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Mercury Monitoring Finds High Levels

HONG KONG - Concerns are mounting about the levels of mercury found in alfonsino fish samples.

High level traces of the heavy metal have been found in three alfonsino fish samples - ranging from 609 to 1,370 micrograms per kilogram. This exceeds the legal 500 microgram limit. The samples were also found to contain a higher level of methylmercury, ranging from 509 micrograms per kilogram to 1,010, says the Centre for Food Safety study has found.


The centre's Community Medicine Consultant Dr Ho Yuk-yin said the study covered 280 fish samples, including 266 whole fish and 14 canned fish of 89 species found in the local market. It found that the Mercury levels in the samples ranged from three to 469 micrograms per kilogram. The levels of methylmercury detected ranged from three to 430.

The investigation also found comparatively higher average levels of methylmercury in yellowback seabream, yellowtail barracuda, and canned albacore tuna, ranging from 205 to 253 micrograms per kilogram.

The average level of methylmercury for different tuna fish species, including canned albacore, canned yellowfin, skipjack (canned and whole fish), also varied, ranging from 85 to 205 micrograms per kilogram. The highest average level was found in canned albacore. More study findings are available here.

HK Low on the Whole

Dr Ho said that the current study shows most of the fish available on the Hong Kong market have relatively low levels of total mercury and methylmercury, while a small proportion contain higher levels.

"The amounts of methylmercury relative to total mercury in different fish species vary considerably. For the high consumers among secondary school students, their estimated dietary exposure to methylmercury may exceed the provisional tolerable weekly intake, therefore possible health risk cannot be ruled out."

Mercury accumulates mainly in the organic form of methylmercury in the food chain, and particularly in fish. Concerns about methylmercury in food are related to its possible effects on the nervous system, particularly in developing foetuses.

Consumers should maintain a balanced diet. Moderate consumption of a variety of fish is recommended as fish contain many essential nutrients, such as omega-3 fatty acids and high-quality proteins. Pregnant women, women planning pregnancy and young children should avoid eating large predatory fish and those which may contain high levels of mercury.