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Summary |
In 1992 RWS started to measure micro contaminants in eel as part of the Biological Monitoring program for the Dutch fresh water bodies (MWTL). In 2003 the project is prolonged till 2007. Samples are collected from 14 locations of the Dutch fresh water bodies every year. Eel accumulates compounds from the water, the sediment and through intake. Lipophylic micro contaminants, like PCB’s and pesticides, are bound into the fat of the organism, while heavy metals are concentrated in the liver. Measurements of the bioaccumulation in eel provide in information about the bioavailability level of compounds in the food chain and the risk of cross contamination of higher organisms and for human consumption. |
| Results |
 Trends:
The concentration of micro contaminants in fish in the River Rhine and Delta area are for a period of 15 years now on such a high level that there is serious risk for fish eating higher organisms. In the River Meuse the risk is less serious and in the area of the lake IJsselmeer and the Randmeren the risk is low.
In the lake Ketelmeer between 1992 till 2004 there was a decreasing trend for the risk till below the average HC5 level of 100%, but in the years 2005 and 2006 the risk was increasing again until a level of light risk. Also the lake Volkerak shows an increasing trend from the year 2002 until 2006. The Twenthekanaal from 2001 until 2005 showed a risk below the average HC5 level of 100%, in 2006 it shows a considerable increase to light risk. In the lake IJ Amsterdam there was a considerable decrease of the risk after 1997, but after 2002 it shows again an increasing trend of the risk for fish eating higher organisms.
Norm values:
The MTR-value (Maximum Tolerable Risk) is the concentration level of a compound at which 95% of the species present in an ecosystem are protected.
The MTR-value for mercury was in 2006 above the norm for almost all measured locations, except for the River Meuse near Borgharen and Keizersveer and for the lake Eemmeer. None of the locations had values for mercury above the norms of the Commodities Act.
The MTR-value for the sum of pesticides was above the norm for 5 of the 14 locations: IJ Amsterdam, Hollands Diep, Volkerak, Rijn Lobith and Lek Culemborg.
It is expected that eels from the locations of the River Meuse near Borgharen and Keizersveer, IJ Amsterdam, Haringvliet, Hollands Diep, Volkerak, Rijn Lobith, and Lek Culemborg will be above the new consumption norm-value from the EU for dioxins and dlPCB’s which is valid on the 4 of November 2006.
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