A wind-tunnel experiment was performed to clarify the effect of local topography on the distribution of air pollution from a steel foundry in Armadale, central Scotland, under various conditions of air flow. The findings indicated that two areas, one directly to the southwest of the foundry and the other in the north of the town, were liable to receive pollution more frequently than had been expected. These observations were used to interpret the results of earlier investigations which had demonstrated relatively high concentrations of metal pollutants in areas of the town which also had surprisingly high mortality from lung cancer during previous years.