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Investigation into Diffusion Tube Bias Adjustment Factors published by Scottish Government


A detailed investigation into the role of bias adjustment for nitrogen dioxide diffusion tubes has been carried out for the Scottish Government (available here).  The project was led by Prof. Duncan Laxen on behalf of Air Quality Consultants Ltd, with support from Prof. Mat Heal of the School of Chemistry at the University of Edinburgh.

Diffusion tubes are widely used by local authorities to monitor nitrogen dioxide concentrations.  The results, however, have to be ‘bias adjusted’ to make them as accurate as possible.  This is because tubes can over- or under-read, when compared to co-located chemiluminescence ‘reference’ monitors, due to a wide range of factors, including the laboratories supplying and analysing the tubes, and exposure factors that influence the uptake of nitrogen dioxide in the tube.  A detailed review of the literature was provided as part of the project (available here).

Concerns had been raised that some bias adjustment factors had been falling year on year, resulting in a reported improvement in air quality.  The Scottish Government wanted to know if these improvements were real or not, or an artefact of the bias adjustment approach.  To address this, the study examined diffusion tube and automatic monitoring data for all co-location sites in Scotland over the period 2008 to 2017. 

The study demonstrated significant and systematic between-site differences in overall bias, even for the same types of tube.  A number of possible explanations for this were identified.  Between-lab differences were also identified.  The downward trend in the overall bias adjustment factors identified by the Scottish Government appears to be mainly an artefact of the changes in the sites that have been used to derive the overall factor, together with some chemistry-driven downward trends due to the declining NO2 and NOx concentrations.

A number of recommendations are made for Scottish local authorities to improve the consistency of diffusion tube results.

Air Quality Consultants contributed to a Unicef report calling for action to protect children from the impacts of air pollution


The Unicef UK report “Healthy Air for Every Child: A Call for National Action” proposes a strategy to tackle air pollution and its effect on children’s health (access report here).  Mike Penrose, Executive Director at Unicef UK stated that the new report “implores government to take action and put children’s health at the heart of its work on air pollution. We urgently need a public commitment to reduce air pollution to acceptable levels, a national strategy that prioritises action for children, and ring-fenced funding to implement this – so that no child is denied their right to clean air.”  (see press release here)

Defra responded to this report saying “the best way to clean up the air … is to stop air pollution from being emitted in the first place. That is why our Strategy focussed on tackling the sources of air pollution.” (see press release here)

Dr Kate Wilkins and Penny Wilson of Air Quality Consultants were commissioned by Unicef UK to produce a literature review setting out a series of case studies on measures to reduce children’s exposure to air pollution.  The review identified a range of interventions applied at schools around the UK, and evaluated the effectiveness of the measures. 

Penny Wilson, Associate Director of Air Quality Consultants, said: “We were pleased to be invited to contribute our considerable experience of managing air quality to support the Unicef project.”


IAQM Launches Revised ‘Guidance on Monitoring in the Vicinity of Demolition and Construction Sites’



The Institute of Air Quality Management (IAQM) has published updated Guidance on Monitoring in the Vicinity of Demolition and Construction Sites.  Stephen Moorcroft of Air Quality Consultants chaired the Working Group that updated the guidance first published in 2012.  The Guidance covers monitoring of nuisance dust and particulate matter (PM) that arises during demolition and construction activities.  It is aimed at developers undertaking construction works and the local authorities who have to protect the public from nuisance and health impacts associated with dust and PM emissions. 

The updated Guidance takes into account feedback received from the users of the original document, and makes reference to newly available monitoring equipment.  This version also includes three case studies, one of which provides examples of good and poor practice of locating instruments.  Reference is also made to recent studies published by King’s College on Site Action Levels and the quality control/assurance procedures that should be applied to certain types of monitoring equipment.

A copy of the Guidance is available at: http://iaqm.co.uk/guidance/



Updated Results from On-Going Customer Survey


Delivering sound, reliable expert advice and a consistently high quality of service is fundamental to everything that Air Quality Consultants does. The company’s on-going client survey, now in its 7th year, shows that 99.5% of clients find Air Quality Consultants’ overall service to be ‘excellent’ or ‘good’, with the vast majority rating it as ‘excellent’. Further details are provided below.

About the survey
In August 2011 Air Quality Consultants commissioned a survey to measure how clients rate the company’ service and find out what they value most about working with Air Quality Consultants.  Since that time clients have been routinely invited to give their feedback in order to ensure that the quality of the work is being maintained.  This forms part of the Company’s QA/QC programme, which is certified to ISO 9001: 2015.  

As of September 2018, 210 survey responses have been received, and the year-on-year results over the seven years show consistent performance. 

Key findings
The 'overall service' that clients receive from Air Quality Consultants is rated as either 'excellent' or 'good' by 99.5% of respondents, with the vast majority (76%) rating the service as 'excellent'. This success is largely down to the 'knowledge and expertise' of the Company, which is rated by 99% of respondents as 'excellent' or 'good', with100% of respondents rating the 'quality' of the service as 'excellent' or 'good'.

The full results are shown below

Senior Level Appointments


Air Quality Consultants Ltd has made two high level appointments to complement its growing team.  Dr Denise Evans has been appointed as an Associate Director and Nigel Bellamy has been appointed as a Technical Director.

Denise previously worked at Air Quality Consultants in Bristol from 2005-2011. Following seven years working with multi-disciplinary consultancies undertaking air quality impact assessments across a range of sectors, Denise has rejoined AQC.

Nigel was formerly Head of Air Quality at Jacobs, where he was responsible for the delivery of both the Birmingham and the Greater Manchester Clean Air Zone projects.  He also supported the Davies Commission work assessing the impacts of expansion of airport capacity in the south east.

Welcoming Denise and Nigel, Chris Whall the Managing Director of AQC said; “Denise and Nigel are joining Air Quality Consultants at an exciting time for the Company.  AQC is now the largest independent air quality consultancy in the UK.  The technical experience that they each bring complements the existing industry-leading expertise provided by the Company, which will be invaluable in terms of helping us achieve continued growth and maintain the high-quality service our clients expect”

Nigel Bellamy said “I am delighted to be joining Air Quality Consultants, and I’m looking forward to working with some of the best technical specialists in the country. Understanding of the importance of air quality has never been greater, and AQC is a leader in delivering real benefits, for both its clients and the public, through the breadth of expertise available in the team.”

Denise Evans said “I’m excited to return to Air Quality Consultants and to once again be exposed to a range of technically challenging and unique projects.  AQC is a specialist company that truly understands and values air quality”

Denise has over 18 years’ experience in the field of air quality, in both academic and consultancy environments. She has extensive experience of Environmental Impact Assessment (EIA) for a variety of developments including large urban regeneration schemes and road schemes. Nigel has over 16 years’ experience as an air quality consultant.  He has worked very closely with major strategic clients including Highways England, Transport for Greater Manchester and Birmingham City Council.

Air Quality Consultants, which recently celebrated its 25th anniversary (more), has a strong and proven track record in providing air quality services to private and public sector clients, both within the UK and internationally.  Denise’s EIA experience and Nigel’s reputation for managing and delivering Clean Air Zone (CAZ) feasibility studies and their implementation will be particularly relevant in this context.



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