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‘Stolen’ Tubes - is 3% ‘a key issue’?

April 18, 2021 11:26 AM
By Peter Dobbs

NOx tube at Windmill lane (Peter Dobbs)

A NOx diffusion tube mounted on a lampost

Derbyshire Dales District Council have been trying really hard to make it seem that they have not been dilatory in declaring an Air Quality Management Area for Buxton Road and St John's Street in Ashbourne. Head of Regulatory Services, Tim Braund, is quoted in the Ashbourne News Telegraph as saying that 'a key issue during the council's investigation of pollution in Ashbourne Town Centre has been the repeated theft of the diffusion tubes used to monitor air quality'.

It is interesting to analyse this claim using the records published on the DDDC's own website.

In the four years from 2017 to 2020, 198 tubes have been placed at various locations around the town, left for four weeks and then collected and analysed for their exposure to the polluting gas, nitrogen dioxide.

During that time just 6 have been 'lost', resulting in no data for that 4 week period at that particular location - an average of just 3%. As it happens only ONE of those tubes was in a pollution 'hot spot' with 4 tubes being taken from a site opposite the park at the end of St John Street. This site is designed to provide 'urban background' pollution levels and since the maximum number of tubes 'missing' in any year has only been 2 there has always been sufficient data to derive a reliable figure for this parameter.

Also the loss of just one tube from one of the monitoring positions on Buxton Road could in no way prevent the pattern of results from being observed. Graph of NOx at 25 Buxton Rd (Peter Dobbs)

You don't need any maths qualifications to see the pattern here - the absence of the figure for June 2020 does not alter the obvious conclusion - the level of NOx is well above the acceptable standard and only when the country was in strict lockdown did this fall to a 'safe' level.

Mr Braund says that 'people should not leap to conclusions [about any delay] without the evidence to back it up'.

We could not agree more.