also: ひかりがい
noun
light pollution
Excessive or misdirected artificial light that brightens the night sky and interferes with astronomical observation or ecosystems.
光害のせいで、都会では星がほとんど見えない。
Because of light pollution, you can hardly see the stars in the city.
天文台は光害を避けるために山の上に建てられた。
The observatory was built on a mountain to avoid light pollution.
Compound of 光 (light) and 害 (harm, damage). A relatively modern term for light pollution.