Tokyo, Japan Air Quality & Smog

Dominant pollutants, when pollution and smog are worst, a notable historical episode, and the official monitoring agencies for Tokyo, Japan — plus how to check the current reading. Tokyo reports air quality on the Japan’s air-quality standards — our full guide explains how that scale works and how it compares to the US AQI.

Dominant pollutants

Photochemical ozone (summer), NO₂, PM2.5.

Seasonal pattern: when smog is worst

Tokyo's air is clean for a megacity, the result of decades of pollution control since the severe "kōgai" episodes of the 1960s–70s. The main residual issues are summer photochemical-smog (ozone) advisories and spring PM2.5 that can be lifted by transboundary transport and Asian dust from the continent.

A notable air-quality episode

Tokyo's 1970s photochemical-smog crises spurred landmark Japanese pollution laws; in the early 2000s the metropolitan government's diesel-vehicle restrictions sharply cut airborne soot.

The local index and who runs it

Tokyo reports air quality using the Japan’s air-quality standards, not the US AQI — so the same air can read as a different number than you may be used to. Japan's Ministry of the Environment publishes readings through its "Soramame" network against national environmental standards; see our world air-quality indices guide for context.

• Japan Ministry of the Environment (Soramame system)
• Tokyo Metropolitan Government

How to check air quality in Tokyo

For the official live reading, the agency portals above are the canonical source. To understand what the numbers mean, start with our guide to the Japan’s air-quality standards and the broader comparison of world air-quality indices. Smog Report puts glanceable air quality on your iPhone — widgets, Live Activities, Siri, and Apple Watch — free and with no account.

Common questions about Tokyo air quality

Why does Tokyo have air-quality and smog problems?

Tokyo's air is clean for a megacity, the result of decades of pollution control since the severe "kōgai" episodes of the 1960s–70s. The main residual issues are summer photochemical-smog (ozone) advisories and spring PM2.5 that can be lifted by transboundary transport and Asian dust from the continent.

What are the main air pollutants in Tokyo?

Tokyo's dominant pollutants are photochemical ozone (summer), NO₂, PM2.5. The reading on any given day is usually driven by whichever of these is highest.

Has Tokyo had a major air-quality or smog event?

Tokyo's 1970s photochemical-smog crises spurred landmark Japanese pollution laws; in the early 2000s the metropolitan government's diesel-vehicle restrictions sharply cut airborne soot.

What air-quality index does Tokyo use?

Tokyo reports air quality on the Japan’s air-quality standards (AQI), not the US AQI — so the same air can read as a different number than you may be used to. For live, glanceable readings on your iPhone, the free Smog Report app auto-selects the right local index for wherever you are.

Related