Here are 4 recent studies showing a link from environmental factors including toxins to autism. Expect to see many, many more studies of this sort. Journal references are at the end of this posting.
1. Twin studies show that autism can be traced to both genetic and to environmental causes. (Hallmeyer, J., Cleveland, S., Torres, A. Phillips, J., Cohen, B., Torigoe, T., Miller, J., Fedele, A., Collins, J., Smith, K., Lotspeich, L., Croen, L., Ozonoff, S., Lajonchere, C., Grether, J., K., & Risch, N. (2011). Genetic heritability and shared environmental factors among twin pairs with autism. Arch Gen Psychiatry, published online July 4, 2011.)
2. Women who are genetically at risk for foliate deficiency have a reduced risk for bearing a child with autism if they take prenatal vitamins before and during pregnancy. (Schmidt, R. J., Hansen R. L., Hartiala J., Allayee H., Schmidt L. C., Tancredi D. J., Tassone F., Hertz-Picciotto I. (2011). Prenatal vitamins, one-carbon metabolism gene variants, and risk for autism. Epidemiology, 4,476-85.)
3. Women who take SSRIs before or during pregnancy (i.e. Proxac, Zolov, etc.) are at a 2% increased risk for bearing a child with autism. (Croen, L. A., Grether, J. K., Yoshida, C. K., Odouli, R. & Hendrick, V. (2011). Antidepressant use during pregnancy and childhood autism spectrum disorders. Arch Gen Psychiatry, 73, 1-9.)
4. I may have mentioned previously that toxins including heavy metals, PCBs and jet fuel products are showing up in bodies of pregnant women - who typically carefully watch their health. Those elements are most likely in all of us. (Woodruff TJ, Zota AR, & Schwartz JM. (2011). Environmental chemicals in pregnant women in the United States: NHANES 2003-2004. Environmental Health Perspectives, 6, 878-85.)