Eating seafood that contains mercury can affect the brain development of children in their adolescence, according to a study of people in the Faroe Islands.

The study contradicts the opinion of researchers who think these compounds are toxic only to babies as they develop in the womb, and that older children are unlikely to suffer developmental problems from the poison.

The group previously found that the children, when 7 years of age, had a slower transmission of electrical signals along a particular circuit in their brain than normal. Now that the children are 14 years old, after a continued diet of fish and whale meat, the researchers find that this disruption is even worse. They also found evidence that mercury exposure is linked to subtle difficulties in controlling blood pressure.

Mercury leaches into water from natural sources, such as eroding rocks, and from industrial pollution such as coal-fired power stations and incinerators.