A new study has unveiled significant findings that deepen the understanding of how environmental factors may influence early brain development.
The study suggests that air pollution inhaled by women during pregnancy could be associated with a higher risk of autism in their children.
Based on a review of the latest research on autism, the findings reveal that children with a genetic predisposition to autism who were exposed to four common air pollutants were more likely to develop the condition.
Researchers believe these pollutants, when inhaled during early childhood or while in the womb, can enter the bloodstream and reach the brain. Once there, they may bypass the brain’s protective barriers and cause inflammation, affecting nerve function and development.
Autism rates have seen a noticeable rise globally in recent decades. A recent analysis in the United States found that autism rates among children and young people have nearly doubled, with approximately 3 out of every 100 children now diagnosed with Autism Spectrum Disorder (ASD).
Dr. Haitham Amal, head of the Department of Neuroscience, Cellular Signaling, and Translational Medicine at the Hebrew University of Jerusalem, stated, “We are trying to understand what might be contributing to this increase in cases.” His lab has focused particularly on nitric oxide (NO), a gas released during fuel combustion in vehicles. He suggests that autism results from a complex interaction between genetic and environmental factors.
In a paper published in Brain Medicine, Dr. Amal’s team reviewed studies on children with autism, as well as research using human cells and animal models.
The team focused on four key components of air pollution: fine particulate matter (PM), nitrogen oxides, sulfur dioxide, and ozone.
- Fine Particulate Matter (PM): Produced by construction sites, power plants, and vehicles, these particles are 7 to 30 times smaller than a human hair.
- Sulfur Dioxide (SO₂): A colorless gas generated by burning fossil fuels or smelting metals.
- Ozone: A colorless, odorless gas produced by chemical plants and oil-based paints.
The findings indicated that individuals with a genetic predisposition to autism who were exposed to air pollution early in life had a higher risk of developing the condition compared to those exposed to lower pollution levels. This points to a gene-environment interaction that may increase autism risk.
While the study did not provide exact statistics, earlier research from Harvard University suggested that exposure to air pollution, such as fine particulate matter, during early childhood could increase autism risk by up to 64%. Prenatal exposure to such particles may increase the risk by 31%.
Although the exact causes of autism remain uncertain, it is believed that genetic factors account for 40-80% of cases. Individuals with a family history of autism may have a higher likelihood of developing the condition.
Dr. Amal’s team remains unsure of the precise mechanisms linking pollution to autism but has proposed several theories:
- Inflammation: Inhaled pollutants may cause inflammation in neural tissues, altering their development over time.
- Chemical Disruption: Pollutants like nitric oxide may cross the placenta and reach the fetus during early development, interfering with brain growth. Inhalation may also disrupt the production of key brain chemicals like dopamine and norepinephrine, essential for decision-making and overall brain development.
The researchers also suggest that the global rise in autism cases may partially result from increased awareness and improved diagnostic practices, leading to more identified cases.
