Residents of Hampstead live in a very green part of London. Nevertheless, air pollution is an important issue. Heavy traffic was the top local complaint in a survey conducted last year by the Hampstead Neighbourhood Forum.

In response to this concern, the forum has a project under way to test levels of nitrogen dioxide (NO2) in 10 locations around Hampstead, using diffusion tubes. We are working with Camden’s air quality team, and we are supported by an amazing team of volunteers, including pupils from three local schools. We are also grateful to generous donors for financial support.

Half way through the year-long project, the data suggest a reduction in NO2 levels since we tested Hampstead’s air in 2015.

This encouraging news may show that the switch to electric vehicles is having some effect, as well as other efforts such as the Healthy School Streets scheme. But it is subject to several caveats.

Ham & High: Francesca Agostini is part of a project monitoring air quality in locations around HampsteadFrancesca Agostini is part of a project monitoring air quality in locations around Hampstead (Image: Hampstead Neighbourhood Forum)

First, NO2 is not the only pollutant. We are not testing for particulates, but other evidence shows that levels have also decreased slightly over recent years, but not nearly as much as those of NO2.

Secondly, we are measuring the monthly mean of NO2, so we cannot identify times during the day, or specific days when pollution is higher. We know that certain areas, such as around schools at pick up and drop off times, suffer high pollution at those times. It may be localised and limited in time, but nonetheless it is dangerous, especially for the children breathing it.

Thirdly, even if local NO2 levels drop below UK legal limits, these are higher than those considered by scientists to be safe. Camden is working towards implementing the more restrictive guidelines of the World Health Organization, and also advocates tougher UK limits for NO2 and particulates.

Our results are preliminary. We will have a full year’s monthly figures when the project is completed in the autumn, and we will report back in more detail then.

Francesca Agostini is co-leader of the air quality project for the Hampstead Neighbourhood Forum.