Air Quality Questions and Answers

31 January 2018

Michele sent in some questions regarding Air Pollution monitoring. These are the questions (in black) and the answers ( in blue) given by the Director of Regeneration and Public Protection at Nuneaton and Bedworth Borough Council. The reference that was questioned is from the Royal College of Physicians paper, Every breathe we take: the lifelong effects of air pollution

Please could you explain why the monitoring tubes on the Old Hinckley Road were moved from the lamp posts to the house fronts? I understand that you only seem to be concerned with the pollution levels at the houses but as the previous readings were from the lamp posts you cannot then claim that there is a reduction as you are not comparing like with like.

This is not the case, tubes have not been moved from lamp posts to the façade of houses, they have been on those house facades since 2008 and remain in position, while the corresponding kerbside tubes have been removed. The Council’s air quality monitoring programme is designed to meet the requirements of the National Air Quality Strategy and is compliant with the strategy and all related guidelines. Earlier monitoring and assessment has demonstrated that across the whole Borough the only issue of concern is the annual mean level of NO2, for which the relevant monitoring location is the façade of sensitive receptors, including houses. The best possible location for monitoring tubes is therefore the façade of houses. Where this is not possible the Council selects the next best available location and in these cases a nationally specified formula has to be applied to estimate levels at the façade of the nearest sensitive receptor. Therefore, if an opportunity should arise to relocate a monitoring tube at any particular address to a location nearer to the façade it makes good sense to do so. This provides more accurate direct readings rather than readings that had to be subject to a calculated adjustment.

In scientific research, when you are looking for the effect of something ( in this case the traffic), you have to keep everything else constant. By moving the position of the tubes and removing some altogether, you are putting in other variables and it means that measurements cannot be compared. As a result, any supposed trends are dubious to say the least. The house fronts are not even all the same distance from the kerbside so you are immediately putting in errors. Surely all the diffusion tubes should be on lamp posts at ( or virtually at) the kerbside so that the diffusion tube measurements all have equal effect from the traffic and can be compared properly? You can then distance correct to the houses.

Our monitoring does not only look at traffic. Traffic is the main source of NO2 but not the only source. Our monitoring also captures background sources of NO2. I disagree that you have to keep everything constant. That would only apply if the monitoring regime was perfect from the outset and nothing in the environment or scientific knowledge changed. When the monitoring regime is not perfect, in this case because not all tubes are located at the facades of sensitive receptors, it makes sense to make improvements where possible. Also when the environment changes and scientific knowledge moves forward, the priorities of the monitoring programme can also change. Our monitoring programme will change as required in response to these factors. You are incorrect in saying the monitoring tubes should all be on lamp-posts. As I have explained above they would ideally all be on the facades of sensitive receptors. We stand by our methodology, and our published results and conclusions.

I appreciate that as a campaigner for promoting cycling you have a particular interest in roadside levels, but the Council’s objective is to protect the health of the population and its monitoring programme is designed around that objective, rather than any other.

As someone who mostly walks or cycles along those sections of road, I am all too aware of the traffic and pollution and, although the guidance says it is only people who spend many hours affected by the pollution e.g. in homes or schools, those of us who do use the roads and paths would like to have the pollution as low as possible, not simply below the legal level.

I am not aware of any guidelines that say only people in houses are affected by traffic generated pollution. Road users are also potentially affected. However, as mentioned above, our monitoring has confirmed that there is no local evidence that roadside pollution exceeds any of the objectives in the National Air Quality Strategy.

The legal level, as I hope you are aware, does not mean a safe level. As evidence for this statement I quote from the Royal College of Physicians.

I note that you have quoted a single sentence from the Royal College of Physicians. I know that you are well aware of the risks of misunderstanding that arise from the use of selected quotations in this way without being able to see the context in which the statement was made. I am not able to comment in any detail on such a brief extract from a report without a reference that will enable me to read the whole report. Please supply a reference for this quotation if you want a comment from us about it.

With regards to “safe” levels it is important to note that while some scientists have made suggestions that there is no “safe” level for PM2.5 this has not been stated for other pollutants such as NO2. The below paragraph from the Government’s Air Quality Strategy explains the Government’s objective and reasoning around the air quality levels that have been set:

The UK Government’s and devolved administrations’ primary objective is to ensure that all citizens should have access to outdoor air without significant risk to their health, where this is economically and technically feasible. This strategy is based on standards from expert recommendations representing levels at which no significant health effects would be expected in the population as a whole and on the standards and principles of better regulation. The objectives in this strategy aim to move air quality as close to these standards as possible’.

