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

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: 15 December 2022

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

The proposed dossier is a revision of a previous EQS dossier (2015) based on recent data and the procedure proposed in the new EQS Technical Guidance (2018). However, several sections of the dossier refer to old technical documents (2003, 2004). It is the recommendation of the SCHEER that other sections also be updated, in line with the 2018 EQS Technical Guidance.

Moreover, all effect data used are older than 2005. This seems in contradiction with the statements of the dossier.

The AA-QS_{fw, eco} =0.44 μg HCBD L^-1 is calculated with the deterministic procedure. The SCHEER endorses the value.

The QS_SPM.fw and QS_SPM.sw are calculated using a formula taken from an old (2004) EQS Manual that allows calculation of a QS as concentration in the SPM (QS_SPM), while the 2018 Guidance allows calculation of a QS as total concentration (dissolved + bound to SPM). The SCHEER suggests revising using the more recent guidance.

A MAC-QS_{fw, eco} =0.59 μg L^-1, derived with the deterministic procedure is endorsed by the SCHEER.

The QS_sediment is calculated using the equilibrium partitioning method with procedures taken from an old (2004) EQS Manual. The SCHEER suggests revising using the more recent guidance.

It is the opinion of the SCHEER that the procedure used for the calculation of secondary poisoning is based on an inappropriate NOAEL therefore, the SCHEER suggests revising the whole calculation with an adequate NOAEL.

The QS_{biota, hh food} = 24.53 μg.kg^-1_biota (rounded to QS_{biota, hh food} = 25 μg.kg^-1_biota) and the QS_{water,biota hh} = 1.1 ng L^-1 are endorsed by the SCHEER.

It is likely that the most critical EQS is the QS_{water, hh water} = 1.1 ng L^-1, unless a lower QS will result from the revision of the QS for secondary poisoning.

Keywords:

Hexachlorobutadiene, HCBD, 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", Hexachlorobutadiene, 15 December 2022.