LONDON (Reuters) - London’s Heathrow airport could build a third runway without breaking European pollution laws, according to research published before a British government decision on airport expansion, the BBC reported on Thursday.

An aircraft lands at Heathrow Airport near London, Britain, December 11, 2015. REUTERS/Neil Hall/File Photo

Europe’s busiest airport is battling Gatwick, London’s number two airport, for government approval to build an extra runway, with a final decision due in the next few weeks after more than two decades of deliberations due to local protests about noise and pollution.

Heathrow, Britain’s biggest port which handles a third of the country’s non-EU exports, says it can build more routes with trading nations but has faced greater scrutiny over its environmental impact. Gatwick says it can build a new runway at a lower cost and with less harm to the environment.

In a potential boost to Heathrow, research from the University of Cambridge showed that any increased levels of poisonous nitrogen oxide from a new runway would be offset by lower pollution from traffic nearby as cleaner car models become more common, the BBC said.

The research, with no formal links to the airport or the government, used small sensors dotted around the airport to pick up changes in air quality more comprehensively.

“There will be more pollution (from the projected runway at Heathrow) but it will be against a background of reduced pollution from the wider area, and so the general pollution level will drop, we think below the critical level we now have for health impacts,” Professor Rod Jones told the BBC.

However Cait Hewitt, deputy director of Britain’s Aviation Environment Federation, told the BBC that basing a decision on the assumption car emissions would decline was “irresponsible in the extreme” because there was no supporting evidence.

Heathrow has said it will comply with an extended ban on night flights and meet European air quality rules if the project gets the green light.

It has also said it will meet 11 conditions set out by Britain’s Airports Commission, including a requirement on air quality which states that new flights will only be permitted if air quality does not breach EU limits.

The University of Cambridge said the results of the research have not yet been published.