鋳型塗料の発がん性に関する実験的研究

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For the protection of workers against risks of occupational cancer, the most important and fundamental principle is to eliminate carcinogenic agents from the work environment. In iron and steel industries, various substances with unknown components are used for coating the inside surface of ingot case. In order to know whether they are carcinogenic or not, the author carried out biological and chemical assays on nine commercial brands of ingot case coating materials. The results obtained are as follows: (1) Animal experiments: thirty % toluene solution of the test materials and toluene used as control were painted on the shaved skin of 20 male and 20 emale ddN mice, aged 7-9 weeks, thrice weekly until death. The mice treated with materials A, B, C, D, E and F yielded skin tumors, including squamous cell carcinomas at the application site, while no tumor was found in the groups receiving G, H and I. Material A seemed to be most carcinogenic since 17 mice bore skin tumors including 11 carcinoma cases with shortest latent period of 10 weeks. Materials B and C were similar but slightly weaker than A, because tumor bearing mice were 13 (6 cancers) for B and 11 (8 cancers) for C, the latent periods being 20 and 28 weeks, respectively. Materials D and F induced a rather small number of cases of tumor, Namely 5 (3 cancers) and 5 (1 cancers), respectively. Carcinogenicity of E was obscure because of only two papillomas yielded. (2) Chemical analysis: Each of the materials, 0.25-5.0g, was charged on a column of 20-100g of activated aluminum and developed with n-hexane containing increasing amount of benzene up to 30%. 15-30 fractions obtained from each material were examined for absorption spectrum and those with similar spectra were combined, making 10-15 fractions. Each of them was subjected to thin layer chromatographic separation; plates composed of two adsorbent layers (26% acetylated cellulose and aluminum oxide G) and methanol-ether-water (4: 4: 1) being used as developer. Fluorescent spots on the plate were eluted with benzene. Absorption spectroscopy of such elutes yielded approximate amounts of hydrocarbons by means of Cooper's base line technique. Materials which were hard to separate chromatographically were subjected to two additional alumina column chromatographies. Recovery rates for benzo[a]pyrene as determined by the above analytical method but the use of radioactive and non-radioactive benzo[a]pyrene were 67 to 74%. Large amounts of polycyclic aromatic hydrocarbons were detected in materials A, B and C, slightly smaller in D, and small amounts in E and F. Benzo[a]pyrene was 340, 175, 235, 45 and 2 μg/g for A, B, C, D and F, respectively. In G, H and I, no hydrocarbons were found. The results of the chemical analysis were thus very similar to those of the animal experiments. It is highly desirable from the findings of this study that use of carcinogenic ingot case coating materials should be discontinued.

著者

河内清司
九州大学医学部公衆衛生学講座

鋳型塗料の発がん性に関する実験的研究

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