Wildfire smoke and extreme summer heat are becoming more common in many parts of the world. When these two dangers happen at the same time, they can create a serious threat to human health.
Experts from the American Heart Association are warning that this combination may be especially dangerous for people with heart disease, but it can also affect otherwise healthy people.
Large wildfires burning in Canada have recently sent smoke across many parts of the United States.
At the same time, many communities have been experiencing unusually high summer temperatures.
Together, these conditions increase the strain on the heart and lungs. The warning is based on evidence from several scientific studies, including research published in Circulation and the Journal of the American Heart Association.
Many people think wildfire smoke mainly harms the lungs, but it can also damage the heart. Smoke contains tiny particles known as fine particulate matter.
These particles are so small that they can travel deep into the lungs and even enter the bloodstream, where they may increase inflammation, affect blood vessels, and raise the risk of heart problems.
According to Dr. Manesh R. Patel, volunteer president of the American Heart Association, smoke can worsen existing heart disease and may even trigger heart attacks or other serious cardiovascular events in people who were not previously known to have heart disease. Because wildfire smoke can travel hundreds or even thousands of kilometers, communities far from the fires may still be exposed.
Researchers have found that extremely hot weather also places extra stress on the body. High temperatures force the heart to work harder to cool the body, increasing the risk of dehydration and lowering blood pressure. These changes can become dangerous, especially for older adults and people with chronic illnesses.
One study reported that the risk of dying from a heart attack nearly doubled when extreme heat occurred together with high levels of air pollution. Women and older adults appeared to face an even greater risk. Another study found that heavy wildfire smoke increased the risk of out-of-hospital cardiac arrest by as much as 70 percent.
Scientists have also linked wildfire smoke to more emergency department visits for heart attacks, irregular heart rhythms, heart failure, stroke, and blood clots in the lungs. These findings show that smoke affects much more than breathing alone.
Health experts recommend limiting time outdoors when smoke levels or temperatures are high. Staying inside with doors and windows closed, using air conditioning with high-quality filters, and running portable air cleaners can reduce exposure. If your home becomes too hot, it may be safer to stay in an air-conditioned public building.
If you must be outside, drink plenty of water, avoid strenuous exercise, wear light clothing, and rest often in cool places. Older adults, young children, pregnant women, people with heart or lung disease, and even pets need extra protection during these conditions.
This advice is supported by strong evidence, although most studies show an association rather than proving that smoke directly causes every heart problem. Even so, the findings from multiple large studies point in the same direction and make a convincing case for taking precautions.
As climate change increases the frequency of wildfires and extreme heat, simple protective steps may save lives.
If you care about heart health, please read studies about how eating eggs can help reduce heart disease risk, and herbal supplements could harm your heart rhythm.
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