During the last years, the human organism has been exposed to airborne pollutants to an increasing extend, among them the following most important: SO2, NOx , hydrocarbons, CO, photochemical smog, airborne particles containing the heavy metals lead and cadmium. The local effects on the lung and the bronchial mucous membrane are described including irritations of the mucous membrane and disturbances of the defence and elimination mechanisms. The main consequences are chronic bronchitis and bronchial carcinoma. The systemic effects of inhaled airborne pollutants are mutagenicity, cancerogenicity and toxicity. Disturbances of the immunological system may occur. Details as regard the effects of carbon monoxide, lead and cadmium, photochemical smog and SO2 are given.