After reading my post below, I thought I should clarify a couple of things. I realize that some who believe in a thimerosal-autism link probably don't argue for a specific brain lesion effect (which spent yesterday's post argues against.) Rather, the general effects of organomercury toxicity could be the cause. I don't think that this argument holds up - see this section of the Institute of Medicine report on thimerosal. Mercury causes a wide variety of neurological symptoms, and it generally causes them all at once.

Autism is probably too specific a condition to ascribe to a general organomercury effect. But, as I argued yesterday, it's still too general a condition to ascribe to some specific MPTP-like thimerosal toxicity. That doesn't close out the possible explanations; there's still room in there. But it does set bounds on them, and the size of the space that's left - coupled with the Rochester data that I mentioned previously - make it increasingly likely that this isn't the answer.