As California wildfires continue to rage and the Lake Tahoe area faces some of the highest air pollution levels in the world, a new study has found that breathing wildfire smoke during pregnancy increases the risk of premature birth.
The study from Stanford University, published in Environmental Research this month, estimates that the effects of wildfire smoke may have resulted in as many as 7,000 extra preterm births in California between 2007 and 2012.
Researchers combined more than 3m birth records with satellite and ground data on wildfire smoke exposures for each zip code in California. They found that the more days a mother was exposed to wildfire smoke during pregnancy, the more likely she was to face a preterm birth. The effects of moderate to severe exposure levels were significantly worse.
“We found that a week’s worth of smoke exposure (at these levels) was associated with a 5% increased risk and a month’s worth was associated with a 20% increase in preterm births,” said Sam Heft-Neal, the lead author on the study.
The findings compound growing evidence that smoke and the tiny particles of air pollution it produces, known as PM2.5, have dire health effects on the human body, ranging from heart attacks, strokes and asthma to mental illness.
“This stuff is tiny and it gets into the body, causes inflammation and creates a cascade of health effects,” said study co-author Marshall Burke, who is deputy director of the Center on Food Security and the Environment.
The findings come as fires continue to scorch California, with blazes such as the massive Dixie fire in the north of the state having already burned through 1.5m acres of drought-parched land. This week visitors to the Lake Tahoe region have seen air quality monitor readings shoot up into the hazardous 600 index range, far worse than current readings in some of the world’s most polluted cities including Delhi, India, and Jakarta, Indonesia.
The school district in the Reno, Nevada, area closed all public schools serving 67,000 students in Reno, Sparks and Incline Village on Monday because of the air pollution, according to the Associated Press. Residents were urged to remain indoors as much as possible.
The Stanford study attributed 2,000 preterm births to smoke in the state in 2008, the worst year of the study period. But, sadly, the authors said, wildfire smoke levels have gotten far worse since the end of the study period in 2012.
“The smoke exposure then was dramatically less back then,” said Burke. “Four of the last five years have seen worse smoke than any year in our sample.”
During California’s historic 2020 fire season, more than 4m acres burned and half of the state’s population experienced a month of unhealthy levels of wildfire smoke, according to a Stanford release on the study.
The study found that pregnant women in wealthy neighborhoods were just as likely to suffer the effects of the smoke as those in low income areas.
Heft-Neal said the findings indicate that pregnant women should take extra measures to protect themselves from wildfire smoke, such as staying indoors, and using air filtration systems and high quality masks.
Burke added that the societal costs of air pollution from wildfire smoke justify further steps from the state and federal government to prevent massive wildfires. He said each premature birth costs society an average of $70,000, so the benefits of reducing such early births alone could have “enormous societal benefits”.
Those benefits could go a long way toward paying for measures to reduce the fuel available for fires, like mechanically thinning forests and prescribed burns, he said.
“Our research highlights that reducing wildfire risk and the air pollution that accompanies it is one way of achieving these societal benefits,” he said.