We are all familiar with images of Beijing citizens wearing masks, but do they work? Scientists from Edinburgh’s Institute for Occupational Medicine tested nine different masks bought from Beijing shops. Generally, the filter in each mask worked well, the best stopped over 99% of the particle pollution and the worst stopped 70% to 80%. Next, volunteers wore the masks in a test chamber filled with diesel exhaust. Pollution inside the mask was measured as they walked, nodded and talked. One mask stopped 90% of the particle pollution while others offered almost no protection. The tightness of fit was crucial. Facial hair prevents a good seal and the fit also depends on the shape of the user’s face. If it fits well then breathing through a mask is not easy. Wearing a mask could therefore pose problems for people who already have breathing or heart difficulties. So, face masks are not the answer to our problems. Walking alongside quiet instead of busy roads can help, and generally you will experience less pollution if you walk or cycle rather than sit in a car, but the best route to clean air is not masks. We need reduce the pollution in our cities.
