# Plaaben Compounds--Part I: An Overview of Their Characteristics, Detection, and Impacts
## 3 Paraben Potential Impacts
### Impacts in Animals  
As already mentioned, it has been shown that parabens can act as endocrine disruptors [29; 30] and that ED compounds can have negative impacts on animals' reproductive systems due to their properties, causing animal feminization, abnormal formations and a decreased in the fecundity of species [75; 76]. Compared to 17\(\beta\)-estradiol, MP, EP, PP and BuP require much higher concentrations to obtain the same response as 17\(\beta\)-estradiol for yeast estrogen screen tests (in vitro study), but it was also reported that BuP could compete with 17\(\beta\)-estradiol in rats in terms of binding the estrogen receptor [34]. However, several authors have reported in in vitrostudies that parabens show weak estrogenic effects [34] but other studies suggest that PP, BuP and BeP can cause adverse effects in aquatic organisms and elicit low estrogenic activity [77]. Additionally, other studies mention that the exposure of fish to low concentrations of paraben compounds can cause vittilogenin (VTG) synthesis, so with this, can cause estrogenic effects [77]. Similar conclusions were reported in studies reviewed by [PERSON] et al. [34]. The effects of endocrine disruptors, namely xenoestrogens, were already noticed in alligators and fishes [78; 79]. [PERSON] et al. [79] did not find evidence of bioaccumulation of parabens in fishes, but studies carried and referred in Section 5.3 show that parabens were detected in fishes. [PERSON] et al. [22] reviewed studies regarding the use of propylparaben for short-term and long-term toxicity, carcinogenicity, and reproduction studies. The major studies involving PP did not show significant problems or statistically significant results for well-structured and well-defined conclusions in animals, including for carcinogenic and reproduction tests. However, some studies for products containing MP, EP, PP and BuP at 0.1-0.8% were carried out by [PERSON] et al. [37], and some products caused slightly or minimal eye irritation in rabbits [22]. Additionally, the application of PP at 10% caused irritation when applied to rabbit skin [22]. Studies showed that rabbits fed with PP at 500 mg/kg/day for 6 days did not show an any negative effects, and the first toxic effect was noticed at 3000 mg/kg/day. Regarding dogs, effects did not appear for MP or PP at 500 mg/kg/day, but toxicity appeared at 4000 mg/kg/day [22]. Some studies in rats concluded that feeding the animals PP of between 1% and 4% caused an increase in labeling index in the prefundic area of the forestomach epithelium, and these studies opened doors for questions of the possibility of occurrence of similar problems in humans, although humans do not have a prefundic forestomachs. However, other similar studies in rats did not produce the same results [22]. [PERSON] et al. [21] reviewed studies using methylparaben for oral, dermal, and intrathecal short-term effects, and concluded that no data or conclusions could prove toxicity effects in rats for oral or intrathecal exposition. However, a group of rabbits where dermal toxicity was studied showed moderate and well-defined erythema, slight edema, and slight desquamation, using products containing 0.2% of MP applied for 3 months daily at doses of 5.5 mg/cm\({}^{2}\)/8.4% body surface area [21; 37]. For another study using the same percentage of MP and dose of 6.6 and 11 mg/cm\({}^{2}\)/8.4%, the same occurred, and in another study of 0.2% of MP and PP in rabbits for doses of 2 and 6 mg/cm\({}^{2}\)/10% of area, the product caused moderate erythema, slight edema, and mild desquamation, and, occasionally, some epidermal fissures with bleeding and papuloerythema [21]. For long-term and carcinogenicity studies with methylparaben, no evidence of toxicity, abnormalities or to be carcinogenic was found in rats or dogs [21]. Additionally, contrary to what happened for PP, for MP no differences were observed in the labeling index in the prefundic area of forestomach epithelium of rats [21].