A new report from two medical organisations urges the government to do more to curb air pollution from motor-transport, and stresses that more journeys should be done on foot and by cycle.
Co-author Professor Jonathan Grigg said there was now overwhelming evidence that air pollution – including from factories and motor-traffic – was linked to heart disease and lung problems, including asthma. Up to 40,000 deaths per year are linked to this pollution.
"As NHS costs continue to escalate due to poor public health - asthma alone costs the NHS an estimated £1bn a year - it is essential that policy makers consider the effects of long-term exposure on our children and the public purse," he said.
Professor Grigg said people should walk, cycle or take the bus or train instead of driving.
His colleague Professor Holgate told BBC Radio Four's Today programme: "When you see cars piling up on the way to school taking their children, the fumes directly from the vehicle in front are being vented straight into the car behind, and exposing their child - and yet we are ignoring this."
(A new “smogmobile” can now measure air pollution on the go and has found that NO2 levels inside vehicles is higher than outside.)
The joint report by the Royal Colleges of Physicians and of Paediatrics and Child Health said the NHS should lead by example. It says: "The health service must no longer be a major polluter; it must lead by example and set the benchmark for clean air and safe workplaces."
The report also said local authorities must have the power to close or divert roads to reduce the volume of traffic, especially near schools when air pollution is high. In many of the UK's cities this is "all of the time."
In London, some boroughs exceeded their allowable annual levels of poor air quality during the first week of 2016. Ironically, the "bikelash" against the new Super Cyclehighways often includes claims that getting more people on bikes will lead to greater air pollution – because of idling engines.