Association of phthalate exposure with thyroid function during pregnancy

Association of exposure to a mixture of phenols, parabens, and phthalates with altered serum thyroid hormone levels and the roles of iodine status and thyroid autoantibody status: A study among American adults

BACKGROUND

Toxicological and epidemiological studies have shown that environmental endocrine disruptors interfere with hormonal homeostasis. However, there is limited research on the effects of mixed exposure to nonpersistent endocrine disruptors on thyroid hormones and the factors (e.g., presence status of thyroid autoantibodies or nutritional status of organismal iodine) that may influence this association.

METHODS

Data were collected from the National Health and Nutrition Examination Survey (NHANES) 2007-2008 and 2011-2012. Relationships between single pollutants and thyroid hormone and thyroid autoantibody levels were assessed using generalized linear (GLM) and restricted cubic spline (RCS) regression models. Weighted quantile sum regression (WQS), group-weighted quantile sum regression (GWQS), quantile-based g-computation (qgcomp), and adaptive elasticity network (AENET) were applied to assess the mixed exposure effect. Next, subgroup analyses were performed on the basis of the urinary iodine concentration or thyroid autoantibody status to assess the modifying role of urinary iodine and thyroid autoantibodies.

RESULTS

A total of 2385 study participants were included in this study. Both the single-pollutant model and the multipollutant mixed model revealed that parabens and bis(2-ethylhexyl) phthalate (DEHP) metabolites were significantly and negatively associated with serum thyroxine (T4) levels. However, no associations were found between the target pollutants and thyroid autoantibodies (thyroglobulin antibodies (TgAb) and thyroid peroxidase antibodies (TPOAb)). In addition, this study revealed that urinary iodine or thyroid autoantibody status altered the associations of some of the target pollutants with thyroid hormones. WQS and qgcomp analyses, revealed that the associations of mixed pollutants with hormones differed depending on the urinary iodine or antibody status, especially T4 and thyroid-stimulating hormone (TSH).

CONCLUSION

Significant associations were found between phenols, parabens, and phthalates and serum thyroid hormone levels, with parabens and DEHP metabolites playing major roles. Urinary iodine and thyroid autoantibody status act as modifiers between environmental endocrine-disrupting pollutants and thyroid hormones.

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 exposure during pregnancy and its association with thyroid hormones: A prospective cohort study

Phthalate esters (PAEs) possess endocrine-disrupting properties. Studies in humans have indicated that in utero phthalate exposure affects maternal thyroid hormones, which are essential for fetal growth and development. However, these studies also reported inconsistent results on the relationship between phthalates and thyroid hormones. This prospective cohort study aimed to assess phthalate exposure across the three trimesters of pregnancy and its association with thyroid hormone levels. From 2019 to 2022, we recruited 672 pregnant women, and two urine samples and one blood sample were collected from each participant during the pregnancy. We examined the urine samples from 663, 335, and 294 women in the first, second, and third trimester, respectively, for the following seven phthalate metabolites: monoethyl phthalate (MEP) from diethyl phthalate (DEP); mono-n-butyl phthalate (MnBP) and mono-iso-butyl phthalate (MiBP) from dibutyl phthalate (DBP); monobenzyl phthalate (MBzP) from butyl benzyl phthalate; and three di(2-ethylhexyl) phthalate (DEHP) metabolites, mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP). Additionally, we examined the levels of free thyroxine (FT4), thyroid-stimulating hormone (TSH), and total triiodothyronine (TT3) in the serum samples of the following participants: 596, 627, and 576 in the first trimester; 292, 293, and 282 in the second trimester; and 250, 250, and 248 in the third trimester, respectively. Other than MBzP, which was detected in 25%-33% of the samples, other metabolites were detectable in >86% of urine samples, indicating widespread exposure to DEP, DBP, and DEHP. The detected phthalate exposure levels in our cohort were significantly higher than those reported in other countries. Metabolite levels varied across the trimesters, implying changes in exposure and metabolism throughout pregnancy. The observed variability in urinary concentrations of phthalate metabolites, which ranged from poor to moderate, underscores the importance of taking multiple measurements during pregnancy for precise exposure assessment. Using a linear mixed model, we analyzed the effects of repeated phthalate exposure on thyroid hormone levels while adjusting for potential confounders. We observed significant linear trends in FT4, TSH, and, to a lesser extent, TT3 across quartiles of specific phthalate metabolites. Comparing the highest to the lowest quartiles, we found a significant increase in FT4 levels, ranging from 2 to 3.7%, associated with MEP; MECPP; MEHHP; and the sum of seven metabolites (∑7PAE), three DEHP metabolites (∑3DEHP), two DBP metabolites (∑DBP), and both low molecular weight (∑LMW) and high molecular weight metabolites. Increased TSH levels (5%-16%) were observed for all phthalate metabolites (except MEHHP) and their molar sums, including ∑7PAE. For TT3, a significant increase was observed with MEP (2.2%) and a decrease was observed with ∑DBP (-2.7%). A higher TSH/FT4 ratio was observed with the highest quartiles (third or fourth) of several phthalate metabolites: MEP (8.8%), MiBP (8.7%), MnBP (22.2%), ∑7PAE (15.3%), ∑DBP (16.4%), and ∑LMW (18.6%). These hormonal alterations, most notably in the second and third trimesters, suggest that phthalate exposure may impact fetal growth and development by affecting maternal thyroid function.

Di-(2-ethylhexyl) phthalate promotes benign prostatic hyperplasia through KIF11-Wnt/β-catenin signaling pathway

Di-(2-ethylhexyl) phthalate (DEHP) might led to chronic and long-term effects on human organs due to its widespread use and bioaccumulation. Despite some cohorts reporting an association between DEHP exposure and BPH, its underlying mechanisms have not been investigated. Our findings indicate that exposure to DEHP or MEHP (main metabolites of DEHP in the human body) leads to increased prostate weights, elevated prostate index, and notable epithelial thickening in rats. It has been observed to promote BPH-1 cell proliferation with effects ranging from low to high concentrations. Transcriptome sequencing analysis of rat prostate tissues identified KIF11 as the key hub gene. KIF11 is highly expressed after DEHP/MEHP exposure, and knocking down of KIF11 inhibits the MEHP-induced promotion of cell proliferation. Exposure to MEHP has been observed to increase the expression of p-GSK-3β and elevate the levels of β-catenin, thereby activating the Wnt/β-catenin signaling pathway. Knocking down of KIF11 significantly inhibits these effects. Histone H3 at Lysine 27 acetylation (H3K27ac) is implicated in the upregulation of KIF11 expression, as evidenced by the addition of the acetylation inhibitor C646. In summary, our findings established that DEHP exposure could promote BPH through H3K27ac regulated KIF11/Wnt/β-catenin signaling pathway.

Disrupted prenatal metabolism may explain the etiology of suboptimal neurodevelopment: a focus on phthalates and micronutrients and their relationship to autism spectrum disorder

Pregnancy is a time of high metabolic coordination, as maternal metabolism adapts to support the growing fetus. Many of these changes are coordinated by the placenta, a critical fetal endocrine organ and the site of maternal-fetal crosstalk. Dysregulation in maternal and placental metabolism during pregnancy has been linked to adverse outcomes, including altered neurodevelopment. Autism spectrum disorder (ASD) is a neurodevelopmental disorder linked to metabolic alterations in both children and their mothers. Prenatal environmental exposures have been linked to risk of ASD through dysregulated maternal, placental, and fetal metabolism. In this review, we focus on recent studies investigating the associations between prenatal metabolism in the maternal-placental-fetal unit and the impact of prenatal environmental exposures to phthalates and micronutrients on ASD risk. By identifying the mechanisms through which phthalates and other ubiquitous endocrine disrupting chemicals influence development, and how nutritional interventions can impact those mechanisms, we can identify promising ways to prevent suboptimal neurodevelopment.

