The ecologic method in the study of environmental health. II. Methodologic issues and feasibility.

This paper reviews some methodological aspects of ecologic studies of human health, with emphasis on investigations of environmental quality. A recent census of Canadian and U.S. data sets potentially suitable for this type of study is summarized. It is concluded that despite the considerable utility of the ecologic design for this purpose, substantial practical difficulties are common in their implementation. Particular problems are the relative scarcity of relevant environmental data and complications associated with rendering them compatible with health data.