A national study by the Harvard School of Public Health confirmed a link between prenatal exposure to air pollution and a higher chance of having a child diagnosed with autism. Autism is a developmental disability characterized by difficulty initiating and sustaining social relationships, communication difficulties, and sensory-motor sensitivities.
Data from the Nurses’ Health Study II, a research project that followed 116,430 nurses from 1989 until present day was reviewed for the project. The study followed 325 women who had a child with autism and 22,000 women who had typically developing children, from different regions of the country. Data on air pollutants was retrieved from the U.S. Environmental Protection Agency from year to year, and cross-referenced with the rate of autism diagnoses in each given area. Results showed that women who lived in areas shown to have high concentrations of diesel and mercury in the air were twice as likely to give birth to a child diagnosed with autism as women from regions with cleaner air.
Two previous studies also showed a link between air pollution and autism diagnoses, but they only looked at data from three U.S. regions. The current study is the largest so far, and it’s results are consistent with past research.
Researchers caution that this study does not specify which environmental toxins may be causing the increased risk of autism. Several toxins, including diesel particulates, lead, manganese, methylene chloride, and other particles were present in the polluted air. Some researchers fear this may lead to a renewed panic over the use of a mercury-based preservative in certain vaccines that was once thought to cause autism and later disproved. The study also factored in other maternal risk factors, such as income level, education, and smoking. More studies are recommended to determine which toxins pose the greatest risk.
Researchers also suggest testing pregnant women regularly to determine the levels of mercury and other pollutants in the bloodstream. The results of these tests could confirm a definitive link between exposure to environmental toxins and the risk of an autism diagnosis, and could also lead to future research designed to isolate which toxins pose the largest threat.
Another study published in the Archives of General Psychiatry found a link between exposure to environmental toxins during the first year of life and increased risk of an autism diagnosis. This study compared 279 children with autism to 245 typically developing children, and found that those living in homes with the highest estimated levels of air pollution from traffic were three times more likely to be diagnosed with autism.
Autism is a complex, developmental disability that affects approximately 1 in 88 children, in the United States. Rates appear to be rising, and the scientific community has yet to pinpoint a reason for the increase. If there is indeed a causative link between environmental toxins and the risk of an autism diagnosis, further research may shed light on ways to protect pregnant women and their children from the risks.