Since the 1970's, in many industrial countries, the awareness of environmental health risks has led to set up information systems in order to assess and monitor concentrations of pollutants in air, water or food. These monitoring systems aim to answer the question: "is the environmental contamination too high?". With this objective, concentrations of pollutants are compared to standards. Up to now, this approach has been favoured and many environmental data have been collected at a local, regional, national or international level. Nevertheless, other approaches are possible as the health surveillance which aims to directly monitor the effects of contaminants on health. More recently, a third approach has been developed which consists in linking environmental monitoring data and health monitoring data. These approaches are not exclusive. All of them aim to produce useful information to help decision-makers in the management of environmental issues. However, the question is "what are the conditions to be achieved for routinely collected data to fulfil the requirements of a real Public Health surveillance system?". The conditions, advantages and limits of these three approaches are discussed.