SAN FRANCISCO ― As California continues to weather its worst blazes in state history, the specific impacts of wildfire smoke on human health continue to elude scientists.
Since igniting earlier this month, the cluster of fires in the state’s Wine Country have killed more than 40 people and destroyed at least 5,700 structures, but the consequences extend to far beyond those in the blaze’s path. The fires have created a record high amount of air pollution spreading across the San Francisco Bay Area ― about as much produced by cars in the state in a given year, one air quality analyst told CNN. But scientists also say more research is needed to understand how wildfire smoke affects residents’ health.
That smoky, polluted air is full of microscopic pieces of particulate matter around 2.5 micrometers or smaller, or PM 2.5, which are too small to be caught by our lungs’ filtration system and instead enter our bloodstreams. Those particles are what turned skies brown and hazy as far as San Francisco 50 miles away, prompting warnings to stay indoors and coughing, wheezing and other side effects among many of those exposed to the abysmal air.
Numerous studies have linked premature death in people with heart or lung disease, heart attacks, asthma and other respiratory issues to inhalation of such particles, which are also emitted year-round by vehicles and other pollution sources. Other recent studies have linked PM exposure to increased kidney disease risk and shortened lifespans of those exposed to it in the womb.
What’s less clear is whether PM in wildfire smoke ― which has a unique chemical makeup and comes in short, intense episodes during and after a fire ― presents a different set of risks than the particles produced by cars and other daily sources, said Jia Coco Liu, a postdoctoral fellow at Johns Hopkins University who’s authored several studies exploring the link between wildfire pollution.
The biggest question that she says needs to be solved is “whether the composition of fine particulate matters from wildfire smoke is more harmful or less harmful than those from traffic,” she said.
Her recent research has made some strides in bridging that gap. In a study published in January in the journal Epidemiology, Liu and her co-authors found that during times of high exposure to wildfire smoke in western U.S. states, there was a 7.2 percent increase in those over 65 admitted to hospitals for respiratory issues, regardless of any pre-existing conditions.
The most common issues people were admitted for were respiratory tract infections and chronic obstructive pulmonary disease, an umbrella term that includes emphysema, chronic bronchitis and asthma.
Her research has also found that women are more vulnerable than men to health issues linked to wildfire smoke, likely because they have smaller lung volumes. Other research has found the same for children, she said.
But pinpointing these effects of wildfire pollution, she said, has proven to be a challenging task.
“It is very difficult to isolate pollution specifically from wildfires” while other pollution sources are constantly churning PM into the atmosphere, she said. The number of studies may also be stifled by the limited interest in the subject. “It is also a regional issue ... it is not a huge concern in majority of the states in the U.S.,” she said.
Other scientific inquiries into the effect of wildfire smoke on health have also found that current research is too sparse. A review out of the University of California, Davis, earlier this month raised concern about the scarcity, noting that more studies are needed to figure out whether chemicals and pesticides applied to forests and farmlands change the composition of the pollution.
“It’s possible that what distinguishes it are the chemicals humans add to the environment, but researchers haven’t paid enough attention to this yet,” Jerold Last, a UC Davis professor and researcher on the environmental causes of disease, said upon the release of the review he co-authored.
Breathing in carcinogens such as arsenic present in wildfire smoke, UC San Francisco physician John Balmes told New Republic last week, could possibly cause cancer, but again, “that hasn’t been well-studied,” he said.
Currently, the Environmental Protection Agency is also hoping to gain some understanding of the link between wildfire smoke and illness by crowdsourcing information. Its newly launched Smoke Sense, a project launched in August and running through October, asks people to report wildfire smoke conditions and their health symptoms through an app.
It’s the kind of undertaking Liu would like to see more of.
″As wildfires are getting more frequent and intense in the recent years, it is getting more attention and more research has been done,” Liu said. “So hopefully there will be more scientific information about wildfires in the coming years.”