Smoke from wildfires on the West Coast may be responsible for more heart attacks, strokes, asthma and other conditions in the past few weeks, and the numbers could continue to rise as the massive blazes impact air quality, according to new Stanford University research.
According to one estimate, the recent wildfire smoke may have caused 1,200 excess deaths — which would not have happened otherwise — and 4,800 additional emergency room visits among people ages 65 and older throughout California, said researchers Marshall Burke and Sam Heft-Neal, an associate professor of earth system science and research scholar at the Center on Food Security and the Environment, respectively.
These numbers, while admittedly "back-of-the envelope" estimates, may just be the tip of the iceberg. In addition, small particles of toxic substances beyond smoke, the length of exposure and concentration of the smoke, and the increasing frequency of pollution caused by more and larger wildfires are contributing to health hazards for Bay Area residents and throughout the West, the researchers said.
The U.S. Environmental Protection Agency's AirNow data showed records of the key air pollutant PM 2.5 collected from Aug. 1 through Sept. 10 were double to five times higher than the average air quality in the Bay Area, Burke and Heft-Neal wrote in an online post in the publication Global Food, Environment and Economic Dynamics. Their research has not undergone a peer review.
This "massive" increase meant that many more of these particles, which are about 1/30th of the diameter of a human hair, can easily be inhaled, Burke and Heft-Neal said.
When looking at how much one day of these additional amounts of smoke increases mortality over 30 days starting from Aug. 1, the estimate rises to 3,000 deaths, they said, adding these numbers could be conservative. It's likely that smoke pollution is having adverse health impacts on the very young and other populations with chronic medical conditions, they said.
"This is just in California alone! And just for people aged 65-plus. Oregon and Washington are being hit very hard right now, too, and non-elderly are also surely affected," they wrote.
The contribution of wildfire smoke to air pollution is also on the rise. About 15 to 20 years ago, 5% to 10% of the air pollutant PM 2.5 was from wildfire smoke. In more recent years, it represents 25% nationally. In some regions, particularly in the West, it has accounted for 50% or more in some years, Burke said during a Sept. 18 webinar by Stanford's Woods Institute for the Environment.
Some studies have found that two or three days of bad air quality from wildfire smoke causes a two-fold increased rate of asthma in children. In the elderly, it leads to a potential 40% increase in strokes and heart attacks in people over 65 years old, said Dr. Kari Nadeau, director of Stanford’s Center for Allergy & Asthma Research. Nadeau and Dr. Mary Prunicki, the center's director of air pollution and health research, are conducting a multiyear study of the long-term effects of wildfire smoke on firefighters and the public.
They also recently searched the Stanford Hospital Emergency Department's electronic medical record system during heavy smoke days in August and compared the data to a period of time prior to the wildfires. They found increases in asthma, heart attacks and strokes during the week of wildfires compared to the week before the fires began, Nadeau said.
"The smoke from wildfires goes through the lungs and the airways and can be absorbed into the blood. There are over 400 toxins associated with wildfire smoke, which have a multitude of bad effects on the body. In the blood, these toxins can activate the immune system and platelets and the lining of blood vessels. When this happens, the inflammation can induce clots, which lodge in the heart or the brain vessels and cause heart attacks or strokes, respectively. Asthma can get worse with wildfire smoke because the smoke gets into the lungs and causes irritation and muscle spasms, which lead to wheezing and difficulty breathing," she told Stanford News Service in August.
Prunicki said that the wildfire smoke could also impact the severity of COVID-19 infections. Air pollution is known to cause immune-system changes, and research has shown that the particulate matter in the PM 2.5-size range can reduce life expectancy. About 80% of particles in wildfire smoke are in that range, she told Stanford News.
Their own research has shown increases in inflammatory markers in teenagers exposed to wildfire smoke. "Less is known about long-term impacts of wildfire smoke exposure on health, which is why our work with retired firefighters is so important. Given that areas of elevated air pollution are associated with increased COVID-19 rates, exposure probably renders the body less able to fight off viral infections, such as COVID-19," she said.
Wildfire smoke might even be more dangerous than smoke from controlled burns, which simply burn off excess vegetation as a fire-management tool. That's because there are other substances burning, such as paint, thinners and plastics when homes and cars catch fire, Lynn Hildemann, a professor of civil and environmental engineering, said during the Woods webinar. As particles burn and are carried in the air, they undergo chemical processing even days later that can make their effects worse, she said.
The best protection against the smoke is to remain indoors with windows and doors closed and to have homes properly sealed so smoke doesn't enter through cracks. An air filter is useful, but only for one room. It is not effective to clean an entire house, she said. When outdoors, an N95 mask offers the best protection, but they are in short supply due to the COVID-19 pandemic, she said.