Local environmentalist Carroll Cox is raising concerns about the lack of public notification of what the Marine Corps revealed Thursday was a "low level" radiation release in the March crash of a CH-53D Sea Stallion helicopter on the Kaneohe Bay sandbar that killed a crewmember and injured three others.

The big chopper is equipped with an In-Flight Blade Inspection System on each of six rotor blades with 500 microcuries of strontium-90 in each of the devices. The IBIS system is used to provide in-flight warning of blade failure.

One of the IBIS capsules was compromised in the crash, and "a few" base personnel received minor contamination from a raft that was used to ferry equipment to and from the crash site, officials said. The contamination was rinsed off with water, officials said.

An ice detector on the single-rotor chopper also contains about 50 microcuries of strontium-90.

"The low levels of radiation previously detected pose no significant health or environmental risk and were not of a reportable quantity," Marine Corps Base Hawaii said in an email. "The site on the sandbar where the helicopter rested was inspected both during and after the salvage and recovery of the aircraft as a precautionary measure. No radiological contamination was found at the site."

Cox said the public should have been notified.

"Remember, this is not a military base, this (the sandbar) is a public place, this is public land, public water," he said. Cox added that "the public has a right to know, (when) there are little children running around. This is also a recreation area. It’s not an isolated area."

In a letter to Gary Gill, state Health Department deputy director for environmental health administration, Cox calls for an investigation "because during the time the Marines failed to report the (radiological) incident to your agency and the public, members of their teams were actively using Geiger counters to search for the IBIS components, and reportedly while screening people for contamination."

Janice Okubo, a Health Department spokeswoman, said Thursday the agency was still gathering information, and was waiting to hear from the Marine Corps base.

The state Department of Land and Natural Resources later said it would do its own testing on the sandbar today.

The Marine Corps said in its release that "during the recovery efforts, some aircraft components were found to have a low level of contamination. All materials found to be contaminated were decontaminated or appropriately contained here on base. All personnel involved in the handling of any contaminated material were screened to verify they were not contaminated."

Cox said he was told some Honolulu Fire Department personnel, who were among the responders to the crash, raised concern about the radiation. The Marines said no firefighters were contaminated and were told after the crash about the release. Fire spokesman Capt. Terry Seelig said the department is looking into the matter.

Marine officials said there was a report made to the state noting the release of about 600 gallons of JP-8 fuel and 100 gallons of hydraulic fluid and turbine oil, but the radiation release wasn’t included because it didn’t contaminate the environment.

Dean Higuchi, a spokesman for the U.S. Environmental Protection Agency in Honolulu, said the National Response Center is the main reporting agency, but a "reportable quantity" spill threshold for strontium-90 was not reached.

"If anybody was to spill (a hazardous material), be it strontium-90 or, let’s say, even ammonia, once the reportable quantity is exceeded, they would call the National Response Center and the National Response Center would then start the chain, OK, who’s going to go, what’s going to happen," Higuchi said.

Higuchi said the "reportable quantity" for a strontium-90 release is 0.1 curies, which is equal to 100,000 microcuries. The threshold compares with 500 microcuries in each IBIS capsule.

According to the EPA, strontium is a silvery metal that turns yellowish in air. Strontium-90 is a byproduct of the fission of uranium and plutonium in nuclear reactors and nuclear weapons.

Strontium-90 can be inhaled or ingested with food or water and is referred to as a "bone seeker" because it tends to deposit in bone and blood-forming tissue. Internal exposure is linked to bone cancer, cancer of the soft tissue and leukemia, the EPA said.

The Navy said in a 2003 document that the dose rate when the IBIS is shielded is 0.8 millirem per hour at 3 inches distance. When the strontium-90 source is unshielded, the dose rate is 150 millirems an hour at 8 inches and 7.5 millirem an hour at 3 feet.

The average person is exposed to about 620 millirems of radiation a year. According to the American Nuclear Society, a chest X-ray is 10 millirems and a six-hour flight in a jetliner results in an exposure of 3 millirems.

The strontium in an IBIS is normally shielded, but is exposed and detected by monitors if rotor-blade pressure falters. A Navy guide for working with the IBIS states that if the radioactive isotope is exposed, barrier tape should be put up 10 feet from the source; leather gloves and eye protection should be worn if attempting to put a cover on the device; and no more than one minute should be spent near the capsule.

The crash of a CH-53D Sea Stallion from Kaneohe Bay while on deployment to Okinawa, Japan, in 2004, also raised concern about IBIS radiation.

The U.S. Embassy in Japan said at the time that five of the six capsules were recovered and that evidence pointed to the sixth being burned and vaporized in the wreckage.

"This amount equates to an exposure much less than a normal chest X-ray or a flight across the Pacific," the embassy said at the time.

A little after 7 p.m. on March 29, a CH-53D crashed onto the Kaneohe sandbar from an altitude of about 300 feet just minutes after leaving base on a night-vision-goggle training run.

Cpl. Jonathan Faircloth, 22, an aerial gunner, was killed, and three other crew members were injured.

Hawaii News Now video: State to test for radiation at Kaneohe sandbar