The role of the assessment of spatial variation and clustering in environmental surveillance of birth defects.

This paper discusses the role of small area spatial analysis of birth defects in environmental surveillance. Two approaches are reviewed: (1) the investigation of identified geographically localised potential environmental hazards, and (2) the detection of clustering. Examples are given where these 2 types of investigation have been used in the follow-up of individual clusters. Finally, it is argued that environmental surveillance, incorporating the 2 groups of spatial methods, should become a part of public health practice on both proactive and reactive basis.