Even at concentrations below the World Health Organization’s air quality guidelines, transient exposure to fine particulate matter (PM_2.5), nitrogen dioxide, sulfur dioxide or carbon monoxide, but not coarse particulate matter or ozone, may trigger the onset of an acute coronary syndrome (ACS), according to a study published June 14 in Circulation.

Renjie Chen, PhD, et al., used a nationwide registry in China to conduct a time-stratified case-crossover study to investigate the association between the hourly exposure to specified air pollutants and the onset of ACS and its subtypes. Real-time data on criteria air pollutants were obtained from the national Urban Air Quality Real-Time Publishing Platform. The levels of air pollution exposure before the hour of the ACS symptomatic onset were compared with a control period for each individual patient, a design that allowed each patient to be their own control and minimize potential confounding.

A total of 1,292,880 patients with an ACS (STEMI, NSTEMI, unstable angina) from 2,239 hospitals in 318 Chinese cities between January 1, 2015, and September 30, 2020, were included in the study. Their data were obtained from the Chest Pain Center (CCA) Database – Chest Pain Center, a nationally representative, multicenter registry.

Results showed that acute exposure to fine particulate matter, nitrogen dioxide, sulfur dioxide and carbon monoxide was associated with ACS onset and its subtypes and that the association was strongest at the concurrent hour. An interquartile range increase in concentrations of fine particulate matter (36.0 μg/m3), nitrogen dioxide (29.0 µg/m3), sulfur dioxide (9.0 µg/m3) and carbon monoxide (0.6 mg/m3) over the preceding 24 hours was significantly associated with a 1.32%, 3.89%, 0.67% and 1.55% higher risk of ACS onset, respectively. No apparent threshold was observed. The associations were greater in patients who were older than 65 years and during the cold season.

In what the investigators say is the first case-crossover study to systematically investigate the roles of specific pollutants on an hourly basis, they write it demonstrated immediate and robust associations with transient exposures to air pollution and an increased risk of ACS. Furthermore, they write, “The findings of this study add to the mounting evidence on the adverse cardiovascular effects of air pollution and its time course, underscoring continued efforts for public health intervention and air pollution control.”

In an accompanying editorial comment, Nicholas L. Mills, MD, PhD, and C. Arden Pope, PhD, write “Whilst it is not possible to identify those who are truly susceptible in clinical practice, interventions to reduce risk of exposure to air pollution should focus on policies to reduce emissions and population exposure.” They add that physicians should keep in mind there is evidence that long-term exposure to air pollution contributes to the initiation and progression of coronary artery disease and that short-term exposure for those with existing diseases have an increased risk of triggering an acute event.

Clinical Topics: Acute Coronary Syndromes, Cardiovascular Care Team, Stable Ischemic Heart Disease, Vascular Medicine, Atherosclerotic Disease (CAD/PAD), Chronic Angina

Keywords: Environmental Pollutants, Physicians, Angina, Unstable, World Health Organization, Air Pollutants, Particulate Matter, Air Pollution, Public Health, Pain Clinics, Non-ST Elevated Myocardial Infarction, Coronary Artery Disease, ST Elevation Myocardial Infarction, Acute Coronary Syndrome, Cross-Over Studies, Carbon Monoxide, Sulfur Dioxide, Nitrogen Dioxide

< Back to Listings