Long-term (2005Long-term ( −2015 tropospheric nitrogen dioxide (NO 2 ) column data recorded by the satellite-borne Ozone Monitoring Instrument (OMI) in East Asia were analyzed to investigate annual trends on an national basis and their potential causes. We found an evident decrease of 6% year −1 in the NO 2 level over China after 2011. The grid-basis trend analysis implies that the rapid decrease occurred on a provincial or larger spatial scale and was likely due to a nationwide action such as the widespread use of denitrification units. In Japan and South Korea, a turnaround indicating an increase was observed after 2013 and 2012, respectively. As a consequence, the tropospheric NO 2 pollution level in East Asia was found to be recovered to the 5-year-ago level in 2015.