In pictures: Nigeria's rubbish scavengers

When asked how often they swim in the water 9-year-old Sanusi says: “every day”.

A multitude of diseases are caught from sewage infected water like this.

The boys seem unconcerned. “We are used to it,” says Sanusi.

Nigeria has seen a massive increase in the numbers of children with polio in the last four years. The disease has spread to neighbouring countries thought to be polio-free.

Words and pictures: The BBC's Andrew Walker.