Every spring, warmer temperatures and the beautiful ume plum blossoms come the less welcome waves of cedar pollen that make life outdoors very unpleasant for those susceptible to kafunsho and “Yellow Sand” that blows in from China. This year, the talk is all about PM 2.5 pollutants which complete a triumvirate of microscopic spring health risks.
PM 2.5 pollutants are airborne particles with a diameter of 2.5 micrometers or less, which means that the face masks that are now such a common sight in Japan provide little or no protection. It is thought that the particulates can be absorbed by the lungs and aggravate heart and even cause heart and lung diseases. Polluted air spreading from beyond China’s borders has caused a sharp rise PM 2.5 levels recorded in Japan.
At the end of last month, the Environment Ministry recommended that local governments broadcast alerts when levels exceed a daily average of 70 micrograms per cubic meter. This is double the the standard of 35 micrograms per cubic meter that the Ministry set back in 2009.
Its proximity to the Asian continent, puts Kyushu on the front line. In early February, the city of Fukuoka, announced that it would issue alerts if the average of PM 2.5 measurements taken at six locations in the city daily at 6am exceeded 39 micrograms per cubic meter. On Tuesday, with readings were as high as 110 micrograms in some places, Kumamoto Prefecture advised residents to stay indoors or wear masks if they went outside.
Here in Hiroshima, levels of 57 micrograms per cubic meter were recorded in Asaminami-ku at the beginning of this week and much higher levels were recorded in neighboring Yamaguchi Prefecture (Source [ja]). Hiroshima Prefecture will start issuing alerts when levels exceed 85 micrograms per cubic meter from tomorrow.
Hiroshima Prefecture has been measuring PM 2.5 levels since October last year at 10 locations. Hourly PM 2.5 levels can be seen here [ja]. PM 2.5 is 微小粒子状物質 (bishou-ryuushijyou-busshitsu) in Japanese and the relevant column is outlined in red in the screenshot below (click the image to see a larger readable version).