University of California San Francisco
Helen Diller Family Comprehensive Cancer Center

Chernobyl Studies Offer Perspective on Radiation Risks

By Jeffrey Norris, UCSF News Center | March 18, 2011

The ongoing radiation releases from the Fukushima Daiichi Nuclear Power Station 140 miles from Tokyo, with the possibility of much more to come, has invited comparisons to the Chernobyl nuclear disaster a quarter century ago.

However, the amount of radiation released in Japan thus far is very small in comparison, and officials and workers still hope to prevent more catastrophic damage. The spread of radioactive contaminants into the atmosphere from the Chernobyl accident was detected globally.

While the spread of radiation from Japan might also reach detectable levels in the United States, many state and federal officials quoted in the news media have indicated that they expect any amount of radiation that reaches the United States will be too low to result in increased health risks.

Nonetheless, there are many reports of customers cleaning out pharmacy shelves and internet suppliers in a rush to buy potassium iodide tablets.

The tablets offer some protection when taken immediately before or during an exposure to radioactive iodine by competing with radioactive iodine for a place in the thyroid gland. But there is no point in taking potassium iodide in the absence of an exposure, health officials say, and individuals who are allergic to iodine or shellfish may have adverse reactions.

“People should not be taking potassium iodide now,” says Stuart Heard, PharmD, executive director of the California Poison Control System and professor with the UCSF School of Pharmacy. “It can have side effects. It’s not appropriate for everybody. People should not take it unless they are properly advised.”

Most Iodine Contamination Was from Food
Studies of the health effects of the Chernobyl disaster in 1986 are still underway and may shed light on potential risks faced by workers and many Japanese in the region of the damaged nuclear reactors.

UCSF epidemiologist Lydia Zablotska, MD, PhD, has published several research studies on health impacts due to radiation released during the accident. Her recent, ongoing studies have focused on thyroid cancer among those exposed as children or adolescents in Ukraine and Belarus, and on leukemia and other blood disorders among clean-up workers.

The incidence of thyroid cancer due to release of the short-lived radioactive isotope iodine-131 rose as a result of the Chernobyl accident. Zablotska and her colleagues from the Radiation Epidemiology Branch of the National Cancer Institute have observed that most of the exposure to radioactive iodine was due to consumption of contaminated foodstuffs within a few months of the accident -- although there was some airborne exposure while nuclear fuel burned and smoked and was spread by winds.

“The portion of the dose that came from inhalation was minimal, and it really was limited to the first week after the accident,” Zablotska says. Most of the exposure was due to ingestion of milk, other dairy products and leafy vegetables contaminated with this radioisotope during the two months after the accident, she says.

Read more at Jeffrey Norris, UCSF News Center