One of Sadiq Khan's many promises in his manifesto was to be the greenest Mayor ever.
Following his historic election win, the campaign group Friends of the Earth want to ensure he now sticks to his pledge.
They're calling on Mr Khan to make cutting pollution a priority.
Sophie Neuburg, a Friends of the Earth campaigner said:
"Many of Sadiq Khan's policies are stronger than the Government's.
He's made some good pledges on air pollution, but we would like him to go further and take significant steps to address the illegally polluted air in London."