Plasma levels of persistent organohalogens and hormone levels in adult male humans

Dichlorodiphenyltrichloroethane for Malaria and Agricultural Uses and Its Impacts on Human Health

Pesticides are widely used in agriculture and disease control, and dichlorodiphenyltrichloroethane (DDT) is one of the most used pesticides in human history. Besides its significant contributions in pest control in agriculture, DDT was credited as having saved millions of human lives for controlling malaria and other deadly insect-transmitted diseases. Even today, the use of DDT in some countries for malaria control cannot be replaced without endangering people who live there. The recent COVID-19 pandemic has changed our lives and reminded us of the challenges in dealing with infectious diseases, especially deadly ones including malaria. However, DDT and its metabolites are stable, persist long, are found in almost every corner of the world, and their persistent effects on humans, animals, and the environment must be seriously considered. This review will focus on the history of DDT use for agriculture and malaria control, the pathways for the spread of DDT, benefits and risks of DDT use, DDT exposure to animals, humans, and the environment, and the associated human health risks. These knowledge and findings of DDT will benefit the selection and management of pesticides worldwide.

An Analysis of the Structural Relationship between Thyroid Hormone-Signaling Disruption and Polybrominated Diphenyl Ethers: Potential Implications for Male Infertility

Polybrominated diphenyl ethers (PBDEs) are a common class of anthropogenic organobromine chemicals with fire-retardant properties and are extensively used in consumer products, such as electrical and electronic equipment, furniture, textiles, and foams. Due to their extensive use, PBDEs have wide eco-chemical dissemination and tend to bioaccumulate in wildlife and humans with many potential adverse health effects in humans, such as neurodevelopmental deficits, cancer, thyroid hormone disruption, dysfunction of reproductive system, and infertility. Many PBDEs have been listed as chemicals of international concern under the Stockholm Convention on Persistent Organic Pollutants. In this study, the aim was to investigate the structural interactions of PBDEs against thyroid hormone receptor (TRα) with potential implications in reproductive function. Structural binding of four PBDEs, i.e., BDE-28, BDE-100, BDE-153 and BDE-154 was investigated against the ligand binding pocket of TRα using Schrodinger's induced fit docking, followed by molecular interaction analysis and the binding energy estimation. The results indicated the stable and tight binding of all four PDBE ligands and similarity in the binding interaction pattern to that of TRα native ligand, triiodothyronine (T3). The estimated binding energy value for BDE-153 was the highest among four PBDEs and was more than that of T3. This was followed by BDE-154, which is approximately the same as that of TRα native ligand, T3. Furthermore, the value estimated for BDE-28 was the lowest; however, the binding energy value for BDE-100 was more than BDE-28 and close to that of TRα native ligand, T3. In conclusion, the results of our study suggested the thyroid signaling disruption potential of indicated ligands according to their binding energy order, which can possibly lead to disruption of reproductive function and infertility.

Fish and the Thyroid: A Janus Bifrons Relationship Caused by Pollutants and the Omega-3 Polyunsaturated Fatty Acids

Benefits of the omega-3 polyunsaturated fatty acids (PUFA) on a number of clinical disorders, including autoimmune diseases, are widely reported in the literature. One major dietary source of PUFA are fish, particularly the small oily fish, like anchovy, sardine, mackerel and others. Unfortunately, fish (particularly the large, top-predator fish like swordfish) are also a source of pollutants, including the heavy metals. One relevant heavy metal is mercury, a known environmental trigger of autoimmunity that is measurable inside the thyroid. There are a number of interactions between the omega-3 PUFA and thyroid hormones, even at the level of the thyroid hormone transport proteins. Concerning the mechanisms behind the protection from/amelioration of autoimmune diseases, including thyroiditis, that are caused by the omega-3 PUFA, one can be the decreased production of chemokines, a decrease that was reported in the literature for other nutraceuticals. Recent studies point also to the involvement of resolvins. The intracellular increase in resolvins is associated with the tissue protection from inflammation that was observed in experimental animals after coadministration of omega-3 PUFA and thyroid hormone. After having presented data on fish consumption at the beginning, we conclude our review by presenting data on the market of the dietary supplements/nutraceuticals. The global omega-3 products market was valued at USD 2.10 billion in 2020, and was projected to go up at a compound annual growth rate of 7.8% from 2020 to 2028. Among supplements, fish oils, which are derived mainly from anchovies, are considered the best and generally safest source of omega-3. Taking into account (i) the anti-autoimmunity and anti-cancer properties of the omega-3 PUFA, (ii) the increasing incidence of both autoimmune thyroiditis and thyroid cancer worldwide, (iii) the predisposing role for thyroid cancer exerted by autoimmune thyroiditis, and (iv) the risk for developing metabolic and cardiovascular disorders conferred by both elevated/trendwise elevated serum TSH levels and thyroid autoimmunity, then there is enough rationale for the omega-3 PUFA as measures to contrast the appearance and/or duration of Hashimoto's thyroiditis as well as to correct the slightly elevated serum TSH levels of subclinical hypothyroidism.

