**Endocrine Disrupting Compounds – Problems and Challenges**

Błażej Kudłak, Natalia Szczepańska, Katarzyna Owczarek, Zofia Mazerska and Jacek Namieśnik

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/60410

#### **Abstract**

In this chapter, information about some of the estrogenic compounds and their environmental fate and biological influence can be found. Special attention is paid to the review of the analytical approaches used at the stages of detection and determi‐ nation of Endocrine Disrupting Compounds (EDCs) in the environmental samples. Also, a brief characterization of both cellular and non-cellular bioassays is presented.

The discovery of micropollutants occurring in the environment resulted in new methodologies being put into the analytical practice. These methodologies are developed in two different directions. The first is based on methodological solutions designed to detect, identify, and determine xenobiotics that occur in various environ‐ mental samples. For this purpose, instrumental methods such as gas and liquid chromatography with mass spectrometry detection are usually used. The second approach is to put into the analytical practice the new bioanalytical methodologies. These methodologies allow the estimation of the sample endocrine potential, but they do not provide the information about which of the sample ingredient is responsible for causing the toxic effect. These results can be the basis for estimating the endocrine potential of the environment exhibited by certain species. Moreover, bioanalytical techniques may be supplementary to the techniques of quantitative and qualitative determination of EDCs.

**Keywords:** Endocrine Disrupting Compounds, xenohormones, trace organic pollu‐ tants, EDC milestones, biotests

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **1. Introduction**

The development of new technologies, progressive urbanization, increasing consumerism, and industrial boom in developing countries has led to elevated pollution of the environment. The broad spectrum of pollutants produced and released to the environment has increased in the last few decades, including the agricultural, industrial, pharmaceutical, and plastic industries. These chemicals can be found in the individual elements of the environment, both living (biota) and non-living. Chemists very often pay attention only to chemical compounds, which are treated as substances foreign to the average chemical composition of individual elements of the environment or occur at levels higher than the so-called mean composition. However, attention should also be paid to legal aspects connected with the presence of specific pollutants in the individual elements of the environment, which are often defined as xenobi‐ otics. Environmental research includes a broader spectrum of chemical individuals – xenobi‐ otics – that need to be detected, identified, and determined. They can be divided into [1]:


The examples of the EDC groups, whose presence in the environment are both regulated and non-regulated by legal aspects, are presented in the Figure 1.

**Figure 1.** Groups of EDC pollutants subjected/not-subjected to legal regulations.

#### **1.1. The basics of hormonal regulation**

To understand endocrine disruption, the basic features and mechanisms of the endocrine system must be explained. The endocrine system consists of a number of ductless glands that secrete hormones directly into the circulatory system (to the blood) in order to regulate various functions of the body. In turn, a hormone is called a special signaling molecule that is produced by an endocrine gland. Hormone molecules travel through the blood to target distant cells and tissues to regulate physiological functions and behavior [6].

Figure 1. Groups of EDC pollutants subjected/not-subjected to legal regulations.

The endocrine system is made up by the following glands:


**1. Introduction**

170 Emerging Pollutants in the Environment - Current and Further Implications

The development of new technologies, progressive urbanization, increasing consumerism, and industrial boom in developing countries has led to elevated pollution of the environment. The broad spectrum of pollutants produced and released to the environment has increased in the last few decades, including the agricultural, industrial, pharmaceutical, and plastic industries. These chemicals can be found in the individual elements of the environment, both living (biota) and non-living. Chemists very often pay attention only to chemical compounds, which are treated as substances foreign to the average chemical composition of individual elements of the environment or occur at levels higher than the so-called mean composition. However, attention should also be paid to legal aspects connected with the presence of specific pollutants in the individual elements of the environment, which are often defined as xenobi‐ otics. Environmental research includes a broader spectrum of chemical individuals – xenobi‐ otics – that need to be detected, identified, and determined. They can be divided into [1]:

**•** compounds that are already subjected to legal regulations because their physicochemical properties, as well as immediate and distant toxic effects (as a result of ecotoxicological tests), and appropriate methodologies are already available and it is possible to obtain reliable information about changes in the content of these analytes in various types of environmental samples. Thus, it was possible to propose appropriate standards defining the highest concentration of a given xenobiotic in a defined environmental element. These normative values are called the *Maximum Admissible Concentration (MAC)* in European

