Levels of toxic gas in gardens close to Heathrow were regularly 125% higher than maximum thresholds set out by the EU, new research reportedly found.
The extent of the pollution levels emerged as the bosses of Heathrow and the Airports Commission are due to be questioned today by MPs investigating the environmental impact of a new runway.
Heathrow rival Gatwick warned that pollution levels in west London were now worse than they were five years ago, insisting that there could be no “legal basis for approving Heathrow expansion,” the Times reported.
EU regulations state that emissions of nitrogen dioxide (NO2), which is linked to 23,500 deaths in the UK each year, should be limited to 40 micrograms per cubic metre (µg/m3).
A study by data management company OpenSensors found that average pollution levels regularly exceeded the 40 µg/m3 standard, according to the newspaper.
The study, which placed sensors in 20 residential gardens around west London, found that NO2 reached an average of 70 µg/m3 at Sipson, just over half a mile north of Heathrow, with highs regularly exceeding 90 µg/m3, 125% higher than the permitted standard.
The research, funded by Open Data Institute, showed that readings in Isleworth, which is six miles east of Heathrow, reached up to 75 µg/m3.
Airports Commission chairman, Sir Howard Davies, and Heathrow chief executive, John Holland-Kaye, are due to appear before the Commons environmental audit committee today where they will face claims that the proposed new runway would worsen pollution levels in the area.
The Commission recommended in July that Heathrow should expand because it would generate greater economic benefits, including more jobs and profitable long-haul routes, than Gatwick.
It insisted that the environmental impact of expansion “does not outweigh its very significant national and local benefits” when mitigation measures were taken into account.
Heathrow says that greener aircraft, changes to landing approaches and reforms designed to stop people driving to the airport — the biggest cause of pollution in the area — will enable it to achieve long-term pollution targets. This includes a link to the Crossrail network and new direct rail access to Reading and London Waterloo.
A Heathrow spokesman said: “We take air quality issues very seriously. The airports commission has been clear that Heathrow can expand while remaining within EU legal limits.”