Which among these is/are the most common site of injury by airborne pollutants?

When inhaled air pollutants affect the lungs and respiratory tract first but can also be taken up and transported by the bloodstream throughout the body. As respiratory tract is the major entry point of air pollutants, many respiratory diseases including lung cancer are often linked to air pollution. The respiratory system is particularly sensitive to air pollutants because it is made up of a mucous membrane covering its internal surface. The lungs are designed to absorb large amounts of air in close contact with the bloodstream and facilitate the transport of oxygen. The cells of the lung tissue can be damaged by air pollutants such as ozone, metals and free radicals.