An estimated 50 million years of human life could be lost in the UK if action is not taken to reduce air pollution, scientists have said.
A study led by King's College London suggests that by meeting targets set out by the Climate Change Act, nitrogen dioxide air pollution could be cut by 50-60%, leading to improved public health and longer life expectancy.
The 2008 Act requires the UK to reduce greenhouse gas emissions by at least 80% on 1990 levels by 2050.
The study, published in the journal Lancet Planetary Health, found that if this target was met in London, one of the major pollutants - nitrogen dioxide - could fall by more than 50% by 2050.
There would also be significant cuts to levels of fine particulates.
It found Liverpool, Leeds and Manchester could see a 57% reduction in nitrogen dioxide pollution while Cardiff and Newcastle could benefit from a 42% reduction in small particulate air pollution.
The capital and other UK cities are regularly breaching EU and World Health Organisation (WHO) air quality standards, largely as a result of vehicle emissions.
Air pollution causes an estimated 40,000 premature deaths a year in the UK and is linked to health problems from childhood illnesses to heart disease and even dementia. It is also thought to affect children's development.
The issue is estimated to be costing the economy £20 billion in healthcare costs and lost productivity.
Lead author, Professor Martin Williams of the Environmental Research Group at King's College London, said: "This is the first study that compares the impacts of policy scenarios to reduce carbon emissions on health and life expectancy from changes associated with air pollution in the UK.
"Our research demonstrates that climate change mitigation policies have the potential to make dramatic improvements in public health through their parallel improvements in air quality.
"It is imperative that climate change and air pollution policies are considered together to fully realise the health benefits of both."
Professor Helen Stokes-Lampard, chairwoman of the Royal College of General Practitioners (RCGP), said the findings serve as a "stark warning about the trajectory of the challenges if we don't act now".
She added: "Climate change is a clear risk to the health and wellbeing of the British population.
"Perhaps most shocking is the estimated 50 million predicted years of life lost across Great Britain between 2011 and 2154 if certain factors don't improve.
"As GPs, we are already seeing more patients presenting with illnesses exacerbated by poor air quality, particularly in vulnerable members of our communities.
"This study shows that an 80% cut in greenhouse gases will dramatically reduce air pollution - so, it makes sense to take urgent measures to achieve this. What is good for the planet is usually good for our patients' health, and the NHS as a whole."
Professor Jonathan Grigg of the Royal College of Paediatrics and Child Health (RCPCH) said: "Children and young people benefit the most from improved air quality, as they are the most vulnerable to the impacts of air pollution.
"Tackling childhood asthma is particularly urgent given its prevalence - air pollution is associated with both reduced lung growth in childhood and severity of asthma for those with the disease.
"This study shows that the Climate Change Act is a powerful tool for reducing air pollution."
A spokeswoman for the Department for Business Energy and Industrial Strategy said: "This government has pledged to be the first generation to leave the environment in a better state than it inherited.
"With the UK a global leader in renewables, clean growth is a key part of our modern Industrial Strategy. We have grown our economy by over two thirds while cutting our emissions by over 40% since 1990.
"Air quality in the UK has been improving in recent decades but this important analysis shows the urgency of meeting our ambitious targets to reduce greenhouse gas emissions for the sake of our children and future generations."