Pregnant women, women planning pregnancy and children should avoid eating large predatory fish because they may contain high levels of mercury, the Centre for Food Safety (CFS) said yesterday.

Shark, swordfish, marlin, alfonsino and tuna (especially big eye and blue fin species) are examples of large predatory fish which may contain high levels of mercury.

Small fish, however, have little harm, according to the CFS.

Between April and August in 2007, the CFS analyzed 280 samples (89 species) of marine and freshwater fish, including local and imported fish species, as well as canned tuna.

The result revealed that the mercury levels in 277 samples were below the statutory limit of 500 micrograms per kilogram in Hong Kong.

As to the three remaining samples of beryx splendens, their mercury levels were above the legal 500 microgram limit.

Announcing the results yesterday, Ho Yuk-yin, consultant doctor of the CFS, said mercury is widely present in the environment. It accumulates mainly in the organic form of methylmercury in the food chain, particularly in fish.

Methymercury will affect the vision, hearing, muscle coordination and memory of adults, he said.

It will also affect the brain development of foetus, infants and young children, with developing foetus being the high-risk group.

Ho said 2 to 10 slices of sashimi a week would exceed the provisional tolerable weekly intake (PTWI) of methylmercury for pregnant women as advised by the Food and Agriculture Organization and World Health Organization.

Men are less susceptible to methylmercury. It is safe for them to consume no more than 20 slices per week.

In response to the CFS appeal to the fishing industry to obtain aquatic supplies from reliable sources, agriculture and fishery constituency legislator Wong Hung-kan said it is impossible for fishermen to ascertain the mercury levels in their catch.

(HK Edition 04/17/2008 page1)