what is thimerosal found in
1 Thimerosal contains ethyl mercury. 2  This is a different chemical compound than mercury found in the environment (methylmercury). 3  Thimerosal has been used as a preservative since the 1930s to prevent bacterial growth in vials containing multiple doses of vaccine and other medical products.he majority of influenza vaccines distributed in the United States contain thimerosal as a preservative. However, an increasing amount is thimerosal-free. While the multiple dose vials still have thimerosal to prevent bacterial growth, the single-dose preparations do not.