Fish Eggs Impaired By Beijing Sewage Water

January 5, 2008

Release from: Satoshi Saeki
Daily Yomiuri Online

BEIJING - An experiment in which killifish eggs were incubated in Beijing sewage water resulted in 80 percent of the fry being stillborn due to a reduced incubation period, or being born with abnormalities such as deformed tails, it has been learned.

Endocrine disrupters--substances that act like hormones and cause adverse biological effects in animals--in the sewage water are believed to have caused the abnormalities in the joint Sino-Japanese experiment.

The results, announced Thursday, highlight latent anxiety over the environment in China, a country that is trying to clean up its act prior to the Beijing Olympics in August.

The experiment was conducted as part of research by Mitsubishi Electric Corp., Peking University and other institutions, over two years from 2005.

The objective of the research is to solve the Chinese capital's water shortage by introducing an advanced sewage treatment that utilizes ozone--a technology that Mitsubishi possesses.

According to Mitsubishi, the experiment utilized killifish eggs, which are believed to be highly sensitive to pollution, by immersing them in Beijing sewage water during their incubation period.

The eggs' assumed hatching rate of 90 percent was reduced to between 30 percent and 40 percent; the normal hatching period of 10 days was cut to between five and seven days; and deformities such as bent tail tips were observed.

As few as 20 percent of the fish hatched normally.

A substance in the water that has a similar effect to retonic acid is believed to have caused the abnormalities.

Retonic acid is formed when vitamin A is absorbed or decomposed and can broadly be described as a type of endocrine disrupter. Retonic acid cannot be eliminated by the current sewage process of activated sludge treatment, but it and other substances with the same effect can be decomposed with treatment that utilizes ozone.

Examination of six major sewage treatment works in Beijing revealed that five of the plants tested positive for substances with effects similar to retonic acid. Sewage water at all five sites is reportedly mixed with liquid waste from factories.

Among other uses, retonic acid is utilized to remove wrinkles in cosmetic surgery. But reports have shown that excessive intake of the acid can cause deformities in animals, such as frogs being born with three hind legs.