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).

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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]).

Source Rappler

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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.