Interactions among thyroid hormones and serum lipid levels in association with PCB exposure in the Mohawk Akwesasne population

Alterations in thyroid function and serum lipid levels were assessed in relation to exposure to polychlorinated biphenyls (PCBs) and three chlorinated pesticides (DDE, hexachorobenzene and mirex) in a sample of Akwesasne Mohawk adults. This population is highly exposed to PCBs because of living in close proximity to three aluminum foundries that used PCBs as hydraulic fluids, which then contaminated local fish, wildlife, water, air and soils. The goal was to assess interactions between thyroid function (TSH, T3, T4 and fT4) and serum lipids (cholesterol, triglycerides and total serum lipids) in relation to concentrations of 101 PCB congeners and three chlorinated pesticides. Previous studies in this population have shown that elevated concentrations of PCBs resulted in suppression of thyroid function in adolescents, and increased risk of clinical hypothyroidism in adults, as well as an elevation in serum lipids. However in adjusted analyses of PCB concentrations of 703 adults we find only small and inconsistent associations between serum PCB levels and thyroid function. The most striking observations were strong significant positive associations between TSH and T3 with serum lipids and a negative association with fT4 in women. Because elevated serum lipids increase risks of other diseases the respective roles of thyroid hormones and PCBs in regulation of serum lipids requires additional study.

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene-environment interactions underlying the pathology of thyroid diseases.

Effects of organochlorine exposure on male reproductive disorders in an electronic waste area of South China

Several studies suggest that organochlorine exposure can affect male reproductive functions, causing poor semen quality, endocrine disruption, or dysregulation of thyroid hormones. This study uses multiple linear regression (MLR) models to analyze the correlation between male reproductive functions and polychlorinated biphenyl (PCBs) congeners or p,p'-DDE levels in serum, semen, and indoor dust samples. Multiple comparisons were all adjusted using the false discovery rate (FDR). The results revealed that the PCB congener levels in seminal plasma were significantly associated with the quality parameters of human semen (i.e., sperm count, morphology, and motility) and thyroid hormones after adjusting for covariates, e.g., associations of the sperm concentration with levels of CB105 (β = -0.323, 95% CI: -0.561, -0.085, p = 0.009), CB44 (β = 0.585, 95% CI: 0.290, 0.880, p < 0.001), and CB66 (β = -0.435, 95% CI: -0.728, -0.143, p = 0.004) in the seminal plasma were observed. Correlations between serum pollutants levels and the semen quality, reproductive hormones, or thyroid hormones were also observed. Moreover, our results demonstrate that the quantification of PCBs in seminal plasma can better describe male reproductive disorders than that in serum or dust. Organochlorine exposure measured in serum or dust, especially in seminal plasma, was associated with semen quality, as well as reproductive and thyroid hormones, thus suggesting that the impacts of persistent pollutants on male reproductive health require further investigation.

Endocrine Disrupting Chemicals and Reproductive Health in Boys and Men

Male reproductive health has declined as indicated by increasing rates of cryptorchidism, i.e., undescended testis, poor semen quality, low serum testosterone level, and testicular cancer. Exposure to endocrine disrupting chemicals (EDCs) has been proposed to have a role in this finding. In utero exposure to antiandrogenic EDCs, particularly at a sensitive period of fetal testicular development, the so-called 'masculinization programming window (MPW)', can disturb testicular development and function. Low androgen effect during the MPW can cause both short- and long-term reproductive disorders. A concurrent exposure to EDCs may also affect testicular function or damage testicular cells. Evidence from animal studies supports the role of endocrine disrupting chemicals in development of male reproductive disorders. However, evidence from epidemiological studies is relatively mixed. In this article, we review the current literature that evaluated relationship between prenatal EDC exposures and anogenital distance, cryptorchidism, and congenital penile abnormality called hypospadias. We review also studies on the association between early life and postnatal EDC exposure and semen quality, hypothalamic-pituitary-gonadal axis hormone levels and testicular cancer.

