Cyclists should wear an effective air filter mask or better move away from the busy roads. That’s the conclusion I got when looking at the animated 3D ‘Pollution map’ video of London. The orange yellow color, mainly along the main roads, indicates high level of air pollution where the blue color are area with better air quality. It is intuitive to think air pollution level is higher along the main roads and lower away from the main roads, but I could never imagine the differences can be so huge!
In the short video below you can see the highest air pollution concentrated along the main roads and peak at the junctions, likely the result of slow moving vehicles there. Most of the area far away from the main roads are much better. Next time when I have to wait for the green light at busy intersection, I will hold my breath as much as possible.
The negative health effect of different pollutants are not the same. Amongst the pollutants, ultrafine particles (0.1-0.3 micros, currently not being regulated) can travel deep down into the lungs and stay longer there than their bigger brothers (PM10, >10 microns, PM2.5 >2.5 microns). According to WHO:
Some 3.7 million premature deaths annually are attributed to outdoor air pollution. About 80% of those deaths are due to heart disease and stroke, while another 20% are from respiratory illnesses and cancers related to exposure to fine particulate matter (PM2.5), the most health-harmful air pollutant.
Ultra fine particles clearly reduces the health benefits of physical exercise. There are increased evidence showing these ultra-fine particles are the silence killer closely links to respiratory and cardiovascular diseases. According to UCLA, the smaller the particles, the more toxic chemicals they are they are carrying. These very fine particles can travel deep into the lung. They stick to the lung and releases chemicals that damage the blood vessels and cause blood clogging plaques to form. The worst exposure is right next to the highway. Therefore, it is not a silly idea to wear a filter mask if your biking route have to go through busy traffic. However, do make sure two things, first the mask must form a good seal on your face, otherwise the pollutant will bypass the filters. Second make sure the filters are effective to block very fine particles, including those of 0.1 micron and PM2.5 (below 2.5 microns).