Toxicologic studies of tin needles at the intrathoracic site of mice

Male Marsh mice which received a single intrathoracic injection of 4 mg of tin needles at 3 months of age were compared with controls given isotonic saline. The form and size of most of the tin needles were similar to those of asbestos needles which produced mesotheliomas and lung neoplasms in rodents. Water and food intake was markedly reduced for 24 hrs after the injection of tin. Survival rates (followed for 19 months), pathology of the bladder, liver, and kidney, as well as local and general cancer development were not adversely associated with the tin treatment as compared with the tin treatment as compared with controls. The local reaction to the tin included giant cell phagocytosis, nodular fibroplasia, and capillary formation. The failure of the tin needles to induce local neoplasms may relate to their high density as compared with silicates and/or their lack of the unique potential of the silicate particles to stimulate avascular fibrosis.