Agency (EPA) as needing standards on a national level. In most cases, they are
the products of the combustion of fossil fuels or industrial processes.
CARBON MONOXIDE (CO)
Carbon monoxide is a colorless, odorless, and tasteless gas that is slightly less
dense than air. Carbon monoxide is produced from the partial oxidation of
carbon-containing compounds and forms when there is not enough oxygen to
produce carbon dioxide, such as when operating a stove, a water heater, or an
internal-combustion engine in an enclosed space.
Carbon monoxide is present in small amounts in the atmosphere, primarily as
a product of:
■ Volcanic activity
■ Natural and man-made fires, such as wildfires and burning crop residues
■ The burning of fossil fuels
■ Photochemical reactions in the troposphere (largest single source)Carbon monoxide is a temporary atmospheric pollutant in some urban areas,
primarily produced from the exhaust of internal-combustion engines but also
from incomplete combustion of various other fuels (e.g., charcoal, coal, natural
gas, oil, propane, trash, and wood). Carbon monoxide, in the presence of
oxygen, nitrogen dioxide, and ultraviolet radiation, also produces tropospheric
(ground level) ozone, a component of photochemical smog:
CO + 2O 2 + uv* → CO 2 + O 3
*ultraviolet radiationMethods to reduce carbon monoxide pollution include:
■ Requiring catalytic converters on all cars worldwide; however, this only
converts carbon monoxide to carbon dioxide—a greenhouse gas
■ Building more public transportation infrastructure
■ Switching to renewable energy sourcesLEAD (Pb)
Lead is used in building construction, lead-acid batteries for vehicles, bullets and
shot (which are ingested by wildlife), fishing weights, solder, and shields for
radiation. Tetraethyl lead (a gasoline additive) was phased out in the United
States starting in 1975 to meet tighter emissions regulations in an effort to reduce
toxic pollution.