Incoming UK government must take 'immediate action' on air pollution, says Supreme Court

In a unanimous judgment, the UK's highest court said that the next government "should be left in no doubt as to the need for immediate action" to tackle air pollution after next month's general election. The UK has been in breach of limits on nitrogen dioxide (NO2) in outdoor air, as set out in the EU's Air Quality Directive, since 2010.

Environmental law expert Eluned Watson said that the judgment had the potential to be a "game changer", which could now promt a shift in approach to air quality control across Europe as the UK is not alone in having struggled to meet the targets. The Supreme Court heard evidence that 17 member states were currently in breach of the limits, she said.

"The UK government will now have to act fast to cut NO2 levels to avoid hefty fines," said Watson. "For business, this will inevitably mean more stringent regulation – but savvy firms will translate investment into low emission vehicle fleets and ramped up green travel policies into cost savings and PR benefits."

EU law makers may now find themselves under some pressure to rethink the directive and the EU's approach to managing pollution levels," she said.

NO2 is the main air pollutant that leads to ground-level ozone, which in turn can cause major respiratory problems and damage to animals and plants. Those living in cities are particularly at risk as most NO2 emissions originate from traffic fumes.

The Air Quality Directive sets limit and target values for the concentrations of various air pollutants present in ambient air, including NO2. These limits came into force in 2010, although member states were able to apply for a give-year extension to ensure compliance. In order to qualify, they had to be able to demonstrate that they had workable plans in place to bring air pollution down to acceptable levels by 1 January 2015.

ClientEarth, a group of environmental lawyers and activists, took the UK's Department for the Environment, Food and Rural Affairs (Defra) to court after its draft plans to reduce pollution showed that 16 'air quality zones' including Manchester, Birmingham and Glasgow would not comply with the limits until 2020. Pollution levels in London would take until at least 2025 to bring within the limits. In November 2014, the Court of Justice of the European Union (CJEU) said that the Supreme Court was entitled to use "any necessary measure" to enforce the directive.

In its judgment, the Supreme Court found that air quality in some areas had deteriorated further since the case began. According to the latest projections, pollution in London, the West Midlands and West Yorkshire will not even have fallen to acceptable levels by 2030, it said. Although work is underway at EU level to develop vehicles with lower emissions, the Supreme Court noted that the limits remained legally binding and that the European Commission had already begun separate enforcement proceedings against the UK.

The court heard evidence that Defra was already developing a new plan, to be presented to the European Commission by the end of this year. However, Lord Carnwath said that the court would be "failing in [its] duty" if it simply "accepted [the government's] assurances without any legal underpinning".

"The new government, whatever its political complexion, should be left in no doubt as to the need for immediate action to address this issue," he said. "The only realistic way to achieve this is a mandatory order requiring new plans complying with [the directive] to be prepared within a defined timetable."

The court rejected arguments for a shorter timetable introduced by ClientEarth, concluding that the 31 December 2015 deadline proposed by Defra was "realistic".