Number

097-EN

Section

General Section

Use

Abstract

The most common method for tanning hides and skin into leather has long been chrome tanning. Chrome is however associated with negative effects both on human health and the environment. A good alternative to chrome based tanning is vegetable tanning using agents such as bark from the mimosa tree.

Substituted substances

Alternative Substances

Reliability of information

Evidence of assessment: there is evidence of an official (positive) assessment of the substitution

Reason substitution

CMR

Hazard Assessment

Substance to be substituted: The main hazard in using chromium (III) is that under certain conditions it can be transformed to chromium (VI). Chromium (VI) has been classified as a carcinogen by the IARC and as a potential sensitiser by REACH regulation. Chromium (VI) is listed in the database of hazardous substances according to SUBSPORTplus screening criteria (SDSC). Alternative substances: Chromium (III) and tannic acid are not listed in the database of hazardous substances according to SUBSPORTplus screening criteria (SDSC). Tannic acid and chromium (III) have no harmonised classification according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation)..

Description of Substitution

In order to convert hides or skins into leather some sort of tanning process is necessary. Most tanneries around the world today use trivalent chromium. Chromium is however associated with several negative effects on the environment and human health. An alternative to using chromium is to use natural tannic acids that can be extracted from the leaves and barks of trees. This is how hides used to be tanned before the introduction of chromium based tanning. One tannery using this technology is Tärnsjö Garveri in Sweden where this case study comes from. The compound which is used as a substitute for chromium (III) in Tärnsjö is tannin extracted from the mimosa tree. Tannins are applied after the pickling in the tanning process and are poured into large wooden barrels along with the hides. The hides along with the tanning agent are then rotated for 10-12 hours which allows the tanning agent to completely penetrate the hides. After this the hides undergo the rest of the tanning process, which is identical for both vegetable tanning and chromium based tanning. Drawbacks in using natural tannic acid instead of chromium is that the process is more expensive and time consuming. Hides tanned with chromium are also slightly more elastic while chromium has however many drawbacks related to health and the environment. Trivalent chrome can be transformed into hexavalent chrome which is sensitising, carcinogenic and toxic. All forms of chrome are also potential pollutants of soil and are not biodegradable.

Case/substitution evaluation

Chromium (VI) has been classified as a carcinogen by the IARC and as a potential sensitiser by REACH regulation. Since chromium (III) can transform into chromium (VI), chromium (III) are inappropriate to use for making leather products which is often worn close to the skin. Vegetable tanning based on tannic acid is a preferable alternative since it is not associated with any hazard statements and can make the leather biodegradable in contrast to leather tanned with chromium. This case study shows the successful replacement of harmful chemicals with non-harmful chemicals. The BVT Information sheet "Leather Industry" dates from 2013, in which there is no mention of substitutes for chromium, the date of the case study is unknown. Therefore, the substitution of chromium in this sector of use is probably not yet state of the art.

State of implementation

Full capacity

Date and place of implementation

sweden

Availability ofAlternative

The alternative is on the market.

Producer/Provider

http://tarnsjogarveri.com/wip/en/

Type of information supplier

Producer / distributor

Contact

http://tarnsjogarveri.com/wip/en/

Date, reviewed

December 11, 2020