TOXICOLOGY
The current Report on Carcinogens (RoC), published by the U.S. National Toxicology Program (NTP), classifies formaldehyde gas as a "Reasonably Anticipated Human Carcinogen".
SOURCES IN LEATHER (1) Phenol sulfone and naphthalene based resins often contain some residual free formaldehyde that can vary in concentration and possibly cause adverse skin reactions LIMITS TEST METHOD In addition to formaldehyde, leather often also contains acetaldehyde, the concentration of which is limited the automotive manufacturers and some eco-labels. Acetaldehyde is almost ubiquitous in the environment, and may be present in leather due to the use of natural fatliquoring oils and/or vegetable extracts for retanning. A third aldehyde, glutaraldehyde, can impart perspiration resistance and washability when used as a retanning agent. The above test method has been found to be equally valid for these additional aldehydes.
Formaldehyde is found in most leather at various concentrations due to its use in the synthesis of retanning agents and process chemical preservatives. Formaldehyde is used by chemical manufacturers to polymerize the synthetic retanning agents (“syntans”) that tanners require to impart the performance and aesthetic properties demanded of modern high performance leather (“feel”, water-resistance, etc.):
The U.S. has not implemented a regulatory ban or limit on the presence of formaldehyde in leather, but some other countries and most retailers – particularly the brand names – have implemented their own specifications that range from as high as 300 ppm to as low as 10 ppm.
Leather manufacturers should determine what limit is being placed on the leather, either by the product manufacturer or by the retailer, and then allow us to test their leather on a regular basis to establish compliance.
As with all test specifications, some of the responsibility of ensuring complience lies higher up in the supply chain. Leather and leather product buyers should check that the tanner has a working compliance program by regularly submitting test samples to us on an independant basis.
We use the internationally recognized ISO test method to measure the concentration of formaldehyde in leather, and have participated successfully in a recent international inter-laboratory method validation trial organized by the IULTCS (International Union of Leather Technologists and Chemists Societies). In this method, the formaldehyde is extracted from the sample, reacted with 2,4-dinitrophenylhydrazine (2,4-DNPH), and then quantified using high performance liquid chromatography (HPLC) with diode array detector as shown below.
Alternatively, aldehydes emitted from leather in the gaseous form are first captured using special collection tubes, and then analysed according to the procedures specified by TOYOTA, NISSAN and HONDA.
Above - Cietta Fambrough using HPLC to measure the concentration of formaldehyde and acetaldhyde emitted from automotive upholstery leather.
