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PCB transfer from river sediment to fish

The sale of equipment containing PCBs was forbidden 25 years ago, but the toxic substances have accumulated in a large number of French rivers and in the organisms living there. The work coordinated by Onema from 2008 to 2012 has improved our understanding of PCB transfer from sediment to fish.

The upper Loue river, in the Doubs department, is in good condition according to the criteria of the Water framework directive and is famous for the quality of its recreational fishing. But since January 2010, there have been two events of exceptionally high fish mortality, primarily trout and grayling, as well as small benthic species such a bullhead fish. At the same time, proliferation of toxic cyanobacteria was observed.

In the beginning of 2008, French authorities launched the national PCB* action plan in response to new European health standards governing the consumption of freshwater fish. Contaminated sediment plays a major role in contaminating freshwater fish and a major goal of the plan was to better understand PCB transfer from sediment to living organisms. To that end, Onema coordinated and funded a number of studies by Irstea. One of those studies, in a partnership with the RMC water agency, the Compagnie nationale du Rhône and the Rhône-Alpes and PACA regions, developed models on PCB bioaccumulation from sediment. The models identified a range of sediment-contamination thresholds (2.6 to 14 ng/g of PCBs in sediment) above which fish are no longer suitable for consumption. The two models tested on the Rhone river must now be validated in other environments.

Guidelines will be drafted in 2012 to set reference values for PCB concentrations in sediment, for use by water managers. They will serve notably to manage sediment-dredging operations in rivers. Little is known today about the impact of dredging operations on aquatic environments. To improve knowledge in the subject, Onema supports a number of projects at Ineris. A review of the literature, carried out in 2010 on case studies in France and abroad, confirmed the potential impact of dredging through resuspension of the PCBs in water. The review will contribute to determining general guidelines for dredging operations. Finally, in terms of methods, another project with Ineris developed innovative bio-analytical tools to quantify dioxins and certain PCBs in sediment. The tools are suitable for diagnostic and monitoring applications. Finally, a set of questions addressed to management organisations and scientific experts identified needs for improvements in environmental knowledge on PCBs and better management of the pollutant. Proposals for new R&D projects are now awaited in four major fields:
1) understanding and quantifying the sources,
2) assessing environmental risks,
3) environmental monitoring and
4) improving processing techniques for contaminated sediments.

* Polychlorinated biphenyls (PCB), commonly known in France as Pyralène, were widely used from the 1930s to the 1980s in manufacturing transformers, capacitors, pumps and turbines, as well as in the composition of oils, welding materials, adhesives and paints.


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