Pharmacokinetic profile of propyl paraben in humans after oral administration

Repeated-dose toxicity and toxicokinetic study of isobutylparaben in rats subcutaneously treated for 13 weeks

Parabens have historically served as antimicrobial preservatives in a range of consumables such as food, beverages, medications, and personal care products due to their broad-spectrum antibacterial and antifungal properties. Traditionally, these compounds were believed to exhibit low toxicity, causing minimal irritation, and possessing limited sensitization potential. However, recent evidence suggests that parabens might function as endocrine-disrupting chemicals (EDCs). Consequently, extensive research is underway to elucidate potential human health implications arising from exposure to these substances. Among these parabens, particular concerns have been raised regarding the potential adverse effects of iso-butylparaben (IBP). Studies have specifically highlighted its potential for inducing hormonal disruption, significant ocular damage, and allergic skin reactions. This study aimed to evaluate the prolonged systemic toxicity, semen quality, and estrus cycle in relation to endocrine disruption endpoints, alongside assessing the toxicokinetic behavior of IBP in Sprague-Dawley rats following a 13-week repeated subcutaneous administration. The rats were administered either the vehicle (4% Tween 80) or IBP at dosage levels of 2, 10, and 50 mg/kg/day for 13 weeks. Blood collection for toxicokinetic study was conducted on three specified days: day 1 (1st), day 30 (2nd), and day 91 (3rd). Systemic toxicity assessment and potential endocrine effects were based on various parameters including mortality rates, clinical signs, body weights, food and water consumption, ophthalmological findings, urinalysis, hematological and clinical biochemistry tests, organ weights, necropsy and histopathological findings, estrus cycle regularity, semen quality, and toxicokinetic behavior. The findings revealed that IBP induced local irritation at the injection site in males at doses ≥ 10 mg/kg/day and in females at 50 mg/kg/day; however, systemic toxicity was not observed. Consequently, the no-observed-adverse-effect level (NOAEL) for IBP was determined to be 50 mg/kg/day in rats of both sexes, indicating no impact on the endocrine system. The toxicokinetics of IBP exhibited dose-dependent systemic exposure, reaching a maximum dose of 50 mg/kg/day, and repeated administration over 13 weeks showed no signs of accumulation.

Parabens effects on female reproductive health - Review of evidence from epidemiological and rodent-based studies

Parabens have been used as antimicrobial preservatives since the 1920s. The prevalent use of parabens increases their detection in the environment and in women's biological samples including reproductive tissues. Recent studies suggest parabens may alter endocrine function and thus female reproductive health may be affected. In this literature review, we summarize findings on parabens and female reproduction while focusing on epidemiological and rodent-based studies. The topics reviewed include paraben effects on cyclicity, pregnancy, newborn and pubertal development, reproductive hormones, and ovarian and uterine specific outcomes. Overall, the scientific literature on paraben effects on female reproduction is limited and with some conflicting results. Yet, some epidemiological and/or rodent-based experimental studies report significant findings in relation to paraben effects on cyclicity, fertility, gestation length, birth weight, postnatal development and pubertal onset, hormone levels, and hormone signaling in reproductive tissues. Future epidemiological and experimental studies are needed to better understand paraben effects on female reproduction while focusing on human related exposures including mixtures, physiologic concentrations of parabens, and multi-generational studies.

Occurrence profiling, risk assessment, and correlations of antimicrobials in surface water and groundwater systems in Southwest Nigeria

The presence of antimicrobials in water has grown into a major global health concern. This study thus focused on the presence, ecological implications, and potential health risks associated with nine antimicrobials: five antibiotics (ampicillin, chloramphenicol, ciprofloxacin, metronidazole, and tetracycline) and four parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in surface water and groundwater samples collected from three Southwestern States in Nigeria (Osun, Oyo, and Lagos States). These antimicrobials were widely detected across the three States with ciprofloxacin being the most dominant having maximum average concentrations of 189 μg L-1 and 319 μg L-1 in surface water and groundwater respectively. The range of average concentrations of antibiotics in surface water are 47.3-235 μg L-1 (Osun), 27.9-166 μg L-1 (Oyo) and 52.1-159 μg L-1 (Lagos). For groundwater, it is 35.3-180 μg L-1 (Osun), 26.5-181 μg L-1 (Oyo) and 32.3-319 μg L-1 (Lagos). The average concentrations of all parabens were 32.4-153 μg L-1, 53.4-80.1 μg L-1, and 83.2-132 μg L-1 for surface water and 46.7-55.7 μg L-1, 53-117 μg L-1, and 62.4-118 μg L-1 for groundwater in Osun, Oyo, and Lagos States respectively. Methylparaben was most frequently detected paraben with average concentrations of 153 μg L-1 and 117 μg L-1 in surface water and groundwater respectively. The measured environmental concentrations of these antimicrobials pose a significant ecological risk while those of ciprofloxacin and ampicillin pose a high health risk to all population groups studied. The average concentrations of antibiotics investigated in this study exceeded their threshold values for Predicted No-Effect Concentrations (PNEC) associated with resistance selection, except for tetracycline.

Into the toxicity potential of an array of parabens by biomimetic liquid chromatography, cell viability assessments and in silico predictions

Five parabens (PBs) i.e., Methylparaben (MP), Ethylparaben (EP), Isopropylparaben (iPrP), Isobutylparaben (iBuP), Benzylparaben (BzP), and their parent compound i.e., para-hydroxy Benzoic Acid (pHBA), were studied both in vitro and in silico. Specifically, we determined their retention on several both protein- (Human Serum Albumin and α1-acidic glycoprotein) and (phospho) lipid- (immobilized artificial membrane (IAM)) based biomimetic stationary phases to evaluate their penetration potential through the biomembranes and their possible distribution in the body. The IAM phases were based either on phosphatidylcholine (PC) analogues i.e., PC.MG and PC.DD2 or on sphingomyelin (SPH). We also assessed their viability effect on breast cancer cells (MCF-7) via MTT assay subjecting the cells to five different PB concentrations i.e., 100 μM, 10 μM, 1 μM, 0.1 μM and 0.01 μM. Finally, their pharmacokinetics and toxicity were assessed by the ADMET Predictor™ software. Isopropylparaben was found to be more active than 17β estradiol (E2) employed as positive control, on the screened cell line inducing cell proliferation up to 150 % more of untreated cells. Other analogues showed only a slight/moderate cell proliferation activity, with parabens having longer/branched side chain showing, on average, a higher proliferation rate. Significant linear direct relationships (for PC.DD2 r2 = 0.89, q2 = 0.86, for SPH r2 = 0.89, q2 = 0.85, for both P value < 0.05) were observed between the difference in proliferative effect between the readout and the control at 0.01 μM concentration and the retention on the IAM phases measured at pH 5.0 for all compounds but pHBA, which is the only analyte of the dataset supporting a carboxylic acid moiety. IAM affinity data measured at pH 7.0 were found to be related to the effective human jejunal permeability as predicted by the software ADMET® Predictor, which is relevant when PBs are added to pharmaceutical and food commodities.

Benzoic acid supplementation improves the growth performance, nutrient digestibility and nitrogen metabolism of weaned lambs

Nitrogen is one of the essential components of proteins and nucleic acids and plays a crucial role in the growth and development of ruminants. However, the nitrogen utilization rate of ruminants is lower than that of monogastric animals, which not only reduces protein conversion and utilization, but also increases manure nitrogen discharge as well as causing environmental pollution. The lamb stage is an important period in the life of sheep, which can affect the production performance and meat quality of fattening sheep. The purpose of this experiment was to explore effects of benzoic acid supplementation on growth performance, nutrient digestibility, nitrogen metabolism and plasma parameters of weaned lambs. A total of 40 weaned male Hu sheep lambs with similar body weight were randomly divided into 4 groups: control with no benzoic acid (0 BA) and the lambs in other 3 groups were fed 0.5, 1, and 1.5% benzoic acid on the basis of experimental diet (0.5, 1, and 1.5 BA, respectively). The experiment lasted for 60 days. Results showed that the average daily gain of 1 BA group was significantly increased (p < 0.05) when compared to 0 and 1.5 BA groups, while an opposite tendency of dry matter intake to average daily gain ratio was observed. The dry matter, organic matter, neutral detergent fiber and acid detergent fiber digestibility of 1 BA group was significantly increased (p < 0.05) as compared with 0 and 1.5 BA groups as well as plasma albumin content. Also, the urinary hippuric acid and hippurate nitrogen concentrations in 1 and 1.5 BA groups were higher (p < 0.05) than those in 0 and 0.5 BA groups. Additionally, the nitrogen intake in 0.5 and 1 BA groups was significantly increased (p < 0.05) when compared to other groups. At 1 h after morning feeding, the plasma benzoic acid concentration of 1 BA group reached up to maximum value and was higher (p < 0.05) than other groups, and then began to decrease. Similarly, the hippuric acid concentration in plasma of 1 and 1.5 BA groups was higher (p < 0.05) than that of 0 BA group from 1 to 4 h post morning feeding. At 3 h after feeding, the urea nitrogen concentration in plasma of 0 BA group was higher (p < 0.05) than that of 1.5 BA group. Overall, the appropriate supplementation of benzoic acid (1%) in the diet can improve growth performance and nitrogen metabolism of weaned lambs.

