ReviewMonitoring, sources, receptors, and control measures for three European Union watch list substances of emerging concern in receiving waters – A 20 year systematic review
Graphical abstract
Introduction
Water is an essential resource, crucial to all living organisms and for a diversity of human activities (Barbosa et al., 2016). Drinking and food preparation, support of the natural environment and a growing economy all require a healthy and secure water supply (Rowan, 2011). Unfortunately, there are significant pressures on this fragile resource. Natural and along with other anthropogenic substances such as pharmaceuticals, pesticides, industrial compounds, personal care products, steroid hormones, drugs of abuse and others, end up in surface water, ground water and vital drinking water (Ribeiro et al., 2015) Specifically, this review focuses on monitoring, sources, receptors and control measures for addressing the pharmaceutically-active compounds diclofenac (DCL) and the synthetic hormone 17-alpha-ethinylestradiol (EE2) along with the natural hormone 17-beta-estradiol (E2), which hereafter will be referred to as contaminants of emerging concern (CECs). Pharmaceuticals and their pharmaceutically active metabolites/transformation products are a class of CECs that are widely used in human and veterinary medicine and are essential to modern healthcare (Fent et al., 2006, Nikolaou et al., 2007). Nevertheless, there are growing concerns about the negative impacts that may result from continuous contamination of the environment with pharmaceutically-active compounds (Barbosa et al., 2016, Verlicchi and Zambello, 2016). This research is important because of the potential toxic effects for aquatic biota and human health that may result from chronic exposure to such CECs (Fent et al., 2006, Kümmerer, 2009, Nikolaou et al., 2007). Characteristics specific to this class of environmental contaminants can however present significant challenges for research. For example, CECs exhibit wide variation in function, chemical structure and physiochemical properties, making it difficult to generalize about their behaviour, persistence or impact in the environment. CECs are also designed to be biologically active, have a specific mode of action and to be persistent in the body, meaning they can impact humans and wildlife at trace concentrations which are often hard to detect and quantify using traditional analytical methods (Fent et al., 2006).
Although there are no legal discharge limits for micropollutants into the environment, some regulations have been published in the last few years (Barbosa et al., 2016). CECs in the aquatic environment primarily originate from use in human medicines, however certain classes are also heavily used in veterinary practices (e.g. anti-inflammatory drugs, antibiotics) (Fent et al., 2006, Zhou et al., 2009). A large number of CECs have been detected in WWTPs influents and effluents and surface, ground and drinking water worldwide in recent years (Barreiros et al., 2016, Heberer, 2002, Nikolaou et al., 2007, Ternes, 1998, Zhou et al., 2009, Verlicchi and Zambello, 2016). In fact, it is now established that throughout the developed world, CECs are ubiquitous at μg to ng per litre levels in the aquatic environment (Nikolaou et al., 2007), although the concentrations of specific compounds depend on usage patterns in different countries and can vary temporally (Verlicchi et al., 2012). The impacts of chronic exposure to trace concentrations of many CECs on wildlife and human health may be severe (e.g. Verlicchi et al., 2012), thus it is critical to limit as much as possible the concentrations of this class of contaminants in our waterways. Certain CECs can specifically impact the endocrine system of humans or wildlife; such chemicals are part of emerging pollutants known as endocrine disrupting chemicals (EDCs). Much of the growing interest in this field of research stems from fears that chronic exposure to EDCs (in bathing or drinking water, for example) may be linked to adverse human health conditions such as declining male fertility, birth defects, and breast and testicular cancer (Nikolaou et al., 2007). Furthermore negative impacts of EDCs exposure on wildlife may include severe consequences such as feminisation in fish (Sumpter and Johnson, 2008). Similar to CECs as a whole, EDCs are mainly thought to be transported into the aquatic environment via incomplete removal at WWTPs (Nikolaou et al., 2007).
