Children's Health, Respiratory Inflammation and Short-term Air Pollution

The goal of this study is to see if physical activity in high air pollution is worse than rest in high air pollution.

The study will recruit a total of 330 children from 10 primary schools split into two groups: "higher pollution" and "lower pollution" schools. The team shall invite children in years 3 to 6 to take part in the study and consent will be provided by parents following information sheets sent home in school bags and parent evening presentations. After the team have received written permission from parents. The study team will visit the school on two days. On the first day the study team will perform lung health assessment in a dedicated classroom. The assessment will involve, measuring children's height and weight, a breathing test (photo and a snot sample collected by squirting a small bit of saline water up one nostril and catching the snot in a cup. Children will then take part in a PE lesson or a sedentary science lesson in a random order in their school playground while wearing activity monitors - like a Fitbit- to track their physical activity. The session is designed to be just like a typical outdoor science or PE lesson and will be exactly the same at all schools. Air pollution levels in the playground will be monitored during this time. Once the PE lesson has finished the children will perform the same health assessment immediately after the lesson and again on a second day. The team shall compare the change in these scores between higher and lower pollution schools. The breathing tests will tell us if the has been any change in lung health and the snot samples will tell us about the pollution the children have breathed and how their bodies try to fight it. Participating will take about 4 hours total.

Inclusion Criteria: * Attending schools in Central and East London that have been recruited to the study Exclusion Criteria: * Not able to engage with PE lessons on safety grounds, reported by their parents. * Children with learning or physical disabilities sufficient for them to be unable to give informed assent to the study, or to carry out study procedures