Northern California wildfire smoke linked to serious health risks, emergency room visits

A new study based on California’s 2015 wildfire season indicates smoke exposure elevates risk for heart attack, stroke and other serious health conditions.|

It would seem self-evident to anyone who endured the firestorm that ravaged the North Bay six months ago that all the smoke and soot in the air during that time posed a health risk.

Public health officials said as much, advising residents - especially those with pre-existing respiratory conditions - to stay indoors whenever possible.

Now a new study strengthens the evidence that exposure to wildfire smoke contributes to serious cardiac and vascular problems, such as heart attack and stroke, in addition to the respiratory ailments long associated with smoke-filled air.

Published this week by the Journal of the American Heart Association, the report indicates that people aged 65 and older are particularly susceptible to symptoms such as cardiac chest pain, irregular heart rhythm, heart failure, stroke and pulmonary embolism after exposure to caustic smoke of the sort that filled the region last October.

The findings highlight elevated risks for conditions that can be severe and potentially disabling or even deadly - in contrast with most respiratory issues that can be remedied quickly with medical attention, said lead author Zachary S. Wettstein, a graduating medical student from UC San Francisco.

The study, based on emergency room visits during California’s 2015 wildfire season, should put people with risk factors on guard as the next fire season rolls around, the authors said. Hospitals and health care providers should be prepared for surging patient needs in the midst of wildfires, particularly as climate change increases the number and intensity of wildfires in the west.

“One of the most important things is that we need to think about more than just lung health when we’re exposed to smoke, and that there are other serious health problems that can result,” Wettstein said in an interview.

Wettstein and collaborators from the state Department of Public Health and the U.S. Environmental Protection Agency analyzed nearly 1.2 million emergency room visits in Northern and Central California between May 1 and Sept. 30 in 2015.

That year’s wildfire season included the Valley fire in Lake County, a devastating and deadly prelude of what was to come two years later in Sonoma County.

It came in September on the heels of the 69,438-acre Rocky fire and the smaller Jerusalem fire, also in Lake County. The Valley fire scorched 76,000 acres, destroyed nearly 2,000 structures, mostly homes, killed five people and burned for more than a month, sending smoke cascading throughout the region.

It was one of 20 large wildfires that burned in California during the study period, including the massive 151,623-acre Rough fire in Fresno County, one of several that persisted for more than two months.

The researchers analyzed emergency room complaints and diagnostic codes against data on smoke plumes in eight California air basins to determine exposure to light, medium or dense smoke.

They found elevated risk among all adults at all levels of smoke intensity, though cardiac and vascular problems were most pronounced when smoke was heaviest and patients were 65 or older.

About one-third of the ER visits overall were related to cardiac or vascular problems, the study said,

Among the findings: Smoky air was associated with a 42 percent higher risk of heart attack compared to smoke-free air, as well as a 22 percent higher relative risk of emergency visits for coronary artery disease.

The findings expand on well-known links between wildfire smoke and exacerbation of respiratory problems such as asthma and chronic obstructive pulmonary disease, or COPD.

Researcher Wayne Cascio, a cardiologist and director of the National Health Effects Lab at the EPA, said the study also expands on ties between cardiovascular problems and airborne particulate matter from urban sources of air pollution, such as industrial plants and vehicular traffic.

Wildfire smoke contains a variety of unhealthy substances, but the key problem is fine particulate matter, which can be drawn deep into the lungs, precipitating a series of changes that increase the chance of blood clots, constriction of arteries, inflammation and other factors that contribute to cardiac and vascular stress.

Omar Ferrari, emergency department medical director for Santa Rosa Memorial Hospital, said wildfire smoke is a little like forced cigarette consumption for the masses - something we know is bad for cardiac and vascular health.

Where young, healthy people may have the “functional reserve” to be able to absorb the impact of wildfire smoke, at least for a time, older people, especially those with other risk factors like hypertension, heart disease, diabetes or respiratory problems “are much more likely to kind of be pushed over the edge,” he said.

The October firestorm inundated Memorial’s emergency room, particularly after the fires forced Sutter and Kaiser hospitals to evacuate and shut down their own emergency rooms. And while the hospital was unable to pull specific data from that time, Ferrari said he and his staff worked overtime to address a variety of symptoms, including many likely caused by smoke.

“We had a big surge in respiratory complaints but also cardiovascular complaints,” he said.

Hearing the findings now, too late to change behavior during the October fires, is probably “not super satisfying for the people of Sonoma County,” Wettstein said.

But the increased intensity and duration of California wildfires because of climate change suggests there are many more opportunities to guard against serious, wide-scale health impacts, researchers said.

“Preparedness in the future is really important,” Wettstein said.

Those with underlying cardiac or vascular conditions - coronary artery disease, hypertension, atrial fibrillation, diabetes and others - should be particularly careful about unnecessary exposure to smoke, researchers said. That message needs get out to the wider public, they said.

“What the study showed us was it gave us a general sense of what the increased risk would be to a population when we encounter smoke, and that we are going to have an excess number of these conditions,” Cascio said. “Where the study is powerful is in helping the public health system, county public health officials and the health care systems, to think about the importance of really communicating in the future to people who are at risk, and to advise them to avoid exposure in an effort to decrease their exposure to risk.”

The North Bay firestorm has prompted several public health inquiries, including a study of firefighter health by researchers at UC Berkeley.

UC Davis scientists also are participating in a study of environmental health hazards and have surveyed about 1,500 North Bay residents about their exposure and health effects in the wake of that fire.

That online survey is still open for a few more weeks and is available at

Cascio said U.S. EPA and partner agencies are updating guidance for public health officials on training and messaging related to wildfire risks. More information is available at

Mary Callahan

Environment and Climate Change, The Press Democrat

I am in awe of the breathtaking nature here in Sonoma County and am so grateful to live in this spectacular region we call home. I am amazed, too, by the expertise in our community and by the commitment to protecting the land, its waterways, its wildlife and its residents. My goal is to improve understanding of the issues, to find hope and to help all of us navigate the future of our environment. 

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