Air pollution may cause irregular heart rhythms in otherwise healthy teens within two hours of exposure, a new study shows.
Irregular heart rhythms, or arrhythmias, occur when the heart's electrical impulses don't work properly. Symptoms may include heart flutters, chest pain, fainting or dizziness. Some arrhythmias increase a teen's chances of sudden cardiac death or developing heart disease later on, researchers said.
"The main take-home message for the teenagers is that air pollution may trigger severe cardiac outcomes, even contribute to death, [even if] they are normally very healthy," said study author Fan He, an instructor in public health sciences at Penn State College of Medicine.
"Wearing face masks may be warranted on highly polluted days, and avoiding vigorous physical activities, especially during rush hours, could reduce adverse health impacts of air pollution," He added. Pollution levels are known to be high during rush hour.
Particulate matter in the air consists of various chemicals, and some of them can be highly toxic. "Since these particles are extremely small, they can penetrate the bloodstream when inhaled and cause physiological damage," He said. This may include inflammation, damage to blood vessels, and/or blood clots.
"Once inhaled, the pollutants irritate the lungs and blood vessels around the heart, and previous research has suggested that over time, pollutants increase the process of disease in the arteries," He said.
PM2.5 particles, in particular, are less than 2.5 microns in size and can disrupt the autonomic nervous system, which controls the rhythm of heartbeats, He said.
For the study, the researchers tracked heart rhythms of 322 teens (average age 17) after they were exposed to pollution for 24 hours. None had any evidence or risk for heart disease when the study began. The researchers looked for two types of irregular heart rhythms: premature atrial contractions and premature ventricular contractions.
With premature atrial contractions, the heartbeat originates from the top chambers of the heart (atria). If frequent, these contractions may up the risk of atrial fibrillation, a heart rhythm disorder that dramatically increases risk for stroke.
With premature ventricular contractions, the heartbeat originates from one of the lower chambers of the heart (ventricles). These can raise the risk of later heart attack, stroke, heart failure or sudden cardiac death if they occur often.
Nearly 80% of the teens had at least one irregular heart rhythm during the 24-hour study period. Of these, 40% had premature atrial contractions, 12% had only premature ventricular contractions, and 48% had both, the study showed.
The average PM2.5 concentration was approximately 17 micrograms of particulate matter per cubic meter of air (µg/m3) a day. This falls well below what the U.S. Environmental Protection Agency considers risky.
For each increase of 10 µg/m3 in PM2.5, teens showed a 5% increase in the number of premature ventricular contractions within two hours of exposure. The study found no link between particulate matter concentration and the number of premature atrial contractions.
Similar findings have been seen among adults, He said. Researchers are now looking at how air pollution affects other markers of the heart's electrical activity.
The findings appear in the Sept. 14 issue of the Journal of the American Heart Association.
There are many ways that exposure to air pollution can increase the risk of irregular heart rhythms in teens and adults, said Aruni Bhatnagar, a professor of medicine at the University of Louisville in Kentucky.
"Inhalation of air particles, particularly fine particles, can induce lung inflammation and activate the sympathetic nervous system [or the irritant response]. Both these mechanisms can increase arrhythmias, but the relative contribution of each remains unknown," said Bhatnagar, who has written several American Heart Association statements and policy papers on air pollution.
Premature ventricular contractions are common, but when they occur frequently, they can lead to atrial fibrillation and an increased risk of heart attacks and stroke. Rarely, they can also lead to sudden cardiac death, said Bhatnagar, who was not involved in the new study.
To protect their hearts, teens and others should try to spend less time outdoors on high pollution days. "Because sports and vigorous physical activity also stimulate the sympathetic nervous system, it is best to avoid vigorous outdoor sports as well as running outside," Bhatnagar said.
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SOURCES: Fan He, PhD, instructor, public health sciences, Penn State College of Medicine, Hershey, Penn.; Aruni Bhatnagar, PhD, professor, medicine, University of Louisville, Ky.; Journal of the American Heart Association, Sept. 14, 2022