Final report on the safety assessment of methyldibromo glutaronitrile

Abstract

The halogen compound Methyldibromo Glutaronitrile is used in a wide variety of cosmetics as a preservative. Concentrations in cosmetic formulations reportedly range from 0.0075 to 0.06%. The oral LD50 in rats is 640 mg/kg. Dogs on a diet of 4,000 ppm Methyldibromo Glutaronitrile for 13 weeks developed thyroid hyperplasia: those on a diet of 167 ppm exhibited no hyperplasia, although the thyroid glands were enlarged. Application of Methyldibromo Glutaronitrile at a level of 4.0 g/kg to the skin of rats for 21 days produced severe irritation. A concentration of 0.025% applied to the skin of rabbits in a 28-day dermal toxicity study resulted in only slight to moderate irritation. No evidence of sensitization was found in guinea pig studies, nor was photosensitization reported in mouse studies. No reproductive or developmental toxicity was noted in two rats studies. Methyldibromo Glutaronitrile was not mutagenic in a series of mammalian system test. Clinical data using repeat insult patch testing (HRIPT) methods indicated that concentrations as low as 0.025% produced a positive reaction in a few individuals. To limit the possibility that formulations containing this ingredient will lead to sensitization, it was concluded that leave-on formulations should contain ≤0.025% Methyldibromo Glutaronitrile. Rinse-off formulations, because the duration of exposure is much less, are considered safe as currently used.