Recently I wrote about the progress made by Boris Johnson on being able to breathe cleaner air in London.

Air pollution means 5,000 of us in London die each year. That is compared to around a hundred of us being murdered. A few more of us die in road accidents – 135 in 2012. Those figures offer some sense of proportion. Air pollution should be taken far more seriously. The problem is the PM2.5 and PM10 which we inhale into the respiratory tract which reduces our lung capacity. You can argue that those 5,000 would have died anyway – but that point also applies to murder and road accident victims.

Gordon Brown’s 2001 budget – which encouraged motorists to switch from petrol to diesel didn’t help.

One of the ways of improving air quality is through the use of dust suppressant spray. The Leftist environmentalists – in the Green Party for example – hate the idea of it. That is because they want us to go “back to nature” and abandon a modern capitalist economy.  But those who want to find ways to combine cleaner air with economic growth should be enthusiastic about the prospect.

It is early days but so far the evidence is rather encouraging.

This study by the Environmental Research Group of King’s College London said that in five of the nine test areas there was proven to be a clear benefit. The ones in Acton and Neasden went particularly well. The Group report:

“The most robust findings were at Horn Lane. A clear drop in local PM10 concentrations occurred in the hour following on-site CMA application of between 31% and 59% relative to the control. A lesser decrease was associated with the on – road applications.

Analysis at Manor Road was restricted due to a lack of pre-trial period, but a similar decrease in local PM10 (41%) was associated with on-site CMA application. The complexity of the industrial area surrounding the Neasden Lane study site made robust analysis difficult, but some limited benefit of CMA application was identified.”

Another study looked at the impact in Scandinavia:

“In Stockholm successful results have been obtained using CMA. For example, a 25% solution of CMA in water was found by Norman and Johansson (2006) to reduced average daily PM10 concentrations by around 35%. The impact normally lasted around 10 days, and was strongest when the salt was first spread. Magnesium chloride has also been tested in Stockholm by Road Technology Sweden with good results.

The effects of four dust suppressants on PM10 concentrations were also investigated in other Swedish trials on rural road sections to the south of Linköping (Gustafsson, 2008). Each section of road was 600 meters long, and all the sections were separated by a distance of at least 500 meters. The suppressants chosen were CMA, CaCl2, MgCl2 and sugar solution, and these were sprayed on the road at regular intervals during the spring of 2008.

Particulate matter monitoring was undertaken using TEOMs (Tapered Element Oscillating Microbalance), active PM10 and PM2.5 sampling and passive particle sampling. The amount of dust on the road was also studied using a ‘wet dust sampler’. Meteorology (wind, temperature and humidity) was measured at one of the locations. Some preliminary results indicated that the suppressants led to an initial reduction to ambient PM10 of around 30-60% after one day, with the effect diminishing, but lasting several days in some cases (Figure 3). It can be seen from Figure 4 that the frictional coefficient of the road surface initially decreased following the application of each binder.”

I’m pleased that a further test is planned for Scrubs Lane, in my own borough of Hammersmith and Fulham. It could commence as early as next month although it may be decided to wait until after the winter to test its success during drier months.

The Mayor’s Air Quality Fund (MAQF) is run through a partnership between the GLA and TFL.  Their funding for this project though 2015-16 in my borough is £100,000. This comes from a total MAQF “pot” across London of £6 million.  There will be a further round of funding of £20 million across London once these projects are completed after 2015/2016.

In many ways the costs are modest for the potential gains. It involves retrofitting those salt gritted vehicles to spray the dust suppressant. Such adaptions cost around £70,000 a times – the vehicles can still be used for gritting if needed.

I can understand how it is difficult to measure quite how much impact this process has. What does seem clear is that it is significant. The Mayor should be encouraged to do more spraying.

It is also something that London borough councils should require during for major construction projects and road works. Boris has included it in new planing guidance.