Most of the respiratory diseases or symptoms appear as the direct or indirect consequence of the inhalation of pathogenic agents present in our environment. The western way of life has been associated with a significant degradation of the quality of our air. Human beings are facing two types of pollution : industrial and domestic. Nitrous oxides, ozone and fine particulate matters are the most important pollutants. Numerous other agents may induce irritation or trigger allergy. Finally, tobacco smoke inhaled involuntarily may be dangerous both for children and adults. Pollutants emitted at home or present at the workplace may also be damageable for the respiratory health. The causal link between pollutants and respiratory disease or symptom is often difficult to demonstrate. This is why air pollution is usually not considered as the unique cause of a given disease but rather appears as a revealer of individual predisposing factors.