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Many Nigerians 'at risk' of lead poisoning

7 February 2012 Last updated at 22:21 GMT

Some 400 children have been killed and many more are at risk after the world's worst lead poisoning epidemic in northern Nigeria.

The Human Rights Watch has confirmed that despite warnings two years ago, dangerous gold mining in the area is expanding, as attempts to clean up villages have stalled.

The BBC's Mark Lobel reports.