The influence of dose rate on ultraviolet tumorigenesis.
To gain an insight into the relationship between the time in which a daily UV dose is delivered and its carcinogenic effectiveness, the following experiment was performed. Three groups of 24 albino hairless mice (Skh-hr1) were exposed to the same daily dose of UVB radiation (600 J m-2; Philips TL12). The exposure times for the three groups were 1.25, 4 and 12 h per day. A fourth unirradiated group served as a control. All animals exposed to UVB developed multiple skin tumours, whereas the control animals did not develop any observable tumours. Tumour development in the groups exposed for 4 and 12 h was virtually identical. Tumour development was significantly faster in the groups exposed for 4 and 12 h per day than in the group exposed for 1.25 h: the median tumour induction time was reduced by 12%. In terms of the effective dose, this is equivalent to a 25% increase in effectiveness for the 4 and 12 h groups relative to the 1.25 h group. In conclusion, the present experiment shows that prolongation of the exposure duration increases the carcinogenic efficacy of UVB radiation.
Kelfkens
G
G
University of Utrecht, Institute of Dermatology, The Netherlands.
van Weelden
H
H
de Gruijl
F R
FR
van der Leun
J C
JC
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D051379:Mice; D008812:Mice, Hairless; D009381:Neoplasms, Radiation-Induced / Q000473:pathology / Q000503:physiopathology*; D012016:Reference Values; D012878:Skin Neoplasms / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D013997:Time Factors; D014466:Ultraviolet Rays