The connection between air pollution and the autism spectrum: a new study conducted by Israeli and American researchers indicates the possibility of an increased risk of autism following exposure to air pollution. The study published in the new issue of the journal “Brain Medicine” and conducted by researchers from the Hebrew University of Jerusalem and the Children’s Hospital in Boston, identifies air pollution as an emerging environmental risk factor that affects brain development, especially during pregnancy and the first years of life.
In the study, the scientists describe the effect of various air pollutants, including fine particles (PM2.5), nitrogen oxides (NO and NO2), sulfur dioxide (SO2) and ozone (O3) on the human body. According to them, exposure to these pollutants may cause disruptions in essential neurological processes such as the migration of nerve cells, the creation of connections between nerves (synapses) and the construction of the “myelin” sheath for the nerve fibers. According to the researchers, exposure during pregnancy and early childhood constitutes a particularly sensitive period in which air pollution may lead to significant changes in the structure and function of the brain.
The study was based on a combination of data from different countries, including the United States, Israel and Taiwan. The researchers used diverse methods, such as collecting data on exposure to environmental pollutants among pregnant women and young children, and comparing the diagnosis rates of autism in different regions. In addition, the researchers performed laboratory experiments to examine how pollutants affect brain cells and the development of embryos, and identified possible mechanisms such as inflammation of the nervous system and disruptions in the functioning of the conducting substances in the brain. These methods helped deepen the understanding of the possible effect of air pollution on brain development.
According to the article, tiny PM2.5 particles are able to penetrate tissues and cross the placenta, increasing the risk of autism spectrum disorders – ASD – in fetuses. In addition, nitrogen oxides, which originate mainly from vehicle emissions, affect molecular pathways in the brain that are related to social and cognitive development. Another study cited highlights the link between exposure to ozone and particulate pollution during pregnancy and the first two years of life and the risk of developing ASD.
The findings also point to possible physiological mechanisms leading to a link between air pollution and ASD. Among these mechanisms are neurological inflammation, oxidative stress and so-called “epigenetic” changes that affect the expression of genes related to brain development. For example, oxidative stress caused by exposure to air pollutants may change the levels of the neurotransmitters glutamate and GABA, which are known to affect the balance of brain activity.
The researchers emphasize that while air pollution is considered an independent risk factor, its effect can be intensified among genetically susceptible individuals. They propose to investigate in the future the cumulative effect of various pollutants and their interactions with other genetic and environmental factors. In addition, future studies may focus on identifying biomarkers capable of predicting the risk of ASD in early stages, which will enable prevention and early intervention.
The researchers concluded that despite the scientific progress, there is a need for a policy that will reduce exposure to air pollutants, especially for pregnant women and babies, which may lead to a reduction in the risk of developing disorders on the autism spectrum.
The disorders of the communicative continuum are usually diagnosed near the age of two and are expressed in a series of deficiencies in social and emotional interaction. Those with the disorder avoid making eye contact, have difficulty understanding and responding to other emotions, have difficulty understanding insinuations or sarcastic comments, have a limited range of interests, prefer to be alone than to be in the company of people, feel comfortable dealing with objects, have attention deficit hyperactivity disorder and have difficulty adapting to changes. Children on the continuum also tend to suffer from difficulties regulating touch and noise and therefore some of them are helped by wearing headphones.