Inhalation research with different cadmium compounds on Wistar rats, Syrian hamsters and NMRI-mice
Inhalationsversuche mit verschiedenen Cadmiumverbindungen an Wistar Ratten, Syrischen Hamstern und NMRI-Mäusen
In a long-term inhalation study four different Cd-compounds, Cd-chloride (CdCl2), Cd-oxide (CdO) as dust and smoke, Cd-sulfate (CdSO4) and Cd-sulfide (CdS) are used. A separate group of rats was exposed to an aerosol mixture, consisting of zinc oxide (ZnO) and Cd-oxide (CdO) dust. The rats are kept in groups of ten animals per cage, the mice in groups of 12 and the hamster individually. The numbers of rats, hamsters and mice per group and sex are 20, 24 and 48, respectively. The animals are exposed in horizontal flow inhalation chambers of 225 l volume each. The aerosol-flow is 80 liters per minute. Each chamber contains two (rats) or four (hamsters, mice) stainless steel wire mesh cages. As in the previous CdCl2 experiment the rats were exposed to the aerosols for 18 months, lasting 7 days per week and 22 hours per day. The mice and Syrian hamsters are exposed for 6-18 months, 5 days per week and 19 hours per day. At the end of exposure the animals are transferred to Macrolon cages an d kept under conventional conditions in clean air until death. In a former pilot study and a long-term study on the inhalation of Cd-chloride aerosols by Wistar rats we had shown that relatively low Cd-concentrations induced primary lung carcinomas. Several authors presumed that for some occupations cadmium aerosols might be a carcinogenic risk. (IUCT) Since CdCl2 has proven to be carcinogenic in rats after exposure to very low concentrations, there was an urgent need to investigate the more occupationally relevant compounds CdO, CdSO4 and CdS for their caracinogenic potencies after inhalative exposure. This task was taken over jointly by two Fraunhofer Institutes. To exclude species specific effects beside rats, hamsters and mice were used in this ongoing long-term inhalation study using the above mentioned four Cd compounds in various exposure concentrations. The animals are exposed for 8 or 19-22 hrs/day 5-7 days/week and for 6-18 months. Despite of its very low solubility also CdS induced severe toxic effects in the lung using exposure concentration of up to 2.4 mg Cd/cbm. For these CdS groups as for other groups, which showed cadmium related toxic effects, the exposure had to be finished prematurely. Lower Cd concentraions or shorter exposure times per day were used replacing these groups.