The Army says its Stryker armored vehicles have never fired depleted uranium rounds in Hawai'i, and there is no intent for them to ever do so.

That leaves Dr. Lorrin Pang unsatisfied.

"I guess the community is a little bit worried about (the Army's) credibility, so they would like to set up for monitoring," said Pang, the state Health Department's district officer for Maui County.

Pang, who also spent 24 years in the Army and was a preventive medicine officer at Tripler Army Medical Center in the late 1980s — and speaking as a private citizen and not in his official capacity — supported a bill that would have required regular soil testing at Schofield Barracks for the presence of depleted uranium.

The bill died in conference committee this past legislative session.

The revelation in January 2006 that the Army had found 15 tail assemblies from depleted uranium aiming rounds used in a 1960s weapon, coupled with the Stryker vehicle's ability to fire rounds with the weakly radioactive material, is spreading new concerns that the Army says are unfounded, and some community members say amount to a potential health risk.

Uranium is used primarily as fuel material in nuclear power plants. Most reactors require enriched uranium, which is extracted from naturally occurring uranium. The uranium remaining after removal of the enriched fraction is called depleted uranium, or DU, which has about 60 percent of the radioactivity of natural uranium.

DU is favored for armor-penetrating ordnance because of its high density, which is approximately twice that of lead. Depleted uranium is self-sharpening upon impact and knifes through armor, while tungsten penetrators tend to become blunt.

Increasingly, opponents of the Army's Stryker brigade are linking the 19-ton vehicles and depleted uranium ordnance.

A recent chairman's report from the Sierra Club's Moku Loa Group on the Big Island states, "Strykers fire weapons containing depleted uranium (DU), which is radioactive and potentially health-threatening."

The group also said the "Army asserted that no DU weapons were used at Schofield. Recently, this claim has been proved wrong." The Army found the 15 depleted uranium tail assemblies and recently confirmed to The Advertiser that it has found even more fragments at the same Schofield firing range.

This summer, the Army will conduct radiological testing at Schofield, Makua Military Reservation and Pohakuloa Training Area on the Big Island for more depleted uranium used in the 1960s with the Davy Crockett, a recoilless rifle that could fire a 76-pound nuclear bomb.

Only dummy warheads were fired here, and the depleted uranium came from smaller aiming rounds that were used to simulate the trajectory of the larger bomb. One Army veteran recalled firing inert warheads at Schofield Barracks and the Pohakuloa Training Area.

In e-mailed responses from the Pentagon, the Army said although the Stryker Mobile Gun System, a tanklike vehicle, can fire a 105 mm depleted uranium round, it does not intend to use or stockpile such munitions in Hawai'i. Stryker vehicles also can be fitted to fire a 25 mm gun using depleted uranium ammunition.

The Army said 27 of the expected 328 Stryker vehicles on O'ahu will be Mobile Gun System variants.

Army policy restricts the use of depleted uranium during training to ranges licensed by the Nuclear Regulatory Commission.

"The U.S. Army does not possess an NRC license to fire DU in Hawai'i, nor do we intend to apply for an NRC license for this purpose," the service said.

Although the steel armor of the M1A1 Abrams battle tank is reinforced by a sandwiched layer of depleted uranium, the Army said, "DU is not and will not be used in the Stryker armor."

The Army said an NRC license may be required to clean up ranges that were discovered to have the old aiming rounds from the 1960s, which represented one of the Army's first uses of depleted uranium.

"This determination will be made after the historical research and initial range surveys are completed this summer," it said.

Pang, Maui's district health officer, worries that despite what the Army said, it may still be using depleted uranium at Pohakuloa.

"Either that or they are stirring up a whole lot of dust (with depleted uranium) that's there," he said.

Pang said the real danger with depleted uranium comes with the vaporized or aerosolized form, which occurs on impact.

"Once it's vaporized and breathed in, the alpha particle emitters are the most dangerous form of radiation of all, because it's up in close and it sticks to the cells of your lung," he said.

The NRC regulates what it calls "source material," including depleted uranium, "to prevent misuse, to provide for the common defense and security, and to protect the health and safety of the public."

The World Health Organization said inhaled uranium particles may lead to irradiation damage of the lung. Measurements at sites where depleted uranium munitions were used indicate only localized contamination within a few yards of the impact site, the organization said.

The Defense Department, meanwhile, maintains that even when breathed or eaten, small amounts of depleted uranium carry no expected radiological health effects because the radioactivity is so low.

Doug Fox, who lives in South Kona, said he used a Geiger counter to test on April 21 downwind from Pohakuloa, 35 miles from the range, and got a radiation reading of 93 counts per minute. A typical radiation background reading is up to 20 counts per minute, he said.

"So this is an elevated reading," he said. He added that he believes Stryker training was being conducted at Pohakuloa at the time. The 3,900-soldier brigade is training for a deployment to Iraq this year and is finishing up rotations with the vehicles to the Big Island.

Readings taken elsewhere on the island were not elevated, Fox said.

But Russell Takata, program manager for the state Health Department's Noise, Radiation and Indoor Air Quality Branch, questioned Fox's use of a Geiger counter.

"I looked it up, and I basically (told him) for background type readings, you really need something that's a little more definitive at the low background levels (to gauge whether radiation levels are high)," Takata said. He added that the rule of thumb is that any readings three times normal background are suspect.

Takata said Fox also could have picked up readings for potassium 40, a naturally occurring radioactive material.

But to make sure, Takata said, he'll send someone from his office in the next week or two to take readings outside Pohakuloa with a gamma spectrometer and sodium iodide detector, "and it will tell me specifically what kind of isotopes are being kicked up."

He doesn't expect to find depleted uranium radiation.

"This is not something that's an imminent danger," he said, "(but) we'll go check it out."

Fox acknowledges he's not a professional in the field of radiation. "I'm just one citizen trying to find the answers to this because I'm living downwind from this thing," he said.

The fact that the Army plans Stryker anti-armor live-fire training "is kind of scary because the anti-armor projectile they use in Iraq is depleted uranium," Fox said.

He said he also believes the Geiger counters he's used are accurate.

"The real problem about this is you can talk about technical gizmos and stuff," he said, "but if the methodology is no good, it doesn't matter what gadget you've got. The only methodology that's going to work is continuous monitoring."

Reach William Cole at wcole@honoluluadvertiser.com.