Reducing Carcinogens in Tanned Alligator Skins

Ioan I. Negulescu

Several Louisiana alligator products are at risk of missing out on the European market because of carcinogenic compounds used in the tanning process. European Union restrictions on hexavalent chromium in leather items affect many alligator skins tanned both in Louisiana and abroad, according to an analysis of these skins by researchers in the LSU AgCenter Department of Textiles, Apparel Design and Merchandising.

The Louisiana alligator industry is a multimillion-dollar business in Louisiana, with more than 300,000 wild and farm-raised American alligators (Alligator mississippiensis) harvested each year. Farm-raised alligators are the second-largest segment of the state’s aquaculture industry, worth $82 million in gross farm value in 2017, according to the LSU AgCenter Agricultural Summary. Combine other alligator-related businesses, and the state’s alligator industry is likely worth $100 million a year, the Louisiana Department of Wildlife and Fisheries Alligator Management Plan Annual Report estimates.

While Louisiana leads the nation in the production of alligator skins, less than 10 percent of all alligator skins produced in Louisiana have been tanned in recent years. Most skins are tanned in Europe or Asia.

Tanneries convert the raw, stiff, horny Louisiana alligator skins into supple, workable, long-lasting leather. The skins arrive salted from the suppliers, and the first process is beaming — cleaning, removing the salt and rehydrating the skins. Next, in a process called liming, the scales, nails, mucins, and natural greases and fats are removed. Then the skins are delimed and pickled in an acid bath to remove bone calcium so the alligator skin becomes more pliable. After pickling, the treatment with chromium salts will render the skin durable and resistant to the elements.

In the finishing operations the leather is re-tanned using vegetable-based products so that the tough skin from the initial tanning process is made supple. The leather is then dyed and shaved down to the thickness and weight needed for the application — clothing, boots or luggage, for example. Then the leather is finished with seasons and protective coats to feel and look nice.

The alligator skin’s fibrillary structure makes it fashionable for textile design applications. The alligator leather is ready to be delivered to the manufacturer, where it is turned into the finished goods, which products varying from earrings to sofas.

Chromium salts are used extensively in the leather industry as a tanning agent. Chromium may be present in the finished leather as trivalent or hexavalent cationic compounds. However, it has been proven that hexavalent chromium is toxic to humans and animals. Aquatic life is vulnerable if discharged wastewater from tanneries contains chromium. It can produce lung tumors when inhaled and readily induces skin sensitization. Hexavalent chromium is closely monitored by the U.S. Department of Health and Human Services, and in 2015, the European Union implemented restrictions on chromium-tanned leather on the European Union market. There could be negative consequences for the marketing of Louisiana alligator leather if tanned with chromium salts.

AgCenter researchers analyzed chromium levels in Louisiana alligator skins. The project used energy dispersive X-ray analysis to examine Louisiana alligator leather specimens tanned both in Louisiana tanneries and abroad in locations such as Singapore and brought back to the United States. These showed alarming amounts of chromium compounds present in the samples, proving that the alligator skins have been tanned with chromium salts. AgCenter researchers are assisting in identifying alternative chromium-free tanning procedures to aid the economic development of Louisiana’s alligator industry.

Ioan I. Negulescu is the Grace Drews Lehmann Professor in the LSU College of Agriculture Department of Textiles, Apparel and Merchandising.

(This article appears in the fall 2018 issue of Louisiana Agriculture.)

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An alligator skin at the Mark Staton Co. leatherworks in Lafayette Parish is about to be cut into sections that will be used to make a pair of boots. A dozen employees at the company near Broussard use wild and farm-raised alligator hides to make a wide variety of high-end products, including belts, wallets, cellphone cases, money clips, purses and even clothing. Photo by Bruce Schultz

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Stacked alligator skins at the Mark Staton Co. leatherworks in Lafayette Parish. Photo by Bruce Schultz

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Boots and alligator skins at the Mark Staton Co. leatherworks in Lafayette Parish. Photo by Bruce Schultz

12/13/2018 7:29:46 PM
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