04/07/2011 - 06:45

Is the United States prepared for a nuclear reactor accident?

Laura H. Kahn

Laura H. Kahn

A general internist who began her career in health care as a registered nurse, Kahn works on the research staff of Princeton University's ...

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As Japan struggles to contain the crisis at its Fukushima Daiichi nuclear complex, government officials in other nations are nervously assessing their own emergency-response policies and procedures for a nuclear reactor accident. If any country is prepared to handle the worst that nature can present, it's Japan, where strict building codes and evacuation drills saved many lives from the March 11 disaster. But even Japan was not ready for a colossal 9.0 earthquake followed by a devastating tsunami.

Although a catastrophic failure of emergency backup systems at a US nuclear reactor may be unlikely, we need to be assured by our government officials that they have in place policies and procedures for dealing with nuclear worst-case scenarios.

Now the Japanese are struggling to contain the release of radioactive materials from the stricken Fukushima reactors. As of March 30, elevated levels of radioactive cesium 137 had been detected in 12 of Japan's 47 prefectures, and radioactive iodine 131 had been detected in eight prefectures. When these two isotopes escape during a nuclear reactor accident, they can pose major risks to human health.

Cesium 137 has a half-life of 30 years and emits penetrating gamma rays that, in massive doses, can cause radiation sickness. The first symptoms are nausea, vomiting, and diarrhea. A gamma-ray dose of 6 grays or more to the entire body causes death within two weeks; that dose is approximately 60,000 times greater than the exposure you receive from one chest X-ray. Depending on the dose and duration of exposure, gamma rays can also damage DNA and eventually lead to cancer. Geographic areas that are heavily contaminated with radioactive cesium require evacuation, but the evacuation need not be hasty. What matters is to avoid a large accumulated dose over many months or years, as the cesium slowly decays.

Iodine 131 has a half-life of only eight days and primarily affects the thyroid gland, a small organ that uses iodine to produce thyroid hormones. Radioactive iodine absorbed by this gland can increase the risk of thyroid cancer and other thyroid problems. Exposure to radioactive iodine can occur through inhaling it, drinking contaminated water, or consuming contaminated food -- particularly milk and other dairy products. Infants and young children are especially at risk from the harmful effects of radioactive iodine.

Fortunately, we have an effective strategy for avoiding the health effects of iodine 131: Taking potassium iodide pills saturates the thyroid with non-radioactive iodine and prevents the gland from absorbing radioactive iodine. To be most effective, potassium iodide should be taken before exposure to radioactive iodine, or at least within a few hours of exposure. Its protective effect lasts about 24 hours, so it must be administered daily as long as the risk of exposure persists. There are health risks associated with potassium iodide, so it should not be taken unless necessary.

In the US, the Nuclear Regulatory Commission emergency-preparedness regulations require that states consider providing potassium iodide to people living within a 10-mile emergency planning zone of a nuclear power plant, as a supplement to plans for sheltering and evacuating these people in the event of a nuclear power plant emergency. However, the final decision about providing potassium iodide is left up to each state.

The Public Health Security and Bioterrorism Preparedness and Response Act of 2002 requires that the president make potassium iodide tablets available to state and local governments in sufficient quantities to protect people living within 20 miles of a nuclear power plant. The act includes a waiver for the president to invoke if it is determined that there is an alternative to the mandate.

The National Academy of Sciences studied the impacts of expanded distribution, and concluded in 2004 that potassium iodide should be available to everyone at risk of significant health consequences, and that emergency response programs should consider pre-distribution and local stockpiling outside of the emergency planning zone. However, the study did not address the discrepancy between the 10-mile and 20-mile requirements, instead deferring to local emergency response officials to decide the geographic boundaries for distribution.

In January 2008, John M. Marburger, the director of President George W. Bush's Office of Science and Technology Policy, issued an executive decision invoking the presidential waiver: "A nuclear power plant accident that creates public health risks beyond the 10-mile range would be a highly unusual catastrophic event … Federal distribution of KI [potassium iodide] beyond the 10-mile emergency planning zone (EPZ) is not warranted, and the mandate for KI availability places an unnecessary burden on State and Local emergency preparedness coordinators already struggling with the establishment and maintenance of programs within the 10-mile EPZ."

Currently, 23 of 34 states with nuclear reactors provide potassium iodide tablets to people living within the 10-mile zone, and 16 states provide liquid pediatric potassium iodide. But in an accident like the Japanese crisis, 10 miles might not be far enough; depending on environmental conditions, radioactive materials can spread widely to soil, food, and drinking water. On March 17, the US embassy in Japan recommended that Americans stay at least 50 miles away from Fukushima Daiichi.

The Fukushima crisis highlights the challenges that government officials face. While rare, accidents do happen. The 1986 Chernobyl explosion resulted in the deaths of 30 plant workers, 6,000 cases of thyroid cancer in children, serious psychological and sociological consequences, and severe economic losses. Almost 58,000 square miles in Belarus, Russia, and Ukraine were contaminated by radioactive materials requiring hundreds of thousands of people to be evacuated. The Chernobyl Nuclear Power Plant Exclusion Zone established soon after the disaster -- in which the only human activities allowed are those associated with the cleanup, monitoring, and study of the accident -- extends 19 miles from the plant in all directions. While the Fukushima Daiichi nuclear power plant crisis does not appear to be as bad as Chernobyl, the full scope of the crisis will likely take years to assess.

Currently, there is no evidence that people living in the US need to take potassium iodide. Increases in radioactivity detected in the US have thus far been very small, and are not expected to cause any health effects. However, government officials are closely monitoring radiation levels.

There are 438 nuclear reactors worldwide, with 65 new plants being built. Most nuclear reactors are in North America, Western Europe, and Japan. The US has 104 reactors -- more than any other country. President Obama has made clean energy an important goal for his administration, and concern about fossil fuels and their contribution to global warming may lead to an increased reliance on nuclear energy. Although a catastrophic failure of emergency backup systems at a US nuclear reactor may be unlikely, we need to be assured by our government officials that they have in place policies and procedures for dealing with nuclear worst-case scenarios.