More than 40 per cent of fish species in east China's Jiangsu Province were found to be contaminated with heavy metals, according to a survey released by Jiangsu Environment Monitoring Centre (JEMC) this week.

Last year's investigation covered the province's major four freshwater lakes and offshore areas, reported the Nanjing-based Contemporary Post.

Cadmium, lead, mercury, chromium and zinc were the five kinds of heavy metals found in 41 per cent of species in the sample survey.

It revealed seashells, shellfish, and large-sized fish are the three types of species that suffer from the most severe contamination.

But Xia Yu, director of the fishery department with Jiangsu Oceanic and Fishery Administration, questioned the liability of the statistics released by JEMC, which is not specialized in fishery products.

According to Xia, surveys carried out by his department in 300 water areas over the past five years showed only 3 per cent of fish species tested were polluted with heavy metals.

"JEMC's research methods and sample selection might be different from us, so we obtain different results," said Xia.

Experts have now urged consumers to be cautious about eating too many of the products.

"The poisoning metals will invade the human body and cause severe problems if people eat them too much. Cadmium will cause kidney problems, and mercury can cause mental disorders," said Xia.

Jiangsu is one of the major fishery production provinces in the country, which has 600,000 hectares of freshwater fishery areas and 240,000 hectares of offshore fishery.

According to Xia, over-density of the pools, uses of chemical products, and poisonous industrial discharges are the main resources for the heavy metal pollution in the province.

Aside from several large-scale fishery factories, most fish vendors are small business owners with no professional skills and proper equipment, Xia added.

Residents in Jiangsu have raised concern at the results of the latest survey.

"Fishery products always form a large proportion of our diets. With such a proportion of heavy metal pollution, we really doubt now what is suitable to eat," said Wang Linlin, from Nanjing.

"We sometimes rely on the famous brands or the quality labels issued by quality inspection institutions. But it's a pity there are only a few brands in the fishery industry, and most of them are nameless products with their sources unclear."

There is only one authoritative fishery product quality examination centre in Jiangsu, which is far from the market demand, according to Xia.

The province produced 3.88 million tons of fishery products in 2005, estimated to have brought in a 70 billion yuan (US$8.8 billion) sales revenue from both home and overseas markets, according to Jiangsu Marine and Fishery Bureau.

(China Daily February 16, 2006)