Two primary schools near a main road show high levels

Air quality surveys carried out twice, which measured emissions around two primary schools in Chiswick, showed a gap in the levels of pollution which has not been explained, the Chiswick Area Forum heard last week.

Hounslow Council's measuring found levels to be lower than a TfL survey, but efforts to find out why did not yield a response from the transport company.

The TfL report on air quality three years ago had found levels breached EU standards at two schools in the borough - two of which, St Mary's Catholic Primary and William Hogarth primary- were in Chiswick. The third school was Floreat in Brentford.

Both local schools are close to the A4.

Following the publication of an updated report on air quality in London’s schools by TfL (previous report in 2013), the Chiswick Area Forum had requested an update on air quality in schools in and around Chiswick.

Hounslow Council said that its monitoring showed that only 2 of the 3 schools named in the TfL report showed exceedence of the annual mean limit value (or Target value of 40 µg/m3).

The NO2 Annual Mean 2013 (µg/m3) for St Mary's Primary was found by TfL to be 49.0 but LBH figures put this at 42.4- a 13% difference.

For William Hogarth School the TfL measured an NO2 Annual Mean 2013 (µg/m3) of 42.4 but the Council's figure was 34.6%.

"TfL’s modelled values are significantly higher at all three schools than the Council’s measured
data. The Council’s monitoring points are usually located outside the school boundary and NO2
concentrations are measured using passive diffusion tubes.

"Air quality within playgrounds located a few metres from main roads may be different but normally the NO2 concentration levels drop-off significantly with distance. Therefore, one would expect NO2 concentration levels within schools to be lower than those measured/modelled concentrations levels at the monitoring location.

"TfL have been contacted via Aether, so that the Council can understand the gap between their modelled concentration levels and our measured concentration levels, however, no response has been received, " according to a council report presented to the CAF.

Hounslow Council's report added that levels of pollution along Chiswick High road were falling.

Analysis of 2015 air quality data indicated that there was a reduction of 13.4% in NO2 annual mean concentration level over 2014, and there was significant reduction in particulate matter (PM10), at Chiswick High Road, it said. This was partly due to lower emissions from new buses.

November 12, 2016