Do environmental factors such as toxins contribute to autism? On Respectful Insolence, Orac looks at a new study which found a correlation between birth defects and the eventual development of autism. Orac says this correlation has already been demonstrated, along with "autism and exposure to teratogens, specifically at least maternal rubella infection, thalidomide, valproic acid, and misoprostol." But could other chemicals be influencing higher rates of birth defects and autism in certain areas? Many people believe that autism-inducing toxins are found in vaccines. But autism's correlation with birth defects and its tendency to cluster in certain geographic areas suggest that the risk of autism could be determined before birth and/or by exposure to regional chemical concentrations, not to a nation-wide standard of care. Besides, no credible research has ever shown a link between vaccines and autism. And the risks of not vaccinating can be dire: on Aetiology, Tara C. Smith writes "infectious diseases still injure and kill, despite our nutritional status, despite appropriate vitamin D levels, despite sanitation improvements, despite breastfeeding, despite handwashing, despite everything we do to keep our kids healthy." With scientific understanding offering so much opportunity to raise a healthy child, why do some parents still draw the line at vaccines?