It is two years since Japan's 9.0- magnitude earthquake, one so powerful it shifted the position of the Earth's figure axis by as much as 6 inches and moved Honshu, Japan's main island, 8 feet eastward. The tsunami generated by the earthquake obliterated towns, drowned almost 20,000 people and left more than 300,000 homeless. Everyone living within 15 miles of Fukushima was evacuated; many are still in temporary housing. Some will never be able to return home.

More than 300,000 buildings were destroyed and another million damaged, including four reactors at the Fukushima Daiichi nuclear power plant on the northeast coast. The earthquake caused the immediate shutdown of this and three other nuclear-power facilities.

In this April 16, 2011 file photo, Wakana Nemoto, 3, standing next to her mother Naoko, receives a radiation exposure screening outside an evacuation
In this April 16, 2011 file photo, Wakana Nemoto, 3, standing next to her mother Naoko, receives a radiation exposure screening outside an evacuation center in Fukushima, northeastern Japan. (Hiro Komae/Associated Press)

Since the earthquake, a powerful movement gained momentum to halt Japan's use of nuclear energy, which provided 30 percent of the country's electricity. The last of 54 nuclear reactors was shut down in May 2012. Two facilities were restarted in June 2012; 52 remain shut. Japan has therefore had to increase its imports of natural gas, low-sulfur crude oil and fuel oil at a substantial economic and environmental cost. Seventy-five percent of the country's electricity now comes from fossil fuels.

Accustomed to large trade surpluses, Japan, in 2012, had a record $78 billion trade deficit, thanks to increased energy imports and a drop in exports as Japanese goods became more expensive to produce.


And what of the lasting threat from radiation? Remarkably, outside the immediate area of Fukushima, this is hardly a problem at all. Although the crippled nuclear reactors themselves still pose a danger, no one, including personnel who worked in the buildings, died from radiation exposure. Most experts agree that future health risks from the released radiation, notably radioactive iodine-131 and cesiums-134 and - 137, are extremely small and likely to be undetectable.



In this April 7, 2011 file photo, Japanese police, wearing suits to protect them from radiation, search for victims inside the deserted evacuation zone,
In this April 7, 2011 file photo, Japanese police, wearing suits to protect them from radiation, search for victims inside the deserted evacuation zone, established for the 20 kilometer radius around the Fukushima Dai-ichi nuclear reactors, in Minamisoma, Fukushima prefecture, Japan. (David Guttenfelder/Associated Press)

Rather than stand as a warning of the radiation danger posed by nuclear power, in other words, Fukushima has become a reminder that uninformed fears aren't the same as actual risks.

Why are the anticipated risks from Japan's nuclear accident so small? Perhaps the most important reason is that about 80 percent of the radiation released was blown into the ocean. Radioactive contamination of the sea sounds dreadful, but because oceans naturally contain large amounts of radioactive materials, the net increase in oceanic radioactivity is minuscule.

Another reason the public was protected is that the 200,000 or so people living within 15 miles of Fukushima were rapidly evacuated. People living in a few hotspot towns slightly farther away who didn't leave on their own received the highest civilian doses.

The quarantine of radiation-contaminated foodstuffs also kept the public safe. Milk containing iodine-131 was responsible for many cases of thyroid cancer in children after the 1986 Chernobyl nuclear accident in Ukraine. In Japan, nonradioactive iodine pills were distributed to the population to block uptake of radioactive iodine by the thyroid.

In the 26 years since Chernobyl, there have been more than 6,000 cases of thyroid cancers, almost all in children who were less than 16 years old when they were exposed to iodine-131, predominately through milk and other contaminated foodstuffs. Fortunately thyroid cancer in children is rarely fatal; there have been fewer than 15 deaths. There may also be a slight increase in leukemia risk among the 600,000 workers involved in containing the accident.

Even so, there is no convincing evidence, at least as yet, of an increased cancer risk in the thousands of evacuees from the town of Pripyat, where the reactor was located, nor among the 30 million living in contaminated lands. Also, as with Fukushima, there is no convincing evidence of birth defects or genetic abnormalities. (Gale helped treat the worst cases of radiation poisoning at Chernobyl and has been involved with the follow-up in the years since the accident. He has been involved in Japan since the catastrophe and worked with Japanese scientists to estimate health risks.)