Association of phthalate exposure with reproductive outcomes among infertile couples undergoing in vitro fertilization: A systematic review

Human fertility is impacted by changes in lifestyle and environmental deterioration. To increase human fertility, assisted reproductive technology (ART) has been extensively used around the globe. As early as 2009, the Endocrine Society released its first scientific statement on the potential adverse effects of environmental endocrine-disrupting chemicals (EDCs) on human health and disease development. Chemicals known as phthalates, frequently employed as plasticizers and additives, are common EDCs. Numerous studies have shown that phthalate metabolites in vivo exert estrogen-like or anti-androgenic effects in both humans and animals. They are associated with the progression of a range of diseases, most notably interference with the reproductive process, damage to the placenta, and the initiation of chronic diseases in adulthood. Phthalates are ingested by infertile couples in a variety of ways, including household products, diet, medical treatment, etc. Exposure to phthalates may exacerbate their infertility or poor ART outcomes, however, the available data on phthalate exposure and ART pregnancy outcomes are sparse and contradictory. Therefore, this review conducted a systematic evaluation of 16 papers related to phthalate exposure and ART pregnancy outcomes, to provide more aggregated results, and deepen our understanding of reproductive outcomes in infertile populations with phthalate exposure.

Regrettable Substitutes and the Brain: What Animal Models and Human Studies Tell Us about the Neurodevelopmental Effects of Bisphenol, Per- and Polyfluoroalkyl Substances, and Phthalate Replacements

In recent decades, emerging evidence has identified endocrine and neurologic health concerns related to exposure to endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA), certain per- and polyfluoroalkyl compounds (PFASs), and phthalates. This has resulted in consumer pressure to remove these chemicals from the market, especially in food-contact materials and personal care products, driving their replacement with structurally or functionally similar substitutes. However, these "new-generation" chemicals may be just as or more harmful than their predecessors and some have not received adequate testing. This review discusses the research on early-life exposures to new-generation bisphenols, PFASs, and phthalates and their links to neurodevelopmental and behavioral alterations in zebrafish, rodents, and humans. As a whole, the evidence suggests that BPA alternatives, especially BPAF, and newer PFASs, such as GenX, can have significant effects on neurodevelopment. The need for further research, especially regarding phthalate replacements and bio-based alternatives, is briefly discussed.

Distribution, seasonal variation and ecological risk assessment of phthalates in the Yitong River, a typical urban watercourse located in Northeast China

Phthalates (PAEs) are a typical class of endocrine disruptors (EEDs). As one of the most commonly used plasticizers, they have received widespread attention due to their wide application in various countries and high detection rates in various environmental media. To be able to clarify the contamination status of PAEs pollutants in a typical northern cold-temperate urban river, 30 water samples from Yitong River in Changchun City, northern China were collected, during the 2023 dry season (March), normal season (May) and wet season (July). Using these samples, a total of 16 target PAEs are investigated. The resulting total PAEs concentrations are: dry season 408 to 1494 ng/L, wet season 491 to 1299 ng/L, and normal season 341 to 780 ng/L. The average concentration of the 16 PAEs over the three seasons is 773 ng/L. Di-2-ethylhexyl phthalate (DEHP) and Dibutyl phthalate (DBP) have the highest concentrations, ranging from 12 to 403 ng/L and 28-680 ng/L respectively. The ecological risks within the Yitong River Basin are evaluated based on the degree of PAEs contamination. DBP and DEHP pose higher risk assessment levels for algae, crustaceans and fish than the other target PAEs. The accurate determination of PAEs provided baseline data on PAEs for the management of the Yitong River, which is of great significance for the prediction of ecological risk assessment and the development of corresponding control measures, supported further research on PAEs in the cold-temperate zone aquatic environments, and shed light on the seasonal variations of PAEs in the Northeast region in the future. Moreover, considering the bioaccumulation and persistence of PAEs, it is necessary to continue to pay attention to the pollution status of cold-temperate zones rivers and the changes in ecological risks in the future.

Maternal Di-(2-ethylhexyl)-Phthalate exposure during pregnancy altered energy metabolism in immature offspring and caused hyperglycemia

Di-(2-ethylhexyl)-phthalate (DEHP), as distinctive endocrine disrupting chemicals, has become a global environmental pollutant harmful to human and animal health. However, the impacts on offspring and mothers with maternal DEHP exposure are largely unknown and the mechanism remains elusive. We established DEHP-exposed maternal mice to investigate the impacts on mother and offspring and illustrate the mechanism from multiple perspectives. Pregnant mice were administered with different doses of DEHP, respectively. Metagenomic sequencing used fecal and transcriptome sequencing using placentas and livers from offspring have been performed, respectively. The results of the histopathology perspective demonstrated that DEHP exposure could disrupt the function of islets impact placentas and fetus development for maternal mice, and cause the disorder of glucose and lipid metabolism for immature offspring mice, resulting in hyperglycemia. The results of the metagenome of gut microbial communities indicated that the dysbiosis of gut microbiota in mother and offspring mice and the dominant phyla transformed through vertical transmission. Transcriptome analysis found DEHP exposure induced mutations of Ahcy and Gstp3, which can damage liver cells and affect the metabolism of the host. DEHP exposure harms pregnant mice and offspring by affecting gene expression and altering metabolism. Our results suggested that exposure of pregnant mice to DEHP during pregnancy and lactation increased the risk of metabolic disorders by altering key genes in liver and gut microbiota, and these results provided new insights into the potential long-term harms of DEHP.

DEHP induces apoptosis and autophagy of the thyroid via Rap1 signaling pathway: In vivo and in vitro study

OBJECTIVE

DEHP has thyroid toxicity and affects thyroid function. However, the mechanism is unclear.

METHODS

The offspring of SD rats were gavaged with different doses of DEHP from in utero to 8 or 12 weeks old. We observed the thyroid morphology with HE and autophagosomes with TEM. The THs levels were tested with ELISA. The apoptosis level was tested by flow cytometry. The levels of apoptosis-related genes, autophagy-related genes and Rap1 pathway genes, were measured with qRT-PCR and Western blot. We established an MEHP-treated Nthy-ori 3-1 cell model and inhibited the Rap1 to verify the mechanism.

RESULTS

DEHP could cause pathological damage and ultrastructure damage of thyroids in offspring rats. After DEHP exposure, the THs levels were altered, the apoptosis levels increased, and autophagosomes appeared. DEHP significantly affected the levels of apoptosis-related genes and autophagy-related genes. DEHP also affected the levels of Rap1 pathway, which was correlated with the levels of apoptosis and autophagy. After inhibiting Rap1 in Nthy-ori 3-1 cells, the THs levels were altered. Rap1 pathway was inhibited and the levels of apoptosis and autophagy were down-regulated.

CONCLUSION

DEHP could induce the apoptosis and autophagy of the thyroid, and Rap1 signaling pathway may play a significant role.

Fetal bisphenol and phthalate exposure and early childhood growth in a New York City birth cohort

BACKGROUND

Exposure to endocrine-disrupting chemicals such as bisphenols and phthalates during pregnancy may disrupt fetal developmental programming and influence early-life growth. We hypothesized that prenatal bisphenol and phthalate exposure was associated with alterations in adiposity through 4 years. This associations might change over time.

METHODS

Among 1091 mother-child pairs in a New York City birth cohort study, we measured maternal urinary concentrations of bisphenols and phthalates at three time points in pregnancy and child weight, height, and triceps and subscapular skinfold thickness at ages 1, 2, 3, and 4 years. We used linear mixed models to assess associations of prenatal individual and grouped bisphenols and phthalates with overall and time-point-specific adiposity outcomes from birth to 4 years.

RESULTS

We observed associations of higher maternal urinary second trimester total bisphenol and bisphenol A concentrations in pregnancy and overall child weight between birth and 4 years only (Beta 0.10 (95 % confidence interval 0.04, 0.16) and 0.07 (0.02, 0.12) standard deviation score (SDS) change in weight per natural log increase in exposure), We reported an interaction of the exposures with time, and analysis showed associations of higher pregnancy-averaged mono-(2-carboxymethyl) phthalate with higher child weight at 3 years (0.14 (0.06, 0.22)), and of higher high-molecular-weight phthalate, di-2-ethylhexyl phthalate, mono-(2-ethyl-5-carboxypentyl) phthalate, mono-(2-carboxymethyl) phthalate, and mono-(2-ethylhexyl) phthalate with higher child weight at 4 years (0.16 (0.04, 0.28), 0.15 (0.03, 0.27), 0.19 (0.07, 0.31), 0.16 (0.07, 0.24), 0.11 (0.03, 0.19)). Higher pregnancy-averaged high-molecular-weight phthalate, di-2-ethylhexyl phthalate, mono-(2-ethyl-5-carboxypentyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, and mono-2(ethyl-5-oxohexyl) phthalate concentrations were associated with higher child BMI at 4 years (0.20 (0.05, 0.35), 0.20 (0.05, 0.35), 0.22 (0.06, 0.37), 0.20 (0.05, 0.34), 0.20 (0.05, 0.34)). For skinfold thicknesses, we observed no associations.

