SCHEER - Scientific Opinion on "Draft Environmental Quality Standards for Priority Substances under the Water Framework Directive" - Mercury and its compounds

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: 22 December 2022

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

In the dossier some sections are the same of a previous version (2005), based on the procedures proposed in an old Technical Guidance, other section have been updated. This produces some inconsistencies. The SCHEER recommends that the full dossier should be updated.

For the QS on water the added approach is proposed, based on the following equation:

QS_water = C_background + MPA.

It is the opinion of the SCHEER that, due to the lack of knowledge on natural background levels in most European water bodies, the approach cannot be applied. In particular, the approach applied considering only the default values of River Rhine cannot be accepted. Considering the need for update the derived values on the basis of the more recent Technical Guidance and toxicity data, it is the opinion of the SCHEER that the proposed MPAs should be proposed as provisional QS as follows:

MAC-QS_fw,eco = MAC-QS_sw,eco= 0.07 μg Hg L^-1

AA-QS _fw,eco = AA-QS _sw,eco = 0.047 μg Hg L^-1

The dossier considers that, for the time being, no reliable QS_sediment can be derived. The SCHEER agrees with this conclusion. However, it is the opinion of the SCHEER that the more recent Technical Guidance must be applied and that more efforts should be made for collecting data on sediment dwelling organisms.

The SCHEER endorses the QS_{biota, secpois, fw} = 11 μg kg^-1_ww, derived with the deterministic procedure, while the SCHEER does not endorse the QS_{biota, secpois, fw} derived with the probabilistic procedure and the back calculated QS_{fw, sec pois} due to inconsistencies in the calculations. The SCHEER endorses the QS_{biota, secpois, sw} = 0.36 μg kg^-1_ww and the back-calculated QS_{sw, biota} = 0.7 pg L^-1.

The SCHEER endorses the QS_{biota, hh} = 23 μg kg^-1_biota and the back calculated QS_{water, hh food}= 4.6 pg L^-1.

The SCHEER agrees with the decision of supporting the drinking water standard (DWS) of 1 μg Hg L^-1, of the Directive (EU) 2020/2184.

Among the QSs endorsed by the SCHEER, the lowest value endorsed by the SCHEER is the QS_{water, hh food}= 4.6 pg MeHg L^-1.

Keywords:

Mercury, 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 - mercury, 22 December 2022.