Environment, Endocrine Disruptors, and Fatty Liver Disease Associated with Metabolic Dysfunction (MASLD)

Ecological theories suggest that environmental factors significantly influence obesity risk and related syndemic morbidities, including metabolically abnormal obesity associated with nonalcoholic fatty liver disease (MASLD). These factors encompass anthropogenic influences and endocrine-disrupting chemicals (EDCs), synergistically interacting to induce metabolic discrepancies, notably in early life, and disrupt metabolic processes in adulthood. This review focuses on endocrine disruptors affecting a child's MASLD risk, independent of their role as obesogens and thus regardless of their impact on adipogenesis. The liver plays a pivotal role in metabolic and detoxification processes, where various lipophilic endocrine-disrupting molecules accumulate in fatty liver parenchyma, exacerbating inflammation and functioning as new anthropogenics that perpetuate chronic low-grade inflammation, especially insulin resistance, crucial in the pathogenesis of MASLD.

Associations of urinary non-persistent endocrine disrupting chemical biomarkers with early-to-mid pregnancy plasma sex-steroid and thyroid hormones

BACKGROUND/OBJECTIVES

Pregnant women are exposed to numerous endocrine disrupting chemicals (EDCs) that can affect hormonal pathways regulating pregnancy outcomes and fetal development. Thus, we evaluated overall and fetal sex-specific associations of phthalate/replacement, paraben, and phenol biomarkers with sex-steroid and thyroid hormones.

METHODS

Illinois women (n = 302) provided plasma for progesterone, estradiol, testosterone, free T4 (FT4), total T4 (TT4), and thyroid stimulating hormone (TSH) at median 17 weeks gestation. Women also provided up-to-five first-morning urine samples monthly across pregnancy (8-40 weeks), which we pooled to measure 19 phthalate/replacement metabolites (reflecting ten parent compounds), three parabens, and six phenols. We used linear regression to evaluate overall and fetal sex-specific associations of biomarkers with hormones, as well as weighted quantile sum and Bayesian kernel machine regression (BKMR) to assess cumulative associations, non-linearities, and chemical interactions.

RESULTS

In women of relatively high socioeconomic status, several EDC biomarkers were associated with select hormones, without cumulative or non-linear associations with progesterone, FT4, or TT4. The biomarker mixture was negatively associated with estradiol (only at higher biomarker concentrations using BKMR), testosterone, and TSH, where each 10% mixture increase was associated with -5.65% (95% CI: -9.79, -1.28) lower testosterone and -0.09 μIU/mL (95% CI: -0.20, 0.00) lower TSH. Associations with progesterone, testosterone, and FT4 did not differ by fetal sex. However, in women carrying females, we identified an inverted u-shaped relationship of the mixture with estradiol. Additionally, in women carrying females, each 10% increase in the mixture was associated with 1.50% (95% CI: -0.15, 3.18) higher TT4, whereas in women carrying males, the mixture was associated with -1.77% (95% CI: -4.08, 0.58) lower TT4 and -0.18 μIU/mL (95% CI: -0.33, -0.03) lower TSH. We also identified select chemical interactions.

CONCLUSION

Some biomarkers were associated with early-to-mid pregnancy hormones. There were some sex-specific and non-linear associations. Future studies could consider how these findings relate to pregnancy/birth outcomes.

Urinary Paraben Concentrations and Associations with the Periconceptional Urinary Metabolome: Untargeted and Targeted Metabolomics Analyses of Participants from the Early Pregnancy Study

BACKGROUND

Parabens, found in everyday items from personal care products to foods, are chemicals with endocrine-disrupting activity, which has been shown to influence reproductive function.

OBJECTIVES

This study investigated whether urinary concentrations of methylparaben, propylparaben, or butylparaben were associated with the urinary metabolome during the periconceptional period, a critical window for female reproductive function. Changes to the periconceptional urinary metabolome could provide insights into the mechanisms by which parabens could impact fertility.

METHODS

Urinary paraben concentrations were measured in paired pre- and postconception urine samples from 42 participants in the Early Pregnancy Study, a prospective cohort of 221 women attempting to conceive. We performed untargeted and targeted metabolomics analyses using ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry. We used principal component analysis, orthogonal partial least-squares discriminant analysis, and permutation testing, coupled with univariate statistical analyses, to find metabolites associated with paraben concentration at the two time points. Potential confounders were identified with a directed acyclic graph and used to adjust results with multivariable linear regression. Metabolites were identified using fragmentation data.

RESULTS

Seven metabolites were associated with paraben concentration (variable importance to projection score > 1 , false discovery rate-corrected q -value < 0.1 ). We identified four diet-related metabolites to the Metabolomics Standards Initiative (MSI) certainty of identification level 2, including metabolites from smoke flavoring, grapes, and olive oil. One metabolite was identified to the class level only (MSI level 3). Two metabolites were unidentified (MSI level 4). After adjustment, three metabolites remained associated with methylparaben and propylparaben, two of which were diet-related. No metabolomic markers of endocrine disruption were associated with paraben concentrations.

DISCUSSION

This study identified novel relationships between urinary paraben concentrations and diet-related metabolites but not with metabolites on endocrine-disrupting pathways, as hypothesized. It demonstrates the feasibility of integrating untargeted metabolomics data with environmental exposure information and epidemiological adjustment for confounders. The findings underscore a potentially important connection between diet and paraben exposure, with applications to nutritional epidemiology and dietary exposure assessment. https://doi.org/10.1289/EHP12125.

Maternal paraben exposure and intra-pair thyroid-stimulating hormone difference in twin neonates

Thyroid hormones are essential for fetal growth and neurodevelopment. The recent frequent use of parabens has raised concerns about their endocrine-disrupting potential. However, the effects of maternal paraben exposure on neonatal thyroid hormone levels are still largely unknown. In our study, a co-twin control design was employed to analyze the relationships between maternal paraben exposure and neonatal thyroid-stimulating hormone (TSH) difference. We collected information from 252 mother-twin pairs from a twin birth cohort in Wuhan, China. Concentrations of six parabens were measured in maternal urine samples collected at < 16, 16-28, and > 28 weeks of gestation. Data of neonatal TSH levels were retrieved from medical records. Multiple informant models were applied to explore the time-specific relationships between paraben exposure and intra-twin TSH difference and to determine the susceptible window of exposure. We found that maternal urinary methyl paraben (MeP) during early pregnancy was positively associated with intra-twin TSH difference (%change = 5.96 %; 95 % confidant interval (CI): 0.04 %, 12.2 %). However, no significant differences were observed for exposure to ethyl paraben (EtP) and propyl paraben (PrP), and the associations between parabens and intra-twin TSH difference did not differ materially across pregnancy. Further, a stratified analysis based on twin zygosity and chorionicity and sex types indicated that the positive association between early pregnancy MeP exposure and intra-twin TSH difference was significant in monochorionic diamniotic (MCDA) twins of female-female fetuses and dichorionic diamniotic (DCDA) twins of opposite-sex. The prospective twin study provides first evidence that MeP exposure in early pregnancy was associated with an increased TSH difference in twin neonates, especially in female fetuses.

Human metabolism and excretion kinetics of benzotriazole UV stabilizer UV-327 after single oral administration

UV-327 (2-(5-chloro-benzotriazol-2-yl)-4,6-di-(tert-butyl)phenol) is used as an ultraviolet (UV) absorber in plastic products and coatings. Due to its ubiquitous distribution in the environment, human exposure is conceivable. In the study presented herein, initial information on the human in vivo metabolism of UV-327 was obtained by single oral administration to three volunteers. Urine and blood samples were collected up to 72 h after exposure. One study participant additionally donated plasma samples. Maximum blood and plasma levels of UV-327 and its two monohydroxylated metabolites UV-327-6-mOH and UV-327-4-mOH were reached 6 h post-exposure. Almost the entire amount found in blood and plasma samples was identified as UV-327, whereas the two metabolites each accounted for only 0.04% of the total amount, indicating that UV-327 is well-absorbed from the intestine, but only partially metabolized. Plasma to blood ratios of UV-327, UV-327-6-mOH, and UV-327-4-mOH ranged from 1.5 to 1.6. Maximum urinary excretion rates of UV-327, UV-327-6-mOH, UV-327-4-mOH, and UV-327-4 + 6-diOH were reached 9-14 h post-exposure. However, only about 0.03% of the orally administered dose of UV-327 was recovered as UV-327 and its metabolites in urine, indicating that biliary excretion may be the major route of elimination of UV-327 and its hydroxylated metabolites. The present study complements the insight in the complex absorption, distribution, metabolism, and elimination (ADME) processes of benzotriazole UV stabilizers (BUVSs).

Endocrine disrupting chemicals: A promoter of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disorder. With the improvement in human living standards, the prevalence of NAFLD has been increasing in recent years. Endocrine-disrupting chemicals (EDCs) are a class of exogenous chemicals that simulate the effects of hormones in the body. There has been growing evidence regarding the potential effects of EDCs on liver health, especially in NAFLD. This paper aims to summarize the major EDCs that contribute to the growing burden of NAFLD and to raise public awareness regarding the hazards posed by EDCs with the objective of reducing the incidence of NAFLD.

