Implications of a threshold effect
The estimates of how many potentially fatal cancers result from exposure to radiation vary considerably. If we accept the ICRP proportionality relationship between dose and effect, even the tiniest of doses could lead to fatalities. According to this linear rule, the exposure to natural radioactivity (an average of 2.5 mSv per persons per year), medical exams (1 mSv) or even nuclear industry (0.010 mSv) could cause thousands of death in France alone. If, however, these ionising radiations are harmless for doses under a threshold of 1 or 2 hundred millisieverts, the total number of deaths would be practically 0. More advanced models predict a less spectacular drop below a given threshold, but nonetheless propose a reduction in risk for small doses.