# Plaaben Compounds--Part I: An Overview of Their Characteristics, Detection, and Impacts
## 3 Paraben Potential Impacts
### Human Health Impact  
Paraben compounds can show estrogenic [31] and antiandrogenic activity [32]. As previously mentioned, these molecules have been associated with tumors, namely breast tumors [28], as well as male infertility [33]. Thus, parabens are being identified as a potential risk to human health [33]. The main sources of human exposure to parabens are the use of pharmaceutical products and cosmetics [34]. Parabens and other xenobiotic chemicals interfere with the hypothalamo-pituitary-gonadal axis and behave similar to female hormones, blocking or destabilizing the normal hormonal action, negatively affecting the reproductive function of males [33]. Endocrine disruptors can interfere with endogenous hormone action, synthesis, metabolism, and transport. These compounds can also change in the normal functioning of the central nervous system, immune system, lipid homeostasis, glucose levels, thyroid function and act as epigenetic modulators causing transgenerational effects [34]. Propylparaben is noniritating and nonsensitizing for normal skin populations, but sensitizing effects were detected in the application of medicines that contained parabens for damaged or broken skin [22]. The Ophthalmic Drug Panel of the United States Food and Drugs Administration's Bureau of Drugs considered MP and PP unsuitable for use in ophthalmic solutions preparations because they can cause eye irritation [21]. It was observed by [PERSON] and [PERSON] [35] that an ingestion of 2000 mg of PP daily for 1 month did not cause a visible toxic effect, but another experiment by [PERSON] et al. [36] using 2000 mg of MP for an unknown period reported the same innocuousness [22]. There is not enough data that can relate the use of parabens with allergic reactions, although some people reported allergies after the ingestion of products containing parabens [22]. [PERSON] et al. [37] reviewed several studies about human skin irritation for products with parabens at 0.1-0.8%. In general, no irritation was noticed, although some cases of moderate irritation were reported. The authors summarized the results of tests with parabens in 27,230 patients with dermatitis, and for patch testing of 1-30% parabens, only 2.2% developed sensitization. Subjects with intact skin did not had sensitization reactions to parabens [19]. [PERSON] et al. [38] applied MP, EP, PP and BuP at different concentrations (5%, 7%, 10%, 12% and 15%) in propylene glycol to 50 patients for 5 days. PP up to 12% did not cause irritation, but a concentration of 15% showed some signs of irritation. For the \"no effect concentration\", the test was repeated in 50 humans (25 males and 25 females) with patches being applied for 4-8 h every day for 3 weeks, and no sensitization was reported [19]. In some countries, 15% of human couples are affected by infertility, and most of the cases are related to low sperm mobility or sperm counts [33]. In vitro studies conducted by [PERSON] et al. (1989) [39], proved that methylparaben, ethylparaben, propylparaben and butylparaben are effective spermicides for human spermataozoan, for a spermicidal potency of 6, 8, 3 and 1 mg/mL [19; 21; 23]. A study carried out by [PERSON] et al. [40] analyzed urine, blood, and semen samples of 215 university students (18-23 years) from the Murcia region, Spain. The researchers did not find correlations between urinary parabens and reproductive hormone levels or semen parameters in young men. Nevertheless, the authors admit that more studies need to be carried out to verify and confirm this hypothesis. [PERSON] et al. [41] studied the effects of MP, EP, PP and BuP on estrogenic activity, and all the parabens showed a weak estrogenic activity compared to 17-beta-estradiol. The estrogenic activity increased as the alkyl length increases. Additionally, parabens showed estrogenic activity, since it was noticed that parabens can interact with the estrogen receptor [19]. Further, [PERSON] et al.