Pollution sensors have been installed outside a number of schools in Newcastle to find out how dirty the city's air is for children.
The city council and Newcastle University have placed monitors next to 22 schools close to busy roads.
They show how nitrogen dioxide and other toxic materials in the air change depending on time of day and weather.
It is hoped the move will discourage parents from using cars on school runs, or leave engines running if they do.
The sensors are monitored through the university's Urban Observatory, and early data has shown readings of nitrogen dioxide of more than twice the annual average legal limit outside several schools at 09:00 GMT, the Local Democracy Reporting Service said.
Eugene Milne, director of public health at Newcastle City Council, said: "Poor air quality harms everybody's health - and young people are among those most at risk.
"As well as raising awareness about the issue among pupils, parents and the wider community, the project will also aim to encourage more active travel and fewer car journeys, particularly on the school run.
"This project will help us to monitor just how much pollution is in the air around schools and enable us to get the views of the children who are directly affected on what else could be done to tackle the problem."
Newcastle, Gateshead and North Tyneside Councils are carrying out a consultation on introducing Clean Air zones and tolls in an effort to reduce pollution created by high emission vehicles.