There have been many theories and innumerable studies dealing with the role of environmental toxins in the development of autism. In fact, there is a school of thought that proposes that autistic individuals have a genetic susceptibility due to a sluggish detoxification system which renders them vulnerable to environmental injury.
The latest candidate is air pollution. A study from the Harvard School of Public Health showed that women exposed to high levels of fine particulate matter had twice the risk of having a child with autism. This was especially important during the last third of the pregnancy.
There have been previous studies showing the neurologic effect of air pollution. A series of studies on children and dogs in Mexico City (an area of very high air pollution) showed defects in cognitive function and executive function. MRI’s showed evidence of prefrontal and brainstem injury, and tissue studies showed not only inflammatory changes but even synuclein and beta-amyloid which are seen in neurodegenerative diseases such as Alzheimer’s and Parkinson’s. The presence of inflammation is important because it has been found routinely in brains of autistic individuals. One of the researchers from the autism study proposed that the immune response to air pollution is the likely mechanism of injury.
Obviously, the practical implications of the study require a public health response. There is only so much an individual can do, but it would seem wise to avoid highly polluted urban or industrial areas during the third trimester of pregnancy.