A coroner's inquest starts in London on Monday to determine whether air pollution played a role in the death of a nine-year-old girl who lived near a busy road.
The hearing, which is due to last 10 days, could set a new legal precedent if it is found poor air quality contributed to the death of Ella Adoo-Kissi-Debrah.
Ella died in February 2013 from a severe asthma attack. She had previously suffered from nearly three years of repeated attacks related to the chronic illness and had been in hospital 30 times.
A first coroner's inquest in 2014 determined she died of acute respiratory failure brought on by severe asthma.
But the ruling was set aside in 2019 and a new investigation ordered after evidence about the risks of air pollution was highlighted in a 2018 report.
The second inquest will examine the levels of pollution the young girl was exposed to.
If it is found it contributed to her death, she would be the first person in the UK to have air pollution recognised as a cause of death.
Ella's mother, Rosamund Adoo-Kissi-Debrah, who will testify at the hearing, said it had been a "long hard fight" to get the second inquest.
"What I want is justice for Ella and for her to have on her death certificate the true cause of why she died," she said.
"The house became so much quieter after her death and I don't think we ever recovered from that. She was the life and soul of our home -– always playing music, always dancing."
The family lived less than 30 metres (98 feet) from the South Circular, a busy and regularly congested arterial road, in Lewisham, southeast London.
In 2018 air pollution expert Professor Stephen Holgate said there was a "striking link" between Ella's time in hospital and recorded peaks in levels of nitrogen dioxide (NO2) and particulate matter -- the most harmful air pollutants to human health.
- Global health issue -
The lawyer representing the family, Jocelyn Cockburn, said reaching the second inquest was a "significant achievement".
"Rosamund's account of Ella's struggle is very powerful and illustrates the human suffering behind the statistics," she said.
Coroner's inquests are held in England and Wales in the event of a sudden or unexplained death. They establish the causes and circumstances of deaths on the balance of probability.
They do not determine criminal or civil liability, guilt or blame but set out facts in the public interest.
According to figures from the Mayor of London, World Health Organization (WHO) recommended limits for air pollution are broken in 99 per cent of the British capital.
The WHO says air pollution kills some seven million people across the globe every year and nine out of 10 people breathe air that exceeds guideline limits on pollutants.
Low- and middle-income countries are worst affected and the problem contributes to premature deaths.
Last month, the executive director of the Clean Air Fund, Jane Burston, said children in London were "4.2 percent more likely to be hospitalised for asthma on days with high NO2 pollution".
Also in October, Mayor of London Sadiq Khan released figures showing improvements in air quality due to changes made since his election in 2016.
These measures have included the introduction of an "ultra low emission zone" which requires drivers of the most polluting vehicles to pay a daily tax when entering central London.