Leather is produced by transforming raw animal hides through the processes of cleaning, tanning and dying. Although the leather industry uses animal hides which are byproducts of the food industry, the demand for particular kinds of leather products has resulted in the wide scale poaching of animals just for their skin. The demand for leather made from exotic skins has even resulted in hunting of certain animals like snakes and crocodiles to near extinction.
A major portion of leather is made of cattle skin. The most commonly used leather types are cow leather, sheep leather, buffalo leather and ox leather. The skin of animals like lamb, deer, elk, pig, kangaroo, ostrich, sting ray, hogs, goats, sheep, alligators, and yaks are also used to make leather.
Leather tanneries pose severe environmental problems by emitting highly polluted wastewater and different kinds of solid wastes and gases. Leather tanning requires massive amounts of energy and dangerous chemicals, including mineral salts, formaldehyde, coal-tar derivatives, and various oils, dyes, and finishes, some of which are cyanide-based. Most leather produced in the U.S. is chrome-tanned. Tannery effluent contains large amounts of pollutants, such as salt, lime sludge, sulfides, and acids.
Additionally, to raise the animals whose skin eventually becomes leather, huge amounts of feed crop, pastureland, water, and fossil fuels are required. Large numbers of trees are cleared to create pastureland. Animals on factory farms also produce large quantities of excrement. Farms which do not have waste treatment plants directly dump these wastes into the environment. The U.S. Environmental Protection Agency (EPA) has acknowledged the fact that livestock pollution is the greatest threat to our waterways.
People who work in and live near tanneries have a high risk of contacting cancer caused by exposure to toxic chemicals used to process and dye the leather. The chances of leukemia among such people are very high. Arsenic, a common tannery chemical, has also been associated with lung cancer in workers who are exposed to it on a regular basis.
In 1985 the Environmental Protection Agency established standards to control pretreatment of the liquid wastes that tanners discharge indirectly to publicly owned waste treatment facilities. All leather tanneries must mandatorily meet the Environmental Protection Agency waste standards. These standards apply to waste acidity and to wastes containing sulfides and chromium. All tanners discharging directly into waterways were required to operate with the EPA-approved National Discharge Elimination System (NDES) permits. In addition to the Environmental Protection Agency waste standards, in 1990, the Clean Air Act along with other strict federal standards have helped to curb the emission of volatile organic compounds into the air. This has encouraged leather tanneries to develop low-solvent or solvent-free finishing technologies.