Edmonton, the capital of Alberta, ranked as the Canadian city with the highest average annual levels of fine particulate matter in 2010, with levels similar to those of Chicago, almost three times its size. (scientificamerican.com)
WHO recommends a maximum level of particulate matter of 20 micrograms per cubic metre, yet major cities such as Cairo, Delhi and Beijing are on average far beyond this limit. (chimalaya.org)
The most recent example of this is a report published in the New England Journal of Medicine looking at 12 years of Medicare beneficiary data, which showed the risk of death increased in proportion to the amount of fine particulate matter in the atmosphere. (sciencedaily.com)