Pharmacokinetics of transdermal methyl-, ethyl-, and propylparaben in humans following single dermal administration

Parabens are common chemicals used as preservatives in foods, cosmetics, and personal care products. Although transdermal exposure to parabens occurs, studies on human pharmacokinetics (PK) following dermal exposure to parabens are scarce. In this study, the PK following dermal exposure to parabens was determined and compared with our previous findings on oral exposure. A paraben mixture cream containing 0.8% deuterated methyl-, ethyl-, and propylparaben (MeP-d₄ 0.26%; EtP-d₄ 0.26%, and PrP-d₄ 0.28%) was dermally applied to the whole arm of five male volunteers at a dose of 24 g/person over 30 min. Blood and urine samples were collected at several intervals over the course of 48 h to measure the levels of MeP-d₄, EtP-d₄, and PrP-d₄ and their conjugated metabolites using HPLC-MS/MS. As a result of non-compartmental analysis, the average peak values of total (sum of conjugated and unconjugated metabolites) MeP-d₄, EtP-d_4, and PrP-d₄ were reached at 7.8 h, 10.5 h, and 5.3 h, indicating a slower absorption rate compared to that of oral exposure (<2 h). The terminal elimination half-lives of MeP-d₄, EtP-d₄, and PrP-d₄ were 12.2 h, 12.0 h, and 9.3 h, respectively. Fractional urinary excretion (F_ue) of total MeP-d₄, EtP-d₄, and PrP-d₄ was 1.7%, 2.3%, and 1.9%, respectively. The F_ue of total and unconjugated PrP-d₄ following dermal exposure was five times lower and three times higher, respectively, compared with those after oral exposure, suggesting that PrP is relatively less metabolized to the conjugated form after dermal exposure. Taken together, dermal exposure to paraben leads to a longer apparent half-life and results in higher proportions of biologically active unconjugated parabens in the systemic circulation as compared to oral exposure. This study provides insights into the kinetic properties of parabens and their metabolites in humans.

Reviewing the variability in urinary concentrations of non-persistent organic chemicals: evaluation across classes, sampling strategies and dilution corrections

Various biomonitoring studies have been carried out to investigate the exposure of populations by measuring non-persistent organic chemicals in urine. To accurately assess the exposure, study designs should be carefully developed to maximise reproducibility and achieve good characterization of the temporal variability. To test these parameters, the intraclass correlation coefficients (ICCs) are calculated from repeated measurements and range from poor (<0.4) to excellent (≥0.75). Several studies have reported ICCs based on diverse study designs, but an overview, including recommendations for future studies, was lacking. Therefore, this review aimed to collect studies describing ICCs of non-persistent organic chemicals, discuss variations due to study design and formulate recommendations for future studies. More than 60 studies were selected, considering various chemical classes: bisphenols, pyrethroids, parabens, phthalates, alternative plasticizers and phosphate flame retardants. The variation in ICCs for an individual chemical was high (e.g. ICC of propyl paraben = 0.28-0.91), showing the large impact of the study design and of the specific exposure sources. The highest ICCs were reported for parabens (median = 0.52), while lowest ICCs were for 3-phenoxybenzoic acid (median = 0.08) and bisphenol A (median = 0.20). Overall, chemicals that had an exposure source with high variation, such as the diet, showed lower ICCs than those with more stable exposure sources, such as indoor materials. Urine correction by specific gravity had an overall positive effect on reducing the variability of ICCs. However, this effect was mostly seen in the adult population, while specific compounds showed less variation with creatinine correction. Single samples might not accurately capture the exposure to most non-persistent organic chemicals, especially when small populations are sampled. Future studies that examine compounds with low ICCs should take adequate measures to improve accuracy, such as correcting dilution with specific gravity or collecting multiple samples for one participant.

Phenols, Parabens, Phthalates and Puberty: a Systematic Review of Synthetic Chemicals Commonly Found in Personal Care Products and Girls' Pubertal Development

PURPOSE OF REVIEW

Exposure to endocrine disrupting chemicals through personal care products (PCPs) is widespread and may disrupt hormone-sensitive endpoints, such as timing of puberty. Given the well-documented (and ongoing) decline in age at menarche in many populations, we conducted a systematic review of the epidemiological literature on exposure to chemicals commonly found in PCPs (including certain phthalates, phenols, and parabens) in relation to girls' pubertal development.

RECENT FINDINGS

The preponderance of research on this topic has examined phthalate exposures with the strongest evidence indicating that prenatal monoethyl phthalate (MEP) concentrations may be associated with slightly earlier timing of puberty, including age at menarche. Findings examining peri-pubertal phthalate exposures and pubertal outcomes were less consistent as were studies of prenatal and peri-pubertal phenol exposures. Very few studies had examined parabens in relation to girls' pubertal development. Common study limitations included potential exposure misclassification related to use of spot samples and/or mistimed biomarker assessment with respect to the outcomes. The role of body size as a mediator in these relationships remains unresolved. Overall, evidence of associations between chemical exposures in PCPs and girls' pubertal development was conflicting. When associations were observed, effect sizes were small. Nevertheless, given the many environmental, social, and behavioral factors in the modern environment that may act synergistically to accelerate timing of puberty, even marginal changes may be cause for concern, with implications for cancer risk, mental health, and cardiometabolic disease in later life.

Urinary paraben concentrations of adult women by fasting status: Comparison between Korea and the United States

Personal care products (PCPs) are considered as a major source of paraben exposure; however, the dietary contribution is not well known. We compared the urinary levels of methyl-, ethyl-, and propyl-paraben (MeP, EtP, and PrP), and investigated their associations with fasting status and contacts with other potential exposure sources among Korea and the US adult women. A group of fasting, non-pregnant adult women (n = 469) was recruited from Seoul, Ansan/Incheon, and Jeju, Korea in 2015-2016, and their urine was measured for parabens. Non-fasting Korean women of matching age (25-45 years) were chosen from the Korean National Environmental Health Survey (KoNEHS) Cycle 3 (n = 579). For the US women, both fasting (n = 154) and non-fasting (n = 201) females were chosen from the NHANES 2015-2016 participants. In fasting Korean women, the urinary MeP, EtP, and PrP concentrations (median) were measured at 47.30, 17.90, and 2.30 ng/mL, respectively. Urinary EtP and PrP levels in fasting Korean women were significantly lower than those in non-fasting women (EtP and PrP median of 26.40 and 3.57 ng/mL). On average, the difference in urinary EtP levels by fasting status was greater among the highly exposed groups. In the US population, EtP levels were significantly lower (median ranged 1.55-1.80 ng/mL depending on fasting status), but MeP levels were higher (67.90-84.35 ng/mL) than those of the Korean population. When only fasting women were considered, the median EtP levels of Korean women were 11.5-fold greater than those of US women, suggesting that the non-dietary contributions of EtP exposure could not be ignored among Korean women. Regardless of fasting status, MeP and PrP were significantly correlated, and their urinary levels in fasting Korean women were correlated with the use of several personal care products. The major dietary and non-dietary sources that may explain EtP exposure in Korean women warrant further investigation.

Investigation of estrogen-like effects of parabens on human neutrophils

This study investigated the estrogen-like effects and mechanism of action most commonly used parabens: methyl- (MeP), ethyl- (EtP), propyl- (PrP) and butylparaben (BuP) in human neutrophils. Neutrophils were isolated from 50 blood donors, pre-incubated with antagonists of estrogen receptor α (ERα), ERβ and G-protein coupled estrogen receptor 1 (GPER), then incubated with MeP, EtP, PrP, BuP and 17β-estradiol (E2; 10 nM). Cytotoxic effect was evaluated by MTT test. Neutrophils apoptosis, necrosis and NETs formation were assessed in flow cytometry and confocal microscopy. The ability of the neutrophils for chemotaxis, phagocytosis, NADPH oxidase activity and generation of superoxide anion was assessed in Boyden's chamber, Park's method with latex, the NBT test, and reduction of cytochrome C, respectively. The total nitric oxide concentration was measured in neutrophils supernatants by the Griess reaction. The expression of cathepsin G, neutrophil elastase, proteinase 3, ERα, ERβ and GPER was assessed in Western blot method. In our research, parabens did not cause a cytotoxic effect on human neutrophils nor affect their lifespan. Parabens exposure did not change neutrophils functions (chemotaxis, phagocytosis, NETs formation and oxygen-dependent killing mechanism) and expression of estrogen receptors. Our results suggest that parabens do not cause estrogen receptor-mediated neutrophils-related effects at concentrations measured in the plasma of individuals using products preserved with parabens.

