Research leader at the University of Northampton’s Institute for Creative Leather Technologies (ICLT), Dr Will Wise, has published an update on the work he and his colleagues have carried out on chromium VI. He said the leather industry’s ongoing debate about chromium VI took on increased significance earlier this year following a proposal from European Chemicals Agency (ECHA) in April that the allowable limit for chromium VI should go from 3 ppm at the moment to 1 ppm to bring the leather industry in line with the textile industry. Dr Wise has pointed out that, while the textile industry uses little chromium, the leather industry faces having to try to detect 1 ppm of chromium VI in a background of 20,000-40,000 ppm of chromium III.

A project to review the current status of chromium (VI) analysis in leather began at ICLT in early 2016, jointly funded by the Worshipful Company of Leathersellers and Leather UK. The focus of this project narrowed when the project team, Dr Stefan Davies and Dr Wise, identified possible sources of error in the colorimetric method (ISO 17075-1) used for determining chromium (VI) levels. According to Dr Wise, the standard method itself provides “rigorous evidence” that lowering the limit below 3 ppm would render the colorimetric method meaningless.

The team’s work also suggests that the supposedly more accurate chromatographic method is also incapable of testing to a limit as low as 1 ppm, despite the analytical technique having greater sensitivity. The team at the ICLT has identified several ways to improve the methodology, which could reduce the discrepancies observed between samples and test houses. For example, tighter restrictions on timings are important in limiting the possibility of premature testing before a complete reaction has taken place. Also, specifying a shelf-life for analytical solutions minimises precipitation and oxidation in solutions that could alter results. It also proposes that when it’s less than certain that a sample has passed or failed, it should be possible to record ‘inconclusive’ as the test result. Other standard methods, for example BS EN 62321-7-1:2015, allow this.

All the proposed changes will be put to the European Committee for Standardization (CEN) for inclusion in future updates of the standard. If adopted, these changes will improve the reliability of results but are unlikely to allow the colorimetric method to remain as a viable method for measuring the lower 1 ppm limit.

ICLT will submit a response to a consultation on the proposed legislation changes, explaining “the fundamental inability” of the current test methods to reach such low levels of detection reliably. This submission will be supported by Leather UK, which will separately examine the impact on the leather manufacturing industry.

All parties have until December 19 to submit a response of their own to the proposed changes.