Scientists from Fudan University found that exposure to air pollutants – even at levels below World Health Organization air quality guidelines – may trigger a heart attack within the hour.
The study found exposure to any level of four common air pollutants could quickly trigger the onset of the acute coronary syndrome.
The risks were highest among older people and when the weather was colder.
The research is published in Circulation and was conducted by Haidong Kan et al.
The acute coronary syndrome is an umbrella term describing any situation in which blood supplied to the heart muscle is blocked, such as in a heart attack or unstable angina, chest pain caused by blood clots that temporarily block an artery.
The strongest risk occurred within the first hour of exposure and diminished over the course of the day.
Exposure to fine particulate matter – microscopic solids or liquid droplets that come from automobile emissions, power plants, construction sites and other sources of pollution – has been unequivocally linked to heart disease, stroke and other health issues, as well as 4.2 million premature deaths worldwide.
These particles can be so small that when inhaled, they may go deep into the lungs or even the bloodstream.
In the study, the team analyzed medical data for nearly 1.3 million people treated for heart attacks and unstable angina at 2,239 hospitals in 318 Chinese cities between 2015 and 2020.
They compared hourly onset times of heart events with concentrations of fine particulate matter, coarse particulate matter, nitrogen dioxide, sulfur dioxide, carbon monoxide and ozone.
The team found short-term exposure to any level of fine particulate matter, nitrogen dioxide, sulfur dioxide and carbon monoxide was linked to the acute coronary syndrome.
As levels of the studied pollutants rose, so did the risk for heart attacks. Exposure to nitrogen dioxide was most strongly associated, followed by fine particulate matter, and was most dangerous during the first hour following exposure.
The link was strongest among adults age 65 and older with no history of smoking or other respiratory illnesses and for people exposed during the colder months.
The team says the heart effects of air pollution should be a serious concern for all, including policymakers, clinicians and individuals.
The study is the first to establish a link between pollution exposure and heart attacks on an hourly basis.
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