Just how polluted is the air we breathe in the UK? Other than the smog we can see it’s sometimes impossible to visualise what some call the ‘invisible killer’. Channel 4 News was shown new modelling which suggests the majority of UK households are in areas which break the World Health Organization's own guidelines on dangerous air pollution levels. In today’s episode, we speak to reporter Keme Nzerem who originally broke this story, about the politics of air pollution, why it’s damaging to our health and its links with poverty. Producer: Freya Pickford