[Linkage of environmental and health data: health risk analysis of the Rio de Janeiro water supply by using geographical information systems].

Exposure assessment of population groups is based on linkage of environmental and health data. This relationship can be hard to establish due to spatial and temporal lags in data sets. Environmental data generally refer to scattered sampling points, while epidemiological data integrate periods of time within administrative territories. GIS can be used as a basis for organizing health-related and environmental data sets. We examined potential health risk in the Rio de Janeiro city water supply based on the overlay of information layers containing data on the presence and quality of water supply services. We used census tracts as the primary georeferenced data, since they contain information on how households are supplied, water supply pipes, sources, and reservoirs, and water quality according to the monitoring program. Population groups exposed to risks were located and quantified using spatial operations among these layers and adopting different risk criteria. The main problems related to water supply are located on the northern slope of the Tijuca Mountain Range (involving the absence or poor quality of water) and in the western area of the city of Rio, where the population relies on alternative water supply sources. The different origins, objectives, and structures of data have to be analyzed critically, and GIS can be used as a data validation tool as well as an instrument for detailed identification of inconsistencies.