Bright colours, dark secret

Last Updated: Saturday 04 July 2015

-- A gaily coloured dress might be a visual treat, but the dyes used in them might hide a dark secret. Studies at the Oregon Graduate Institute of Science and Technology in the US have revealed that treating azo dyes -- noxious effluents released by textile mills -- with hydroxyl ions may actually be doing more harm than good to the environment (Environmental Science and Technology, Vol 28, No 7).

Azo dyes constitute the largest class of dyes and pigments -- more than 10,000 types are currently in use and an estimated 10 to 15 per cent of them are released as an effluent. According to the study, the hydroxyl-ion treatment may lead to the production of benzene, a known carcinogen.

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