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What caused small town's leukemia?

Childhood cancer cluster, like the outbreak during the summer of 2000 in Fallon, Nev.  still remain a mystery to health experts.
Brenda Gross helps her son, Dustin, 8, with his homework at their Fallon, Nev., home in November. Dustin, who is now healthy, was among an unusually high number of Fallon children diagnosed with leukemia in the late 1990s.Cathleen Allison / AP
/ Source: The Associated Press

Maybe the first person to realize something terrible was happening to the children of Fallon was a nurse who gives chemotherapy at the community hospital.

It was the summer of 2000, and Dr. James Hockenberry had recently diagnosed two cases of childhood leukemia. As it happened, his son Timothy, also a family practitioner, had seen another.

These are the tragedies doctors encounter even in small towns, and neither man put them together.

Then one day Tim Hockenberry was working in the emergency room, and the infusion nurse, Barbara de Braga, stopped to see him.

“She came walking in and closed the door behind her,” Hockenberry says. “I thought, ’Oh, gee. Now what.’ She said, ’I’m concerned. I think we may have a cancer cluster going on.’ I remember the blood drained out of my face and just thinking, ’Oh, my God.”’

Hardly a coincidence
She counted them up: The Hockenberrys’ three cases plus one more, all in the past year. Soon calls were made. By the time state health officials got to the hospital, there was a fifth case. Then quickly a sixth. And a seventh. All in Fallon.

“People were starting to feel panicky, even the health care professionals,” remembers de Braga. “Everyone was looking at children and saying, ’Are they pale? Do they have bruises?”’ Possible signs of leukemia.

One thing seemed certain. This could hardly be a coincidence. Childhood leukemia is a rare disease. In a town the size of Fallon, just one case would be expected in five years. And during the 1990s, that is exactly what happened: one case in 1992 and one in 1999.

But that 1999 case — a 3-year-old boy named Dustin Gross with acute lymphocytic leukemia — was the start of an incredible spike. Through 2001, 11 cases were diagnosed in Fallon and surrounding Churchill County. Eventually, another five were found between 1997 and 2002 among children who once lived there but had moved away.

Little is known for certain about what causes this disease. Some think exposure to radiation in the womb or early childhood can contribute. But for most cases, there is no clear answer.
Without doubt genes are involved, as in all kinds of cancer.

Often young leukemia victims are born with genetic defects that put them at risk, but it probably takes several more to get cancer. Perhaps some environmental toxin causes these. Or maybe they accumulate through an unlucky series of random errors when cells copy their genetic material as they divide.

During the 1960s and ’70s, the Centers for Disease Control and Prevention investigated 108 cancer clusters around the United States, most of them childhood leukemia, in hope of proving that a virus, a chemical or some other contaminant caused the disease.

In the end, they found nothing. If the cases in any single place shared a source, it could not be detected with the tools medical investigators had at the time. Maybe they were just random flukes after all.

Were there common traits?
In the decades since then, the source of these cancer outbreaks remained as much a mystery as ever. In fact, not a single geographic cluster was ever solved to scientists’ satisfaction.

Still, the Fallon outbreak was especially sudden and large. State health officials decided an inquiry was essential, if only to make sure no awful contaminant was seeping unseen through the community.

The first step, decided that day when the state visited the hospital, was to interview all the victims’ families to see what they had in common.

And so began the most intensive investigation ever conducted into a cancer cluster. By the time it was over, hundreds of experts from at least seven state and federal agencies would be involved, spending millions, all to answer one question: What is causing Fallon’s leukemia?

Except for its sprinkling of small casinos and the legal brothel outside town, Fallon at first glance could be a modest farming community anywhere. Its 8,200 residents live on the high desert about an hour east of Reno. Along U.S. 50, the main drag, miles of emerald irrigated alfalfa fields dead-end in brown, rocky scrub that undulates to the horizon.

Were farm chemicals to blame for the cancer? The drinking water? Or could it somehow have come from the town’s real claim to fame, the Fallon Naval Air Station? All day, planes roar and bank overhead, reminder of the base’s busy fighter jet training program, including the Navy’s Top Gun school.

