Air quality assessment after lockdown

James Bellinger (CEnv), senior consultant at Arup discusses the change in air quality assessments as a direct result of this lockdown period.

The impact of Covid-19 has shown some remarkable findings in relation to air quality. For the first time in decades, certain roadside locations have shown concentrations which if held stable would meet the World Health Organisation air quality limits. Lessons can be learned from this period in terms of air quality and how the data can be used to justify future mitigation choices. We have written about these findings and lessons learned from the data in past articles.

Much of what we do as air quality consultants can be carried out from our computers and our team has done a fantastic job of adjusting to home working. We are busy delivering work for clients and we are also looking ahead to think about what will change in our assessments as a direct result of this lockdown period. This article will discuss some of the challenges ahead and identifies some possible solutions.

How has the baseline changed?

For air quality we assess what the existing situation is to give us an understanding of risks around an area and to do that we would look at existing recent air quality data. This period has resulted in a question mark around what we consider as our baseline. Data for this year will look quite different in many places in comparison to 2019. There is also the question of what the new baseline will be – will activity return to the same level as last year or will there be tangible changes in how we use transport and energy?

With the change to ‘normal’ life that we have seen caused by the lockdown, it makes sense to disregard this year when looking at a baseline for air quality. When reviewing the situation in 2019, we still need to consider the present. Trends in pollution which have seen a reduction at a location may not continue to fall, especially if this leads to an increase in personal car use as people continue to social distance after lockdown and avoid public transport. So, the question for assessments in future years will be how has this period changed behaviour? For example, how do we increase economic activity without putting environmental performance at risk?

All that can be said at this point is that using last year’s data will be suitable as a baseline year for assessments carried out during the next two years. After this the situation will need to be reviewed to determine how air quality has changed in the longer-term following lockdown.

Future air quality predictions, what will change?

We don’t have a crystal ball to predict the future but there are a number of immediately obvious potential scenarios which could affect air quality. For road traffic assessments, emissions for future years are taken from the Defra emissions factor toolkit. However, due to the uncertainties which now arise there will be risks to using this data-set.

Future road emission factors will be affected if the economy slows down and there is less take up of new cleaner vehicles. To adjust our assessments for this, we would consider a conservative assessment and that could mean assessing future emissions with no improvements beyond 2019 emissions. That will certainly be an option for assessment of sites which are due to open within the next five years.

It can be presumed that the economy will be affected by lockdown which will result in less spending and therefore less take up of new cleaner vehicles and electric vehicles. Therefore, if traffic flows return to the same levels as in 2019, there will be less of a reduction in emissions due to the changeover of the fleet than would have been expected.

Working with transport team colleagues will remain important when considering what the fleet volumes and fleet mix will look like in our future. Arup’s Transport teams are working closely with the UK government and transport authorities, to provide advice on this and other active travel initiatives.

Significant or not significant?

Air quality assessments are ultimately an assessment of a scheme’s impact, whether it is going to be significant or not. Arup’s air quality team regularly represent clients at planning hearings or as expert witnesses and our approach to provide assessments which are built on robust and where necessary realistic conservative assumptions, will remain the same The methodology which is set out in the EPUK/IAQM guidance is still fit for purpose with the important point that suitable professional judgement is applied.

There is likely to be an increased need for sensitivity testing of future year emission options. We would propose using 2019 emissions for any development opening in the next five years as a starting point for that sensitivity testing. Air quality modelling and assessment of emissions will continue to be important for the assessment and testing of future impacts. Monitoring will be required to continually review how local air quality has been affected by changes in activity.

This lockdown period has shown the significant reductions in travel and human activity which are required to meet the WHO recommended limits for air quality. This raises questions, not just for air quality consultants delivering assessments for planning or permitting but also for planners and policy makers. As we look to see how air quality is affected by a wide range of impacts in urban areas, we continue to advise our clients on the best way to follow a joined-up approach to improving air quality.

Please note: the views expressed in this blog are those of the individual contributing member, and are not necessarily representative of the views of IEMA or any professional institutions with which IEMA is associated.