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1. Introduction
Organochlorine pesticides (OCPs) are a class of persistent organic pollutants (POPs) that accumulate in the environment and can be distributed through runoffs into surface water or groundwater [1]. OCPs with low estrogenic or anti-estrogenic effects are classified as endocrine disruptors. Lipophilic OCPs, known for having high resistance to degradation as well as long half-lives, can be bioaccumulative in the environment and are usually detected in biological media such as human serum, breast milk, and adipose tissues through everyday diets [2,3]. OCPs have been banned since the 1960s by the Stockholm Convention, but in most developing countries, they are still being utilized illegally [4]. In Taiwan, the government has banned the use of OCPs since 1975. However, the OCPs released before the ban of OCPs use are still present in various environmental and biological media [5,6,7].
OCPs negatively affect human health and have been reported to cause endocrine disruption, reproductive toxicities, neurological disorders, immunotoxicity, and oncogenesis [4]. Meeker, et al. [8] found that serum levels of p-p′-dichlorodiphenyldichloroethylene (DDE) cause endocrine disruption by increasing the free thyroxine (T4) and total triiodothyronine (T3) levels and found DDE to be inversely associated with thyroid-stimulating hormone (TSH). Reproductive toxicity studies linking OCPs to female infertility and gynecological issues date back to as early as the 1980s [9]. In an in-vivo study, rats exposed to methoxyclor (200 mg kg−1 b.w.) for 7 days showed a reduction in seminal vesicle weight, serum testosterone, and dehydroepiandrosterone levels [10] while mature female rabbits exposed to dichlorodiphenyltrichloroethane (DDT) (3 mg kg−1) and lindane (0.8 mg kg−1) exhibited reduced ovulation rates [11]. Although several in-vitro studies (e.g., studies using ovarian cells) have listed the negative impacts of DDE and DDT, such as infertility and reductions in the number, development or quality of oocytes, fertilization rate, embryo quality or development, and pregnancy rate, only a few of these studies have managed to obtain statistically significant results [12]. An epidemiological study reported that high levels of serum ΣDDT (DDE + DDT) above 1 μg kg−1 were significantly correlated to low pregnancy rates in German women [13]. On the other hand, Axmon, et al. [14] indicated that female serum levels of DDE were not correlated to the prolonged time to...