**4. Health effects of POPs**

polychlorinated dibenzo-*p*-dioxins and dibenzofurans (PCDDs/PCDFs) and polycyclic aromatic hydrocarbons (PAHs). The first priority list of POPs consisted of 12 compounds commonly referred as the dirty dozen by the Stockholm Convention that was adopted in 2001.

Over the last decade, the priority list of POPs has been updated to include such compounds like brominated flame retardants (BFRs), such as polybrominated diphenyl ethers (PBDEs), listed under the Stockholm Convention in 2017 [1], and hexabromocyclododecanes (HBCDDs), currently under consideration for listing. A further group of recently recognized halogenated POPs are the perfluorinated alkyl substances, of which perfluorooctane sulfonate (PFOS), its salts, and perfluorooctane sulfonyl fluoride were also added to the Stockholm list in 2017. Other compounds in the new list include endosulfan, lindane, pentachlorobenzene, chlorde-

POPs have a tendency to persist in the environment for long periods, are capable of longrange transport, bioaccumulate in human and animal tissue and biomagnify in food chains and food webs, and have potential significant adverse impacts on human health and the environment. Exposure to POPs can cause serious health problems including certain cancers, birth defects, dysfunctional immune and reproductive systems, greater susceptibility to disease, and even diminished intelligence. Of all known POPs so far, the organochlorine compounds, including polychlorinated dibenzo-*p*-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs), have received the most attention due to their persistence in the environment, bioaccumulation, biomagnification, and hazard

There are many ways that release POPs to the environment. POPs such as pesticides are released, as a result of plant protection efforts. The main sources of pesticide pollution include

cone, and hexabromocyclododecane (HBCD).

**2. Sources of POPs in the environment**

**Figure 1.** Emission of dioxins from industrial wastes. Source: Marie Sedillo et al. 2010.

effects to biota.

18 Persistent Organic Pollutants

POP exposure may cause developmental defects, chronic illnesses, and death. Some are carcinogens, possibly including breast cancer. Many POPs are capable of endocrine disruption within the reproductive system, the central nervous system, or the immune system. People and animals are exposed to POPs mostly through their diet, occupationally, or while growing in the womb [6]. For humans not exposed to POPs through accidental or occupational means, over 90% of exposure comes from animal food products due to bioaccumulation in fat tissues and bioaccumulation through the food chain. In general, POP serum levels increase with age and tend to be higher in females than males [7].

#### **4.1. Effect on endocrine disruption**

Exogenous substance/mixture that alters the function(s) of the hormonal system and consequently causes adverse effects in an intact organism or its progeny or its subpopulation is called endocrine disruptors. The majority of POPs are known to disrupt the normal functioning of the endocrine system. Low-level exposure to POPs during critical developmental periods of the fetus, newborn, and child can have a lasting effect throughout its lifespan. A 2002 study [8] synthesizes data on endocrine disruption and health complications from exposure to POPs during critical developmental stages in an organism's lifespan. The study aimed to answer the question whether or not chronic, low-level exposure to POPs can have a health impact on the endocrine system and development of organisms from different species. The study found that exposure of POPs during a critical developmental time frame can produce a permanent change in the organism's path of development. Exposure of POPs during non-critical developmental time frames may not lead to detectable diseases and health complications later in their life. In wildlife, the critical development time frames are in utero, in ovo, and during reproductive periods. In humans, the critical development time frame is during fetal development [9].

#### **4.2. Effect on the reproductive system**

The same study in 2002 with evidence of a link from POPs to endocrine disruption also linked low-dose exposure of POPs to reproductive health effects. The study stated that POP exposure can lead to negative health effects especially in the male reproductive system, such as decreased sperm quality and quantity, altered sex ratio, and early puberty onset. For females exposed to POPs, altered reproductive tissues and pregnancy outcomes as well as endometriosis have been reported [9, 10].

**Figure 2.** Transboundary movement of POPs. (Source: Ref. [13]).

**Figure 3.** Transport and circulation of PCDDs/PCDFs and PCBs in the environment. (Source: Ref. [14]).

Degradation Pathways of Persistent Organic Pollutants (POPs) in the Environment

http://dx.doi.org/10.5772/intechopen.79645

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#### **4.3. Effect on gestational weight gain and newborn head circumference**

A Greek study in 2014 investigated the link between maternal weight gain during pregnancy exposure and PCB level in their newborn infants, their birth weight, gestational age, and head circumference. The lower the birth weight and head circumference of the infants was, the higher POPs levels during prenatal development had been, but only if mothers had either excessive or inadequate weight gain during pregnancy. No correlation between POP exposure and gestational age was found [11]. A 2013 case-control study conducted in 2009 in Indian mothers and their offspring showed prenatal exposure of three types of organochlorine pesticides (HCH, DDT and DDE) impaired the growth of the fetus, reduced the birth weight, head circumference and chest circumference [12].
