ABSTRACT - The National Institute for Public Health and the Environment (RIVM) proposes indicative water quality standards for a number of pesticides. Most of these substances are included in surface water monitoring programs, but quality standards are not available yet. This makes it difficult to evaluate water quality policy and to tackle problem substances. The new indicative standards give water managers a first impression of whether compounds are a reason for concern.
The RIVM has compared the proposed standards with monitoring data from 2017. Based on this, it is expected that almost half of the substances will not exceed the standards. This is uncertain for the other substances because there are no accurate data. A better analysis method is needed to detect acequinocyl, azadirachtin A, bifenazate, Pyridalyl and tribenuron-methyl at the level of the proposed standards.
The indicative standards include protection of humans that may be exposed to the substances when they eat fish and fish products. This is important for substances that can accumulate in fish or that may be harmful to humans. Nevertheless, the direct effects on aquatic organisms determine the the indicative standard in almost all cases. The derived value for the insecticide spirotetramat is uncertain, because there are no adequate tests for the substance.
Indicative water quality standards are derived using data from a limited number of databases and without thoroughly evaluating the underlying studies. Therefore, the uncertainty is higher than when following the full derivation procedure. Where the indicative standards are exceeded, a more detailed determination of the standard may help to determine the risks.
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