Toxicological and ecotoxicological assessment of water tracers

Uncertainties regarding possible negative effects on the environment or on human health of authorizing tracing experiments in groundwater and surface waters led to the establishment of a Working Group at the German Federal En vironmental Agency (Umweltbundesamt - UBA) for conducting a toxicological a nd ecotoxicological assessment. A total of 17 water tracers was assessed by the Working Group on the basis of the results of toxicological tests, the available literature, and the group's expert knowledge. In the future, trac ers that pose a risk to the environment or to human health should no longer be used. Nevertheless, there are a number of tracers that could be used in hydrogeological and hydrological investigations for water-pollution-contro l purposes with no adverse environmental impact.