Volcanic gas carrying sulfur dioxide released from Mount Sakurajima in Kagoshima Prefecture is partly responsible for spikes in the level of the air pollutant PM2.5 in the Kanto and Tokai regions, according to the government's Meteorological Research Institute.
The institute ruled out pollutants from China as a factor. China along with factory smoke and car exhaust have so far been seen as the most likely sources of the hazardous fine particulate matter.
The Chiba Prefectural Government has also discounted pollutants from China as a factor behind the PM2.5 rise earlier this month in some parts of the prefecture. It points the finger at climate conditions that apparently drew PM2.5-laced air into the affected areas.