The leather industry is among the top 10 most polluting industries, due to the heavy use of chemicals and a high water footprint. The leather tanning process involves the transformation of the animal skin or hide into leather through the use of different chemicals, including chromium sulfate which is considered one of the most effective and efficient tanning agents. Untreated effluents from tanning industries contain a high concentration of these chromium compounds along with other contaminants including dyes, chlorides, dissolved solids, nitrogen, and suspended solids. These untreated effluents can end up in soils and water bodies near tanneries.
The use of tannery effluents for irrigation in farmlands is also a common practice that can lead to heavy metals leaching into the soil. In Kanpur, Uttar Pradesh, also known as the "leather city" where the largest tanneries in India are located, tannery effluents are used for irrigation due to their high nutrient content for plant growth. Additionally, many small-scale tanneries release their effluent into surface water bodies without pre-treatment of effluent as it is expensive. Dotaniya et al (2017) found that soil and groundwater had a significant build-up of heavy metals, from chromium to zinc from around 50 years of effluent use. Soil samples were heavy to extremely polluted by chromium and unpolluted to moderately polluted with other heavy metals.
Higher chromium concentrations in the soil affect root and shoot growth, germination, and crop yield. The same study found that soil and water pollution had contributed to a reduction of crop yield in agricultural areas in Kanpur by 25-40%. The tanning process can also oxidize trivalent chromium (Cr +3) into a significantly more toxic hexavalent state (Cr +6). A study in Dhaka, Bangladesh also found an accumulation of trivalent chromium around the waste disposal area surrounding a tannery plant, and chromium was found to bind to clay minerals in the soil. The effect of heavy metal soil pollution poses dangerous health risks to human health, both to industrial workers and those consuming foods from irrigated fields. In Kanpur, rampant soil and water pollution have led to an array of health issues resulting from the prolonged use of effluents, including respiratory disease, renal failure and dermal problems.
The leather industry is of substantial economic importance to countries like China, India, Thailand, Indonesia, Pakistan, and Bangladesh. Among the top importers of leather are the United States, Germany, and other European countries. Leather is usually considered a luxury product that has always been in high demand, although it did fall sharply during the pandemic and has been falling globally, as artificial leather is cheaper. Environmental consciousness among the global community is also increasing, with more people adopting an animal-cruelty-free lifestyle. Thus, there has been increasing interest in innovating environmentally friendly alternatives to leather-like those made of mushrooms, which has been touted as a sustainability gamechanger. For example, an Indonesia-based startup has innovated "Mycotech", its own mushroom leather technology inspired by tempeh, which has already been used to develop bags, shoes, and other accessories.
There have also been initiatives to make the leather industry more sustainable. Solidaridad, an international civil society organization is promoting the use of algae to remediate water polluted from the tanneries, which has shown promising results in improving crop yields when treated effluents are used for irrigation. Many employed in the leather industry in developing countries are from vulnerable and minority communities. In India, this includes Dalits (lower caste) and Muslims (a religious minority). They are often subjected to unfair treatment or violence, due to political and social reasons, and are also faced with an uncertain future with the decline of the leather market as aforementioned. Therefore, a just and sustainable transition for the leather industry is needed.
References
Bhavya, K. S., P, R., A, J. S., Samrot, A. V., Thevarkattil, P., Javad, M., & V.V.S.S, A. (2019). LEATHER PROCESSING, ITS EFFECTS ON ENVIRONMENT AND ALTERNATIVES OF CHROME TANNING. INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING & TECHNOLOGY, 10(6). https://doi.org/10.34218/IJARET.10.6.2019.009
Chandra Kashyap, G., Sharma, S. K., & Singh, S. K. (2021). Prevalence and predictors of asthma, tuberculosis and chronic bronchitis among male tannery workers: A study of Kanpur City, India. Clinical Epidemiology and Global Health, 9, 71–77. https://doi.org/10.1016/j.cegh.2020.07.002
Dotaniya, M. L., Meena, V. D., Rajendiran, S., Coumar, M. V., Saha, J. K., Kundu, S., & Patra, A. K. (2017). Geo-Accumulation Indices of Heavy Metals in Soil and Groundwater of Kanpur, India Under Long Term Irrigation of Tannery Effluent. Bulletin of Environmental Contamination and Toxicology, 98(5), 706–711. https://doi.org/10.1007/s00128-016-1983-4
FAO and UNEP. (2021). Global assessment of soil pollution: Report. https://doi.org/10.4060/cb4894en
Mishra, U. (2017, May 22). Using tannery waste in fields turning soil toxic: study. Down To Earth. https://www.downtoearth.org.in/news/waste/using-tannery-waste-in-fields-adding-toxics-to-soil-study-57912
Sen, J. (2016, April 12). The Unmaking of Kanpur’s Leather Industry. The Wire. Retrieved February 16, 2022, from https://thewire.in/uncategorised/the-unmaking-of-kanpurs-leather-industry
Solidaridad. (2019, January 08). India steps up to make leather production more sustainable. Solidaridad Network. Retrieved February 16, 2022, from https://www.solidaridadnetwork.org/story/india-steps-up-to-make-leather-production-more-sustainable/