1. Introduction

The occurrence of endocrine disrupting compounds (EDCs) in wastewaters, aquatic systems, and drinking water is considered one of the main environmental problems globally. Endocrine disrupting compounds (EDCs) have gained significant interest in recent decades in the academic press because of the many, serious diseases related to them. Exposure to EDCs is interlinked with decreased fertility, changed sexual behaviour, and amplification of abnormalities and cancers in humans and laboratory animals [1–3]. Kavlock et al. [4] defines EDC as “an exogenous agent that interferes with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body which are responsible for the maintenance of homeostasis, reproduction, development and or behaviour”. Several hundreds of chemicals may have endocrine disrupting properties [5,6]. More than 100 substances are categorised as potential endocrine disrupters such as: Carbon disulfide, o-phenylphenol, tetrabrominated diphenyl ether, 4-chloro-3-methylphenol, 2,4-dichlorophenol, resorcinol, 4-nitrotoluene, 2,2′-bis(4-(2,3-epoxypropoxy) phenyl) propane, 4-octylphenol, estrone (E1), 17α-ethinylestradiol (EE2), and 17β-estradiol (βE2 [7]. The main EDCs include the following pharmaceuticals: Triclosan, nonylphenol, nonylphenol ethoxylates, octylphenol, octylphenol ethoxylates, bisphenol A, phytoestrogens, and steroid hormones have been identified in wastewater [8], and these compounds also frequently occur in domestic wastewater, industrial wastewaters, and livestock wastes [9–12]. These and other associated EDCs such as: Bisphenol A (BPA), Polychlorinated biphenyls (PCBs), and phthalates, have been identified in human serum, fat, and umbilical cord blood [13–16]. The four important categories of EDCs are: Natural steroidal oestrogens, synthetic oestrogens, phytoestrogens, and various industrial chemicals (xenoestrogens) contaminants have a strong estrogenic strength.

Natural and synthetic oestrogens have greater oestrogenic effects than phyto- and xenoestrogens [17–20]. Nevertheless, the concentrations of phyto- and xenoestrogens in aquatic environments are usually higher. Recent research indicates that several sewage treatment plant effluents and rivers in the UK comprise sufficient quantities of oestrogenic compounds to induce harmful effects on aquatic species [21–26]. The occurrence of EDC pollutants in wastewater creates a huge concern to humans and animals and therefore, the current paper provides an overview of the adverse effects of EDC contaminants and removal methods which were used in the UK for the period of 2010–2017. The research highlights that despite the relative efficacy of existing chemical and physical methods for removing certain EDCs from wastewater, there is emerging evidence supporting the need for more widespread application of nature-based and biological approaches, particularly the use of biofilms. 

2. Endocrine Disrupting Compounds and Their Impacts

Endocrine disrupting compounds are a type of exogenous endocrine disruptors and encompass natural hormones and synthetic compounds secreted by humans and animals. The majority of EDCs have not been studied completely, analytical approaches for many of the recognised EDCs have yet to be established, and the stages of toxicological consequences or impacts are yet to be conducted. Since 1940, there has been a rapid increase in the number and usage of chemicals for various purposes, and some of those chemicals have been discharged into the environment [15]. This chemical upsurge has changed the environment ecosystems and caused damage to human health and wildlife (Table 1). The first publication on EDCs came out in 1962, which emphasised that Dichlorodiphenyltrichloroethane (DDT) could be accountable for the reduction of bird populations owing to reproductive failure triggered by DDT and other associated harmful chemicals. It is predicted that more than 24% of human disorders and diseases are caused by environmental factors across the globe [27]. While the percentage of urogenital malformations in male babies were raised amongst those exposed to DDT in the developing countries [28,29]. The constant exposure to the DDT in the infanthood and adolescence stages has been identified in the results of substantial reproductive irregularities, cancers, early adolescence, and low pregnancy rates in females [30,31]. Endocrine related disease rates have risen due to the sharp increase in use and application of manufactured chemicals. Since 1970, production of plastics has risen from 50 million to 300 million tonnes today, and the chemical industry has experienced a huge growth in global sales, which has increased from £126 billion in 1970 to over £2.9 trillion in 2013 [32].

Table 1. EDC (endocrine disrupting compound) paths of exposure in humans. Source: Adapted from Gore et al. [15].

Snyder (2003) [18] found that oestrogenic compounds in drinking water are not responsible (highly likely) for adverse human health effects because of the relatively small amounts of oestrogenic content in water compared to the quantity in foods. However, exposure to EDCs for humans is distinct from aquatic organisms such as fish, therefore, an equivalent hormonal response might not be anticipated [33,34]. Some of the EDC have a long life span, and these will be harmful to humans and wildlife. The substances of these EDC do not decay over a certain period, and there is a chance they fragment into more complex toxic elements than the initial particles. Moreover, some of the EDC substances which were banned several decades ago still remain in significant amounts in the environment, and these particles are not easily detectable in aquatic animals and other organisms [35,36]. EDCs also cause abnormalities in fish reproductive systems and stimulation of vitellogenin synthesis in fish plasma, and can also significantly reduce (nearly 90%) the production of fertile eggs of sand goby fish [37]. In summary, various natural and synthetic chemical compounds have been identified that induce estrogenic responses, and several studies specify that EDCs are ubiquitous in diverse media, and their probable risks to humans and lab animals are very high. Therefore, EDCs are of concern worldwide because of their wide range of negative impacts on the environment. EDCs have complex molecular structures and distinctive biological systematic mechanisms and as a result, cannot be effectively removed by sewage treatment plants (STPs) [38], but may effectively be processed in wastewater treatment plants.