Air pollution strikes at the heart, linked to rhythm disturbances
We expect air pollution to negatively affect the lungs, and studies have proven that to be the case. However, new research has shown that air pollution also affects the heart and can lead to rhythm disturbances called arrhythmias. Chinese researchers used data from 2,025 hospitals in 322 cities nationwide to evaluate hourly exposure to air pollution and examined its effects on heart rhythm.
Arrhythmia is caused by faulty electrical conduction, so the heart’s beats are not coordinated, and the heart can’t pump blood effectively. The current study looked at the prevalence of four common arrhythmias: atrial fibrillation (AF), where the upper chambers of the heart (atria) beat quickly and irregularly; atrial flutter, where the atria pump too quickly; premature beats arising in the atria and the ventricles (bottom chambers); and, supraventricular tachycardia (SVT), a faster-than-normal heart rate originating above the ventricles.
The large study included 190,115 patients with acute onset of symptomatic heart arrhythmias. Fatigue, weakness, lightheadedness, fainting, shortness of breath and chest pain are common arrhythmia symptoms.
Using data from air pollution monitoring stations near the hospitals, they looked at six pollutants: fine particles, coarse particles, nitrogen dioxide, sulfur dioxide, carbon monoxide and ozone. Fine particles or particulate matter (PM2.5) are tiny inhalable particles 2.5 microns or smaller, including dust, soot and smoke. Coarse particles (PM10) are 2.5 to 10 microns wide, such as pollen, spores, and plant and insect parts. Ozone is one of the major components of smog.
Analyzing the data, the researchers found a link between exposure to air pollution and the incidence of arrhythmia.
“We found that acute exposure to ambient air pollution was associated with increased risk of symptomatic arrhythmia,” said Renjie Chen, one of the study’s co-authors. “The risks occurred during the first several hours after exposure and could persist for 24 hours.”
They found that exposure to ambient air pollution was most strongly associated with atrial flutter and SVT, followed by AF and premature heartbeats. Nitrogen dioxide had the strongest association with all four arrhythmias, with longer exposure strengthening the association. The biggest contributors to nitrogen dioxide emissions are motor vehicles.
Further research will be conducted to ascertain what underlies this association.
“Although the exact mechanisms are not yet fully understood, the association between air pollution and acute onset of arrhythmias that we observed is biologically plausible,” said the researchers.
China’s high air pollution is well-known, caused by population increases and a heavy reliance on fossil fuels. In 2022, China’s average PM2.5 concentration was more than six times the World Health Organization’s (WHO) guideline value. But China is not alone.
According to the US Environmental Protection Agency (EPA), in 2021, about 67 million tons (60.8 million tonnes) of pollution were emitted into the US atmosphere, contributing mostly to ozone and particle concentrations. And despite progress in improving air quality, in the same year, more than 100 million people across the US lived in counties with pollution levels above the recommended National Ambient Air Quality Standards (NAAQS).
Although their study was conducted in a country known for its high levels of air pollution, the researchers say that the findings are applicable worldwide.
“Our study adds to the evidence of adverse cardiovascular effects of air pollution, highlighting the importance of further reducing exposure to air pollution and of prompt protection of susceptible populations worldwide,” they said.
The study was published in the Canadian Medical Association Journal.