Autism spectrum disorder (ASD) and other neurodevelopmental disorders could be triggered by air pollution, including the type emitted in car exhaust, a new study suggested — though it had some limitations.
The review, led by Hebrew University of Jerusalem, analyzed multiple studies related to autism and cellular activity. The findings were published in the journal Brain Medicine.
The researchers focused on four specific types of particles that make up air pollution: fine particulate matter (PM), nitrogen oxides (NO, NO2), sulfur dioxide (SO2) and ozone (O3).
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They also investigated four different ways in which these particles could impact the fetus.
Those four ways were neuroinflammation, oxidative/nitrosative stress (an imbalance of free radicals and antioxidants that causes cell damage), epigenetic modifications (chemical changes to DNA) and disruptions to certain neurotransmitters, according to the study.
"Increasing air pollution may significantly raise the risk of neurodevelopmental disorders, particularly ASD, due to gene-environment interactions," lead study author Haitham Amal, PhD, an associate professor at The School of Pharmacy at Hebrew University of Jerusalem, told Fox News Digital.
"Key air pollutants — such as fine particulate matter, nitrogen oxides, sulfur dioxide and ozone — are implicated in triggering harmful processes in the brain, including neuroinflammation, oxidative stress and neurotransmitter imbalances," he added.
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The risk is highest during times of accelerated development, such as prenatal and early childhood periods, according to Amal, who is also a visiting professor at Boston Children's Hospital within Harvard Medical School.
"The brain starts developing at birth and continues to develop until the mid 20s," Georges Ghacibeh, M.D., a neurologist at Hackensack University Medical Center in New Jersey, told Fox News Digital. He was not involved in the study.
"During the early years, from conception until about age 5, the brain undergoes the most changes and therefore is more susceptible to the impact of external factors," added Ghacibeh.
In a previous study published in 2023, the same research team found that nitric oxide (NO), which is one of the particles in air pollution, is a "key pathological factor in autism," Amal noted.
Ghacibeh agreed that air pollution could increase autism risk.
"Chemicals inhaled by a pregnant mother or a young child, if they enter the bloodstream and make it to the brain of the fetus or developing child, can affect various metabolic pathways, either by interfering directly with certain chemical reactions inside the cells, or by reducing the amount of oxygen delivered to the brain," he told Fox News Digital.
This can interrupt the process of normal brain development, according to the doctor, causing brain cells to lose their normal function.
"The mechanism would be similar to the effect of certain medications ingested during pregnancy that can lead to developmental delay or autism in the child," Ghacibeh said.
Amal acknowledged that the study had some limitations.
"The data is based on epidemiological studies," he said. "Extensive experiments in our labs should be done to validate and prove this connection."
Ghacibeh agreed, noting that epidemiological studies prove association but not causality.
"In other words, if two phenomena occur simultaneously, such as high levels of air pollution and a rise in autism, this does not necessarily prove that one caused the other — it just means that both phenomena occurred at the same time. It is possible that additional, unknown factors might have played a role as well," he said.
Future research should aim to better understand pollution’s effects on "genetically susceptible individuals" and to find ways to protect those at greatest risk, according to Amal.
"This knowledge could inform public health policies aimed at minimizing ASD risk from environmental pollutants," he added.
In the U.S., autism affects one in 36 children, or about 2.3%, as of 2024, according to statistics from the Centers for Disease Control and Prevention (CDC).
This is an increase from one in 44 children two years ago.
Air pollution is also on the rise, affecting approximately 131.2 million people, or 39% of the U.S., as noted in the 2024 American Lung Association's State of the Air report.
This is an increase of 11.7 million people from 2023.
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Living in areas with lower pollution levels — away from factories or airports, for example — could help to prevent potentially harmful effects of air pollution, Ghacibeh said.
"Using good air filters, especially when you live in a higher-pollution environment, also helps mitigate those risks," he added.
Good nutrition and limited exposure to smoking, alcohol and drugs also helps to promote optimal brain development and neurological health, according to Ghacibeh.
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The study was funded by grants from the U.S. Department of Defense (DoD) and the Eagles Autism Foundation, which raises funds for innovative research and care programs, according to its website, along with others.
Fox News Digital reached out to the Autism Foundation, Autism Spectrum Disorder Foundation and Autism Society for comment on the study.
