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The European Union offers guidelines to consumers on a complex Web site, but policy is left to its 25 member states. The official French agency for oceanic studies demonstrated that methyl mercury has permeated the world's oceans and that 5 percent of it ended up in fish. About half of the mercury occurs naturally, he said. Mercury, PCBs and dioxins comes from factories and other dumping. He urged governments to keep a closer watch.

Children of mothers who had eaten lots of fish during pregnancy had better communication and social skills at seven years old, the Lancet paper says. There are fears surrounding the possible toxic damage from eating fish during pregnancy. Researchers looked at social and communication skills as well as hand-eye co-ordination and total IQ in the children up to the age of eight years. Socioeconomic factors were taken into account as well as information on the rest of the women's diet. Eating less than 340g of fish and seafood a week was associated with a 48% increased risk of children being in the lowest group for verbal intelligence.

Seafood is the predominant source of omega-3 fatty acids, which are essential for optimum neural development. Low seafood consumption by mothers was more likely in homes with evidence of social disadvantage (high level of family adversity, crowding, low maternal education levels, not being a home owner, and being a single parent) and less than ideal lifestyles (smoker, low parenting scores, and not breastfeeding).