Particularly environmentally relevant criteria
In addition to general legislation, however, there are also chemical substances which are prohibited by consumer protection NGOs (non-governmental organizations):
PCP (pentachlorophenol), a preserving agent which is predominantly used in tropical countries, but has no longer been in use for more than twenty years in Europe.
Various azo dyes that contain one of the 20 amines listed in the German Foods and Commodities Ordinance. This means that not all azo dyes in general are prohibited but only a few individual ones. Incidentally, the textile industry uses azo dyes in much larger quantities than the leather industry.
Formaldehyde (not to be confused with glutaraldehyde) which can be used as an auxiliary tanning agent. Formaldehyde is also used as a cross-linking agent for casein-based finishes.
Hexavalent chromium (not to be confused with trivalent chromium) which may be formed from chromium III in the tanning agent under extreme conditions.
It is the responsibility of each tannery to issue declarations as to whether these products are contained in their leathers or not. The tanneries still remaining in Switzerland have no problem at all in confirming that the above-mentioned products are not contained in their leathers.