Thresholds and Status evaluation

Good Status is achieved if the concentrations of metals are below the specified threshold values boundary of (Thresholds figure 1).


Thresholds figure 1. Good status is achieved if the concentrations of metals are below the threshold values listed in Good status table 1.


The threshold values for metals are based on Environmental Quality Standards (EQS) for water and biota (Thresholds table 1) which have been defined at EU level for substances included in the priority list under the Water Framework Directive, WFD (European Commission 2000, 2013). The threshold can only be evaluated if concentrations are measured in the appropriate matrix. For historical reasons, the countries around the Baltic Sea have differing monitoring strategies. As a pragmatic approach, a threshold value is defined for primary matrix for each metal. However, if suitable monitoring data is not available in a region to evaluate the primary threshold, then the secondary threshold value can be used for the evaluation of alternative matrices (Good environmental status table 1). Under the WFD, Member States may establish other values than EQS for alternative matrices if specific criteria are met (see Art 3.3. in European Commission 2008a, revised in European Commission 2013).


Thresholds table 1. Threshold value for the included metals (EQS – Environmental Quality Standard, AA- Annual Average Concentration, QS – Quality Standard, BAC = Background Assessment Criteria).

Threshold values 
AA 0.2 µg l-1
EQS waterSediment2.3 mg kg-1 d.w.QS sediment[1]
Mussel960 µg kg-1 d.wOSPAR BAC
MercuryFish, mussel20 µg kg-1 wwEQS biota secondary poisoning---
Lead ​ ​Water ​ ​
AA 1.3 µg l-1 ​ ​EQS water ​ ​Sediment120 mg kg-1 d.w.QS sediment[1]
Mussel1300 µg kg-1 d.wOSPAR BAC
Fish26 µg kg-1 w.w.OSPAR BAC

[1] Applies to freshwater sediment (standard for marine sediment is currently not available). Sweden however considers this standard to be applicable also for assessment of the marine environment.