That summer and fall, a team led by Randall Todd, the state epidemiologist, put the young victims’ parents through sessions that lasted an average of three hours.

They asked where they lived when their child got sick, whether they drank tap water or bottled, the kind of chemicals they used, whether crop sprayers flew nearby, and so on, then the house they lived in before that, and before that, going back to two years before the child was conceived.

“Was there some common trait they all had?” Todd asked. “Had the majority of moms taken a particular medicine during pregnancy? X-rays? Chemicals in the household? We realized it was probably a long shot, but we needed to ask the questions to rule out a common denominator.”

But there was none, at least, none this first look could detect.

** ADVANCE FOR SUNDAY, DEC. 14 **This is a view of downtown Fallon, Nev., Nov. 20, 2003. Health officials in the town of 8,200 became concerned in the late 1990s when they observed a spike in the number of childhood leukemia cases. (AP Photo/Cathleen Allison)
** ADVANCE FOR SUNDAY, DEC. 14 **This is a view of downtown Fallon, Nev., Nov. 20, 2003. Health officials in the town of 8,200 became concerned in the late 1990s when they observed a spike in the number of childhood leukemia cases. (AP Photo/Cathleen Allison)Cathleen Allison / AP

The state pulled together a committee of outside experts to go over the facts and give advice. They recommended a methodical analysis of all the contaminants the cancer families could have been exposed to, along with a review the town’s hazardous sites. It suggested two federal agencies for the job, the U.S. Centers for Disease Control and Prevention and the Agency for Toxic Substances and Disease Registries.

For two decades, the CDC had largely avoided cluster investigations, considering them futile.

However, this seemed like an opportunity to get to the bottom of one at last. “I went into this with a fair amount of optimism that we might ultimately identify something responsible,” says committee member Les Robison, head of pediatric epidemiology at the University of Minnesota.

The CDC agreed to take on Fallon, in part, because of huge improvements in the ability to locate traces of toxins and microbes. With new technology, they can pinpoint one part per trillion in a sample of blood or urine, the equivalent of locating a grain of sand in a 3,000-square-foot house. But which should they look for?

“We had to ask, ’What’s unique about this community?”’ says Todd.

At least three things stand out: Its municipal water has among the country’s highest levels of naturally occurring arsenic, 10 times federal standards. A pipeline carries jet fuel across the desert to Fallon’s Navy base. And 40 years earlier, an underground nuclear test was done just 30 miles away.

Perhaps these things or something else in the drinking water was causing cancer. So while the federal investigators planned their studies, the state tested a dozen wells plus the town water.

There is no evidence that arsenic, dangerous as it is, causes childhood leukemia. The level of the town water — 100 parts per million — was well-known, but the amount in people’s wells was another matter. In some of the victims’ wells, the testing found off-the-charts amounts, eight times higher even than the town water.

No real clues
But nothing suggested it caused a sudden surge in cancer, since people in Fallon have been drinking arsenic in their water since the town was settled a century ago.

There was no trace of jet fuel in the water, either, and the only radioactive material was slight amounts of the natural kind, not bomb remnants.

With no real clues from the state’s examination, the CDC went to work drawing blood, collecting urine samples and scraping cells from inside people’s mouths. They dug soil from families’ yards, vacuumed dust in their bedrooms and captured air in their living rooms.

And of course, there were many more questions, too, about jobs, hobbies, pets, diet, school attendance, medicines, vaccinations, travel, smoking, weed killers, bathing habits, X-rays, infections, and much more. Did the child eat locally grown cantaloupe? Did the mother swim in the ocean while pregnant?

For each family with cancer, they randomly picked four more as comparisons. This is called a case-control study, used to look for differences between families that get sick or stay well. It is the standard way of isolating the causes of all sorts of illnesses.

From the start, though, the investigators prepared people for a less than definitive conclusion. “The CDC said, ’We’ll work really hard, but we may not find anything,”’ remembers Mayor Ken Tedford.

