Wildfire smoke is becoming an increasing threat to pregnant women as climate change drives more frequent and intense fires, potentially undermining improvements made in air quality through reductions in pollution from transport and industry.
A new study published in Frontiers in Environmental Health examined exposure to fine particulate matter, known as PM2.5, from wildfires across the United States between 2003 and 2019. Researchers found that prenatal exposure to wildfire smoke more than doubled during the 17-year period.
The increase was particularly significant in western US states, where wildfire seasons have become longer and fires have grown more severe. Researchers found that wildfire smoke was responsible for about 65% of days when air pollution reached levels considered unsafe during pregnancy.
The findings suggest that progress in reducing pollution from human activities is being partly offset by emissions from wildfires.
“Increasing wildfire activity is systematically offsetting prenatal air quality gains,” researchers said, warning that the trend could place a disproportionate burden on low-income, rural and Indigenous communities as wildfire activity continues to intensify.
PM2.5 consists of microscopic particles that can travel deep into the lungs and enter the bloodstream. Exposure during pregnancy has previously been associated with health problems including premature birth and low birth weight.
Researchers also noted that particles produced by wildfires may pose additional risks because their chemical composition can differ from pollution produced by traffic and industrial activity. This could make wildfire smoke particularly concerning for people who are more vulnerable to air pollution.
The findings have implications beyond the United States, as Europe has also experienced increasingly severe wildfire seasons in recent years.
Countries including Greece, Portugal, Spain and France have faced major fires during successive summers, with smoke sometimes spreading across national borders. European climate and health authorities have warned that rising temperatures are contributing to conditions that increase the likelihood and intensity of wildfires.
The growing exposure has raised concerns about how public health systems can protect vulnerable groups as climate-related risks increase.
Experts say governments may need to strengthen guidance for pregnant women and other groups at higher risk from smoke exposure. Measures could include improved wildfire smoke forecasting, earlier health warnings and greater access to clean indoor air during periods of severe pollution.
The research highlights a challenge facing environmental policymakers. While decades of measures have reduced pollution from vehicles, industry and other human activities, climate change is creating additional sources of harmful air pollution.