Radiation spikes detected in the weeks and months following the Fukushima accident caused concern and sometimes panic. One day a higher-than-permissible level of iodine-131 (300 becquerels per liter, or less than 0.00008 parts per trillion) was detected in the drinking water in Tokyo. People immediately emptied stores of bottled water. However, the amount of contamination in Tokyo water was so low, Tokyoites would have had to drink 6 quarts of it a day for a month to get the same radiation dose that an airline crew member receives in a year of flying between Los Angeles and Tokyo.

People naturally worried about eating fish from the ocean around Fukushima, and stringent mitigation actions were taken. Bluefin tuna caught off California six months later were found to have traces of cesium-137 from Fukushima, though less ounce for ounce than the amount of radioactive potassium-40 found in a banana.

The important question is, how can we be certain any food source is safe if higher-than-normal radiation levels are detected? The best way to answer this is to consider the risk involved with eating food that may be contaminated. U.S. food safety standards, for example, often restrict the content of carcinogens, including radiation, to levels that might cause a 1-in-100,000 or 1-in-1,000,000 lifetime risk of cancer. But consider the average 50-year-old male who has a baseline risk of 43 percent to develop cancer in his lifetime. (In women, it's 39 percent.) The contaminated food increases that 43 percent lifetime risk to 43.0000001 percent.

Exposure to radiation isn't always what it seems. Of course, people in the path of a radioactive cloud may receive a dangerous dose of radiation, depending on the concentration of radionuclides, atmospheric conditions and their location - indoors or outside - when the plume passes. Immediate countermeasures are essential. In Japan, laudably, most people were sheltered in place and then evacuated in a relatively controlled manner. Some people received iodine tablets.

An independent commission found considerable confusion among Japanese government officials, personnel at the nuclear power facility and executives at Tokyo Electric Power Company in Tokyo. Furthermore, emergency authorities didn't share or use some important data on radioactive contamination, and that caused some people to be evacuated to zones of higher radioactive contamination. And some children remained in high- radiation areas far too long. Nevertheless, official actions largely protected the public, and most continuing fears of health risks from radiation have little basis in fact.

Prudence and safety must be paramount in the use of nuclear energy - in fact, in the use of any kind of energy. Although immediate and long-term health risks of nuclear accidents are often exaggerated, social, psychological and economic consequences are obviously enormous. We don't believe that nuclear energy is always the best choice, but it is important to carefully weigh the risks and benefits of using nuclear energy compared with other sources of fuel to generate electricity.

Japan has few domestic energy resources and depends on imports for about 85 percent of its energy. What price will the country pay if it abandons nuclear energy and uses only fossil fuels? Air pollution from coal-fired power plants causes about 500 times more deaths per unit of electricity produced than radiation from nuclear plants does. Electricity produced from oil isn't much safer. Even natural gas causes about 60 times more deaths than nuclear does because of pollution. And consider that more than 100,000 coal miners died in the U.S. in the past century and more than 6,000 die every year in China.

If, in response to Fukushima, Japan switches to more fossil fuels, the resulting carbon dioxide emissions, greenhouse gases and global warming could affect all of us. Already, because of the nuclear shutdown since the accident, there is no longer any chance Japan will meet its commitments in the 2009 Copenhagen Accord to cut greenhouse-gas emissions from 1990 levels by 25 percent by 2020. The country's 2012 estimate for greenhouse gases is about 1.3 billion tons, the most since 2007, making Japan the fifth top emitter worldwide.

We support stringent safety requirements for operating all nuclear power facilities, in Japan and everywhere else, including the Bushehr facility in Iran. But no energy-producing operation is foolproof: mines collapse, ships run aground, terrorists blow up pipelines and nuclear plants have meltdowns (fortunately rarely). Citizens of Japan are understandably traumatized by the 2011 earthquake and tsunami. But to make intelligent decisions about radiation, it's best to rely on facts - and not let emotional or illogical fears get in the way.

Robert Peter Gale, a visiting professor of hematology at Imperial College London, has for 30 years been involved in the global medical response to nuclear and radiation accidents. Eric Lax is a writer whose books include "The Mold in Dr. Florey's Coat" and "Conversations with Woody Allen." They are the authors of "Radiation: What It Is, What You Need to Know."