First UK site to breach NO2 legal limits in 2019?

In January 2017, the air monitor on the Brixton Road was the first to breach hourly legal limits for NO2 across the UK (more than 18 exceedances of 200ugm3).

During 2017 a total of 75 exceedances were recorded.

In December 2017, the Brixton Road Low Emission Bus Zone (LEBZ) was completed.

In January 2018, the air monitor on the Brixton Road again became the first location to breach legal limits.

By August 2018, Brixton Road had exceeded hourly limits 85 times (ten more exceedances than in the whole of 2017).

The air monitor on the Brixton Road then stopped recording at the end of August 2018.

The Brixton Road air monitor was not repaired during the remaining four months of 2018.

If the monitor had continued recording, we would have likely seen a total of round 120 exceedances for 2018, so a possible 60% increase in exceedances from 2017. Not what was hoped for or expected following the introduction of the LEBZ.

Why was there an increase in pollution following the introduction of the LEBZ on Brixton Road?

If you take a closer look at the buses and bus operating company, you may noticed a number of retro fitted buses used in the LEBZ and the use of Selective Catalytic Reduction (SCR) systems which are most efficient when the engine is working hard (i.e. by moving at speed or driving a heavy bus full of passengers).

You may note that when these buses are sitting in stationary traffic for long periods of time (like they do on the Brixton Road) the catalyst cools down and the NO2 is not efficiently removed. This is particularly the case for retrofit buses as they rely solely on SCR for NOx reduction.

There is potential for the SCR to be less efficient if it is not properly maintained and there is crystallisation. When the SCR is not operating efficiently tailpipe emissions of NO2 increase considerably!

The main operator of the bus route has confirmed to TfL that in December 2017 they discovered crystallisation in some of their SCR systems which increased the emissions of NO2 from these buses.

At the time people were being reassured that the air they were breathing on Brixton Road was cleaner due to the introduction of the LEBZ, it was in fact more polluted. Here’s the link to the LEBZ report:

At the start of January 2019 the Brixton Road air monitor was still offline.

On 9th January 2019, I visited Brixton Road to see the monitor for myself and I started this video blog:

I also took my AQMesh air monitor that I’d been using to monitor NO2 at a bus stop on the South Circular Road and mounted it on a lamp post on the Brixton Road.

As of today, Friday 1st February 2019, the air monitor on the Brixton Road is still offline, so unlike the previous two years where Brixton Road has been first to breach legal limits in January there is no data.

No evidence, no scandal, no interest, no scrutiny and no action.

London Air have reported that across all London monitoring sites this year, nitrogen dioxide has exceeded 200 μg/m3 for 11 hours so no location has yet beached the legal limit. Seven hours were reported in Kingston Upon Thames, when short-term roadworks reduced three lanes of traffic to one, right beside the monitoring site. One hour was at Oxford Street East and three hours were measured at Putney High Street.

Worth noting that the new traffic management system on Putney High Street has been introduced to hold traffic on Putney Hill for an increased amount of time which has significantly reduced the amount of time vehicles spend idling next to the air pollution monitor on Putney High Street. This has reduce pollution levels next to the monitor and kept the number of exceedances to a minimum. This has increase journey time and congestion on Putney Hill and may also have increased air pollution exposure for the people living and travelling there and for the children attending the school on Putney Hill. Video blog here:

So far in 2019, there has been less traffic next to the monitor on Putney High Street and lower levels of air pollution have been recorded. Brixton Road, the most likely monitor in the UK to exceed legal limits, has been offline since August 2018 (over 22 weeks).

Has London’s air pollution improved in 2019? Maybe.

Maybe not.


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