The following quotes were taken from the website of The Chartered Institute of Environmental Health, which you said you were a member of.

The first extract above relates to concerns held by the CIEH that some local authorities have cut back on monitoring and personnel to a point where they can no longer meet their statutory duties. This council has retained the necessary monitoring infrastructure and expert capacity. You will note that the second paragraph refers to emission levels, rather than air quality levels or monitoring techniques. Reductions in emission levels at source will help to improve air quality levels and would be welcome. I agree that it is right to apply stricter air quality objectives where it is appropriate to do so in the light of evolving scientific evidence. As and when this happens the council will consider what changes it needs to make to its services in response to changes in air quality objectives.


It is information like this, from the relevant professional body, that makes me feel so strongly that we must not be watering down the monitoring here in Nuneaton and Bedworth but actually need to be increasing our monitoring. We are also only monitoring for NO2, whereas the emerging consensus is that it is the PM2.5 particles that are the ones we need to be particularly concerned about.


I do not accept your suggestion that our monitoring programme has been watered down. We have the same number of diffusion tubes deployed as in previous years but some are at different locations. It has evolved according to changes of priority and meets the requirements of the National Air Quality Strategy. I do not agree with your suggestion that we should be concentrating on PM2.5 rather than NO2. Local monitoring indicates that NO2 is the local priority and the annual mean for NO2 is the only objective against which we are required to monitor. However, I agree with you that PM2.5 is something that is of growing concern as a result of emerging scientific knowledge. The council’s officers are monitoring developments, and crucially the Government’s response to new developments for PM2.5. As Government issues new objectives or guidelines the council will consider what its response ought to be. I am satisfied that the council’s current position regarding PM2.5 meets its obligations.

I would also like to find out why the only air quality/air pollution monitor on the A5 , Watling Street, which must be one of the busiest roads in the Borough that has housing on it, is on the opposite side of the road to that which has the traffic queues? The worst pollution is from stationary traffic as it queues at the traffic lights with The Long Shoot on the Eastbound A5 and yet the monitoring is on the Westbound A5, where the traffic is almost always free flowing as the traffic is coming away from the traffic lights. The side where the monitor is supposed to be ( I say that because I was unable to locate it) also has a lay-by beside the road so if the monitor is on a house it is well away from the road. Could you please clarify exactly where the monitor is too please? In the annual air quality status report it says that it was at 64 Watling Street (where I could see where it had been on the lamp post) and that it is now NB35 at 62 Watling Street but I could not find it. I spoke to the residents, who knew nothing about it and told me that they had lived there for 4 years.

For clarification, historically there have been two tubes on the westbound Watling Street, one kerbside on the street light outside of 64 (NB13) and the other on the façade of 62 (NB35). NB35 has been moved to 60 Watling Street, it is on the same building and is the same distance from the road as for number 62 so is not a significant change. This will be the site address reported in the 2018 ASR. Site NB13 was discontinued at the end of 2016.


It is recognised that heavily trafficked roads and junctions can be the source of increased pollution levels from frequent stop-starts and acceleration away from the junction. This is of particular relevance when in combination with narrow congested streets and housing within 10 metres of the road or forming a street canyon with tall buildings. This junction is not like this, the housing is not close and the road is wide benefiting from good dispersion of pollutants. Houses on either side of the road will be affected by pollution arising from stop-start, idling and acceleration to varying extents so the whole road contribution is what is being measured and will solely depend upon the distance away from the road.


Results (reproduced below) for the last 6yrs show that concentrations of nitrogen dioxide are well below the 40 ug/m3 objective at both monitoring positions. You are correct in saying that levels may be higher on the east side of the Watling Street but only because the houses are closer on that side of the road. However, the objective has not been exceeded at the kerbside and there are no receptors that are this close to the road. We would expect that levels at the other houses would be somewhere between the two measured concentrations after correction for distance. We have no concerns that would warrant additional tubes being placed on the other side of the road.


Annual Mean Concentration of NO2 in ug/m3










Kerbside, Street-lamp near to 64 Watling St








Façade of 62 Watling St








We need to have good monitoring so that we can have evidence to enable us to get money from developers for mitigation measures.


We do have good monitoring and it is referred to when developers are asked to undertake air quality impact assessments to support planning applications. Even in the absence of air quality justifications, the Council does seek mitigation measures as part of the planning applications process and within policies contained in the draft Borough Plan, including highways investment, cycle path investment and other approaches to promoting a modal shift away from the internal combustion engine.


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