Last year Greenpeace toxics team went undercover to infiltrate factories that were releasing hazardous chemicals into China's waterways. Campaigner Zhang Kai looks back on the challenges and successes of the Detox campaign...We spent about one year carrying out the investigation on the textile plants, covering factories along the Yangtze River and in the Pearl River Delta...[T]wo weeks after we released our report, Puma came out with its promise to eliminate toxic substances from its supply chain...Since then Adidas, H&M, Nike and Li-Ning have all followed suit. This was one of Greenpeace's most complex investigations because the relationship between textile plants and the big brands was often opaque and it was vital to our campaign that we established the relationship clearly...We will continue to pressure the big clothing brands to commit to eliminating toxic chemicals...