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 a report saying that 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.
Of course, I'd hardly given the time of day to another report, weeks before, projecting the huge cost of transport links to a new airport. I have a bee in my un-soundproofed bonnet about aircraft noise.
Like thousands of central Londoners, I'm awoken before 5am several times a week, as flights muster over the Thames, queuing to land at Heathrow. It especially annoys me when people say that those living near airports know what they are getting. Central London is not Hounslow or Richmond.
But there was another reason why the report tweaked my interest. A few months before, I'd tried to find out whether anyone had compared "normal" air pollution levels in London with the level when volcanic ash grounded all planes in spring 2010. I had the impression at the time that those days were uniquely clear; that I didn't need to wash my hair so often; that general grime levels were lower. Were there figures to prove it?
I was put in touch with a team at University College London. They regretted that they had no answer. Air quality is only monitored, apparently, in the immediate vicinity of the airport, and any recorded difference had been negligible.
But now there seems to be an answer, if only a partial one, that at least chimes with common sense. The MIT/Cambridge study found that the wind mostly blows from north-east to south-west, so that pollution from Heathrow disproportionately affects the whole of London. I can imagine politicians and planners whispering that an extra 100 deaths a year is not so many in the greater scheme of things (though they wouldn't say it on record). But is air quality for the rest of us not an issue? And if it isn't, perhaps it should be.