Prenatal Pollution Exposure Linked to Lower Cognitive Scores in Early Life

Summary: Maternal exposure to air pollution during mid-to-late pregnancy was associated with lower scores on tests of cognition, language, and motor skills in children at the age of two.

Source: University of Colorado

Toddlers whose moms were exposed to higher levels of air pollution during mid- to late-pregnancy tend to score lower on measures of cognition, motor coordination and language skills, according to new University of Colorado Boulder research.

Published today in the journal Environmental Health, the study of Latino mother-child pairs is among the first to assess the link between prenatal pollution exposure and brain development in infancy. It adds to a growing body of evidence suggesting that exposure to dirty air during critical windows of development can have potentially lasting impacts on children’s health.

“Our findings suggest that pollution exposure, particularly during mid- to late-pregnancy, may negatively impact neurodevelopment in early life,” said senior author Tanya Alderete, an assistant professor of integrative physiology at CU Boulder.

For the study, the research team followed 161 healthy mother-infant pairs residing in Southern California and enrolled in the Mother’s Milk Study, a longitudinal study of infant health. Participants provided detailed histories of where they had lived.

Researchers then used the U.S. Environmental Protection Agency’s Air Quality System, which records data from ambient monitoring stations around the country, to calculate the mothers’ exposure to pollutants from roadside traffic, industry, wildfire smoke and other sources during pregnancy.

When the children reached age 2, they underwent a series of neurodevelopmental tests, assessing cognitive, motor and language skills.

After taking into consideration socioeconomic status, number of times the baby was breastfed per day, whether the infant was early, late or on time, the mother’s weight, the baby’s birthweight and other factors that could influence results, the study found that 2-year-olds exposed prenatally to more inhalable particulate matter (PM 10 and PM 2.5) scored significantly lower on cognitive tests. For instance,  those exposed to PM10 levels at the 75th percentile compared to the 25th percentile scored about 3 points lower.

Put another way, 16% of participants had a composite cognitive score that indicated some degree of impairment. If all participants had been exposed to as much pollution as the 75th percentile, the prevalence of cognitive impairment at age 2 would be 22%.

Mid- to late-pregnancy key

When the exposure occurred mattered, according to the study, with exposures in mid- to late-pregnancy proving particularly detrimental to neurodevelopment, said first author Zach Morgan, who graduated in May with a master’s degree in integrative physiology.

“The brain develops differently at different stages of pregnancy and when you have a disruption at a critical window that can affect the trajectory of that development,” he said.

He explained that during mid- to late-pregnancy, key circuits within the brain form to support sensory, communication and motor systems.

While more research is needed to understand just how pollution impacts the developing brain, previous research suggests inhaled pollutants may come into direct contact with the fetus, causing systemic inflammation and oxidative stress that can interfere with neurodevelopment.

Alderete’s own research has also shown that exposure to air pollution can impact a baby’s gut microbiome in ways that promote inflammation, which could also impact the brain.

Other studies in older children have found associations between prenatal exposure to pollutants and reductions in white matter, cortex thickness and blood flow in the brain as well as lower IQ scores.

This shows a diagram from the study
Exposure to air pollution during pregnancy may adversely impact neurodevelopment by promoting inflammation and oxidative stress. Credit: CU Boulder

The study was restricted to Latino infants, so it is not yet clear whether the results hold for the general population.

Alderete noted that 90% of the world’s population is exposed to particulate matter levels exceeding recommended levels, and the burden of exposure is often higher among racial and ethnic minorities and low-income populations. (One EPA study found that racial minorities are exposed to as much as 1.5 times more airborne pollutants than white counterparts).

Additionally, other research by Alderete has shown that Latinos in Southern California tend to live in adverse environmental conditions, including those that have been linked with poor neurodevelopmental outcomes.

“Our findings highlight the importance of addressing the impact of pollution on disadvantaged communities and point to additional steps all families can take to protect their health,” said Alderete.

She cautioned that just because a woman was exposed to high levels of pollution while pregnant does not mean that her child will have lasting cognitive deficits.

But she does recommend that pregnant women be vigilant in avoiding airborne pollutants when possible, particularly in the second and third trimester. They should also avoid exercising outdoors on high pollution days; invest in an air filtration system inside the home; open the windows while cooking; and steer clear of secondhand smoke.

“This is just one of the many things parents-to-be should be aware of to give their child the best start possible,” she said.

About this pollution and cognitive development research news

Author: Lisa Marshall
Source: University of Colorado
Contact: Lisa Marshall – University of Colorado
Image: The image is credited to UC Boulder

Original Research: Open access.
Prenatal exposure to ambient air pollution is associated with neurodevelopmental outcomes at 2 years of age” by Tanya Alderete et al. Environmental Health


Prenatal exposure to ambient air pollution is associated with neurodevelopmental outcomes at 2 years of age


Higher prenatal ambient air pollution exposure has been associated with impaired neurodevelopment in preschoolers and school-aged children. The purpose of this study was to explore the relationships between prenatal ambient air pollution exposure and neurodevelopment during infancy.


This study examined 161 Latino mother-infant pairs from the Southern California Mother’s Milk Study. Exposure assessments included prenatal nitrogen dioxide (NO2) and particulate matter smaller than 2.5 and 10 microns in diameter (PM2.5 and PM10, respectively). The pregnancy period was also examined as three windows, early, mid, and late, which describe the first, middle, and last three months of pregnancy. Infant neurodevelopmental outcomes at 2 years of age were measured using the Bayley-III Scales of Infant and Toddler Development. Multivariable linear models and distributed lag linear models (DLM) were used to examine relationships between prenatal exposures and neurodevelopmental scores, adjusting for socioeconomic status, breastfeeding frequency, time of delivery, pre-pregnancy body mass index, and infant birthweight and sex.


Higher prenatal exposure to PM10 and PM2.5 was negatively associated with composite cognitive score (β = -2.01 [-3.89, -0.13] and β = -1.97 [-3.83, -0.10], respectively). In addition, higher average prenatal exposure to PM10 was negatively associated with composite motor (β = -2.35 [-3.95, -0.74]), scaled motor (β = -0.77 [-1.30, -0.24]), gross motor (β = -0.37 [-0.70, -0.04]), fine motor (β = -0.40 [-0.71, -0.09]), composite language (β = -1.87 [-3.52, -0.22]), scaled language (β = -0.61 [-1.18, -0.05]) and expressive communication scaled scores (β = -0.36 [-0.66, -0.05]). DLMs showed that higher prenatal air pollution exposure during mid and late pregnancy was inversely associated with motor, cognitive, and communication language scores.


Higher exposure to air pollutants during pregnancy, particularly in the mid and late prenatal periods, was inversely associated with scaled and composite motor, cognitive, and language scores at 2 years. These results indicate that prenatal ambient air pollution may negatively impact neurodevelopment in early life.

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