FALLON -- An investigation by the federal Agency for Toxic Substance and Disease Registry into possible contaminant "pathways" found no environmental link to a childhood leukemia cluster in this northern Nevada town.
The analysis of information collected by other agencies and area companies ruled out a jet fuel pipeline and the military base in Fallon as sources of the leukemia, scientists said Thursday.
The ATSDR reports echoed findings of another federal study released last week showing elevated levels of arsenic and tungsten in area biological samples and drinking water, but no indication they were related to the cancers.
"We just don't always have the answers," said lead scientist Gary Campbell. "We would like to have said this is the cause, but as in most cases with science, that's not easily done."
Scientists shared findings at a community meeting Wednesday evening. Residents expecting little new information trickled into the meeting in far fewer numbers than at a Centers for Disease Control and Prevention meeting last week.
Since 1997, the leukemia in Fallon -- a farming community of 8,300 and home of the "Top Gun" Navy fighter pilot training base -- has sickened 13 children and killed three others.
Arsenic occurs naturally in the Fallon area, about 60 miles southeast of Reno. Tungsten, used to strengthen steel, was mined for years, although the mines have been shut down. Neither contaminant has been linked to leukemia, though researchers have begun experiments based on Fallon findings.
The CDC announced in August that tungsten was found in unexpectedly high levels in eight out of 10 Fallon residents tested. Nationally, one in 10 Americans has comparatively high levels of the heavy metal.
The Atlanta-based ATSDR will assist CDC in an upcoming study comparing contaminant levels in Fallon with two other Nevada towns -- Lovelock and Pahrump.
Agency scientists used computer modeling and data from a dozen local and federal agencies to track the leukemia back to possible sources. Some information dated back to the 1970s.
The agency attempted to link an ever-shifting map of potential contaminants to areas where the sickened children lived or visited. Researchers reviewed weather data, wildlife studies, and dozens of government regulatory reports and records.
Like CDC and state investigators, ATSDR scientists warned Fallon residents against drinking tap water and well-water because of high levels of uranium and arsenic.
Based on concerns from residents, researchers pulled air pollutant permits for 37 nearby companies and visited three industrial plants including a tungsten smelting plant north of Fallon.
Campbell said he wouldn't rule out the Kennametal Inc. plant as a possible leukemia cause. However, he said air pollution records and site visits demonstrated no apparent health risks based on current scientific knowledge.
"We didn't see anything that would be alarming in terms of exposures to the community," Campbell said.
A University of Arizona scientist searching for links between Fallon and a smaller leukemia cluster in Sierra Vista, Ariz., said last week that his preliminary laboratory research indicates that tungsten alters the cell growth of acute lymphocytic leukemia or ALL, the disease type found in Fallon.
Dr. Mark Witten, a pediatric research professor at the University of Arizona at Tucson, said tree-ring samples taken near Fallon and Sierra Vista showed tungsten levels increasing in the past 15 years.
Federal and state scientists have cautioned that such research must be duplicated and further examined. The CDC previously asked the National Institutes of Health to begin researching possible links between tungsten and leukemia.
ALL -- the most common form of childhood cancer -- weakens blood and bone marrow, spongy tissue inside large bones. It initially causes children to tire and may make them bruise or bleed easily. It can be fatal, but most children who are diagnosed survive.
Nationally, there's an average of three cases per 100,000 people. Churchill County, where Fallon is located, has about 27,000 residents.
On the Net:
Agency for Toxic Substances and Disease Registry: www.atsdr.cdc.gov