Summary of symposium
Symposium organized by Kees van Gestel (VU) and Michiel Kraak (UvA) on behalf of the section Environmental Chemistry & Toxicology (KNCV/NVT-MCT) on Friday 16 September 2022 at the University of Amsterdam
The symposium was divided into three parts, on Exposure, Hazard and Risk.
The Exposure part of the symposium started with an overview by Leonard Oste (Deltares) of currently found PFAS concentrations in soils, groundwater, sediments, surface water and suspended matter. The number of PFAS detected depends on their properties (long- versus short-chained), but also on the method of analysis. Several sources were identified, and levels are expected to stabilize in the future, but the composition of the PFAS mixture may change with ‘old’ ones being phased out and replacements popping up. Mohammad Sadia (UvA) briefly discussed methods for producing PFAS and for removing PFAS from water. In drinking water, he measured many branched PFAS compared to other media, while the ultra-short PFAS like TFA dominate in groundwater and drinking water. Ioanna Gkika (UvA) presented preliminary results of a mesocosm study with sediment from a pond next to the 3M factory in Antwerp, in which she assessed PFAS bioaccumulation in plants, and from a field sampling of biota from the same pond. In both cases, many PFAS compounds were present, and they also showed rather high bioaccumulation factors in biota. In the general discussion on exposure, the high BSAF levels were further discussed in relation to trophic relations. It was concluded that such studies should try to measure as many PFAS compounds as possible, to obtain a better overview of the presence and concentrations of PFAS in the environment.
The Hazard part of the symposium was started by Jessica Legradi (VU), who reported on the toxicity and modes of action of PFAS in zebrafish determined by the use of different omics methods. Oxidative stress, effects on lipid metabolism and on the immune system seemed to be most relevant, while also behavior and development of the zebrafish may be affected. Lackson Kashobwe (VU) further explored the mechanisms behind the lipid metabolism effects of PFAS using cellular assays. Activation of PPAR receptors seems to be important in these mechanisms. Skylar Xie (VU) presented results of toxicity tests done by herself but also by colleagues (Cara Byns, Thimo Groffen) of the University of Antwerp. FBSA was much more toxic than PFBS, although both compounds were not very toxic to daphnids, but toxicity increased over generations. In the Asian clam, oxidate stress was seen at lower concentrations of PFAS. But in great tits from the area near the 3M factory in Antwerp, no clear effects of PFAS were seen on reproductive success, even though the eggs contained extremely high PFAS concentrations. In the presentation of Anna Huang (WUR), it was shown that aquatic insects like midge larvae are much more sensitive to PFAS than other aquatic invertebrates, but the reason for this big difference in sensitivity remained unclear. In the general discussion on hazard, it was concluded that immune responses and endocrine disruption also may be of importance for effects of PFAS. More studies are needed to unravel the possible relation between PFAS fate and effects and chemical properties/molecular descriptors. It was also advocated to apply the One Health approach to further investigate the effects of PFAS.
In the Risk part of the symposium Erik Verbruggen (RIVM) discussed the current EU approaches for the risk assessment of PFAS. A universal restriction of PFAS is proposed by several countries, which applies to all PFAS. For the risk of PFAS mixtures, a toxic potency factor approach is used, and this has resulted in the new Tolerable Weekly Intake (TWI) for 4 PFAS compounds set by EFSA. New RIVM guidance related to this, leading to an Environmental Risk Limit of PFAS In surface water of 7 pg/L has been published. This risk limit is frequently exceeded, nearly everywhere in the Netherlands. Joris Quik (RIVM) described how PFAS fate and exposure can be modelled. Major challenges relate to the detergent like behavior (foaming), transformation and partitioning of PFAS. Risk limits for soil and sediment for PFAS were discussed by Arjen Wintersen (RIVM). Point of departure for the risk limits is the TWI set by EFSA, and risk limits for soil may be differentiated based on the use of the soil (e.g., residential versus industrial). Since the TWI is only based on 4 PFAS compounds, more data is needed to develop risk limits for other PFAS.
In the vivid final plenary discussion led by Annemarie van Wezel (UvA), a co-worker of the Health Service Authority GGD Dordrecht expressed his concerns about the recent statements of some experts in news items on PFAS in Belgium and the rather strict risk limits for human health. It confuses him and he does not really know what to tell his patients. This made clear that in addition to risk assessment, also risk communication and risk management are crucial. The extremely low risk limits for human health also triggered the question whether further ecotoxicological research still is needed, as it seems unlikely to find organisms more sensitive than the currently maximum allowable concentrations. On the other hand, further research on the environmental fate of PFAS, including its bioaccumulation potential seems crucial for a proper assessment of exposure and therefore of its potential risk, also to human health. Finally, the audience was challenged to give their opinion about the future needs for PFAS research.
