Comment: Toward a coordinated system for the surveillance of environmental health hazards.

The rapid increases in the numbers and quantities of chemicals released into the environment have been accompanied by a lack of adequate prerelease testing for adverse health outcomes. Environmental health surveillance is used both to track changes in exposures that are known to have adverse health effects and to identify previously unrecognized hazards. Surveillance data can directly aid in the design of interventions to reduce the level of hazardous agents in the environment or the opportunities for human contact with them. Components of an ideal environmental health surveillance system are discussed. For well-recognized hazards, databases related to exposure alone are adequate. However, for uncovering previously unrecognized associations, linkage between exposure and outcome databases that are collected or aggregated at the same geographic scale and for regions of relatively homogeneous exposures are needed.