heavy PM2.5 pollution events, this critical public health burden has failed to attract sufficient attention from the government, marked by a pronounced lack of health protection measures to combat heavy PM2.5 pollution events,” the researchers lamented.

    They, therefore, set out to establish quantitative evidence through a case-crossover study in Beijing, which experienced heavy PM2.5 pollution events from 2013 to 2017.

    A total of 2,202,244 hospital admissions for cardiovascular diseases were observed by the Beijing Municipal Commission of Health and Family Planning Information Center from January 1, 2013, to December 31, 2017 – a citywide hospital admission surveillance system in the Chinese capital. This covered all hospitals except for “first-level” hospitals in charge of community and primary care.

    Patients who had lived in Beijing for less than 6 months were also excluded.

    Of the more than 2 million cardiovascular disease hospital admissions, the patients’ mean age was 64 (± 16) years, they were majority male (58.4%) and largely Han nationality (94.62%).

    Meanwhile, air pollution data from 35 monitoring stations across all 16 districts in Beijing were collected from the Beijing Municipal Environmental Monitoring Center, across 222 days of extremely heavy PM2.5 pollution events (defined as PM2.5 concentration ≥150 μm/m3).

    The daily average PM2.5, O3, NO2, SO2 and CO levels were calculated from the hourly data of the surveillance stations, while daily temperature and relative humidity were collected from the Chinese Meteorological Data Network of the Chinese Meteorological Bureau.

    Pollution events were stratified as heavy or extremely heavy based on PM2.5 concentration levels and length of event.

    A time-stratified case-crossover design was utilized to explore the association between different lasting days of PM2.5 heavy pollution events and cardiovascular disease admission.

    The average increased hospital admission numbers for cardiovascular disease annually were 1,322 (95% confidence interval [CI]: 839-1,806) and 3,311 (95% CI: 2,969-3,655) during heavy and extremely heavy PM2.5 pollution events, lasting for 1 day or more in Beijing with a PM2.5 concentration of 75-149 mg/m3 and ≥150 mg/m3, respectively.

    Increased admission days related to heavy and extremely heavy pollution events lasting for 1 day or more were 14,781 days (95% CI: 9,381- 20,193 days) and 37,020 days (95% CI: 33,196-40,866 days), respectively.

    The odds ratio (OR) associated with extremely heavy PM2.5 pollution events lasting for 3 days or more for total cardiovascular disease was 1.085 (95% CI: 1.077-1.093).

    Respectively, ORs for individual cardiovascular conditions were: angina 1.112 (95% CI: 1.095-1.130), myocardial infarction 1.068 (95% CI: 1.037-1.100), ischemic stroke 1.071 (95% CI: 1.053-1.090) and heart failure 1.060 (95% CI: 1.021-1.101).

    “Most of the specific causes of hospital admissions for cardiovascular disease significantly were associated with heavy PM2.5 pollution events or extremely heavy PM2.5 pollution events, except hemorrhagic stroke,” the researchers noted.

    “Heavy and extremely heavy PM2.5 pollution events resulted in substantially increased hospital admission risk for cardiovascular disease. With higher PM2.5 concentration and longer duration of heavy PM2.5 pollution events, a greater risk of cardiovascular hospital admission was observed,” they concluded.

    The researchers pushed for further studies exploring the association between components or sources of PM2.5 and cardiovascular disease.

    They warned that without quantitative evidence, the “necessary legislation and early warning systems have not been established” and that “without a robust response, this situation will eventually result in serious harm to public health.

    “Thus, it is urgent to fully address the health risks of regularly occurring heavy PM2.5 pollution events.”

    In an accompanying editorial, Sanjay Rajagopalan, MD, from University Hospitals and Case Western Reserve University, Cleveland, and colleagues said the findings are in general “entirely consistent with the known effects of air pollution, with both dose and duration of heavy antecedent exposure increasing the risk for hospitalization.”

    The editorialists added that China has committed to peaking its carbon emissions by 2030 and be carbon neutral by 2060 as part of the Paris climate accord.

    “Forgoing an opportunity to regulate air pollution levels would only mean that China may be farther away from achieving a healthy environment for its citizenry,” they said.


    Zhang Y, Ma R, Ban J et al. Risk of Cardiovascular Hospital Admission After Exposure to Fine Particulate Pollution. J Am Coll Cardiol 2021;78:1015-1024.

    Rajagopalan S, Brook RD, Al-Kindi S. How Tweets Can Cause a Revolution. J Am Coll Cardiol 2021;78:1025-1027.

    Image Credit: Gang – stock.adobe.com

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