2022 journal article

Metal-complexed monoazo dyes as sustainable permanent hair dye alternatives—Toxicological and durability properties

Dyes and Pigments.

By: T. Williams n, F. Vacchi*, A. Santos*, G. Aragão Umbuzeiro* & H. Freeman n

author keywords: Aquatic toxicity; Hair dyes; Metal-complexed dyes; Mutagenicity; Sustainability
Source: ORCID
Added: October 5, 2021

As a new approach to permanent/oxidative hair dyes, we demonstrated that certain monoazo dyes containing substituents that enable diffusion into hair fibers and subsequent chelation/complexation using benign metal ions (Al3+ and Fe3+), rather than a harsh oxidant and strong alkali, merit consideration in this application area. This is important, because billions of individuals worldwide color their hair using permanent hair dye products that can contain aromatic amines and phenols that display genotoxicity and/or skin sensitization (e.g., para-phenylenediamine, PPD). Herein, our work is extended to an examination of the toxicological properties and durability of metallizable monoazo dyes, in comparison to a commercially used permanent hair dye product. Results from the Salmonella/microsome mutagenicity assay and from acute toxicity tests using aquatic test organisms (Daphnia similis, 48-h and Parhyale hawaiensis, 96-h) indicated that the proposed dyes were significantly less toxic than the top-eight permanent hair dye precursors utilized annually. Regarding durability, monoazo dye chelation in situ led to a higher degree of resistance to removal by washing than a commercial permanent hair dye. Taken together, these results further demonstrate the potential of the dyes as sustainable alternatives to conventional permanent hair dyes.