Until recently, environmental regulations worldwide had not required explicit testing for any CECs in water bodies. However given the growing concern about contamination of the aquatic environment with these compounds, legislation has recently begun to acknowledge this potential problem. The Water Framework Directive (WFD, 2000/60/EC) is an overarching piece of European environmental legislation aimed at protecting and improving water quality throughout the EU. The WFD committed EU Member States to achieve good qualitative and quantitative status of all water bodies by 2015. In order to reach this goal, certain chemicals identified by Annex X of the WFD have been deemed priority substances; these chemicals (e.g. some pesticides, metals such as lead or mercury, organic volatile compounds and other organics such as polycyclic aromatic hydrocarbon) must be monitored by all member states and cannot exceed specific concentration thresholds in surface waters (defined by the legislation as Environmental Quality Standards, or EQSs). Furthermore, article 16(4) of this legislation requires that the list of priority substances must be reviewed and adjusted as appropriate at regular intervals. As such, directive 2013/39/EU of 12 August 2013 added a further 12 substances to Annex X of the WFD. In addition, Article 8b of Directive 2013/39/EU states that “the Commission shall establish a watch list of substances for which EU-wide monitoring data are to be gathered for the purpose of supporting future prioritisation exercises.” In response to growing EU concern about the release of untreated CECs into the aquatic environment, three compounds were included in the first watch list in 2013: diclofenac (CAS# 15307-79-6, hereafter referred as DCL), 17-beta-estradiol (CAS# 50-28-2, hereafter referred as E2) and 17-alpha-ethinylestradiol (CAS# 57-63-6, hereafter referred as EE2). It is relevant to note that the European Commission implemented decision 495 of 20 March 2015 that expanded substances or groups of substances on the watch list to 10 in the field of water policy. Besides the two pharmaceuticals (DCL and EE2) and the natural hormone (E2) that were previously recommended to be included by the Directive 39/2013/EU, the first watch list of 10 substances/groups of substances also refers to the three macrolide antibiotics (clarithromycin, azithromycin and erythromycin) other natural hormone (E1), some pesticides (oxadiazon, methiocarb, imidacloprid, thiacloprid, thiamethoxam, clothianidin, acetamiprid and triallate), a UVB filter (2-ethinylhexyl 4-methoxcinnamate) and an antioxidant (2,6-di-tert-butyl-4-methylphenol) commonly used as a food additive. This review focuses solely on the first three substances DCL, E2 and EE2 as there is a requirement to investigate policy implications for Ireland of these PhACs in receiving waters in the first instance. An overview of the EU policy in the water field as it relates to commonly used conventional and advanced treatment processes in the aqueous matrices of these 10 substances/groups can be found in Barbosa et al. (2016). The EU-wide monitoring data that will be produced in the next few years will help legislators determine whether or not these compounds are ultimately added to the list of priority substances from Annex X of the WFD. The WFD requires that all EU member states prepare river basin management plans (RBMPs) to address the many issues relating to water quality and protection in a holistic manner. These RBMPs identify the main pressures and activities affecting water status and propose environmental objectives that must be achieved during certain time periods. The recent European legislation on DCL, E2 and EE2 mentioned above has been identified as potentially significant water management issue that may need to be addressed in the next round of RBMPs (due for publication in 2017).
The overall aim of this literature review was to identify and evaluate all previous relevant EU-wide studies on contamination of the aquatic environment with the three watch list pharmaceuticals DCL, E2 and EE2 in order to anticipate their entrance in the WFD priority substances list and to identify gaps in knowledge aiming at guiding future research. This review is directed towards at-risk industries, companies, researchers, regulators and any sectors that would be affected by the addition of these compounds to future iterations of the WFD priority substance list (toxicology, water treatment, chemical analysis, biology, regulation). Risk assessment was not included in this literature review as it has been addressed by other authors (Camacho-Muñoz et al., 2012, Ferrari et al., 2004, Futran Fuhrman et al., 2015). However, this systematic literature review addresses four main research questions for each compound:
- 1)
What are the likely sources/entry points of these CECs into European aquatic environment?
- 2)
What are the likely receptors and loadings in European waters?
- 3)
What monitoring methods are currently employed to measure aquatic concentrations of these CECs, and what are the current limits of detection/quantification?
- 4)
What control measures (including both source control and treatment options) are effective (or potentially effective) and employed for lowering concentrations of these compounds in the aquatic environment?
Section snippets
Systematic review protocol and defining search parameters
Even a cursory search of the literature reveals a vast amount of published material regarding the sources, receptors, monitoring and control measures of DCL, E2 and EE2 (Fatta-Kassinos et al., 2011b, Johnson et al., 2013, Qian et al., 2015). Consequently this literature review was carried out using a defined systematic approach that answers research questions based on the published evidence, which is gathered using a predefined protocol that was adapted from the Centre for Evidence-Based
Results and discussion
The aim of this systematic literature review was to evaluate current state of knowledge on contamination of the European aquatic environment with DCL, E2 and EE2, especially in regards to sources, receptors, monitoring and control measures. The following sections address the specific research questions this systematic review was concerned with: 3.1 General overview of the database, 3.2 Bibliographic analysis: State of European research on DCL, E2 and EE2 report the results from the
Conclusions and future research needs
The overall aim of this study was to provide a baseline study for Europe exploring the implications of the addition of the three watch list compounds DCL, E2 and EE2 to the Water Framework Directive (WFD) priority substances list. This study utilized a systematic literature review to summarize the European state of knowledge in regards to the sources and prevalence of these CECs. Finally, a critical analysis of the effectiveness of potential control measures was carried out based on
Acknowledgements
The authors express gratitude to Ireland's Environmental Protection Agency STRIVE Programme for supporting this study (Project 2014-W-DS-18).
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