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.ulfur oxides, oxides of nitrogen, and carbon monoxide are chemical compounds. Particulate matter and volatile organic compounds are groups of related pollutants. The term particulate refers to tiny specks of solid matter in the atmosphere, including smoke, haze, aerosols, and tiny particles of carbon.