Tests have found that the mercury content in Asian shark fin exceeds safe levels, posing a health risk, especially to infants. San Francisco-based WildAid and Hong Kong's EarthCare, two animal protection and conservation NGOs, said yesterday that many of the fin samples they tested in Hong Kong, on the mainland, in Singapore, Taiwan and Thailand contained mercury concentrations that exceeded each place's safety standards. In Hong Kong, eight of 10 samples exceeded the Food Environmental Hygiene Department's limit of 0.5 parts per million (ppm). In terms of the proportion of over-contaminated samples found, only Taiwan fared worse. Like Hong Kong, eight of 10 samples contained dangerous levels, but that was according to a much higher limit of 2ppm. On the mainland, Thailand and Singapore, 16 of 62, one of three and three of 10 samples, respectively, exceeded their national contamination standards. WildAid conducted the survey at the beginning of the year. It sent small, whole fins purchased in each place to ALS Technichem, an international laboratory network, for mercury testing on random parts, then the tip and the base. 'The law is there, but it isn't being applied,' EarthCare director Andrea Ng Wai-yee said. Pregnant women, those preparing for pregnancy, breastfeeding mothers, young children and people with a high seafood content in their diets should avoid shark fin and large predatory fish, said WildAid executive director Peter Knights. Mercury in large doses 'can cause a decrease in intelligence quotient, lack of co-ordination, blindness and seizures in children' and personality changes, deafness, and memory loss in adults, according to a Centre for Food Safety risk assessment released last month. Pregnant or breastfeeding mothers can pass it to fetuses or infants through the placenta and breast milk. It is unclear how much shark fin consumers must ingest per month before they experience noticeable negative symptoms. The effects are 'gradual and very small', Mr Knights said, but mercury still poses a risk. 'We are not saying that people should stop eating shark fin, but mothers and women should be warned about it, like alcohol or cigarettes,' he said. Shark and other large predatory fish are at the top of the food chain and hence contain the accumulation of the mercury in the smaller fish they eat. Sharks live longer, collecting higher doses. The fin - 83 per cent protein, the material to which mercury binds - and especially the oldest tissue at its base contain higher levels of mercury, Mr Knights said. WildAid plans to ask the government to introduce warning labels on shark fin after University of Hong Kong researchers produce a paper on the survey results. The World Health Organisation's limit is higher, at 1.6ppm.