Cytotoxicity evaluation and mechanism of endocrine-disrupting chemicals by the embryoid body test

Endocrine-disrupting chemicals (EDCs) are a structurally diverse class of synthetic and natural compounds. EDCs can cause non-communicable diseases such as obesity, type 2 diabetes, thyroid disorders, neurodevelopmental disease, hormone-dependent cancers, and reproductive disorders. The embryoid body test (EBT) is a developmental toxicity test method that determines the size of embryoid bodies (EBs) and the viability of mouse embryonic stem cells (mESCs) and fibroblasts (3T3 cells). The present study used the EBT to perform cytotoxicity evaluations of 10 EDCs and assessed the mechanistic relationship between endoplasmic reticulum (ER) stress and cytotoxicity. According to the statistical analysis and prediction model results, methylparaben, butylparaben, propylparaben, ethylparaben, triclosan, octylphenol, methoxychlor, bisphenol A, and diethylstilbestrol were classified as cytotoxic, but trichloroacetic acid was non-toxic. Classification accuracy was 90%. The mechanistic study showed that the cytotoxicities of butylparaben, propylparaben, octylphenol, and triclosan were induced by ER stress. The mRNA expressions of BiP, CHOP, and ATF4 were significantly higher following treatments with four EDCs compared to those after the control treatment. Compared to the control treatment, the mRNA levels of XBP1u and XBP1s increased significantly after butylparaben and propylparaben treatments, but did not increase with octylphenol and triclosan treatments. These results indicate that the EBT can be applied as an alternative toxicity test when evaluating the cytotoxicity of EDCs.

Serum parabens and its correlations with immunologic and cellular markers in Southern Taiwan industrialized city systemic lupus erythematosus patients

BACKGROUND

Although the immune systems of patients with systemic lupus erythematosus (SLE) are affected by both personal characteristics and environmental factors, the effects of parabens on patients with SLE have not been well studied. We investigated the indirect effects of four parabens-methylparaben (MP), ethylparaben (EP), propylparaben (n-PrP), and butylparaben (n-BuP)-on several immunological markers.

METHODS

We assessed the serum levels of MP, EP, n-PrP, and n-BuP in 25 SLE patients and correlated the concentration of each paraben with available clinical and laboratory markers, including intracellular markers of antiviral immunity and apoptosis.

RESULTS

The expression of aryl hydrocarbon receptor (AhR) was significantly negatively correlated with n-PrP levels (p = 0.03, r = -0.434). In monocytes, APO2.7 was significantly positively correlated with n-BuP levels (p = 0.019, r = 0.467). Glutathione levels were significantly negatively correlated with n-BuP levels (p = 0.019, r = -0.518). Anti- β2 glycoprotein I IgM was significantly positively correlated with both MP (p = 0.011, r = 0.585) and EP levels (p = 0.032, r = 0.506). Anti-cardiolipin IgA was significantly positively correlated with both MP (p = 0.038, r = 0.493) and n-PrP levels (p = 0.031, r = 0.508). On CD8 T cells, the early apoptotic marker annexin V was significantly negatively correlated with both MP (p < 0.05, r = -0.541) and n-BuP levels (p = 0.02, r = -0.616), and L-selectin was significantly positively correlated with both MP (p < 0.05, r = 0.47) and n-PrP levels (p = 0.02, r = 0.556).

CONCLUSION

Our findings suggest that higher parabens levels were associated with lower AhR expression in leukocytes, increased monocyte apoptosis, lower serum glutathione levels, reduced annexin V expression on CD8 T cells, and higher L-selectin levels on leukocytes.

Investigation of combined effects of propyl paraben and methyl paraben on the hypothalamic-pituitary-adrenal axis in male rats

The aim of this study was to investigate the endocrine-disrupting effects of methyl paraben (MeP) and propyl paraben (PrP) mixture on the hypothalamic-pituitary-adrenal axis (HPA). In this study, six experimental groups were designated. These groups included three control groups (control, corn oil control, and positive control (50 mg/kg/day BPA)) and three dose groups (10, 100, and 500 mg/kg/day MeP+PrP). MeP with PrP were mixed in a 1:1 ratio and administered to the 42-day-old male rats by oral gavage for 30 days. At the end of the experiment, adrenocorticotropic hormone (ACTH), corticosterone and aldosterone hormones were analyzed in serum. Effects of MeP+PrP on the adrenal glands were investigated by immunohistochemical staining of 11ß hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) enzymes involved in the synthesis steps of corticosterone and aldosterone. Also, pituitary and adrenal glands were examined histopathologically. In the histopathological findings, cortical nodule, congestion, and edema were found in the tissues. In the pituitary gland, cytokeratin rings were detected in all MeP+PrP dose groups, supporting the increase of corticosterone and ACTH. Serum corticosterone, aldosterone, and ACTH hormone levels were increased in the 100 mg/kg/day MeP+PrP and BPA groups. Results obtained from immunohistochemical staining showed that increased staining parallelled increased corticosterone and aldosterone hormone levels. In summary, the results showed that exposure to the MeP+PrP mixture caused a significant increase in ACTH and corticosterone. Also, the MeP+PrP mixture caused a significant increase of CYP11B1 and CYP11B2. MeP+PrP exposure disrupts the normal HPA axis.

Exposure to phthalates, phenols, and parabens mixture and alterations in sex steroid hormones among adolescents

Exposure to phthalates (PAEs), phenols, and parabens has been linked with sex hormone imbalance; however, previous studies were predominantly limited to adults and failed to examine the combined effects of these chemicals mixture among adolescents. Thus, we used the data from the National Health and Nutrition Examination Survey (2013-2016) to explore the associations of urinary PAEs, phenols, and parabens biomarkers with sex hormones among participants aged 12-19 years old (n = 613). Latent class analysis (LCA) and quantile-based g-computation (QGC) were applied to assess the associations of the latent exposure profiles and chemicals mixture with sex hormone indicators, including steroid hormones and sex hormone binding globulin (SHBG), in adolescents and by sex. Using LCA, four latent classes were identified among all participants. Compared with the class characterized by "Low exposure", the class represented by "High PAEs" [mono (2-ethyl-5-carboxypentyl) phthalate (MECPP), mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and monobenzyl phthalate (MBZP)] had lower level of estradiol (E₂) [β = -0.249, 95% confidence interval (CI): -0.419, -0.08], free androgen index (FAI) (β = -0.258, 95%CI: -0.512, -0.005) and free testosterone (FT) (β = -0.248, 95%CI: -0.496, -0.001) among male adolescents. These results were echoed by the results in QGC analyses, where PAEs mixture was negatively associated with E₂ (β = -0.137, 95% CI: -0.263, -0.011), FAI (β = -0.198, 95%CI: -0.387, -0.008) and FT (β = -0.189, 95%CI: -0.375, -0.002) among male adolescents. By contrast, the associations of the identified latent classes or chemicals mixture with sex hormone indicators were generally nonsignificant among female counterparts, except for a positive association between PAEs mixture and SHBG (β = 0.121, 95%CI: 0.012, 0.23). Our study demonstrated that exposure to PAEs, particularly MECPP, MEHHP, and MBZP, would be a threat to the sex hormone homeostasis of male adolescents.

Endocrine-Disrupting Chemicals and Breast Cancer: Disparities in Exposure and Importance of Research Inclusivity

Endocrine-disrupting chemicals (EDCs) are known contributors to breast cancer development. Exposures to EDCs commonly occur through food packaging, cookware, fabrics, and personal care products, as well as external environmental sources. Increasing evidence highlights disparities in EDC exposure across racial/ethnic groups, yet breast cancer research continues to lack the inclusion necessary to positively impact treatment response and overall survival in socially disadvantaged populations. Additionally, the inequity in environmental exposures has yet to be remedied. Exposure to EDCs due to structural racism poses an unequivocal risk to marginalized communities. In this review, we summarize recent epidemiological and molecular studies on 2 lesser-studied EDCs, the per- and polyfluoroalkyl substances (PFAS) and the parabens, the health disparities that exist in EDC exposure between populations, and their association with breast carcinogenesis. We discuss the importance of understanding the relationship between EDC exposure and breast cancer development, particularly to promote efforts to mitigate exposures and improve breast cancer disparities in socially disadvantaged populations.

Identifying potential paraben transformation products and evaluating changes in toxicity as a result of transformation

Parabens are a class of compounds often used as preservatives in personal care products, pharmaceuticals, and food. They have received attention recently due to findings that demonstrate estrogenic impacts and other adverse effects of parabens. Release into wastewater effluent is considered a major contributor to the spread of parabens into surface water. Current regulations in areas such as Japan, Europe, and Southeast Asia limit the concentrations of parabens that can be used in formulations but do not address concentrations discharged into waterbodies. Recent studies suggest that parent parabens are effectively eliminated by transformation during the wastewater treatment processes. Common tertiary treatments include ultrafiltration, chlorination, UV disinfection and ozonation. Ultrafiltration is used to remove solids before a disinfection step. Of the disinfection steps, ozonation is often the most effective at removing parabens. Not much is known about the toxicities of paraben transformation products. Of the transformation products, chlorinated parabens and PHBA are the most studied. Previous studies have shown that chlorinated parabens have greatly reduced estrogen agonistic activity when compared with the activity of parents. However, more recent studies have found that halogenated parabens actually have estrogen antagonistic activity. Further research involving chlorinated parabens could include other toxic endpoints. No known studies have evaluated adverse effects of oxygenated parabens. Parabens can interact with chlorine residues in the environment and form chlorinated products, this will occur at a faster rate during chlorination. Ozonation will oxidize parabens and UV disinfection can both oxidize and halogenate parabens. All studies determining potential transformation products have been done in laboratory settings or specific conditions. Further research is needed to determine if these transformations occur in situ. PRACTITIONER POINTS: Common chemical processes utilized by wastewater treatment facilities are effective at transforming parabens. Paraben transformation products are released in greater concentration in effluent than parent paraben compounds. Halogenated transformation products have been identified as estrogen receptor antagonists.

