Reproductive and behavioral effects of diisononyl phthalate (DINP) in perinatally exposed rats

Thyroid and neurobehavioral effects of DiNP on GH3 cells and larval zebrafish (Danio rerio)

Diisononyl phthalate (DiNP) has been used to replace bis(2-ethylhexyl) phthalate (DEHP) and is frequently found in the environment and humans. DiNP is reported for its anti-androgenic activity; however, little is known about its effects on thyroid function and neurodevelopment. In the present study, the thyroid disruption and neurobehavioral alteration potential of DiNP and its major metabolites were assessed in a rat pituitary carcinoma cell line (GH3) and embryo-larval zebrafish (Danio rerio). In GH3 cells, exposure to DiNP and its metabolites not only increased proliferation but also induced transcriptional changes in several target genes, which were different from those observed with DEHP exposure. In larval fish, a 5-day exposure to DiNP caused significant increases in thyroid hormone levels, following a similar pattern to that reported for DEHP exposure. Following exposure to DiNP, the activity of the larval fish decreased, and neurodevelopment-related genes, such as c-fos, elavl3, and mbp, were down-regulated. These changes are generally similar to those observed for DEHP. Up-regulation of gap43 and down-regulation of elavl3 gene, which are important for both thyroid hormone production and neurodevelopment, respectively, support the potential for both thyroid and behavioral disruption of DiNP. Overall, these results emphasize the need to consider the adverse thyroid and neurodevelopmental effects in developing regulations for DEHP-replacing phthalates.

Phthalate esters in clothing: A review

Phthalate esters (PAEs) are widely used as plasticizers to enhance the flexibility and durability of different consumer products, including clothing. However, concerns have been raised about the potential adverse health effects associated with the presence of phthalates in textiles, such as endocrine disruption, reproductive toxicity and potential carcinogenicity. Based on examination of more than 120 published articles, this paper presents a comprehensive review of studies concerning the phthalate content in clothing and other textile products, with special emphasis on those conducted in the last decade (2014-2023). The types and role of PAEs as plasticizers, the relevant legislation in different countries (emphasizing the importance of monitoring PAE levels in clothing to protect consumer health) and the analytical methods used for PAE determination are critically evaluated. The review also discusses the models used to evaluate exposure to PAEs and the associated health risks. Finally, the study limitations and challenges related to determining the phthalate contents of textile products are considered.

Prenatal Exposure to Environmentally Relevant Low Dosage Dibutyl Phthalate Reduces Placental Efficiency in CD-1 Mice

Introduction

Dibutyl phthalate (DBP), a phthalate congener, is widely utilized in consumer products and medication coatings. Women of reproductive age have a significant burden of DBP exposure through consumer products, occupational exposure, and medication. Prenatal DBP exposure is associated with adverse pregnancy/fetal outcomes and cardiovascular diseases in the offspring. However, the role of fetal sex and the general mechanisms underlying DBP exposure-associated adverse pregnancy outcomes are unclear. We hypothesize that prenatal DBP exposure at an environmentally relevant low dosage adversely affects fetal-placental development and function during pregnancy in a fetal sex-specific manner.

Methods

Adult female CD-1 mice (8-10wks) were orally treated with vehicle (control) or with environmentally relevant low DBP dosages at 0.1 μg/kg/day (refer as DBP0.1) daily from 30 days before pregnancy through gestational day (GD) 18.5. Dam body mass composition was measured non-invasively using the echo-magnetic resonance imaging system. Lipid disposition in fetal labyrinth and maternal decidual area of placentas was examined using Oil Red O staining.

Results

DBP0.1 exposure did not significantly affect the body weight and adiposity of non-pregnant adult female mice nor the maternal weight gain pattern and adiposity during pregnancy in adult female mice. DBP0.1 exposure does not affect fetal weight but significantly increased the placental weight at GD18.5 (indicative of decreased placental efficiency) in a fetal sex-specific manner. We further observed that DBP0.1 significantly decreased lipid disposition in fetal labyrinth of female, but not male placentas, while it did not affect lipid disposition in maternal decidual.

Conclusions

Prenatal exposure to environmentally relevant low-dosage DBP adversely impacts the fetal-placental efficiency and lipid disposition in a fetal sex-specific manner.

Phthalates and uterine disorders

Humans are ubiquitously exposed to environmental endocrine disrupting chemicals such as phthalates. Phthalates can migrate out of products and enter the human body through ingestion, inhalation, or dermal application, can have potential estrogenic/antiestrogenic and/or androgenic/antiandrogenic activity, and are involved in many diseases. As a female reproductive organ that is regulated by hormones such as estrogen, progesterone and androgen, the uterus can develop several disorders such as leiomyoma, endometriosis and abnormal bleeding. In this review, we summarize the hormone-like activities of phthalates, in vitro studies of endometrial cells exposed to phthalates, epigenetic modifications in the uterus induced by phthalate exposure, and associations between phthalate exposure and uterine disorders such as leiomyoma and endometriosis. Moreover, we also discuss the current research gaps in understanding the relationship between phthalate exposure and uterine disorders.

What risk factors for Developmental Language Disorder can tell us about the neurobiological mechanisms of language development

Language is a complex multidimensional cognitive system that is connected to many neurocognitive capacities. The development of language is therefore strongly intertwined with the development of these capacities and their neurobiological substrates. Consequently, language problems, for example those of children with Developmental Language Disorder (DLD), are explained by a variety of etiological pathways and each of these pathways will be associated with specific risk factors. In this review, we attempt to link previously described factors that may interfere with language development to putative underlying neurobiological mechanisms of language development, hoping to uncover openings for future therapeutical approaches or interventions that can help children to optimally develop their language skills.

Mediation of endoplasmic reticulum stress and NF-κB signaling pathway in DINP-exacerbated allergic asthma: A toxicological study with Balb/c mice

Epidemiological evidence indicates a significant relationship between exposure to diisononyl phthalate and allergic asthma. Despite this, the mechanism underlying this association remains unclear. Previous toxicological researches have suggested that the development of allergic asthma may involve the activation of endoplasmic reticulum stress (ERS) and the nuclear factor κ-B (NF-κB) pathways. Nevertheless, it is currently unknown whether these specific signaling pathways are implicated in diisononyl phthalate (DINP)-induced allergic asthma. The objective of this research was to understand how DINP exacerbates allergic asthma in Balb/c mice through ERS and NF-κB pathways. To systematically examine the aggravated effects of DINP in Balb/c mice, we measured airway hyperresponsiveness (AHR), lung tissue pathology, cytokines, and ERS and NF-κB pathway biomarkers. Additionally, we applied the ERS antagonist phenylbutyric acid (4-PBA) or the NF-κB antagonist pyrrolidine dithiocarbamate (PDTC) to verify the mediating effects of ERS and NF-κB on DINP-exacerbated allergic asthma. The results of our experiment show that oral DINP exposure may exacerbate airway hyperresponsiveness and airway remodeling. This deterioration is accompanied by an imbalance in immunoglobulin levels, Th17/Treg cells, ERS, and NF-κB biomarkers, leading to the activation of pro-inflammatory pathways. Furthermore, our study found that the blocking effect of 4-PBA or PDTC can inhibit the Th17/Treg imbalance and effectively alleviate symptoms resembling allergic asthma. In conclusion, ERS and NF-κB signaling pathways play an important role in regulating DINP-induced allergic asthma exacerbations.

Endocrine disrupting chemicals and male fertility: from physiological to molecular effects

The deleterious effects of chemical or non-chemical endocrine disruptors (EDs) on male fertility potential is well documented but still not fully elucidated. For example, the detection of industrial chemicals' metabolites in seminal plasma and follicular fluid can affect efficiency of the gametogenesis, the maturation and competency of gametes and has guided scientists to hypothesize that endocrine disrupting chemicals (EDCs) may disrupt hormonal homoeostasis by leading to a wide range of hormonal control impairments. The effects of EDCs exposure on reproductive health are highly dependent on factors including the type of EDCs, the duration of exposure, individual susceptibility, and the presence of other co-factors. Research and scientists continue to study these complex interactions. The aim of this review is to summarize the literature to better understand the potential reproductive health risks of EDCs in France.

