SIERRA VISTA — No toxic exposures have been detected to explain this city's alarming cluster of childhood leukemia, federal health officials announced today.
"We don't know why this cluster occurred. We really wish we had the answer, but we don't,” said Beverly Kingsley, an epidemiologist with the federal Centers for Disease Control and Prevention, which released the results of a three-year bio-sampling probe of both sick and healthy children and their families in Sierra Vista.
"We find nothing to indicate that any action needs to be taken in Sierra Vista," Kingsley said.
In fact, most of the 128 substances measured in the bodies of these children and their families "were low, and often lower, than levels usually detected in the U.S. population," a report on the probe stated.
However, the CDC did find a variation in a gene that controls how the body converts an unsafe chemical to a safe one in all of the leukemia-stricken children and almost half of the healthy children in the study. But investigators said they didn't know what effect this might have on the risk of leukemia.
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This booming military town 70 miles southeast of Tucson has been the focus of medical scrutiny for several years, after doctors at University Medical Center started treating an unusually high number of leukemia cases in children from this area.
Since 1997, at least 12 Sierra Vista children have developed this cancer of the blood and bone marrow system, and two have died of it. That is nearly triple the childhood leukemia rate expected in a town of 40,000 during that time period.
Both state and federal health officials at first resisted investigating the situation, saying cancer cluster probes rarely produce useful answers. But in 2004, the CDC finally decided to draw and analyze biosamples of blood, urine and cheek swabs from the surviving leukemia victims and their families, test them for 128 contaminants and possible carcinogens, and compare them to samples healthy Sierra Vista children. The samples also underwent genetic testing.
Environmental toxins long have been suspected as a cause of trigger for leukemia, although only one — the solvent benzene — has ever been proved to cause it.
After several delays, the bio-sampling got under way in May of last year. Samples were collected from five families of children with leukemia and nine comparison families with non-leukemic children, then sent to CDC labs for analysis.
The final results were disclosed today, first to the tested families, in private, individual meetings with CDC investigators and county health officials. That was to be followed by a two-hour public meeting held in Sierra Vista this evening.
Read more in Friday's Arizona Daily Star.
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