Trends in environmental chemical concentrations in the Canadian population: Biomonitoring data from the Canadian Health Measures Survey 2007-2017

Ten years of nationally representative biomonitoring data collected between 2007 and 2017 are available from the Canadian Health Measures Survey (CHMS). These data establish baseline environmental chemical concentrations in the general population. Here we sought to evaluate temporal trends in environmental chemical exposures in the Canadian population by quantifying changes in biomarker concentrations measured in the first five two-year cycles of the CHMS. We identified 39 chemicals that were measured in blood or urine in at least three cycles and had detection rates over 50% in the Canadian population. We calculated geometric mean concentrations for each cycle using the survey weights provided. We then conducted analyses of variance to test for linear trends over all cycles. We also calculated the percent difference in geometric means between the first and most recent cycle measured. Of the 39 chemicals examined, we found statistically significant trends across cycles for 21 chemicals. Trends were decreasing for 19 chemicals from diverse chemical groups, including metals and trace elements, phenols and parabens, organophosphate pesticides, per- and polyfluoroalkyl substances, and plasticizers. Significant reductions in chemical concentrations included di-2-ethylhexyl phthalate (DEHP; 75% decrease), perfluorooctane sulfate (PFOS; 61% decrease), perfluorooctanoic acid (PFOA; 58% decrease), dimethylphosphate (DMP; 40% decrease), lead (33% decrease), and bisphenol A (BPA; 32% decrease). Trends were increasing for two pyrethroid pesticide metabolites, including a 110% increase between 2007 and 2017 for 3-phenoxybenzoic acid (3-PBA). No significant trends were observed for the remaining 18 chemicals that included arsenic, mercury, fluoride, acrylamide, volatile organic compounds, and polycyclic aromatic hydrocarbons. National biomonitoring data indicate that concentrations, and therefore exposures, have decreased for many priority chemicals in the Canadian population. Concentrations for other chemical groups have not changed or have increased, although average concentrations remain below thresholds of concern derived from human exposure guidance values. Continued collection of national biomonitoring data is necessary to monitor trends in exposures over time.

Prenatal exposure to propylparaben at human-relevant doses accelerates ovarian aging in adult mice

Embryonic exposure to environmental chemicals may result in specific chronic diseases in adulthood. Parabens, a type of environmental endocrine disruptors widely used in pharmaceuticals and cosmetics, have been shown to cause a decline in women's reproductive function. However, whether exposure to parabens during pregnancy also negatively affect the ovarian function of the female offspring in adulthood remains unclear. This study aims to investigate the effects of prenatal propylparaben (PrP) exposure on the ovarian function of adult mice aged 46 weeks, which is equivalent to the age of 40 years in women. Pregnant ICR mice were intraperitoneally injected with human-relevant doses of PrP (i.e., 0, 7.5, 90, and 450 mg/kg/day) during the fetal sex determination period-from embryonic day E7.5 to E13.5. Our results revealed that ovarian aging was accelerated in PrP-exposed mice at 46 weeks, with altered regularity of the estrous cycle, decreased serum estrogen (E2) and progesterone (P4) levels, reduced size of the primordial follicle pool, and increased number of atretic follicles. It was found that prenatal exposure to human-relevant doses of PrP exacerbated ovarian oxidative stress, inflammation, and fibrosis, which promoted follicular atresia by activating the mitochondrial apoptosis pathway. To compensate, the depletion of primordial follicles was also accelerated by activating the PI3K/AKT/mTOR signaling pathway in PrP-exposed mice. Moreover, PrP induced hypermethylation of CpG sites in the promoter region of Cyp11a1 (a 17.16-64.28% increase) partly led to the disrupted steroidogenesis, and the altered methylation levels of imprinted genes H19 and Peg3 may also contribute to the phenotypes observed. These remarkable findings highlight the embryonic origin of ovarian aging and suggest that a reduced use of PrP during pregnancy should be advocated.

Occurrence of parabens, triclosan and triclocarban in paired human urine and indoor dust from two typical cities in China and its implications for human exposure

Parabens, triclosan (TCS) and triclocarban (TCC) are emerging endocrine disrupting chemicals, which are commonly used in personal care products and household applications in daily life. Due to their adverse health effects, human exposure to these chemicals has been a public concern. Despite evidence showing different exposure pathways of these chemicals, few studies have examined contribution of certain exposure to total human exposure. In this study, we measured six parabens, TCS and TCC in 129 indoor dust samples and these chemicals plus four paraben metabolites in 203 urine samples from two different cities in China (Suizhou, a typical small city in central China and Beijing, the capital of China). The median concentrations of ∑₆Parabens (1050 ng/g) and ∑TCS + TCC (565 ng/g) in dusts from Beijing were 1.9-3.3 times higher than those from Suizhou (∑₆Parabens: 314, ∑TCS + TCC: 294 ng/g). The ∑₆Parabens in urines from Suizhou and Beijing were in the range of 0.208-645 and 0.455-2300 μg/g Creatinine (Cr), respectively. The ∑TCS + TCC concentrations in urine were 1-2 orders of magnitude lower than those found for ∑₆Parabens. Comparatively, women had relatively higher body burden of parabens than men, which was more noticeable when considering the use of skin care products. In this regard, relatively higher levels of parabens were also found in women in couples. Positive correlations were found between concentrations of methyl-paraben (MeP) and ethyl-paraben (PrP) in paired dust and urine samples (p < 0.05). Human exposure to such chemicals was evaluated. Based on the measured concentrations in paired human urine and indoor dust samples, our results provided direct evidence that the contribution of indoor dust ingestion to the total exposure was minor. These findings are essential for clarifying the sources and potential exposure routes of these chemicals in humans.

Urinary benzophenones and synthetic progestin in Chinese adults and children: concentration, source and exposure

The endocrine-disrupting activities of UV filters and synthetic progestin have raised concerns about their adverse risks. In this study, 208 urine samples were collected from Shanghai residents for the determination of seven benzophenones (BPs) and six synthetic progestins. The highest median concentration (6.21ng g^-1 Cr) was observed in young adults (21-50 years), followed by a concentration of 3.86 ng g^-1 Cr in elderly adults (over 50 years old), and the lowest median concentration (1.32 ng g^-1 Cr) was found in children (8-11 years old). The detection rates of BP-3 and EE2 in adults were 97% and 82%, and in children were 31% and 24%, respectively. Synthetic progestin levels in Shanghai, China, were relatively low compared to other countries. And the urinary BPs level showed an increasing trend in Chinese in the past 5 years. The principal component analysis suggested that adults' exposure to BP-1 and BP-3 was related, which occurs through food or dermal absorption of these chemicals present in cosmetic products and coatings. And diet was an important exposure pathway for children exposed to BPs. Despite relatively high levels of synthetic progestin for female and obese, the total estimated daily intake (EDI) was still lower than acceptable daily intake adopted by America. In the Monte-Carlo analysis, the 95th percentile of hazard quotients (HQs) was 0.83, which indicated that potential health risks were appreciated in the studied population.

Variability of urinary creatinine, specific gravity, and osmolality over the course of pregnancy: Implications in exposure assessment among pregnant women

Due to dilution status of the urine, chemical concentrations measured in spot urine are frequently adjusted using correction factors, such as creatinine, specific gravity (SG), or osmolarity of the urine. Urinary correction factors, however, can be influenced dramatically by physiological changes such as pregnancy. Details about the variation of urine dilution over the course of pregnancy are not well characterized. In the present study, we investigated the variation of urine correction factors over time among the pregnant women of Korea (n = 69) and Thailand (n = 102). Creatinine, SG, and osmolality were determined in the urine samples obtained in each trimester of the participating women, and were compared by sampling time and by nationality. Implication of the variation in these correction factors was studied using phthalate metabolites measured in the urine samples as model chemicals. Urinary correction factors significantly varied across the trimesters especially in Korean pregnant women: urinary creatinine and osmolality were significantly lower in the third trimester (T3) urine than the first trimester (T1) urine. Urinary creatinine and SG of the T3 urine of Korean pregnant women were also significantly lower than those reported from the non-pregnant women who participated in Korean National Environmental Health Survey (KoNEHS) 2015-2017. Among Thai women, however, these correction factors were rather stable across the pregnancy. Differences in ethnicity, or in behavior such as water consumption amount may partly explain the differences. Temporal changes in these urine correction factors influenced the urinary phthalate metabolite concentrations adjusted for dilution, in both Korean and Thai pregnant women. The present observations show that the variations of urinary correction factors should be considered in exposure assessment of urinary chemicals for pregnant women, in order to circumvent potential bias due to physiological changes occurring during pregnancy, and to reduce errors in exposure classification and association.

