By David Douglas NEW YORK (Reuters Health) - Shrapnel wounds caused by weapons grade tungsten alloy triggers aggressive tumors in rats, according to military researchers.
"As per regulatory guidelines," Dr. John F. Kalinich told Reuters Health, "an additional study using a second rodent species is required before this tungsten alloy could be labeled as a 'suspected human carcinogen'."
Until that study is done, he added, "it would be premature to speculate on any medical implications of this work. However, this study does point out the need for thorough testing of these unique compounds before their use."
In Environmental Health Perspectives, Dr. Kalinich of the Armed Forces Radiobiology Research Institute in Bethesda, Maryland, and colleagues note that tungsten in combination with various metals produces alloys with characteristics of interest to the military.
Part of this interest, say the researchers, springs from a desire to avoid the known environmental and other consequences of using munitions based on depleted uranium and lead. However, little is known of the potential health effects of embedded tungsten alloy shrapnel.
To investigate, the researchers implanted rats with tungsten alloy pellets -- either a low dose (4 pellets) or a high dose (20 pellets). Other animals were implanted with 20 pellets of nickel, a known carcinogen, or tantalum, an inert metal, which was used as the comparison group.
Within 4 to 5 months, all rats in the high-dose alloy group developed extremely aggressive rhabdomyosarcomas surrounding the pellets. All of the lower-dose alloy animals also developed these tumors, but at a slower rate. Tumor formation was also observed in the nickel-implanted rats.
Tumors in the alloy-implanted rats rapidly spread to the lungs and necessitated euthanasia of the animals before the intended end of the experiments.
Based on these findings, the researchers call for "further studies investigating the health effects of tungsten and tungsten-based alloys."
SOURCE: Environmental Heath Perspectives, February 2005.
