According to whom?
Science has told us unequivocally that mercury is bad for our bodies. In sufficient doses, mercury kills cells that it contacts, causes neurological damage in humans and other animals, and generally wreaks havoc on living things. Yet since the 1930s, thimerosal has been used as a preservative in vaccines.2 One of the breakdown products of thimerosal is ethylmercury, which is an organic form of mercury. Public concern about thimerosal is certainly understandable, but does this mean that concern about the link between vaccines and autism is justified as well? In a word, no. Mercury might do a number of nasty things to the human body, and concern about it is therefore justified, but that does not mean it causes autism.
Ethylmercury is not the same thing as its cousin, methylmercury. Cumulative and high doses of methylmercury can produce renal and neurologic damage. It can build up in the brain and stay in the body for a long time. Ethylmercury is more, well, mercurial. It is expelled rapidly from the body and it does not accumulate. Nevertheless, guidelines for the ingestion of ethylmercury were based on those for methylmercury. Around the same time these guidelines were formalized, children were receiving more vaccines that contained thimerosal. For example, in the early 1990s the Haemophilus influenzae b and hepatitis B became staple features of the vaccine schedule for infants, which already included another thimerosal-containing vaccine (diphtheria tetanus and variants). Based on the very conservative guidelines established by the Environmental Protection Agency, it was concluded that by age two some children might be receiving excessive levels of ethylmercury when considered in the context of known risks of methylmercury exposure.3
From previous posts, I believe you are a physician.
Can you comment on the total elimination of all mercuric compounds in the US (perhaps worldwide?) since the 1990s? I know mercurochrome and yellow mercuric oxide preparations disappeared from pharmacies about that time. When I asked the pharmacist, I was told that 1) there are better antiseptics now and 2) formulations like opthalmic 1% yellow mercuric oxide (for styes) never worked, anyway. I mentioned this to a vet who said that he also no longer uses nor can obtain any mercuric formulations. No one mentioned dangers, just that the old mercury compounds had been superceded by better preparations.
Since I am fairly certain of the above facts, it seems strange that any mercury would still be used anywhere, even in low amounts as a perservative.