Denim is still being sand-blasted by hand in Bangladesh to satisfy the fashion trade despite the dangers it poses to the health of workers.

A report entitled “Deadly Denim”, published on Thursday by the Swiss non-governmental organisation, the Berne Declaration, and the Clean Clothes Campaign (CCC), says that on-site inspections show that suppliers of some major clothes brands are carrying on with the practice despite undertakings from the companies to put an end to it.

The procedure can cause workers to develop the incurable lung disease silicosis, which often proves fatal. Even when the process is carried out mechanically, the workers are exposed to silicone dust.

The report says almost half the 200 million pairs of jeans exported from Bangladesh annually are sand-blasted, and that Bangladesh has over 2,000 sand-blasters producing garments for export.

Sand-blasting is used to give jeans a "worn" look, popular with western consumers.

The study interviewed workers in a total of nine factories. It says well over 45 per cent of the interviewees recognised the logos of brands including H&M, Levi’s, C&A, D&G, Esprit, Lee, Zara and Diesel and said they were being manufactured in their factories.

The report admits that “buyer bans” have some impact on the use of sand-blasting, but “the impact of ban has been patchy, poorly monitored and widely circumvented, at least in the majority of factories we investigated”.

It said manual sand-blasting often takes place at night to avoid detection by audits.

The Berne Declaration and the CCC are calling on all the companies involved to do more to put an end to the practice, for example by changing the design of their jeans and imposing less tight deadlines.

They say the report shows a voluntary ban is not enough: governments worldwide must enforce national bans, and all brands should support them in this.

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