Various factors may affect growth and maturation which may change individual’s genetic map. These factors can be classified into genetic, nutritional, hormonal, and environmental [5].
Pollution is very old problem that became huge one with the start of the industrial revolution. Different pollutants can reach our bodies mainly via inhalation and intake with food, while dermal contact presents a minor route of exposure [3].
The composition of pollutants, dosage and time of exposurecan affect human health. These effects can be in the form of nausea, difficult respiration, skin irritation, and malignancy. They also include fetal abnormalities, developmental restriction in children, and many other problems[6].
Several environmental pollutants are suspected to have many effects on the growth of fetuses and children [4].
As a result of children physiological immaturity, they are really vulnerable to pollutants. Transplacental transfer during pregnancy and Breast feeding are also important sources of exposure to pollutants [7].
At the early on weeks of development, the fetus is more sensitive to teratogenic insults. Environmental teratogens can produce cellular death, alter normal maturation of tissues, or interfere with normal cellular differentiation. This may causefetal loss, growth restriction, and birth abnormalities, or impaired neurologic performance [8].
Dosage and timing are important determinants of fetal results. Thus, exposures occurring at “critical periods” in development have specific effects related to the developmental level of the fetal internal organs and contact with the same chemical at different times may cause different effects . Exposure to these chemicals at the last weeks of pregnancy may generate only minor abnormalities, but can still impair growth and development [8].
Central nervous system (CNS) of the fetus is most vulnerable system to developmental injury throughout pregnancy. The fetal brain is particularly sensitive to harmful toxinsdue to incomplete blood-brain barrier; continued myelination, diffrentiation of neurons; and sensitivity to hypoxia.
Environmental chemicals associated with normal growth disruption can be classified into two main groups, Endocrine disruptors and Heavy metals.[9].
An endocrine-disrupting compound was defined by theU. S. Environmental Protection Agency (EPA) as “an exogenous agent that disrupts activity, secretion, transport, metabolism, action, or elimination of natural blood-borne hormones that are present in the body and control homeostasis, reproduction, and developing process.
Endocrine-disrupting chemicals (EDCs) are acting through many receptors, as thyroid gland receptors (TRs), estrogen pain (ERs), progesterone receptors, androgen receptors (ARs), and retinoid receptors.. Many enzymatic path ways involved in steroid biosynthesis and/or metabolism, and a lot of other mechanisms that affect endocrine and reproductive systems[10].
Endocrine disruptors are pollutants include synthetic chemicals used as solvents/lubricants and their byproducts [polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), dioxins], plastics [bisphenol A (BPA)], plasticizers (phthalates), pesticides [methoxychlor, chlorpyrifos, dichlorodiphenyltrichloroethane (DDT)], fungicides (vinclozolin), and pharmaceutical agents [diethylstilbestrol (DES)] [11].
Bisphenol A (BPA)
BPA is a monomer used to harden polycarbonate plastics, plus some epoxy resins. These plastics are widely-used in water bottles, infant bottles, and some medical devices. The BPA containing epoxy resins are widely-used to cover metal products, such as food cans, and are generally used in some dental sealants and tools. The primary route of exposure is ingestion through the diet, since BPA can migrate into food from food and drink containers [12].
A study from the United states Department of Health and Human Services’ National Toxicology Program (NTP) endorsed the conclusions of an expert panel of the Center for the Evaluation of Risks to Human Reproduction (CERHR). This panel concluded that there is “some concern” for neural and behavioral effects in fetuses, newborns, and children at current human BPA exposures [13].