Many people live near point sources of air pollution such as industrial sites and waste disposal operations and there are often suggestions of clusters of disease around such activities. Such alleged clusters will generate significant public concern and media interest and in many cases will warrant detailed investigation. However, the ability of current epidemiological methods to investigate such clusters is limited, particularly with regard to obtaining reliable and accurate population exposure data. In many cases, the key question is whether releases from a point source result in a significant increase in exposure or whether other sources (background exposure) give rise to the dominant exposure. This review considers some of the issues around point sources including methods of estimating exposure and briefly discusses some of the epidemiological evidence linking respiratory disease and cancer with specific industries such as coking works and incinerators.