Spatial and temporal analyses of perfluorooctanoic acid in drinking water for external exposure assessment in the Ruhr metropolitan area, Germany

Abstract

Perfluorooctanoic acid (PFOA) and related chemicals among the per- and polyfluoroalkyl substances are widely distributed in the environment. Adverse health effects may occur even at low exposure levels. A large-scale contamination of drinking water resources, especially the rivers Möhne and Ruhr, was detected in North Rhine-Westphalia, Germany, in summer 2006. As a result, concentration data are available from the water supply stations along these rivers and partly from the water network of areas supplied by them. Measurements started after the contamination’s discovery. In addition, there are sparse data from stations in other regions. Further information on the supply structure (river system, station-to-area relations) and expert statements on contamination risks are available. Within the first state-wide environmental-epidemiological study on the general population, these data are temporally and spatially modelled to assign estimated exposure values to the resident population. A generalized linear model with an inverse link offers consistent temporal approaches to model each station’s PFOA data along the river Ruhr and copes with a steeply decreasing temporal data pattern at mainly affected locations. The river’s segments between the main junctions are the most important factor to explain the spatial structure, besides local effects. Deductions from supply stations to areas and, therefore, to the residents’ risk are possible via estimated supply proportions. The resulting potential correlation structure of the supply areas is dominated by the common water supply from the Ruhr. Other areas are often isolated and, therefore, need to be modelled separately. The contamination is homogeneous within most of the areas.