Are New Phthalate Ester Substitutes Safer than Traditional DBP and DiBP? Comparative Endocrine-Disrupting Analyses on Zebrafish Using In Vivo, Transcriptome, and In Silico Approaches

Although previous studies have confirmed the association between phthalate esters (PAEs) exposure and endocrine disorders in humans, few studies to date have systematically assessed the threats of new PAE alternatives to endocrine disruptions. Herein, zebrafish embryos were continuously exposed to two PAEs [di-n-butyl phthalate (DBP) and diisobutyl phthalate (DiBP)], two structurally related alternatives [diiononyl phthalate (DINP) and diisononyl hexahydrophthalate (DINCH)], and two non-PAE substitutes [dipropylene glycol dibenzoate (DGD) and glyceryl triacetate (GTA)], and the endocrine-disrupting effects were investigated during the early stages (8-48 hpf). For five endogenous hormones, including progesterone, testosterone, 17β-estradiol, triiodothyronine (T3), and cortisol, the tested chemicals disturbed the contents of at least one hormone at environmentally relevant concentrations (≤3.9 μM), except DINCH and GTA. Then, the concentration-dependent reduced zebrafish transcriptome analysis was performed. Thyroid hormone (TH)- and androgen/estrogen-regulated adverse outcome pathways (AOPs) were the two types of biological pathways most sensitive to PAE exposure. Notably, six compounds disrupted four TH-mediated AOPs, from the inhibition of deiodinases (molecular initiating event, MIE), a decrease in T3 levels (key event, KE), to mortality (adverse outcome, AO) with the quantitatively linear relationships between MIE-KE (|r| = 0.96, p = 0.002), KE-AO (|r| = 0.88, p = 0.02), and MIE-AO (|r| = 0.89, p = 0.02). Multiple structural analyses showed that benzoic acid is the critical toxicogenic fragment. Our data will facilitate the screening and development of green alternatives.

Persistent high exposure to exogenous phthalates and endogenous sex hormones associated with early pubertal onset among children: A 3.5-year longitudinal cohort study in China

BACKGROUND

Early onset of puberty could have significant impacts on childhood health, but the extent to which it was affected by phthalate esters (PAEs) and sex hormone disruption was not understood. The aim of this study is to investigate the associations between exposure to PAEs and sex hormone disruption and early onset of puberty in children.

METHODS

A longitudinal cohort study was conducted in China from May 2017 to Oct 2020, involving 740 children during consecutive visits. The onset of puberty was evaluated using Tanner definition, and early puberty was defined as an onset age less than the first 25 %, with cut-offs of 10.33 and 8.97 years for boys and girls, respectively. Serum testosterone (TT), estradiol (E₂) and urinary PAE metabolites were measured during three visits. Generalized linear models were used to explore the associations between PAE and sex hormones with the age of puberty onset, while log-binomial regressions were applied to assess the associations of persistent exposure to PAEs and sex hormones with early pubertal onset.

RESULTS

Approximately 86.0 % of boys and 90.2 % of girls completed puberty onset from pre-puberty, and more than 95 % of participants had PAE concentrations higher than the limit of detection. Boys showed higher exposure to PAE pollutants and higher TT levels. Persistent exposure to PAEs was positively associated with early pubertal onset in girls (ARR = 1.97, 95 %CI = 1.12, 3.46). Moreover, persistent exposure to PAEs and E₂ had synergistic associations with early pubertal onset in both boys (ARR = 4.77, 95 %CI = 1.06, 21.54) and girls (ARR = 7.07, 95 %CI = 1.51, 33.10). However, PAEs and TT had antagonistic associations only in boys (ARR = 0.44, 95 %CI = 0.07, 2.58).

CONCLUSION

Long-term exposure to PAEs might increase the risk of early pubertal onset, and it appears to work in synergy with E₂, while in antagonism with TT in boys' early pubertal onset. Reducing PAEs exposure might promote pubertal health.

Endocrine-Disrupting Chemicals and Hippocampal Development: The Role of Estrogen and Androgen Signaling

Hormones are important regulators of key processes during fetal brain development. Thus, the developing brain is vulnerable to the action of chemicals that can interfere with endocrine signals. Epidemiological studies have pointed toward sexually dimorphic associations between neurodevelopmental outcomes, such as cognitive abilities, in children and prenatal exposure to endocrine-disrupting chemicals (EDCs). This points toward disruption of sex steroid signaling in the development of neural structures underlying cognitive functions, such as the hippocampus, an essential mediator of learning and memory processes. Indeed, during development, the hippocampus is subjected to the organizational effects of estrogens and androgens, which influence hippocampal cell proliferation, differentiation, dendritic growth, and synaptogenesis in the hippocampal fields of Cornu Ammonis and the dentate gyrus. These early organizational effects correlate with a sexual dimorphism in spatial cognition and are subject to exogenous chemical perturbations. This review summarizes the current knowledge about the organizational effects of estrogens and androgens on the developing hippocampus and the evidence for hippocampal-dependent learning and memory perturbations induced by developmental exposure to EDCs. We conclude that, while it is clear that sex hormone signaling plays a significant role during hippocampal development, a complete picture at the molecular and cellular levels would be needed to establish causative links between the endocrine modes of action exerted by EDCs and the adverse outcomes these chemicals can induce at the organism level.

Reproductive toxicity of emerging plasticizers, flame retardants, and bisphenols, using culture of the rat fetal testis†

The use of bis (2-ethylhexyl) phthalate (DEHP), 2,2'4,4'-tetrabromodiphenyl ether (BDE47), and bisphenol A (BPA), as plasticizers, flame retardants, and epoxy resins, respectively, has been regulated due to their endocrine disrupting activities. Replacements for these chemicals are found in human matrices, yet the endocrine disrupting potential of these emerging contaminants is poorly characterized. We compared the effects of legacy chemicals with those of their replacements using fetal rat testis organ culture. Fetal testes sampled at gestation day 15 were grown ex vivo, and the impact was evaluated after a 3-day exposure to 10 μM of each legacy chemical; two BPA analogs (bisphenol M and bisphenol TMC); three replacements for DEHP/MEHP (2,2,4-trimethyl-1,3-pentanediol diisobutyrate, diisononyl-phthalate, and diisodecyl adipate); or two replacements for BDE47 (tributoxyethyl phosphate and isopropylated triphenyl phosphate). We showed that only BPA and MEHP significantly decrease testosterone secretions after 24 h, while BPM and BPTMC have the opposite effect. Luteinizing hormone-stimulated testosterone was reduced by BPA and MEHP but was increased by BPTMC. After exposure, testes were used for immunofluorescent staining of germ cells, Sertoli cells, and Leydig cells. Interestingly, exposures to BPM or BPTMC induced a significant increase in the Leydig cell density and surface area. A decrease in germ cell density was observed only after treatment with MEHP or BDE47. MEHP also significantly decreased Sertoli cell proliferation. These studies show that some replacement chemicals can affect testicular function, while others appear to show little toxicity in this model. These findings provide essential information regarding the need for their regulation.

Maternal phthalate exposure during pregnancy and testis function of young adult sons

BACKGROUND

Phthalate exposure during fetal life may disrupt testicular development. Congruent with this, studies have found shorter anogenital distance, reduced penile size and altered hormone levels in infant boys whose mothers were exposed to higher levels of some phthalates during pregnancy. Few studies have explored if such adverse effects persist in adulthood. Thus, we aimed to explore if there is an association between fetal phthalate exposure and markers of testicular function in young adult men.

METHODS

In a longitudinal mother-child cohort from Copenhagen, Denmark, we examined 100 young men whose mothers during pregnancy had serum drawn and analyzed for 34 phthalate metabolites. Examinations of the young men took place at 18-20 years of age and included measurements of adult markers of testicular function (reproductive hormones, penile size, anogenital distance (AGD), testis volume, semen quality) and growth factors. Associations between maternal serum concentrations of phthalate metabolites and reproductive measures in the young men were tested using multiple linear regression.

RESULTS

Most consistently, higher maternal phthalate exposure was associated with higher luteinizing hormone (LH) but unchanged testosterone in adult sons. Congruently, higher maternal exposure was associated with lower total and free testosterone/LH ratios in adult sons. For example, twice as high maternal MiNP was associated with a 7.9 % (95 % CI 1.6-13.8) lower free testosterone/LH ratio. There was no consistent pattern of associations between the different phthalate metabolites and other reproductive hormones, clinical outcomes, or semen quality. None of the tested associations was significant after multiplicity adjustment.

CONCLUSIONS

In this exploratory study, higher maternal exposure to some phthalates was associated with impaired testicular Leydig cell function evidenced by a lower total and free testosterone/LH ratio in adult sons. This unique 18-20-year follow-up study raises concern and suggests that exposure of pregnant women to phthalates may have long-term effects on adult reproductive health in male offspring.

