Kids more affected by traffic fumes
Scientists have come up with a new way of measuring the amount of pollution in the air around us and it's not great news for children.
The results show traffic pollution from cars and lorries is at its strongest the closer you are to the ground.
That means if you're shorter or smaller, you're more likely to be breathing in harmful fumes than adults.
Now politicians are studying the research to see what else they can do to help reduce traffic pollution.
Harmful particles that come out of car exhausts are so tiny - smaller than the width of a human hair - that you can't see them, so you breathe them in without realising.
Toxic particles from car exhausts are invisible
But if soot from traffic fumes gets into our lungs it can increase the risk of getting conditions like asthma and other serious health problems.
In east London, hundreds of kids are taking part in an experiment to see how their bodies are affected by fumes.
Scientists have also come up with a new way of testing the levels of pollution near schools, by collecting leaves from the roadside.
Professor Barbara Maher from the University of Lancaster said: "As we're standing at the roadside, we're surrounded by this invisible mist of these millions of toxic particles.
"We can't see them but we know we've measured them here and our research shows that down at small child height the concentration and number of these very fine particles is sometimes twice the current EU regulation standard."
Future problems for children
There are already cleaner fuels for cars, but experts say that won't be enough to stop many kids facing serious lung problems in the future.
Now politicians are working to see if there's anything else they can do to reduce traffic pollution.