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 November 10, 2014
Human-like fish that could be used to test China's water quality

 A fish with a genetic code similar to humans' may soon be used by the government to monitor water quality.

The tiny zebrafish, native to the River Ganges in eastern India, is prized by biologists because more than 90 per cent of its genetic code is identical to ours.

Embryonic zebrafish also develop important organs, such as the brain and heart, in the same way as human embryos, making the species an important subject for scientific research.

Though many countries use zebrafish to test new drugs, China could become the first to use it in the fight against water pollution, which threatens the health and livelihood of tens of millions of citizens.

Professor Chen Feng, biological researcher with the Chinese Academy of Sciences' South China Botanical Garden in Guangzhou, said she had been consulted by the Ministry of Environmental Protection, which has spent several years drafting a national standard water quality test using zebrafish.

"Today most technical issues have been solved. I think the standard will be launched soon," she said.

The method is straightforward. About 20 healthy zebrafish embryos are placed in various samples of water and observed with a microscope in a laboratory-controlled environment for between four and seven days.

If any embryo dies or mutates, the water is considered polluted and rated unsafe for drinking.

Using the zebrafish test, some drinking water sources regarded as safe by traditional tests could be found to be unsafe.

Traditional water quality tests use chemicals to trace the existence of pollutants such as heavy metals and pesticides. The central government's water pollutant test covers 106 pollutants. However, many chemical and biological pollutants are not covered by the test and to make matters worse, to save time and money, some authorities check for only about eight pollutants on a regular basis.

Zebrafish could provide a more reliable result than traditional tests because the animal's embryonic development is highly sensitive to pollutants that are not on the traditional check list.

"The zebrafish test is the most stringent test ever. Even the death or mutation of a single embryo can rate an entire water source unsafe for drinking," Chen said.

"We can see directly and vividly the impact of polluted water on the embryos. Some may die, some experience mutations in critical organs such as brain, heart or blood lines.

"If the fish can die or get sick, the same may happen to us."

China is facing one of the world's most serious water pollution crises, with the rapid development of mining and heavy industry over the past few decades polluting almost every major river and many underground water sources.

Though China's drinking water standard adheres to World Health Organisation guidelines, many pollutants in China are unique - and have unknown health impacts - owing to the country's large industrial sector.

Professor Cai Yaqi, water safety researcher with the CAS Research Centre for Eco-Environmental Sciences in Beijing, said one of the biggest challenges for the zebrafish test would be when it produced results that contradicted traditional tests.

He argued traditional methods had proved their worth and could still be trusted.

"Can we say that the old methods can no longer be trusted and used? Maybe not," he said.

"Each method has its advantages and limits.

"The best strategy is to find a way to combine the new and old methods in practice."