**•** compounds that are not subjected to legal regulations yet. This group includes xenobiotics detected in the environment because new analytical methodologies were introduced into the analytical practice, which make it possible to detect and determine analytes occurring in tested environmental samples at very low levels (so-called micropollutants). It is said that the determined compounds have been so far called **unidentified pollutants**. The group of pollutants, which are not subjected to legal regulations, includes the so-called newly emerging pollutants [4]. These compounds are introduced into the individual elements of the environment as a result of new manifestations of human pressure, e.g. a new technology of manufacturing products or consumer goods. As a result, it has not been possible yet to define the ecotoxicological properties or develop and validate appropriate analytical procedures, which could make it possible to obtain reliable information about the levels of these compounds in various environmental samples. The occurrence of some specific micropollutants (EDCs), which are not subjected to legal regulation yet, has become more and

The examples of the EDC groups, whose presence in the environment are both regulated and

countries and the *Threshold Limit Value (TLV*) in the United States [2, 3];

more concerning in the last years [5].

non-regulated by legal aspects, are presented in the Figure 1.

Next to these specialized endocrine glands, many other organs and tissues have secondary endocrine functions and secrete hormones (e.g. heart, adipose tissue, muscle, liver, kidneys) [7, 8]. Just to make a story short, every system of internal secretion glands, hormones, and final organs sensitive to given stressors can be named the hormonal system. With such systems, the organism can reach and hold the homeostasis.

Hormones produce effects by acting on specialized proteins called receptors that attract and bind to specific hormones. Hormone receptors provide specificity to hormone actions, both in terms of the time and the place of hormone action. A receptor proteins superfamily consists of glucocorticoid, mineralocorticoid, androgen, estrogen, progesterone, retinoic acid, vitamin D, and thyroid receptors. Binding with ligand (antagonist or agonist) *in vivo* causes conforma‐ tional changes, dimerization, and binding to a specific DNA sequence responding to charac‐ teristic receptor (see Figure 2) [1].

The target of the hormonal system is the activity of estrogenic, androgenic, thyroid, and glucocorticoids hormones. Classification of the hormones based on their structural properties is presented in Table 1. The modes of action of specific signaling systems are summarized in Figure 2 [1].

#### **1.2. Endocrine disrupting compounds as xenohormones**

EDCs are chemicals responsible for the occurrence of disturbances in the hormonal balance of the organism. This group includes both egzogenic and endogenic substances or their mixtures that impact the function of the natural hormones in the organism [13]. Taking into account complexity and importance of hormones played in organisms functioning, it must be stated that endocrine chemicals have versatile and almost unlimited cells at low concentration levels. EDCs, also called xenohormones, disturb natural hormonal balance by modifying the func‐ tioning of the hormonal system in numerous ways [13-15]. Below are specified selected processes through which EDCs may influence human beings [8, 13, 16]:


**•** natural endocrine chemicals;

Next to these specialized endocrine glands, many other organs and tissues have secondary endocrine functions and secrete hormones (e.g. heart, adipose tissue, muscle, liver, kidneys) [7, 8]. Just to make a story short, every system of internal secretion glands, hormones, and final organs sensitive to given stressors can be named the hormonal system. With such systems, the

Hormones produce effects by acting on specialized proteins called receptors that attract and bind to specific hormones. Hormone receptors provide specificity to hormone actions, both in terms of the time and the place of hormone action. A receptor proteins superfamily consists of glucocorticoid, mineralocorticoid, androgen, estrogen, progesterone, retinoic acid, vitamin D, and thyroid receptors. Binding with ligand (antagonist or agonist) *in vivo* causes conforma‐ tional changes, dimerization, and binding to a specific DNA sequence responding to charac‐

The target of the hormonal system is the activity of estrogenic, androgenic, thyroid, and glucocorticoids hormones. Classification of the hormones based on their structural properties is presented in Table 1. The modes of action of specific signaling systems are summarized in

EDCs are chemicals responsible for the occurrence of disturbances in the hormonal balance of the organism. This group includes both egzogenic and endogenic substances or their mixtures that impact the function of the natural hormones in the organism [13]. Taking into account complexity and importance of hormones played in organisms functioning, it must be stated that endocrine chemicals have versatile and almost unlimited cells at low concentration levels. EDCs, also called xenohormones, disturb natural hormonal balance by modifying the func‐ tioning of the hormonal system in numerous ways [13-15]. Below are specified selected

**•** EDCs have also imprinted in the specific mechanisms of modifying organisms functioning,

organism can reach and hold the homeostasis.