DISCUSSION

This study contributes to the evidence suggesting associations of prenatal exposure to bisphenols and high-molecular-weight phthalates on childhood weight and BMI.

Analytical methods and biomonitoring results in hair for the assessment of exposure to endocrine-disrupting chemicals: A literature review

Endocrine-disrupting chemicals (EDC) are compounds that alter functions of the endocrine system due to their ability to mimic or antagonize endogenous hormones, or that alter their synthesis and metabolism, causing adverse health effects. Human biomonitoring (HBM) is a reliable method to assess human exposure to chemicals through measurement in human body fluids and tissues. It identifies new sources of exposure and determines their distribution, thereby enabling detection of the most exposed populations. Blood and urine are commonly used for HBM of EDC, but their interest is limited for compounds presenting short half-lives. Hair appears as an interesting alternative insofar as it provides a large exposure window. For the present study, we evaluated the relevance of hair in determining EDC exposure. With this in mind, we undertook a literature review focusing on the bioanalytical aspects and performances of methods developed to determine EDC in hair. The literature review was performed through methodical bibliographical research. Relevant articles were identified using two scientific databases: PubMed and Web of Science, with search equations built from a combination of keywords, MeSH terms and Boolean operators. The search strategy identified 2949 articles. After duplicates were removed, and following title, abstract, and full-text screenings, only 31 were included for qualitative synthesis. Hair collection was mainly performed in the back of the head and preparation involved two processes: cutting into small pieces or grounding to powder. The off-line LC-MS/MS method remains the main technique used to assess EDC through hair. Differences regarding the validation of analytical methods and interpretation of HBM results were highlighted, suggesting a need for international harmonisation to obtain reliable and comparable results. External contamination of hair was identified as a main limitation in the interpretation of results, highlighting the need to better understand EDC transfers through hair and to develop relevant hair decontamination processes.

A global review on the abundance and threats of microplastics in soils to terrestrial ecosystem and human health

Soil is the source and sink of microplastics (MPs), which is more polluted than water and air. In this paper, the pollution levels of MPs in the agriculture, roadside, urban and landfill soils were reviewed, and the influence of MPs on soil ecosystem, including soil properties, microorganisms, animals and plants, was discussed. According to the results of in vivo and in vitro experiments, the possible risks of MPs to soil ecosystem and human health were predicted. Finally, in light of the current status of MPs research, several prospects are provided for future research directions to better evaluate the ecological risk and human health risk of MPs. MPs concentrations in global agricultural soils, roadside soils, urban soils and landfill soils had a great variance in different studies and locations. The participation of MPs has an impact on all aspects of terrestrial ecosystems. For soil properties, pH value, bulk density, pore space and evapotranspiration can be changed by MPs. For microorganisms, MPs can alter the diversity and abundance of microbiome, and different MPs have different effects on bacteria and fungi differently. For plants, MPs may interfere with their biochemical and physiological conditions and produce a wide range of toxic effects, such as inhibiting plant growth, delaying or reducing seed germination, reducing biological and fruit yield, and interfering with photosynthesis. For soil animals, MPs can affect their mobility, growth rate and reproductive capacity. At present epidemiological evidences regarding MPs exposure and negative human health effects are unavailable, but in vitro and in vivo data suggest that they pose various threats to human health, including respiratory system, digestive system, urinary system, endocrine system, nervous system, and circulation system. In conclusion, the existence and danger of MPs cannot be ignored and requires a global effort.

The role of estrogen receptors (ERs)-Notch pathway in thyroid toxicity induced by Di-2-ethylhexyl phthalate (DEHP) exposure: Population data and in vitro studies

BACKGROUND

This study aimed to assess the exposure level and risk of Di-2-ethylhexyl Phthalate (DEHP) among adults in Jilin Province, China, clarify the impact of DEHP on human thyroid function, and to explore the role of estrogen receptors (ERs)-Notch signaling pathway in the effect of DEHP metabolites on thyroid hormones based on population data and in vitro experiments.

METHODS

312 adults participated in this study. Urinary DEHP metabolites were determined by high performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS). Two pharmacokinetic models were used to evaluate the estimated daily intake (EDI) and hazard quotient (HQ) of the adults. Multiple linear regression and mediating effect models were used to evaluate the target associations. In cell experiments, thyroid follicular epithelial (Nthy-ori3-1) cells were exposed to mono (2-ethylhexyl) phthalate (MEHP) for testing. The inhibitions of ERα and Notch pathway were conducted by siRNA and Notch pathway inhibitor DAPT.

RESULTS

The detection rate of five DEHP metabolites was 97.1∼100.0%. The HQ value of 0.3% of adults was higher than 1. The levels of urinary DEHP metabolites were significantly correlated with thyrotropin (TSH), thyrotropin-releasing hormone (TRH), total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3) and free thyroxine (FT4) and gene (estrogen receptor α (ERα), Notch1, Dll4) levels. The ERα-Notch pathway played a mediating role in the association between DEHP metabolite levels and FT4. The cell results showed, the levels of FT3 and FT4 in cell supernatant decreased after MEHP exposure, and the downward trend was reversed after ERα and notch pathways were inhibited, notch pathway genes also decreased after ERα inhibition.

CONCLUSION

Adults in the Jilin Province of China were widely exposed to DEHP. ERs-Notch pathway played an important role in the effect of DEHP metabolites on thyroid hormones.

Single- and combined-phthalate exposures are associated with biological ageing among adults

BACKGROUND

Previous research has emphasized the effects of lifestyle and genetics on ageing. However, the association between exposure to phthalates, which are extensively used in cosmetics and personal care products, and ageing is still unclear.

METHOD

Data for 4711 subjects from the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2010 were incorporated in the present study. The acceleration of the Klemera-Doubal method-biological age (KDM-BA) and phenotypic Age (PhenoAge) were measured by the composite of 13 biomarkers. Multiple-linear and weighted-quantile sum (WQS) regression models were constructed to explore the relationships of single- and combined-phthalate exposures, as indicated by urinary phthalate metabolites, with KDM-BA and PhenoAge. A generalized additive model (GAM) was fitted to explore the potential nonlinear relationships among the above variables.

RESULTS

Except for mono-(carboxynonyl), all urinary phthalate metabolites were associated with biological ageing, with correlation coefficients ranging from 0.241 to 0.526; however, mono-ethyl presented a negative correlation. The WQS models revealed mixed effects of combined urinary phthalate metabolites on ageing, with a 0.22-year ((95 % CI) 0.09, 0.32) increase in KDM-BA acceleration and a 0.27-year ((95 % CI) 0.13, 0.37) increase in PhenoAge acceleration for each decile increase in urinary phthalate metabolites. Moreover, MCPP, MEOHP, and MBzP seemed to be the top three phthalates in terms of biological ageing, with weights of 33.3 % and 32.2 %, 29.2 % and 17.2 %, and 21.5 % and 30.1 % in KDM-BA and PhenoAge acceleration, respectively.

CONCLUSION

Single-phthalate exposure was mostly associated with the ageing process, and combined-phthalate exposure presented mixed effects on biological ageing, emphasizing phthalate exposure as a significant risk factor for ageing.

