Air quality in Japan: where to check and what to do

Short answer. Check the Ministry of the Environment's monitoring site, Soramame-kun (そらまめくん), and your prefecture's website for alerts ¹. When PM2.5 is expected to exceed a daily mean of 70 µg/m³, the ministry's expert panel recommends that prefectures issue an advisory (注意喚起) ². On those days, cut prolonged strenuous exercise and time outdoors, and keep windows and ventilation to a minimum ².

Where can I check air quality right now?

The Ministry of the Environment publishes provisional real-time readings on its wide-area monitoring system, Soramame-kun, and links to each prefecture's own air-monitoring page, where detailed local conditions and advisories are posted ¹. PM2.5 is monitored continuously at more than 700 sites across Japan, run by local governments under the Air Pollution Control Act ¹.

What do the index levels mean?

Japan works with pollutant thresholds, not colour bands: Phaenyx found no single national air quality index for Japan like the US AQI.

The PM2.5 advisory is not a legal order, so no formal warning (注意報 or 警報) is issued for PM2.5 ². People with lung or heart disease, children and older people may be affected below 70 µg/m³ ². See Air quality index explained.

How polluted is the air on average?

Above the WHO guideline, but moderate. The population-weighted median of Japanese cities shows about 14 µg/m³ of PM2.5 (annual mean 2021-2023) ⁵, close to three times the WHO guideline of 5 µg/m³ ⁷. Nitrogen dioxide is about 12.1 µg/m³ ⁶, slightly above the WHO guideline of 10 µg/m³ ⁷. That NO2 figure is a regional background over roughly 80 km: a busy street will be higher. PM2.5 usually varies most and rises from winter to spring ².

What should I do on a bad air day, or with smoke or dust?

On high-PM2.5 days, cut prolonged strenuous exercise and time outdoors, and keep ventilation to the minimum needed ².

• High PM2.5: reduce prolonged strenuous exercise and going outdoors; indoors, keep ventilation and window opening to the minimum needed ². Sensitive people should watch for changes in their health ². See Pollution episodes and Sensitive people and polluted air.
• Masks: high-performance masks (N95 or Japan's DS1 grade and above) reduce PM2.5 intake, but only if they fit the face without leaks ². See Masks for smoke.
• Air purifiers: effectiveness depends on the model and filter; check the product's labelling ². See A clean-air room at home.
• Yellow dust (黄砂): dust from East Asian deserts can raise PM2.5 readings; take care when it arrives ². See Dust storms.
• Ozone: see Ozone days and Children and polluted air.
• Wildfire smoke: Phaenyx found no national smoke advice for Japan; see Wildfire smoke.

A household plan can list who in your home is sensitive to polluted air and where to shelter.

Frequently asked questions

Does Japan issue PM2.5 warnings?

Prefectures issue advisories (注意喚起) based on the ministry's 70 µg/m³ daily guideline; these are not legal warnings ².

What ozone level triggers a public alert in Japan?

An hourly photochemical oxidant value of 0.12 ppm or more, when weather suggests it will continue ³⁴.

Should outdoor events be cancelled on high PM2.5 days?

The ministry says sports days need not be cancelled unless levels greatly exceed the guideline; sensitive people should act more cautiously ².

Where do I find local advisories?

On your prefecture's air-monitoring page, linked from the ministry's PM2.5 page ¹. See also our Japan alerts page.