Pollution - NORDIC LAke exposure to Cyclic Siloxanes: assessment of transport, distribution and fate

Cyclic volatile methyl siloxanes (cVMS) are used in personal care products, and are emitted to aquatic environments with wastewater effluents. With several reports documenting high concentrations in the aquatic environment, cVMS have come under extensive scrutiny by both national and international regulatory bodies regarding their environmental persistence and bioaccumulation. However, the understanding of the full link between emissions and biotic exposure is still fragmentary, including how environmental factors influence the environmental behavior of cVMS. Hence, the main objective of this project was to explore the behavior of cVMS using Lake Storvannet in Hammerfest as a case-study. An essential part of this was to also develop improved methods for analysis of cVMS in the environment, as well as to evaluate computer models to simulate the link between emissions and exposure for cVMS. Sewage from the population around Storvannet is emitted to the lake through leaking pipes and overflow events, which the local municipality is already addressing through renovation of the sewage system. The results from this project showed that concentrations of cVMS in sediments and fish in Storvannet are still comparable to concentrations in aquatic systems impacted by sewage from much larger populations (e.g. Lake Mjøsa and the Oslofjord). The cVMS concentrations were higher in Arctic Char than in Brown Trout from the lake, which may be explained by different habitats and dietary habits between these two species. Combination of the measured concentrations with computer models contributed to increase the understanding of how siloxanes may be impacted by low temperatures and ice cover. One of the main findings from the project was that siloxanes are expected to behave differently than well-known legacy contaminants in cold environments. While contaminants like PCBs partition more from water to sediments when it gets colder, increasing their persistence, siloxanes are expected to behave in the opposite way, possibly decreasing their persistence at colder temperatures. However, these predictions contain considerable uncertainty, highlighting both that we still lack basic knowledge on the properties of siloxanes, and that experience from legacy contaminants not necessarily can be directly transferred to new and emerging contaminants. The results from this project are highly relevant for both local, national, and international regulatory bodies, particularly as the use of the siloxanes D4 and D5 probably will be regulated within the EU in the near future. Results have thus been communicated to relevant environmental stakeholders. In addition, improved methods for analysis of siloxanes developed within this project have already been incorporated into monitoring activities for the Norwegian Environment Agency, and an upgraded bioaccumulation model will be utilized in new and upcoming projects financed by the Research Council of Norway.

Environmental emissions of cyclic volatile methyl siloxanes (cVMS) in Europe are estimated in the range of kilo-tonnes per year. With several reports documenting high concentrations in the aquatic environment, cVMS have come under extensive review by reg ulatory bodies within the Europe (REACH) and North America (Canadian Chemical Management Plan) regarding their environmental persistence, bioaccumulation, and toxicity. However, understanding their distribution and fate within the aquatic environment has been hindered by unreliable methods for determining trace levels in water and sediment matrices. In addition to this, environmental winter conditions in Nordic Regions may slow removal/degradation processes of cVMS and increase their persistence and exp osure in aquatic ecosystems. This proposal will develop sensitive methods for monitoring the distribution and exposure of cVMS and apply these new methods to a Nordic lake system. Data collected will be used to evaluate the capability of environmental fa te and transport models to predict the observed behaviour of cVMS under different environmental conditions. NILU is an international leader in cVMS research, and the only Norwegian laboratory that can conduct cVMS analysis, which has propelled Norway to the forefront of monitoring the fate and impact of these compounds. However, in order to maintain Norway's position as a leader in this research field, improvements to methodology is needed to enhance monitoring and model evaluations.