Fish in the Yangtze River contain an "environmental hormone" that mimics the female hormone and can cause sexual prematurity and breast cancer, according to non-governmental organization members in four cities along the river.

Sample tests found the accumulation of two types of the toxic hormones nonylphenol and octylphenol in the livers of carp and catfish in Chongqing Municipality, Wuhan City, Ma'anshan City and Nanjing City, Xinhua news agency reported.

The two chemicals - usually used in food packaging, cleansing products and coating of aluminum tins - can enter the food chain through biological circulation and cause fertility problems such as reduced sperms and unnatural rise of estrogen level in end eaters, said a Greenpeace report released last week.

Tests results showed nonylphenol in a carp's body reaching up to 85 microgram per kilogram, while octylphenol in catfish reached 3.37 microgram per kilogram. The elements can be concentrated in successive stages of the food chain and harm the people's health.

Due to their hazardous effect in nature, the two compounds have been on a European Union priority list that took force in 2000, and been banned or limited from industrial use in western countries.

However, China currently has no specific law to control or supervise the production and release of the chemicals.

Beyond these two pollutants, heavy metal elements including lead, mercury and perfluorinated chemicals - potent compounds that can cause hormone disorders - were also found in the fish's organs, said the 24-page report.

With chemical companies opening up tens of thousands of factories and plants near its banks, the Yangtze River - China's longest river, and the world's third longest - swallowed nearly 21 billion tons of sewage, amounting to 30 percent of China's total waste water in 2008, the report said.

Nearly 70 percent of the sewage was released by chemical industries. This caused severe water pollution and posed a long-time threat to the country's fishery as well as the food safety as a whole, the report said.