Five GoodGym runners were given Middlesex University air quality monitors to assess the air quality around them as they moved about in the month of October. All of them reported interesting results he is what George had to say.

Air Quality Monitoring Mission Report from George

Collecting the data was really eye opening. Barnet Council's Air Quality Action Plan marks the North Circular and Tally Ho Corner as some of the most polluted parts of our borough, exceeding WHO limits on particulate matter. However, the times I went to those areas, air quality appeared relatively OK, perhaps due to the wet and windy weather, which reduces particulate pollution. (I also learned later that our monitoring devices don't measure nitrogen oxides, which is the main pollution type from road traffic!)

However, going near smokers dropped the air quality quickly. Also, going climbing (which I love!) put me in a chalk-dusty environment with poor air quality. But the most shocking part was going on the tube.

Open air platforms were fine, but going inside a train carriage lowered the air quality. Underground, the air quality quickly hit zero on the Northern, Piccadilly, Victoria and Bakerloo lines because of PM10 - the large pollution particles, or soot, which you can see all over the tube. 

And waiting on a platform, arriving trains brought clouds of dust that triggered massive spikes in pollution. The highest reading I got was when two trains came in almost back to back (the first up the Edgware branch, the second one I was waiting for).

The highest reading I got a screenshot of was over 500μg per cubic metre of PM10. The app's measurements only go up to 250μg per cubic metre. I can't imagine how bad that is for your lungs, but I'm now wearing a pollution-filtering mask whenever I travel underground.