Actual water pollution often vastly higher than calculated, European research on pesticide approvals shows

Pesticides sprayed onto fields are, for example, flushed by rain into rivers and oceans. In larger amounts they lead to the demise of flora and fauna: the bio-diversity suffers substantial damage. Within the scope of a legally established approval process the EU is therefore seeking to determine the effects of pesticides. Since the end of the 1990s mathematical simulation models (FOCUS models) have been used to predict the concentrations in water resources which arise due to the use of pesticides in agriculture. In Europe, a pesticide can be approved only when the predicted concentrations are below the ecologically critical effect thresholds. However, until now the agreement of the predictions with practice has never been thoroughly validated.

Using the example of insecticides which are particularly toxic for most animals living in water, the Institute for Environmental Sciences in Landau has now put this process to the test. In 122 cases the measured values were compared with the predicted values. The result is alarming: there is no statistical and not even any apparent relationship between the values. In up to four of ten cases the actual pollution of the water resources is higher than calculated. With newer insecticides, this quota is even greater.

"The results of the study clearly show that the calculation models in their current form are unsuited for the protection of water resources," states Professor Ralf Schulz of the Institute for Environmental Sciences at the University of Koblenz-Landau. "In view of these new results the risk assessment for many active substances approved in the EU must therefore be re-examined. This is the duty of the relevant approval authorities."

Besides faulty calculation models, other possible causes for the substantially higher values found in the field situation may be: failure of farmers to comply with regulations for the application of pesticides and insufficient instructions for use by the manufacturer. "Either the approval of insecticides or agricultural practice is subject to considerable errors -- presumably both," adds Schulz. "As permit owners, industry must meet its environmental obligations and play its part in clarifying the causes. In any case, in Germany also we need more independently derived data on the pollution of water resources in agricultural areas with pesticides."

As long as the actual causes remain unclarified, as a precautionary measure the environmental concentrations of insecticides predicted within the scope of the approval process should be increased by a factor of ten in order to adequately protect water resources. Furthermore, it is possible to require a buffer strip of five to ten metres between fields and water bodies not used for agricultural purposes. However, this was not included in the revision of the plant protection act in Germany at the end of 2011.

The current regulations for the approval of agricultural pesticide use in the EU was amended only in 2009 and, following this, incorporated in German national law by a new version of the plant protection act.