High levels of yellow sand and particle-laden smog known as PM2.5 are now being registered in some parts of the nation, creating misery for allergy sufferers and posing a potential hazard from prolonged exposure.

The first clouds of yellow sand were observed in Kyushu and Yamaguchi Prefecture on Sunday and Monday. On Tuesday, the Meteorological Agency reported that a westerly wind from China was bringing the sand to much of western Japan.

At times, visibility in the cities of Kobe, Matsuyama, Fukui and Tottori was reduced to between 5 and 10 km, while Kyoto and Osaka were also affected. Earlier in the week, visibility in the city of Nagasaki was reduced to about 6 km at one point because of the sand, the agency said.

Cumulative daily PM2.5 levels across Japan on Tuesday were declared to be low to moderately high, but Tokyo, Tokai and Shikoku were forecast to have moderately high levels Wednesday, while Kyushu was predicted to have high levels.

Japan has it easy compared with the Korean Peninsula, which this past weekend suffered extremely high levels of Chinese sand and PM2.5-laden smog. But the government has warned that levels in Japan may rise from late March to mid-April, a period when they have spiked in recent years.

PM stands for “particulate matter.” The 2.5 refers to airborne particles that are at least 2.5 microns in diameter — about one-thirtieth of the diameter of a human hair.

The particles are commonly found in smoke from fossil fuels or wood, and are created through the use of pesticides. The particles may contain nitrates, sulfates, organic chemicals, metals and soil dust, as well as pollen and mold spores. Heightened prolonged exposure can lead to respiratory ailments and possibly lung cancer.

The central government’s safety standard for PM2.5 exposure is a mean of 35 micrograms per cubic meter over a 24-hour period, and 15 micrograms per cubic meter annually. Health warnings are issued if levels reach 70 micrograms per cubic meter at any given time.

To learn, in Japanese, the latest levels of yellow sand and PM2.5 particulates in your area, view www.jma.go.jp/jp/kosa, or go to www.jma.go.jp/jp/kosafcst for a three-day forecast.

PM2.5 levels can be seen at pm25.jp, a privately run site that compiles data from each prefectural monitoring station and shows PM2.5 levels both in real time and the daily average. It has color-coded levels ranging from low to extremely high.

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