Digging deeper

Monica Yellowhair, PhD
Monica Yellowhair, PhD

Uranium exposure has led to some devastating public health consequences, including potential increased risk for certain forms of cancer. It’s an issue that truly hits home for Monica Yellowhair, PhD.

Dr. Yellowhair, a postdoctoral research associate with the University of Arizona Cancer Center, grew up in Kayenta, Ariz., on the Navajo Nation. That area near the Four Corners was home to some of the richest uranium mines in North America. According to the Environmental Protection Agency, nearly four million tons of uranium ore was extracted from this area between 1944 and 1986.

This radioactive element was in high demand during the Cold War, as increased demand for atomic weapons led to unprecedented mining in the area. During this time, uranium became the driving force of the Navajo Nation’s economy, while also quietly becoming the area’s greatest health risk.

“When I go back home to meet with people and especially talk with the elders, I can sense that uranium exposure is still a really big issue,” Dr. Yellowhair said. “It’s something that deeply affected the community’s older generation, and it’s something that is still affecting younger community members, whether they know it or not.”

All the uranium mines are now closed, but that does not mean that the problem has been solved. More than 500 abandoned uranium mines are scattered throughout Navajo Nation, with depleted uranium having potentially resulted in increased levels of radiation and uranium found in local drinking water and livestock sources.

Dr. Yellowhair began investigating this issue as an undergraduate student at Northern Arizona University (NAU) in 1998. She earned a Master’s degree in chemistry in 2005 and searched for opportunities that would allow her to delve deeper into the links between uranium exposure and a cell’s ability to repair its own DNA. As luck would have it, the UA Cancer Center and NAU had just established The Partnership for Native American Cancer Prevention (NACP) to help alleviate the unequal burden of cancer among Native Americans of the Southwest through research, training and outreach programs.

Dr. Yellowhair was among the first students to get involved with the NACP in its early stages, which allowed her to develop working relationships with some of the UACC’s top faculty, including Clark Lantz, PhD; Patricia Thompson, PhD; Jesse Martinez, PhD, and UACC Director David Alberts, MD.

Dr. Yellowhair enrolled in the PhD program at the University of Arizona in 2005 and is currently in the second year of her postdoctoral research program. She’s seen her research on this topic published in more than a half-dozen publications and has established herself as an authority on the subject as the issue has gained momentum over the last decade.

“We already know that uranium exposure has serious radiological consequences and increases one’s likelihood of suffering from leukemia or lung cancer, but what I’m primarily trying to figure out is if prolonged exposure to depleted uranium has a chemical consequence, which is an area we don’t know as much about yet,” Dr. Yellowhair said. “If the impact is, in fact, chemical, uranium exposure could also lead to increased risk of bone, kidney, stomach, pancreatic, colon and prostate cancers.”

In May 2013, Dr. Yellowhair explored the impact of copper and gold mining in small Mexican villages to serve as a comparative study to what she has been researching in Arizona. Her study’s hypothesis is that populations with higher uranium exposure will have an increased uranium concentration compared to the low-exposed group. As a result, populations with higher uranium exposure will have an abnormal DNA repair response when compared to a lower exposed population.

Her study’s target population is women in good health, ages 18 or over who are non-smokers and have experienced limited exposure to hazardous agents. She will be comparing the data between residents of San Antonio de la Huerta, near the Luz del Cobre mine to those who live in Ciudad Obregon, Mexico (the control population).

“We’re studying women primarily because this has been an under-studied demographic on this issue,” Dr. Yellowhair said. “Not only that, but there is an older study that shows potential childbirth complications, as well as another paper that indicates that uranium may mimic estrogen, which, if true, could open the door to all sorts of unforeseen issues.”

This isn’t just an issue that affects Navajo Nation or small Mexican mining villages, either. Uranium particles have occasionally been found in the Colorado River, and soldiers serving in Iraq and Afghanistan have encountered serious uranium exposure, as well.

When it comes to the field of depleted uranium exposure and its impact on cancer, we are just scratching the surface. Researchers such as Dr. Yellowhair will continue digging deeper.

-Nick Prevenas, June 24, 2013