An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Community Multiscale Air Quality Modeling System (CMAQ)

Trends in Air Pollution Exposure Using CMAQ

CMAQ simulations have been analyzed to investigate the historical trend in the long-term exposure to PM2.5 and PM2.5-related premature mortality (PM2.5-mortality) and its response to changes in emissions that occurred during 1990-2010; and to examine implications for future trends in human exposure to air pollution in both developed and developing regions of the world. Results indicate that while in East Asia and South Asia PM2.5-mortalities increased by 21% and 85% respectively, in Europe and North America they decreased substantially by 67% and 58% respectively. Additional health benefits from air pollution controls occur when the positive correlation between population and air pollution exposure weakens, as witnessed in Europe and North America over past two decades.

Graphs showing trends in population exposure to ambient PM2.5 in East Asia and North AmericaContrasting trends in population exposure to ambient PM2.5: Control measures have significantly reduced exposure to high levels of PM2.5 in North America, but uncontrolled growth has resulted in larger populations being exposed to higher PM2.5 in many parts of Asia.

Analyses of model results also show that though the fine particle induced cooling partially offsets the greenhouse gas warming, the associated reductions in atmospheric ventilation lead to air pollutants becoming more concentrated locally, especially in highly polluted and populated regions. Thus control measures aimed at reducing PM2.5–related mortalities, result in unexpected additional benefits, making the controls even more effective than originally projected.

Maps showing mortality changes resulting from aerosol radiative effects on Temperature (left) and combined Temperature and PM2.5 (right)Mortality changes resulting from aerosol radiative effects on temperature (left) and combined temperature and PM2.5 (right).


Wang, J., Xing, J., Mathur, R., Pleim, J., Wang, S., Hogrefe, C., Gan, C.-M., Wong, D., & Hao, J. (2016). Historical trends in PM2.5 related premature mortality during 1990-2010 across the northern hemisphere, Environ. Health Perspect., doi: 10.1289/EHP298 Exit

Xing, J., Wang, J., Mathur, R., Pleim, J., Wang, S., Hogrefe, C., Gan, C.-M., Wong, D., & Hao, J. (2016). Unexpected benefits of reducing aerosol cooling effects. Environ. Sci. & Technol., 50(14), 7527-7534. doi: 10.1021/ Exit