A team of researchers led by Nikolaos Evangeliou, with the Norwegian Institute for Air Research, recently completed the first global survey of radiation exposure from the 2011 Fukushima meltdown. The research estimated the exposure levels of everyone on Earth, finding that most individuals received about 0.02 millisieverts, an amount similar to the exposure from a single X-ray. The research used data from the Comprehensive Test Ban Treaty Organization, which uses a network of measuring stations around the globe to monitor environmental radiation.
“We don’t need to worry,” said Evangeliou. “More than 80 per cent of the radiation was deposited in the ocean and poles, so I think the global population got the least exposure. What I found was that we got one extra X-ray each,” he added.
Meltdowns occurred at three nuclear reactors at the Fukushima-Daiichi nuclear plant in Japan, after the area was hit by a tsunami following an earthquake in 2011.
In Japan, the estimated exposure of the average person was not significantly higher than global levels of exposure, at 0.5 millisieverts. That amount that is near the recommended limit for inhalation of naturally occurring radon gas. As a point of comparison, the average exposure annually for background radiation in the UK is about 2.7 millisieverts a year.
Exposure in Fukushima and the surrounding region was higher in the first three months of the accident, estimated to be between 1 and 5 millisieverts. Even those doses, however, are considered comparatively low. The average CT scan exposes patients to 15 millisieverts. It takes about 1000 millisieverts to bring about radiation sickness.
However, Evangeliou warned that wildlife in the Fukushima area may have been exposed to more dangerous doses. He said increased radiation in that region has been linked to a decline in the populations of birds between 2011 and 2014.
“There have also been reports of declines in other species such as insects and some mammals,” he added.
He said that overall, the dangers from the fallout of the 1986 Chernobyl nuclear incident in Ukraine were much greater than those from the Fukushima meltdown. Quantities of fallout were much larger, and were concentrated in much more densely populated areas. That incident led directly to 31 deaths from radiation exposure within three months of the incident, and another 6,000 cases of thyroid cancer may be linked to exposure in Ukraine, Russia, and Belarus. However, the precise scale of the health impact of that disaster has proven nearly impossible to estimate accurately.