Preventing occupational and environmental lung diseases was discussed. The ability of the lung to act as a barrier to microorganisms, dusts, carcinogens, and other damaging agents was considered. The present situation regarding the risk of occupational and environmental lung diseases in India was considered. It was noted that despite large expenditures of money to protect against occupational and environmental hazards the Indian mining and chemical industries have created problems faster than they can be solved. Deposition, clearance, translocation, and retention of inhaled agents and their relation to pulmonary toxicity were discussed. The development of pneumoconioses, malignancies, and infectious diseases resulting from inhaling dusts depends primarily on the deposition and clearance of particles in the respiratory tract. Phagocytosis by alveolar macrophages by helping to prevent entry of deposited particles into the lung parenchyma plays an important role in clearing inhaled dust from the lungs. Continuous dust exposure can result in particles being retained in the lungs despite the clearance mechanisms. Accidental or sudden massive exposure, such as that resulting from a chemical accident, can overwhelm the equilibrium between deposition and clearance, thereby maximizing retention. Pathological states such as coal workers' pneumoconiosis, silicosis, and asbestosis and their relationship to dust inhalation were discussed. Preventing and treating occupational dust diseases was considered. All pneumoconioses and lung diseases can in theory be prevented by eliminating all dust exposures at the source; however, that is not possible on a practical basis. Although it is possible to halt the progression of lung fibrosis, the disease cannot be reversed. Attempts to prevent pneumoconioses with various drugs have shown mixed results. The prophylactic activity of Indian jaggery was discussed.