New study links air pollution to increased autism risk

A recent study published on November 12 in the journal *Brain Medicine* has revealed a significant link between air pollution and an increased risk of autism spectrum disorder (ASD). The research, led by Professor Haitham Amal, a world-leading expert in nitric oxide (NO) and brain disorders, indicates that exposure to common air pollutants during pregnancy and early childhood may pose a "significant risk" of developing ASD.

According to the study, exposure to nitric oxide (NO), produced when fuel is burned, can disrupt normal brain development during critical periods. The study's authors wrote, "'NO' is a common air pollutant produced mainly by vehicle emissions and the combustion of fossil and industrial fuels. Exposure to NO and its derivative NO₂ during pregnancy and early childhood can disrupt normal brain development." Maternal exposure to NO₂ and benzene—a volatile organic compound found in vehicle emissions, industrial processes, and tobacco smoke—was also associated with an increased risk of ASD.

Professor Amal emphasized the importance of timing in exposure to these pollutants. "The timing of exposure appears crucial, with heightened vulnerability during prenatal development," he stated. The researchers found that the prenatal period, particularly the third trimester, is when the developing fetus is most vulnerable to environmental factors such as air pollution. "During pregnancy, the developing fetus is highly vulnerable to environmental factors such as air pollution, which could generate inflammatory processes affecting brain development," the study noted.

The research points to several physiological mechanisms that could explain the connection between air pollution and ASD. These include interference with brain chemicals like dopamine and norepinephrine, nitrosative stress orchestrated by nitric oxide, neuroinflammation, and oxidative stress. The study revealed that common air pollutants, including fine particulate matter and nitrogen oxides, can trigger complex biological cascades affecting brain development. "Air pollution exposure during pregnancy can activate the mother's immune system, leading to inflammation and altered fetal brain development," the researchers explained. "Elevated concentrations of inflammation-related cytokines in maternal serum in utero and children during their early life are associated with worse neurodevelopmental outcomes."

The study also highlights the interaction between genetic predisposition and environmental factors. Individuals with a genetic susceptibility to ASD may be more vulnerable to the harmful effects of air pollution exposure. Professor Amal noted, "The research suggests that individuals with genetic predisposition to ASD may be more vulnerable to the harmful effects of air pollution exposure." He added, "This interaction between genetic and environmental factors opens new avenues for understanding ASD’s complex etiology."

Exposure to fine particulate matter such as PM2.5 and PM10—tiny particles that can cross the placenta—was identified as a concerning factor for ASD. These pollutants, primarily from vehicle emissions and industrial processes, can harm fetal brain development. The findings raise important questions about protective measures for pregnant women in highly polluted areas. The implications extend beyond individual health to public policy, suggesting that cities may need to adapt urban planning to safeguard vulnerable populations from air pollution.

The researchers emphasized the need for comprehensive studies examining the combined effects of multiple pollutants, particularly during specific developmental windows. Understanding these interactions could prove crucial for developing effective preventive strategies. The team suggests that future studies may focus on identifying biological markers capable of predicting the risk of ASD at early stages, allowing for prevention and early intervention. The review highlights promising directions for biomarker development, potentially enabling early identification of at-risk individuals, as global ASD prevalence reaches 1–1.5% of the population.

Taking measures to reduce exposure to air pollution and support clean air is vital for the overall well-being of the community, especially as nearly 40% of Americans live in areas with unhealthy levels of air pollution. The researchers concluded that despite scientific progress, there is a need for policies that reduce exposure to air pollutants, especially for pregnant women and infants, which may lead to a reduction in the risk of developing autism spectrum disorders.

Professor Amal acknowledged that while increased public awareness might contribute to the rising number of ASD diagnoses, the research clearly indicates that nitric oxide plays a key role in autism. Previous studies support these findings; for instance, Harvard scientists found that fine particulate matter in air pollution increased the risk of ASD by 64% during early childhood and by 31% during prenatal periods.

According to the most recent data from the U.S. Centers for Disease Control, 1 in 36 children have been diagnosed with ASD, an increase from 1 in 44 just two years prior. Genetic factors play a significant role in the development of autism, and the interaction between genetic and environmental factors affects how many children develop ASD.

Sources: Neuroscience News, Newsmax, People

This article was written in collaboration with generative AI company Alchemiq