Sex-specific association of exposure to a mixture of phenols, parabens, and phthalates with thyroid hormone and antibody levels in US adolescents and adults

Individuals are exposed to multiple phenols, parabens, and phthalates simultaneously since they are important endocrine-disrupting compounds (EDCs) and share common exposure pathways. It is necessary to assess the effects of the co-exposure of these EDCs on thyroid hormones (THs). In this study, data included 704 adolescents and 2911 adults from the 2007-2012 National Health and Nutrition Examination Survey (NHANES). Serum THs measured total triiodothyronine (T3), total thyroxine (T4), free forms of T3 (FT3) and T4 (FT4), thyroid-stimulating hormone (TSH), thyroglobulin (Tg), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb). And 16 EDCs (3 phenols, 2 parabens, and 11 phthalates) were measured from urine. The relationship between single EDCs and single THs was analyzed using generalized linear regression. And results showed that several EDCs were positively associated with serum T3 and FT3 levels in boys but negatively associated with serum T4 and FT4 levels in girls. And in adults, five EDCs were negatively associated with T3, T4, or FT4. The effects of co-exposure to 16 EDCs on THs were calculated using Bayesian kernel machine regression and quantile-based g-computational modeling, confirmed that co-exposure was related to the increase of T3 in adolescents and the decrease of T4 in both adolescents and adults. Besides, nonlinear and linear relationships were identified between co-exposure and the risk of positive TPOAb and TgAb in girls and adult females, respectively. In conclusion, phenols, parabens, and phthalates as a mixture might interfere the concentrations of THs and thyroid autoantibodies, and the interfering effect varies significantly by sex as well as by age. Further prospective research is warranted to investigate the causal effects and underlying mechanisms of co-exposure on thyroid dysfunction.

Association of exposure to perfluoroalkyl substances (PFAS) and phthalates with thyroid hormones in adolescents from HBM4EU aligned studies

BACKGROUND

Perfluoroalkyl substances (PFAS) and phthalates are synthetic chemicals widely used in various types of consumer products. There is epidemiological and experimental evidence that PFAS and phthalates may alter thyroid hormone levels; however, studies in children and adolescents are limited.

AIM

To investigate the association of exposure to PFAS and phthalate with serum levels of thyroid hormones in European adolescents.

METHODS

A cross-sectional study was conducted in 406 female and 327 male adolescents (14-17 years) from Belgium, Slovakia, and Spain participating in the Aligned Studies of the HBM4EU Project (FLEHS IV, PCB cohort, and BEA, respectively). Concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), free thyroxine (FT4), free triiodothyronine (FT3), and thyroid-stimulating hormone (TSH) were measured in sera from study participants, and urinary metabolites of six phthalates (DEP, DiBP, DnBP, BBzP, DEHP, and DiNP) and the non-phthalate plasticizer DINCH® were quantified in spot urine samples. Associations were assessed with linear regression and g-computational models for mixtures. Effect modification by sex was examined.

RESULTS

In females, serum PFOA and the PFAS mixture concentrations were associated with lower FT4 and higher FT3 levels; MEP and the sums of DEHP, DiNP, and DINCH® metabolites (∑DEHP, ∑DiNP, and ∑DINCH) were associated with higher FT4; ∑DEHP with lower FT3; and the phthalate/DINCH® metabolite mixture with higher FT4 and lower FT3. In males, PFOA was associated with lower FT4 and the PFAS mixture with higher TSH levels and lower FT4/TSH ratio; MEP and ∑DiNP were associated with higher FT4; and MBzP, ∑DEHP, and the phthalate/DINCH® metabolite mixture with lower TSH and higher FT4/TSH. PFOA, mono-(2-ethyl-5-hydroxyhexyl) phthalate (OH-MEHP), mono-(2-ethyl-5-oxohexyl) phthalate (oxo-MEHP), and monocarboxyoctyl phthalate (MCOP) made the greatest contribution to the mixture effect.

CONCLUSIONS

Results suggest that exposure to PFAS and phthalates is associated with sex-specific differences in thyroid hormone levels in adolescents.

The Role of Endocrine Disrupting Chemicals in Gestation and Pregnancy Outcomes

Endocrine disrupting chemicals (EDCs) are exogenous substances widely disseminated both in the environment and in daily-life products which can interfere with the regulation and function of the endocrine system. These substances have gradually entered the food chain, being frequently found in human blood and urine samples. This becomes a particularly serious issue when they reach vulnerable populations such as pregnant women, whose hormones are more unstable and vulnerable to EDCs. The proper formation and activity of the placenta, and therefore embryonic development, may get seriously affected by the presence of these chemicals, augmenting the risk of several pregnancy complications, including intrauterine growth restriction, preterm birth, preeclampsia, and gestational diabetes mellitus, among others. Additionally, some of them also exert a detrimental impact on fertility, thus hindering the reproductive process from the beginning. In several cases, EDCs even induce cross-generational effects, inherited by future generations through epigenetic mechanisms. These are the reasons why a proper understanding of the reproductive and gestational alterations derived from these substances is needed, along with efforts to establish regulations and preventive measures in order to avoid exposition (especially during this particular stage of life).

Association between urinary phthalate metabolites and chronic obstructive pulmonary disease incidence in US adults: results from NHANES 2007-2018

Despite associations between urinary phthalates and respiratory symptoms and disorders have been investigated, knowledge about their impact on COPD incidence remains limited. Using data of 8242 adults (aged 20-80 years) from the 2007-2018 National Health and Nutrition Examination Survey (NHANES), the association of mixed urinary phthalate metabolites with COPD incidence was evaluated. Among them, 789 were COPD patients, and the rest were non-COPD participants. In the single-pollutant models, a variety of phthalate metabolites were identified as independent positive factors for COPD incidence, including mono-(carboxynonyl) phthalate (MCNP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-n-butyl phthalate (MnBP), mono-(3-carboxylpropyl) phthalate (MCPP), mono-ethyl phthalate (MEP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono-benzyl phthalate (MBzP). Multi-pollutant models, including weighted quantile sum (WQS) regression, quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR) approaches consistently revealed the positive association between phthalates co-exposure and COPD incidence, and MCPP was recognized as the dominant positive driver. The positive association was more evident in the youth group and the male group. The interactions between certain phthalate metabolites in COPD were also observed. Given the limitations of the cross-sectional design of NHANES study, well-designed longitudinal studies are needed to verify or disprove these findings.

The association between urinary phthalate metabolites and serum thyroid function in US adolescents

The aim was to investigate the association between mixed exposure to phthalates and serum thyroid function among US adolescents. The study used 2007-2008 survey data from the National Health and Nutrition Examination Survey (NHANES). Data on urinary phthalates metabolites and serum thyroid function indicators were collected. The weighted multivariable linear regression models and Bayesian kernel machine regression (BKMR) analyses were used to analyze the relationship between phthalates metabolites and thyroid function. A total of 356 adolescents aged 12-19 years were included in the analysis. Linear regression models showed that mono-(carboxyisoctyl) phthalate (MCOP) was positively correlated with total triiodothyronine (TT3) (β = 0.045, 95% confidence interval [CI] 0.022, 0.068) and thyroid stimulating hormone (TSH) (β = 0.1461, 95% CI 0.059, 0.232), while mono-(carboxyisononyl) phthalate (MCNP) was negatively correlated with TSH (β = - 0.119, 95% CI - 0.196, - 0.042). BKMR analyses showed phthalate metabolites mixtures have significantly positive overall effect on TT3. Exposure to phthalate mixtures might be positively correlated with increased TT3 serum level in US adolescents. The study provided evidence for the association between mixed phthalates exposure and thyroid health in adolescent population.

Exposure to a mixture of non-persistent environmental chemicals and neonatal thyroid function in a cohort with improved exposure assessment

BACKGROUND

In vitro and toxicological studies have shown that non-persistent environmental chemicals can perturb thyroid hormone homeostasis. Epidemiological studies with improved exposure assessment (i.e., repeated urine samples) are needed to evaluate effects of these compounds, individually or as a mixture, in humans. We studied the associations between prenatal exposure to non-persistent environmental chemicals and neonatal thyroid hormones.

METHODS

The study population consisted of 442 mother-child pairs from the French SEPAGES mother-child cohort recruited between July 2014 and July 2017. For each participant, four parabens, five bisphenols, triclosan, triclocarban, benzophenone-3 as well as metabolites of phthalates and of di(isononyl)cyclohexane-1,2-dicarboxylate were assessed in two pools of repeated urine samples (median: 21 spot urines per pool), collected in the 2nd and 3rd trimesters of pregnancy, respectively. Thyroid stimulating hormone (TSH) and total thyroxine (T4) levels were determined in newborns from a heel-prick blood spot. Maternal iodine and selenium were assessed in urine and serum, respectively. Adjusted linear regression (uni-pollutant model) and Bayesian Kernel Machine Regression (BKMR, mixture model) were applied to study overall and sex-stratified associations between chemicals and hormone concentrations.

