London air pollution is poisoning my son, says campaigner

Father asks why politicians are not acting on child health crisis caused by illegal toxin levels

For David Smith, the final straw came as he was standing at the bus stop near his home in south London with his two-year-old son Ely.

He had become increasingly aware of the damage pollution was doing to young people's health since the birth of his two youngest children. And when the gridlocked traffic edged forward and a lorry pulled up a metre from Ely, something snapped.