In August 2018 Ethical Consumer viewed Nkuku's website and found that it sold products made from leather. It stated "The leather we use is sourced from India.The leather is a bi-product of the food industry. We carefully select our leather hides and use natural, traditional treatments to retain its individual character. Depending on the leather collection, we use either natural vegetable dyes or azo free chemical dyes."
As leather was a slaughterhouse byproduct the company lost half a mark under Ethical Consumer's animal rights category.
Leather, as the hide of a dead animal, naturally decomposes. To prevent this decomposition the leather industry uses a cocktail of harmful chemicals including trivalent chromium sulphate, sodium sulphide, sodium sulfhydrate, arsenic and cyanide to preserve it. Tannery effluent also contains large amounts of other pollutants, such as protein, hair, salt, lime sludge and acids. These can all pollute the land, air, and water supply making it a highly polluting industry. As a result the company lost half a mark in the Pollution and Toxics category.

Reference:

www.nkuku.com (15 August 2018)