A nine-year-old girl who suffered from chronic asthma was "living on a knife edge" in the months before her death, a medical expert has said.

Ella Kissi-Debrah died in February 2013 after suffering numerous seizures and making almost 30 visits to hospital with breathing problems over the previous three years.

An inquest at Southwark Coroner's Court is investigating whether dangerous levels of air pollution in the London Borough of Lewisham, where Ella lived with her family, may have contributed to her death.

Professor Sir Stephen Holgate, professor of Immunopharmacology at the University of Southampton, told the inquest that Ella's "exceptionally rare" condition, in combination with her surroundings, had put her at "exquisite" risk.

"I've used the term 'Ella was living on a knife edge'. What that really means is that ... a very small change can lead to a dramatic event," he said.

Sir Stephen said that a "hyper-secretion" of mucus in Ella's lungs induced prolonged coughing fits which had worsened in the winter months of 2012.

"During these winter months, when air pollution was getting worse in her neighbourhood... this is when she would be experiencing her worse exposures," he said.

"I believe that is why (Ella's condition) was most accentuated during that time, whereas in the summer months where the air pollution levels as a whole drop her airway is able to get itself together again.

"Clearly she had a strong genetic susceptibility second to almost none."

News Shopper:

A 2018 report written by Sir Stephen found that the levels of pollution at the Catford monitoring station, one mile from Ella's home, "consistently" exceeded lawful EU limits over the three years prior to her death.

Sir Stephen said it was "almost certain" that Ella's asthma would have been "substantially less severe" if the concentration of pollution in the local area had been within the limits.

"If she had been moved out of the area into an area which was much less polluted, based on my evaluation... I would suggest that she would have improved," he said.

Sir Stephen added that air pollution had been known as an exacerbating factor in asthmatics, including children, "for at least 40 years, if not longer".

Professor Paul Wilkinson, professor of environmental epidemiology at the London School of Tropical Diseases said that Ella was likely to have been exposed to above average levels of pollution "even for London", due to her home's proximity to the busy south circular road.

The inquest heard that between 28,000 to 36,000 deaths each year in the UK were thought to have been contributed to by air pollution.

Sir Stephen said the issue of air pollution needed to be "on the agenda" and that the public should be given the ability to measure levels themselves.

"I think information about local air quality, empowering individuals, would be tremendously helpful," he said.

Sir Stephen paid tribute to Ella as an "extraordinary girl" and praised her "amazing" mother Rosamund Kissi-Debrah for her resilience following the tragedy.

Dr Andy Whittamore, clinical lead at Asthma UK and the British Lung Foundation and practising GP, said it was "crucial" that safeguards were put in place to avoid similar deaths in future.

"Clinicians and local authorities must work together to alert the public of the dangers of air pollution by highlighting places and times when air quality is poor, so they can take action to protect themselves," he said.

"Air pollution may be invisible, but it persistently irritates the airways, meaning that people get more symptoms, need stronger doses of medication to keep them well and are more likely to have asthma attacks or symptom flare-ups - which can be fatal."

The inquest is expected to conclude on Friday.