Microbiological parameters under the Drinking Water Directive.

In November 1998, the European Council adopted a directive, the Drinking Water Directive (DWD), concerning the quality of water intended for human consumption. It includes a certain number of microbiological, chemical or physical criteria or parameters to monitor, to ensure that i) it is “clean”, ii) the distribution network is safe and iii) to react promptly in case of contamination (Directive 98/83/EC)1. The Directive has been implemented by Member States, but its approach to monitoring quality at the point of consumption uses parameters determined over 20 years ago. After the submission of the European’s citizens’ initiative “Right2Water” to the Commission in December 2013, the Commission invited Member States to improve the access to a minimum water supply and the management of water in a sustainable manner. In 2017, following the WHO recommendations2, the Drinking Water Directive (DWD) was revised either for the microbiological or chemical parameters (RECAST DWD). Among the first ones, somatic coliphage (virus infecting Escherichia coli) has been proposed as new parameter, while bacterium Clostridium perfringens (C. perfringens) and its spores are already included in the Directive. The present report provides an overview on the current knowledge of these two microbiological parameters, their biological characterisations, relevance and suitability as indicators for human faecal contamination in the drinking water treatment. Finally, the report illustrates the available and standardised methods for their detection in water, listing as well the new and most promising ones with advantages/disadvantages and costs. Furthermore, the report provides a list of recommendations in order to elucidate the role of the two microbiological parameters for drinking water quality management.JRC.D.2-Water and Marine Resource

Modes of action of the current Priority Substances list under the Water Framework Directive and other substances of interest

The Water Framework Directive 2000/60/EC (WFD) has established a strategy for water protection that includes specific measures for pollution control to achieve good chemical and ecological status at European level. There is a need to review the approach to the current listing of priority substances (PS) under the WFD and to the current assessment of the chemical status, and consider eventually a wider range of chemical substances that could be covered in future monitoring programmes. Overall, the aim is to assess the water status more holistically and understand which the real effects are caused by the sum of the chemical substances present in the aquatic environment (including emerging pollutants /other substances of interest, metabolites and transformation products). The assessment of chemical status should be improved and linked with ecological status where relevant. Hundreds of different substances may co-occur, and even if most are present at very small concentrations they could exert a toxic effect on aquatic organisms (Carvalho et al. 2014) exposed for their entire life cycle and indirectly on human health (via food and drinking water consumption). Some of the substances in the current list of Priority Substances and in the first Watch List are considered in groups (e.g. brominated diphenylethers, neonicotinoid insecticides), but the overall approach to chemical pollution is otherwise based on the regulation of single substances. It has become increasingly clear that the risks from the vast number of chemical substances present in the environment cannot be adequately controlled on this basis. The Commission acknowledges the need to consider the potential toxic effects of mixtures of chemicals (EC COM(2012)252, 7th EAP). The challenge is to find a way of capturing a true picture of the chemical status of water bodies based on standards and methods that assess the presence of an adequate range of representative chemical effect types or modes of action (MoA), for example. The knowledge on the MoA is an important driver for linking exposure to chemicals to their effects in the aquatic environment, and therefore for development and application of the scientific methodologies for the assessment of combined effects of chemicals - the effect-based methods (EBM). The EBM, including biomarkers and bioassays, can target different levels of biological organisation in the aquatic environment, such as individual and/or sub-organism, community, and population levels (Carvalho et al. 2014, Ann-Sofie Wernersson et al. 2014). It is however much less clear how these EBM can be used to capture (predictively) the indirect effects that might occur in humans following long-term chronic exposure to pollutants via the aquatic environment. The use of effect-based monitoring approaches, complementary to chemical analysis, could allow assessing chemical status more holistically (rather than with a limited but ever-growing list of individual substances). The use of the EBM offers also the advantage of overcoming analytical difficulties (Kunz et al. 2015) and reducing monitoring costs by screening. To become a credible complement to chemical monitoring information, however, a better understanding of the capabilities and gaps of available EBM is needed. This report, based on a comprehensive literature study, reviews the current PS list and other substances of interest, considering their MoA(s). The review of data from the open sources clearly identified few groups of toxicological endpoints, with the majority driven by non-specific mechanisms (e.g. oxidative stress, activation of metabolizing / detoxifying pathways, histopathology, and others), and few groups with more specific biochemical / physiological pathways (photosynthesis inhibition, acetylcholinesterase inhibition, presence of PAHs metabolites, expression of metallothioneins). The majority of current PS and other substances of interest can be grouped, based on few common toxicological endpoints, and biomarkers are available for determining the concentrations and/or effects of some groups of substances. The identified biomarkers of effect seem to be however in general not very specific. There is clearly no “one size fits all” bioassay / EBM that could provide the toxicological potency of every PS and other substances of interest and their mixture toward all aquatic organisms in all water bodies, but rather a battery of bioassays that should be selected as “fit for purpose”. In addition, the present report allowed identification of uncertainty and inconsistency in observations, and thus identified areas where future investigations can be best directed. The present knowledge about MoA(s) remains limited, especially for the emerging substances of concern, such as pyrethroids and neonicotinoides.JRC.D.2-Water and Marine Resource

Testing comparability of existing and innovative bioassays for water quality assessment

The JRC led a consortium of seventeen research Institutes from eleven countries in EU and associated countries to evaluate the suitability of the current paradigm in environmental risk assessment that considers the risk of single chemicals for assessing water quality. Combined effects of chemical mixtures of concern were measured on different aquatic organisms and different levels of biological organisation using existing and innovative bioassays. Aquatic organisms in most European surface waters were exposed to many chemical pollutants simultaneously. However, the current paradigm in water quality assessment under the Water Framework Directive (WFD) still considers the effects of single substances instead of evaluating the combined action of environmentally relevant mixtures.The potential effects of combinations of chemicals are equally relevant to the risk assessment of consumer products and of drinking water to humans. In this EU-wide exercise, we could show that exposure to mixtures of dissimilarity acting substances at concentrations considered environmentally acceptable can exert significant effects on the biota. Therefore, chemical monitoring of a few substances may be insufficient to assess the quality status of water impacted by complex anthropogenic mixtures. The study highlighted an urgent need to revise methods and paradigms used to assess the safety of chemicals to the environment. Bioassays as part of a multi-tier approach to water quality monitoring can fill the gap between chemical and ecological assessments for a more holistic characterisation of water quality. Considering the upcoming revision of the WFD in 2019, it is timely to introduce the issue of risk posed by mixtures of pollutants into the discussion table and find innovative ways to assess water quality in a more holistic way than the mere assessment of biological and chemical indicators.JRC.D.2-Water and Marine Resource