The nuclear accident at Japan's Fukushima plant caused the evacuation of hundreds of thousands of people and sparked fears of a health catastrophe. But nearly two years after the meltdown, a World Health Organization reports says that those fears are unfounded.

Getty Images An anti-nuclear protest in Tokyo in April 2012. Japan is likely to begin restarting its shutter atomic plants.

The World Health Organization’s (WHO) report (PDF) on the estimated health effects from the Fukushima nuclear accident is out, and the results are… reassuring. The WHO modeled the impacts of excess radiation doses on those living around the Fukushima plant, which partially melted down after the earthquake and tsunami on March 11, 2011. The agency concluded that any additional cancer risk from radiation was small—extremely small, for the most part—and chiefly limited to those living closest to the plant. The WHO found:

For leukemia, a lifetime risk increase of around 7% over baseline cancer rates for males exposed to the radiation as infants, and about 6% for females exposed as babies.

For all solid cancers (meaning everything with a discrete tumor mass, including brain and breast cancer), a lifetime risk increase of about 4% over baseline rates for females exposed as infants.

For thyroid cancer (which chiefly occurs in women) a lifetime risk increase of around 70% over baseline rates for women exposed as infants.

Wait a minute, you might be thinking. 7%, 6%, 4%, 70%—those percentage increases actually sound pretty large. Is the WHO saying that those exposed to Fukushima radiation now have a 7% chance of eventually contracting leukemia? Or a 70% chance of contracting thyroid cancer? Isn’t that worrying?

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But that’s not what the WHO is saying. From the report itself:

These percentages represent estimated relative increases over the baseline rates and are not absolute risks for developing such cancers. Due to the low baseline rates of thyroid cancer, even a large relative increase represents a small absolute increase in risks. For example, the baseline lifetime risk of thyroid cancer for females is just three-quarters of one percent and the additional lifetime risk estimated in this assessment for a female infant exposed in the most affected location is one-half of one percent.

What that means is that the risk of getting cancers like leukemia or thyroid cancer is already very, very low, and even those who lived close to Fukushima—and therefore most likely received the highest radiation doses—will see only a small increase in that small danger. As Richard Wakeford of the University of Manchester, one of the authors of the report, told journalists:

These are pretty small proportional increases. The additional risk is quite small and will probably be hidden by the noise of other (cancer) risks like people’s lifestyle choices and statistical fluctuations. It’s more important not to start smoking than having been in Fukushima.

For those who lived beyond the immediately affected areas around Fukushima, the increased risk is likely to be infinitesimal. The report also looked at the brave emergency workers at the Fukushima plant, who likely received higher radiation doses during the meltdown than anyone else in Japan. The news there, too, is mostly good: perhaps one-third of the workers face a higher lifetime risk of cancer, but that risk still remains low.

While an earlier study by researchers at Stanford University estimated that the radiation from Fukushima might result in an as many as 1,300 additional cancer deaths globally, some researchers feel that the WHO may have even overestimated the increased risk from the accident. (And keep in mind that with some 7.6 million cancer deaths each year, 1,300 additional deaths would mean an increase of 0.02%.) Wade Allison, an emeritus professor of physics at Oxford University, told the AP:

On the basis of the radiation doses people have received, there is no reason to think there would be an increase in cancer in the next 50 years. The very small increase in cancers means that it’s even less than the risk of crossing the road.

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I’m pretty sure that Allison means the risk of getting hit by a car while crossing the road, not the risk of getting cancer while crossing the road. But the point is, by the WHO’s own estimates, Fukushima is unlikely to have a very significant health impact on Japanese citizens. Part of that is due to prompt action in the wake of the accident, including the evacuation of nearby towns, and even more importantly, bans on food from the affected areas. After Chernobyl, some 6,000 children exposed to radiation later developed thyroid cancer because many drank irradiated milk—milk that the Soviet government at the time should have banned.

Greenpeace—which put out its own report on the Fukushima fallout earlier this month—wasn’t happy with the WHO, releasing a statement challenging the study from the group’s nuclear radiation expert Dr. Rianne Teule:

The WHO report shamelessly downplays the impact of early radioactive releases from the Fukushima disaster on people inside the 20 km evacuation zone who were not able to leave the area quickly. The WHO should have estimated the radiation exposure of these people to give a more accurate picture of the potential long-term impacts of Fukushima. The WHO report is clearly a political statement to protect the nuclear industry and not a scientific one with people’s health in mind.

Far be it from me to say the WHO, or any international scientific organization, is above reproach. But the WHO’s modeling here seems if anything conservative, overstating the potential risk. And when environmental groups pick holes in scientific consensus on something like Fukushima, they sound very much like the politically conservative climate skeptics who are constantly harping on the supposedly international scientific conspiracy over climate science.

Fukushima, for all the attention, was ultimately small potatoes compared to the disaster at Chernobyl. Tokyo Electric Power Company (TEPCO) reported that the Fukushima plant may have released about 900,000 terabecquerels of radiation into the air at the height of the disaster, while the 5.2 million terabecquerels of radiation were released during the Chernobyl accident, which also covered a much bigger territory. It’s just a reminder that’s what true about natural disasters is true about man-made ones: the public response or lack of one can matter as much or more than the disaster itself.

But it’s also pretty important that the human health effects of one of the biggest nuclear disasters seem to be virtually nil. That’s worth remembering as nations turn away from nuclear power on the grounds that it is simply too dangerous. In the wake of the Fukushima accident, Germany decided to begin shuttering its nuclear power plants years before they were do to close. The result, as Bloomberg reported yesterday, has been more coal, more pollutants and more carbon. New coal plants with about 5.3 GW of power capacity will begin operating in Germany this year, far more than the 1 GW of coal that is likely to come offline. Greenhouse gas emissions rose 1.6% in Germany last year. The increase in coal—due in part to the reduction in carbon-free nuclear power—has more than outweighed the vast increase in renewable power created by Germany’s progressive energy policy.

The challenging economics of building new nuclear plants are another question, especially in developed countries. But it’s very difficult to see the logic of voluntarily shutting down the biggest source of carbon-free electricity when it turns out the dangers of nuclear power seem to be overstated. (Tokyo seems to agree—Japanese Prime Minister Shinzo Abe announced that the country would begin restarting idled nuclear plants once new safety guidelines are in place later this year.) And it’s not just carbon—if existing nuclear is replaced by coal or even natural gas, we’ll also see an increase in other pollutants which pose clear and present health dangers that exceed the risks of atomic power. Nuclear power is scary—scarier than climate change for most people—but the facts don’t back up that fear.

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