A coroner in London is investigating the death of a nine-year-old who died after repeated asthma attacks.
A 2014 inquest had ruled that Ella Adoo-Kissi-Debrah died of acute respiratory failure.
But this was quashed in 2019 after a report found there may be a link between her death and the quality of air near her home.
Adoo-Kissi-Debrah lived 30 metres from the often-congested South Circular Road in Lewisham, southeast London. A new two-week inquest will attempt to identify whether this was a factor in her death.
It will also look at what, if any, steps were taken to control the quality of air. And it will examine if the public were informed about levels of pollution and what steps they could take to reduce exposure.
Solicitors representing the family say that if the coroner rules that poor air quality directly caused her death, Adoo-Kissi-Debrah could be the first person in the UK - and possibly the world - to have air pollution listed on her death certificate as the cause.