Air quality is considered to be satisfactory, and air pollution poses little or no risk.

Air quality is acceptable; however, for some pollutants there may be moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Increased likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly.

Increased aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; increased respiratory effects in the general population.

Significant aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; significant increase in respiratory effects in the general population.

Significant aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; signifigant increase in respiratory effects in the general population.