Exposure to parabens and associations with oxidative stress in adults from South China

Parabens are widely applied as preservatives in cosmetics, drugs and food. Previous studies suggested that parabens could exhibit potential risks to human health. However, data on human exposure levels and health effects of parabens remain limited, especially in the potential effects on DNA oxidative stress. This study aimed to investigate urinary levels of parabens in adults from South China and explore the relationships between urinary parabens and DNA oxidative stress. Five short chain parabens, including methyl paraben (MeP), ethyl paraben (EtP), n-propyl paraben (PrP), butyl paraben (BuP) and benzyl paraben (BzP), were determined in urine from 319 adults in Shenzhen, China. MeP, EtP and PrP were frequently detected in urine samples (detection frequencies >66.5%), suggesting broad exposure in South China adults. Median concentrations of MeP, EtP, PrP, BuP and BzP were 5.78, 0.39, 0.35, 0.01 and 0.02 μg/L, respectively. A significantly positive correlation was observed between the urinary concentrations of MeP and PrP (p < 0.01), suggesting similar sources for these two chemicals. In addition, participants with alcohol consumption exhibited significantly lower paraben concentrations in urine than those without alcohol drinking (p < 0.05). Significant association was observed between urinary concentrations of parabens and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels (p < 0.01), while no significant dose-response relationship was found (p > 0.05). A potential risk from PrP exposure was found in South China adults.

Role of Endocrine-Disrupting Chemicals in the Pathogenesis of Non-Alcoholic Fatty Liver Disease: A Comprehensive Review

Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder, affecting around 25% of the population worldwide. It is a complex disease spectrum, closely linked with other conditions such as obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome, which may increase liver-related mortality. In light of this, numerous efforts have been carried out in recent years in order to clarify its pathogenesis and create new prevention strategies. Currently, the essential role of environmental pollutants in NAFLD development is recognized. Particularly, endocrine-disrupting chemicals (EDCs) have a notable influence. EDCs can be classified as natural (phytoestrogens, genistein, and coumestrol) or synthetic, and the latter ones can be further subdivided into industrial (dioxins, polychlorinated biphenyls, and alkylphenols), agricultural (pesticides, insecticides, herbicides, and fungicides), residential (phthalates, polybrominated biphenyls, and bisphenol A), and pharmaceutical (parabens). Several experimental models have proposed a mechanism involving this group of substances with the disruption of hepatic metabolism, which promotes NAFLD. These include an imbalance between lipid influx/efflux in the liver, mitochondrial dysfunction, liver inflammation, and epigenetic reprogramming. It can be concluded that exposure to EDCs might play a crucial role in NAFLD initiation and evolution. However, further investigations supporting these effects in humans are required.

Parabens in urine of children and adolescents in Germany - human biomonitoring results of the german environmental survey 2014-2017 (GerES V)

Parabens are antimicrobial preservatives used in a wide range of consumer products such as personal care products, cosmetics, pharmaceuticals, and food. Consequently, the general population is ubiquitously exposed to these substances via dermal absorption, ingestion, and inhalation. Parabens promote estrogenic activity and are hence under assessment as endocrine disrupting substances. Urine samples from 3- to 17-year-old children and adolescents (N = 516) living in Germany were analysed for concentrations of nine parabens in the population representative German Environmental Survey for Children and Adolescents 2014-2017 (GerES V). Detection rates and urinary concentrations of the parabens decreased with increasing length of the alkyl chain. Methyl paraben was quantified in 97% of the samples with a geometric mean (GM) concentration of 7.724 μg/L (6.714 μg/g_creatinine), ethyl paraben was quantified in 69% (GM: 0.943 μg/L and 0.825 μg/g_crea), and n-propyl paraben in 31% (GM: 0.563 μg/L and 0.493 μg/g_crea). Concentrations of iso-propyl paraben, butyl paraben, iso-butyl paraben, and benzyl paraben were below the limit of quantification in most samples. Pentyl paraben and heptyl paraben were not detected in any of the samples. Paraben concentrations in urine were found to be associated with frequent usage of leave-on personal care products and cosmetics. Cumulative exposure to parabens (back-calculated daily intakes, expressed as hazard index) was found to be on a level raising concern in up to 14% of the population, mainly driven by n-propyl paraben, and depending on the level of conservativeness and point-of departures used for calculation.

The controversies of parabens - an overview nowadays

Effects of paraben toxicity, i.e., endocrine-disruption properties, are in the focus of researchers for decades, but still - they are a hot subject of debate. Parabens are aliphatic esters of p-hydroxybenzoic acid, which are widely used as antimicrobial agents for the preservation of cosmetics, pharmaceuticals and foods. Mostly used parabens are methyl-, ethyl-, propyl- and butylparaben. Although the toxicity of parabens is reported in animals and in in vitro studies, it cannot be taken for granted when discussing hazards for human health due to an unrealistic exposure -safety profile. Many studies have demonstrated that parabens are non-teratogenic, non-mutagenic, non-carcinogenic and the real evidence for their toxicity in humans has not been established. For now, methyl-, ethyl- and propylparaben are considered safe for use in cosmetics and pharmaceuticals within the recommended range of doses. Regarding alternatives for parabens, a variety of approaches have been proposed, but every substitute would need to be tested rigorously for toxicity and safety.

Accurate assessment of parabens exposure in healthy Chinese female adults: Findings from a multi-pathway exposure assessment coupled with intervention study

Exposure of humans to parabens is widespread and urinary parabens are widely used as exposure biomarkers. However, are the levels of these chemicals suitable to assess exposure to parabens? We conducted an intervention study by controlling the use of personal care products (PCPs) to explore the exposure of parabens. Ten female participants were recruited who were treated with different types of PCPs during the 18-day study period. The concentrations of parabens and their metabolites in matrices of different exposure pathways (dust, drinking water and dietary food) and urine samples were determined. We demonstrated that PCPs were the major sources of parabens, accounting for >99% of total exposure. The metabolites were nonspecific to individual parabens and could not be used as exposure biomarkers. Urinary paraben concentrations were positively correlated with external exposure levels. However, poor reproducibility was observed, with intraclass correlation coefficients (ICC) ranging from 0.125 to 0.295 in unadjusted urinary concentrations. Creatinine-adjusting could not significantly improve the ICC values in random spot samples. After adjusting for both creatinine and kinetic models, the ICC values ranged from 0.695 to 0.886, indicating a good reproducibility. So, toxicokinetic parameters may be taken into consideration for precise monitoring of exposures for the non-persistent pollutants.

Application of grouping and read-across for the evaluation of parabens of different chain lengths with a particular focus on endocrine properties

This article presents the outcomes of higher-tier repeated-dose toxicity studies and developmental and reproductive toxicity (DART) studies using Wistar rats requested for methyl paraben and propyl paraben under the European Union chemicals legislation. All studies revealed no-observed adverse effects (NOAELs) at 1000 mg/kg body weight/day. These findings (absence of effects) were then used to interpolate the hazard profile for ethyl paraben, further considering available data for butyl paraben. The underlying read-across hypothesis (all shorter-chained linear n-alkyl parabens are a ‘category’ based on very high structural similarity and are transformed to a common compound) was confirmed by similarity calculations and comparative in vivo toxicokinetics screening studies for methyl paraben, ethyl paraben, propyl paraben and butyl paraben. All four parabens were rapidly taken up systemically following oral gavage administration to rats, metabolised to p-hydroxybenzoic acid, and rapidly eliminated (parabens within one hour; p-hydroxybenzoic acid within 4–8 h). Accordingly, for ethyl paraben, the NOAELs for repeated-dose toxicity and DART were interpolated to be 1000 mg/kg body weight/day. Finally, all evidence was evaluated to address concerns expressed in the literature that parabens might be endocrine disruptors. This evaluation showed that the higher-tier studies do not provide any indication for any endocrine disrupting property. This is the first time that a comprehensive dataset from higher-tier in vivo studies following internationally agreed test protocols has become available for shorter-chained linear n-alkyl parabens. Consistently, the dataset shows that these parabens are devoid of repeated-dose toxicity and do not possess any DART or endocrine disrupting properties.

Assessing the Public Health Implications of the Food Preservative Propylparaben: Has This Chemical Been Safely Used for Decades

PURPOSE

Parabens are chemicals containing alkyl-esters of p-hydroxybenzoic acid, which give them antimicrobial, antifungal, and preservative properties. Propylparaben (PP) is one paraben that has been widely used in personal care products, cosmetics, pharmaceuticals, and food. In this review, we address the ongoing controversy over the safety of parabens, and PP specifically. These chemicals have received significant public attention after studies published almost 20 years ago suggested plausible associations between PP exposures and breast cancer.

RECENT FINDINGS

Here, we use key characteristics, a systematic approach to evaluate the endocrine disrupting properties of PP based on features of "known" endocrine disruptors, and consider whether its classification as a "weak" estrogen should alleviate public health concerns over human exposures. We also review the available evidence from rodent and human studies to illustrate how the large data gaps that exist in hazard assessments raise concerns about current evaluations by regulatory agencies that PP use is safe. Finally, we address the circular logic that is used to suggest that because PP has been used for several decades, it must be safe. We conclude that inadequate evidence has been provided for the safe use of PP in food, cosmetics, and consumer products.

