Good status is achieved when the concentration of perfluorooctane sulphonate (PFOS) in fish muscle is below 9.1 µg/ kg 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 list of priority substances under the Water Framework Directive (European Commission 2000, 2013). Good environmental status within 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 PFOS is below the threshold value of 9.1 µg/ kg fish muscle wet weight. The threshold value is an environmental quality standard (EQS) derived at EU level as a substance included on the list of priority substances under the Water Framework Directive.
EQSs are derived from ecotoxicological studies to protect freshwater and marine ecosystems from potential adverse effects of chemicals, as well as adverse effects on human health via 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 is the basis for the EQS. The EQS boundary for PFOS is based on the QS set for biota to protect human health (9.1 µg/ kg fish ww), defined for edible parts in fish.
For harmonization purposes the EC Guidance Document No. 32 on biota monitoring (the implementation of EQSbiota) under the WFD was developed (European Commission 2014). This guidance document recommends that the results from the monitoring should be standardized to represent fish at a trophic level of 4, which is an estimate of the general trophic level in commercial fish in Europe. The recommendation to obtain PFOS data in fish at a trophic level of 4 is to adjust the values from monitoring in accordance with trophic magnification factors and trophic level.
An alternative, secondary threshold value at 0.00013 µg/l is set for water. It is derived within the EQS process by using a bioconcentration factor and biomagnification factor for PFOS and represents the corresponding water concentration to the selected QS biota, secondary poisoning (PFOS EQS dossier, 2011). The secondary threshold value should only be used when it is not possible to evaluate an area using the primary biota-based threshold value.
Article 3 of the EU Directive on environmental quality standards (EQSD) states that also long-term temporal trends should be assessed for substances that accumulate in sediment and/or biota, such as PFOS (European Commission 2008a). A trend indicates if the status of the environment is improving and approaching the threshold value or if the status is deteriorating.