Few reports were published on exhalation of a radioactive substance into the air from animals injected with it. For safe handling of iodine-125 in research using animals, we examined daily changes of airborne release of radioactivity from housing cages, containing mice treated with Na 125I or125I labelled anti-mouse monoclonal IgG1κ. Airborne radioactivity was collected during 100 min with a flow rate of 10l/min with charcoal filters and measured every 24 h during the period of 4 days. Radioactivity in the removed organs was also measured after 96 h of the time when the mice were sacrificed. Different patterns were observed in airborne radioactivity for different chemical forms of injected radioisotope, i.e. Na125I or125I labelled anti-mouse monoclonal IgG1κ. For Na 125I injection, the radioactive concentration in air was highest at 24 h after injection. The concentration decreased gradually from 24 to 96 h, to one seventh at 96 h. Contrary, in the125I labelled anti-mouse monoclonal IgG1κ injection, the radioactivity was low at 24 h and became highest at 96 h. The radioactivity only in the thyroid gland was higher in the Na 125I than in 125I labelled anti-mouse monoclonal IgG1 κ injection. The radioactivity in the submaxillary gland, liver, kidney, stomach and lung was higher in the125I labelled anti-mouse monoclonal IgG1κ than in Na 125I injection. These results indicate that the different chemical forms of125I compounds show different patterns not only in the distribution in the organs but also in the exhalation.
Analysis of99Tc in the environment have been interested because of a long term radioecological effect of99Tc due to its long half-life. One of the problems on99Tc analysis is a tracer since there is no stable isotope in Tc. Development of99Tc determination by ICP-MS enables us to use95mTc as a yield monitor. The radiochemical yield is evaluated by gamma spectrometry of95mTc and99Tc is determined by mass spectrometry without any in-terference by95mTc tracer added to the sample. We produced95mTc without99Tc by an irradiation of metal Nb with 40MeV alpha particles using cyclotron. The 0.1 mm thickness Nb foil stacked 4 pieces was irradiated for 21 h at beam current of 1.5μC, dissolved in a mixture of HNO3and HF, and95mTc was isolated and purified chemically. No contamination of99Tc was confirmed on95mTc fraction.