Biologically relevant reductions in fetal testosterone and Insl3 induced by in utero exposure to high levels of di-isononyl phthalate (DINP) in male rats

Some phthalate esters alter male rat reproductive development during sexual differentiation by interfering with fetal testis maturation resulting in reduced Leydig Cell synthesis of testosterone and insulin-like 3 (Insl3) hormones. Gene transcripts associated with steroid hormone and cholesterol transport, and cholesterol synthesis and lipid metabolism also are reduced. These alterations cause permanent malformations of hormone-dependent tissues, sperm production and fertility in male offspring; effects known as the "Phthalate Syndrome." We have shown that administration of a high dose of 750 mg diisononyl phthalate (750 mg/kg/d DINP) during sex differentiation reduced fetal testis testosterone production (T Prod), testis gene expression and induced a low incidence of reproductive malformations in male rat offspring. In the current study we administered DINP at even higher dose levels (1.0 and 1.5 g/kg/d) from gestational day (GD) 14 to postnatal (PND) 3 to determine if these effects were dose related and if the magnitude of the effects could be predicted from a statistical model of fetal testosterone production (T Prod) and Insl3 mRNA levels. These models were previously developed using dipentyl phthalate (DPeP) data from fetal T Prod and postnatal studies. We found that the severity of the demasculinizing effects on the androgen-dependent organs and gubernaculum by DINP were accurately predicted from the statistical models of fetal T prod and Insl3 mRNA, respectively. Taken together, our results indicate that reductions fetal T prod and Insl3 predict the severity of demasculinizing effects in utero exposure to the phthalates DINP and DPeP regardless of potency.

Development, testing, parameterisation, and calibration of a human PBPK model for the plasticiser, di-(2-ethylhexyl) terephthalate (DEHTP) using in silico, in vitro and human biomonitoring data

A physiologically based pharmacokinetic model for di-(2-ethylhexyl) terephthalate (DEHTP) based on a refined model for di-(2-propylheptyl) phthalate (DPHP) was developed to interpret the metabolism and biokinetics of DEHTP following a single oral dose of 50 mg to three male volunteers. In vitro and in silico methods were used to generate parameters for the model. For example, measured intrinsic hepatic clearance scaled from in vitro to in vivo and plasma unbound fraction and tissue:blood partition coefficients (PCs) were predicted algorithmically. Whereas the development and calibration of the DPHP model was based upon two data streams, blood concentrations of parent chemical and first metabolite and the urinary excretion of metabolites, the model for DEHTP was calibrated against a single data stream, the urinary excretion of metabolites. Despite the model form and structure being identical significant quantitative differences in lymphatic uptake between the models were observed. In contrast to DPHP the fraction of ingested DEHTP entering lymphatic circulation was much greater and of a similar magnitude to that entering the liver with evidence for the dual uptake mechanisms discernible in the urinary excretion data. Further, the absolute amounts absorbed by the study participants, were much higher for DEHTP relative to DPHP. The in silico algorithm for predicting protein binding performed poorly with an error of more than two orders of magnitude. The extent of plasma protein binding has important implications for the persistence of parent chemical in venous blood-inferences on the behaviour of this class of highly lipophilic chemicals, based on calculations of chemical properties, should be made with extreme caution. Attempting read across for this class of highly lipophilic chemicals should be undertaken with caution since basic adjustments to PCs and metabolism parameters would be insufficient, even when the structure of the model itself is appropriate. Therefore, validation of a model parameterized entirely with in vitro and in silico derived parameters would need to be calibrated against several human biomonitoring data streams to constitute a data rich source chemical to afford confidence for future evaluations of other similar chemicals using the read-across approach.

Exposure to environmentally relevant doses of plasticizers alters maternal behavior and related neuroendocrine processes in primiparous and multiparous female mice

Phthalates are organic pollutants frequently detected in the environment. The effects of these substances on male reproduction have been extensively studied but their potential impact on female reproductive behaviors in particular at environmental doses still remains to be documented. In the present study, we examined the effects of chronic exposure to di (2-ethylhexyl) phthalate (DEHP) alone at 5 or 50 μg/kg/d, or in an environmental phthalate mixture on maternal behavior of lactating female mice after a first (primiparous) and a second gestation (multiparous). Exposure of DEHP alone or in a phthalate mixture reduced pup-directed behaviors, increased self-care and forced nursing behaviors and altered nest quality for both primiparous and multiparous dams. In pup-retrieval test, primiparous and multiparous dams exposed to DEHP alone or in a phthalate mixture retrieved their pups more rapidly, probably due to a higher emission of ultrasonic vocalizations by the pups. At lactational day 2 following the third and last gestational period, the neural circuitry of maternal behavior was analyzed. A lower number of oxytocin-immunoreactive neurons in the paraventricular and anterior commissural nuclei was found in dams exposed to DEHP alone or in a phthalate mixture, while no changes were observed in the number of arginine-vasopressin immunoreactive cells. In the medial preoptic area, exposure to DEHP alone or in a phthalate mixture reduced ERα-immunoreactive cell number. Dendritic spine density assessed for DEHP at 5 μg/kg/d was also reduced. Thus, exposure to DEHP alone or in a phthalate mixture altered maternal behavior probably through a neuroendocrine mode of action involving oxytocin and estrogen through ERα, key pathways necessary for neuroplasticity and behavioral processing.

Di-isononyl phthalate induces apoptosis and autophagy of mouse ovarian granulosa cells via oxidative stress

Di-isononyl phthalate (DINP) has been widely utilized in industrial, commercial and medical applications for the past few years. Therefore, more attention should be paid to the toxicity of DINP. DINP can cause damage to female reproductive system; however, the potential mechanism remains to be further investigated. In this study, female mice were orally administered with 0, 2, 20 and 200 mg DINP/kg/day for 14 days. We found that DINP significantly affected the arrangement of granulosa cells in ovarian follicles. In addition, DINP could induce apoptosis, autophagy and oxidative stress of the ovary tissue. Meanwhile, the serum estradiol concentration distinctly decreased in the 20 and 200 mg/kg DINP-treated groups, suggesting that DINP might affect the function of ovarian granulosa cells. Primary mouse ovarian granulosa cells were utilized for further investigation after the cells were treated with 0, 100, 200, 400 μM DINP for 24 h. Similar to the in vivo experiment, DINP could also induce apoptosis and autophagy of ovarian granulosa cells, as well as oxidative stress; while inhibition of oxidative stress by NAC could alleviate DINP-induced apoptosis and autophagy. Furthermore, inhibition of autophagy by 3-MA could also rescue the induction of apoptosis by DINP. Taken together, these results indicated that DINP induced apoptosis and autophagy of mouse ovarian granulosa cells via oxidative stress, and autophagy played a cytotoxic role in DINP-induced apoptosis.

Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland

Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.

Plasticizers: negative impacts on the thyroid hormone system

This review aims to understand the impacts of plasticizers on the thyroid system of animals and humans. The thyroid gland is one of the earliest endocrine glands that appear during embryogenesis. The thyroid gland synthesizes thyroid hormones (TH), triiodothyronine (T3), and thyroxine (T4) that are important in the regulation of body homeostasis. TH plays critical roles in regulating different physiological functions, including metabolism, cell growth, circadian rhythm, and nervous system development. Alteration in thyroid function can lead to different medical problems. In recent years, thyroid-related medical problems have increased and this could be due to rising environmental pollutants. Plasticizers are one such group of a pollutant that impacts thyroid function. Plasticizers are man-made chemicals used in a wide range of products, such as children's toys, food packaging items, building materials, medical devices, cosmetics, and ink. The increased use of plasticizers has resulted in their detection in the environment, animals, and humans. Studies indicated that plasticizers could alter thyroid function in both animals and humans at different levels. Several studies demonstrated a positive and/or negative correlation between plasticizers and serum T4 and T3 levels. Plasticizers could also change the expression of various TH-related genes and proteins, including thyroid-stimulating hormone (TSH), thyrotropin-releasing hormone (TRH), and transporters. Histological analyses demonstrated thyroid follicular cell hypertrophy and hyperplasia in response to several plasticizers. In conclusion, plasticizers could disrupt TH homeostasis and the mechanisms of toxicity could be diverse.

