Radiation disaster response plans needed

Health systems in close proximity to nuclear facilities and organizations involved with public health emergencies should develop and regularly practice response plans for radiation disasters, experts warn.

“A critical component of the response, with respect to both treatment of individual patients and interaction with the community, is clear communication about exposure levels and corresponding risk,” John P. Christodouleas, MD, MPH, and colleagues from the departments of radiation oncology and radiation safety at the University of Pennsylvania in Philadelphia wrote in New England Journal of Medicine.

Emphasizing the importance of addressing public fears about radiation sickness and cancer, Christodouleas and colleagues analyzed the short- and long-term risks of radiation exposure in the medical literature, including reports from the 1979 accident at Three Mile Island in Pennsylvania and the 1986 Chernobyl disaster in the Ukraine.

They categorized three kinds of radiation exposure that can occur as a result of nuclear reactor accidents: total or partial body exposure among plant workers and cleaning crews in close proximity, external contamination from escaped radioactive particles and internal contamination by ingesting exposed food both of which are likely to occur among the general population.

Workers are most likely to have the greatest radiation exposure, previous reports indicate – for example, clean-up workers at Chernobyl were exposed to more than 100 mSV of radiation compared to residents that were exposed to more than 50 mSV in highly contaminated areas.

In the United States the upper limit for occupational radiation exposure is 50 mSV.

Although food contamination can be widespread after a nuclear accident, with radiation rates thousands of times higher than normal, the health risks are still minimal, the researchers noted, and depend on the halve-lives of the radioisotopes released.

“The type of radiation and the dose rates that are invoved in a reactor accident would typically be very different from those seen in the detonation of a nuclear bomb, which is why the biologic consequences of these events may differ substantially,” the researchers wrote.

Iodine-131 is of particular concern, because it is typically prevalent in reactor discharges, can accumulate in the thyroid gland and is known to cause cancer. However, its half-life is short and local resources, such as produce and groundwater may only be contaminated for about two to three months.

Risk for thyroid cancer from iodine-131 is highest for children, with reports from Chernobyl indicating that children exposed to 1 Gy of radiation in endemic iodine deficient regions at a two- to three-fold higher risk for developing the cancer. The researchers noted that while the relative increase in cancer incidence due to radiation exposure  is large, baseline incidence levels are low in the population, at fewer than one case per 100,000 children.

Treating radiation exposure

Acute radiation sickness, which has not before been seen in the general population after a nuclear accident, occurs when a person is exposed to a single dose of more than 1 Gy of radiation. At Chernobyl radiation sickness only occurred in plant workers and members of the emergency response team.

The first steps in caring for anyone exposed to radiation involves treating immediate life-threatening injuries, like trauma or burns, and follow decontamination protocols, according to the researchers. After this “treatment is guided by the estimated total [radiation] dose, which is determine on the basis of initial clinical symptoms, lymphocyte depletion kinetics, and cytogenic analyses.”

Patients exposed to a whole-body dose of radiation less than 2 Gy may only needed to be treated for nausea and vomiting, whereas those who received a dose greater than 2 Gy may require treatment for bone marrow depletion. This can involve antibiotics, antivirals and antifungals for infections, hematopoietic growth factors and bone marrow transplant.

“The use of bone marrow transplantation is controversial, since outcomes after radiation accidents have been poor,” the researchers wrote, noting that 11 of the 13 patients who received transplants after Chernobyl died, two in which transplant complications was the primary cause of death.

Probiotics for gastrointestinal complications and topical corticosteroids for skin inflammation may also be necessary, according to the researchers.

Reducing contamination and minimizing exposure to radiation by staying indoors and avoiding locally grown produce and groundwater are the only options available to manage the long-term cancer risks, with the exception of potassium iodide supplements – which can help reduce iodine-131 build-up in the thyroid.

Despite concerns about potential toxic effects from potassium iodide, more than 10 million children in Poland were given a single prophylactic dose of the supplement with few adverse events. Among children exposed to radiation after Chernobyl, those who received iodine had one third the risk for thyroid cancer than those who did not.

FDA guidelines are available to clinicians looking for potassium iodide dosing information, which is determined by age and expected radiation exposure.

References

Christodouleas JP. N Engl J Med. 2011;DOI:10.1056/NEJMra1103676.

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