The area has a large concentration of radon, with Brockwell Park falling right in the middle of it.
Most of Tooting is radioactive, including the ground under St George's Hospital and Tooting Primary School. This also stretches to Streatham Cemetery.
Peckham is also one of the worst affected areas, with Aylesham Shopping Centre and Peckham Bus Station in the perimeter.
Southwark Park, Surrey Quays Shopping Centre and Alfred Salter Primary School all sit on land with higher levels of radon.
The whole area, including the idyllic Greenwich Park, is affected.
This South London area is also affected, right along to Kidbrooke.
Parts of Eltham, near Royal Blackheath Golf Course, also have high levels of radioactivity.
The belt of radioactivity stretches from Greenwich to Charlton and through to Woolwich.