Final Report On the Safety Assessment of Hc Yellow No. 4

Abstract

HC Yellow No. 4 is a colorant for use mostly in hair dyes and colors, but also in a few hair tints. Concentrations at which the ingredient is used range from 0.1 % to 1.0%. Confusion has existed regarding the proper structure for this ingredient, but was resolved through additional analysis; the correct CAS number is 59820-43-8. Commercially available HC Yellow No. 4 may contain a nitroaniline impurity. Percutaneous absorption studies using commercial products containing 1% HC Yellow No. 4 found little absorption. Body weight decreases were noted in short-term oral toxicity studies and in a subchronic oral toxicity study. HC Yellow No. 4 did not produce irritation, sensitization, or photosensitization in animal tests (primarily using guinea pigs). In some feeding studies, fetal toxicity was observed, but no such effect was found in other feeding studies. HC Yellow No. 4 was mutagenic in several assays, but no evidence of carcinogenesis was found in oral or dermal studies. Two repeated insult patch tests, totalling over 200 human volunteers, found no sensitization reactions. While there was concern expressed over the reproduction and developmental toxicity found in feeding studies, such adverse responses would not be expected from the use of this ingredient in hair coloring products because so little HC Yellow No. 4 is absorbed. The presence of a low level of nitroaniline derivative impurity (0.3 to 7%) is not considered to present a human health risk because the products containing HC Yellow No. 4 are used in a brief and discontinuous manner, followed by rinsing. On the basis of the available data, therefore, it is concluded that HC Yellow No. 4 is safe as a hair colorant in the present practices of use.