That's equivalent to one or two CAT scans, according to the American College of Radiology. Even on the upper end of the scale, that barely raises the risk of dying from cancer, the college says.
According to United Nations nuclear experts, exposure to less than 1,000 mSv annually causes no meaningful increase in the risk of getting cancer.
Smoking is much more likely to.
And coal-fired power plants kill more people than their nuclear counterparts do, according to the Clean Air Task Force. Resulting air pollution was expected to cause nearly 13,200 deaths in 2010, not to mention 20,000 heart attacks per year.
Radiation occurs naturally. We are exposed to it through some minerals and from the sun. "The average person in the U.S. receives an effective dose of about 3 mSv per year," the American College of Radiology says.
The rest of Fukushima prefecture saw 3 to 5 mSv in the first year, the equivalent of an X-ray.
Although that may be less upsetting to know, after the Daiichi catastrophe, there have been discomforting signs -- and wonders.
Scientist found butterflies with a variety of mutations in Fukushima prefecture and beyond.
Radioactive iodine poured into the ocean at the reactor site, spiking at 1,250 times normal levels. Offshore monitoring stations also detected high levels of cesium, a radioactive element.
More than a year after the disaster, fish caught off the coast of Fukushima exhibited levels of cesium up to 250 times the amount the Japanese government approves for consumption.
Isolated tests have revealed higher than normal concentrations of radioactive elements in other agricultural products in surrounding areas in the past.
Though the WHO sees no significant danger of radioactivity in the food chain raising the cancer risk, who wants to be the unlucky person to eat the wrong fish?
And although the cancer risk has risen only slightly in a very small area, this will be little comfort to the few additional people who get cancer after having been exposed to radiation near the Daiichi plant as little girls or young men.
The WHO's report stresses that although its research has been thorough, the final effects of the radiation disaster won't be known until sometime in the future, when scientists will have the benefit of hindsight.