Polluted, poisonous and immune to popular efforts to enforce a clean-up: Tai Lake is a metaphor for the state of China's politics The plain-clothes police are always there, watching Xu Jiehua. When she goes out, two of them follow by motorcycle. Sometimes an unmarked car joins them, tailing her closely on the narrow road winding past the factories and wheat fields around her village. Ms Xu is used to the attention. Her husband, Wu Lihong, was arrested in April last year and sentenced four months later to three years in prison for fraud and blackmail. For her, the police harassment is proof that the charges were false, and that Mr Wu's only crime was to anger local officials with his tireless campaigning against pollution around nearby Tai Lake, China's third-biggest freshwater body. It is also a warning that she too should keep quiet. Last year nature appeared to vindicate Mr Wu. Soon after his arrest, the lake was choked by toxic algae fed by the phosphates from the human and industrial waste that had been poured into the water and its tributaries. For more than a week, the stinking growth disrupted the water supply of 2m people living on its shores. It was one of China's biggest environmental scandals since the Communist Party came to power. In Wuxi, the city closest to Mr Wu's home in Fenshui village, residents queued to buy bottled water. The Yangzi River was diverted to flush the algae out. Amid an internet-fuelled uproar, officials promised to close down polluting factories and clean up an area once legendary for its beauty. But in late March blue-green blooms were again found along the southern shore. Such growths are rare so early in the year. Officials admit that despite their clean-up efforts the water remains at the lowest grade in China's water-quality scale, unfit for human contact, and that another "big bloom" is possible this year. A repeat of the algae catastrophe on Tai Lake would be a huge embarrassment to both local officials and the central government. As they look nervously at protests around the country fuelled by an upsurge of anti-Western nationalism, the authorities are ever mindful that the anger could readily turn upon them too. Nationalist fervour may be helping to divert public attention away from the party's mishandling of Tibet