This chapter analyses the emergence and development of the 'low-dose' exposure issue, taking the iconic case of nuclear power as its starting point. At the end of the 1940s, on the basis of the observation that radiation caused genetic mutations whatever the dose may be and that it was impossible to confirm their safety, various American scientists suggested changing the term for exposure limits from 'tolerable dose' to 'permissible dose'. At the end of 1969, American scientists John Gofman and Arthur Tamplin presented an exhaustive summary of six years of work funded by the Atomic Energy Commission (AEC), on the links between exposure to low doses of radiation and cancers. One of the main traits of the low-dose controversy was the shift back and forth between a precise criticism, of a technical order, relating to the link between exposure and effects, and a generalized criticism of the nuclear industry and decision-making modes within this area.