RESULTS

Interaction with child sex was detected for several compounds. Triclosan, three parabens, and one phthalate metabolite (OH-MPHP) were negatively associated with T4 among girls in the uni-pollutant model. BKMR also suggested a negative association between the mixture and T4 in girls, whereas in boys the association was positive. The mixture was not linked to TSH levels, and for this hormone the uni-pollutant model revealed associations with only a few compounds.

CONCLUSION

Our study, based on repeated urine samples to assess exposure, showed that prenatal exposure to some phenols and phthalates disturb thyroid hormone homeostasis at birth. Furthermore, both uni-pollutant and mixture models, suggested effect modification by child sex, while, to date underlying mechanisms for such sex-differences are not well understood.

Associations between exposure to phthalates and subclinical hypothyroidism in pregnant women during early pregnancy: A pilot case-control study in China

Phthalates are environmental endocrine disruptors with thyroid-disrupting properties; however, the association between phthalate exposure and subclinical hypothyroidism (SCH) during pregnancy is unknown. We recruited a study population from a cohort of pregnant women in Beijing, China, and conducted the present pilot case-control study of 42 SCH cases and 84 non-SCH controls matched with age and body mass index (BMI). Serum levels of thyroid peroxidase antibody, free thyroxine (FT₄), thyroid-stimulating hormone (TSH), and urinary levels of ten phthalate metabolites during early pregnancy were measured. Urinary monoethyl phthalate (MEP) levels in SCH cases were observably higher than those in controls (p = 0.01). Conditional logistic regression analysis revealed that mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), MEP, mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), and di-(2-ethylhexyl) phthalate (ΣDEHP) were significantly associated with a higher risk of SCH during early pregnancy (adjusted odds ratios = 1.89, 1.42, 1.81, and 1.92, respectively). Concomitantly, multiple linear regression analysis showed that MECPP, MEOHP, and ΣDEHP were positively associated with TSH and FT₄ × TSH in the entire study population. Bayesian kernel machine regression analysis and stratified analysis by BMI revealed upward tendencies in the serum levels of TSH and FT₄ × TSH. In summary, exposure to phthalates, especially DEHP, may be associated with a higher risk of SCH during early pregnancy, and a possible mechanism is the disruption of the hypothalamus-pituitary-thyroid axis.

Impact of Microplastics on the Ocular Surface

Plastics are synthetic materials made from organic polymers that are ubiquitous in daily living and are especially important in the healthcare setting. However, recent advances have revealed the pervasive nature of microplastics, which are formed by degradation of existing plastic products. Although the impact on human health has yet to be fully characterised, there is increasing evidence that microplastics can trigger inflammatory damage, microbial dysbiosis, and oxidative stress in humans. Although there are limited studies investigating their effect on the ocular surface, studies of microplastics on other organs provide some insights. The prevalence of plastic waste has also triggered public outcry, culminating in the development of legislation aimed at reducing microplastics in commercial products. We present a review outlining the possible sources of microplastics leading to ocular exposure, and analyse the possible mechanisms of ocular surface damage. Finally, we examine the utility and consequences of current legislation surrounding microplastic regulation.

Prenatal exposure to phthalates and polybrominated diphenyl ethers on neonatal health: A birth cohort study in Guangxi, China

Few epidemiological studies have focused on prenatal phthalates (PAEs) and polybrominated diphenyl ethers (PBDEs) exposure to neonatal health in China. This study aimed to assess the associations between prenatal PAEs and PBDEs exposure and neonatal health in Guangxi, a Zhuang autonomous region of China. Concentrations of 4 PAEs metabolites (mPAEs) and 5 PBDEs congeners were measured in the serum of 267 healthy pregnant women. Birth outcomes and clinical data of neonates were collected after delivery. Mono-(2-Ethylhexyl) phthalate (MEHP) (81.52%) and BDE47 (35.21%) were the mPAEs and PBDEs congeners with the highest detection rate in serum. Prenatal exposures to mono-n-butyl phthalate (MBP), MEHP, and ΣmPAEs were negatively associated with birth weight (BW), birth length (BL), and gestational age (GA). Higher exposures to MBP, MEHP, and ΣmPAEs were associated with an increased odds ratio (OR) for low birth weight (LBW), but exposure to BDE28 exhibited the opposite effect. Moreover, higher exposures to MBP, MEHP, ΣmPAEs, BDE99, and ΣPBDEswere associated with an increased OR for premature birth (PTB) (P < 0.05). In contrast to MBP exposure, BDE28 exposure was associated with a higher OR for neonatal jaundice (NNJ) (P < 0.05). The interaction analysis showed a positive interaction between monoethyl phthalate (MEP) and BDE28 on the risk of NNJ and positive interaction between ΣmPAEs and BDE47 on the risk of NNJ. In addition, there are ethnicity-specific associations of prenatal PBDEs exposure with neonatal health in individuals of Zhuang and Han nationalities, and boy neonates were more sensitive to prenatal PBDEs exposure than girl neonates. The results revealed that prenatal exposure to mPAEs and PBDEs might have adverse effects on neonatal development, and the effects might be ethnicity- and sex-specific.

Environmental exposure to perchlorate, nitrate and thiocyanate, and thyroid function in Chinese adults: A community-based cross-sectional study

BACKGROUND

Evidence on environmental exposure to perchlorate, nitrate, and thiocyanate, three thyroidal sodium iodine symporter (NIS) inhibitors, and thyroid function in the Chinese population remains limited.

OBJECTIVE

To investigate the associations of environmental exposure to perchlorate, nitrate, and thiocyanate with markers of thyroid function in Chinese adults.

METHODS

A total of 2441 non-pregnant adults (mean age 50.4 years and 39.1% male) with a median urinary iodine of 180.1 μg/L from four communities in Shenzhen were included in this cross-sectional study. Urinary perchlorate, nitrate, thiocyanate, and thyroid profiles, including serum free thyroxine (FT4), total thyroxine (TT4), free triiodothyronine (FT3), total triiodothyronine (TT3), and thyroid stimulating hormone (TSH), were measured. Generalized linear model was applied to investigate the single-analyte associations. Weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) models were used to examine the association between the co-occurrence of three anions and thyroid profile.

RESULTS

The median levels of urinary perchlorate, nitrate, and thiocyanate were 5.8 μg/g, 76.4 mg/g, and 274.1 μg/g, respectively. After adjusting for confounders, higher urinary perchlorate was associated with lower serum FT4, TT4, and TT3, and higher serum FT3 and TSH (all P < 0.05). Comparing extreme tertiles, subjects in the highest nitrate tertile had marginally elevated TT3 (β: 0.02, 95% CI: 0.00-0.04). Each 1-unit increase in log-transformed urinary thiocyanate was associated with a 0.04 (95% CI: 0.02-0.06) pmol/L decrease in serum FT3. The WQS indices were inversely associated with serum FT4, TT4, and FT3 (all P < 0.05). In the BKMR model, the mixture of three anions was inversely associated with serum FT4, TT4, and FT3.

CONCLUSIONS

Our study provides evidence that individual and combined environmental exposure to perchlorate, nitrate, and thiocyanate are associated with significant changes in thyroid function markers in the Chinese population with adequate iodine intake.

Persistent Organic Pollutant Exposure and Thyroid Function among 12-Year-Old Children

INTRODUCTION

Polychlorobiphenyls (PCBs), organochlorine pesticides (OCPs), and per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants (POPs) having numerous toxicological properties, including thyroid endocrine disruption. Our aim was to assess the impact of POPs on thyroid hormones among 12-year-old children, while taking puberty into consideration.

METHODS

Exposure to 7 PCBs, 4 OCPs, and 6 PFASs (in µg/L), and free tri-iodothyronine (fT3, pg/mL), free thyroxine (fT4, ng/dL), and thyroid-stimulating hormones (TSH, mIU/L) were assessed through blood-serum measurements at age 12 years in 249 boys and 227 girls of the PELAGIE mother-child cohort (France). Pubertal status was clinically rated using the Tanner stages. For each POP, associations were estimated using linear regression, adjusted for potential confounders.

