Leather-Tanning with Chromium

Chrome is used in about 90% of leather tanning operations worldwide, and its use has long been a concern in regards to its potential environmental impact.  Trivalent chromium, the form most commonly used in tanning, is naturally occurring and essential for good health.  Under certain conditions, however, trivalent chromium will oxidize and turn into hexavalent chromium.  Hexavalent chromium is carcinogenic and can pose severe health concerns for humans, animals, and the environment.

While there are other methods of tanning, such as vegetable tanning, chromium is used most of all because it produces leather that is softer and suppler than the other methods, and doesn’t discolor or lose its shape as much in water. Chromium-tanned hides also pick up more color during the dying process. For more information on how leather is made, and my source for this chromium-tanning information, click here.

Acute effects of hexavalent chromium exposure include irritation to the mouth, throat, lungs, and nose (if inhaled); skin irritation and allergic reactions (if the skin was exposed); and digestive problems, kidney damage, or liver damage (if consumed contaminated food or water).  Long-term effects of chromium exposure include lung cancer, lung irritation resulting in asthma, liver or kidney damage, impaired immune system, and reproductive problems.  For a chromium fact sheet provided by the Wisconsin Department of Health Services, and my source for the health effects of chromium, click here.

Many tanneries worldwide have strict regulations for purifying water used during the tanning process of any residues or pollutants, but a very large portion of the tanning industry operates from developing countries without such strict regulations, especially in regards to wastewater. As you can see from the chart below, the regions most impacted by chromium pollution from tannery operations is South Asia, Central America, South America, and Africa.

2011 - Population estimates are preliminary and are based on an ongoing global assessment of known polluted sites.

In addition to potentially toxic wastewater, some tanneries also produce large amounts of solid waste that contains chromium.  In some areas, these pollutants are the reason that all nearby surface and groundwater systems are contaminated with severely high levels of chromium.

For more information regarding chromium pollution deriving from tannery operations, and my source for these images and accompanying data, click here.