Genotoxic impact of di-n-butyl phthalate on DNA: A comparative study of three generations in the neuronal tissue of Wistar rats

Di-n-butyl phthalate (DBP), one of the plasticizers, is considered a ubiquitous environmental contaminant due to its widespread application in personal-care products and serves as a raw material in many industries for the generation of many plastic products. Several scientific investigations have shown that DBP caused embryotoxicity and cognitive impairments. However, there is less understanding of the genotoxic potential of DBP in neuronal tissue when exposure happens continuously for several generations. The present study was undertaken to investigate the impact of DBP on the nucleic acids of neuronal tissue in one-month-old rats by performing a comet assay and biochemical analyses. By oral gavage, the parental generation (F₀) was administered DBP (500 mg/kg/day) during gestation (GD6-20) and lactation, and exposures were continued for three consecutive generations until the pups were grown to one-month-old. The oxidative stress assessments carried out in discrete brain regions isolated from one-month-old rats (F₁-F₃) following DBP exposure indicated significant inhibition in the levels of antioxidant enzymes (superoxide dismutase and catalase) while oxidant status (malondialdehyde) was elevated significantly. The extent of DNA damage using the comet assay, as measured by the olive moment, tail DNA percentage and tail length, was greater in DBP-treated rats compared with the control group, but RNA/DNA content decreased significantly. The results of this study suggested a strong link between oxidative stress and genetic integrity in the neuronal tissue of rats exposed to DBP generationally. To summarise, DBP exposure during pregnancy caused oxidative stress, which resulted in genetic instability in specific discrete brain regions of the third generation.

Behavioral Effects of Exposure to Phthalates in Female Rodents: Evidence for Endocrine Disruption?

Phthalates have been widely studied for their reprotoxic effects in male rodents and in particular on testosterone production, for which reference doses were established. The female rodent brain can also represent a target for exposure to these environmental endocrine disruptors. Indeed, a large range of behaviors including reproductive behaviors, mood-related behaviors, and learning and memory are regulated by sex steroid hormones. Here we review the experimental studies addressing the effects and mechanisms of phthalate exposure on these behaviors in female rodents, paying particular attention to the experimental conditions (period of exposure, doses, estrous stage of analyses etc.). The objective of this review is to provide a clear picture of the consistent effects that can occur in female rodents and the gaps that still need to be filled in terms of effects and mode(s) of action for a better risk assessment for human health.

On the Use and Interpretation of Areola/Nipple Retention as a Biomarker for Anti-androgenic Effects in Rat Toxicity Studies

Areola/nipple retention (NR) is an established biomarker for an anti-androgenic mode of action in rat toxicity studies. It is a mandatory measurement under several OECD test guidelines and is typically assessed in combination with anogenital distance (AGD). Both NR and AGD are considered retrospective biomarkers of insufficient androgen signaling during the masculinization programming window in male fetuses. However, there are still aspects concerning NR as a biomarker for endocrine disruption that remains to be clarified. For instance, can NR be regarded a permanent adverse effect? Is it a redundant measurement if AGD is assessed in the same study? Is NR equally sensitive and specific to anti-androgenic chemical substances as a shortening of male AGD? In this review we discuss these and other aspects concerning the use of NR as a biomarker in toxicity studies. We have collected available literature from rat toxicity studies that have reported on NR and synthesized the data in order to draw a clearer picture about the sensitivity and specificity of NR as an effect biomarker for an anti-androgenic mode of action, including comparisons to AGD measurements. We carefully conclude that NR and AGD in rats for the most part display similar sensitivity and specificity, but that there are clear exceptions which support the continued assessment of both endpoints in relevant reproductive toxicity studies. Available literature also support the view that NR in infant male rats signifies a high risk for permanent nipples in adulthood. Finally, the literature suggests that the mechanisms of action leading from a chemical stressor event to either NR or short AGD in male offspring are overlapping with respect to canonical androgen signaling, yet differ with respect to other mechanisms of action.

Endocrine-disrupting chemicals and behaviour: A high risk to take?

Early life exposure to endocrine-disrupting chemicals (EDCs) is considered a potential risk factor for aberrant brain development and the emergence of behavioral deficits. The purpose of this review is to summarize the toxic effects of bisphenol-A (BPA) and phthalate exposure during pre-, -post- or perinatal life on different types of behaviour in male and female rodents. Despite results not being always consistent, most probably due to methodological issues, it is highly probable that early life exposure to BPA or/and phthalates, affects various aspects of behaviour in the offspring. Adverse effects include: Increased levels of anxiety, altered exploratory behaviour, reduced social interaction or increased aggression and deficits in spatial or recognition learning and memory. These effects have been observed with a wide range of doses, in some cases even below the currently employed Tolerable Daily Intake dose for either BPA or phthalates.

Gestational Phthalate Exposure and Preschool Attention Deficit Hyperactivity Disorder in Norway

Supplemental Digital Content is available in the text.

Prenatal phthalate exposure has been linked to altered neurobehavioral development in both animal models and epidemiologic studies, but whether or not these associations translate to increased risk of neurodevelopmental disorders is unclear. We used a nested case-cohort study design to assess whether maternal urinary concentrations of 12 phthalate metabolites at 17 weeks gestation were associated with criteria for Attention Deficit Hyperactivity Disorder (ADHD) classified among 3-year-old children in the Norwegian Mother, Father and Child Cohort Study (MoBa). Between 2007 and 2011, 260 children in this substudy were classified with ADHD using a standardized, on-site clinical assessment; they were compared with 549 population-based controls. We modeled phthalate levels both linearly and by quintiles in logistic regression models adjusted for relevant covariates and tested for interaction by child sex. Children of mothers in the highest quintile of di-iso-nonyl phthalate (∑DiNP) metabolite levels had 1.70 times the odds of being classified with ADHD compared with those in the lowest quintile (95% confidence interval [CI] = 1.03 to 2.82). In linear models, there was a trend with the sum of di-2-ethylhexyl phthalate metabolites (∑DEHP); each natural log-unit increase in concentration was associated with 1.22 times the odds of ADHD (95% CI = 0.99 to 1.52). In boys, but not girls, mono-n-butyl phthalate exposure was associated with increased odds of ADHD (odds ratio [OR] 1.42; 95% CI = 1.07 to 1.88). Additional adjustment for correlated phthalate metabolites attenuated estimates. These results suggest gestational phthalate exposure may impact the behavior of children as young as 3 years.

Morphological and transcriptomic alterations in neonatal lamb testes following developmental exposure to low-level environmental chemical mixture

Exposure to anthropogenic environmental chemical mixtures could be contributing to the decline in male reproductive health. This study used the biosolid treated pasture (BTP) sheep model to assess the effects of exposure to low-dose chemical mixtures. Maternal BTP exposure was associated with lower plasma testosterone concentrations, a greater proportion of Sertoli cell-only seminiferous tubules, and fewer gonocytes in the testes of neonatal offspring. Transcriptome analysis highlighted changes in testicular mTOR signalling, including lower expression of two mTOR complex components. Transcriptomic hierarchical analysis relative to the phenotypic severity demonstrated distinct differential responses to maternal BTP exposure during pregnancy. Transcriptome analysis between phenotypically normal and abnormal BTP lambs demonstrated separate responses within the cAMP and PI3K signalling pathways towards CREB. Together, the results provide a potential mechanistic explanation for adverse effects. Exposure could lower gonocyte numbers through mTOR mediated autophagy, but CREB mediated survival factors may act to increase germ cell survival.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

Endocrine disrupting chemicals and the mammary gland

Development of the mammary gland requires coordination of hormone signaling pathways including those mediated by estrogen, progesterone, androgen and prolactin receptors. These hormones play important roles at several distinct stages of life including embryonic/fetal development, puberty, pregnancy, lactation, and old age. This also makes the gland sensitive to perturbations from environmental agents including endocrine disrupting chemicals (EDCs). Although there is evidence from human populations of associations between EDCs and disruptions to breast development and lactation, these studies are often complicated by the timing of exposure assessments and the latency to develop breast diseases (e.g., years to decades). Rodents have been instrumental in providing insights-not only to the basic biology and endocrinology of the mammary gland, but to the effects of EDCs on this tissue at different stages of development. Studies, mostly but not exclusively, of estrogenic EDCs have shown that the mammary gland is a sensitive tissue, that exposures during perinatal development can produce abnormal mammary structures (e.g., alveolar buds, typically seen in pregnant females) in adulthood; that exposures during pregnancy can alter milk production; and that EDC exposures can enhance the response of the mammary tissue to hormones and chemical carcinogens. Other studies of persistent organic pollutants have shown that EDC exposures during critical windows of development can delay development of the gland, with lifelong consequences for the individual. Collectively, this work continues to support the conclusion that EDCs can harm the mammary gland, with effects that depend on the period of exposure and the period of evaluation.

