[Radioprotection during clinical and laboratory utilization of tritium-labeled thymidine (author's transl)]

In view of the new prescriptions for radioprotection of the Helevetic Confederacy (Eidgenössische Strahlenschutzverordnung) the problems of radioprotection connected with utilization of the pure beta-ray emitter tritium are exposed, since the latter frequently is used as a marker substance in biomedical investigations. Inorganic tritum is regarded as the least toxic radionuclide. With tritiated thymidine, very often used for study of cell proliferation and cellular kinetics because of its incorporation into DNA, the radiation risk has to be considered quite differently. Its radiotoxicity is estimated to be superior by a factor up to thousand. The increased risk, thus resulting, is discussed with regard to the findings by animal experimentation and to the toxicity in man. Practical recommendations for the use of tritium-thymidine are given.