There were never any studies done on its safety since 1929
. So the wording has always been something like 'there is no evidence that it is harmful'. Of course there isn't it hasn't been tested.
The main problem with thimerosal was that no-one considered the amount that babies were receiving. A little is probably fine, especially if you have a fully functioning detox system - which a lot of autistic children don't.
The FDA asked for it to be removed from childhood vaccinations in 1999, and the American Academy of Paediatrics called for the same in the same year.
The UK finally removed it in 2004 when I think WHO guidelines were changed to recommend it was removed. THis did follow work showing that thimerosal affected brain structure in mice.
There was some sort of overlap when the FSA were recommending that pregnant women shouldn't eat more than one portion of tuna a week (this was post 1999 as it was after my first pregnancy) but it was still deemed ok to inject mercury into 8, 12 and 16 week old babies.
Of course we didn't always inject 8, 12 and 16 week old babies with thimerosal- until the introduction of the MMR in 1989 the baby jabs were spread over the first year which gave longer between doses to get rid of the mercury.
If you want definitive proof that thimerosal is dangerous you won't find it as so little research has been carried out on it. However it is known that mercury is a neurotoxin. It also didn't need to be in the vaccinations. It could have been entirely avoided (as it is now) using single dose vaccinations. They cost a dollar more per dose.