Expert Commentary

Radiation Fears and the Reality of Thyroid Cancers

Robert Yanagisawa, MD

Associate Professor of Endocrinology
Program Director, Fellowship Training Program in Endocrinology
Mount Sinai School of Medicine
New York, NY

 

The most significant impact on general health from the nuclear power plant accident in Fukushima following the tsunami of 11 March 2011 may be fear of radiation exposure and the stress of not knowing its effect. By providing more information about the effect of radiation on the thyroid, this fear can be appropriately reduced.

Two thyroid hormones, thyroxin (T4) and triiodothyronine (T3) are critical to infant development and control body metabolism in adults. In humans, the thyroid gland actively takes up iodide, oxidizes it, and couples it to other components to form thyroid hormone. Radioactive iodine (RAI) is also actively taken up. Children under 15 exposed to RAI are most at risk of developing thyroid nodules and cancers. Adults over 40 are generally not known to be affected.

During the 25 years since the Chernobyl accident, some 4000 cases of thyroid carcinoma and 15 deaths due to thyroid cancer are known from patients aged <19 at exposure. For Fukushima, thyroid cancer risk is expected to be significantly less. First, the amount of RAI released is ~10% of the Chernobyl accident. Second, the typical Japanese diet contains high iodine from seafood. In Chernobyl, patients were iodine deficient and thus predisposed to higher RAI uptake during exposure; similar to patients on 2 weeks of low iodide diet prior to RAI therapy to maximize uptake. Over 35,000 patients followed for 30 years after RAI therapy has not shown any significant increase in thyroid cancer.

In terms of internal exposure from contaminated food and water, to date, there has been no evidence for increased risk of thyroid carcinoma. Internal exposure is gradual and slow - reducing the risk of DNA damage. RAI emitted from the Hanford Nuclear site from 1944-1957 has not been tied to any significant increase in thyroid cancer incidence after 50 years.

To follow those exposed to a significant dose of RAI we recommend palpation of thyroid US and TFT. Any nodules greater than 1cm should have FNA for cytological confirmation if initial screening is benign, thyroid US every 3-5 years.

References

  1. Likhtarov I, et al (2011) Estimation of the thyroid doses for ukrainian children exposed in utero after the chernobyl accident. Health Phys. Jun;100(6):583-93.
  2. Hamada N and Ogino H. (2011) Food safety regulations: what we learned from the Fukushima nuclear accident. J Environ Radioact. Oct 11.
  3. Christodouleas JP et al (2011) Short-term and long-term health risks of nuclear-power-plant accidents. N Engl J Med. Jun 16; 364(24):2334-41
  4. McCurry J. (2011) Anxiety over radiation exposure remains high in Japan. Lancet. 2011 Sep 17;378 (9796):1061-2.
     
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