Detrimental effects induced by diisononyl phthalate on development and behavior of Drosophila larva and potential mechanisms

Diisononyl phthalate (DINP) as one of the most commonly used phthalates, has been found in various environmental samples and is considered to have potential risks to ecosystem. Till now, DINP has no clear effect consensus on insects from development to behavior and even mechanisms. Here, Drosophila melanogaster was selected as model organisms and the toxic effects of DINP (0.1%, 0.2%, 0.5% and 1.0%) (v/v) on its metamorphosis, crawling behavior, intestinal cells and cellular redox balance were investigated. During metamorphosis process, lower hatching rate, longer development time, lighter body weight and malformation were observed at high concentration groups. The crawling ability of larvae was severely inhibited by DINP and the movement distance was drastically reduced. DINP could cause severe damage to the larval intestinal cells in the dose-dependent and time-dependent manners. DINP was found to induce redox imbalance with activities of two important antioxidant enzymes (catalase (CAT) and superoxide dismutase (SOD)) increasing, and reactive oxygen species (ROS) level fluctuation in larvae. Our findings provide theoretical basis and data support for scientific management of DINP to reduce ecological risk.

Maternal Exposure to Dibutyl Phthalate (DBP) or Diethylstilbestrol (DES) Leads to Long-Term Changes in Hypothalamic Gene Expression and Sexual Behavior

Xenobiotic exposure during pregnancy and lactation has been linked to perinatal changes in male reproductive outcomes and other endocrine parameters. This pilot study wished to assess whether brief maternal exposure of rats to xenobiotics dibutyl phthalate (DBP) or diethylstilbestrol (DES) might also cause long-term changes in hypothalamic gene expression or in reproductive behavior of the resulting offspring. Time-mated female Sprague Dawley rats were given either DBP (500 mg/kg body weight, every second day from GD14.5 to PND6), DES (125 µg/kg body weight at GD14.5 and GD16.5 only), or vehicle (n = 8–12 per group) and mild endocrine disruption was confirmed by monitoring postnatal anogenital distance. Hypothalamic RNA from male and female offspring at PND10, PND24 and PND90 was analyzed by qRT-PCR for expression of aromatase, oxytocin, vasopressin, ER-alpha, ER-beta, kisspeptin, and GnRH genes. Reproductive behavior was monitored in male and female offspring from PND60 to PND90. Particularly, DES treatment led to significant changes in hypothalamic gene expression, which for the oxytocin gene was still evident at PND90, as well as in sexual behavior. In conclusion, maternal xenobiotic exposure may not only alter endocrine systems in offspring but, by impacting on brain development at a critical time, can have long-term effects on male or female sexual behavior.

Associations of prenatal exposure to phthalates with measures of cognition in 7.5-month-old infants

BACKGROUND

Phthalates are endocrine disrupting chemicals that have been associated with adverse neurobehavior, but little is known about their influence on infant cognition.

METHODS

A visual recognition memory task was used to assess cognition in 244 7-8-month-old infants (121 females; 123 males) from a prospective cohort study. Phthalate metabolites were quantified in maternal urines pooled from across pregnancy. The task included familiarization trials (infant shown 2 identical faces) and test trials (infant shown the now familiar face paired with a novel one). Half of the infants saw one set of faces as familiar (set 1) and half saw the other set as familiar (set 2). During familiarization trials, average run duration (time looking at stimuli before looking away, measure of processing speed), and time to familiarization (time to reach 20 s looking at the stimuli, measure of attention) were assessed. During test trials, novelty preference (proportion of time looking at the novel face, measure of recognition memory) was assessed. Multivariable generalized linear models were used to assess associations of monoethyl phthalate (MEP), sum of di(2-ethylhexyl) phthalate metabolites (ΣDEHP), sum of di(isononyl) phthalate metabolites (ΣDINP), and sum of anti-androgenic phthalate metabolites (ΣAA) with each outcome.

RESULTS

Mothers were mostly white and college educated, and urine phthalate concentrations were similar to those in reproductive age women in the U.S.

POPULATION

All phthalate exposure biomarkers, except MEP, were associated with increases in average run duration. However, depending on the phthalate, associations were only in males or infants who saw the set 2 stimuli as familiar. Unexpectedly, ΣAA was associated with a shorter time to reach familiarization. Phthalate biomarkers also were associated with modest decrements in novelty preference, but these associations were nonsignificant.

CONCLUSION

Prenatal exposure to phthalates may be related to slower information processing and poorer recognition memory in infants.

Reproductive toxic potential of phthalate compounds - State of art review

Phthalates are pervasive compounds, and due to the ubiquitous usage of phthalates, humans or even children are widely exposed to them. Since phthalates are not chemically bound to the plastic matrix, they can easily leach out to contaminate the peripheral environment. Various animal and human studies have raised vital health concern including developmental and reproductive toxicity of phthalate exposure. The present review is based upon the available literature on phthalates with respect to their reproductive toxic potential. Common reproductive effects such as declined fertility, reduced testis weight, variations in accessory sex organs and several female reproductive disorders appeared to be largely associated with the transitional phthalates. Among the higher molecular weight phthalates (≥ C7), di-isononyl phthalate (DINP) produces some minor effects on development of male reproductive tract and among low molecular weight phthalates (≤C3), di-methyl (DMP) and di-isobutyl (DIBP) phthalate produce some adverse effects on male reproductive system. Whereas transitional phthalates such as di-butyl phthalate, benzyl butyl phthalate, and di-(2-ethylhexyl) phthalate have shown adverse effects on female reproductive system. Owing to these, non-toxic alternatives to phthalates may be developed and use of phthalates could be rationalized as an important issue where human reproduction system is involved. Though, more epidemiological studies are needed to substantiate the reported findings on phthalates.

Comparison of In Vitro Endocrine Activity of Phthalates and Alternative Plasticizers

Because of the deleterious effects of phthalates, regulations have been taken to decrease their use, and the needs for alternatives are increasing. Due to the concerns about the endocrine-disrupting properties of phthalates, it was deemed necessary to particularly investigate these effects for potential substitutes. In this study, we compared the in vitro endocrine activity of several already used potential alternative plasticizers (DEHT, DINCH, and TOTM) or new substitutes (POLYSORB® isosorbide and POLYSORB® ID 46) to one of 2 phthalates, DEHP and DINP. Effects of these chemicals on 3 common mechanisms of endocrine disruption, i.e., interaction with estrogen receptors (ER), androgen receptors (AR), or steroidogenesis, were studied using extensively used in vitro methods. In the E-Screen assay, only DEHP moderately induced MCF-7 cell proliferation; none of the other tested substances were estrogenic or antiestrogenic. No androgenic or antiandrogenic activity in MDA-kb2 cells was shown for any of the tested phthalates or alternatives. On the other hand, both DEHP and DINP, as well as DEHT, DINCH, and TOTM, disrupted steroidogenesis in the H295R assay, mainly by inducing an increase in estradiol synthesis; no such effect was observed for POLYSORB® isosorbide and POLYSORB® ID 46.

Effects of Di-Isononyl Phthalate (DiNP) on Follicular Atresia in Zebrafish Ovary

Di-isononyl phthalate (DiNP) is a plasticizer reported to elicit hormone-like activity and disrupt metabolism and reproduction in fish and other vertebrates. In general, phthalates have been used at high concentrations beyond reported environmental levels to assess their adverse effects on fish gonadal physiology. The present study exposed adult female zebrafish to a wide range of DiNP concentrations [0.42 µg L^-1 (10^-9 M), 4.2 µg L^-1 (10^-8 M), and 42 µg L^-1 (10^-7 M)] for 21 days. We evaluated gene expression profiles related to apoptosis, autophagy, and oxidative stress; DNA fragmentation (TUNEL assay: terminal deoxynucleotidyl transferase dUTP nick end labeling) and caspase activity (CAS3) were also examined. Exposure to 0.42 and 4.2 µg L^-1 upregulated the genes coding for tnfa and baxa, sod1, prkaa1, respectively. CAS3 immunohistochemistry revealed a higher number of positive vitellogenic oocytes in ovaries exposed to 0.42 µg L^-1. Subsequently, we examined the relationship between CAS3 signaling and DNA fragmentation. Accordingly, DNA fragmentation was observed in vitellogenic follicles of fish exposed to 0.42 and 4.2 μg L^-1. Our results demonstrate that follicular atresia can occur after exposure to environmental levels of DiNP for 21 days, which may adversely affect the reproductive performance of female zebrafish in a non-monotonic manner.

