Beware of photochemical smog

Nitrogen oxides and other substances emitted into the atmosphere from factories, workplaces, automobiles, etc. undergo chemical reactions with the ultraviolet rays contained in sunlight and become substances called "photochemical oxidants." This is not diffused into the atmosphere and remains, causing the sky to become hazy and look like a white mist.

Please be aware that photochemical smog is more likely to occur on days from June to September when the sun is strong, the temperature is high, and the wind is weak. It may irritate the eyes and throat, causing symptoms such as stinging in the eyes and a sore throat. When information regarding photochemical smog is provided, please take sufficient precautions to avoid health hazards from photochemical smog, such as by refraining from outdoor activities as much as possible.

The Tokyo Metropolitan Government Bureau of Environment will send out information such as photochemical smog warnings by email when the oxidant concentration at the standard measurement point exceeds the emergency warning standard. For more information, please see below.