Traffic signs show a warning as a smog alarm is activated in Flanders and Brussels on January 24, 2013 | Dirk Waem/AFP via Getty Images Brussels ordered to get real on its pollution problem Amid a choking heatwave, the bloc’s top court says an endemic pollution problem can no longer be hidden.

Brussels is being forced to come clean about the level of toxic fumes being inhaled on its dirtiest streets.

The EU’s top court said Wednesday that regional authorities can no longer rely on their past practice of averaging air pollution measures across the city, a ruling that could expose an endemic pollution problem in parts of the Belgian capital.

The city's people have persistently been exposed to illegal levels of nitrogen oxide (NOx) and particulate matter (PM), which spew out of vehicle exhausts in congested parts of Brussels — levels worsened by this week's heatwave.

The EU's legal limit for NOx is 40 micrograms per cubic meter of air (µg/m3). A monitoring station at Arts-Loi in the European quarter recorded an average NOx level of 56 µg/m3 since it was turned back on in 2016. Another at Rue Belliard, which cuts across the political district, is averaging 52 µg/m3 so far this year.

Both of those areas are in the heart of the district where thousands of EU politicians and bureaucrats work.

“We have known for years that the EU district is in the middle of one of Belgium’s most polluted areas,” said Jens Mueller, who works on air pollution for Brussels-based campaign group Transport & Environment.

Both stations, and another at the European Parliament, which now records safe levels of pollution, were switched off by authorities temporarily in recent years, a decision green groups argue was an effort to conceal the scale of the city’s pollution problem. The regional government said that the siting of those stations wasn't in accordance with EU rules.

To meet EU norms, the government would average pollution levels across the city; nitrogen dioxide pollution in the leafy suburb of Uccle was 18 µg/m3 in 2018.

In its ruling Wednesday, the Court of Justice of the European Union said averaging values of air pollution “does not provide a valid indication” of the population’s exposure to pollution.

ClientEarth, a legal NGO that was one of the parties to the lawsuit against the city, said the ruling means Brussels cannot “hide poor air quality in some areas by using a city-wide average.”

Laying down the law

The EU’s Air Quality Directive, which sets rules on the use and location of measuring stations, gives national authorities discretion where to set up those points.

The Brussels government says it has more sampling points than required, and that those stations accurately represent the city, but locals have treated those locations with suspicion.

The city only has five monitoring stations collecting information on fine particle matter (PM2.5). A local campaign group conducted its own study in February and found illegal levels of PM2.5 across suburban areas and not only in the center. The group argued that the five stations are insufficient for a city of 1 million people measuring 160 square kilometers.

In its ruling, the CJEU said national courts can assess whether authorities’ choice of location accurately measures pollution.

Lies Craeynest, one of five Brussels residents who filed the case challenging the city’s air quality plan in court alongside ClientEarth, called the result “a total victory.”

Craeynest lives just off Rue du Trône, which runs from the central ring road out past the European Parliament. Her family “lives, eats, breathes ... in a bubble, covered by air pollution on a daily basis,” she said, adding that her own monitoring device had recorded “shocking levels.”

Late last year, the Commission filed a complaint against Belgium for its air pollution, saying the country had “persistently failed” to meet legal limits for NOx in Brussels and Antwerp. The formal letter sent by the EU to Belgian authorities explicitly questioned the location of measuring stations in the capital.

Heatwave politics

Wednesday’s court ruling also said people can invoke the EU’s Air Quality Directive to challenge how governments monitor air pollution. That’s already happening in Germany, where a string of judgments saw courts order city bans on older diesel vehicles to alleviate urban smog — in opposition to federal government policy.

“It shows that as citizens we do still have ways to weigh on politicians,” Craeynest said.

In Belgium, the ruling comes at a crucial moment, with parties in talks over new governing coalitions at a regional and national level. In Brussels, the Greens are in the ascendancy.

Brussels’ outgoing Environment Minister Céline Fremault from the Christian Democrats said she’d “taken note of the ruling,” adding that “in any event, the region aims to comply with European standards at each measuring point.”

In December, following the Commission’s action, Fremault promised her department would build a new measuring station every year until 2026.

Brussels also implemented a low emission zone in 2018 it hopes will cut the number of polluting cars. Regional authorities recently installed bike lanes on Rue Belliard, and have announced plans to redevelop the Schuman roundabout directly outside the European Commission headquarters to reduce traffic.