Thimerosol is a commonly-used preservative, used primarily in children's vaccinations. It contains 49.6% mercury. It has been in use since the 1930s. External links http://www.cliffroberts.com/Thimeresol/List%20of%20Vaccines%20Containing%20Thimerosal.htm http://www.testfoundation.org/thimerosal.htm This is very much a stub article