As workers continue to attempt to contain damage of the four reactors in Japan’s Fukushima Dai-Ichi nuclear plant, residents of the country are becoming increasingly worried about the health risks associated with radiation fallout from the plant — not only in the coming weeks, but months or years into the future. Based on the aftermath of previous nuclear accidents, the consequences of the March 11 earthquake and ensuing tsunami may linger long after the debris has been cleaned up. Here’s what experts say the Japanese can expect.
What are the health problems associated with radiation exposure?
Depending on length of exposure and how much radiation is involved, the effect can be acute in the form of radiation poisoning, or more long term in the form of increased risk of cancers.
The workers at the plant who are trying to cool overheated fuel rods and and prevent a meltdown are likely to experience the highest levels of exposure in the shortest period of time. They are at highest risk for radiation sickness, or acute radiation syndrome, which can damage tissues, cause the bone marrow to stop generating new blood and immune cells, and lead to periods of severe illness or eventually death. People exposed to high levels of radiation are also at greatest risk of infection, so they need to be kept in isolation wards in sterile environments to protect them from bacteria and viruses.
To reduce their risk, regulatory agencies set limits for the amount of time nuclear-plant workers can be exposed to situations that carry a risk of excessive radiation exposure. These limits are generally calculated in the form of cumulative yearly exposure, so once workers reach that amount, they cannot be re-exposed to radiation for another year. In the U.S., the Nuclear Regulatory Commission restricts workers to 50 millisieverts of radiation exposure per year. At the Fukushima plant’s No. 2 reactor, radiation levels had hovered at about 73 microsieverts (0.073 millisieverts), before a blast sent the amount soaring to 11,900 microsieverts (11.9 millisieverts) three hours later.
Longer term health consequences of exposure include cancer, particularly thyroid cancer, since the gland is especially sensitive to the effects of radiation. Again, the risk varies depending on distance, dose and duration of exposure.
People in and immediately around the crippled reactors are likely to have higher long-term cancer risks than others. For the majority of Japanese, however, that additional risk is likely to be relatively small, according to Dr. David Brenner, director of the center for radiological research at Columbia University. “The exposures [most] people are getting — as opposed to those right outside the plant — is still pretty low,” he says. “It’s important to stress that the risk of cancer under normal circumstances is already big anyway, and what we’re talking about here is a pretty small increase over and above that very big cancer risk. We’re not talking about a doubling of risk or anything like that.”
The difference between the ongoing Fukushima incident and the explosion of the Chernobyl nuclear facility in Ukraine in 1986 is that the latter released a more dangerous cloud of radioactive material — which eventually drifted as far as Western Europe — and which some studies suggest could have contributed to as many as 2000 additional cancers, and possibly more, in the ensuing years.
There may yet be more radioactive material released from the Fukushima plant, but so far the material that has been released appears to have mostly dissipated into the atmosphere, Dr. Kirby Kemper, nuclear physicist and physics professor at Florida State University, tells CNN.
People near the plant are being told to stay indoors. Can that really reduce radiation exposure?
Yes. Staying indoors and sealing your house is a way to prevent ingesting or carrying around any radioactive material that may have attached to dust or other airborne particles and to keep it from landing on skin, clothing or hair. How long people should stay indoors depends on the half-life of the radioactive material (how long it takes radioactivity to dissipate by half): the health danger could be largely reduced in as soon as a week in the case of radioactive iodine, or many years in the case of cesium.
Will the food supply be contaminated?
According to Japanese officials, the explosions in the four reactors have released radioactive iodine 131 and cesium 137. Because iodine has a half-life of just over a week, any grasses, crops or animals exposed to it should be cleared of any residual material in a matter of weeks. If no more radioactive material is released into the air, Brenner says, there would not be much radioactive contamination to worry about when it comes to the food supply.
Cesium 137 is a different story, since it has a longer half-life, of 30 years. But both forms of radioactive material are heavier than air, and their ability to disperse rapidly is limited.
Still, in the meantime, at least for a few weeks, says Brenner: “Don’t drink the milk [from the nearby area]. The pathway for radioactive iodine to get into human beings is via milk. The iodine hits the ground, gets on the grass, cows eat the grass, and it is concentrated in the milk, and people drink the milk.”
Is there a safe distance to be when a nuclear disaster occurs?
That’s hard to say, since it depends on currents and winds as well as the radioactive half life of potentially dangerous materials released into the air. Fortunately, it appears that the prevailing winds are pushing materials from Fukushima out to sea and away from more populated Japanese cities.
Are the effects of radiation exposure cumulative?
Yes. That’s why regulatory agencies set yearly thresholds of acceptable exposure for employees who regularly work around radioactive material.
Can radioactive particles be transmitted from person to person?
Yes, in two ways. Most commonly, radioactive material that attaches to dust or other small particles and settles on skin or clothing can be transferred during physical contact.
In addition, an individual who is internally contaminated can emit particles in urine, blood or sweat, and coming into contact with these fluids can transmit exposure.
If you are contaminated, how do you get rid of the radioactive material?
External particles of radioactive material can be washed away, but you have to be careful not to spread tiny bits of material onto your skin when removing contaminated clothing.
If the thyroid is contaminated, it can be treated with potassium iodide, which counters some of radiation’s effects on that tissue. The Japanese government has distributed about 230,000 units of iodine to evacuation centers where residents closest to the Fukushima plant have been moved, as a precaution.