Hong Kong Study Finds Some Mercury Levels of Concern in Fish Samples
Hong Kong's Centre for Food Safety on April 16 released findings of a study it conducted on mercury in fish, comparing the levels found to limits set for human consumption by the Food Adulteration (Metallic Contamination) Regulations: 0.5 ppm, or 500 micrograms per kilogram. Some fish that were tested were found to have far higher levels, raising concern that seconday schoolchildren may be ingesting too much mercury.
"Mercury is a metallic element present widely in the environment from natural sources and human activities. It accumulates mainly in the organic form of methylmercury (MeHg) in the food chain, particularly in fish. Concerns about MeHg in food are related to its possible effects on the nervous system, particularly in developing fetuses," the center's Consultant for Risk Assessment and Communication Dr. Ho Yuk-yin said.
CFS collected 280 fish samples, including 266 whole fish and 14 canned fish of 89 species found in the local market. Alfonsino, yellowback seabream, yellowtail barracuda, and canned albacore tuna had relatively high levels. Based on the levels detected in the study and data from the risk assessment study "Dietary Exposure to Mercury of Secondary School Students" in 2004, the center estimated dietary exposure to methylmercury of secondary school students was below the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives' Provisional Tolerable Weekly Intake (PTWI) of 1.6 microgram/kg of body weight for MeHg. "The current study shows that most of the fish available in the Hong Kong market have relatively low levels of total mercury and MeHg, while a small proportion contains higher levels. The amounts of MeHg relative to total mercury in different fish species vary considerably," Ho said. "For the high consumers among secondary school students, their estimated dietary exposure to methylmercury may exceed the PTWI, therefore the possible health risk cannot be ruled out."
CFS advised consumers to maintain a balanced diet and consume fish in noderation. Pregnant women, women planning pregnancy, and young children should avoid eating large predatory fish and those that may contain high levels of mercury, such as shark, swordfish, marlin, alfonsino, and tuna, especially the bigeye and bluefin species, the center advised.