More than 21,000 old sites may be releasing ‘forever chemicals’ into land often left as open space

• ‘It’s a poison and it’s killing us’: the hidden dangers of old UK landfills

Thousands of polluted landfills across England could be leaking toxic chemicals into the environment and harming people who live nearby, experts have warned.

A few decades ago, the method for getting rid of industrial and domestic waste was to stick it in a hole in the ground, cover it up and hope for the best. It was known as “dilute and disperse” and it assumed toxic substances would seep into the surrounding soils, air and water and become harmless.