RESULTS

Among boys, hexachlorobenzene and perfluorodecanoic acid were associated with decreased fT3 (log-scale; β [95% confidence interval] = -0.07 [-0.12,-0.02] and β = -0.03 [-0.06,-0.00], respectively). Intermediate levels of perfluorohexanesulfonic acid (PFHxS) and PCB180 were associated, respectively, with increased and decreased fT4. After stratification on pubertal status, PCBs and OCPs were associated with decreased TSH only in the more advanced Tanner stages (3-5) and with decreased fT3 among early Tanner stages (1-2). Among girls, PFHxS was associated with decreased TSH (log-scale; β = -0.15 [-0.29,-0.00]), and perfluorooctanoic acid was associated with decreased fT3 (β2nd_tercile = -0.06 [-0.10,-0.03] and β3rd_tercile = -0.04 [-0.08,-0.00], versus. 1st tercile).

DISCUSSION

This cross-sectional study highlights associations between some POPs and thyroid function disruption, which appears consistent with the literature. Considering that the associations were sex-specific and moderated by pubertal status in boys, complex endocrine interactions are likely involved.

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.

Maternal rodent exposure to di-(2-ethylhexyl) phthalate decreases muscle mass in the offspring by increasing myostatin

BACKGROUND

Di-(2-ethylhexyl) phthalate (DEHP) and its metabolites can cross the placenta and may cause birth defects and developmental disorders. However, whether maternal DEHP exposure affects skeletal muscle development in the offspring and the pathways involved are unknown. This study investigated the effects of maternal DEHP exposure and the contribution of myostatin (MSTN) to skeletal muscle development in the offspring.

METHODS

Pregnant wild-type and muscle-specific myostatin knockout (MSTN KO) C57BL/6 mice were randomized to receive vehicle (corn oil) or 250 mg/kg DEHP by gavage every other day until their pups were weaned (postnatal day 21 [PND21]). Body weights of the offspring mice were measured longitudinally, and their hindleg muscles were harvested at PD21. Also, C2C12 cells were treated with mono-2-ethylhexyl phthalate (MEHP), the primary metabolite of DEHP, and proteolysis, protein synthesis, and myogenesis markers were measured. The contribution of myostatin to maternal DEHP exposure-induced muscle wasting in the offspring was determined.

RESULTS

Maternal DEHP exposure reduced body weight growth, myofibre size, and muscle mass in the offspring compared to controls (Quad: 2.70 ± 0.1 vs. 3.38 ± 0.23, Gastroc: 2.29 ± 0.09 vs. 2.81 ± 0.14, Tibialis: 1.01 ± 0.07 vs. 1.25 ± 0.11, mg/tibial length in mm, all P < 0.01, n = 35). Maternal DEHP exposure significantly increased Myostatin expression (2.45 ± 0.41 vs. 0.03 ± 0.00 DEHP vs. controls, P < 0.01, n = 5), Atrogin-1(2.68 ± 0.65 vs. 0.63 ± 0.01, P < 0.05, n = 5), MuRF1 (1.56 ± 0.51 vs. 0.31 ± 0.01, P < 0.05, n = 5), and Smad2/3 phosphorylation (4.12 ± 0.35 vs. 0.49 ± 0.18, P < 0.05), and decreased MyoD (0.27 ± 0.01 vs. 1.52 ± 0.01, P < 0.05, n = 5), Myogenin (0.25 ± 0.03 vs. 1.95 ± 0.56, P < 0.05, n = 5), and AKT phosphorylation (4.12 ± 0.35 vs. 1.00 ± 0.06, P < 0.05, n = 5), in skeletal muscle of the offspring in MSTNflox/flox , but not in MSTN KO mice. Maternal DEHP exposure resulted in up-regulation of CCAAT/enhancer-binding protein δ (C/EBPδ, 4.12 ± 0.35 vs. 1.00 ± 0.19, P < 0.05, n = 5) in skeletal muscle of the offspring in MSTNflox/flox and MSTN KO mice (4.12 ± 0.35 vs. 4.35 ± 0.28, P > 0.05, n = 5). In vitro, C/EBPδ silencing abrogated the MEHP-induced increases in Myostatin, MuRF-1, and Atrogin-1 and decreases in MyoD and Myogenin expression.

CONCLUSIONS

Maternal DEHP exposure impairs skeletal muscle development in the offspring by enhancing the C/EBPδ-myostatin pathway in mice.

Phenol and Phthalate Effects on Thyroid Hormone Levels during Pregnancy: Relying on In Vitro Assays and Adverse Outcome Pathways to Inform an Epidemiological Analysis

BACKGROUND

Studies characterizing associations between phenols, phthalates and thyroid hormones during pregnancy produce inconsistent results. This divergence may be partly attributable to false positives due to multiple comparison testing of large numbers of chemicals, and measurement error as studies rely on small numbers of biospecimens despite high intra-individual variability in urinary chemical metabolite concentrations.

OBJECTIVES

This study employs a priori chemical filtering and expanded urinary biomonitoring to evaluate associations between phenol/phthalate exposures and serum thyroid hormones assessed during pregnancy.

METHODS

A two-tiered approach was implemented: a) In vitro high-throughput screening results from the ToxCast/Tox21 database, as informed by a thyroid Adverse Outcome Pathway network, were evaluated to select phenols/phthalates with activity on known and putative molecular initiating events in the thyroid pathway; and b) Adjusted linear regressions were used to study associations between filtered compounds and serum thyroid hormones measured in 437 pregnant women recruited in Grenoble area (France) between 2014 and 2017. Phenol/phthalate metabolites were measured in repeated spot urine sample pools (median: 21 samples/women).

RESULTS

The ToxCast/Tox21 screening reduced the chemical set from 16 to 13 and the associated number of statistical comparisons by 19%. Parabens were negatively associated with free triiodothyronine (T3) and the T3/T4 (total thyroxine) ratio. Monobenzyl phthalate was positively associated with total T4 and negatively with the T3/T4 ratio. Effect modification by iodine status was detected for several compounds (among them ΣDEHP and mono-n-butyl phthalate) that were associated with some hormones among women with normal iodine levels.

CONCLUSION

For these chemicals, screening for compounds with an increased likelihood for thyroid-related effects and relying on repeated urine samples to assess exposures improved the overall performance of multichemical analyses of thyroid disruption. This approach may improve future evaluations of human data for the thyroid pathway with implication for fetal health and may serve as a model for evaluating other toxicity outcomes. https://doi.org/10.1289/EHP10239.

Concurrent Assessment of Phthalates/HEXAMOLL® DINCH Exposure and Wechsler Intelligence Scale for Children Performance in Three European Cohorts of the HBM4EU Aligned Studies

Information about the effects of phthalates and non-phthalate substitute cyclohexane-1,2-dicarboxylic acid diisononyl ester (HEXAMOLL^® DINCH) on children's neurodevelopment is limited. The aim of the present research is to evaluate the association between phthalate/HEXAMOLL^® DINCH exposure and child neurodevelopment in three European cohorts involved in HBM4EU Aligned Studies. Participating subjects were school-aged children belonging to the Northern Adriatic cohort II (NAC-II), Italy, Odense Child Cohort (OCC), Denmark, and PCB cohort, Slovakia. In each cohort, children's neurodevelopment was assessed through the Full-Scale Intelligence Quotient score (FSIQ) of the Wechsler Intelligence Scale of Children test using three different editions. The children's urine samples, collected for one point in time concurrently with the neurodevelopmental evaluation, were analyzed for several phthalates/HEXAMOLL^® DINCH biomarkers. The relation between phthalates/HEXAMOLL^® DINCH and FSIQ was explored by applying separate multiple linear regressions in each cohort. The means and standard deviations of FSIQ were 109 ± 11 (NAC-II), 98 ± 12 (OCC), and 81 ± 15 (PCB cohort). In NAC-II, direct associations between FSIQ and DEHP's biomarkers were found: 5OH-MEHP+5oxo-MEHP (β = 2.56; 95% CI 0.58-4.55; N = 270), 5OH-MEHP+5cx-MEPP (β = 2.48; 95% CI 0.47-4.49; N = 270) and 5OH-MEHP (β = 2.58; 95% CI 0.65-4.51; N = 270). On the contrary, in the OCC the relation between DEHP's biomarkers and FSIQ tended to be inverse but imprecise (p-value ≥ 0.10). No associations were found in the PCB cohort. FSIQ was not associated with HEXAMOLL^® DINCH in any cohort. In conclusion, these results do not provide evidence of an association between concurrent phthalate/DINCHHEXAMOLLR DINCH exposure and IQ in children.

