Persistence and Mobility (Defined as Organic-Carbon Partitioning) Do Not Correlate to the Detection of Substances Found in Surface and Groundwater: Criticism of the Regulatory Concept of Persistent and Mobile Substances

The Chemical Strategy for Sustainability (CSS) includes actions to ensure the protection of drinking water resources from chemical pollution. To proactively identify potential pollutants, the German Environment Agency (UBA) proposed the Persistent and Mobile (PM) concept according to which Persistence (criteria of REACH Annex XIII) and Mobility (log Koc < 4) would be proxies for a substance's degradation potential and transport velocity, two processes believed to drive the potential for contamination of surface and groundwater as drinking water sources. Two studies identified hundreds of PM substances while three subsequent studies have selected some of these substances for monitoring in surface, ground- and/or drinking water to support the concept. In the present work, the Persistence of the aforementioned substances was reassessed based on all experimental data publicly available. Depending on the exact study examined, it was found that 15 % to 40 % of the substances were erroneously concluded as P. The reinterpretation of the data indicates that a PM substance does not have a higher likelihood to be detected in surface or groundwater than a non-PM substance. In addition, the PM properties do not have any influence on the level of contamination. Twenty-six to 75 % of the substances selected because they were identified as PM were not found in surface or ground water despite being selected for their high emission pattern. Regulations based primarily on the PM concept, like the CLP and possibly REACH and UN-GHS, are unlikely to appropriately identify substances of concern for drinking water sources. It is more likely that chemical presence in surface and groundwater is driven by emission patterns or local factors. The development of specific exposure models would better contribute to the protection of drinking water resources and consumers.