HEALTH

What We Don't Know About Wildfire Smoke Should Scare Us

When it comes to the long-term effects of smoke exposure, "we're all research subjects," one public health expert said.

Plumes of wildfire smoke around California have left the state with air quality so bad in some areas that it was literally off the charts. Even in cities hundreds of miles away from the blazes, the smoky air has been so unhealthy to inhale that officials warned against anyone going outside. 

There’s clear consensus that wildfire smoke is bad for us in the short term: It leaves people coughing and suffering from headaches and sore throats; it inflames some existing health conditions, such as asthma and heart problems; and it may even make a person more susceptible to COVID-19 symptoms. But when it comes to the long-term effects that wildfire smoke may have on people, the experts still have a lot more questions than answers.

“Unfortunately for all of us, we’re all research subjects,” said Dr. Gina Solomon, a principal investigator at the Public Health Institute and a clinical professor of medicine at the University of California, San Francisco. “[There are] a lot of people that are being exposed repeatedly to wildfire smoke, so we’re going to know a lot more in the coming years.”

The San Francisco-Oakland Bay Bridge is seen under a smoke-filled sky due to various California wildfires earlier this month.
The San Francisco-Oakland Bay Bridge is seen under a smoke-filled sky due to various California wildfires earlier this month.

No communities have been more of a test subject than those across California, especially Butte and Lake counties in the northern part of the state. Foothill towns in those areas have seen massive fires year after year as climate change drives record-high temperatures and severe droughts. 

The outstanding question, Solomon said, is whether particulate matter ― the dangerous mixture of tiny particles and liquid droplets in the air ― in wildfire smoke is just as toxic as the air tainted by cigarettes, tailpipes and other year-round pollutants.

“If wildfire smoke particulate matter behaves just like other particles, then the picture is not good for for long-term health,” she said. Exposure to particulate matter from air pollution reduces lung function, and it’s especially harmful for children since their lungs are still developing, she added.

There are still big gaps in our knowledge, largely because wildfires have never been as bad as they’ve been in recent years and because smoke is so hard to isolate from other air pollutants.

A review of the research on this subject in 2017, when some of the worst wildfires in history hit California, emphasized the missing puzzle pieces in understanding the long-term impact of particulate matter in wildfire smoke. The review noted that it remains “completely unknown” what the cumulative effect of repeated exposure may have on a person’s lung health.

One of the authors of that review was Dr. Lisa Miller, the associate director of research at the California National Primate Research Center and a professor at the University of California, Davis. Miller is one of the experts working to expand what we know about the long-term effects of smoke exposure.

When severe wildfires left her Davis-based research facility blanketed in smoke in 2008, Miller had the idea to observe wildfire smoke exposure on baby monkeys living in enclosed, half-acre fields outdoors at the facility. During the 10-day period of smoky conditions, the amount of particulate matter in the area was far above the federal standard for healthy air and sometimes more than doubled the safe amount per cubic meter.

The study followed those monkeys from infancy to around three years of age, and it led to grim findings.

“The animals that were exposed to the smoke during that period of time when they were babies had deficiencies in their immune system, and their lungs appear to be more stiff,” Miller said.

A stiff lung in humans is early evidence of pulmonary fibrosis, a condition in which people’s lungs become irreversibly scarred and less functional, leaving them short of breath, she added.

The study also showed some evidence that the animals affected by the smoke exposure passed on immune deficiencies to their offspring, leaving both of them more susceptible to disease.

A man walks along the Redwood Highway by the Pacific Ocean coast as smoke from wildfires covers an area near Orick, Californi
A man walks along the Redwood Highway by the Pacific Ocean coast as smoke from wildfires covers an area near Orick, California, on Sept. 9.

Miller and the others involved in the study are now in the process of presenting more data showing that the impact of the smoke on those monkeys was maintained as they aged further into adulthood.

One of Miller’s biggest concerns is that these fires are burning up more than just forests — they’re burning up artificial materials in people’s homes, especially plastics that emit dangerous chemicals when they burn.

“I think it’s important for people to really understand that this isn’t just wood burning,” she said.

Solomon agreed, saying, “There’s other stuff in that smoke.”

“If you live near the fire, there’s a lot a lot of other material, including chemicals like benzene that are emitted from combustion that are very, very toxic substances,” she said.

Solomon has seen that problem show up in unexpected places. When a small group of residents in Santa Rosa, California, returned home after the catastrophic Tubbs fire in 2017, several of them found that their tap water suddenly had a strong, foul odor. Testing found that their water contained extraordinarily high concentrations of benzene, a carcinogen known to cause leukemia in humans.

I think it’s important for people to really understand that this isn’t just wood burning. Dr. Lisa Miller, associate director of research at the California National Primate Research Center

“Levels were about up to about 1,000 times higher than the legally allowable concentrations,” Solomon said.

When the same phenomenon was observed in Paradise, California, after people returned home following the 2018 Camp fire, Solomon secured funding to try and figure out what was happening. She’s still putting the data together, but one explanation appears the most likely: The water systems lost pressure when the fires stormed those communities and pipes instead sucked in wildfire smoke, which contains benzene, she said. Those levels of benzene were made worse by all the incinerated plastics inside people’s homes and the charred plastic water pipes, which both released benzene when they burned.

“Anytime you have a fire come through and there’s a loss of pressure in the system, there’s a risk of having severe contamination of the water system afterwards,” Solomon said.

“Unfortunately,” she concluded, “this can happen again.”