Would a third runway at Heathrow treble the number of deaths from air pollution?

"a third runway at Heathrow would increase deaths from air pollution linked to the airport from the current 50 a year to 150 by 2030"

The Daily Telegraph, 13 October 2012

"We pay more attention, I would wager, to arguments we like than to those we don't. Which is doubtless why I was so taken with reports of research saying that building a third runway at Heathrow could treble deaths related to air pollution (bringing them to 150 a year by 2030), while a brand new "Boris Island" airport could reduce them by two thirds."

The Independent, 16 October 2012

Not content with having a bicycle named after him, London Mayor Boris Johnson also has his sights set on a large land mass in the Thames estuary. According to the Conservatives' most popular politician, 'Boris Island' would be the perfect solution to the capital's lack of airport capacity. 

While others in his party would prefer to build a third runway at Heathrow, Mr Johnson is convinced that a new hub airport in the east of London offers the best deal for his constituents and the country as a whole.

In recent days the Daily Telegraph and the Independent have reported on new research that might provide a boost to Mr Johnson's campaign. The Telegraph warns that a third runway at Heathrow "would" treble the number of deaths related to air-pollution; the Independent, a little more circumspect in its wording, suggests that this "could" be the result. Both newspapers state that building an airport on Boris Island would mean a two thirds reduction in the number of air-pollution fatalities.

Is the media exaggerating the health risks of a third runway?

What we have here is a classic case of a headline statistic that contradicts the numbers cited later on in the same article. 

According to the Telegraph headline and the first paragraph of its article, researchers have concluded that the number of deaths related to air-pollution would treble if a third runway were built at Heathrow. We learn that the number of deaths currently stands at 50 per year and is projected to increase to 150 per year by 2030. 

However, in the paragraph immediately following this statement there is an important qualification: "Even if the new runway is not built, the number of deaths will double to 110 a year by 2030".

In other words, third runway or no third runway, there will be at least 110 deaths per year from air pollution by 2030. This means that a third runway at Heathrow would be responsible for an extra 40 deaths per year, not an extra 100 deaths. 

The Independent has simply repeated the Telegraph's headline without acknowledging the caveats that are attached to the report's statistics. 

Where are the numbers from?

The source for the newspaper articles is a survey conducted by the Massachusetts Institute of Technology (MIT) and Cambridge University. Scientists from these universities have attempted to predict how air quality in London would be affected by the building of a third runway at Heathrow, or the construction of a new airport in the Thames Estuary.

The researchers have used Department for Transport air traffic forecasts to model the health impacts of each scenario. The DfT has produced statistics for "constrained" growth (assuming no third runway at Heathrow) and "unconstrained" growth (assuming a third runway is built).

The scientific paper is due to be published in the journal Atmospheric Environment.

Why fuss over the details?

The Coalition has pledged not to build a third runway at Heathrow during this Parliament, but is under increasing pressure from business leaders to perform a U-turn. Meanwhile, Mr Johnson's team say that they're "keen to examine this latest research" that appears to lend support to the idea of Boris Island.

The stand-off is set to continue in the months to come, with both sides eager to prove that their proposal makes the most sense - for the economy, for the environment and for public health. We must hope that all parties interrogate the data in this latest report, rather than campaigning off the back of misleading media straplines.

Flickr image courtesy of Route79.