In the radiobiology and carcinogenesis studies, progress has been made in understanding the first steps of cancer development, but not to the point of validating a reference dose-effect model. The only certainty gained is that the process is very complex, the resulting dose-effect response being complex, and most probably not a linear one. Biologically based models have also been proposed that could project substantially reduced carcinogenicity at low doses.[1][88][89] In the epidemiological field, no definite conclusion has been reached.