Louise Canfield, director of the Native American Cancer Research Partnership at the University of Arizona, says: "My personal opinion is that obesity and other lifestyle factors are key risks (for breast cancer), along with access to care. Uranium in drinking water is a health hazard for sure, but I'm not sure it's a primary cause of cancer."
But others consider the work groundbreaking. "This is a science of subtlety," explains Andrea Gore, a neuroendocrinologist at the University of Texas, Austin, and former advisor to the National Science Foundation. "(Dyer's and Raymond-Whish's) work is consistent with other good labs. People criticize the field of endocrine disruption because we don't always understand the mechanisms, but the effects are still real. This is why animal studies are so important. The responses we see in lab animals can happen in humans, because we share the exact same hormones. The estrogen receptor is similar."
Still, more evidence is needed before scientists concede a link between uranium and breast cancer in humans. "You can make a very strong case with animal studies, but it will never be definitive," says cancer expert Joaquin Espinosa, professor of molecular, cellular and developmental biology at the University of Colorado, Boulder. "You hope that nature would have done the experiment for you out there at some point. You need to show that real people are affected."
But epidemiological data on the reservation is hard to come by. For one thing, it's difficult to sort out reliable cancer statistics and their changes over time. Some Navajo elders consult only medicine men, so some cancers go unreported. Cancer itself is translated in Navajo as Lood doo nadziihii, "the sore that does not heal." Some patients do not seek treatment, nor do they even speak of the disease for fear of wishing it upon their families, according to Fran Robinson, a nurse oncologist at San Juan Regional Medical Center in Farmington. Until recently, the Indian Health Services kept haphazard records in which diagnoses went unconfirmed and doctors came and went. For a variety of reasons, including instances of abuse of trust by researchers, the Navajo Nation guards its own data as closely as any member of the former Soviet bloc.
The New Mexico State Tumor Registry keeps statistics on cancers by county, including those on the New Mexico portion of the reservation, which is also where many uranium mines were located. In her published paper, Raymond-Whish cites registry data from the late 1970s showing a 17-fold increase in childhood reproductive cancers there compared to the U.S. as a whole. These are extremely rare cancers that are related to hormone systems. Another study looking at registry data from 1970-1982 showed a 2.5-fold increase in these cancers among all Native Americans in New Mexico. (Although these statistics are not broken down by tribe, most of the Native Americans in the state are Navajo.) A 1981 paper showed a possible link between incidents of birth defects in families and the proximity of those families to uranium mine tailings. The sample sizes of the first two studies were too small to draw solid conclusions, and the birth defects study was flawed, cautions Charles Wiggins, director of the Tumor Registry. He plans to re-examine childhood cancer statistics this fall, using new data gathered since 1982.
Overall, Native Americans in New Mexico actually suffer less cancer than the rest of the country, including about half the rate of breast cancer. But even as breast cancer rates in the U.S. have leveled or dropped slightly in recent years, they continue to grow among Native Americans, and the rate has increased more steeply over the past three decades. Breast cancer is the number-two killer (after heart disease) of Navajo women and the most common cancer found in Navajos. (In the U.S. as a whole, lung cancer is the most common cancer.) Navajos with cancer also suffer higher mortality rates due to poor access to medical care. One study found that between one-third and one-fifth of Navajo breast cancer patients receive substandard care. Relatively more young Navajo women get breast cancer, although much of this can be explained by demographics: Navajos have a younger population than other groups. To the doctors working on the reservation, the anecdotal evidence is disturbing. "When we see women in their 30s with breast cancer, it really knocks everyone for a loop," says physician Tom Drouhard, who has been practicing in Tuba City, Ariz., for 30 years. "Our ladies come in with later stages and higher death rates. It's hard to say what the trends are. All of these tumors are multi-factorial, and uranium could be another thing thrown at it. We are very paranoid about the situation with uranium. We had uncovered tailings five miles from Tuba City for 20 years. It's a reasonable concern."
Two other hormonally active cancers, uterine and ovarian cancers, have doubled or tripled in New Mexico Indians since 1970 while remaining essentially the same for Anglos and Hispanics. But although lung cancer in the Navajo population has been authoritatively linked to uranium exposure, it's harder to make the case for other cancers.
"It's a tough nut to crack," says Wiggins. "The rise in breast cancer everywhere almost certainly has to do with hormones more than anything else. Is something going on with hormones and hormone receptors? Our data is not going to make or break any one hypothesis, because there are a zillion factors going up or down. But you have to take seriously any proposition anyone comes out with, because we just don't have answers yet."
It's difficult to trace a disease to an environmental exposure that may have occurred years earlier. And so far, cancer cases have not been mapped in concert with drinking water sources. "Is there more breast and reproductive cancer here?" asks Dyer. "Yes, but you can't localize it geographically. It would be nice to establish a connection between where people are getting sick and where they drink their water. It's hard to get the data. It's frustrating."
One major effort is currently under way to do just that, but the sickness in question is kidney disease, not cancer. This five-year, $2.5 million study, a collaboration between the University of New Mexico Community Environmental Health Program, the Eastern Navajo Health Board and the Dine Network for Environmental Health, is being funded by U.S. Health and Human Services. The team is compiling illness data from 1,300 Navajos, backed up by urine and blood samples, and then overlaying the results on a map of 160 drinking wells that have been studied for uranium, arsenic and other contaminants. Preliminary data from 550 residents and 100 wells have already shown that living within .8 kilometer of an abandoned mine is a significant predictor of kidney disease and diabetes. Although the science linking uranium with kidney disease is solid, it's never before been demonstrated on a real-life map showing proximity to mines, says Chris Shuey, an environmental scientist at the Southwest Research and Information Center. Once the kidney data are in, the researchers might look at cancer next, he says.
Of course, Navajos are not the only population exposed to uranium. What about breast cancer rates in other areas with better data?
Susan Pinney is an epidemiologist at the University of Cincinnati. She and her colleagues looked at the population surrounding a nuclear processing facility in Fernald, Ohio, which operated between 1952 and 1989. The facility, which made fuel rods for nuclear power plants, was the site of numerous accidental releases of uranium into the surrounding air and water. As a result of a $73 million class action lawsuit in 1990 against National Lead of Ohio and the U.S. Department of Energy, the Fernald Medical Monitoring Project has accumulated 17 years worth of data on illnesses and exposures. Pinney examined the medical records of 8,770 people, including nearly 5,000 women, for a variety of cancers, and was able to model the exposure level of each individual. Her work is still being prepared for publication, and she declined to discuss it. However, a presentation of her preliminary, statistically significant findings last November to the annual conference of the Breast Cancer and the Environment Research Centers is now available on-line. Its provocative conclusion: "For women living within five miles of a uranium processing plant, degree of exposure to uranium particulates was related to risk of incident breast cancer."