Elevated tungsten and cobalt in airborne particulates in Fallon, Nevada: Possible implications for the childhood leukemia cluster

Trace metal content was measured in airborne particulates in five towns located in west central Nevada with an emphasis on Fallon, where 16 cases of childhood leukemia were diagnosed recently. Airborne dust samples were collected using portable, high-volume particulate air samplers, and each filter was chemically analyzed by acid-dissolution, inductively coupled plasma mass spectroscopy. Tungsten was the most notable metal in Fallon dust, with cobalt of secondary but still important interest. Tungsten and cobalt were elevated in Fallon relative to comparison towns of west central Nevada, and within Fallon they co-varied closely temporally and spatially. These results were obtained and confirmed in two different collections during two different seasons of the year and using entirely different hardware and different types of filters. By weight of multiple lines of evidence, the source of tungsten and cobalt in airborne particulates in Fallon is probably not natural, but rather a hard-metal facility located in Fallon should tentatively be considered a candidate source of the airborne exposure of these metals within Fallon. Neither tungsten nor cobalt has yet to be definitively associated with childhood leukemia, but cobalt and tungsten carbide together are probably carcinogenic to humans. We concur with calls by others for more research in Fallon, and we recommend that cobalt be added into the toxicological studies, especially as an interactive factor with tungsten. (c) 2005 Elsevier Ltd. All rights reserved.