Environmental quality standards for water framework directive priority substances: challenges and opportunities

Area of Science:

• Environmental Chemistry
• Water Quality Management
• European Environmental Policy

Background:

• The European Commission has developed the Daughter Directive to establish consistent, science-based environmental quality standards (EQS) for priority substances in European surface waters.
• This initiative aims to protect and improve the ecological status of Europe's water bodies.

Purpose of the Study:

• To review the progress in deriving EQS under the Water Framework Directive.
• To identify remaining challenges and opportunities in setting environmental standards for priority substances.
• To discuss the appropriateness of current risk assessment methodologies and potential alternative strategies.

Main Methods:

• Analysis of the recently published Daughter Directive.
• Review of the progress in deriving EQS under the Water Framework Directive.
• Discussion of chemical risk assessment methodologies for water, sediment, and biota.

Main Results:

• The Daughter Directive sets annual average EQS for surface waters for 33 priority substances.
• No sediment standards are included; biota EQS are proposed for methyl-mercury, hexachlorobenzene, and hexachlorobutadiene.
• Key questions persist regarding the suitability of standard risk assessment for water column EQS and the inclusion of sediment/biota standards.

Conclusions:

• The directive represents significant progress in harmonizing water quality standards across Europe.
• Further research and discussion are needed on refining risk assessment and expanding EQS to include sediment and biota.
• Consideration of cross-cutting issues like cessation of discharges and member state flexibility in setting EQS is crucial.