Associations between phthalate exposure and thyroid function in pregnant women during the first trimester

Phthalates are a class of environmental endocrine disruptors. Previous studies have demonstrated that phthalate exposure can affect thyroid function; however, limited studies have assessed the associations between phthalate exposure and thyroid function, especially thyroid autoimmunity in pregnant women during the first trimester. We recruited participants from a cohort of pregnant women in Beijing, China, and collected urine samples to measure ten phthalate metabolites, serum samples to measure free thyroxine (FT₄), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb) during the first trimester. We included 325 pregnant women without thyroid diseases or dysfunction in this study. Associations between phthalate metabolites and thyroid function parameters were assessed with the Bayesian kernel machine regression (BKMR) model, multiple linear regression model, and restricted cubic spline. In the BKMR model analysis, compared to the 50th percentile, total urinary phthalate metabolites levels were negatively associated with serum TPOAb levels when phthalate metabolites were at or below the 40th percentile. Stratifying by body mass index, total urinary phthalate metabolites levels were negatively associated with serum TPOAb levels in normal weight women when phthalate metabolites were at or below the 45th percentile. However, total urinary phthalate metabolites levels were positively associated with serum TPOAb levels in underweight women when phthalate metabolites were at or below the 30th percentile. In restricted cubic spline analysis, L-shaped nonlinear associations of mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), di-(2-ethylhexyl) phthalate (ΣDEHP), and inverted S-shaped nonlinear association of mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) with TPOAb were observed. In conclusion, our findings suggest that phthalate exposure may affect thyroid autoimmunity in underweight pregnant women during early pregnancy, and the potential effects of phthalate exposure on thyroid autoimmunity may be nonlinear.

Strong temperature influence and indiscernible ventilation effect on dynamics of some semivolatile organic compounds in the indoor air of an office

Many manmade organic air pollutants are semivolatile and primarily used and exposed indoors. It remains unclear how indoor environmental parameters affect indoor air dynamics of semivolatile organic compounds (SVOCs) in real-world indoor conditions, which directly relates to human exposure. By making time-resolved SVOC measurements over multiple weeks in an office, we characterized the indoor air dynamics of six representative SVOCs which were mainly present in the gas phase and of indoor origins, and investigated the effects of the temperature and ventilation rate. The six species include di-isobutyl phthalate and di-n-butyl phthalate, as well as two n-alkanes and two siloxanes. Airborne concentrations of all six SVOCs responded strongly and quickly to changes in the indoor temperature. The temperature dependence of individual species can be well fitted in the form of the van't Hoff equation, and explained 65-86% of the observed variation in the logarithm-transformed concentrations. In contrast, increasing the ventilation rate by a factor of 3-5 for hours at a constant temperature had no discernible influence on the SVOC concentrations. Further kinetic modeling analysis suggests that the observed fast temperature response and indiscernible ventilation effect are both associated with SVOC sorption onto indoor surfaces, which dramatically slows the response of SVOC concentration to changes in the ventilation rate and speeds up the response to changes in the temperature. These results highlight the importance of sorption reservoirs on regulating indoor SVOC dynamics and also have important implications for controlling and assessing indoor air exposure to SVOCs.

Multigenerational Effects of an Environmentally Relevant Phthalate Mixture on Reproductive Parameters and Ovarian miRNA Expression in Female Rats

Phthalates are endocrine-disrupting chemicals used in many consumer products. Our laboratory previously developed an environmentally relevant phthalate mixture consisting of 6 phthalates and found that it disrupted female fertility in mice. However, it was unknown if maternal exposure to the mixture affects reproductive parameters and ovarian post-transcription in the F1 and F2 generation of female rats. Thus, we tested the hypothesis that maternal exposure to the phthalate mixture affects folliculogenesis, steroidogenesis, and ovarian microRNA (miRNA) in the F1 and F2 generations of female rats. Pregnant female rats were divided into 4 groups and orally dosed daily from gestational day 10 to postnatal day 21 with corn oil (control group), 20 μg/kg/day, 200 μg/kg/day, or 200 mg/kg/day of the phthalate mixture. Maternal exposure to the phthalate mixture impaired folliculogenesis in the F1 and F2 generations of female rats and affected steroidogenesis in the F1 generation of female rats compared to control. Further, the phthalate mixture altered ovarian expression of some genes related to the cell cycle and steroidogenesis compared to control in the F1 and F2 generations of female rats. The mixture also increased ovarian expression of rno-mir-184 that is involved with the oocyte maturation process. Collectively, our data show that maternal exposure to the phthalate mixture affects folliculogenesis and steroidogenesis in the F1 and F2 generations of female rats and alters ovarian miRNA expression in the F1 generation of female rats.

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.

Insights into the Endocrine Disrupting Activity of Emerging Non-Phthalate Alternate Plasticizers against Thyroid Hormone Receptor: A Structural Perspective

Many endocrine-disrupting chemicals (EDCs) have a ubiquitous presence in our environment due to anthropogenic activity. These EDCs can disrupt hormone signaling in the human and animal body systems including the very important hypothalamic-pituitary-thyroid (HPT) axis causing adverse health effects. Thyroxine (T4) and triiodothyronine (T3) are hormones of the HPT axis which are essential for regulation of metabolism, heart rate, body temperature, growth, development, etc. In this study, potential endocrine-disrupting activity of the most common phthalate plasticizer, DEHP, and emerging non-phthalate alternate plasticizers, DINCH, ATBC, and DEHA against thyroid hormone receptor (TRα) were characterized. The structural binding characterization of indicated ligands was performed against the TRα ligand binding site employing Schrodinger’s induced fit docking (IFD) approach. The molecular simulations of interactions of the ligands against the residues lining a TRα binding pocket, including bonding interactions, binding energy, docking score, and IFD score were analyzed. In addition, the structural binding characterization of TRα native ligand, T3, was also done for comparative analysis. The results revealed that all ligands were placed stably in the TRα ligand-binding pocket. The binding energy values were highest for DINCH, followed by ATBC, and were higher than the values estimated for TRα native ligand, T3, whereas the values for DEHA and DEHP were similar and comparable to that of T3. This study suggested that all the indicated plasticizers have the potential for thyroid hormone disruption with two alternate plasticizers, DINCH and ATBC, exhibiting higher potential for thyroid dysfunction compared to DEHA and DEHP.

Identification of profiles and determinants of maternal pregnancy urinary biomarkers of phthalates and replacements in the Illinois Kids Development Study

BACKGROUND/OBJECTIVES

Pregnant women are exposed to multiple phthalates and their replacements, which are endocrine disrupting chemicals associated with adverse maternal and child health outcomes. Identifying maternal characteristics associated with phthalate/replacement exposure during pregnancy is important.

METHODS

We evaluated 13 maternal sociodemographic and lifestyle factors, enrollment year, and conception season as determinants of exposure biomarkers of phthalates and their replacements in 482 pregnant women from the Illinois Kids Development Study (I-KIDS, enrolled 2013-2018). We quantified 19 phthalate/replacement metabolites in pools of five first-morning urines collected across pregnancy. K-means clustering identified women with distinct patterns of biomarker concentrations and principal component analysis (PCA) identified principal component (PC) profiles of biomarkers that exist together. We used multivariable regression models to evaluate associations of predictors with identified k-means clusters and PCs.

