Public health surveillance involves the ongoing collection, analysis, evaluation, and reporting of health-relevant information to improve prevention. Surveillance of occupational health, like other public health endeavors, has been a powerful tool for tracking trends, evaluating the success or failure of interventions, and identifying new problems or the new circumstances where well-known problems are arising. Surveillance data can provide a measure of the extent of a problem and be invaluable in the allocation of scare prevention resources  . Surveillance systems often rely on information collected in administrative systems such as death certificates or hospital discharge diagnoses. Alternatively, surveillance can be active and case-based, depending on the recognition and reporting of particular conditions by health care providers or by a subset of volunteers. For example, in the UK, the Health and Occupation Research Network (THOR) system has provided useful information about trends in work-related and occupational lung diseases by engaging voluntary reporters from amongst the specialists in respiratory or occupational medicine  . In this issue of Respiration, Amar et al.  demonstrate both the feasibility and the value of analyzing data from the electronic medical records of general practitioners in order to better understand the incidence and temporal trends of the pneumoconioses in the UK.
Gregory R. Wagner, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115 USA