What is causing UK's pollution problems?

Parts of the UK could reach the highest level of air pollution on Friday, prompting health warnings.

Warm, still conditions are expected to combine with traffic fumes, pollution from the continent and Saharan dust from the south as it rises to level 10.

Much of the South East and eastern England will see high levels of pollution, although the problem is expected to be short-lived.

Air quality specialist Nigel Jenkins spoke to the BBC's Rebecca Williams in Brighton to explain what was causing the problematic pollution levels.