Chrome in leather manufacture: part two
About this essay
We first published essay nine in the Nothing To Hide series in the June-July 2015 issue of World Leather, the second of two essays on the subject of the use of chrome in leather manufacture. Its main author was Dr Dietrich Tegtmeyer in his capacity as the then chair of the research commission of the International Union of Leather Technologists and Chemists Societies (IULTCS). Dr Tegtmeyer is now the global head of business development and industry relations at leather chemicals group TFL. In 2015, he held a similar position at Lanxess and acknowledged the contribution that his colleague Dr Martin Kleban had made to the original essays. We, in turn, want to acknowledge the input we have received from Eurofins-BLC Leather Technology Centre, and especially from technical manager, Georgina Mawer, in updating essays eight and nine.
The most common method used throughout the world for tanning leather is known as chrome tannage. Approximately 85% of all leather is manufactured using this process, and it has been established for more than 160 years. Essay eight focused on the two forms of chromium compounds that the leather industry must take into account, Cr(III) and Cr(VI), and on the equilibrium between them.
In essay nine, our attention turns more towards the way these two forms of chromium compounds behave and the potential effect they can have on human health.
It concludes that, based on science, Cr(III) is not a hazard to consumers or to the workforce in the concentrations used in leather manufacture.
With Cr(VI), however, the picture is more complicated. There are three hazardous risks for which any chemical manufacturer use must be assessed. It is important to know if they are sensitising, carcinogenic or mutagenic. Hexavalent chromium, Cr(VI), presents all three hazardous risks in certain concentrations, but it is reasonable to say that, based on science, any acute toxicity risk from leather can be excluded. It is far beyond any relevant consumer risk.
Assessments show that Cr(VI) is rated as carcinogenic, but only by inhalation (an important workforce safety factor). And, although it is likely to affect a small percentage of people (smaller than for many other substances) Cr(VI) can also be a sensitising allergen.
All chemicals need to be handled with care. The chromium compounds leather manufacturers use are no exception.