Mention depleted uranium, or DU, and most people draw a blank. But the radioactive, man-made heavy metal is the focus of a growing controversy both here in Hawaii and elsewhere in the world.

Internationally, concerns have been raised about the long-term health and environmental effects of using DU to make bullets and shells more pervious and armored tanks impervious. Locally, similar fears have been expressed about the DU weapons present on at least two Army bases — Schofield Barracks on Oahu and Pohakuloa Training Area on Big Island.

The Army long denied that DU weapons had ever been used in Hawaii, but the advocacy law firm Earthjustice inadvertently came across e-mails to the contrary in 2006. The Army subsequently confirmed that contractors had discovered tail assemblies from the M101 spotting rounds while clearing a training range at Schofield in 2005. It acknowledged the DU rounds were used for training on the Davy Crockett — one of the smallest nuclear weapons ever built — in Hawaii and at least seven other states throughout the 1960s.

The Army is now asking the Nuclear Regulatory Commission for an after-the-fact license to possess a maximum of 17,600 pounds of DU at all of its American installations. The Army has no plans to remove or clean up the DU in Hawaii.

The NRC expects to issue a decision by the end of this year. If a license is granted, it likely will contain a number of conditions, with monitoring typically required “to ensure that depleted uranium and associated products are not being released offsite in quantities that would pose a potential threat to public health and safety or the environment,” according to an e-mail to Civil Beat from David McIntyre of the NRC Office of Public Affairs.

Meanwhile, Hawaii Island resident Isaac Harp has asked the NRC to take enforcement action against the Army for using DU in Hawaii without a permit in the 1960s. The NRC is reviewing that request and the director of its Petition Review Board expects to issue a proposed decision soon, according to a June 28 email to Harp from the NRC’s Ken Kalman.

It’s unclear how much DU is in Hawaii, or exactly where. It has been confirmed at PTA and Schofield, including an area above the aquifer there, but the Army acknowledges in its NRC application that rough terrain and hazards presented by unexploded ordnance made it impossible to conduct a thorough survey at the two installations. It is suspected on the Makua Military Reservation, and further surveys are planned there.

The NRC is assessing whether the Army’s request to possess nearly nine tons of DU accurately reflects the quantity present on its installations. The Army says the figure “includes a significant margin above what the Army’s records indicate was used,” McIntyre said in an e-mail to Civil Beat.

It is also unclear whether other DU munitions may be present in Hawaii as a result of training exercises. Under the Army’s application, its disclosure responsibilities would be limited to the Davy Crockett rounds. However, McIntyre said, “The NRC expects the Army’s application to cover all NRC-licensable material. If the Army discovers DU from other weapons, they would need to notify us and apply for a license amendment.”

Although the Army has steadfastly maintained that the DU on ranges in Hawaii poses “no imminent or immediate threat to human health,” some citizens are not convinced. They are particularly worried about aerosolized DU oxide, the tiny, airborne particles that are produced when DU is burned. Some of the M101 spotting rounds are located on live-fire training ranges.

As a result of those concerns, the Hawaii County Council passed a resolution in June 2008 urging the Army to halt all B-2 bombing missions, live firing exercises and other activities that create dust at Pohakuloa until the DU is assessed and cleaned up.

McIntyre wrote that the NRC also “has informed the Army that until such time as a license is issued for a particular facility and the attendant requirements are in place (i.e., the Army meets the conditions placed on the license), the Army should limit disturbance of and public access to its depleted uranium material.”

According to testimony given during three public meetings on the application held in Hawaii last August, citizens also cited fears about the possible contamination of drinking water sources and claimed the Army has failed to properly monitor radiation emissions. Many speakers also expressed distrust of the Army, while others objected to storing radioactive waste in Hawaii, particularly on the so-called “ceded lands.”