The smallest particles, less than 100 nanometers (nanoparticles), may be even more damaging to the cardiovascular system.[39]
It has been demonstrated (Arden et al, JAMA Vol 287, p.1132-1141,2002) that an increase of 10micro g/m^3 causes an increase of overall mortality of about 1%. This figure was also used by EPA to estimate the number of death due to PM 2.5 pollution each year. If one has a life expectancy of 100 years, that means each 10 mic. g/m^3 of PM 2.5 would shorten one's life by one year.
The EPA has established an averaged level of 15 mug/m3 and instantaneous level of 35. The air quality of most US and European cities satisfy these guidelines.
The Chinese government has established future goals to reduce the PM 2.5 pollution to 50 by 2018 and 35 by 2020.
At this moment, PM 2.5 is about 300 in Bejing and 200 in Shanghai.