Introduction

Water scarcity is a global issue that affects all continents and constitutes one of the major challenges of the 21st century. Over the past few years, water use and consumption have grown at twice the rate of population growth. Although there is enough drinking water on the planet, its distribution is irregular, contaminated in many cases, and is often unsustainably managed [1].

The supply problem is exacerbated by the significant pollution of surface water and groundwater due to discharges of waste from human activity. The United Nations estimates that 2 million tons of waste are disposed of through waterways every day [2]. Such pollution reduces the availability of safe drinking water and requires an extensive treatment process.

Although substantial pollution prevention measures implemented in the last century have drastically reduced the presence of some pollutants, such as the so-called "persistent organic compounds", the list of known potentially dangerous substances that can affect the environment, and thus humans, is extensive [3, 4]. Currente research attention are focused on the class of "emerging contaminants" (ECs). ECs are natural or synthetic chemical substances of various origins, and their presence in natural ecosystems is not necessarily new. However, the development of more sensitive analytical methods in recent years has made it possible to detect their presence, increasing concern about their potential consequences for human health [5].

ECs are found in many types of everyday chemicals, such as pesticides used to protect crops from insects, weeds, fungi and other pests [6]. This subgroup of emerging contaminants is of particular concern to agencies such as the World Health Organization (WHO) and the European Food Safety Authority (EFSA) [7–9]. Most of these substances are very persistent in the environment and can be highly toxic to humans. There is scientific evidence that chronic exposure to pesticides can lead to various health issues such as cancer, neurologic disorders, diabetes, respiratory disorders, and reproductive syndromes [10]. Moderate pesticide poisoning can cause intrinsic asthma, bronchitis, and gastroenteritis. Acute effects may include reduced vision, headaches, salivation, diarrhea, nausea, vomiting, wheezing, coma and even death [11]. These effects depend on the chemical nature of the compound, the amount, and the mode of exposure (ingestion, inhalation or direct skin contact) [12].

On the other hand, pesticides are very important for food production, as they maintain and/or increase crop yields, which is especially important in countries with food shortages. The need to produce enough food to feed the world’s population, combined with political and economic interests, has left an impact on agricultural practices worldwide. In many countries, particularly those with more flexible regulations, these pressures have led to expanded use of fertilizers and pesticides to achieve and maintain higher yields [13–15].

The European Union (EU) has established a framework for the prevention and control of water pollution, that includes measures to assess the chemical status of water and strategies to reduce the presence of pollutants. As stated in Directive 2013/39/EU of 12 August 2013 amending Directives 2000/60/EC and 2008/105/EC in relation to priority substances in the field of water policy [16], priority must be given to identifying the causes of pollution and addressing pollutant emissions at their source, in the most economically and environmentally effective way. Some strategies were agreed in the Millennium Development Goals through the Sustainable Development Goals (SDGs), especially Goal 6 "Ensure availability and sustainable management of water and sanitation for all" [17].

The EU recently revised the regulation on surface water and groundwater pollution, urban wastewater, and the sustainable use of pesticides [18–20]. This evidence that the study of these substances is research priority for the protection of public health and the environment [4].

Despite all these regulatory frameworks established by competent authorities, the presence of pesticide residues in aquatic ecosystems remains high. This underscores the need to understand the prevalence and extent of this type of contaminant, in order to formulate preventive strategies to minimize their presence in the environment, particularly in aquatic systems, specially water designated for human consumption [11, 21–23]. Thus, this paper describes a protocol for a systematic review and meta-analysis to assess the prevalence and concentration of pesticides in European waters.

Methods and analysis

Discussion

Studies carried out in recent years reveal the presence not only of the well-known ECs but also of numerous variants of these families, in this case the study of pesticides. Pesticides can be found in the water bodies, derived above all, by the runoff from the agricultural field where they have been applied and industrial wastewaters. Especially pesticides more soluble are transported by water molecules during the precipitation event by percolating downward into the soil layers and eventually reaching surface waters and groundwater [31]. Consequently, it produces a degradation of water quality and then reduces the supply of potable water. The presence of pesticides in different environmental compartments, such as groundwater and surface water are a widespread problem. For example, pesticides with high mobility and persistence like organophosphates are detected most frequently in streams and groundwater around the world [32].

Although the use of pesticides is necessary to achieve higher agricultural yields, the occurrence of pesticides in water poses a deleterious effect on human and ecosystem health, where the effect magnitude depends on the pesticide properties such as solubility, half-life, adsorption capacity or biodegradability [33]. The effects produced in human beings can be acute or chronic. Some concrete examples of the effects of the pesticides above human health are reported in literature [10]. Frequent exposure to chlorinated pesticides had a high chance of inducing prostate cancer and allergic or non-allergic asthma in farmers [34].

To protect public and ecosystem health, guideline levels for pesticides in drinking waters have been restricted by governments. For example, there are several guideline values for the presence of pesticides in drinking water issued by WHO, United States, Australia, EU and Japan [35]. In fact, new legislations have been implemented in Europe for the use of regenerated water containing pesticides.

Concerns have increased, as has the need to detect them and use new techniques to reduce and eliminate them. For this reason, this study was undertaken because, to the authors knowledge, there are many site-specific monitoring studies, but no studies that conduct a systematic review and meta-analysis of pesticides in Europe.

The study focuses on the systematic review of the status of European Mediterranean waters through a meta-analysis of data collected in studies conducted in recent years using the most relevant databases in this research area. To establish comparative studies between the different regions of the Mediterranean and the repercussion of these pollutants by families. To offer not only a global vision of the current situation of pharmaceuticals, drugs and personal hygiene products, but also new possibilities to increase the detection and elimination systems of these ECs.

Therefore, it is necessary to resort to what are known as monitoring studies that, through the design and implementation of methods, processes and procedures, guarantee, to a large extent, the follow-up and evaluation of these pesticides, as well as the implementation or execution of observation systems for the ecosystems [36]. In this respect, chemical pollution of natural waters represents a threat to the environment, with effects such as acute or chronic toxicity in aquatic organisms, accumulation of pollutants in the ecosystem and loss of habitats and biodiversity [37, 38]. As stated in Directive 2013/39/EU, the causes of pollution must be identified, and pollutant emissions must be dealt with at source in the most economically and environmentally effective way [16]. There are no studies in the literature dealing specifically with this issue and the results of this study will help in the elaboration of public policies for the whole of Europe. The results obtained through this study will contribute to the development of public policies for Europe and probably for the whole world.

Supporting information