Vehicle emissions are a major source of air pollution in urban areas, contributing to high levels of pollutants such as nitrogen oxides, carbon monoxide, and particulate matter.

Oxygen is not a greenhouse gas, as it does not trap heat in the atmosphere like carbon dioxide, methane, and nitrous oxide.

Deposition is the process by which pollutants are removed from the air and deposited on the ground or water surfaces.

Air pollution has been linked to a variety of health problems, including respiratory problems, cardiovascular disease, and cancer. However, it is not known to improve cognitive function.

Smog is formed through a series of photochemical reactions involving sunlight, nitrogen oxides, and volatile organic compounds.

Natural ventilation is not a source of indoor air pollution, as it helps to bring in fresh air and remove pollutants.

Advection is the process by which pollutants are transported through the atmosphere by wind currents.

Ozone is a secondary air pollutant, formed in the atmosphere through chemical reactions involving sunlight, nitrogen oxides, and volatile organic compounds.

Transformation is the process by which pollutants are converted into less harmful substances through chemical reactions in the atmosphere.

Particulate matter air pollution has been linked to a variety of health problems, including respiratory problems, cardiovascular disease, and cancer. However, it is not known to improve lung function.

Emission is the process by which pollutants are released into the atmosphere from sources such as vehicles, power plants, and industrial activities.

Carbon monoxide is a primary air pollutant, emitted directly into the atmosphere from sources such as vehicles and power plants.

Diffusion is the process by which pollutants are mixed and diluted in the atmosphere due to the random motion of molecules.

Natural vegetation is not a source of outdoor air pollution, as it does not emit significant amounts of pollutants into the atmosphere.

Absorption is the process by which pollutants are removed from the atmosphere by plants and other organisms through their leaves, stems, and roots.