Assessment of the Emerging Threat Posed by Perfluoroalkyl and Polyfluoroalkyl Substances to Male Reproduction in Humans

Per-fluoroalkyl and polyfluoroalkyl substances (PFAS) are a diverse group of synthetic fluorinated chemicals used widely in industry and consumer products. Due to their extensive use and chemical stability, PFAS are ubiquitous environmental contaminants and as such, form an emerging risk factor for male reproductive health. The long half-lives of PFAS is of particular concern as the propensity to accumulate in biological systems prolong the time taken for excretion, taking years in many cases. Accordingly, there is mounting evidence supporting a negative association between PFAS exposure and an array of human health conditions. However, inconsistencies among epidemiological and experimental findings have hindered the ability to definitively link negative reproductive outcomes to specific PFAS exposure. This situation highlights the requirement for further investigation and the identification of reliable biological models that can inform health risks, allowing sensitive assessment of the spectrum of effects of PFAS exposure on humans. Here, we review the literature on the biological effects of PFAS exposure, with a specific focus on male reproduction, owing to its utility as a sentinel marker of general health. Indeed, male infertility has increasingly been shown to serve as an early indicator of a range of co-morbidities such as coronary, inflammatory, and metabolic diseases. It follows that adverse associations have been established between PFAS exposure and the incidence of testicular dysfunction, including pathologies such as testicular cancer and a reduction in semen quality. We also give consideration to the mechanisms that render the male reproductive tract vulnerable to PFAS mediated damage, and discuss novel remediation strategies to mitigate the negative impact of PFAS contamination and/or to ameliorate the PFAS load of exposed individuals.

Wastewater-based epidemiology to assess human exposure to personal care and household products - A review of biomarkers, analytical methods, and applications

Humans are nowadays exposed to numerous chemicals in our day-to-day life, including parabens, UV filters, phosphorous flame retardants/plasticizers, bisphenols, phthalates and alternative plasticizers, which can have different adverse effects to human health. Estimating human's exposure to these potentially harmful substances is, therefore, of paramount importance. Human biomonitoring (HBM) is the existing approach to assess exposure to environmental contaminants, which relies on the analysis of specific human biomarkers (parent compounds and/or their metabolic products) in biological matrices from individuals. The main drawback is its implementation, which involves complex cohort studies. A novel approach, wastewater-based epidemiology (WBE), involves estimating exposure from the analysis of biomarkers in sewage (a pooled urine and feces sample of an entire population). One of the key challenges of WBE is the selection of biomarkers which are specific to human metabolism, excreted in sufficient amounts, and stable in sewage. So far, literature data on potential biomarkers for estimating exposure to these chemicals are scattered over numerous pharmacokinetic and HBM studies. Hence, this review provides a list of potential biomarkers of exposure to more than 30 widely used chemicals and report on their urinary excretion rates. Furthermore, the potential and challenges of WBE in this particular field is discussed through the review of pioneer WBE studies, which for the first time explored applicability of this novel approach to assess human exposure to environmental contaminants. In the future, WBE could be potentially applied as an "early warning system", which could promptly identify communities with the highest exposure to environmental contaminants.

Evaluation of 1-year urinary excretion of eight metabolites of synthetic pyrethroids, chlorpyrifos, and neonicotinoids

Synthetic pyrethroids, chlorpyrifos, and neonicotinoids are representatives of non-persistent insecticides ubiquitously used against insects all over the world. Their widespread use causes prevalent exposure to these compounds, which may be hazardous to human health. The insecticides have short biological half-lives and are mostly excreted in urine within 24 h after entering the human body; thus, the urinary concentration of their metabolites is highly dependent on the time elapsed between exposure and sample collection. Considering the within-day fluctuations in urinary concentration, one randomly collected sample may cause misclassification of long-term exposure. We evaluated the variability of excretion of eight insecticide metabolites in 24-h urine samples collected from 14 volunteers once or twice per month over 12 consecutive months. High detection frequency above 70% for non-specific metabolites of pyrethroid, chlorpyrifos, and neonicotinoids confirmed widespread exposure to these insecticides in the studied population. A long-term variability of exposure was assessed based on intraclass correlation coefficient (ICC). We found relatively low variability of excretion for non-specific pyrethroid metabolites and 3,5,6-trichloro-2-pyridinol (ICC > 0.75), but poor repeatability for 6-chloronicotinic acid. Constantly higher ICCs were observed for daily excretion than for unadjusted concentrations. Seasonal differences were observed for 3,5,6-trichloro-2-pyridinol and 6-chloronicotinic acid, with the highest and the lowest median concentration, respectively, in the summer. Due to high ICC values and lack of seasonal variations, one 24-h urine sample was considered sufficient to characterize long-term excretion of non-specific pyrethroid metabolites in non-occupationally exposed population. In addition, we calculated the daily intake (DI) for cypermethrin, permethrin, deltamethrin, and chlorpyrifos. The estimated DI values were mostly below the acceptable daily intake, which indicates that the evaluated exposure is non-hazardous to the population.

Propylparaben Reduces the Long-Term Consequences in Hippocampus Induced by Traumatic Brain Injury in Rats: Its Implications as Therapeutic Strategy to Prevent Neurodegenerative Diseases

BACKGROUND

Severe traumatic brain injury (TBI), an important risk factor for Alzheimer's disease, induces long-term hippocampal damage and hyperexcitability. On the other hand, studies support that propylparaben (PPB) induces hippocampal neuroprotection in neurodegenerative diseases.

OBJECTIVE

Experiments were designed to evaluate the effects of subchronic treatment with PPB on TBI-induced changes in the hippocampus of rats.

METHODS

Severe TBI was induced using the lateral fluid percussion model. Subsequently, rats received subchronic administration with PPB (178 mg/kg, TBI+PPB) or vehicle (TBI+PEG) daily for 5 days. The following changes were examined during the experimental procedure: sensorimotor dysfunction, changes in hippocampal excitability, as well as neuronal damage and volume.

RESULTS

TBI+PEG group showed sensorimotor dysfunction (p < 0.001), hyperexcitability (64.2%, p < 0.001), and low neuronal preservation ipsi- and contralateral to the trauma. Magnetic resonance imaging (MRI) analysis revealed lower volume (17.2%; p < 0.01) and great damage to the ipsilateral hippocampus. TBI+PPB group showed sensorimotor dysfunction that was partially reversed 30 days after trauma. This group showed hippocampal excitability and neuronal preservation similar to the control group. However, MRI analysis revealed lower hippocampal volume (p < 0.05) when compared with the control group.

CONCLUSION

The present study confirms that post-TBI subchronic administration with PPB reduces the long-term consequences of trauma in the hippocampus. Implications of PPB as a neuroprotective strategy to prevent the development of Alzheimer's disease as consequence of TBI are discussed.

Exposure to parabens and prevalence of obesity and metabolic syndrome: An analysis of the Canadian Health Measures Survey

BACKGROUND

Parabens are group of widely used preservative agents in the cosmetic, food, and pharmaceutical industries. They are estrogenic and anti-androgenic, and thus have the potential to alter the hormonal regulation of energy metabolism, and in turn affect obesity and metabolic health. Compared to obesity alone, having metabolic syndrome (a cluster of cardiometabolic risk factors) further increases the risk of cardiovascular disease, diabetes, and certain cancers. We examined whether exposure to parabens was associated with obesity, metabolic syndrome or its components among Canadians.

METHODS

Methyl, ethyl, propyl, and butyl paraben concentrations were measured in the urine of 2,564 individuals participating in Cycle 4 (2014-2015) of the Canadian Health Measures Survey, a national biomonitoring survey. We assessed associations between specific gravity-corrected log10-transformed paraben concentrations and obesity, metabolic syndrome and its components (waist circumference, HDL cholesterol, triglycerides, fasting blood glucose and blood pressure) via Poisson regression with robust variance estimators for binary outcomes and via linear regression for outcomes expressed continuously. We stratified analyses by age (children aged 3 to 17 years vs. adults aged 18 years and older) and investigated the presence of effect modification by sex.

RESULTS

A 10-fold increase in propyl paraben concentration was associated with a 40% (95% CI: 3, 90) higher prevalence of metabolic syndrome among men, while ethyl paraben was associated with a 63% (95% CI: 2, 86) lower prevalence among women. Among women, methyl paraben was inversely associated with obesity, and methyl, propyl and ethyl parabens were associated with higher high density lipoprotein (HDL) cholesterol. No associations were observed among children.

CONCLUSIONS

This is the first study to report a positive association between parabens and metabolic syndrome in men. Protective associations among women previously reported for obesity were also observed for metabolic syndrome and HDL cholesterol. These results should be confirmed in longitudinal studies.

Use of personal care products during pregnancy in relation to urinary concentrations of select phenols: A longitudinal analysis from the SEPAGES feasibility study

BACKGROUND

Exposure to certain synthetic phenols is of growing concern, in particular among pregnant women, because of their endocrine disrupting nature. Many phenols are still authorized in personal care products (PCP). We aimed to assess if use of PCPs, by pregnant women could influence their urinary concentrations of synthetic phenols.

