The number of installed vertical borehole heat exchangers is continuing to grow continuously which increases the risk of a local groundwater contamination with heat exchanger fluids due to a system leakage. This study evaluates the groundwater pollution potential of organic additives applied in heat exchanger fluids. In the first step of the project a data survey was carried out to collect detailed information about the identity, frequency of use and concentrations of the applied additives. In total, 35 different additives were disclosed by producers and/or distributors of heat exchanger fluids. The additives were classified as corrosion inhibitors, alkalis, dyes, solvents, scentsflavours, defoamers, and surfactants. The groundwater pollution potential of the additives was assessed based on their frequency of usage in the declared fluids and on their environmental fate (mobility, persistence and aquatic toxicity). Based on our analysis, the corrosion inhibitors benzotriazole, tolyltriazole, 2-ethylhexanoate, benzoate and sebacate exhibit a potentially exhibit a significant risk for groundwater contamination.