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The Science of Fire and Health

UCLA Magazine interviewed Fielding School of Public Health professors Yifang Zhu and Michael Jerrett to understand how living with wildfires and unbreathable air affects humans, physically and mentally

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Date: 
Friday, December 4, 2020
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There’s a smell that has permeated Los Angeles for months, of scorched sage, sometimes wood smoke, often accompanied by falling ash. Under campfire circumstances, it might be appealing; as a backdrop of urban life, it’s thick and unhealthy. The fact is, you don’t have to be running for your life to be affected by wildfire. And some of the deadliest stuff in the air is invisible.

“The most dangerous and dramatic health risks come from the fine particulate matter called PM2.5,” explains Yifang Zhu (PhD ’03), a professor of environmental health sciences at the UCLA Fielding School of Public Health, who studies air pollution and the health risks related to it for the Institute of the Environment and Sustainability. PM2.5 stands for “particulate matter” that’s 2.5 micrometers, which is superfine — 30 times smaller in circumference than a human hair.

Her research, and that of other UCLA scientists, is helping to identify the long-term and remote effects of wildfires, not just on those whose homes are threatened but also on those who breathe the polluted air. The consensus among researchers: More frequent fires and their closer proximity to communities are creating a far more serious health problem than was previously recognized.

Zhu says that during the fires this fall, the air was likely full of PM2.5 and other gaseous air pollutants, such as nitrogen dioxide and carbon monoxide, which are hazardous to our health. Coarse particles, such as PM10, can be inhaled and cause irritation, leading to a sore throat and wheezing. But PM2.5 particles are so small that they can embed in the lungs and get into the bloodstream, becoming both a respiratory and cardiovascular health risk.

“The fires are getting closer to populated areas, so exposure to air pollution is at extremely high levels,” Zhu says. “And it’s getting worse with each new fire.

“On a normal day in Los Angeles, PM2.5 pollution levels are on the order of 10 to 30 micrograms per cubic meter of air, usually around 12 or 15. During wildfires the level can go over 100; some areas showed 200. And when there are several fires, it can go even higher.”

Zhu says data for the respiratory problems are pretty clear. “For the most susceptible subgroups — those with respiratory conditions like asthma, emphysema and chronic obstructive pulmonary disease [COPD], those with lower socioeconomic status, who live in places with high air pollution to begin with, as well as children, elderly people and pregnant women — the emissions definitely add to the issues,” she says.

The COVID factor

Dr. Reza Ronaghi, a pulmonologist at the Ronald Reagan UCLA Medical Center who specializes in lung conditions and disease, says the intensity and length of this fire season have been particularly concerning, since it means higher and longer exposure to the particles.

“We worry about patients with underlying lung disease, especially those with lung cancer and cystic fibrosis,” he says. “With bronchitis, COPD, emphysema or asthma, the conditions can lead to long-term sickness, but with lung cancer and cystic fibrosis, it can lead to hospitalization and even morbidity.”

For the general population, the acute symptoms — sore throat, wheezing, burning eyes — are short-term maladies. “Once you remove yourself [from the polluted air], your body will heal,” Ronaghi says. “It will just take time.” The problem is repeated exposure to many fires and many fire seasons. “Over the years, that could lead to COPD and emphysema.”

This year’s risks have been compounded by the COVID-19 pandemic, which adds many wrinkles, because, well, the lungs. “So far, we haven’t seen research showing that the wildfires will make you more susceptible to COVID,” Ronaghi explains. “But we do worry about patients who have COVID and are exposed to the smoke and particles, which could lead to a worsening of their condition.”

He adds, “Because of COVID, people are told to stay outside to exercise. For instance, running outside of the gym. But now, because of the fires, that is a mixed message. And people get frustrated because their quality of life is affected.”

UCLA researchers, led by Michael Jerrett, Fielding School professor of environmental health sciences, are also on the path toward discovering connections between air pollution and COVID outcomes, as well as the impacts of socioeconomic status, race and ethnicity, and preexisting conditions.

Masking the problem

Can face masks offer protection against the PM2.5 that saturates the air during wildfires? “In a normal year, I would recommend wearing an N95 face mask,” Zhu says. “But this year, we are in the middle of COVID, so we have supply issues. I recommend wearing any face mask, preferably a well-fitted one that you can pinch the top [of] so it fits the shape of your nose.”

Air filters and purifiers can also help, but they have limits. “Purifiers are great, but they must have HEPA filters, or else the particles will get right through them,” Ronaghi explains. “And they will only cover a small area, so if you are in a big room and have a small machine, it won’t be enough.” Central air conditioning with HEPA filters is the gold standard, but very pricey.

Finally, Ronaghi suggests inspecting windows and cracks around your home to make sure they are leakproof, covering them appropriately and maybe even using tape.

Emotional consequences

Wildfires significantly contribute to air pollution, and when that’s combined with all the related stresses, it can negatively impact mental health.

“The wildfire situation is one of the largest threats to public health,” Jerrett says. “We’ve fought long and hard to reduce air pollution levels that were as bad as they could be back in the ’60s and ’70s. We’ve seen a reduction of 60 million metric tons, but the fires have completed wiped out our progress.”

Jerrett and his colleagues at the Fielding School's UCLA Center for Healthy Climate Solutions cite studies that show how chronic exposure to air pollution can affect mental health and may lead to depression, with symptoms that can last 18 months after the fire. “There also is evidence that living in polluted areas actually changes the brains of children and can lead to a higher risk of cognitive decline and dementia,” he says.

Jerrett and the center also conducted two smaller studies in California, which suggest that “when people have dramatic traumas in their home environment, they experience a sense of loss and feelings of dismay and longing for what was there before,” he says.

Looking ahead

“Whatever we can do to slow climate change is going to have a positive effect on public health,” Jerrett says. “I look to places like Paris, where they have spent more than $100 million to get people to bike instead of drive. There is a triple reward there: It reduces emissions, particulate matter and nitrogen dioxide; it gives people a form of functional physical activity during this pandemic; and it is an inherently physically distanced activity that people can do together, so the feelings of isolation are lessened.”

However, climate change will continue to negatively impact public health. As warmer temperatures fuel fires, trees will burn and release carbon into the atmosphere.

“Usually the forest is our best friend in holding carbon back,” Jerrett says. “But once the trees are gone, they can’t absorb the carbon dioxide that creates the ozone and global warming. The mega fires are hotter and bigger and more complex.”

And that, in turn, spreads the health effects of fire and smoke, which is sure to worsen in the years ahead.

written by Peg Moline

READ MORE - UCLA Magazine "State of Fire" Report