title: Threshold dose-response in radiation carcinogenesis: an approach from chronic beta-irradiation experiments and a review of non-tumour doses.
abstract: OBJECTIVE
  To discuss the threshold dose problem in radiation carcinogenesis after a review of the present author's experimental data on mouse tumour induction by chronic beta-irradiation and other relevant data.
  
  
  CONCLUSIONS
  A threshold dose-response in radiation carcinogenesis appears in certain tissues and under certain conditions. The optimum condition for demonstrating an apparent threshold is with partial-body chronic or repeated radiation rather than with acute whole-body radiation. Its possible mechanism is host tolerance, involving DNA repair, apoptosis and an immune response activated by low radiation doses. This tolerance level was examined by a survey in the literature of non-tumour-inducing doses, D(nt), the highest dose at which no significant increase of tumours was observed above the control level.
authors.affiliation: Genetics Division, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. htanooka@ncc.go.jp
authors.forename: H
authors.initials: H
authors.lastname: Tanooka
mesh_terms: D000818:Animals; D001610:Beta Particles / Q000009:adverse effects*; D015197:Carcinogenicity Tests; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology / Q000209:etiology*; D011836:Radiation Tolerance; D013997:Time Factors