Clearing the Chromium/Chrome Tanning Confusion
There is much inaccurate information in circulation regarding the use of chromium salts and their associated safety for the tanning of leather.
Approximately 80% of global leather production is tanned with safe chromium 3 salts. It is a highly effective tanning agent producing a leather with a flexible range of properties making it suitable for many end uses.
Chromium is a transition metal that can exist in a number of different oxidation states each with distinctive properties.
This is a steel grey, hard metal found as chromite ore (it does not occur in the metallic state naturally). It is used to harden steel, to manufacture stainless steel, and to form alloys. It is also used in plating to produce a hard corrosion resistant surface.
Trivalent chromium – Chrome 3 – Cr3 – Cr III
Trivalent chromium 3 compounds occur naturally in the environment. They are found in rocks, soil, plants and volcanic emissions. Chromium salts are present in foodstuffs and are a necessary nutrient for the human body as trivalent chromium 3 is required for the normal metabolism of fats and sugars. Nutritional supplements are currently on sale containing chromium picolinate. Chromium 3 sulphate is considered safe to use in leather manufacture.
Hexavalent chromium – Chrome 6 – Cr 6 – Cr VI
Hexavalent chromium 6 is the hazardous form of this element. It can be formed when trivalent chromium is oxidised. This usually occurs in the presence of oxygen combined with other factors such as extremes in pH. The salts have a characteristic yellow colour and are classified as carcinogens. Chromium 6 is not used in the chrome tanning of leather.
What is Chrome VI?
Hexavalent chromium VI is the hazardous form of this element. It can be formed when trivalent chromium is
oxidised. This usually occurs in the presence of oxygen combined with other factors such as extremes in pH. The salts have a characteristic yellow colour and are classified as carcinogens. Chromium VI is not used in the tanning of leather.
What are the risks of Chrome VI?
Chrome VI is recognized as a human carcinogen when it is inhaled. Chronic inhalation of Chrome VI has been shown to increase risk of lung cancer and may also damage the small capillaries in kidneys and intestines. Other adverse health effects associated with Chrome VI exposure, according to the National Institute for Occupational Safety and Health (NIOSH), include skin irritation or ulceration and allergic contact dermatitis
What legislation relates to Chrome VI?
Following an EU proposal there will be a new requirement which prohibits the placing on the market of leather
articles and articles containing leather parts if the content of chromium VI is equal to or greater than 3 mg/kg of the total dry weight of leather in the leather article or the leather parts. The restriction will apply to leather parts that under normal or foreseeable use come into contact with the skin. The restriction, which is written in Annex XVII of REACH, becomes effective from 1st May 2015.