Researchers, writing in the journal Chemical Research in Toxicology, say tungsten alloys have been introduced as a "green" replacement for lead in bullets and other munitions out of concern that lead from spent ammunition could harm wildlife when it dissolves into water in the soil, streams and lakes, a release from the American Chemical Society said Wednesday.
Scientists had believed tungsten was relatively non-toxic but recent studies suggested otherwise, the researchers said.
Laboratory mice given drinking water containing small amounts of a tungsten compound were examined to see where in their bodies the tungsten ended up.
Researchers found the highest concentrations of tungsten were found in the spleen, one of the main components of the immune system, and in bone marrow, the initial source of all the cells of the immune system.
Further research, they say, will be necessary to measure what effects tungsten may have on functioning of the immune system.