Tungsten remains at center of cancer cluster probe
Terry on Mar 25th 2010
BY FRANK X. MULLEN JR. • Reno Gazette Journal
The metal tungsten remains an important clue in research related to the Fallon leukemia cluster, which sickened 17 children and killed three of them between 1997 and 2004, scientists said Thursday.
Presenters at the University of Nevada, Reno symposium described their research into cancer genetics, water contamination, electro-magnetic fields, mouse studies, and contaminants found in tree rings and on tree leaves. They are looking for possible environmental underpinnings of the cancer outbreak, whose odds of being random have been estimated at 1 in 232 million.
Researchers from the UNR; the University of Arizona and the University of California San Francisco presented final reports on three years work relating to the cluster. The research was funded by about $700,000 in federal grants obtained by Sen. Harry Reid, D-Nev., on behalf of the Fallon families affected by the outbreak.
The theory is that something in Fallon’s environment makes the area unique. For eight years, the metal tungsten, which is found in greater concentrations in the area’s water, air and people than in other parts of Nevada, has been an element of interest.
“We have been looking at linking environmental exposures unique to leukemia clusters to the development of leukemia,” said Cynthia D. Fastje, who exposed laboratory mice to tungsten and a virus at the University of Arizona.
Scientists have a two-hit theory of cancer cluster causes. The first “hit” is something from the environment that damages a child’s genes, perhaps while it is in the womb. The second “hit” could be an infection, a chemical or a virus that strikes the community but causes further damage to children’s genes already affected by the first hit.
In the experiments conducted by Fastje, Dr. Mark Witten and others, pregnant mice were given tungsten water at levels similar to those found in Fallon. The mouse pups were born and exposed to respiratory syncytial virus (RSV), which causes a common childhood illness.
Tungsten weakens immune response
Fastje said the tungsten appeared to weaken the animals’ immune response to the virus. About half the mice had enlarged spleens and 25 percent developed tumors in their jaws and necks. Some mice had symptoms consistent with leukemia.
She said more research into the effects of tungsten exposure is needed and noted that it’s a big leap between mice and humans.
Dr. Paul Sheppard of the University of Arizona said his research since 2002 has looked at tungsten and other metals as airborne contaminants in Fallon. His studies indicated spikes over time in the tungsten levels in tree rings and that tungsten found on tree leaves in 2008 was more concentrated on the trees closer to the center of Fallon, a finding consistent with previous studies of airborne metals.
Since the 1960s, the Fallon area has been home to a tungsten refinery and a tungsten plant in the center of town. That firm has consistently denied its operations can have anything to do with the cancer outbreak. It’s undetermined whether the tungsten found in the latest tree or leaf studies is the industrial or naturally-occurring form of the metal.
Dr. Joseph L. Wiemels, associate professor of cancer epidemiology, University of California, San Francisco, has looked at the genetic roots of cancer and studied leukemia cases in California and the Fallon cluster. He said because of Nevada privacy laws he was only able to look at the genetics of four of the 17 Fallon patients, but found nothing unusual in their DNA makeup.
Based on the disease registry information that has been made available, he said, “it appears to be clusters of other types of cancer in Churchill County at the time of the leukemia cluster.”
Overall, he said, children who have early exposure to viruses and thus develop immunities seem to be more protected against leukemia than those who have limited viral exposure, such as children without older siblings or those who don’t interact with other children at an early age.
A change in the environment
One question that scientists have been asking throughout their investigations: what sharply changed in Fallon’s environment in the mid-1990s that may account for the cancer outbreak between 1997 and 2004?
Dr. Chris Chris A. Pritsos, UNR professor of nutrition, and Dr, Ralph Seiler, a geologist, have been investigating Fallon’s groundwater. They looked at the concentrations of arsenic, tungsten, uranium and polonium-210 in the water and exposed lab mice to the Fallon water and water from other sources.
The studies indicated that exposure to groundwater high in tungsten, arsenic and polonium-210 induced “oxidative stress” in mice. Oxidative stress affects the body’s ability to repair itself at the cellular level and may be involved in the development of several diseases.
Although tungsten remains an element of interest, Sheppard cautioned that “we can’t link environmental findings to leukemia itself based on environmental data alone.” He noted that Nevada health authorities and the federal government have no interest in further probes of the Fallon cluster.
Future investigations are up to scientists outside the government labs, he said.
“We’ll keep on trying,” Sheppard said. “It’s important to carry on environmental monitoring in Fallon and I intend to do that.”
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