UA scientists are seeking definitive links between recent unexplained leukemia clusters and surrounding environmental factors in an attempt to understand mysterious child cancer cases in Fallon, Nev., and Sierra Vista.

Since investigations began in 2002, scientists have discovered that between 1997 and 2004, at least 17 children fell victim to leukemia in Fallon, a town of only 8,000 residents, for a ratio more than 50 times higher than the national average, said Paul Sheppard, a UA tree ring specialist.

Scientists

from several medical institutions, including those at the UA, the University of Nevada, the University of California-San Francisco and the University of Nevada-Reno, are working in close collaboration to determine causes for the cases. Their research has been funded by federal grants obtained by U.S. Sen. Harry Reid (D-Nev.), the Environmental Protection Agency and the Gerber Foundation, said UA toxicologist Mark Witten.

Researchers are exhausting all means of establishing a definitive link, measures that include examining the air quality, climate, dust particles and, most notably, samples taken from local tree rings, Witten said.

The composition of materials within tree rings is a valuable tool, as it allows scientists to look back in history hundreds of years, he said.

“”We can tell if cancer clusters happened 125 years ago, something we can’t figure out just by talking to people,”” Witten said. “”People move, trees don’t.””

The most significant find within tree rings around the Fallon area has been the unusually high amount of the naturally occurring element tungsten.

Although the specific effects of tungsten on the human body are still being researched, the discovery is exactly the kind of link the team has been looking for, Witten said. Other environmental variables are being discussed, while some factors have been disproved.

Early in the research timeframe, some Fallon residents believed the military airport nearby had exposed their homes to dangerous jet fuel. After extensive testing on laboratory mice, it was found that jet fuel did not raise white blood cell counts, ruling out the ability of the jet fuel to cause leukemia within the community, Witten said.

A possibility still in the cancer discussion is the role of Fallon’s mines, which house large quantities of tungsten. In the past, mining was integral to the Fallon community.

While the investigation of Fallon has led to probable links between the environment and leukemia, less is known about the cancer clusters in and around Sierra Vista, where children are also coming down with leukemia.

The possibility of tungsten exposure in Sierra Vista still exists, although scientists continue to search for definitive links and will do so for several years to come, Sheppard said

Witten said the clusters are not a result of completely random environmental factors.

People over the past century have negatively affected land in the western United States, he said.

“”A hundred years ago, Arizona and Nevada were dumping grounds for toxic materials in the desert,”” Witten said. “”People in these states have the right to know if the ground they live on is safe.””

Tungsten exposure, cancer clusters and other afflictions are potential problems at several places nationally. Scientists on the Fallon and Sierra Vista cases also must research such locations as Kansas, Sacramento, Connecticut and southern New York, Witten said.

“”Tungsten is literally everywhere,”” he said.

Witten and Sheppard plan to continue research on how metals influence the development of cancer in the affected regions and what can be done to fight the process.

“”We are trying to answer questions about what causes cancer, how it manifests and how it progresses,”” Witten said. “”People have been trying to find out about clusters for years. These questions need to be answered.””