Environment pollution: Light pollution

Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.
This approach confuses the cause and its result, however. Pollution is the adding-of/added light itself, in analogy to added sound, carbon dioxide, etc. Adverse consequences are multiple; some of them may be not known yet. Scientific definitions thus include the following:
Alteration of natural light levels in the outdoor environment owing to artificial light sources.
Light pollution is the alteration of light levels in the outdoor environment (from those present naturally) due to man-made sources of light. Indoor light pollution is such alteration of light levels in the indoor environment due to sources of light, which compromises human health.
Light pollution is the introduction by humans, directly or indirectly, of artificial light into the environment.
Light pollution obscures the stars in the night sky for city dwellers, interferes with astronomical observatories, and, like any other form of pollution, disrupts ecosystems and has adverse health effects. Light pollution can be divided into two main types: annoying light that intrudes on an otherwise natural or low-light setting and excessive light (generally indoors) that leads to discomfort and adverse health effects. Since the early 1980s, a global dark-sky movement has emerged, with concerned people campaigning to reduce the amount of light pollution.