Newswise — The peer-reviewed journal Environmental Health Perspectives (EHP) today published online a paper reporting that weapons-grade tungsten alloys, newly incorporated into the battlefield munitions of several countries, rapidly cause tumors, then lung cancer, when embedded in rats to emulate shrapnel wounds.
Concern over the human and environmental health effects of other metals long used in weapons has led many countries to replace depleted uranium (in some armor-penetrating munitions) and lead (In small-caliber ammunition) with various alloys of tungsten. One motivation for such a replacement is widespread public concern about the health and environmental impact of continued use of metals such as uranium and lead, along with the belief that tungsten has only limited toxicity. "However, to our knowledge, none of these militarily relevant tungsten alloys have been tested for potential health effects, particularly as embedded shrapnel," the study authors write.
Rats were implanted with a low dose (4 pellets) or a high dose (20 pellets) of tungsten alloy. Other rats received 20 pellets of nickel, a known carcinogen, or tantalum, an inert control metal. In findings that surprised the researchers, 100% of the rats implanted with tungsten-alloy pellets developed extremely aggressive tumors surrounding the pellets, although tumor growth was slower in rats implanted with lower doses. The tumors then rapidly metastasized to the lungs of the rats, necessitating euthanasia of the animals well before the anticipated end of the study.
"[The findings raise] extremely serious concerns over the potential health effects of tungsten alloy-based munitions currently being used as non-toxic alternatives to lead and depleted uranium," write the authors.
Tumors grew in the high-dose tungsten alloy implanted rats within 4 to 5 months of implantation. Changes in these rats' blood, including significant increases in red and white blood cells, were apparent as early as one month after implantation.
"While switching to tungsten was an effort to create a 'greener bullet,' these surprising findings demonstrate the complexity of understanding how metals combined into alloys might affect human health. If the findings of this paper are validated by further research, it appears that soldiers could be at risk of surviving battlefield wounds only to develop an aggressive form of cancer," said Dr. Jim Burkhart, science editor for EHP.
The lead author of the study was John F. Kalinich of the Heavy Metals Research Team of the Armed Forces Radiobiology Research Institute. Other authors include Christy A. Emond, Thomas K. Dalton, Steven R. Mog, Gary D. Coleman, Jessica E. Kordell, Alexandra C. Miller, and David E. McClain.
Funding sources for the research as reported by the authors include the United States Army Medical Research and Materiel Command. The paper will be published in the print edition of EHP this spring. This article is available online at http://ehp.niehs.nih.gov/docs/2005/7791/abstract.html.
EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org/.