Dense Smog Over China (IMAGE) NASA/Goddard Space Flight Center Caption Dense smog, comprised of various pollutants, settled over the North China Plain on Feb. 20, 2011. Scientists have calculated the relationship between pollution and urban population. Image Credit: Credit NASA Goddard's MODIS Rapid Response Team Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.