Dust suppressants and monitoring sites

Meeting: 
MQT on 2011-12-14
Session date: 
December 14, 2011
Reference: 
2011/3733
Question By: 
Darren Johnson
Organisation: 
City Hall Greens
Asked Of: 
The Mayor

Question

On the matter of dust suppressants to tackle localised air pollution, you told me in answer to my question 3371/2011 that "no research has been undertaken to investigate if this targeted action in London's most polluted locations will create a significant issue for understanding the macro picture of air quality across London." On what evidence, therefore, did you state in answer to question 3679/2011, that "TfL's use of dust suppressants to reduce PM10 at London's worst pollution locations does not give the impression that pollution is lower than it is"?

Answer

Answer for Dust suppressants and monitoring sites

Answer for Dust suppressants and monitoring sites

Answered By: 
The Mayor

Written answer received on 21 December 2011:

The response to question 3371/2011 needs to be placed in context of the full response, which read "These two monitors are part of the comprehensive network of approximately 100 air quality monitors in London operated independently by Kings College. This comprehensive network of monitors still provides an appraisal of air pollution levels across London; and therefore, no research has been undertaken to investigate if this targeted action in London's most polluted locations will create a significant issue for understanding the macro picture of air quality across London." 

Therefore due to the coverage of dusts suppressants, relative to the scale of the monitoring network, no further specific research is required as the application of dust suppressants would not give the impression that pollution is lower than it is across London. Dust suppressants impact on less than 2% of sites. 

Further to this, TfL model the macro effects of air quality in London, which allows priority locations to be identified even if they do not have monitoring sites, such as Park Lane. To ensure that the modelling is as accurate as possible it is verified against data from the network of monitoring sites. If for any reason monitored concentrations are lower at a specific site than the general trend across London (for example, if local measures have been trialled close to a monitoring site) then whilst this would be reflected in the monitoring data at that site, it would not affect the London-wide modelling as this site would be treated as an 'outlier' in the verification process. Therefore, London-wide air quality modelling is not specifically affected by the application of local measures and TfL continues to rely on data from monitoring sites to assess the impact of local measures.