Garbage in, gospel out? – Air quality assessment in the UK planning system

• Published in: Environmental science & policy Vol. 101; pp. 211 - 220
• Main Authors: Mills, Ashley, Peckham, Stephen
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2019
• Subjects: Air pollution; Air quality management; Planning; UK regulation; Air pollution; Planning; Air quality management; UK regulation
• ISSN: 1462-9011; 1873-6416
• DOI: 10.1016/j.envsci.2019.06.010

•In 30% of cases use of the Defra bias correction spreadsheet degrades accuracy by more than 10% relative to the corresponding locally derived bias factor.•In 30% of cases the Defra bias correction spreadsheet degrades accuracy relative to no bias correction at all.•Diffusion tube bias adjustment improves mean accuracy at the cost of increasing the percentage of points that underestimate the true value. In the United Kingdom, the planning process requires applicants to submit an air quality impact assessment wherever an impact on national limit compliance is likely, and this factors into the resultant decision. We identify flaws in the current methodological frameworks and policies associated with this process that in the worst cases could lead to poor decision making. We give examples of how inaccurate data is certified as good through unsuitable pre-processing, how these errors are then amplified by poor modelling practice, and how the final data is judged against metrics that are evidence impaired to arrive at potentially unsound decisions. We then discuss the implications and propose a way forward.