| Summary: | On 31 July the company Chimac-Agriphar from Ougrée discharged 64 kilo chlorpyrifos and 12 kilo cypermethrin into the River Meuse, imposing risks to recreation (swimming and fishing), ecology (about 20 to 25 ton fish were killed) and drinking water production. In this study a retrospective risk analysis of this accidental spill was done in order to get more understanding of the risks on fish and drinking water production. The exposure is characterized through environmental concentrations of cypermethrin and chlorpyrifos estimated with the Meuse Alarm Model (MAM) at relevant locations in the Netherlands. Following acute toxicity (LC50), we calculated PAF of Atlantic salmon, brown trout and fish community with peak concentrations and 96 hour average concentration, while in the case of chronic toxicity (NOEC) PAF were calculated with 96 hour and 96x10 hour average concentrations. The results showed that the concentration (peak or average) adds uncertainties to the estimation of toxicity, especially when the concentrations are low (e.g. cypermethrin). For acute toxicity, when 96 hour average concentrations of cypermethrin were used, fish was not potentially affected, while with peak concentrations PAF reached values up to 37%. In the case of chlorpyrifos, PAF values were above 5% and up to 20% when peak concentrations were used and up to 10% with 96 hour average concentrations. For chronic toxicity, Atlantic salmon appeared to be seriously affected by cypermethrin (lower PAF 38%). The results for fish community showed a PAF above 5% at most of the locations. It can be concluded that the accidental spill of chlorpyrifos in July 2007 imposed a serious risk to the fish community on the short term (2-3 days) but less of a risk on the long term (40 days). The spill of cypermethrin imposed a serious risk in particular to Atlantic salmon on the long term, as a lower to medium risk to the fish community. With respect to drinking water production, the exceedance of the standards may lead to stops of the water intake: more ...
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