HydroquinoneUpdated a month ago

Hydroquinone is used in skin-lightening cosmetic products. It is also an impurity of synthetic tocopheryl acetate or tocopherol (vitamin E) synthesized using methylhydroquinone. While it has been classified as a carcinogen, in vitro and in vivo studies show that it exhibits some mutagenic properties. Hydroquinone is banned in the European Union.

Sources:

http://journals.sagepub.com/doi/abs/10.1080/10915810290169819
https://www.ncbi.nlm.nih.gov/pubmed/18027166
http://www.safecosmetics.org/get-the-facts/chemicals-of-concern/hydroquinone/