It’s well-established that wildfire smoke, something that is becoming more frequent because of climate change, is bad for our health, causing asthma attacks, cough, congestion and worse.
Now, a new study gives even more reason to be concerned. Recent research published in the journal Environmental Science and Technology found that pregnant people who were exposed to wildfire smoke in their third trimester had a higher risk of having a child with autism.
The study was conducted by Tulane University researchers in New Orleans, who looked at recorded wildfire smoke in Southern California and examined data from 200,000 births between 2006 and 2014. The study’s authors estimated wildfire smoke exposure for each person by using the pregnant person’s address (or addresses, if they moved during the time) to determine smoke exposure levels and the number of smoke events. Researchers then looked at autism diagnoses from the baby’s providers.
Specifically, researchers looked at exposure to PM 2.5, which are particles commonly found in wildfire smoke that are 2.5 micrometers and smaller and can be inhaled and end up in the bloodstream. Colleen Reid, an environmental epidemiologist and health geographer with the University of Colorado Boulder, previously told HuffPost that no amount of PM 2.5 exposure is safe.
Tulane researchers found that the more time a pregnant person was exposed to wildfire smoke, the higher the risk of an autism diagnosis by age 5 for their child. It wasn’t about the wildfire smoke concentration, but rather the total number of days a pregnant person was exposed to smoke, lead study author David Luglio, a post-doctoral fellow with the Celia Scott Weatherhead School of Public Health and Tropical Medicine at Tulane University, told HuffPost.
When compared to a pregnant person with no wildfire smoke exposure, those who had more than 10 days of wildfire smoke exposure in their third trimester had a 23% higher chance of having a child with autism. When exposed to wildfire smoke for six to 10 days, that number dropped to 12%. Pregnant people exposed to one to five wildfire smoke days were 11% more likely to have a child with an autism diagnosis.
This study does have limitations. It is unknown if study participants evacuated during wildfire smoke events or if they used (or did not use) protective measures such as masks and indoor air filters.
This does not mean wildfire smoke exposure during pregnancy causes autism, but it is an area where more research is needed.
“This is not definitive causation. It’s just an association. It’s a start to look at specific types of air pollution, and we can go from there,” Luglio told HuffPost.
The cause of autism is complicated and not totally known; it can be genetic, and research is ongoing to determine what environmental factors (such as air pollution) can also play a role.
“For me, the relationship between environmental policy and public health is one aspect to think about with this … we’re getting better able to identify not just the genetic causes,” said Dr. Sinan Omer Turnacioglu, interim division chief of neurodevelopmental pediatrics and neurogenetics at Children’s National Hospital in Washington, D.C.
Turnacioglu, who was not affiliated with the study, told HuffPost that experts are starting to gain a “better awareness” of what could contribute to autism from an environmental standpoint. “This is a really important study along those lines,” he continued.
Dr. Hanna Stevens, a professor of psychiatry at the University of Iowa, told HuffPost that the new study has “some overlaps here with other things that have been studied with respect to air pollution. There have been a couple of big studies, actually by some of these same authors in the same data set … of a relationship of particulate matter and exposure to air pollution with the diagnosis of autism.” Stevens was also not affiliated with the new study.
Existing research shows there may be a link between prenatal air pollution exposure and autism risk. “So, the fact that this dives deeper into that is actually helping us understand that relationship better and understand where to look further with more research … that needs to be done,” Stevens noted.
Unlike past research, though, this study looks at wildfire smoke as an environmental pollutant and a stress exposure, Stevens added, “which combines different elements that I think matter for consideration of prenatal exposures.” Both stress and pollutants can be “disruptive” to a pregnant person’s health and, likely, a baby’s developing brain, Stevens said.
“We think that all of these things ― chemical exposure, stress experiences ― change the physiology of the mother, and probably change the physiology of the placenta, which is a combined maternal-fetal organ that is really responsible for everything that happens to the fetus,” Stevens explained. The placenta “provides a lot of supportive factors, transports nutrients from the mother, provides oxygen to the developing fetus.”
If the placenta is coping with a chemical exposure, this can increase oxidative stress within the cells in the placenta, Stevens said. This can impact the transportation of nutrients and also “have more direct effects on perpetuating oxidative stress in the developing fetus,” Stevens explained. “And all of these things are very, very important — nutrients, the level of oxidative stress, how cells are able to do what they’re supposed to do — for brain development.”
Moreover, study leaders found that the smoke exposure during the third trimester carried the highest risk of autism diagnosis.
“So, we’re really thinking about later stages of fetal-brain development … I think there’s probably something about those later periods of brain development that’s increasing that risk,” Turnacioglu said.
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What this means for you:
Studies like this are, understandably, stressful and worrisome. That isn’t the goal of this research, according to Stevens. Instead, it’s to help show leaders what needs to be done to help people; Stevens stressed that this study was National Institutes of Health-funded, which speaks to the importance of having NIH backing and funding for big studies.
“When information comes out like this, it’s not all up to you … but at the same time, following recommendations for good prenatal care is one of the most fundamental things,” Stevens said. This means staying in touch with your doctor and following their guidance regarding your own health and the health of your unborn baby, she added.
While wildfire exposure is not a direct cause of autism, it is a potential environmental risk factor, the corresponding study author, Mostafijur Rahman, assistant professor of environmental health sciences at the Celia Scott Weatherhead School of Public Health and Tropical Medicine at Tulane University, told HuffPost.
There’s no need to panic, but overall, wildfire smoke exposure is bad for you, whether you’re pregnant or not. If there is a wildfire event in your area, stay indoors when the air quality is poor, use an air purifier in your home and avoid outdoor physical activity during a smoke event, Rahman said. Most phones have air quality information in the weather app, and sites like airnow.gov also provide local air quality data.
Moreover, if you know you had wildfire smoke exposure during pregnancy, particularly during the third trimester, closely monitor your baby’s development, said Turnacioglu.
“Make sure you’re checking in with your pediatrician [and] your pediatrician is doing the surveillance,” Turnacioglu noted, “and screening for autism to get a family connected with early intervention as soon as signs appear.”
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