There is an ideological subculture that is motivated to blame all the perceived ills of the world on environmental factors and corporate/government malfeasance. Often this serves a deeper ideological drive, which can be anti-vaccine, extreme environmentalism, or anti-GMO. The latest environmental bogeyman making the rounds is glyphosate, which is being blamed for (you guessed it) autism.
Glyphosate is the active ingredient in the herbicide Roundup. It has been widely used for about 40 years, and with the introduction of GM crops that are Roundup resistant, its use has increased significantly in the last 20 years. It has therefore become a popular target for anti-GMO fearmongering.
Glyphosate is one of the least toxic herbicides used. It inhibits the enzyme 5-enolpyruvylshikimic acid-3-phosphate synthase which interferes with the shikimic pathway in plants, resulting in the accumulation of shikimic acid in plant tissues and ultimately plant death. The enzyme and pathway do not exist in animals, which is why toxicity is so low. Still, chemicals can have multiple effects and so toxicity needs to be directly measured and its epidemiology studied.
Experimental evidence has shown that neither glyphosate nor AMPA bioaccumulates in any animal tissue. No significant toxicity occurred in acute, subchronic, and chronic studies.
Therefore, it is concluded that the use of Roundup herbicide does not result in adverse effects on development, reproduction, or endocrine systems in humans and other mammals. For purposes of risk assessment, no-observed-adverse-effect levels (NOAELs) were identified for all subchronic, chronic, developmental, and reproduction studies with glyphosate, AMPA, and POEA.
As pesticides go, glyphosate has very low toxicity, and any dose a person is likely to get exposed to is well below the safety limits.