Information on the exposures of the population to the environmental hazards of concern are essential in any environmental health impact assessment.   Ideally, these would come from direct measurement or monitoring of the population, either using biomarkers or by personal monitoring.   Unfortunately, this is rarely feasible, both because of the lack (and cost) of such monitoring, and because most assessments are concerned with situations that have not yet happened, or with past conditions which can no longer be directly observed.  In the absence of such data, recourse is therefore often made to environmental monitoring data.  Nevertheless, albeit to a lesser degree, these suffer from many of the same limitations: namely the sparseness of the data and their restriction only to existing and some past conditions.  As a consequence most assessments ultimately rely on some form of modelling to estimate exposures under the various scenarios of interest.

None of this is to mean that direct measurements of exposure, dose or environmental conditions (e.g. concentrations) are not valuable for integrated environmental health impact assessments.  In most cases, indeed, they are vital - either as inputs to models, or to validate models based on other predictors.   Such data, however, are rarely sufficient.  Most assessments also have to call on a range of other forms of environmental data, in order to estimate exposures and to model the way in which changes propagate through the causal chain.  Thus, data are typically required on a wide range of environmental factors, such as the topography, weather, soil, hydrology and land cover.

Traditionally, most environmental data were obtained by ground-based field surveys.  With the development of methods of remote sensing, however, airborne and satellite observations have become far more important, and these now provide the primary source for many types of environmental data.  As survey and monitoring technologies have advanced, so the range, size and complexity of environmental databases has grown.  Today, therefore, the main challenge is to find relevant data from the myriad of sources available, and to extract and combine them in an efficient way.

In Europe, the European Environment Agency provides an invaluable source of many data.  At national level, environmental ministries and their associated agencies also hold, or can give access to, a wide range of data.  Another valuable source, specific to environmental health, is the ExpoPlatform.  Factsheets for many of these data (along with selected data sets) are provided in the Environmental data section of the Toolkit, and these give links to many of the data sources.