Needle fibers of an azo-dye mixture induce polyploidy in a Chinese hamster cell line CHL.

In a routine Safety evaluation of chemicals included in household products, we found a mixture of azo dyes (CMBA, main component: N-[5-[(2-cyanoethyl)ethylamino]-4-methoxy-2-[(5-nitro-2,1-benzisothiazol-3-yl)azo]phenyl] acetamide) that precipitated in the culture medium in a characteristic fiber form (around 2 - 33 microm in length) similar to that of asbestos. We compared CMBA with an asbestos, chrysotile B, in a cytotoxicity, chromosome aberration (CA), and micronucleus (MN) test in a Chinese hamster lung cell line (CHL). In the cytotoxicity test, the 50% growth inhibition concentration was 11.0 microg/ml for CMBA and 0.398 microg/ml for chrysotile B asbestos. CMBA and chrysotile B both induced polyploidy in the CA test and equal-sized binucleated and polynuclear cells in the MN test. CMBA differs from chrysotile B chemically. The former is an organic chemical and the latter is a mineral. Although CMBA is soluble in methanol and can be safely disposed by burning, it should be handled carefully when manufactured in a factory.