March 13, 2017 by Becky Brown


There are currently 33 substances or groups of substances designated as priority substances (PS) under the WFD, for which environmental quality standards (EQSs) have been set and a further 8 substances with EQSs which are under the scope of Directive 86/280/EEC1. Good chemical status can only be achieved for a water body if concentrations of the PS are below their specific EQS. The European Commission (EC) has an obligation to review the current list of PS by the beginning of 2018, and to review the whole WFD process by 2019.

There are issues with the current approach of monitoring priority substances under the WFD. These include a lack of agreement over what substances should be prioritised (particularly regarding new substances), concerns that the prioritisation process is biased towards data rich substances like pesticides and metals rather than emerging substances of concern, and a lack of sufficiently sensitive analytical methods for some substances leading to low quality monitoring data2. There is also the long-standing issue that assessment based on single substances do not cover mixtures of substances that may be acting via a similar mode of action.

As part of the WFD review it has been suggested that the use of “effects based tools (EBT)” should be given consideration. The use of such approaches was recently reviewed in an EC report on “Aquatic Effects Based Monitoring Tools”3, and a number of recent publications have suggested deriving EQSs for groups of substances based on mode of action2,4. The types of in vitro assays that might be considered for monitoring purposes include those for oestrogenic substances, aryl hydrocarbon receptor binding, acetylcholinesterase inhibition, anti-cholinergic activity and possibly assays focusing on potential activities of pharmaceuticals including cox inhibitors or glucocorticoid activity. The approach is considered to align with the Marine Strategy Framework Directive (MSFD) under which a framework is currently being developed for using “trigger values” for biomarker and biological effect measures which, if exceeded, could be used to highlight specific sites or areas that are not considered to meet good environmental status (GES)5.

The use of EBTs does not have universal support and there are several issues with applying these techniques in a regulatory capacity. These include concerns that only a limited number of in vitro assays have been validated in inter-laboratory calibration exercises and usually not for surface water monitoring purposes. There needs to be guidance on the interpretation of the results from EBTs, for example through the development of trigger values for in vitro assays that can be linked to chemical pollution and ecological status. EBT’s do not give a definitive answer on cause and effect so a positive result in an in vitro assay will require follow up to understand which substance (or substances) are responsible for the observed effects. The nature of follow up work is not clear but it would be expected to include measurements for individual chemicals. In fact, EBTs (at least in the short term) would be unlikely to replace priority substance monitoring, since this is also used for setting discharge consents and permit values. Such concerns raise questions regarding the cost effectiveness of using “biological effect measures”.

More broadly, some leading scientists have questioned whether environmental risk assessment in general is shifting its focus too far to concerns regarding the mode of action of a substance while losing sight of the primary protection goal: healthy wildlife populations6. They suggest that efforts might be better placed monitoring aquatic wildlife diversity and abundance over time7.

In summary, a review of the WFD process should be holistic and consider both improvements to single substance assessments as well as potential complementary methods for determining good environmental status for our water bodies.

1 EC Website. 2017. Priority Substances and Certain Other Pollutants according to Annex II of Directive 2008/105/EC. Accessed 8th March 2017.

2 Brack W, Dulio V, Ågerstrand M, Allan I, Altenburger R, Brinkmann M, Bunke D, M. Burgess RM, Cousins I, Escher BI, Hernández FJ, Hewitt LM, Hilscherovák K, Hollender J, Hollert H, Kase R, Klauer B, Lindim C, López Herráez D, Miège C, Munthe J, O'Toole S, Posthuma L, Rüdel H, Schäfert RB, Sengl M, Smedes F, van de Meent D, van den Brink PJ, van Gils J, van Wezel AP, Vethaak D, Vermeirssen E, von der Ohe PC, Vrana B. 2017. Towards the review of the European Union Water Framework Directive: Recommendations for more efficient assessment and management of chemical contamination in European surface water resources. Science of the Total Environment. 576: 720-737.

3 CIS. 2014. Common Implementation Strategy (CIS) Technical report on aquatic effect-based monitoring tools. Technical Report - 2014 – 077

4 Busch W, Schmidt S, Kühne R, Schulze T, Krauss M, Altenburger R. 2016. Micropollutants in European rivers: A mode of action survey to support the development of effect-based tools for water monitoring. Environ Toxicol Chem 35:1887–1899

5 Lyons BP, Bignell JP, Stentiford GD, Bolam TPC, Rumney HS, Bersuder P, Barber JL, Askem CE, Nicolaus MEE, Maes T. 2017. Determining Good Environmental Status under the Marine Strategy Framework Directive: Case study for descriptor 8 (chemical contaminants). Marine Environmental Research. 124: 118-129.

6 Johnson AC, Sumpter JP. 2016. Are we going about chemical risk assessment for the aquatic environment the wrong way? Environ Toxicol Chem 35:1606-1609

7 Johnson AC, Chen Y. 2017. Does exposure to domestic wastewater effluent (including steroid estrogens) harm fish populations in the UK? Science of the Total Environment. 589: 89-96.