A Zhejiang entrepreneur has offered 200,000 yuan ($32,000) to any local environmental protection official willing to swim in a filthy local river for more than 20 minutes.

Jin Zengmin, chairman of Hangzhou's Maoyuanchang Eyeglass Ltd Co, said he "dared" the city's environmental chief to jump into the un-named river, which flows through the Xianjiang neighborhood of Rui'an city.

Referring to it as "the river I used to swim in when I was little" and the same used by his mother to wash the family's clothes, he claimed that residents have suffered from unusually high cancer rates as a result of pollutants in the water.

According to Jin there are about 1,000 rubber shoe manufacturing plants operating in the neighborhood, the highest concentration in China, many of whom dump waste directly into the river.

Zhejiang Online reported that Xu Yihua, the head of Rui'an Feiyun Environmental Management Administration, who is now in charge of an investigation into the river, said the pollution was not as bad as Jin claimed.

"Jin's photos only show a small section but the overall water quality (of the river) is relatively good," Xu was quoted as saying.

Jin responded to Xu's claim that he would also offer him 200,000 yuan if he dared to even step into the river.

"If Xu thinks the water is clean, I dare him to walk in it, even 20 meters," said Jin, who now lives in Hangzhou.

Chi Renfu, an official with Rui'an Environmental Protection Bureau, told China Daily that the bureau chief Bao Zhenming had inspected the site.

"Household garbage including plastic takeaway food packages and used Chinese New Year lanterns were everywhere.

"It's not the chemical waste that polluted the river as Jin stated, it's more household refuse dumped by local residents," said Chi, adding that poor local environmental awareness had also led to the problems.