That is the Linear, No Threshold model is nonsense at low doses. By the way 30 cSv is equivalent to the radiation we would get from nature in about 100 years. Since there are no data below 30 cGy they extrapolate a huge distance and then claim that the linear, no threshold is an appropriate model. There have been about 90,000 children and grandchildren of the A-bomb survivors and still no detectable increase in genetic mutations. Fruit flies and mice show genetic mutations but so far, no humans.
All animals have repair mechanisms, humans seem to have better than average.
This doesn't prove radiation hormesis but it is inconsistent with the LNT model. The dosimetry for the A-bomb survivors is not good but it is better than in Chernobyl. No measurements were made on anybody either place. It now appears from recent studies that the 1965 estimates are closer to the truth. Radiation effects depend on strongly on the rate.