Screen captures from the documentary Pandora’s Promise
The sievert (Wikipedia)
1 Sv = 1 joule/kilogram – a biological effect. The sievert represents the equivalent biological effect of the deposit of a joule of radiation energy in a kilogram of human tissue.
Background radiation is measured in microsieverts per hour (one millionth of a sievert).
• • •
As of January 30, 2014, there are areas within the [Fukushima] prefecture with radiation levels as high as 2.880μSv/h (microSieverts per hour). Minamisoma Municipal Office [20 km from the reactors] had a record high of 0.130μSv/h. (1 μSv/h = 0.001 mSv [milliSieverts]).
• • •
Twenty km from the Fukushima the radiation level (0.130μSv/h) is roughly that of Paris (0.100μSv/h) and much less than Rio de Janeiro or New Hampshire.