Associations of PCBS, dioxins and furans with follicle-stimulating hormone and luteinizing hormone in postmenopausal women: National Health and Nutrition Examination Survey 1999-2002

BACKGROUND

The general population is exposed to the group of endocrine disrupting chemicals persistent organic pollutants (POPs), that includes polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs).

OBJECTIVES

The aim of this research was to evaluate the associations of serum levels of PCB, PCDD, and PCDF congeners with follicle stimulating hormone (FSH) and luteinizing hormone (LH) in postmenopausal women not taking exogenous hormones. We hypothesized that associations of POPs with these gonadotropins could be modified by factors affecting endogenous hormones.

METHODS

Cross-sectional analyses were conducted on data from 89 postmenopausal women using data from the National Health and Nutrition Examination Survey (NHANES). POPs were summarized based on classification schemes thought to reflect toxicological properties. Associations of POPs and gonadotropin hormones were modeled with multivariable regression models. When evidence of interaction was found, conditional effects were estimated.

RESULTS

We found inverse associations of LH, but not FSH, with exposure to anti-estrogenic and/or dioxin-like POPs, but not with non dioxin-like PCBs. A doubling of dioxin-like toxic equivalents (TEQs) was associated with a decrease in LH of 11.9% (95% CI = -21.3%, -1.4%, p = 0.03). Inverse associations were enhanced by potential effect modifiers related to both direct and indirect estrogenicity, including obesity and the obesity-related condition inflammation.

CONCLUSIONS

These investigations support a pattern of endocrine-disrupting effects by dioxin-like POPs among postmenopausal women, especially those with conditions related to peripheral estrogenicity.

Multiple organochlorine pesticide exposures and measures of sex steroid hormones in adult males: Cross-sectional findings from the 1999-2004 National Health and Nutrition Examination Survey

BACKGROUND

Organochlorine pesticides are detectable in serum from most adults. Animal studies provide evidence of pesticide effects on sex hormones, suggesting that exposures may impact human reproductive function. Mounting evidence of sex differences in chronic diseases suggest that perturbations in endogenous sex hormones may influence disease risk. However, the association between organochlorine pesticide exposure and sex hormone levels in males across the lifespan is not well understood.

METHODS

We evaluated cross-sectional associations of lipid-adjusted serum concentrations of β-hexachlorocyclohexane, hexachlorobenzene, heptachlor epoxide, oxychlordane, dichlorodiphenyldichloroethylene (DDE), p,p'-dichlorodiphenyltrichloroethane (DDT), trans-nonachlor, and mirex in relation to sex steroid hormone levels [testosterone (ng/dL), sex hormone binding globulin (SHBG; nmol/L), estradiol (pg/mL), and androstanediol glucuronide (ng/dL)] in a sample of 748 males aged 20 years and older from the 1999-2004 cycles of the National Health and Nutrition Examination Survey (NHANES). Survey-weighted linear regression models were performed to estimate geometric means (GM) and their 95% confidence intervals (CIs) for quartiles of lipid-adjusted pesticide concentrations, adjusting for age, race, body mass index, serum lipids, smoking, education, and survey cycle.

RESULTS

Hexachlorobenzene concentration was positively associated with total estradiol (GM Q4 = 43.2 pg/mL (95% CI 36.5-51.1) vs. Q1 GM = 25.6 pg/mL (24.1-27.3), p-trend <0.0001) and free estradiol (GM Q4 = 0.77 pg/mL (95% CI 0.64-0.93) vs. Q1 GM = 0.47 pg/mL (0.44-0.51), p-trend = 0.002). Serum DDT concentration was positively associated with total estradiol (GM Q4 = 31.6 pg/mL (95% CI 25.9-38.5) vs. Q1 GM = 27.3 pg/mL (25.9-28.7), p-trend = 0.05) and free estradiol (GM Q4 = 0.60 pg/mL (95% CI 0.48-0.76) vs. Q1 GM = 0.50 pg/mL (0.47-0.53), p-trend 0.02). There was a suggestive inverse association of DDT and SHBG (GM Q4 = 29.2 nmol/L (95% CI 23.8-35.9) vs. Q1 GM = 33.9 nmol/L (32.3-35.5), p-trend 0.07). A positive association of β-hexachlorocyclohexane with total estradiol (GM Q4 = 30.3 pg/mL (95% CI 26.5-34.6) vs. Q1 GM = 26.7 pg/mL (24.5-29.0), p-trend = 0.09) was also suggestive but did not reach statistical significance. No distinct associations were observed for other hormone levels or other organochlorine pesticides.

