You don’t have to be near a forest fire for it to affect your health.

Summer wildfires have hit multiple areas of California scorching tens of thousands of acres.

In Europe, forest fires have affected a number of countries and caused dozens of deaths in Portugal.

The intense smoke and heat of a forest fire are clearly causes of immediate dangers to those in its path.

However, the flames can also cause unexpected health threats, including heart attacks, for those fleeing the fire or just living nearby.

How do forest fires lead to heart attacks?

Past research has found those living near forest fires are at increased risk for major cardiac events while smoke is in the air.

Tiny particulates from wildfire smoke can travel through the air and increase the risk for cardiac events in people who are miles away, even in areas that aren’t acutely affected by the flames.

In a 2015 study researchers found that there was an almost 7 percent increase in cardiac arrest in one Australian state during one .

“These particles may act as a trigger factor for acute cardiovascular health events,” Anjali Haikerwal, a doctoral candidate at the School of Public Health and Preventive Medicine at Monash University in Australia and lead author of the 2015 study, said in a statement.

Dr. Richard Josephson, a cardiologist at University Hospitals Cleveland Medical Center, explained that the cardiovascular system can come under increased strain from these particulates.

“There are a variety of toxic chemicals in the smoke and small particulate air pollution in the smoke that are bad for the cardiovascular system,” Josephson told Healthline.

While particulates enter the body through the lungs, they can seriously irritate or damage the cardiovascular system.

“It can cause activation of the clotting system and constriction of blood vessels,” Josephson said.

That can increase the risk of heart attack.

Those with cardiac risk factors such as high blood pressure are more at risk for having a heart attack or other major cardiac event.

“In days and weeks where air pollution is bad, the risk of people having cardiovascular events goes up,” Josephson said.

Josephson pointed out that exposure to smoke and the resulting chemicals can also result in long-term damage to the cardiovascular system, increasing a person’s risk of cardiac disease years later.

A special risk for firefighters

For those closest to the blaze, a trifecta of heat, smoke, and physical strain puts firefighters at significantly increased risk for heart attacks.

A published in the American Heart Association’s journal Circulation, found that heat and physical exertion can cause blood clots and impair blood vessel function increasing the likelihood of a major heart attack.

Josephson pointed out that firefighters work in extreme situations and their bodies react accordingly.

“Adrenaline levels go up very high and blood pressure can go up very high,” he said.

Cardiac events are so dangerous for firefighters they account for 45 percent of all on-duty deaths, according to the .

“These harsh conditions can cause injury to the heart muscle in healthy firefighters and may explain the link between fire suppression and risk of heart attacks,” said Dr. Nicholas Mills, lead researcher and chair of cardiology and consultant cardiologist at the University of Edinburgh in Scotland said in a .

While it can be difficult to pinpoint when a heart attack is going to occur, those concerned about air pollution and cardiac risk can monitor their local air quality from the daily reports released by the .