Evaluation of a panel of spermatological methods for assessing reprotoxic compounds in multilayer semen plastic bags

The increase of fertility performance in sows is one of the biggest achievements in pig production over the last 30 years. Nevertheless, pig farms using artificial insemination (AI) repeatedly experienced in recent year’s fertility problems with dramatic consequences due to toxic compounds from plastic semen bags. In particular, bisphenol A diglycidyl-ether (BADGE) present in multilayer plastic bags can leach into the semen and could affect the functionality of the spermatozoa. Former studies could not find any alterations in spermatozoa based on the exposure to BADGE. The aim of the study was to evaluate effects of BADGE on boar spermatozoa using an extended panel of spermatological methods. In spring 2019, a large drop in farrowing rates from 92.6 ± 2.3% to 63.7 ± 11.1% in four sow farms in Croatia was detected. In migration studies, BADGE could be identified as a causal toxic compound and leached into the extended semen in concentration of 0.37 ± 0.05 mg/L. Detailed spermatological studies showed that significant predictors for effects on spermatozoa were different levels of motility and kinematic data after a prolonged storage time, thermo-resistance test (prolonged incubation time), mitochondrial activity, membrane integrity and fluidity. No serious effects were observed for sperm morphology and DNA fragmentation. These results provide new insights into the development of a new quality assurance concept for a detailed spermatological examination during testing of plastic materials for boar semen preservation. It could be shown that boar spermatozoa are an excellent biosensor to detect potential toxicity and fertility-relevant compounds.

Is there an optimal sampling time and number of samples for assessing exposure to fast elimination endocrine disruptors with urinary biomarkers?

In studies investigating the effects of endocrine disruptors (ED) such as phthalates, bisphenols and some pesticides on human health, exposure is usually characterized with urinary metabolites. The variability of biomarkers concentration, due to rapid elimination from the body combined with frequent exposure is however pointed out as a major limitation to exposure assessment. This study was conducted to assess variability of urinary metabolites of ED, and to investigate how sampling time and number of samples analyzed impacts exposure assessment. Urine samples were collected over 6 months from 16 volunteers according to a random sampling design, and analyzed for 16 phthalate metabolites, 9 pesticide metabolites and 4 bisphenols. The amount of biomarkers excreted in urine at different times of the day were compared. In parallel, 2 algorithms were developed to investigate the effect of the number of urine samples analyzed per subject on exposure assessment reliability. In the 805 urine samples collected from the participants, all the biomarkers tested were detected, and 18 were present in >90% of the samples. Biomarkers variability was highlighted by the low intraclass correlation coefficients (ICC) ranging from 0.09 to 0.51. Comparing the amount of biomarkers excreted in urine at different time did not allow to identify a preferred moment for urine collection between first day urine, morning, afternoon and evening. Algorithms demonstrated that between 10 (for monobenzyl (MBzP) phthalate) and 31 (for bisphenol S) samples were necessary to correctly classify 87.5% of the subjects into quartiles according to their level of exposure. The results illustrate the high variability of urinary biomarkers of ED over time and the impossibility to reliably classify subjects based on a single urine sample (or a limited number). Results showed that classifying individuals based on urinary biomarkers requires several samples per subject, and this number is highly different for different biomarkers.

Exposure evaluation of diisononyl phthalate in the adults of Drosophila melanogaster: Potential risks in fertility, lifespan, behavior, and modes of action

Diisononyl phthalate (DINP) as a phthalate plasticizer is widely used in daily life and production, which shows endocrine disruption effects and has several adverse effects on the normal physiological function. Here, the effects of DINP (0.1%, 0.2%, 0.5%, and 1.0%) (v/v) on the fertility, lifespan, climbing behavior, anti-starvation ability of Drosophila melanogaster and the potential modes of action were investigated. The results showed that DINP impaired fertility in a dose-dependent manner and smaller ovarian volume, lower hatching rate, and fewer offspring was observed at higher concentrations. The effect of DINP on the lifespan showed gender-specific, and mortality was increased after exposure above 0.2% DINP. The climbing ability increased at 0.1% DINP compared with the vehicle group, while it manifested a dose-dependent decrease at higher concentrations. The anti-starvation ability exhibited hormesis after short-term culture and reduced as culture time extending. By measuring the redox status (catalase (CAT) and reactive oxygen species (ROS)) of adult flies after two exposure methods, it was found that DINP induced redox instability, which may explain the above effects at the molecular level. This study provides data to support a comprehensive analysis of DINP potential toxicity and to guide its rational use and management better.

Subacute exposure to di-isononyl phthalate alters the morphology, endocrine function, and immune system in the colon of adult female mice

Di-isononyl phthalate (DiNP), a common plasticizer used in polyvinyl chloride products, exhibits endocrine-disrupting capabilities. It is also toxic to the brain, reproductive system, liver, and kidney. However, little is known about how DiNP impacts the gastrointestinal tract (GIT). It is crucial to understand how DiNP exposure affects the GIT because humans are primarily exposed to DiNP through the GIT. Thus, this study tested the hypothesis that subacute exposure to DiNP dysregulates cellular, endocrine, and immunological aspects in the colon of adult female mice. To test this hypothesis, adult female mice were dosed with vehicle control or DiNP doses ranging from 0.02 to 200 mg/kg for 10–14 days. After the treatment period, mice were euthanized during diestrus, and colon tissue samples were subjected to morphological, biochemical, and hormone assays. DiNP exposure significantly increased histological damage in the colon compared to control. Exposure to DiNP also significantly decreased sICAM-1 levels, increased Tnf expression, decreased a cell cycle regulator (Ccnb1), and increased apoptotic factors (Aifm1 and Bcl2l10) in the colon compared to control. Colon-extracted lipids revealed that DiNP exposure significantly decreased estradiol levels compared to control. Collectively, these data indicate that subacute exposure to DiNP alters colon morphology and physiology in adult female mice.

Maternal phthalate exposure associated with decreased testosterone/LH ratio in male offspring during mini-puberty. Odense Child Cohort

BACKGROUND

Phthalates are plastic softeners with anti-androgenic properties. Prenatal exposure has led to lower testosterone (T) levels and smaller testicles in adult rats. To our knowledge, no studies have examined associations between prenatal phthalate exposure and sex hormone concentrations in infants.

OBJECTIVE

To study associations between phthalate exposure in Danish pregnant women and T, luteinizing hormone (LH), follicle stimulating hormone (FSH), Δ4-androstenedione (adion), 17α-hydroxyprogesterone (17-OHP) dehydroepiandrosterone sulfate (DHEAS) concentrations in their infants (N = 479) during mini-puberty.

METHODS

Concentrations of 12 phthalate metabolites from six phthalate diesters were measured in urine samples collected from 2010 to 2012 from 479 pregnant women participating in the Odense Child Cohort at gestational week 28 (range 20.4-30.4). Serum T, LH, FSH, adion, 17-OHP, DHEAS, weight and height were measured approximately three months after expected date of birth. Associations between prenatal phthalate exposure and gonadotropin and androgen metabolite concentrations were estimated in boys and girls separately in adjusted linear regression models.

RESULTS

T concentration was lower in boys prenatally exposed to phthalates. Maternal urinary concentrations of summed mono-iso-butyl and mono-n-butyl phthalate (∑MBP_i+n) and summed metabolites of di-iso-nonyl phthalate (∑DiNP_m) were associated with lower T/LH ratio in male offspring and a dose-response association was found. FSH was 14% (95% CI: 1; 25) lower among male offspring from mothers exposed to ∑DiNP_m in the highest compared to the lowest tertile. No association was found for girls.

CONCLUSION

Even in these low exposed children, we found a significant decrease in T/LH ratio during mini-puberty in boys prenatally exposed to phthalates, which may suggest impairment of Leydig cells. The children will be followed as they approach adrenarche and pubarche in order to assess if long-term adverse effects persist.

The effects of the phthalate DiNP on reproduction†

Di-isononyl phthalate (DiNP) is a high molecular weight, general purpose, plasticizer used primarily in the manufacture of polymers and consumer products. It can be metabolized rapidly and does not bioaccumulate. The primary metabolite of DiNP is monoisononyl-phthalate (MiNP) and the secondary metabolites include three oxidative derivatives of DiNP, which have been identified mainly in urine: mono-oxoisononyl phthalate (MOINP or oxo-MiNP), mono-carboxyisooctyl phthalate (MCIOP, MCOP or cx-MiNP), and mono-hydroxyisononyl phthalate (MHINP or OH-MiNP). The secondary metabolites are very sensitive biomarkers of DiNP exposure while primary metabolites are not. As the usage of DiNP worldwide increases, studies evaluating its potential reproductive toxicity are becoming more prevalent in the literature. In studies on female animals, the researchers found that the exposure to DiNP appears to induce negative effects on ovarian function and fertility in animal models. Whether or not DiNP has direct effects on the uterus is still controversial, and the effects on human reproduction require much more research. Studies on males indicate that DiNP exposure has disruptive effects on male reproduction and fertility. Occupational studies also indicate that the exposure to DiNP might induce negative effects on male reproduction, but larger cohort studies are needed to confirm this. This review presents an overview of the literature regarding the reproductive effects of exposure to DiNP.