CONCLUSIONS

Our findings suggest that select organochlorine pesticides may alter male estradiol levels. The positive associations with estradiol may implicate sex hormones as a possible mechanism for disease risk among those with organochlorine pesticide exposure.

Cross-Sectional and Longitudinal Effects of PCB Exposure on Human Stress Hormones in the German HELPcB Surveillance Program

Multiple pathological associations are attributed to PCBs (polychlorinated biphenyls). Research shows a positive association of PCBs with dehydroepiandrosterone sulfate (DHEAS) concentration but the results on the stress hormone cortisol have been inconsistent so far. This study is the first to examine not only the cross-sectional but also the longitudinal effects of PCB exposure on the stress hormones DHEAS and cortisol. Over a period of three years, 112 former employees occupationally exposed to PCBs were tested for their body burden with different types of PCBs (lower and higher chlorinated, dioxin-like and hydroxylated) and for their stress hormone concentration. Highly exposed employees showed a significantly higher risk for higher DHEAS values. Multiple linear regression analysis revealed a positive relationship between the exposure to lower chlorinated PCBs and DHEAS. Mixed models also revealed a significantly positive correlation between lower chlorinated PCBs with DHEAS when controlled for a cross-section. However, an effect for cortisol was not found. These results suggest a causal pathophysiological relationship between PCB exposure and DHEAS concentration, but not with cortisol. The health consequences of high DHEAS concentrations are discussed.

Association between polychlorinated biphenyl 153 exposure and serum testosterone levels: analysis of the National Health and Nutrition Examination Survey

Background

To examine the effects of environmental polychlorinated biphenyls (PCBs) 153 exposure, an industrial plasticizer, on serum testosterone levels.

Methods

Using data collected from the 1999-2000 and 2001-2002 National Health and Nutrition Examination Survey (NHANES), we analyzed serum total testosterone and PCB153 levels, demographic data and comorbidities for men aged 18 years and older. Univariate and multivariate linear regression analysis was used to evaluate the association between total testosterone and serum PCB153.

Results

Five hundred and fifty-seven men met inclusion criteria. Median age was 45.7 [33.4-60.4] years old while median serum total testosterone and PCB153 levels were 479 [352.5-607] ng/dL and 0.20 [0.11-0.39] ng/g, respectively. Increasing age, higher body mass index (BMI), higher levels of serum PCB153, lower levels of activity and a history of diabetes mellitus and coronary heart disease were associated with decreasing serum testosterone levels on univariate linear regression. On multivariate linear regression, increasing age (estimate -6.29 ng/dL per year of life, P<0.001) and BMI (estimate -7.08 ng/dL per unit BMI, P<0.001) were associated with declining serum testosterone levels. While serum PCB153 levels were found to be negatively correlated with serum testosterone levels on univariate analysis (estimate -179.67, P<0.001), this association was not significant on the multivariable model (estimate -12.83, P=0.673).

Conclusions

In this population-based analysis, we report an association between a decrease in serum testosterone with increasing serum levels of PCB153. Identifying environmental factors for etiology of low testosterone and mechanisms for causation will be important to aid in strategies to increase testosterone naturally in men.

Reproductive Function in a Population of Young Faroese Men with Elevated Exposure to Polychlorinated Biphenyls (PCBs) and Perfluorinated Alkylate Substances (PFAS)

