Good status in biota is achieved if the concentration of hexabromocyclododecane (HBCCD) is below the threshold value of 167 µg kg-1 fish wet weight (Thresholds figure 1).
The threshold value is an environmental quality standard (EQS), derived at EU level as a substance included on the priority list under Directive 2008/105/EC regarding priority substances in the field of water policy (EQSD) (European Commission 2008a). Good status in accordance with the MSFD is defined as 'concentrations of contaminants at levels not giving rise to pollution effects'.
Thresholds figure 1. Good status is achieved if the concentration of HBCCD is below the threshold value of 167 µg kg-1 fish wet weight. The threshold value is an environmental quality standard (EQS) derived at EU level as a substance included on the priority list under the Directive on Environmental Quality Standards.
The EQS values are derived from ecotoxicological and toxicological studies to protect freshwater and marine ecosystems from potential adverse effects of chemicals, as well as protection of human health in connection with consumption of drinking water and food from aquatic environments. Quality Standards (QSs) are derived for different protection goals, i.e. pelagic and benthic communities, top-predators in these ecosystems, and human health. The most stringent of these QSs are the basis for the EQS. The EQS boundary for HBCDD is based on the QS set for biota, to protect from secondary poisoning, defined for prey tissue, i.e. fish whole body. For harmonization purposes, the EC Guidance Document No. 32 on biota monitoring (the implementation of EQSbiota) under the Water Framework Directive was developed (European Commission 2014). This guidance document recommends that for lipid soluble, biomagnifying compounds such as HBCDD the fish assessed for EQS compliance should be at a trophic level of 4.5 for marine environments with a whole body lipid content of 5%. The aim of the recommendation is to obtain comparable monitoring data. The results in the indicator have been adjusted in order to represent a lipid content of 5 % however no adjustment to a trophic level of 4.5 has been done.
An alternative, secondary threshold value at 170 µg kg-1 dry weight (dw) is set for concentrations in sediment. It is derived within the EQS process and is a QS in sediment, set to protect the marine benthic community. The secondary threshold value should only be used when it is not possible to evaluate an area using the primary biota-based threshold value.
The technical HBCDD products consist of three stereoisomers, α-, β- and γ-HBCDD, but the QS and EQS values are derived for the sum of these three stereoisomers. More detailed information concerning the derivation of the threshold value can be found in HBCDD EQS dossier (HBCDD EQS dossier 2011).
Article 3 of the EQSD states that long-term temporal trends should also be assessed for substances that accumulate in sediment and/or biota, such as HBCDD. A trend indicates if the state of the environment is approaching the threshold value or if the state is deteriorating.