A Method to Distinguish Chromium-Tanned Leathers With Low and High Risks of Surface Hexavalent Chromium

Traces of hexavalent chromium, Cr(VI), are a major concern for skin contact with Cr-tanned leather. Current extraction methods (ISO 17075-1:2017) for Cr(VI) testing do not necessarily reflect the true potential of surface-formed Cr(VI), as extracted concentrations are dependent on previous storage and atmospheric conditions.

To test whether a spiking method protocol can distinguish leathers with high and low risks of releasing Cr(VI).

Two groups of leather types were selected based on previously detected Cr(VI) (group A) and optimal tanning practices with high antioxidants (group B), corresponding to a high and low risk of forming and keeping Cr(VI). Leathers were spiked with different concentrations up to 10 mg/kg of Cr(VI) and incubated at 80°C for 24 h prior to the ISO 17075-1:2017 extraction protocol.

All Cr(VI) was reduced by group B leathers, whereas all group A leather extracts contained detectable Cr(VI) that was dependent on the exact leather type and the amount initially spiked.

Pre-treatment of samples with supplemental Cr(VI) is a potential method for determining the reduction capabilities of leather, which are closely related to the risk of Cr(VI) formation. 10 mg/kg spiking unambiguously distinguished leathers with high and low risks of forming Cr(VI).