Three weeks after the Japanese nuclear power plant disaster began, many U.S. residents are fearful about the possible health effects of radiation traveling across the Pacific. The Union of Concerned Scientists (UCS), an independent scientific research-based environmental advocacy group, has been monitoring the crisis closely. Below are some frequently asked questions from the UCS website regarding the health consequences of the Fukushima disaster, as well as information shared at news briefings by David Lochbaum and Edwin Lyman, nuclear safety experts with the UCS:
What are radioactive isotopes, and which ones are of most concern in a nuclear power accident?
UCS: Radioactive materials decay, releasing particles that can damage living tissue and lead to cancer. Some elements have different forms, called isotopes, which differ in the number of neutrons in the nucleus.
The radioactive isotopes of greatest concern in a nuclear power accident are iodine-131 and cesium-137. Iodine-131 has a half-life of eight days, meaning half of it will have decayed after eight days, and half of that in another eight days. It is also volatile, so it will spread easily.
In the human body, iodine is absorbed by the thyroid, and becomes concentrated there, where it can lead to thyroid cancer in later life. Children who are exposed to iodine-131 are more likely than adults to get cancer later in life.
To guard against the absorption of iodine-131, people can proactively take potassium iodide pills so the thyroid becomes saturated with non-radioactive iodine and unable to absorb any iodine-131. Cesium-137 has a half-life of about 30 years, so will take more than a century to decay by a significant amount. Living organisms treat cesium-137 as if it were potassium, and it becomes part of the fluid electrolytes, and is eventually excreted. It can cause many different types of cancer.
Is there a threat to Americans in Hawaii, Alaska, or the U.S. west coast? Should residents of these areas take potassium iodide pills to protect against thyroid cancer?
UCS: No. While wind patterns will likely carry the radioactive plume eastward, since Japan is thousands of miles from the United States, radioactive material in the air will be so diffuse by the time it reaches Hawaii, Alaska or the mainland United States that it is highly unlikely to create significant health concerns.
As a result, people in those locations will not have to worry about direct inhalation of a radiation plume, which is the kind of exposure potassium iodide (KI) pills are most effective against.
Americans could also be exposed to radioactive iodine if agricultural products became contaminated. Radioactive iodine could be ingested by dairy cows, for example, and then would be concentrated in milk. Potassium iodide, however, would not be effective in that situation. Moreover, federal and state health authorities should test for such contamination and could take products off the market if necessary.
Why is potassium iodide effective against inhalation of radioactive iodine, but not against ingestion via, for example, milk?
UCS: Potassium iodide can only reduce the risk from radioactive iodine that has entered the body, not eliminate it. People in the radioactive plume do not have the option of not breathing, so taking potassium iodide is an effective countermeasure against inhalation. However, people have the option of not drinking contaminated milk or eating other contaminated food products. In comparison, taking potassium iodide would be less effective.
Can you be exposed to dangerous levels of radiation flying across the United States due to the radiation released in Japan?
UCS: No. As noted in the previous question, since Japan is thousands of miles from the United States, radioactive material carried by the wind to Hawaii, Alaska, or the mainland United States will be so diffuse that it is highly unlikely to create significant health concerns. This is true whether you are on the ground or in an airplane.
Can nuclear plants in the United States withstand disasters such as the earthquake and tsunami that crippled nuclear reactors in Japan?
UCS: Some U.S. reactors are sister plants to the Fukushima Unit 1 reactor, which is a boiling water reactor (BWR) designed by General Electric, and they are operating under similar regulations. If confronted with a similar challenge, it's folly to assume the outcome would not also be similar. U.S. plants have the same key vulnerability that led to the crisis in Japan. The basic problem is that the Japanese reactors lost both their normal and back-up power supplies, which are used to cool fuel rods and the reactor core. The reactors had batteries that could supply power for eight hours until the back-up system or normal power supply was restored. But officials were unable to fully restore either.
Most U.S. reactors on the other hand, are designed to cope with station power outages (where both primary and back-up power supplies are out) lasting only four hours. Measures that increase the chance of restoring power within the four-hour time period, and provide better cooling options if that time runs out, would make U.S. reactors less vulnerable.
But dozens of nuclear reactors in the United States have operated for years in violation of fire protection regulations, knowing that earthquakes can cause fires at nuclear reactors. Studies have concluded that fire can be a dominant risk for reactor core damage by disabling primary and backup emergency systems. Yet those nuclear reactors have no plans to address these safety risks. Finally, reactor emergency plans in the United States assume that a reactor accident would be the only demand on emergency response resources. The accident in Japan is another reminder of the need to revisit emergency plans to ensure that emergency responders are able to respond to both the problem at the power plant and the nearby community’s needs.
Since 9/11, the U.S. nuclear industry has implemented additional power plant safeguards. Are we better equipped than the Japanese to cope with such a situation?
DR. DAVID LOCHBAUM: Well, I think with the situation they have, they have to grasp at straws to try to explain why what happened there can't happen here. They're basically similar reactor designs operating under similar regulations, so if our reactors were faced with a similar challenge, the outcome would be similar.
You know, there are certain things that were done since 9/11 that help, but I don't think that's a panacea that makes any of our reactors invulnerable to the type of problem that Japan faced.
DR. EDWIN LYMAN: First of all, the plans are secret. So, no member of the public actually knows what those plans involve. Second, what we do know is that because those were addressing what (the Nuclear Regulatory Commission) considers to be a beyond design-basis event, namely an aircraft attack on a currently operating plant, we do know that the equipment, any equipment that would be staged or designated for that post-accident management would not meet the highest nuclear safety standards that are required for protecting its design-basis events.
So, for instance, the Nuclear Energy Institute already admitted that that equipment is not safety related and would not be seismically qualified. So, if you have an event other than an aircraft crash, let's say a large earthquake, it's not clear that those plans and that equipment would actually survive to be available, putting U.S. reactors in the same spot that they were in in Japan.
Will washing Japanese produce make it safe? Can Japanese produce be decontaminated?
DR. LYMAN: With regard to iodine, that is a limited problem, and will be cleared in a few months. To the extent there's contamination with cesium, and other longer-lived isotopes, frankly, I don't think there are any good answers about how affected produce can be decontaminated. There are both national limits in Japan, international limits for destruction of contaminated produce, and I think those will have to be followed.
The problem is going to be when the contamination is within limits that the authorities say is safe. I think people need to understand more. I think I've said before, understand the potential doses associated with those levels and make their own decisions whether they should consume the produce or not.
But I would think whether or not it can be washed off, because I've been watching NHK and seeing what people are saying, I would be very wary of any unverified information about how to make produce safe at this point.
The FDA has banned the import of milk and fresh produce from the Fukushima region. Should the U.S. ban all Japanese food products?
DR. LYMAN: I haven't looked. Obviously it's not just the real risk, but it's also public perception and it's the same, you know, whether it's mad cow disease or melamine or lead, and unfortunately, one of the economic outcomes of this type of event …is the perception of contamination which can be as damaging as the actual, or more damaging than the actual, health risk, and that will have an economic impact whether or not there's actually a significant health risk.
So, unfortunately, it's going to take a long time for Japan to restore confidence in the safety of its exports.
Dr. Erin N. Marcus, is an associate professor of Clinical Medicine at the University of Miami Miller School of Medicine.