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.
There are two main types of pollution, point source pollution and nonpoint source pollution. Point source pollution comes from one source (you can easily point to it) like a factory or waste water treatment plant.