At Greenpeace we believe in bearing witness to environmental crimes. In shining a global spotlight on injustice. In the positivity of action.

A year ago we set out to investigate the discharges flowing into the Qiantang River in coastal Zhejiang Province. This is an area where more than one third of China's dyeing and printing takes place in an attempt to quench the insatiable global thirst for fast-fashion. Big global brands, such as Calvin Klein, were found to have links to suppliers operating in the region, many of whom take advantage of communal waste water treatment plants to conceal and mix their dirty pollution together with the waste water coming from other production facilities. And when we tested the water coming out of these big industrial areas, we found a real cocktail of chemicals that contained both hormone disrupting and cancer causing substances.

We decided enough was enough. The world needed to see the environmental destruction that was being caused in the name of "fashion". And who better to bear witness to the crime than a bunch of second-hand mannequins who's CVs included wearing the same type of clothes that are being manufactured inside the facilities responsible for this pollution?

Setting them up wasn't easy. The area around the "black swirl" is tidal, and the flow of pollution coming from the underwater pipe is unrelenting. Wearing protective gear the team entered the hot, smelly, dirty water and using a combination of superglue, iron plates and wire netting we were able to secure the mannequins down.

We then attached webcams to several of them, and when our press conference kicked off in Beijing we were able to stream live footage from the scene of the environmental crime directly to a room full of shocked journalists.

Toxic water pollution is not a new story in China, but the sheer scale of the pollution in this area is shocking, even for a team that has spent many years working on the issue. That is why we not only bear witness to these environmental crimes, but also actively work to change the situation on-the-ground at the source of the pollution, and why we campaign on the big fashion brands, that are hidden behind a smokescreen of opaque practices, to take responsibility for the pollution caused when manufacturing their clothes. Already things are starting to change for the better. Eleven international brands including Zara, Esprit and Levi's have committed to work with their suppliers to eliminate hazardous chemicals from their production and products, in response to the global Detox campaign. Better yet, many of these brands have also committed to publish data about the discharges coming from their supplier's facilities as soon as 2013, allowing their customers and those most directly affected by the pollution to see exactly what is being released into our public waterways.

Actions speak louder than words.

As with the silent witnesses who braved the terrible conditions to shine a light on the pollution many had wanted to conceal – we will of course judge these brands by the concrete actions they take, not by the paper promises they give. But these commitments, along with the transparent publication of discharge data, are the crucial first steps on the road to a toxic-free future.

After all, as more and more brands sign up to Detox, and as hundreds of thousands of people around the globe join our campaign calling for fashion without pollution, the message to the textile industry only gets clearer and clearer.

The era of toxic fashion will soon be over, and any brand stupid enough to ignore this new reality risks being swept away forever in the toxic tide.

Muyi Yang is based in Beijing and has been involved in the Detox campaign since it began in 2011: challenging some of the world's most popular clothing brands to work with their suppliers and eliminate all releases of hazardous chemicals into our water.