Twenty-four young male CB stock rats received 20 once-weekly injections of calcium chromate, suspended in 0-2 ml. arachis oil, given intramuscularly into the right flank; each rat received 19 mg. calcium chromate. Sixteen similar control rats received 20 once-weekly intramuscular injections of 0-2 ml. arachis oil alone. The experiment was terminated after 63 weeks when the surviving animals were killed. Spindle cell and pleomorphic cell sarcomas developed at the site of injection in 18 of the 24 test rats (75%). The first tumour appeared 203 days after the beginning of the experiment and the mean period of induction was 323 days. The tumours were locally invasive but did not metastasise. No neoplasms were found at other sites and no injection-site tumours developed in control rats which received arachis oil alone. These observations confirm the previous account by Hueper and Payne (1959) and indicate that calcium chromate is a potent carcinogen for the subcutaneous tissues of the rat. The present findings, particularly when taken in conjunction with the recent report by Laskin and his colleagues of lung cancers induced in rats with intrabronchial pellets of calcium chromate, indicate that this compound may be at least one of the carcinogens responsible for the well-documented cancer-hazard associated with the chromate-producing industry. © 1969, The British Empire Cancer Campaign for Research. All rights reserved.
