air quality monitoring diffusion tube
This is an air quality monitoring diffusion tube

Did you know that the point where Gap Road, Plough Lane, Durnsford Road and Haydons Road meet is not only a key junction but actually among the busiest in the borough of Merton? It’s a claim backed up by TfL statistics and repeated by our MP.

With high traffic levels, a couple of nearby industrial estates and often stationary vehicles it is also among Merton’s worst areas for air quality. At least, it used to be. There are now no records of current air quality levels and haven’t been since 2014.

Merton Council carries out air quality monitoring through the use of diffusion tubes in a number of sites across the borough, which used to include busy Plough Lane. Diffusion tubes are ‘a relatively cheap way of monitoring, allowing more sites to be monitored to give a Borough-wide view’, according to the LBM Air Quality Annual Status Report for 2015 (published Sept 2016). More detailed, roadside base station monitoring takes place at just two sites in Merton: a roadside site at the Civic Centre in Morden, and a roadside site in Merton Road, South Wimbledon. These two sites form part of the King’s London Air Quality Network.

The annual mean objective for nitrogen dioxide is set at 40 µg m-3. Exceeding this is A Bad Thing.

In 2013, 25 sites were monitored. Plough Lane readings showed an average mean reading of 66.1 µg m-3, peaking at 80.0 µg m-3 in January with the lowest monthly reading sitting at 51.0 in August: still far in excess of ‘safe’ levels. Once bias adjusted (to an annual average of 54.9 µg m-3) according to DEFRA recommendations, the only sites to equal or exceed Plough Lane readings that year were Colliers Wood High Street, Merton High Street, London Road Tooting, Crown Lane Morden and London Road Morden.

We were interested to know why Plough Lane readings had disappeared, given they were among the highest in the borough and therefore surely worthy of being recorded for Public Health reasons. So we emailed Merton’s Environmental Health Pollution Manager Jason Andrews to find out more.

He informed us by email: “I have spoken to the person that coordinates the diffusion tube network and the reason Plough Lane has temporarily been removed was due to the tubes going missing. We are re-evaluating the network and will likely be reinstating this area, it is also important to note that this monitoring network is being reviewed by the Councils Scrutiny Committee so should be enhanced over the next few years.”

It’s worrying that tubes can go missing and not be replaced in such a high-pollution area, also that there is no guarantee that air quality monitoring in Plough Lane will be resumed. It would also be useful to have diffusion tube monitoring installed at the top of Haydons Road, given the frequency of traffic jams in the area. Perhaps we should all get in touch with our local councillors to press for this to take place?

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