Our Nitrogen Dioxide Project


Alex Ingram has uploaded an ITV News piece on our work: https://www.youtube.com/watch?v=Ntk3hkEQKEA
Download Summary Report  and Detailed Results as PDFs

 Summary report  at —  http://hfcyclists.org.uk/wp/wp-content/uploads/2015/08/NO2_hfcyclists_ClientEarth_Report.pdf

Detailed Results and analysis Download at  http://hfcyclists.org.uk/wp/wp-content/uploads/2015/08/NO2_hfcyclists_ClientEarth_results.pdf




Nitrogen dioxide is a noxious gas given out by petrol and diesel engines, but particularly by diesel engines. It aggravates asthma and leads to many early deaths.


Andrea Lee on left with Paul Saunderson and Susie Gretz

On 4 February four members of hfcyclists, joined by Andrea Lee from Client Earth set off to place 33 small NO2 detection tubes around Hammersmith Gyratory and Shepherds Bush Green. They were collected and replaced on 4 March, and the fresh tubes will be collected a month later. We hope to get the results sometime in April.


John Griffiths, Chair of hfcyclists, placing an NO2 tube

London Borough of Hammersmith & Fulham measures NO2 / pollution in a few locations around the Borough, but at a height of 3m. Our tests are to show if NO2 pollution levels are higher in places where the NO2 may be concentrated because of the local geometry and prevailing winds. We also want to see if the levels are  higher at breathing height and push-chair height.

We hope to use the results to inform and influence those making traffic decisions at Hammersmith Gyratory and Shepherds Bush Green. If the results turn out to be of general interest we will consider how to broadcast them more widely.


Several tubes will be used at each site, so there are not 30 separate sites. We are looking at places where there are a lot of people crowded together with a lot of traffic. The local geometry and prevailing winds can concentrate the pollution in certain areas.





Because of the potential for interference when tubes are placed at a lower height LBHF only place tubes at a height of 3m. Pollution levels lower down and closer to the source are expected to be higher, but we do not know by how much. We will be measuring at two heights, 3.0m and 2.25m at the same location. We hope that by extrapolating, this will give us an indication of the NO2 levels at 1.5m,  approximately breathing height.


An NO2 monitoring tube in situ

At a couple of places where we do not expect any interference to the tubes we will be measuring at heights of 3.0m, 2,25m, 1.5m and 0.5m. This may give us an indication as to whether children in pushchairs are exposed to greater levels of pollution, and by how much.

It should be pointed out that NO2 diffusion tubes are not considered a very exact method, and measuring for only two  months out of a year will not lead to very robust results, and they may be described as “indicative”.

We will use statistics on our results to see how much reliance can be placed upon them. However we do hope to  extract useful information from these tests that may be used to inform people making traffic [and health] decisions.


The level found for 2013 at the Hammersmith Broadway NO2 diffusion tube site was 89.5 microgram / cubic metre. The EU guideline  for the maximum value is 40μg/m3 . Levels above 60μg/m3 could lead to a potential exceedence of the NO2 hourly mean Air Quality Strategy objective.

This is an important consideration that traffic planners must take into account when deciding whether to give space to pedestrians and cyclists or to motor traffic.


We did not find any consistent difference between the values at 3.0m and at 2.25m. We were surprised that at some places the values were higher at 3.0m than at 2.25m. In the circumstances we combined the values at the two levels to give an average for that location.

This also meant that we could not extrapolate to estimate the NO2 concentrations at normal breathing height. However we were able to find how the NO2 values varied around our locations and how they compared to the NO2 value at the LBHF reference point.

At the two locations where we measured at 4 different heights we found a gradual increase in NO2 as we descended to pushchair height.

It is possible that the proximity of the Hammersmith flyover may have affected the height distribution of NO2.

We applied corrections

a] for the difference between our reference tubes and the readings from the Automatic Monitoring Station at Shepherds Bush Green.

b] to estimate an Annual Mean by taking into account how our months compared to the general trend over the last year.

On the following pages are charts showing the adjusted values. The EU limit is 40μg / m^3 [40 microgram per cubic metre].

NO2 results Chart

NO2 values compared to the EU limit of 40μg / m^3

Pushchair Chart

Graphic showing the relative NO2 pollution at different heights


Graphic showing relative NO2 values at different heights


1] The NO2 values were all well over the EU limit of 40μg / m^3 [40 microgram per cubic metre]. Most were more than 2x the EU limit.

2] In Hammersmith all the values apart from the one in Beadon Rd were greater than at the LBHF reference location by St Paul’s Church. This may be due to the Canyon Effect where in enclosed places the pollution is concentrated.

3] At Shepherds Bush Green there is an Automatic Monitoring Station. Around the area all the values are higher than at the monitoring station. The closest LBHF tube is on the Uxbridge road and does not have a very high reading.

4] At present LBHF uses indications of the NO2 pollution levels that are below those that actually exist in some of the busiest spots. To bring these values down to the EU limit some extraordinary measures must be taken. One such would be to encourage a massive modal shift towards cycling for shorter journeys. This would involve using the road space to encourage cycling.

5] Whilst we only measured NO2 values in two locations at pushchair height, we found the values at 0.5m to be about 30% greater than at 3.0m where LBHF makes its measurements. At a buggy height of 0.8m the NO2 value is about 25% greater than at 3m. Young children with developing lungs are especially vulnerable to the effects of NO2 pollution.


John Griffiths Chair hfcyclists

122c Edith road, West Kensington, W14 9AP

020 7371 1290 / 07789 095 748



Andrea Lee ClientEarth

Community Engagement Officer (Healthy Air London)

t. +44 207 749 5979

e. alee@clientearth.org