Public policy decisions are fuelled by information. Often, this information is in the form of statistical data. Questions stemming from public health and environmental concerns often arise or are studied within small subgroups of a population. Continuing improvements in the performance and availability of computing resources, including geographic information systems, and the need to better understand environmental exposures and consequent health effects create increasing demand for small population health and environmental data. These demands are at odds with the need to preserve the privacy and data confidentiality of persons, groups or organizations covered by the data. Although confidentiality issues for demographic and economic data are well-studied and are gaining maturity for health data, these issues are only beginning to emerge for environmental data and combined environmental-health data. The aim of this paper is to provide a framework for that examination. Herein we examine confidentiality problems posed by small population health and environmental data, summarize available statistical methods, and propose avenues for the solution of new problems.