SCHEER - Scientific Opinion on "Draft Environmental Quality Standards for Priority Substances under the Water Framework Directive" - Diuron

SCHEER WG on Water Framework Directive
SCHEER members: Marian Scott (Chair), Marco Vighi (Rapporteur), Thomas Backhaus, Teresa Borges, Peter Hoet, Pim de Voogt, Rodica Mariana Ion
External experts: Andrew Johnson, Jan Linders
Contact:SANTE-SCHEERec [dot] europa [dot] eu (SANTE-SCHEER[at]ec[dot]europa[dot]eu)
On request from: European Commission
Adopted on: 12 October 2022

The dossier on Environmental Quality Standards for “Diuron” is reviewed by the SCHEER according to the general mandate on EQS dossiers.

The SCHEER agrees with the final MAC-QS_fw,eco = 0.27 μg L^-1 and MAC-QS_sw,eco = 0.054 μg L^-1, derived with a probabilistic procedure, on the basis of the data provided in the dossier. However, it is the opinion of the SCHEER that the availability of reliable data in the literature should be carefully checked.

The SCHEER accepts with reservations the deterministic AA-QS_fw,eco = 0.049 μg L^-1 and AA-QS_sw,eco = 0.0049 μg L^-1. The availability of reliable chronic data, including mesocosm studies, should be carefully checked.

For sediment ecotoxicity, the equilibrium partitioning procedure is applied, considering the scarcity of data. The SCHEER agrees with this decision. However, the SCHEER does not agree with the values derived in the dossier (AA-QS_sed,EqP,dw = 1 μg kg^-1_dw for freshwater sediment and 0.1 μg kg^-1_dw for marine sediment) as in this case the probabilistic results should be preferred, giving the results of QS_{sed,fw EqP} = 2.3 μg kg^-1_dw and QS_{sed,sw EqPdw} = 0.23 μg kg^-1_dw. It is the opinion of the SCHEER that the procedure is correctly applied. However, the availability of reliable sediment data should be carefully checked.

It is the opinion of the SCHEER that the procedures on secondary poisoning are properly applied. Therefore, the SCHEER endorses that secondary poisoning is not relevant for diuron.

For human health, the value of QS_biota,hh= 860 μg kg^-1_biota is calculated, using the ADI of 0.007 mg kgbw^-1 d^-1, proposed by EFSA (2005). The dossier does not calculate the QS_{water,hh-food} as the BCF is 2. The SCHEER endorses this conclusion.

For the exposure via drinking water, the SCHEER agrees with the adoption of the general drinking water standard for pesticides (QS_dw,hh = 0.1 μg L^-1).

The most critical EQS (in terms of impact on environment/health) has been identified as the AA-QS_{sw, eco} = 0.0049 μg L^-1.

Keywords:

Diuron, Water Framework Directive, environmental quality standards

Opinion to be cited as:

SCHEER (Scientific Committee on Health, Environmental and Emerging Risks), Final Opinion on Draft Environmental Quality Standards for Priority Substances under the Water Framework Directive - diuron, 12 October 2022.