Another Reason for a Heart Attack

A research team including the Japanese Circulation Society has uncovered a link between air pollution and heart attacks.

In its study, the researchers determined that exposure to high concentrations of microscopic particulate matter (PM2.5) in the air increases the risk of acute myocardial infarction.

PM2.5 refers to extremely fine particles with a diameter of 2.5 micrometers or less that contain various substances. Because they can penetrate deep into the lungs, concerns exist about their health impacts.

The study also found a similar risk associated with black carbon (soot), a component of PM2.5, stating that it is useful for evaluating air-related acute myocardial infarction risks.

The researchers analyzed approximately 44,000 cases of patients diagnosed with acute myocardial infarction between April 2017 and December 2019.

The study focused on seven prefectures, including Tokyo, where the Environment Ministry has installed continuous automatic PM2.5 monitoring devices.

The results showed a 2.4-percent increase in a patient’s risk of a heart attack for every 7.9-microgram jump in the concentration of PM2.5 per cubic meter; this is specific to the day they were hospitalized and the day before.

Furthermore, the study found that for every 0.3-microgram increase in black carbon concentration per cubic meter, the risk increased by 2.8 percent.

How exactly black carbon increases myocardial infarction risk is not fully understood, but one of several theories posits that it causes inflammation and oxidative stress in the lungs.

It is theorized this ultimately makes it easier for blood clots to form in the arteries.

Sunao Kojima, vice director of Sakurajyuji Yatsushiro Rehabilitation Hospital in Yatsushiro, Kumamoto Prefecture, who led the research team, noted that a negative effect was observed even though black carbon makes up only 3 percent of PM2.5.

“It can be considered a substance that cannot be ignored and deserves attention,” Kojima said.

However, he said while potentially harmful, its impact is weaker than individual factors such as high blood pressure or smoking.

“People with multiple risk factors are more susceptible to developing an attack, but I envision PM2.5 as the final push that sends those already teetering on the edge over the cliff,” Kojima said.

In Japan, PM2.5 concentration has been measured since 2009 and has decreased annually due to measures such as exhaust gas regulations.

However, the World Health Organization (WHO) reports that most of the world’s population is exposed to air that exceeds its guideline values, and Japan’s annual average concentration is also above this level.

The team’s findings were published recently in the international academic journal Communications Medicine.