172 Emerging Pollutants in the Environment - Current and Further Implications

**1.2. Endocrine disrupting compounds as xenohormones**

**•** modifying hormones synthesis pathways;

**•** cell/tissue transport of hormones in the organism;

**•** mimicking the endogenous hormones' functioning;

**•** changes of level or activity of the hormonal receptors.

**•** EDCs can be assigned to one of two groups [17]:

**•** hormones excretion mechanisms;

**•** hormones degradation pathways.

**•** binding to receptors;

just to mention [15]:

processes through which EDCs may influence human beings [8, 13, 16]:

**•** antagonism with synthesis of natural hormones or their metabolism;

teristic receptor (see Figure 2) [1].

Figure 2 [1].

**•** chemicals emitted to the environment as a result of anthropopression.

**Figure 2.** Mode of hormonal action in target receptor.


**Table 1.** Division of the hormones based on their structural properties [1, 9-12].

#### *1.2.1. A brief history of EDCs discovery*

The first evidences of endocrine disruption in nature have been observed since the 1950s, but the source of the occuring phenomena was not known yet. Figure 3 shows the most important milestones in the development of the knowledge about endocrine disrupting micropollutants.

Currently, the studies on EDCs are spreading in all branches of science including analytical chemistry, toxicology, chemometrics (data treatment), modeling, chemical processing, *etc*. [30]. Their aim is to predict the environmental fate of these chemicals, EDCs' potential to cause observable deformations, identify newly emerging pollutants, and assess the efficiency of novel sozotechnical methods being designed to reduce threats posed by EDCs. The next step – and the most difficult one – for sure will be validating and establishing legal frames to control the pollution level with EDC.

**Figure 3.** Selected milestones on Endocrine Disrupting Chemicals analysis and environmental issues.

Since the 1960s, the huge increase of the number of such scientific papers has been observed. The rate of this increase is presented in Figure 4.

**Figure 4.** Increasing number of manuscripts on EDC over the years.

#### *1.2.2. Scientific centers and laboratories dealing with the issue of EDC*

There is still not enough knowledge about mechanisms, modes of action and the effects that endocrine disrupting compounds and their mixtures, which are present in the environment, have on single organisms and on whole ecosystems. That is the reason why researches in this field of expertise are being held in numerous scientific centers and laboratories all over the world. In Table 2, the above mentioned scientific units are presented. The studies conducted are aimed at:


## **2. Health effects**

#### **2.1. Harmful health effects of EDCs on vertebrates**

#### *2.1.1. Humans*

novel sozotechnical methods being designed to reduce threats posed by EDCs. The next step – and the most difficult one – for sure will be validating and establishing legal frames to control

**Figure 3.** Selected milestones on Endocrine Disrupting Chemicals analysis and environmental issues.

The rate of this increase is presented in Figure 4.

Since the 1960s, the huge increase of the number of such scientific papers has been observed.

the pollution level with EDC.

174 Emerging Pollutants in the Environment - Current and Further Implications

Until now, there is no clear opinion in the scientific circles concerning the harmful effects of EDCs. However, it is hard to remain calm as the review of literature concerning the issues connected to environmental chemistry and ecotoxicology shows an increasing number of


**Table 2.** Information on selected scientific units conducting research on EDCs.

articles showing a relation between the presence of xenobiotics in the environment and the annually increasing rate of incidence of various kinds of neoplasms, distorted reproductive behavior, and an increasing level of feminization of specific populations at different levels of the food chain.

Even though the majority of those studies has been conducted on animals, there is evidence confirming the negative effect of even small doses of those substances have on humans [31]. The EDC group compounds are characterized by a similar structural construction to natural estrogens. Although the activity of many xenoestrogens has been estimated to be lower than the activity of the feminine sex hormone estradiol, numerous *in vitro* studies indicate its capability of binding with ERα, Estrogen Receptors, and aryl hydrocarbon and thyroid hormones receptors. These properties are the reason why estrogen is suspected to cause diseases resulting from hormonal disorders, including: fertility problems, heart diseases, circulatory problems, and diabetes [32]. The data published during the last few years more and more often indicates to a relation between identification and the growing levels of EDCs in various biological samples and the global problem of obesity, which occurs on an epidemic scale.

