**1. Introduction**

Industrialization and the development of technology make our lives easier, but they also bring negative effects on our health. Particularly, the reproductive health is the system most affected by these modern living conditions and environmental factors. In recent years, many environmental polluting chemicals have been shown to have the ability to interfere with the functioning of the body's hormone, which have been classified as endocrine-disrupting chemicals (EDCs). An EDC is defined by the United States Environmental Protection Agency (EPA) as, "an exogenous chemical substance or mixture that alters the structure or function(s) of the endocrine system and causes adverse effects at the level of the organism, its progeny, and populations or (sub)populations" [1–4].

These EDCs are extremely heterogeneous and can be divided into three groups;

1.Pharmaceuticals—(e.g., diethylstilbestrol, ethinyl oestradiol, naproxen, acetaminophen),


EDCs have been by far the biggest focus due to their widespread use and wide exposure. The major route of human exposure to these chemicals is through ingestion of contaminated water and food (e.g., meat, fish, dairy products, and vegetables), *via* inhalation, and through the skin. These chemicals are easily released into the environment for example through leaching into the soil and water. Some EDCs (such as some organochlorine pesticides, polychlorinated biphenyl, biphenol-A, phthalates, heavy metals) are known as persistent organic pollutants due to their high lipophilicity. These substances pass into the systemic circulation, can be metabolized to compounds that are more toxic than the parent chemicals, and are potentially eliminated through pathways such as urine, semen, and breast milk [6–9].

EDCs include different groups of chemicals such as persistent organic pollutants, industrial compounds, children's products (containing lead, phthalates, cadmium), food contact materials (e.g., bisphenol A, phthalates, linings of cans, or plastic bottles containing phenol), pesticides, chemical substances that are widely used in cosmetics such as phthalates, ultraviolet (UV) filter constituents, and parabens, as well as several heavy metals, polybrominated diphenyl ethers that are flame retardants used in agriculture, and many household and industrial products [2, 8].

Most EDCs have the potential to markedly affect the development of the steroid hormone dependent human reproductive system. EDCs can interfere with the normal secretion, synthesis, production, metabolism, transport, or effect of hormones. EDCs can alter cellular processes by different mechanisms, by binding to steroid hormone nuclear receptors and activating genomic and non-genomic pathways, activating ion channels, inducing proinflammatory cytokines and chemokines, promoting oxidative stress, and altering cell proliferation and differentiation [7, 8]. EDCs may contain a large number of molecules capable of inducing estrogenic or antiandrogenic effects. They may mimic the sex hormones estrogen or androgen or they may block the activities of estrogen or androgen. (i.e., be antiestrogens or antiandrogens) [4, 5, 10]. EDCs can indirectly produce an estrogenic response by a number of different mechanisms, such as increasing estrogen synthesis (e.g., peroxisome proliferators inducing aromatase activity, thus increasing circulating estradiol levels), facilitating estrogen receptor binding, or altering the estrogen ratio. Estrogens are a group of chemicals of similar structure primarily responsible for female reproduction but the existence of estrogen in men has been known for over 90 years. However, our knowledge of the general role of estrogens in the male reproductive and non-reproductive organs is clearly far behind that in females. In addition, exposure to exogenous estrogens, especially developmentally, has recently been shown to have deleterious effects on the male reproductive system in men [11, 12].

Estrogens are mainly produced by the ovaries, but also by the adrenal glands and adipose tissue. Estradiol is most potent member of the class of steroid hormones produced primarily by the ovaries [11, 13]. For instance, in either sex, androgens give rise to estrogens, through aromatase, so together they play a vital role in homoeostasis. In addition, EDCs can exert an antiestrogenic effect by preventing endogenous estrogens from interacting with their receptors and thus inhibiting their action. In general,

#### *Endocrine Disruptors and Infertility DOI: http://dx.doi.org/10.5772/intechopen.104403*

estrogenic compounds promote the development of female sexual characteristics; antiestrogens inhibit the development of female characteristics, but not necessarily male characteristics [7, 13].

It is well known that chemicals interfering with hormonal pathways can seriously affect human reproductive disorders such as infertility, endometriosis, breast cancer, testicular cancer, poor sperm quality, and/or function [5, 6, 9, 14]. A growing body of scientific evidence indicates that reproductive health, and ultimately reproductive capacity, is under pressure globally. Unfortunately, relatively few studies have addressed the impact of environmental exposures on human reproductive function. It has been reported that the number of families applying to infertility clinics to have a child with the assisted reproductive techniques has increased significantly in recent years [4, 8, 15]. Infertility is defined as "a disease characterized by the failure to establish a clinical pregnancy after 12 months of regular and unprotected sexual intercourse." It affects 10–15% of all couples and varies between countries and geographic regions. Idiopathic infertility accounts for approximately 44% of male infertility cases and is the most common individual diagnosis [3, 16, 17].

The current chapter discusses the detrimental effects of EDCs exposure on male/ female infertility, by providing an overview of experimental studies on humans and by reporting epidemiological studies in humans. The present section will focus on the relationship between hormone disruptors and female infertility. Specifically, pesticides pyrethroids, heavy metal such as lead as well as commonly used cosmetics like UV filters will be discussed.