First among the suspects were the most biologically plausible cancer causes, such as benzene and similar solvents. But eventually they checked for a long list of volatile organic compounds, pesticides, metals, PCBs, radioactive material and viruses.

“As researchers, we invested an extraordinary amount of time and effort and planning and really wanted to find an explanation,” says Carol Rubin, who headed the CDC investigation.
Meanwhile, rumors and theories circulated through town. Some spoke of government conspiracies, of crucial information hidden. Others worried that the cancer was contagious.

At first, many blamed arsenic. Then jet fuel. State investigators even walked the pipeline, looking for withered plants, odors, anything to suggest a leak. Talk turned to a theory called population mixing, the idea that military people cycling through the base had brought in a germ of some sort. But in the end, none of these held up.

Eventually, all the testing revealed a surprise. Screening volunteers’ urine for 16 different metals, from antimony to uranium, they found incredibly high levels of tungsten. No one knew what to make of it. There was no reason to think tungsten causes cancer, although its health effects have not been studied much, either.

Intrigued, the CDC studied three other Nevada towns. All also turned out to have tungsten levels far above the national average. Tungsten, it seems, is just a natural part of the region’s geological environment.

In the end, the CDC tested for more than 100 different pesticides, metals and other contaminants in blood and urine, along with more than 100 in soil, 70 in house dust and 60 in air samples.

They showed the cancer families had virtually the same exposure to these things as did healthy neighbors. Review of the pipeline, the base, crop spraying and other possible sources showed nothing unusual, either.

All of this is in a four-inch stack of reports in Todd’s office in Carson City. The bottom line: Nobody knows what caused the leukemia.

For the people of Fallon, there is at least one consolation.

“We do know probably more about the environmental health of Fallon, Nev., than most communities elsewhere,” says Rubin. “Of all the many things we measured, levels of most were no different from elsewhere in the United States. That’s got to be good news for the community.”

So what caused it?
Because cancer has many possible origins, including random genetic mutations, there is simply no way to say what caused any individual’s disease. That’s why the researchers focused on the families” shared exposures. But perhaps they missed it. Maybe it was so elusive that even their one-in-a-trillion tests could not detect it.

Cancer typically takes years to develop, even for children, so if there was a common cause, it must have been at work in the late 1990s. By the time the investigators arrived in 2000, perhaps it had vanished.

Although toxins in the environment were the main target of the investigation, they are not typically a major cause of cancer. The American Cancer Society estimates that such exposures as air or water pollution probably account for only 1 percent to 2 percent of the disease.

And even if an environmental poison was to blame, everybody in Fallon may have received it to some degree, making it impossible to show this exposure was the culprit.

Theories about viruses are also kicked about. But in truth, there are no strong suspects, and some now wonder if the real answer may be one they rejected so certainly at the investigation’s start.

Could all of those cancer cases in one small place have been just an against-the-odds roll of the dice, like winning the lottery or being attacked by sharks?
Robison believe so. “My interpretation is what we are probably looking at is a random occurrence of chance,” he says.

That is the most likely reason behind most cancer clusters, says Dr. Michael Thun, the cancer society’s epidemiology chief. “Throw confetti out of an airplane, and some will fall in clusters. It’s a terribly unsatisfying explanation to anyone.”

Especially to people like Brenda Gross, mother of Dustin, the cluster’s first victim in Fallon. Dustin is now 8, a healthy looking boy whose disease is in remission, and she still very much wants to know the cause.

“I don’t want to sound unappreciative, but it seemed like they were going through the motions to pacify us,” she said of the investigations. “I am 100 percent sure there was an environmental cause, absolutely.”

The outbreak stopped as quickly as it began. No new cases have been seen in Fallon since 2001. Now, it seems, many in town are relieved to put it all behind them.

“The community is confident that those people came and looked,” says Tedford, the mayor. “They tried hard. They eliminated dozens and dozens of possible causes. Now they are ready for life to go on.”