Our Air Quality specialist, James Hewitt, is keen to engage, particularly with local people and schools, about how we can work together to improve the air we all breathe.

Given its health and economic impact, air quality is of interest to those who live, work, and invest in St John's Wood - and comparable locations elsewhere.  Greenhouse gas aside, the pollutants of greatest current concern are a gas - nitrogen dioxide (NO2) - and fine particulate matter - PM2.5.

NO2, often linked with asthma, is particularly harmful to children.  PM2.5 contributes to cardiovascular, respiratory and other illness.  On death certificates, coroners can now list air pollution as a contributory factor.

The main source of NO2 used to be diesel engines.  Emissions from this source have greatly declined.  In contrast, the contribution from gas heating and cooking has changed little.  NO2 concentrations tend to be worst in heavy traffic and when roads are congested.  PM2.5 concentrations are attributable to many factors, including construction and vehicles (through brakes and the interaction of tyres on roads), and may be blown in from industries, fires and land far away.  Concentrations of NO2 change considerably during the day, between summer and winter, and with distance from hotspots.  Those of PM2.5 change much less.

Engine idling may waste fuel and increases CO2 emissions.  The extent to which it causes air pollution depends on the quality of the engine and its fuel.

Since mid-2017, the St John's Wood Society has been monitoring the monthly concentration of NO2 at between 15 and 30 sites in the area using small measuring tubes.  The results are displayed as maps and charts (here).  Similar charts referring to other parts of Westminster, London and elsewhere are available from here based on data provided by government.

The initial purpose was to provide a baseline for monitoring the impact of CS11 (a proposed cycleway along Avenue Road).  Reflecting local interest, the cost of the tubes is being funded by Westminster City Council from ward budgets.

Across St John’s Wood during 2024, annual average concentrations of NO2 and PM2.5 were well below the UK legal limit but roughly double the World Health Organisation guideline.  The latter reflects many years of evidence and research.

The charts below provide a visual introduction to the most recent estimates of the geographic distribution of air pollution (2019) [uppermost row], road transport fuel consumption (2022) [middle row], and greenhouse gas emissions (2022) [lowermost row].