Temporal variability of tungsten and cobalt in Fallon, Nevada
| Autor: | Gary Ridenour, Robert J. Speakman, Paul R. Sheppard, Mark L. Witten |
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| Rok vydání: | 2006 |
| Předmět: |
Time Factors
Childhood leukemia Health Toxicology and Mutagenesis Childhood cancer Tungsten Correspondence medicine Cluster Analysis Humans Random event Child Leukemia Plant Stems Ecology Public Health Environmental and Occupational Health Population mixing Environmental availability Heavy metals Environmental exposure Cobalt Environmental Exposure medicine.disease Geography Populus Epidemiological Monitoring Environmental Pollutants Demography Pediatric population Environmental Monitoring Nevada Perspectives |
| Zdroj: | Environmental Health Perspectives |
| ISSN: | 0091-6765 |
| Popis: | We assessed recent temporal variability in environmental tungsten and cobalt in Fallon, Nevada (Figure 1A), where 16 cases of childhood leukemia were diagnosed from 1997 to 2002 (Expert Panel 2004) and an additional case was announced in December 2004 (Nevada State Health Division 2004). All cases but one were acute lymphocytic leukemia. As of the 2000 Census, Fallon has 7,536 residents (U.S. Census Bureau 2000), and its pediatric population up to 19 years of age is approximately 2,400 children. Counting all 17 cases in the time span of 8 years, the rate of childhood leukemia in Fallon is many times higher than the expected rate of 4.3 cases per 100,000 children (0–19 years of age) per year (National Cancer Institute 2007). This cluster has a very small likelihood of being a random event (Expert Panel 2004), and Fallon has been declared “one of the most unique clusters of childhood cancer ever reported” (Steinmaus et al. 2004). Figure 1 Maps of (A) west-central Nevada and (B) Fallon. In the detail of Fallon, filled circles indicate sampled trees. The hard-metal facility processes tungsten carbide and cobalt. Extensive research has been conducted in Fallon to determine if an environmental cause might be playing a role in its childhood leukemia [Agency for Toxic Substances and Disease Registry (ATSDR) 2002, 2003a, 2003b, 2003c; Centers for Disease Control and Prevention (CDC) 2003a, 2003b; Moore et al. 2002; Seiler 2004; Seiler et al. 2005]. A theory known as population mixing has also been proposed for Fallon (Kinlen 2004; Kinlen and Doll 2004). Among other environmental findings, a consensus has emerged that the heavy metal tungsten is elevated in Fallon (CDC 2003a; Sheppard et al. 2006a, 2007b, 2007c). Cobalt also is elevated in Fallon (ATSDR 2003a; Sheppard et al. 2006a, 2007b, 2007c). The temporal variability of tungsten and cobalt in Fallon over the last several years is not known because the environmental monitoring techniques used thus far cannot resolve changes through time. Dendrochemistry—the measurement and interpretation of element concentrations in tree rings (Amato 1988)—can document temporal variability of elements in the environment with up to annual resolution. Dendrochemistry has been used in studies of temporal patterns of various heavy metals in the environment, including lead (Hagemeyer and Weinand 1996), nickel (Yanosky and Vroblesky 1992), cadmium (Guyette et al. 1991), and mercury (Li et al. 1995). Dendrochemical measurements are typically used to evaluate relative changes through time in environmental availability of elements as well as to compare their absolute concentrations across different trees or different sites (Lewis 1995). Accordingly, dendro-chemistry was used in Fallon to assess temporal variability of tungsten and cobalt since the late 1980s—that is, since before the onset of the cluster of childhood leukemia. |
| Databáze: | OpenAIRE |
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