Systematic comparison of the male reproductive tract in fetal and adult Wistar rats exposed to DBP and DINP in utero during the masculinisation programming window

This study investigates possible effects of in utero exposure of rats to a low dose (125 mg/kg bw/day) and a high dose (750 mg/kg bw/day) of Diisononyl phthalate (DINP) during the masculinisation programming window (MPW) which is embryonic days 15.5-18.5 (e15.5 - e18.5). Dibutyl phthalate (DBP) was used at a high dose level (750 mg/kg bw/day) as an established positive control substance for anti-androgenic effects on the developing male reproductive tract. We focussed on the MPW and measured a multitude of biological endpoints at various life stages and applied state of the art histopathology staining techniques to refine the characterization of potential changes to the testis, beyond what is currently available with DINP. If DINP can mediate testicular dysgenesis (TDS) disorders, this exposure window would be sufficient to induce androgen impacts and alter male reproductive tract development as shown earlier in this validated experimental model with DBP. Overall, the results of this systematic comparison provide convincing evidence on the differences between the effects occurring with DBP and DINP. In contrast to what was seen with DBP, DINP did not cause cryptorchidism or hypospadias, had no effect on anogenital distance/anogenital index (AGD/AGi) and Leydig cell aggregates on e17.5 and e21.5 did not increase. With DINP no reduction of intratesticular testosterone, no effects on sperm motility and sperm count and no effect on adult testosterone or luteinizing hormone (LH) levels were seen. Our results demonstrate that DINP does not cause the adverse reproductive effects known to occur with DBP, a well-established endocrine disruptor.

Prenatal and early childhood exposure to phthalates and childhood behavior at age 7 years

BACKGROUND

Emerging evidence suggests that phthalate exposure may be associated with behavior problems in children and that these associations may be sex specific.

METHODS

In a follow up study of 411 inner-city minority mothers and their children, mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), monoisobutyl phthalate (MiBP), monethyl phthalate (MEP) and four di-2-ethylhexyl phthalate metabolites (DEHP) were quantified in maternal urine samples collected during the third trimester and in child urine samples at ages 3 and 5 years. The Conners' Parent Rating Scale-Revised: Long Form (CPRS) and Child Behavior Checklist (CBCL) were administered to the mothers to assess children's behavior problems at 7 years of age. The analysis included children with available measures of CBCL, CPRS and phthalates measured in maternal urine. We performed both Quasi-Poisson regression and a mixture analysis using Weighted Quantile Sum(WQS) regression to assess the risk for CPRS scores and for internalizing and externalizing behaviors (from the CBCL) following intra-uterine exposure to the phthalate metabolites for boys and girls separately.

RESULTS

Among boys, increases in in anxious-shy behaviors were associated with prenatal exposure to MBzP (Mean Ratio [MR] = 1.20, 95%CI 1.05-1.36) and MiBP (Mean Ratio (MR) = 1.22, 95%CI 1.02-1.47). Among girls, increases in perfectionism were associated with MBzP (MR = 1.15, 95%CI 1.01-1.30). In both boys and girls, increases in psychosomatic problems were associated with MiBP (MR = 1.28, 95%CI 1.02-1.60), and MnBP (MR = 1.28, 95%CI 1.02-1.59), respectively. Among girls, decreased hyperactivity was associated with two DEHP metabolites, mono(2-ethyl-5-oxohexyl) phthalate (MR = 0.83, 95%CI 0.71-0.98) and mono(2-ethyl-5-hydroxyhexyl) phthalate (MR = 0.85, 95%CI 0.72-0.99). Using weighted Quantile Sum logistic regression, no associations were found between the Weighted Quantile Sum (WQS) of phthalate metabolites and CPRS scores or externalizing and internalizing behaviors. Nonetheless, when the analysis was performed separately for DEHP and non-DEHP metabolites significant associations were found between the WQS of DEHP metabolites and social problems in boys (OR = 2.15, 95%CI 1.13-4.06, p-value = 0.02) anxious-shy problems in girls (OR = 2.19, 95%CI 1.15-4.16, p = 0.02), and emotional lability problems in all children (OR = 0.61, 95%CI 0.38-0.97, p = 0.04). MEHP and MEOHP were the most highly weighted DEHP metabolites in WQS mixture. The analysis performed with CBCL scale corroborated these associations.

CONCLUSION

Concentration of non-DEHP metabolites was associated with anxious-shy behaviors among boys. DEHP phthalate metabolites were associated with decreased hyperactivity and impulsivity among girls on CPRS scores. These findings lend further support to the adverse associations between prenatal phthalate exposure and childhood outcomes, and clearly suggest that such associations are sex and mixture specific.

Phthalate and Bisphenol Exposure during Pregnancy and Offspring Nonverbal IQ

BACKGROUND

Prenatal exposures to phthalates and bisphenols are associated with impaired brain development in animals. However, epidemiological studies investigating the association between prenatal phthalate or bisphenol exposure and cognition have produced mixed findings and mostly had modest sample sizes and measured the exposure during the third trimester.

OBJECTIVE

We examined the association between pregnancy maternal urinary biomarkers of phthalate or bisphenol exposure and nonverbal intelligence quotient (IQ) in children 6 years of age.

METHOD

The study sample consisted of 1,282 mother-child pairs participating in the Generation R Study, a population-based birth cohort in Rotterdam, Netherlands (enrollment 2002-2006). We measured maternal urinary concentrations of 18 phthalate metabolites and 8 bisphenols at < 18 , 18-25, and > 25  wks of gestation. Child nonverbal IQ was measured at 6 years of age using the Snijders-Oomen Nonverbal Intelligence Test-Revised. Linear regression models were fit for each of the three collection phases separately, the three collection phases jointly, and for the averaged prenatal exposure across pregnancy.

RESULTS

Higher urinary concentrations of phthalate metabolites during early pregnancy were associated with lower child nonverbal IQ score [e.g., B per 10-fold increase in summed low-molecular weight phthalates = - 1.7 (95% CI: - 3.1 , - 0.3 )]. This association remained unchanged when adjusted for mid and late pregnancy exposures. We also observed an inverse association between late pregnancy di-n-octyl phthalate (DNOP) exposure and nonverbal IQ. Maternal urinary concentrations of bisphenols were not associated with child nonverbal IQ. There was no effect estimate modification by sex.

CONCLUSIONS

We did not observe that maternal biomarkers of bisphenol exposure are associated with nonverbal IQ. We found that phthalate exposure in early pregnancy and DNOP exposure in late pregnancy are associated with lower nonverbal IQ scores in children. Our results might suggest that particularly early pregnancy is a sensitive window of phthalate exposure, but future studies are needed to replicate our findings. https://doi.org/10.1289/EHP6047.

Grouping of phthalates for risk characterization of human exposures

The European Food Safety Authority (EFSA) has developed a group tolerable daily intake (TDI) for low molecular weight phthalates (LWP) including diisononyl phthalate (DINP). The LWP covered by the group TDI induce clear adverse effects on rat testicular development and pronounced reductions in fetal testicular testosterone. In contrast, DINP has a very low potency regarding changes in testicular testosterone in fetal rodents and does not induce adverse effects on reproductive endpoints. The most sensitive toxicity endpoint for DINP is liver toxicity. Due to the much lower potency of DINP for effects on testosterone, absence of reproductive toxicity, and its noted liver toxicity as compared to the LWP in the group, DINP should not be included in the group TDI.

Subchronic Exposure to Di(2-ethylhexyl) Phthalate and Diisononyl Phthalate During Adulthood Has Immediate and Long-Term Reproductive Consequences in Female Mice

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer used in a variety of consumer products. This is concerning because DEHP is an endocrine disruptor and ovarian toxicant. Diisononyl phthalate (DiNP) is a DEHP replacement that is a rising human toxicant due to its increased use as a DEHP substitute. However, little is known about the effects of DEHP or DiNP exposure during adulthood on female reproduction. Thus, this study tested the hypothesis that DEHP or DiNP exposure during adulthood has long-term consequences for female reproduction in mice. Adult female CD-1 mice (39-40 days) were orally dosed with vehicle control (corn oil), DEHP (20 µg/kg/day-200 mg/kg/day), or DiNP (20 µg/kg/day-200 mg/kg/day) for 10 days. Females were paired with untreated male mice for breeding trials immediately post-dosing and again at 3 and 9 months post-dosing. Immediately post-dosing, DEHP and DiNP did not affect fertility. At 3 months post-dosing, DiNP (20 and 100 µg/kg/day and 200 mg/kg/day) significantly disrupted estrous cyclicity, and DiNP and DEHP (20 µg/kg/day) significantly reduced the ability of females to get pregnant. At 9 months post-dosing, DiNP significantly disrupted estrous cyclicity (100 µg/kg/day), reduced time to mating (100 µg/kg/day-200 mg/kg/day), and borderline reduced percent of females who produced offspring (20 mg/kg/day). At 9 months post-dosing, DEHP (200 µg/kg/day and 200 mg/kg/day) and DiNP (100 µg/kg/day and 20 and 200 mg/kg/day) increased numbers of male-biased litters. These data show that DEHP and DiNP exposure has long-term consequences for female reproduction, even long after cessation of exposure.

