Lung carcinomas in rats after low level cadmium inhalation†

Abstract

Three groups of 40 male Wistar rats were continuously exposed to CdCl₂ aerosols at 3 concentrations: 12.5, 25 and 50 μg/m³ for 18 months. Forty‐one rats kept in fresh air served as controls. Thirteen months after termination of the exposure, the surviving animals were sacrificed. Body weights and mortality were not significantly different between the four groups. Primary lung carcinomas, i.e. epidermoid carcinomas, adenocarcinomas, combined epidermoid and adenocarcinomas, and mucoepidermoid carcinomas were found in 71.4% (50 μg/m³ group), 52.6% (25 μg/m³ group) and 15.4% (12.5 μg/m³ group) of the animals respectively. In addition, metastases in regional lymph nodes and the kidneys and invasion into regional lymph nodes and the heart were observed. Lung adenomas and nodular hyperplasia developed in several rats of the exposed groups. No primary lung tumors were found in the control group. These studies revealed a dose dependent incidence of primary lung carcinomas after inhalation of CdCl₂ aerosols in rats. Even a concentration of 12.5 μg/m³—well below present TLV values—led to a significant lung carcinoma rate.