In addition, as the latest reports from the scientific world indicate, many of these compounds may have an influence on organisms not only through receptors. The epigenetic tests con‐ ducted have confirmed that these compounds influence the process of methylation of histone proteins, influencing alterations in the molecule expression. There are many concerns regard‐ ing the fact that these contaminations are capable of crossing the placenta barrier and the bloodbrain barrier, and thus, they may have a negative influence on organisms since the early stages of their lives. This fact has been confirmed in many epidemiological studies and experiments, what indicates to a strong correlation between an exposure of the mother to the activity of xenobiotics and the occurrence of neurodevelopmental disorders of her offspring, such as ADHD, autism, or alterations in behavioural development as well as impairment of cognitive functions [33]. There are many indications that show that the compound may be also respon‐ sible for the initiation of carcinogenesis, that is why studies conducted in numerous research centers are aimed at finding the relations between the presence of xenoestrogens in the human body and the frequency of incidence of neoplasms of e.g., the testicles, prostate, uterus, ovaries, and breasts [34].

Humans may be exposed to the harmful effects of the EDCs *via* many ways as presented in Figure 5. [7].

**Figure 5.** Routes of human exposure to EDCs.

#### *2.1.2. Wildlife*

articles showing a relation between the presence of xenobiotics in the environment and the annually increasing rate of incidence of various kinds of neoplasms, distorted reproductive behavior, and an increasing level of feminization of specific populations at different levels of

**Scientific center**

University of Saskatchewan, Department of Veterinary Biomedical Sciences and Toxicology Centre, Saskatoon, Canada

University of Arizona, Department of Chemical and Environmental Engineering, Tuscon United States

Institute of Molecular Science, Division of Molecular Environmental Endocrinology, Japan

Catalan Institute of Water Research (ICRA) Girona, Spain

University of Exert, Bioscences Exeter, United Kingdom

Carleton University, Department of Chemistry, Ottawa, Canada

Universiteit Antwerpen, Toxicological Center, Antwerpen, Belgium

**Table 2.** Information on selected scientific units conducting research on EDCs.

Gdańsk University of Technology, Department of Analytical Chemistry

176 Emerging Pollutants in the Environment - Current and Further Implications

Even though the majority of those studies has been conducted on animals, there is evidence confirming the negative effect of even small doses of those substances have on humans [31]. The EDC group compounds are characterized by a similar structural construction to natural estrogens. Although the activity of many xenoestrogens has been estimated to be lower than the activity of the feminine sex hormone estradiol, numerous *in vitro* studies indicate its capability of binding with ERα, Estrogen Receptors, and aryl hydrocarbon and thyroid hormones receptors. These properties are the reason why estrogen is suspected to cause diseases resulting from hormonal disorders, including: fertility problems, heart diseases, circulatory problems, and diabetes [32]. The data published during the last few years more and more often indicates to a relation between identification and the growing levels of EDCs in various biological samples and the global problem of obesity, which occurs on an epidemic

In addition, as the latest reports from the scientific world indicate, many of these compounds may have an influence on organisms not only through receptors. The epigenetic tests con‐ ducted have confirmed that these compounds influence the process of methylation of histone proteins, influencing alterations in the molecule expression. There are many concerns regard‐ ing the fact that these contaminations are capable of crossing the placenta barrier and the bloodbrain barrier, and thus, they may have a negative influence on organisms since the early stages of their lives. This fact has been confirmed in many epidemiological studies and experiments, what indicates to a strong correlation between an exposure of the mother to the activity of

the food chain.

scale.

Most data about the adverse effects of endocrine disruptors present in the environment on wild aimals come from Europe and North America. Observed changes vary from very subtle, such as small changes in the physiology and sexual behavior of some species to permanently altered sexual diferentiation. Most affected are aquatic species located on the top of the food chain, but some effects have also been observed in terrestial species. Table 3 provides infor‐ mation concerning some health effects induced by EDCs on wildlife [5].

Figure 5. Routes of human exposure to EDCs.


**Table 3.** Summarized information about the adverese health effects of EDCs on wildlife [7].

#### **2.2. Harmful health effects of EDCs on invertebrates**

There is still not enough knowledge on endocrine effects on invertebrates; however, these organisms seem to be good intermediates in modeling hormonal potential toward higher organisms. There are some historical reports in which females have exhibited signs of mascu‐ linization, apparently in association with exposure to EDCs. Exposure of marine gastropods to Tributyltin (TBT), a biocide used in anti-fouling paints, provides the clearest example in invertebrates of an endocrine-mediated adverse effect caused by exposure to an environmental contaminant. Masculinization of marine gastropods exposed to TBT has resulted in worldwide declines of gastropods. The endocrine mechanism probably involves elevated androgen levels possibly through altered aromatase activity. Tributyltin-induced imposex in prosobranch female snails is a condition in which the penis "imposes" on the normal female reproductive anatomy. The associated development of the sperm duct can, in extreme cases, lead to the blockage of the oviduct of the female, resulting in sterility and population declines [1, 5, 7].
