Old English broc garment for the legs and trunk; see breeches). The sense might reflect the breeches sense, on the notion of two limbs or of appliances used in pairs. The typographical bracket is first recorded 1750, so called for its resemblance to double supports in carpentry (a sense attested from 1610s). Senses affected by Latin brachium arm..
Carbon dioxide, a greenhouse gas, is the main pollutant that is warming Earth. Though living things emit carbon dioxide when they breathe, carbon dioxide is widely considered to be a pollutant when associated with cars, planes, power plants, and other human activities that involve the burning of fossil fuels such as gasoline and natural gas.
Pollution can be caused both by natural sources and humans. Volcanic eruptions are an example of natural sources of pollution. When a volcano explodes, it releases sulfur dioxide, carbon monoxide, solid particles, and other materials into the air at a much greater rate than is normally the case.ollution refers to situations in which some material or some form of energy occurs in larger quantity than can be tolerated by humans, plants, or animals without suffering some kind of harm. Probably the best-known forms of pollution are air and water pollution, which are discussed below.