A failure to plan? The UK and its obligations under the Air Quality Directive

On 4 March 2021, the Court of Justice of the European Union (CJEU) ruled that the UK has “systematically and persistently”[1] exceeded legal limits for dangerous nitrogen dioxide (NO2) since 2010 and failed to put in place an effective strategy to reduce the levels as quickly as possible. The case was brought by the European Commission (EC) who during the proceedings argued, “Severe and prolonged exceedances can have a particularly serious impact on the health of a population”[2].

The judgment relates to the UK’s obligations under Directive 2008/50/EC on ambient air quality and cleaner air for Europe (the AAQ Directive). Article 13 of the AAQ Directive requires that, “Member States shall ensure that, throughout their zones and agglomerations, levels of sulphur dioxide, PM10, lead, and carbon monoxide in ambient air do not exceed the limit values” set out in the Directive. Where the limits of those pollutants are exceeded, Article 23 requires that, “Member States shall ensure that air quality plans are established for those zones and agglomerations in order to achieve the related limit value” in as short a period as possible.


In September 2011, the UK had submitted air quality plans for some 40 zones where NO2 limits had been exceeded during 2010. The lawfulness of those plans was challenged in the UK Supreme Court by ClientEarth in 2012, and the Secretary of State was ordered to submit new plans by the end of 2015. The EC also concluded in 2014 that the United Kingdom for the year 2012 only complied with the annual NO2 limits in 5 zones. The 2015 plans were produced but only anticipated NO2 limit compliance in numerous zones by 2020, and in Greater London not until 2025 (dates that the Commission later argued appeared to “have been selected at random”[3]). These were again challenged by ClientEarth and the High Court ordered that further new plans be published by mid-2017. Those were in due course submitted to the Commission but, in January 2018, the Commission organised a summit on air quality during which the UK was invited to present, “additional binding commitments for timely, effective and credible measures”[4] to avoid referral to the CJEU. Having considered those proposals, the Commission concluded that they would not address the exceedances in as short a time as possible, and duly lodged the instant action before the CJEU.

The judgment

Article 13

The CJEU held that, “the data contained in the annual air quality reports…show that from 2010 to 2017 inclusive, the annual limit value for NO2 was exceeded in the 16 zones”[5] and that, “the stated values regularly exceeded between 25% and 75% of the limit value”[6]. In some years, the levels were three times higher. The UK attempted to argue that it was not the only Member State that has declared such breaches but the Court bluntly noted that, “a failure by another Member State to fulfil its obligations does not exonerate the United Kingdom”[7]. Importantly, the Court was also not persuaded that the ‘diesel emissions scandal’ provided any excuse given that affected vehicles are not the only cause of NO2 emissions[8].

Article 23

The UK argued that it had, at every stage, prepared revised air quality plans, designed to ensure that the period of exceedance was kept as short as possible[9] but the Commission responded that, “the 2017 plans merely repeated the measures foreseen in the 2015 plans”[10]. The UK also argued it was incorrect to assume their obligations under Article 23 were breached simply because the limits continued to be exceeded, and that, in relation to the 2017 plans, “the Commission has not attempted to conduct, as required, a case-by-case analysis of the plans taking into account all of the material put forward as part of the overall plan for the United Kingdom”[11].

However, the CJEU held there was no mere presumption that a breach of Article 13 indicated a breach of Article 23, but there instead was a “direct link” which indicated, “where those exceedances are of a certain magnitude and duration, they are evidence that the United Kingdom has not taken the measures it is required to take”[12]. It described the 2015 plans as “insufficiently detailed, summary or vague”[13] and, where the intention was that the 2017 plans might address such deficiencies, “On the contrary, in the majority of cases the period foreseen for complying with [the Directive] obligations is even longer”[14].

Accordingly, the Court found that, “the United Kingdom has manifestly failed to adopt in good time appropriate measures to ensure that…the limit values in question are exceeded is kept as short as possible in the zones concerned” and that, “the exceedance of those limit values has remained systematic and persistent”[15].

Therefore, the CJEU declared the UK had failed to fulfill its Article 13 and 23 obligations under the AAQ Directive.


The CJEU’s judgment represents a damning indictment of air quality in parts of the UK, and of the Government’s failure to produce effective mitigation plans in accordance with its obligations under the law.

These are issues of the highest significance: in August 2018, a report produced by the report by the Committee on the Medical Effects of Air Pollutants and Kings College London estimated that, “between 28,000 and 36,000 people die as a result of air pollution every year in the UK”[16]. One of those was the tragic and widely-reported death of 9 year old, Ella Adoo Kissi-Debrah. Following the inquest into her death the coroner, in what is thought to be the first time that air pollution was found to be a contributory cause of illness and death, stated, “between 2010 and 2013 she was exposed to levels of Nitrogen Dioxide and Particulate Matter in excess of World Health Organization Guidelines. The principal source of her exposure was traffic emissions. During this period there was a recognized failure to reduce the level of NO2 to within the limits set by EU and domestic law which possibly contributed to her death”[17].

In light of the CJEU’s findings, the pressure on the Government to ensure clean air for UK citizens is only likely to grow. Going forward, the UK will no longer be subject to air quality regulation within the EU and, with the new Environment Bill currently working its way through Parliament, it can only be hoped that any ‘new dawn’ after Brexit won’t be obscured by a haze of pollution.


[1] C‑664/18 §158

[2] §94

[3] §104

[4] §33

[5] §55

[6] §56

[7] §59

[8] §60

[9] §66

[10] §73

[11] §123

[12] §135

[13] §147

[14] §151

[15] §153

[16] https://www.kcl.ac.uk/news/uk-air-pollution-could-cause-36000-deaths-a-year

[17] https://www.innersouthlondoncoroner.org.uk/assets/attach/86/mnizari_16-12-2020_10-28-00.pdf