The cold, still air is causing a rise in air pollution in the capital and many other parts of the country The first “very high” pollution alert has been issued for London by mayor Sadiq Khan, under a new system for warning people about poor air quality. Warnings have been issued at bus stops, Tube stations and roadsides in the capital, and Mr Khan said everyone from the vulnerable to the physically fit may need to take protections to protect themselves from the “filthy air”.