The toxic legacy of Britain's industrial heritage lies festering beneath our feet in 20 thousand former landfill sites. But now Government has ended the system of grants to local authorities to help pay for their clean up, and developers are moving in to build housing. How safe are these places, and should people be concerned about living on top of them? Many of these sites were commissioned long before safety and environmental regulations were introduced so nobody knows what's buried underground and what problems it might create in the future. Families whose homes were built right next door to old landfill sites tell the programme their lives have been blighted by health issues. File on 4 has seen new research commissioned by the Environment Agency which reveals how erosion is threatening hundreds of toxic dumps along our coastline that could leach chemicals and other harmful substances onto our beaches and into the sea.