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AA-EQS (Annual Average EQS)
The annual average concentration of a substance in water that must not be exceeded to protect against chronic, long-term exposure.
Annual Average Environmental Quality Standard. Calculated as the arithmetic mean of concentrations measured at a representative monitoring point over a calendar year. Protects against chronic (long-term) ecological harm. All AA-EQS values in Directive (EU) 2026/805 are expressed in μg/L (micrograms per litre) unless otherwise stated.
Legal reference
Directive 2008/105/EC Art 4, as amended by Directive (EU) 2026/805