Noun
thimerosal (uncountable)
US standard form of thiomersal.
Thimerosal is a controversial mercury based (sic) vaccine preservative that research scientists and vaccine safety advocates have connected to the epidemic of brain disorders in children. Robert Francis Kennedy, Jr.
Due to the controversy surrounding thimerosal it has been removed from most vaccines except multi-use influenza, where it was reduced to levels so that a single dose contained less than 1 microgram of mercury, a level similar to eating 10g of canned tuna. Source: Internet
Until recent years, the preservative thimerosal was used in many vaccines that did not contain live virus. Source: Internet