Exposure to di(2-ethylhexyl) phthalate and diisononyl phthalate during adulthood disrupts hormones and ovarian folliculogenesis throughout the prime reproductive life of the mouse

Di(2-ethylhexyl) phthalate (DEHP) is a phthalate commonly used for its plasticizing capabilities. Because of the wide production and use of DEHP, humans are exposed to DEHP on a daily basis. Diisononyl phthalate (DiNP) is often used as a DEHP replacement chemical, and because of the increased use of DiNP, humans are increasingly exposed to DiNP over time. Of concern is that DEHP and DiNP both exhibit endocrine disrupting capabilities, and little is known about how short-term exposure to either of these phthalates affects aspects of female reproduction. Thus, this study tested the hypothesis that short-term exposure to DEHP or DiNP during adulthood has long-lasting consequences on ovarian follicles and hormones in female mice. Female CD-1 mice aged 39-40 days were orally dosed with either vehicle control (corn oil), DEHP (20 μg/kg/day-200 mg/kg/day), or DiNP (20 μg/kg/day-200 mg/kg/day) for 10 days. Ovarian follicle populations, estradiol, testosterone, progesterone, follicle stimulating hormone (FSH), and inhibin B were analyzed at time points immediately post-dosing and 3, 6, and 9 months post-dosing. The results indicate that 10 days of exposure to DEHP and DiNP changed the distribution of ovarian follicle populations and sex steroid hormones at multiple time points, including the last time point, 9 months post-dosing. Further, FSH was increased at multiple doses up to 6 months post-dosing. Inhibin B was not affected by treatment. These data show that short-term exposure to either DEHP or DiNP has long-term consequences that persist long after cessation of exposure.

Phthalate esters in atmospheric PM2.5 and PM10 in the semi-arid city of Xi'an, Northwest China: Pollution characteristics, sources, health risks, and relationships with meteorological factors

PM_2.5 and PM₁₀ samples were collected in the semi-arid city of Xi'an in Northwest China from November 2016 to November 2017 and analyzed to assess pollution characteristics, sources, health risks, and influencing factors of 6 priority phthalate esters (PAEs). The results showed that the sum of the 6 PAEs (Σ₆PAEs) was 85.5 ng m^-3 in PM_2.5 and 94.5 ng m^-3 in PM₁₀, being higher at the suburban site than the urban site and winter > spring > summer > autumn. The most abundant PAE was bis(2-ethylhexyl phthalate) (DEHP). PM_2.5- and PM₁₀-bound PAEs were associated mainly with the use of plasticizers plus the uses of cosmetics and personal care products, construction materials, and home furnishings. Temperature, relative humidity, and visibility had stronger influences on the concentrations of PM and PM-bound PAEs than pressure and wind speed. Pressure and relative humidity were positively correlated with the concentrations of PM and most of the PM-bound PAEs, while temperature, visibility and wind speed had negative correlations with the concentrations of PM and PM-bound PAEs. The non-carcinogenic risks of human inhalation exposure to PM-bound PAEs were in the range of 10^-7 to 10^-3, suggesting low non-cancer risks, which were higher at the suburban site than the urban site and higher to children than adults. The cancer risks of human inhalation exposure to PM-bound DEHP and butyl benzyl phthalate (BBP) were in the range of 10^-12 to 10^-10, suggesting low carcinogenic risks, being in the order of the suburban site > the urban site and DEHP > BBP. Special attention should be paid to long-term low dose exposure to PAEs in the suburb, especially in winter and spring.

Oxidative damage in the liver and kidney induced by dermal exposure to diisononyl phthalate in Balb/c mice

As a general alternative, diisononyl phthalate (DINP) has gradually replaced di(2-ethylhexyl) phthalate (DEHP) as the main plasticizer used in polyvinyl chloride. Like DEHP, DINP can also be released into the environment, resulting in humans being exposed through skin contact. This study aims to explore whether oxidative damage to hepatic and renal tissues can be induced by dermal exposure to DINP in mice. Forty-two male Balb/c mice were divided into six groups. The five DINP dermal exposure groups were exposed to different doses of DINP (0.02, 0.2, 2, 20, and 200 mg/kg) for 28 consecutive days. The pathological alterations to the skin, liver, and kidney in the mice were examined. Levels of reactive oxygen species (ROS), reduced glutathione (GSH), malondialdehyde (MDA), and DNA-protein cross-links (DPC) in the liver and kidney were also determined to investigate oxidative damage. The experimental results showed that the levels of ROS, MDA, and DPC coefficients increased gradually in a dose-dependent manner, whereas the level of GSH decreased accordingly. When the exposure dose was ≥20 mg/kg, ROS, GSH, MDA content, and the DPC coefficient were significantly different compared to the control group ( p < 0.05). These results suggest that a high dose of DINP can induce oxidative stress and histopathological alterations in the liver and kidney via dermal exposure.

Decrease in serum testosterone levels after short-term occupational exposure to diisononyl phthalate in male workers

Objective

The objective of the study was to examine the effects of occupational exposure to diisononyl phthalate (DINP) on serum testosterone levels in male workers.

Methods

From 2015 to 2018, 97 male workers were recruited from six French factories in the plastics industry. In a short longitudinal study, changes over 3 days in the level of total or free serum testosterone and DINP exposure were measured. DINP exposure was measured by urinary biomonitoring: mono-4-methyl-7-oxo-octyl phthalate (OXO-MINP), mono-4-methyl-7-hydroxy-octyl phthalate (OH-MINP) and mono-4-methyl-7-carboxyheptylphthalate (CX-MINP). We further analysed changes in follicle-stimulating hormone, luteinising hormone, total testosterone to oestradiol ratio and two bone turnover markers (procollagen-type-I-N propeptide, C terminal cross-linking telopeptide of type I collagen), and erectile dysfunction via standardised questionnaires (International Index of Erectile Function, Androgen Deficiency in Aging Males). Linear mixed models were used with the variables ‘age’ and ‘abdominal diameter’ included as confounder.

Results

Increased urinary OXO-MINP was associated with a significant decrease in total serum testosterone concentrations, but only for workers who exhibited the smallest variations and lowest exposures (p=0.002). The same pattern was observed for CX-MINP but was not significant; no association with OH-MINP was detectable. More self-reported erectile problems were found in workers exposed directly to DINP at the workstation (p=0.01). No changes were observed for the other biological parameters.

Conclusions

Short-term exposure to DINP is associated with a decrease in total serum testosterone levels in male workers. Our results suggest that DINP could present weak antiandrogenic properties in humans, but these need to be confirmed by other studies.

Review of the Effects of Perinatal Exposure to Endocrine-Disrupting Chemicals in Animals and Humans

Maternal exposure to endocrine-disrupting chemicals (EDCs) is associated with long-term hormone-dependent effects that are sometimes not revealed until maturity, middle age, or adulthood. The aim of this study was to conduct descriptive reviews on animal experimental and human epidemiological evidence of the adverse health effects of in utero and lactational exposure to selected EDCs on the first generation and subsequent generation of the exposed offspring. PubMed, Web of Science, and Toxline databases were searched for relevant human and experimental animal studies on 29 October 29 2018. Search results were screened for relevance, and studies that met the inclusion criteria were evaluated and qualitative data extracted for analysis. The search yielded 73 relevant human and 113 animal studies. Results from studies show that in utero and lactational exposure to EDCs is associated with impairment of reproductive, immunologic, metabolic, neurobehavioral, and growth physiology of the exposed offspring up to the fourth generation without additional exposure. Little convergence is seen between animal experiments and human studies in terms of the reported adverse health effects which might be associated with methodologic challenges across the studies. Based on the available animal and human evidence, in utero and lactational exposure to EDCs is detrimental to the offspring. However, more human studies are necessary to clarify the toxicological and pathophysiological mechanisms underlying these effects.