As California grapples with massive wildfires in recent years, a new Kaiser Permanente study raises new concerns about the possible increased risk of heart attacks, heart failure, and stroke from air pollution caused by wildfires.

The study included 3.2 million adults who were Kaiser Permanente members in Northern California during the Mendocino Complex and Camp fires. The Mendocino Complex fire burned in July and August of 2018, while the Camp fire in Butte County burned in November of 2018.

The researchers wanted to see how the air pollution from the fires affected the heart. So they looked at the rates of heart attacks, heart failure, stroke, and cardiovascular deaths that occurred in Kaiser Permanente members in Northern California from July to December 2018. They compared days when the fires caused a large amount of bad air pollution with the days of good air quality.

Cardiovascular risk

The researchers found the Mendocino Complex fires increased the risk of cardiovascular problems.

There was a 23.1% increased rate of heart attacks, heart failure, stroke, and cardiovascular deaths during the days with poor air quality.

There also was a 35.8% increased rate of death from any cause when air pollution levels were high, according to the study that was published this month in the Journal of the American Heart Association.

However, the researchers found no increased risk of heart disease or death tied to high air pollution during the Camp fire. Other research teams have done studies that also had conflicting results.

“This finding surprised us because we know from many other studies of air pollution that the high levels of pollution we saw are not safe,” said lead author Stacey E. Alexeeff, PhD, a research scientist at the Kaiser Permanente Northern California Division of Research. “Both fires spread smoke across the region. And both led to air quality levels that were above what the Environmental Protection Agency believes is safe. In fact, there was one day when the Camp fire caused the worst air pollution in the world.”

Each fire burned more than 100,000 acres and spread clouds of smoke across Northern California. The Camp fire was the deadliest and most destructive in California’s history, while the Mendocino Complex fire was the third largest, according to CalFire data.

“Air pollution is the world’s fourth leading cause of disease and death. And most of these deaths are due to  cardiovascular disease, not lung conditions or cancer,” said senior author Jamal S. Rana, MD, PhD, a cardiologist at KP Oakland and an adjunct investigator at the Division of Research. “The recent horrific wildfires in Los Angeles are yet another awful reminder that climate change is a real threat to public health.”

It’s not clear why the pollution from the Mendocino Complex fire caused more heart problems than the Camp fire.

“It could be because different types of materials burned in each fire,” said Alexeeff. “It’s also possible that people did more to protect themselves from the smoke during the Camp fire. Or it could be that because the Mendocino Complex fire occurred first, it affected the people most at risk. We need more research to help us learn the answers.”

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