High levels of tungsten apparent in Fallon trees

RENO -- Elevated levels of tungsten began showing up in trees in Fallon several years before an unusually large number of the town's children developed leukemia, but more research is needed to determine whether there's a link between the metal and the cancer cluster, researchers said.

The amount of tungsten in tree rings from the agricultural community quadrupled from 1990 to 2002, while the level in three nearby towns remained the same, said Dr. Paul Sheppard, an associate professor of dendrochronology at the University of Arizona, who specializes in the science of dating events and variations in the environment by studying rings in trees.

Previous research by Sheppard found elevated levels of tungsten and cobalt in airborne and surface dust in Fallon.

Sheppard's findings are the latest to suggest toxins and genetics play a role in the cancer cluster plaguing the town 60 miles east of Reno.

Since 1997, 17 children with ties to Fallon have been diagnosed with acute lymphocytic leukemia. Three have died. Health officials say about one childhood leukemia case in five years would be expected.

"The research suggests interesting patterns of tungsten with this incredible cluster," Sheppard said. "There needs to be more research done to examine the relationship between this metal and the development of leukemia."

Tungsten is a naturally occurring heavy metal that is mined and used in hardened tools and tools exposed to high temperatures, such as drill bits and the filaments of incandescent light bulbs. It has not been shown to cause leukemia, but research suggests it can damage DNA in cells in combination with other metals.

The tree-ring study by Sheppard, Dr. Mark Witten of the University of Arizona, Dr. Gary Ridenour of Fallon and Robert Speakman of the Smithsonian Institution in Suitland, Md., was published in the May issue of the journal Environmental Health Perspectives.

At least one parent of a child in the cancer cluster was encouraged by the findings.

"I'm always excited to hear about advances like this," Brenda Gross said. "I'm optimistic the cause eventually will be found as long as there's continuous research. These studies get us closer to the truth."

Martha Framsted, spokeswoman for the Nevada Health Division, said the agency would not comment until it had a chance to review the findings.

"We're not a research unit, but we certainly do encourage further research be undertaken, whether from universities, cancer institutes or others," she said.

Charles Green, a spokesman for the Centers for Disease Control and Prevention in Atlanta, said his agency usually does not comment on outside studies, but agreed that more research is needed to determine whether there's a link between tungsten and the cluster.

"It's definitely a very interesting ecological association," Green said. "I know we've met with him (Sheppard) several times and listened to him talk about his studies. We think any kind of science can lead to advances."

In November, the CDC released a study that found children in the cluster are more likely to have a variation in a gene that helps combat unsafe chemicals.

An earlier study headed by the CDC failed to find an environmental cause for the cluster. It found Fallon-area residents had higher levels of tungsten and arsenic in their blood and urine, but there was no evidence the substances caused leukemia.

Sheppard said tungsten levels in Fallon trees began significantly increasing in 1994, while levels in nearby towns remained the same.

He said he's unsure about the cause of the high tungsten levels. Sheppard does not think the tungsten found in trees there is naturally occurring.