Concerns related to radiation exposure emerge in Japan

As Japan recovers from the devastating earthquake and subsequent tsunami that damaged several nuclear reactors, endocrinologists find themselves fielding questions from patients and the public about whether the fallout will affect the US population.

Leonard Wartofsky, MD, speaking on behalf of The Endocrine Society, elaborated on a few of the typical concerns about radiation exposure.

“The problems in endocrinology that we’re concerned about are primarily associated with the thyroid gland,” Wartofsky said. “With larger amounts of radiation, particularly radioactive iodine, there may be damage to the thyroid severe enough to cause hypothyroidism, and lower doses may cause mutations that lead to thyroid nodules and thyroid cancer.”

Radiation exposure may also raise the risk for parathyroid adenomas and hyperparathyroidism, he said. In addition, similar to adverse events observed in some patients with thyroid cancer who are treated with radioactive iodine, exposure may also cause damage to the salivary glands.

Reports from the Nuclear Regulatory Commission and Environmental Protection Agency purport that the thousands of miles separating Japan and the United States make the chances of radiation reaching US territories extremely low.

“We should provide Japan with any support we can, but otherwise, we seem to be fine here in the United States,” Wartofsky said.

A push for preparedness

According to estimates from the International Atomic Energy Agency, the Japanese government has distributed more than 200,000 stable iodine units to Fukushima evacuation centers since the tsunami hit the coast. In the United States, potassium iodide is selling quickly.

The American Thyroid Association released a statement that underscores the importance of distribution of potassium iodide in regions surrounding nuclear power plants. If taken soon after exposure to the radioactive iodine released during a nuclear emergency, potassium iodide can help dilute the amount of radioactive iodine in the blood so that uptake into the thyroid gland becomes minimal. Distribution of potassium iodide in the area around a nuclear reactor before an accident can ensure that it is available in a timely fashion, even in the setting of major disruptions to transportation and other infrastructure, as have occurred in Japan, according to the ATA.

“The risk to the thyroid from radioactive iodine can be ablated by taking in stable iodide,” Wartofsky said.

Although preventive measures, including regular safety surveillance of nuclear plants, are essential to thwarting these problems, disaster preparedness is the best solution to combat the consequences of such accidents. One of the most vital components of a preparedness plan is an early warning system.

However, using the accident at Chernobyl in 1986 as an example, Wartofsky said the earliest warning system to the population was not effective. “A lot of people were exposed to the radiation before any word got out,” he said.

Since 1984, the ATA has advocated that potassium iodide should be part of an emergency plan that includes evacuation, sheltering and avoidance of contaminated foods, milk and water. The association also recommends that potassium iodide should be made available to people who live within 200 miles of a nuclear power plant and should be predistributed to households within 50 miles of a plant. However, all usage and planned usage of potassium iodide in the event of a disaster should be used only under regulatory guidance.

“The ATA and The Endocrine Society pioneered for stockpiling of potassium iodide, but the EPA and other organizations in hearings held during the 1980s and 1990s declined to do so, I think largely on the basis of cost related to the logistics of stockpiling,” Wartofsky told Endocrine Today, a sister publication of HemOnc Today.

Nevertheless, several companies manufacture potassium iodide and many pharmacies stock the solution, so the product is already widely available.

The current disaster in Japan may serve as a wake-up call for the US government to re-examine this issue, Wartofsky said.

“Particularly, regional stockpiles around nuclear reactors with an emergency system for distribution that can kick in immediately would be very appropriate,” he said. “Letting this incident provoke a re-look at the safety of our US nuclear reactors would be the best outcome for this terrible accident.”

Previous fallout

Past events involving the negative effects of radiation exposure at Chernobyl, as well as US nuclear weapons testing on the Marshall Islands in the South Pacific in the 1940s and ’50s, have led to the heightened anxiety. One incident on the Marshall Islands led to exposures of approximately 50 to 600 rad to the thyroid, and many people who were exposed eventually developed thyroid nodules and thyroid cancers. The estimated radiation release at Chernobyl was smaller, creating exposures of about 25 to 250 rad to the thyroid. Wartofsky said these exposures equate to about a three- to fivefold increased risk for thyroid cancer. These numbers are increased considerably among young people, however.

“The risk [for thyroid cancer] is primarily increased in children [after radiation exposure],” he said. “Pregnant women and children aged younger than 5 years have maybe a 10- to 20-fold risk, but once you reach age 18 to 20, there’s virtually no longer any risk because the thyroid cells are not dividing and growing as frequently as in children.”

In addition, children have much smaller thyroid glands. Therefore, given the same absorbed radiation dose, the dose per gram or milligram of tissue is much higher than in adults, Wartofsky said, adding that the source of exposure in many of these incidents, such as Chernobyl, derived from milk from cows that had consumed grass contaminated from the fallout, which also drove up the risk for thyroid cancer and nodules in children.

In the current situation, however, officials have said there seems to be a low risk to the US population. Wartofsky said he encouraged the endocrine and other medical societies to create bulletins about radiation exposure available to the public to help ease anxiety.

For more information on potassium iodide and its distribution during emergencies, visit www.thyroid.org. – by Melissa Foster

Disclosure: Dr. Wartofsky reports no relevant financial disclosures.

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