Air pollutants can also cause inflammation, i.e. kill body cells or their function temporarily or permanently. If inflammation continued in the alveolar portions of the lung, not enough oxygen is transported into the bloodstream and emphysema will be resulted. Continued cell injury can alter cell type. For example, ciliated cells change to squamous epithelium will cause an uncontrollable growth of cells and destruction of adjacent normal tissue by compression and invasion and finally causes cancer. Cigarette smoking is the best known cause of lung cancer.
Studies using animal cells can indicate the ability of a new materials to cause mutation.
However, questions arise whether these results can be applied to human. The current standard of ozone pollutants is 120 parts per billion. Risk potecy will be estimated quantitatively in the second phase and decisions will be made on whether further controls are needed.