RESULTS

K-means clustering identified two clusters of women: 1) low phthalate/di(2-ethylhexyl) terephthalate (∑DEHTP) and 2) high phthalate/∑DEHTP biomarker concentrations. PCA identified four PCs with loadings heaviest for biomarkers of plasticizer phthalates [di-isononyl, di-isodecyl, di-n-octyl phthalates] (PC1), of other phthalates [dibenzyl, di-n-butyl, di-iso-butyl phthalates] (PC2), of phthalate replacements [∑DEHTP, di(isononyl) cyclohexane-1,2-dicarboxylate (∑DiNCH)] (PC3), and of monoethyl phthalate [MEP] (PC4). Overall, age, marital status, income, parity, pre-pregnancy BMI, caffeine intake, enrollment year, and conception season were independently associated with k-means cluster membership and at least one PC. Additionally, race/ethnicity, education, employment, pregnancy intention, smoking status, alcohol intake, and diet were associated with at least one PC. For instance, women who conceived in the spring, summer, and/or fall months had lower odds of high phthalate/∑DEHTP cluster membership and had lower plasticizer phthalate, phthalate replacement, and MEP PC scores.

CONCLUSIONS

Conception season, enrollment year, and several sociodemographic/lifestyle factors were predictive of phthalate/replacement biomarker profiles. Future studies should corroborate these findings, with a special focus on replacements to which pregnant women are becoming increasingly exposed.

Impact of endocrine disrupting chemicals on neurodevelopment: the need for better testing strategies for endocrine disruption-induced developmental neurotoxicity

INTRODUCTION

Brain development is highly dependent on hormonal regulation. Exposure to chemicals disrupting endocrine signaling has been associated with neurodevelopmental impairment. This raises concern about exposure to the suspected thousands of endocrine disruptors, and has resulted in efforts to improve regulation of these chemicals. Yet, the causal links between endocrine disruption and developmental neurotoxicity, which would be required for regulatory action, are still largely missing.

AREAS COVERED

In this review, we illustrate the importance of two endocrine systems, thyroid hormone and retinoic acid pathways, for neurodevelopment. We place special emphasis on TH and RA synthesis, metabolism, and how endocrine disrupting chemicals known or suspected to affect these systems are associated with developmental neurotoxicity.

EXPERT OPINION

While it is clear that neurodevelopment is dependent on proper hormonal functioning, and evidence is increasing for developmental neurotoxicity induced by endocrine disrupting chemicals, this is not grasped by current chemical testing. Thus, there is an urgent need to develop test methods detecting endocrine disruption in the context of neurodevelopment. Key to this development is further mechanistic insights on the involvement of endocrine signaling in neurodevelopment as well as increased support to develop and validate new test methods for the regulatory context.

A review of the endocrine disrupting effects of micro and nano plastic and their associated chemicals in mammals

Over the years, the vaste expansion of plastic manufacturing has dramatically increased the environmental impact of microplastics [MPs] and nanoplastics [NPs], making them a threat to marine and terrestrial biota because they contain endocrine disrupting chemicals [EDCs] and other harmful compounds. MPs and NPs have deleteriouse impacts on mammalian endocrine components such as hypothalamus, pituitary, thyroid, adrenal, testes, and ovaries. MPs and NPs absorb and act as a transport medium for harmful chemicals such as bisphenols, phthalates, polybrominated diphenyl ether, polychlorinated biphenyl ether, organotin, perfluorinated compounds, dioxins, polycyclic aromatic hydrocarbons, organic contaminants, and heavy metals, which are commonly used as additives in plastic production. As the EDCs are not covalently bonded to plastics, they can easily leach into milk, water, and other liquids affecting the endocrine system of mammals upon exposure. The toxicity induced by MPs and NPs is size-dependent, as smaller particles have better absorption capacity and larger surface area, releasing more EDC and toxic chemicals. Various EDCs contained or carried by MPs and NPs share structural similarities with specific hormone receptors; hence they interfere with normal hormone receptors, altering the hormonal action of the endocrine glands. This review demonstrates size-dependent MPs' bioaccumulation, distribution, and translocation with potential hazards to the endocrine gland. We reviewed that MPs and NPs disrupt hypothalamic-pituitary axes, including the hypothalamic-pituitary-thyroid/adrenal/testicular/ovarian axis leading to oxidative stress, reproductive toxicity, neurotoxicity, cytotoxicity, developmental abnormalities, decreased sperm quality, and immunotoxicity. The direct consequences of MPs and NPs on the thyroid, testis, and ovaries are documented. Still, studies need to be carried out to identify the direct effects of MPs and NPs on the hypothalamus, pituitary, and adrenal glands.

Intrauterine exposure to di(2-ethylhexyl) phthalate (DEHP) disrupts the function of the hypothalamus-pituitary-thyroid axis of the F1 rats during adult life

INTRODUCTION

DEHP is an endocrine disruptor widely used in the production of malleable plastics. DEHP exposure was associated with altered hypothalamic-pituitary-thyroid (HPT) axis function. Although previous studies reported deleterious effects of DEHP exposure during the intrauterine period, few studies have evaluated the direct effects triggered by this endocrine disruptor on the offspring animals' thyroid function. This study aimed to investigate the impact of intrauterine exposure to DEHP on the HPT axis function programming of the offspring animals during adulthood.

METHODS

Pregnant Wistar rats were orally treated with corn oil or corn oil supplemented with DEHP (0.48 or 4.8 mg/kg/day) throughout the gestational period. The offspring rats were euthanized on the 90th postnatal day. Hypothalamus, pituitary, thyroid, and liver were collected to analyze gene expression and protein content through qPCR and Western Blot. Blood was collected to determine TSH and thyroid hormone levels through fluorometric or chemiluminescence immunoassays.

RESULTS

In the adult F1 female rats, the highest dose of DEHP decreased TSH serum levels. In the thyroid, DEHP reduced the gene expression and/or protein content of NIS, TSHR, TG, TPO, MCT8, NKX2.1, PAX8, and FOXE1. These data are consistent with the reduction in T4 serum levels of the F1 DEHP-exposed female rats. In the liver, DEHP exposure increased the mRNA expression of Dio1 and Ttr, while the highest dose of DEHP reduced the mRNA expression of Ugt1a1 and Ugt1a6. Conversely, in the F1 male adult rats, TSHB expression and TSH serum levels were increased in DEHP-exposed animals. In the thyroid, except for the reduced protein content of TSHR, none of the evaluated genes/proteins were altered by DEHP. TH serum levels were not changed in the DEHP-exposed F1 male rats compared to the control group. Additionally, there were no significant alterations in the expression of hepatic enzymes in these animals.

DISCUSSION/CONCLUSIONS

Our results demonstrated, for the first time, that intrauterine exposure to DEHP disrupts the HPT axis function in male and female offspring rats and strongly suggest that DEHP exposure increases the susceptibility of the offspring animals to develop thyroid dysfunctions during adulthood.

Structural binding perspectives of common plasticizers and a flame retardant, BDE-153, against thyroxine-binding globulin: potential for endocrine disruption

The human exposure to diverse endocrine-disrupting chemicals (EDCs) has increased dramatically over several decades with very adverse health effects. Plasticizers and flame retardants constitute important classes of EDCs interfering in endocrine physiology including the thyroid function. Thyroxine (T4) is an important hormone regulating metabolism and playing key roles in developmental processes. In this study, six phthalate and nonphthalate plasticizers and one flame retardant (BDE-153) were subjected to structural binding against thyroxine-binding globulin (TBG). The aim was to understand their potential role in thyroid dysfunction using structural binding approach. The structural study was performed using Schrodinger's induced fit docking, followed by binding energy estimations of ligands and the molecular interaction analysis between the ligands and the amino acid residues in the TBG ligand-binding pocket. The results indicated that all the compounds packed tightly into the TBG ligand-binding pocket with similar binding pattern to that of TBG native ligand, T4. A high majority of TBG interacting amino acid residues for ligands showed commonality with native ligand, T4. The estimated binding energy values were highest for BDE-153 followed by nonphthalate plasticizer, DINCH, with values comparable with native ligand, T4. The estimated binding energy values of other plasticizers DEHP, DEHT, DEHA, ATBC, and TOTM were less than DINCH. In conclusion, the tight docking conformations, amino acid interactions, and binding energy values of the most of the indicated ligands were comparable with TBG native ligand, T4, suggesting their potential for thyroid dysfunction. The results revealed highest potential thyroid disruptive action for BDE-153 and DINCH.