METHODS

We used a panel design with intense urine sample collection. Eight women completed a diary with exact time and use of PCPs in three weeks. We measured the concentrations of phenols (four parabens, bisphenol A and S, two dichlorophenols, triclosan, and benzophenone-3) in 178 urine samples, collected during 7 consecutive days at 3 time points during pregnancy. We characterized PCP use as the total number of PCP applications or as a single PCP use (yes/no) in three time windows (0-6, 6 to 12 and 12 to 24h before each urine sample collection). We used adjusted linear and Tobit regressions to assess associations between PCP use and phenol urinary concentrations.

RESULTS

The total number of PCP applications was positively associated with ethylparaben, propylparaben and butylparaben concentrations. We observed a peak in urinary concentration of ethylparaben, butylparaben and propylparaben at 2.86, 2.55 and 2.67 h since last PCP use, respectively and twelve different types of PCPs were positively associated with at least one of these parabens. The bisphenol S concentration increased by 12.4% (95%CI: confidence interval: 5.9; 19.3) for each additional PCP application in the 12 to 24 time window and use of specific PCPs such as anti-stretchmarks cream, facial cleanser and shower gel. Associations varied by time window.

CONCLUSION

Our study showed that PCP use was associated with a short-term increase in the urinary concentration of ethylparaben, butylparaben and propylparaben, but not methylparaben. This study also reported a positive association between the use of PCPs and the bisphenol S concentration, a finding that warrants further investigation in cohorts with repeated collection of urine samples and detailed information on PCP use.

[Neonates exposure to parabens through medicines administered to inpatients]

OBJECTIVES

The objective of this study was to quantify parabens intake due to drug administration in neonates during hospitalization following their birth.

METHOD

A monocentric prospective study was performed into a neonatalogy unit to collect all drug prescriptions. An exhaustive list of parabens containing medicines commercialized in France was completed from Theriaque® database. This list was combined with drug prescription to establish an exposure profile to parabens. For each paraben containing medicines, a HPLC-UV assay was performed to determine the average daily intake of paraben received by hospitalized neonates.

RESULTS

More than 300 medicines commercialized in France contain at least one paraben. A combination of methylparaben and propylparaben was found in most cases. All hospitalized neonates (n=22) were exposed at least once to methylparaben and propylparaben through medicines while 50 % were exposed to ethylparaben. The average daily intake was higher in term newborns (572,0±249,0 versus 414,6±294,1μg/kg/j for methylparaben) but frequency was higher in prematures (65,0 versus 78,6% for methylparaben) as well as cumutives doses (1421,5±758,8 versus 8618,7±7922,3). These doses are lower than toxicological reference values but these latter do not take into account endocrine disrupting effects of these compounds.

CONCLUSIONS

These results highlight medicines as a high source of exposure to parabens in hospitalized neonates. It should encourage pharmaceutical companies and health professionnal to prioritize therapeutic cares without parabens.

Concentration and distribution of parabens, triclosan, and triclocarban in pregnant woman serum in China

Despite mass production and widespread use of parabens, triclosan (TCS), and triclocarban (TCC) in a range of personal care products, little is known about their concentrations and distribution in pregnant woman serum in China. In this study, 5 parabens (methyl- (MeP), ethyl- (EtP), butyl- (BuP), heptyl- (HeP) and benzyl-parabens (BzP)) and 4 their metabolites (methyl protocatechuate (OH-MeP), ethyl protocatechuate (OH-EtP), 3,4-dihydroxybenzoic acid (3,4-DHB) and 4-hydroxybenzoic acid (4-HB)), TCS, and TCC were measured, by using solid-phase extraction (SPE) and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) techniques, in pregnant woman serum samples collected from 13 provinces in China. Total concentrations of parabens (∑PBs), their metabolites (∑MBs), and TCC and TCS (∑AAs) in serum ranged from 0.221-18.6 (geometric mean (GM): 2.47), 47.4-598 (212), and 0.101-5.84 (1.01) ng/mL, respectively. MeP, EtP, 4-HB and TCS were the dominant compounds, and their GM concentrations were 1.86, 0.239, 211 and 1.00 ng/mL, respectively. Geographical distribution of target chemicals in serum was determined. Concentrations of MeP (5.49 ng/mL) and EtP (0.895 ng/mL) in sera from the Northeast China were higher than those from other regions (MeP: 0.987-3.54, EtP: 0.07-0.254 ng/mL; p < 0.05). The highest 4-HB concentrations were found in sera from the Southwest China (GM: 286 ng/mL), whereas the TCS concentrations in sera from the North China (1.18 ng/mL) were higher than those found for other regions (p < 0.05). The estimated daily intakes (EDIs; range: 49.5-126 μg/kg body weight (bw)/day) showed that the Chinese women were in a low health risk from exposure to such chemicals. This is the first study to report concentration profiles of parabens, TCS and TCC in pregnant woman serum in China.

Risk Assessment of Cosmetics Using Triclosan on Future Generation's Germ Cell Maturation via Lactating Mother Rats

Triclosan (TCS) is a widely used chemical in personal care and household products as an antimicrobial agent but some studies have reported it as being estrogenic. We investigated the influence of TCS on the male reproductive system of postnatal pups. Lactating mother rats (Rattus norvegicus) were given daily doses of 0 mg, 3 mg, and 5 mg/kg/day from the day of delivery until 28 days, equivalent to their natural breastfeeding duration. At 28 days, the male pups of all three groups were sacrificed and their biochemical parameters evaluated. TCS-treated pups had decreased mRNA levels for 3β hydro-hydroxysteroid dehydrogenases (3βHSD), OCT3/4, and androgen receptor (AR) (p < 0.05). The higher dose (5 mg/kg/day) male pups exhibited more significantly affected germ cell maturation and decreased body weight. In summary, TCS-treated lactating mothers passed the deleterious effects to their untreated male pups as exhibited by reduced androgens synthesis and subsequently decreased sperm count.

The Impact of Early-Life Exposure to Antimicrobials on Asthma and Eczema Risk in Children

PURPOSE OF REVIEW

We examined recent research on associations of prenatal and early-childhood exposure to the antimicrobial compounds, triclosan, and parabens, with the risk of asthma and eczema in children. We will discuss potential biological mechanisms of this association and highlight strengths and limitations of the study design and exposure assessment of current findings.

RECENT FINDINGS

Results of available toxicological and epidemiologic studies indicate a potential link of triclosan and paraben exposures with asthma and eczema in children, as well as changes in microbiome diversity and immune dysfunction, which could possibly mediate an association with the health outcomes. A small number of studies suggest that triclosan and paraben exposures could be related to the risk of asthma and eczema in children. Although current findings are far from conclusive, there is emerging evidence that changes in microbiome diversity and immune function from antimicrobial exposure may mediate these relations.

Presence of Bisphenol A and Parabens in a Neonatal Intensive Care Unit: An Exploratory Study of Potential Sources of Exposure

BACKGROUND

Newborns in neonatal intensive care units (NICUs) are in contact with a variety of medical products whose production might include synthetic chemicals with hormonal activity.

OBJECTIVES

Our aim was to assess the content of bisphenol A (BPA) and parabens (PBs) and the hormone-like activities of a subset of medical products commonly used in NICUs in prolonged intimate contact with NICU newborns.

METHODS

Fifty-two NICU items were analyzed, determining the concentrations of BPA and PBs [methyl- (MeP), ethyl- (EtP), propyl- (PrP), and butylparaben (BuP)] and using the E-Screen and PALM-luciferase assays to measure the in vitro (anti-)estrogenic and (anti-)androgenic activity, respectively, of the extracts. Items found to have elevated BPA/PB content or hormone-like activities were further extracted using leaching methodologies.

RESULTS

BPA was found in three-fifths and PBs in four-fifths of tested NICU items, and ∼25% and ∼10% of extracts evidenced estrogenic and anti-androgenic activity, respectively. The highest BPA content was found in the three-way stopcock (>7.000 ng/g), followed by patterned transparent film dressing, gastro-duodenal feeding tubes, sterile gloves, single-lumen umbilical catheters, and intravenous (IV) infusion extension sets (concentrations ranged from 100 to 700 ng/g BPA). A total PB concentration (∑PBs) >100 ng/g was observed in several items, including light therapy protection glasses, patterned transparent film dressing, winged IV catheters, IV infusion extension sets, and textile tape. The highest estrogenic activity [>450 pM estradiol equivalent (E2eq)] was found in small dummy nipples, three-way stopcocks, and patterned transparent film dressing and the highest anti-androgenic activity [>5 mM procymidone equivalent units per gram (Proceq/g)] in small dummy nipples and three-way stopcocks.

DISCUSSION

According to these findings, neonates might be exposed to multiple sources of BPA and PBs in NICUs via inhalation, dermal, oral, and IV/parenteral routes. There is a need to address the future health implications for these extremely vulnerable patients and to adopt precautionary preventive measures as a matter of urgency. https://doi.org/10.1289/EHP5564.