Hi everyone! I broke the momentum of the usual posts with two reflection posts last week, we will continue with posts for Chapter 2 this week and this post discusses the impact of textile dyes on the environment. When we look at the negative impacts of the fast fashion industry on the environment, it is easy to think about air, cotton or packaging pollution. However, the more inconspicuous impacts of the industry are caused by the dyeing processes. Dyes are complex organic compounds that are used in many industrial processes including textile, cosmetic, leather and rubber industries. In meeting the demand for dyes, about 1.6 million tons of dyes are produced yearly and about 15% of this is disposed of as wastewater (Varghese et al., 2019).
In this post, I will discuss how dyes contribute to environmental pollution in 3 main ways:
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Intensive water use
Dyeing processes require a large volume of water – as much as 37 MILLION Olympic swimming pools, or 93 billion cubic metres of water every year. For a pair of jeans, 7.5 cubic metres of water is needed from growing raw cotton to manufacturing the finished product. Fabrics are repeatedly dyed with synthetic indigo dye to obtain the blue denim colour. After dyeing, the fabric is treated and washed again with even more water and chemicals (Regan, 2020).
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Water and groundwater pollution
After these dyeing processes, factories may dump chemical-laden wastewaters into nearby water bodies such as rivers and lakes. This can be referred to as toxic sludge. Not all of the substances used in the factories are hazardous, but the World Bank has identified more than 70 toxic substances in textile dyes (Regan, 2020). Once these toxic substances have entered the water bodies, the molecules will continue to persist due to the complex molecular structures of dyes that resist natural degradation. For example, when methylene blue dye is discharged as waste, it produces a dark colour at high concentrations. The dye then blocks sunlight from penetrating into the water and affects the photosynthetic activity of submerged aquatic plants (Wong et al., 2018). For bright reds and yellows, synthetic nitrogen-based dyes such as azo dyes are commonly used but these dyes degrade under certain conditions to release aromatic amines. These are the same type of chemical compounds found in pesticides and can increase the risk of cancer (Regan, 2020). Azo dyes are also water-soluble, and this means that they are easily absorbed by the skin and can cause skin and eye irritation.
Environmentalists found that many water bodies in China, one of the largest clothes manufacturers in the world, are severely polluted by toxic sludge. The photo above shows Jian River in China’s Henan province that turned red after a red dye was dumped in. In fact, more than 70% of the rivers in China are polluted and with the contamination of groundwater, some communities cannot access safe drinking water for domestic consumption (Ranson, 2020).
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Chemicals and heavy metals contamination
Dyeing processes use a cocktail of toxic chemicals and heavy metals. Research by Greenpeace found 5 heavy metals in most of the 21 samples collected from rivers in Xintang, the denim capital of China. In particular, lead, chromium, cadmium, copper and nickel are commonly used. Chromium compounds have been used as catalysts in the dyeing process, while lead compounds are used in pigments and oxidisers. These heavy metals are carcinogenic and chronic exposure from contaminated water bodies or groundwater may affect the lungs and respiratory system.
In the next post, we will explore some technological improvements and innovations to ensure that the colours in our wardrobe are more sustainable. Until then, let’s keep running away from fast fashion!
Cheers,
Chermaine
References
Ranson, B. (2020). The true cost of colour: The impact of textile dyes on water systems. Fashion Revolution. https://www.fashionrevolution.org/the-true-cost-of-colour-the-impact-of-textile-dyes-on-water-systems/
Regan, H. (2020). Asian rivers are turning black. And our colorful closets are to blame. CNN. https://www.cnn.com/style/article/dyeing-pollution-fashion-intl-hnk-dst-sept/index.html
Varghese, A. G., Paul, S. A., & Latha, M. S. (2019). Remediation of heavy metals and dyes from wastewater using cellulose-based adsorbents. Environmental Chemistry Letters, 17(2), 867–877. https://doi.org/10.1007/s10311-018-00843-z
Wong, S., Yac’cob, N. A. N., Ngadi, N., Hassan, O., & Inuwa, I. M. (2018). From pollutant to solution of wastewater pollution: Synthesis of activated carbon from textile sludge for dye adsorption. Chinese Journal of Chemical Engineering, 26(4), 870–878. https://doi.org/10.1016/j.cjche.2017.07.015