Air Quality Network directors respond to link between sulphur dioxide and lockdown

Richard Maggs and Paul Willis, project directors of relevant functions on the UK Air Quality Network contacted Air Quality News following the publication of a story about the increase in sulphur dioxide levels during lockdown, disputing several points. Their response to the story is published in full below. 

We note the above article provided a headline on levels of sulphur dioxide (SO2) during the March to June lockdown period this year, which has gained considerable interest in the air quality community and amongst researchers.

We have looked at the data gathered from the network on which the data is based — the UK Automatic Urban and Rural Network — and note that the authors of the primary work which have informed your article have made a fundamental error.

That is, the analysis they have undertaken has not taken due account of the status of the data, which is classed (at the time of analysis) as being unverified, or ‘provisional’.

The AURN works on a status feed that is immediate to UK-AIR with the caveat that the unverified data should be treated with some degree of caution.

This is particularly the case for SO2 concentrations in the UK which are generally very low and close to limits of detection for AURN instrumentation.

The Quality Assurance and Control Unit subsequently undertake a verification process (otherwise referred to as ratification), which takes into account any anomalies in instrument performance and the calibration and maintenance regime observations in the preceding three months.

Following this exercise (and now looking at verified data only) the mean concentration of SO2 during lockdown fall from the author’s stated value of 3.95 μg/m3 to 1.87 μg/m3, which is consistent with the typical ambient concentrations of SO2 observed prior to lockdown.

As such, the conclusion that SO2 levels ‘doubled under lockdown’ does not hold true and the article gives a false conclusion.

We, therefore, wish to make you and your readers aware of this, having additionally raised the issue with the author of the work to make him aware.


Dr Richard Maggs — Bureau Veritas UK. Project Director, Central Management and Coordination Unit for the AURN.

Paul Willis — Ricardo Energy & Environment. Project Director, QA/QC unit for the AURN.


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