The contribution of wildfire smoke to the average amount of air pollution experienced by infants in the womb more than doubled between 2003 and 2019, according to a study led by researchers from the University of Maryland School of Public Health (UMD SPH).
Air pollution experienced during this prenatal period has been linked to premature birth and low birthweight, which are among the leading causes of infant illness and death.
“Our research found that by the end of the study period, wildfire smoke contributed about 4% to 13% of the average daily air pollution experienced before birth, depending on where you live. Although extremely bad air days have become far less common, most of the ones that remain are now attributable to wildfire smoke,” said Dr. Menglu Liang, UMD SPH assistant clinical professor in biostatistics and lead author of the study, published in Frontiers in Environmental Health in August.
The study found that the increased role that wildfire smoke plays in prenatal pollution exposure is partially explained by the fact that the US has been successful in reducing exposure to other sources of pollution, such as from industry or vehicles. This reduction is thanks to the Clean Air Act and other regulations as well as development of cleaner technologies.
Between 2003 and 2019 average daily exposure from non-fire sources declined by 37% and the chance of being exposed to an extremely bad air day that was caused by a non-fire source declined by about 85%. However, average exposure to pollution carried by wildfire smoke has been steadily increasing, more than doubling in hard-hit areas like the Northwest.
Nationally, the share of extreme days attributable to wildfire smoke climbed from 22% to 65%. That shift reflects a change in what causes the bad air days that remain, not an increase in their number: the share of infants exposed to at least one extreme day fell from about 67% to 22% over the same period.
The study comes as several wildfires rage across North America and Europe.
“We also found that wildfire’s share of air pollution grew fastest in places that already face other disadvantages – lower-income counties, rural areas, communities with large American Indian and Alaska Native populations and areas with few maternity and neonatal care services,” said Liang.
Liang and colleagues analyzed prenatal exposures to PM2.5 – tiny particles, 30 times smaller than a human hair, that people can inhale from various polluting sources such as power plants, industrial exhaust, wildfires and gasoline-powered cars. These fine particles pose a risk to human health and have been linked to adverse birth outcomes.
The study analyzed over 64 million live births in 48 states between 2003 and 2019. They linked these birth records to pollution measures from an atmospheric model that estimated daily air pollution from different sources, including wildfires. This model allowed the researchers to estimate how much of total air pollution was attributable to smoke versus other sources.
Researchers tracked the average daily exposure to PM2.5 during the prenatal period and the number of prenatal days that exceeded the Environmental Protection Agency’s (EPA) quality standard for particulate matter.
“As more people increasingly encounter wildfire smoke, we need to proactively help communities avoid exposures when they can and access appropriate medical care when they experience an adverse reaction,” said study co-author Dr. Michel Boudreaux, UMD SPH associate professor of health policy and management.
Ensuring people have access to respirator masks and that our homes, schools and workplaces have adequate air filtration in place are all important adaptation measures, he said.
“However, we also have to reckon with the fact that large smoke events are not going away and we must ensure that everyone has access to affordable, high quality health care services.”