A mercury-containing preservative should not be banned as an ingredient in vaccines, U.S. pediatricians said [on December 17], in a move that may be controversial. In its statement, the American Academy of Pediatrics (AAP) endorsed calls from a World Health Organization (WHO) committee that the preservative, thimerosal, not be considered a hazardous source of mercury that could be banned by the United Nations. Back in 1999, a concern that kids receiving multiple shots containing thimerosal might get too much mercury - and develop autism or other neurodevelopmental problems as a result - led the AAP to call for its removal, despite the lack of hard evidence at the time. In a 2004 safety review ... the independent U.S. Institute of Medicine concluded there was no evidence thimerosal-containing vaccines could cause autism. A study from the Centers for Disease Control and Prevention came to the same conclusion in 2010. Thimerosal contains a type of mercury called ethyl mercury. Toxic effects have been tied to its cousin, methyl mercury, which stays in the body for much longer. Earlier this year, the WHO said replacing thimerosal with an alternative preservative could affect vaccine safety and might cause some vaccines to become unavailable. Mercury, however, is still on the list of global health hazards to be banned in a draft treaty from the United Nations Environment Program - which would mean a ban on thimerosal.