Increases in the incidence of cancerous lung tumors among human and animal subjects exposed to cadmium-oxide (1306190) and cadmium- chloride (10108642) are reviewed by NIOSH. A 1978 epidemiological study of 602 workers employed in a cadmium (7440439) smelting facility between 1940 and 1969 showed that mortality as a result of respiratory tract cancer was significantly greater in the cohort as a whole compared to the population of the United States in general, with all respiratory deaths resulting from lung, tracheal, and bronchial cancer. In addition, this study demonstrated that lung cancer mortality rises as cumulative exposure to cadmium is increased. Another study of 6,995 exposed workers in 17 facilities producing cadmium, alloys, cadmium soap, and pigments showed the lung cancer mortality rate observed to be slightly higher than the anticipated value. During experiments conducted on rats, 71.4 percent, 52.6 percent, and 15.4 percent of the animals exposed to cadmium-chloride aerosols by inhalation at concentrations of 12.5, 25, and 50 micrograms per cubic meter, respectively, 23 hours a day, 7 days a week, for 18 months developed primary lung carcinomas. Similar results were obtained during the exposure of rats to cadmium- oxide via single inhalations and multiple intratracheal injections. NIOSH concludes that additional research is needed in order to further assess the carcinogenicity of cadmium in animals, as well as to ascertain the nature of the mechanisms by means of which cadmium exerts its cancerous influence. NIOSH recommends that cadmium and its compounds be regarded as potential occupational carcinogens. It is further recommended that the present OSHA standard governing exposure to cadmium be reexamined in light of the new data which has recently been uncovered.