Historical Document
This document is provided by the National Center for Environmental Health ONLY as an historical reference for the public health community. It is no longer being maintained and the data it contains may no longer be current and/or accurate.
For current information about cancer clusters, please visit
http://www.cdc.gov/nceh/clusters/
What is known about tungsten?
See Frequently Asked Questions About Tungsten.
What was the purpose of the tungsten study?
The study was conducted to assess the level of exposure to tungsten in three Nevada communities to determine whether or not the levels of tungsten measured in Churchill County (Fallon), Nevada, were unique. CDC conducted the study as a recommended follow-up step to the Churchill County (Fallon) environmental exposure assessment.
CDC did not assess any potential health effects related to tungsten in this study. In August 2002, CDC nominated tungsten for study with high priority to the National Toxicology Program (NTP) [external link] of the National Institutes of Health. NTP is conducting the process of reviewing tungsten for its research agenda. For the latest progress on this issue, see The National Toxicology Program and Tungsten.
Who conducted the study?
CDC was the lead agency on the study, collecting samples, analyzing the urine samples, and preparing the report. The water samples were analyzed by the United States Geologic Survey [external link]. The soil and dust samples were analyzed by a laboratory that is certified by the U.S. Environmental Protection Agency [external link].
When did the study begin and end?
CDC began the study in mid-February 2003 and completed it in June 2003.
Why were the towns of Lovelock, Pahrump, and Yerington, Nevada, selected for the study?
The Nevada State Health Division [external link] selected the three communities on the basis of hydrogeology (the study of the interrelationships of geologic materials and processes with water, especially ground water).and history of tungsten mining. Lovelock and Yerington are hydrogeologically similar to Churchill County; Pahrump is not. Like Churchill County, Lovelock has a history of tungsten mining; Pahrump and Yerington do not. None of the three communities studied have a commercial tungsten facility.
Is there a greater than expected incidence of cancer in the three communities studied (i.e., a cancer cluster or unusually high rate of cancer, such as the high rate of childhood leukemia in Churchill County)?
According to the Nevada State Health Divisions [external link] analysis of Nevada cancer registry data, there is no evidence of an unusually high rate of cancer in any of these communities. For information about cancer rates in Nevada, contact the Nevada State Health Division through the following:
Nevada State Health Division
505 E. King Street, Room 201
Carson City, Nevada 89701
Tel: (775) 684-4200
Fax: (775) 684-4211
Web site:
http://health2k.state.nv.us/ [external link]
How was the study conducted?
CDC recruited 30 households from Yerington and Pahrump and 11 households from Lovelock. The eligibility criteria for household enrollment were residence in the city for at least one month prior to the interview, and presence of one adult and one child under 18 years of age who consented to participate in the study. We recruited a total of 141 participants. Each consenting study participant was asked to submit a spot urine sample for the analysis of tungsten metabolites, and to respond to a questionnaire detailing demographics and relevant exposures. CDC also collected a tap water sample, a floor-dust sample, and a yard soil sample from each household. These samples were analyzed for their tungsten content. In order to maximize comparability, the sampling protocol used was identical to that used in the Churchill County study.
What were the results of the study? And how do the results for these three communities relate to the levels of tungsten reported in the Fallon, Nevada, investigation?
All three study sites had geometric mean levels of urinary tungsten at or above the 95th percentile of the level established by the National Health and Nutrition Examination Survey (NHANES) reference population (0.48 micrograms per Liter [g/L]). A comparison of these levels between the study sites revealed that Pahrump and Lovelock had statistically identical levels, at 0.51g/L and 0.48g/L, while Yerington had levels significantly higher than both Lovelock and Pahrump (1.11g/L, p = .0001). Yeringtons overall urinary tungsten levels were similar to those found in Churchill County. Children had consistently higher urinary tungsten levels than adults across all study populations. Therefore, in general, exposure to tungsten in Churchill County does not appear to be unique when compared with other communities in Nevada. People living in communities having similar water sources and geologic formations to Churchill County may be expected to have tungsten exposures well above those reported as national reference levels from NHANES. For more information, see the full report [169 Kb] or one-page summary [154 Kb].
What do the tungsten levels mean to individuals?
CDC sent study participants their results along with the most complete information available on the relation between tungsten levels and health effects. At this time, there are no known adverse health effects of exposure to tungsten at the levels observed. In August 2002, CDC nominated tungsten for study with high priority to the National Toxicology Program (NTP) [external link] of the National Institutes of Health. NTP is conducting the process of reviewing tungsten for its research agenda. For the latest progress on this issue, see The National Toxicology Program and Tungsten.
Do these results disprove tungsten as a cause of the Fallon cancer cluster?
This study was designed to measure the level of exposure to tungsten in three Nevada communities. The results indicate that exposure to tungsten in Churchill County does not appear to be unique when compared with other communities in Nevada. The study was not designed to implicate or rule out tungsten as a cause of cancer. In August 2002, CDC nominated tungsten for study with high priority to the National Toxicology Program (NTP) [external link] of the National Institutes of Health. NTP is conducting the process of reviewing tungsten for its research agenda. For the latest progress on this issue, see The National Toxicology Program and Tungsten.
CDC also is conducting genetic testing to try to determine whether Fallon children or their families might either metabolize environmental contaminants differently or react differently in other ways to environmental contaminants. So far, CDC has done research to select the genes most likely to affect a persons susceptibility to leukemia. CDC is now extracting the DNA from each study participants blood and is developing methods to identify which of the gene variants each person has. CDC is also working on quality-control measures necessary to ensure that test results are accurate.
Will there be any follow-up to this latest tungsten study in the three communities (i.e., whats next for these communities)?
In August 2002, CDC nominated tungsten for study with high priority to the National Toxicology Program (NTP) [external link] of the National Institutes of Health. NTP is conducting the process of reviewing tungsten for its research agenda. For the latest progress on this issue, see The National Toxicology Program and Tungsten.
What is the status of the National Toxicology Programs study of the possible health effects of tungsten?
In August 2002, CDC nominated tungsten for study with high priority to the National Toxicology Program (NTP) [external link] of the National Institutes of Health. NTP is conducting the process of reviewing tungsten for its research agenda. For the latest progress on this issue, see The National Toxicology Program and Tungsten.
