Abstract
Summary
1. Adsorption of 20-methyl-cholanthrene, 3,4 benzpyrene and p-dimethylaminoazobenzene to 7 different carbon blacks has been determined quantitatively. Differences in the amount adsorbed are related not only to the specific carcinogen but also to the total surface value of a carbon black. 2. Administration of carbon black alone by feeding, painting and subcutaneous injection did not produce any benign or malignant tumor in 460 animals. 3. The carcinogenicity of p-dimethylaminoazobenzene was almost completely inhibited by carbon black. Only 1 out of 72 animals fed carbon black adsorbed azo dye developed a hepatoma. 4. Administration of carbon black adsorbed 20-methyl-cholanthrene and 3,4-benzpyrene in combination with olive oil and acetone respectively inhibited carcinogenesis to a lesser degree. The incidence of tumors occurring in these experiments was approximately that expected from the concentrations of the free carcinogen eluted by the vehicle from the carbon black. 5. It is therefore suggested that in the adsorbed state all 3 compounds tested are not carcinogenic and that carcinogenicity in two of the compounds was restored due to elution by either olive oil or acetone.
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