Priority Substances in Water

The Commission plans to impose further restrictions on certain chemicals used in biocides, pharmaceuticals and plant protection products in order to reduce their presence in European rivers, lakes and coastal waters.

This is happening through a revision of the Directive on priority substances in the field of water quality.

Some 15 chemicals would be added to the list of 33 pollutants that are currently monitored and controlled in EU surface waters, with pharmaceuticals proposed for the first time. Although the proposal does not question the medicinal value of these substances, it does address the potential harmful effects of their presence in the aquatic environment.

For six of the 15 proposed new substances - Dicofol, Quinoxyfen, PFOS, Heptachlor, HBCDD, Dioxin and Dioxin-Like PCBs - emissions to water would have to be phased out within 20 years.

This proposal is the outcome of a review that assessed the risks posed by around 2000 substances according to their levels in surface waters, their levels of production and use as well as how hazardous they are.


The Water Framework Directive (WFD) sets out a legal framework with the aim of improving water quality across Europe. The main objective of the WFD is to maintain water of lakes, rivers, streams and groundwater aquifers – into a healthy state by 2015.

The Environmental Quality Standards (EQS) Directive 2008/105/EC introduced further rules aimed at achieving the objectives set out in the WFD. The EQS Directive intended to set out environmental quality standards (EQS) for the substances contained in surface waters (river, lake, transitional and coastal) and adds to the WFD a list (contained in Annex X of the WFD) of priority substances.

The new proposal would update this list by adding as many as 15 new substances, and would also further tighten the existing environmental quality limits for these substances.

Priority Substances and Priority Hazardous Substances

There are currently 33 Priority Substances listed in Annex X of the Water Framework Directive (WFD). Member States are required to monitor their concentrations in surface waters and meet the Environmental Quality Standards (EQS) set for them within a certain timeline, unless they meet conditions that allow them to apply exemptions.

Priority hazardous substances are characterised by their Persistence (resistance to naturally degrading in the environment), Bioaccumulation, (their build up in the organism) and Toxicity (the degree to which a substance can damage a living or non-living organisms), or by an equivalent level of concern.

Due to their dangerous properties, emissions to water of these PBT substances are required by the WFD to be phased out within 20 years from the point where they have been defined by the EU rules as "priority hazardous substances".

New Priority Substances

The 15 new chemicals to be added to the list of 33 pollutants to be monitored and controlled in EU waters are: 
• Plant protection product substances: Aclonifen, Bifenox, Cypermethrin, Dicofol, Heptachlor, Quinoxyfen
• Substances used in biocidal products: Cybutryne, Dichlorvos, Terbutryn
• Industrial chemicals: Perfluorooctane sulfonic acid (PFOS), Hexabromocyclododecane (HBCDD)
• Combustion by-products: Dioxin and Dioxin-Like PCBs
• Pharmaceutical substances: 17 alpha-ethinylestradiol (EE2), 17 beta-estradiol (E2), Diclofenac

In addition, the proposed Directive would:
• Set out stricter environmental quality standards (EQS)for four existing priority substances and slightly revised EQS for three others
• Define two existing priority substances as priority hazardous substances
• Introduce biota standards for several substances
• Includes provisions to improve the efficiency of monitoring and the clarity of reporting with regard to certain substances behaving as ubiquitous persistent, bioaccumulative and toxic (PBT) substances
• Propose a Watch-List Mechanism that would allow EU-wide monitoring of substances that could pose risks for the future

Ubiquitous Persistent, Bioaccumulative and Toxic (PBT) Substances

Several substances that are persistent, bioaccumulative and toxic (PBT) are contained in the water environment. The majority of substances are either no longer allowed or restricted. However, some of them may still be authorised for specific uses, for which an appropriate substitute is not yet available, or due to the fact that some of the substances are being emitted from products that are still in use and were manufactured before the substances were regulated.

The proposed Directive would allow Member States to: (1) reduce monitoring for these substances. However, Member States would be authorised to reduce monitoring only if they already have enough information about the extent of pollution by these substances; (2) allow separate presentation by Member States of the concentrations of substances behaving as ubiquitous PBTs.

Watch List Mechanism and Priority Substances List

The proposal introduces the Watch List Mechanism which would include substances that possibly pose a threat over one or two years. Contrary to Priority Substances, the substances contained in the Watch List would not be subject to EU standards or phase-out obligations and they are not required to be closely monitored. The watch list should contain up to 25 substances or groups of substances. The information collected would feed into the potential future review of the Priority Substances list.


In order to comply with the proposed rules, Member States have the possibility to take those measures they consider the most appropriate ones based on their national economy. The impact assessment accompanying the proposal includes a number of examples, such as those related to the improvement of urban waste water treatment in certain areas.

According to the Commission, only some monitoring costs would occur for the additional substances, but they would be minor in relation to the existing overall monitoring costs. The proposal allows Member States to reduce the monitoring of certain substances that do not require close monitoring, and therefore to minimise the related costs.

Next Steps

The proposed Directive has been sent to the European Parliament and the Council for consideration following the ordinary legislative procedure. These Institutions will examine the proposal in the course of 2012.