More than 1,000 nurseries in England are within 150m (164 yards) of roads that break legal limits for air pollution, ITV News has learned.
The majority of nurseries close to polluted roads - 760 out of 1,015 - are in London, but as the research by Greenpeace and seen by ITV News shows, the problem stretches to towns and cities across the country.
Outside of London, the top 10 local authority areas most affected are: Birmingham, Sandwell, Nottingham, Plymouth, Manchester, Leicester, Hampshire, Leeds, Wolverhampton and Salford.
Greenpeace's findings are based on the levels of nitrogen dioxide (NO2) close to nurseries in England only.
NO2 is a toxic gas largely produced by diesel vehicles and is linked to lung and respiratory issues.
By law the annual average limit for nitrogen dioxide (NO2) is 40 micrograms per cubic metre of air (µg/m3). A microgram is one millionth of a gram.
Analysis by the Department for Environment, Food and Rural Affairs (Defra) found NO2 is estimated to be responsible for 23,500 deaths in the UK each year.
In London there were more than 20 nurseries close to a road where NO2 was more than double the legal limit, and one - Tower Hamlets Opportunity Group - where it was almost three times the limit at 118.19µg/m3.
High exposure to polluted air at a young age is thought to lead to an increased risk of developing asthma and may also stunt lung growth.
Alexandra Morfaki-Williams, Nursery Manager and Associate Lecturer for the Department of Education at the University of West of England, said that while she wanted children at her nursery to learn about the environment, she often avoids taking the children outside at the busiest times of day in an attempt to limit their exposure to air pollution.
She continued: "We always have to strive for something better and raising environmental awareness and if possible limiting these emissions will be a positive thing."
Following the latest findings, Greenpeace has renewed its calls for the car industry to ditch diesel and switch to electrical powered vehicles.
The organisation also called on the Government to help with this transformation by introducing a national diesel scrappage scheme and investing in electric vehicle-charging infrastructure.
Anna Jones, Greenpeace clean air campaigner said: "Most people don’t realise that all across the country, toddlers are being exposed to invisible air pollution caused by diesel vehicles.
"At such a young age, children are extremely vulnerable to its effects, and it can cause a lifetime of ill health and reduced lung function.
“We were told diesel cars were the cleaner choice, but car makers lied about the toxic pollution they emit.
"That deception has left our kids exposed to toxic air pollution that’s causing widespread chronic health problems.”
Chris Griffiths, Professor of Primary Care at Barts and the London School of Medicine and Dentistry and co-director of the Asthma UK Centre for Applied Research, said: “The research is largely consistent across studies in the US, Europe, and also in London, that traffic fume exposure is associated with stunted lung development in young children.
“Although Greenpeace’s investigation relates to the EU annual legal limit for NO2 pollution, there isn’t an accepted safe level.
"So even toddlers in nurseries where the exposure levels are lower will also be at risk of damage to lung growth.”
Andy Edwards, Air Quality Officer for Bristol City Council, explained that air quality "levels do need to improve because there's a duty to meet those air quality limits that have been set".
Greenpeace added that following the emissions scandal, two-thirds of new diesel cars (those built since 2014) are still not meeting emissions standards in real world conditions, with some emitting 15 times more pollutants than they should.
Ms Jones continued: “The only way to make our communities safe is to tackle air pollution head on.
“To fix this problem we need wholesale transformation on our roads away from diesel and towards hybrid and electric vehicles.
"Both the government and the car companies need to work urgently to fix this.”
The High Court has ordered the UK Government to look at its plans to tackle air pollution, with a deadline of April 24, 2017.
Currently the Government advisory panel the Committee on Climate Change believes 9% of new car sales should be electric by 2020 for the UK to meet its legal obligation to cut greenhouse gas emissions by 80% by 2050 compared with 1990 levels.
In 2016 the market share of new car sales for alternatively fuelled vehicles was 3.3%, up from 2.8% the previous year.