Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light. The International Dark-Sky Association(IDA), "The Light Pollution Authority," defines light pollution as:
It obscures the starsin the night skyfor citydwellers, interferes with astronomicalobservatories, and, like any other form of pollution, disrupts ecosystemsand has adverse health effects. Light pollution can be divided into two main types: 1) annoying light that intrudes on an otherwise natural or low-light setting and 2) excessive light (generally indoors) that leads to discomfort and adverse health effects. Since the early 1980s, a global dark-sky movementhas emerged, with concerned people campaigning to reduce the amount of light pollution.
Light pollution is a side effect of industrialcivilization. Its sources include building exterior and interior lighting, advertising, commercialproperties, offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialized, densely populated areas of North America, Europe, and Japanand in major cities in the Middle Eastand North Africalike Cairo, but even relatively small amounts of light can be noticed and create problems. Like other forms of pollution (such as air, water, and noise pollution) light pollution causes damage to the environment.