No Significant Health Risks Expected from Plutonium Exposures

BOULDER, Colo. – According to new dose analyses and lifetime risk estimates received from radiation health physicians and experts, the small number of National Institute of Standards and Technology (NIST) personnel internally exposed to plutonium as a result of a June 9 incident are not expected to suffer any clinically significant impact to either their short- or long-term health. The experts calculated that the maximum increased lifetime risk of cancer as a result of the exposures was less than four-hundredths of one percent (0.04%).

"The estimated doses, and the increased overall risk for cancer based on these estimates, are so small we don't expect there to be any clinically significant impact on either the short- or long-term health of anyone exposed," said Edward Cetaruk of the University of Colorado Health Sciences Center, the doctor providing medical care to the affected individuals.

On June 27, NIST officials announced that a small number of individuals had received internal plutonium exposure as a result of the incident. Since that time, medical experts have conducted additional reviews and determined radiation dose levels to the affected personnel. Bioassay results and dose analyses from sensitive tests of plutonium exposure for 25 people were received and communicated to the affected individuals by July 9.

The Department of Commerce announced today that it will establish its own blue ribbon panel of independent experts to thoroughly examine NIST's environmental health and safety programs.

"We need a rigorous, above-the-fray review of this incident by nationally recognized experts," said Deputy Secretary of Commerce John Sullivan. "We will expedite efforts to get such a review under way to ensure that NIST has the best advice possible for identifying any improvements needed to strengthen its safety programs."

For the small number of laboratory personnel whose test results indicated internal plutonium exposure, none of the dose estimates received so far exceeded 400 millirem (4 milliSieverts, mSv) and most were below 100 millirem (1 mSv), according to radiation health physicist Richard Toohey of the Oak Ridge Associated Universities. For perspective, the average annual exposure of the general public to natural background radiation in the Boulder, Colo., area is about 450 millirem (4.5 mSv), based on estimates from the National Council on Radiation Protection and Measurements. Natural background radiation comes from cosmic rays, the ground (e.g., rocks) and the atmosphere (e.g., radon gas). The radiation dose for a typical chest X-ray is 10 millirem (0.1 mSv) and an abdominal CAT scan is 1,000 millirem (10 mSv), according to the Health Physics Society.

The increased overall risk probability for developing cancer from a radiation dose of 400 millirem (4 mSv), said Toohey, is 0.04 percent during an individual's lifetime. According to the National Cancer Institute, the average person born today has an aggregate lifetime risk of about 8 percent of contracting lung, liver or bone cancer, the principal potential health effects from plutonium exposure.

Additional, more sensitive tests are being conducted to confirm these initial dose estimates. Results are due to be delivered in up to four weeks. Estimating plutonium exposures is complex and dependent on many variables. Nevertheless, even if the total exposures are several times the dose estimates received so far, the affected personnel would not be expected to suffer significant health effects, according to the radiation health physicians and experts.

"I hope the affected individuals and their families are encouraged by these new results, but we have not lost sight of the fact that these radiation exposures should not have occurred in the first place," NIST Deputy Director James M. Turner said.

Also on July 9, NIST delivered to the Nuclear Regulatory Commission (NRC) a 30-day internal investigation report. The preliminary report cited a variety of factors, including inadequate training, failure to follow established proper procedures, and a lack of risk assessment and incident response planning, as contributing factors to the June 9 incident in which a vial containing about 1/4 gram of plutonium cracked, spilling the material. The report also describes NIST's best understanding of the chain of events leading to the spill, including factors and conditions contributing to the incident and a preliminary root cause analysis.

According to the report, current evidence suggests the spill was caused by breakage of the plutonium sample's glass container against a detector or nearby lead shielding material during an experiment. "An exacerbating factor and primary cause of the spread of contamination inside and outside the laboratory" was the fact that a researcher who handled the vial failed to "recognize and report the event in a timely, appropriate, and accurate manner and to limit his movements accordingly," the report states.

Contributing factors included a lack of radiation safety training or inadequate training for individuals who had access to the plutonium sample, improper removal of the glass vial from "secondary confinement" and inadequate hazards assessment. Preliminary root causes included inadequate radiation safety and emergency response training, inadequate supervision, access to the laboratory where the spill occurred by many individuals who were uninformed and untrained with respect to radiation, and lack of a specific emergency response plan for dealing with potential accidents involving the plutonium sample.

"I am deeply troubled by the facts described in this report. NIST is an agency devoted to meticulous detail and high standards. Clearly, we failed in many ways and I am committed to making sure that lax attitudes toward safety will not be tolerated. My goal is to have a strong and sustainable safety culture and I will do everything in my power to get us there," Turner said.

The investigation report was based on interviews with affected personnel, review of security camera recordings, computer data from detectors used in scientific experiments, and measurements of contamination patterns in the affected laboratories and other areas.

The report to the NRC is the first of several planned on the incident and NIST's response to it. An upcoming report by NIST's Ionizing Radiation Safety Committee will incorporate individual findings by five additional radiation physics and health experts.

Copies of these five reports will be provided to congressional oversight committees and posted on the NIST Web site.

In addition, NIST is cooperating with NRC, congressional and Department of Commerce Office of the Inspector General inquiries into the incident.

NIST already has taken a number of corrective actions, including developing an incident response plan, shifting supervision for NIST's Safety, Health, and Environment Division so that it reports directly to the NIST Deputy Director (who is currently carrying out the responsibilities of the Director) and requesting the assistance of the five experts to review the incident and NIST's current radiation safety and emergency response procedures and policies. 

NIST holds a license from the NRC authorizing it to possess and use radioactive materials. The June 9 spill occurred during the course of research to improve the sensitivity of detectors for nuclear inspectors. NIST-Boulder has currently suspended research using radioactive materials.

NIST will use the new dose analyses to report whether the internal doses received by a small number of individuals are within or exceed NRC regulatory limits. This determination is not expected until after the results of the more sensitive bioassay tests, using a method called thermal ionization mass spectrometry, are available.

Additional information on the NIST Boulder plutonium incident is available online.