There are 22 different cancers associated with radiation exposure, and the most common cancer associated with uranium mining and milling workers is lung cancer. This is most likely because radon and its decay products are primarily airborne and pose the greatest cancer risk of all the radionuclides emitted per the findings of an EPA study.¹⁶⁷ Other studies have indicated that long-term worker exposure to uranium mill tailings is weakly associated with elevated risks for birth defects, stillbirths, and other adverse outcomes of pregnancy; however, the authors stated “a lack of clear evidence for an increase in cancer risk to miners should be reassuring.”¹⁶⁸ A different study conducted in 2008 reviewing multiple papers on the health risks relating to the uranium industry found that the association of worker uranium exposure and cancer “is limited.”169 There are also several studies that have indicated no detectible increases in cancer to populations surrounding uranium mines or mills.^{170 171 172}

While the science could be viewed as inconclusive, mixed, and still evolving, prudence dictates caution. The absence of evidence—in this case an indisputable body of scientific work linking uranium industry to increased cancer rates in the nearby population—should not be construed as evidence of absence. The risk is unambiguously skewed to the downside. As time permits more long-term studies and medical technologies advance scientific understanding, there is an ever-present possibility that heretofore unknown linkages between the uranium industry and a specific illness will be uncovered. (Bold ours - RTR)

p. 85-86, Chmura report

Uranium mill tailings are the radioactive sandlike materials that remain after uranium is extracted by milling ore mined from the earth. Tailings are placed in huge mounds called tailings piles which are located close to the mills where the ore is processed.

The most important radioactive component of uranium mill tailings is radium, which decays to produce radon. Other potentially hazardous substances in the tailings are selenium, molybdenum, uranium, and thorium.

Uranium mill tailings can adversely affect public health. There are four principal ways (or exposure pathways) that the public can be exposed to the hazards from this waste. The first is the diffusion of radon gas directly into indoor air if tailings are misused as a construction material or for backfill around buildings. When people breathe air containing radon, it increases their risk of developing lung cancer. Second, radon gas can diffuse from the piles into the atmosphere where it can be inhaled and small particles can be blown from the piles where they can be inhaled or ingested. Third, many of the radioactive decay products in tailings produce gamma radiation, which poses a health hazard to people in the immediate vicinity of tailings. Finally, the dispersal of tailings by wind or water, or by leaching, can carry radioactive and other toxic materials to surface or ground water that may be used for drinking water.

The NRC and some individual states that have regulatory agreements with the NRC have licensed 26 sites for milling uranium ore. However, most of the mills at these sites are no longer processing ore. Another 24 sites have been abandoned and are currently the responsibility of DOE.

All the tailings piles except for one abandoned site located in Canonsburg, PA, are located in the West, predominantly in arid areas (Figure 6 [on page linked to below]). The licensed tailings piles contain a combined total of approximately 200 million metric tons (MT), with individual piles ranging from about 2 million MT to about 30 million MT. (A metric ton is 2,200 pounds.) The 24 abandoned sites contain a total of about 26 million MT and range in size from about 50 thousand MT to about 3 million MT. (Bold Ours - RTR)

http://www.epa.gov/rpdweb00/docs/radwaste/402-k-94-001-umt.html