London has had dramatic improvements in its air quality since the coronavirus lockdown, with dangerous emissions at some of the capital’s busiest roads and junctions falling by almost 50%. Figures released by the London mayor, Sadiq Khan, show that anti-pollution measures introduced from 2017 had already led to a 35% drop across the capital of the harmful gas nitrogen dioxide, NO2 – rising to a 44% reduction inside central London’s ultra-low emissions zone (ULEZ). In the last four weeks of lockdown there have been further big reductions, with NO2 falling by a further 27% across London, and by almost half at some of the worst pollution hotspots. Khan welcomed the decline in toxic air, but said that once the lockdown was over it was essential that the efforts to improve London’s toxic air continued. “This cleaner air should not just be temporary. So once the current emergency has passed and we start to recover, our challenge will be to eradicate air pollution permanently and ensure the gains we’ve made through policies such as ULEZ continue.” Although the figures show a big reduction in NO2, particulate pollution, which comes largely from domestic wood burning and agriculture, and which is very harmful to human health, remains a severe threat in London. Elizabeth Fonseca, an air quality expert at the Environmental Defence Fund Europe, said that long-term cleaner air was essential to protect people’s health. “Nitrogen dioxide pollution has gone down, but London recently saw huge spikes in dangerous particulate pollution. A few weeks’ or months’ improvement of just one pollutant doesn’t make lung disease and other ailments disappear.” There is mounting evidence of detrimental health impacts of air pollution, through lung disease, heart attacks, asthma, effects on pregnancies and on intelligence levels. Research published on Monday also found that the five most polluted regions among 66 analysed in Italy, Spain, France and Germany accounted for 78% of all reported Covid-19 deaths in those areas. Another study looked at fine particle pollution in the US and found that even small increases in levels in the years before the pandemic were associated with far higher Covid-19 death rates. In the UK NO2 has been at illegal levels in most urban areas for the last 10 years. A key policy to reduce levels involves clean air zones – such as the ultra-low emissions zone in London – where charges are imposed to deter the most polluting vehicles from city centres. But the coronavirus crisis has seen some councils delay the planned introduction of clean air zones. Many cities across Europe, and some in the UK, have begun to unveil ambitious cycling and walking schemes to ensure people can move around safely and maintain the environmental benefits, in terms of cleaner air and safer streets, that have come about amid the lockdown. Gary Fuller, an air pollution expert at King’s College London, welcomed Thursday’s figures and said the policies introduced in London and elsewhere proved air pollution could be tackled. He said: “Breathing bad air has had an intolerable impact of Londoners’ health for far too long … but even before the Covid lockdown, London’s air pollution was undergoing a dramatic change for the better. “Nitrogen dioxide in central London and along main bus routes was improving at some of the fastest rates we’ve ever measured. We need to remember these lessons going forward. These successes show that our city’s air pollution is not an intractable problem and that actions can bring results.” Prof Stephen Holgate, an adviser on air quality at the Royal College of Physicians, said that although Covid-19 had wreaked havoc, the “dreadful virus has brought the importance of outdoor space and the environment into focus”. He added: “We’re all looking forward to the time when the lockdown is lifted, and once it does I sincerely hope we’ll be able to retain some of the new cleaner and greener habits we’ve developed.”