Semen quality may be adversely affected by exposure to environmental chemicals such as polychlorinated biphenyls (PCBs) and perfluorinated alkylate substances (PFASs) that are persistent and may act as endocrine disrupting compounds. The aim of this study was to explore whether PCBs or PFASs exposure were associated with abnormalities in semen quality or reproductive hormones in Faroese men. This population based cross-sectional study includes 263 Faroese men (24⁻26 years) who delivered a semen sample for assessment of sperm concentration, total sperm count, semen volume, morphology and motility. A blood sample was drawn and analyzed for reproductive hormones, PCBs and PFASs. Exposure to ∑PCBs and perfluorooctane sulfonate (PFOS) was positively associated with sex hormone-binding globulin (SHBG) and luteinizing hormone (LH). In addition, total testosterone (T) was positively associated with ∑PCB. Both PCBs and PFOS appear to lead to increased SHBG, perhaps mediated via the liver. The higher total T associated with PCB may represent a compensatory adaption to elevated SHBG levels to maintain an unchanged free testosterone concentration. The positive association to LH for both PCBs and PFOS may indicate a direct adverse effect on the testosterone producing Leydig cells.

Exposure to polybrominated diphenyl ethers and phthalates in healthy men living in the greater Montreal area: A study of hormonal balance and semen quality

Studies investigating the associations between exposure of young men to polybrominated diphenyl ethers (PBDEs) or phthalates and hormone levels or semen quality have produced inconsistent results. Our goal was to investigate the association of exposure to PBDEs or phthalate metabolites with changes in markers of thyroid (TSH, free T3 and free T4) and reproductive function (sperm concentrations, motility, and quality; serum LH and testosterone) in 153 healthy young men from the greater Montreal area. Using covariate-adjusted models, we found that each 10-fold increase in BDE-47 was associated with lower TSH levels (-17.3%; 95% CI: -31.5, 0.0; p = 0.05). BDE-47 exposure was also associated with a decrease in sperm concentration (-19.7%; 95% CI: -36.8; 2.0; p = 0.07) and motility (-25.5%; 95% CI: -44.5, 0.1; p = 0.05). Trends towards decreases in these parameters were also observed in association with exposure to BDE-100 and the sum of BDE-47, -99, and -100 (∑₃BDEs). These associations were not accompanied by effects on sperm chromatin quality, as assessed with the HT-COMET assay. There were no substantial associations between urinary phthalate metabolite concentrations, either individually or grouped by molecular weight or parent compound, and sperm quality parameters; however, there was a positive association between elevated MECCP and free T4 (0.98; 95% CI: 0.02, 1.94; p = 0.05). Inverse associations between BDE-47 and ∑₃BDEs and free T3 and positive associations between MEHP and free T3 were stronger among individuals with BMI ≥ 25, suggesting that weight status may modify the effects of these endocrine disrupting chemicals.

Alterations in male reproductive hormones in relation to environmental DDT exposure

DDT [1, 1, 1-trichloro-2,2-bis (p-chlorophenyl)-ethane] compounds are used for indoor residual spraying (IRS) to control malaria mosquitoes. DDT is an endocrine disruptor chemical in experimental conditions, but little is known of adverse effects related to living conditions with continual uptake across a time span by all possible means of exposure. Based on estrogenic and/or anti-androgenic effects found in animal studies, we hypothesized that chronic DDT/DDE exposures in men may be associated with changes in male reproductive hormones. We tested this hypothesis by compared the magnitude and direction of associations between DDT and DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene) concentrations and male reproductive hormones in samples collected from IRS and non-IRS areas. We sampled a cross-section of 535 men (aged 18-40 years). Men living in IRS villages had significantly higher DDT and DDE concentrations compared with men from non-IRS villages. Men with DDT or DDE uptake (as reflected in detectable plasma concentrations) had significantly higher total-, free and bio-available testosterone (T), and lower follicle stimulating hormone (FSH) concentrations; lower luteinizing hormone (LH) concentrations were only evident with DDT uptake. To establish a dose-dependent effect, four sub-categories were defined. Men with the highest DDT (74-519 μg/g) and DDE (173-997 μg/g) concentrations had significantly higher total-, free and bio-available T, and lower FSH concentrations compared with subjects with non-detectable isomer concentrations. Estradiol concentrations were significantly higher in men with DDT and DDE concentrations in both the third (DDE: 27-172 μg/g; DDT: 5-73 μg/g) and fourth (DDE: 173-997 μg/g; DDT: 74-519 μg/g) categories. Men from IRS villages were significantly more likely to have higher total and bioavailable T as well as higher estradiol concentrations OR = 2.5 (95% CI 1.2, 3.2); OR 2.5 (95% CI 1.6, 4.0) and OR = 2.3 (95% CI 1.3, 4.1) compared to men from non-IRS villages, after controlling for age, BMI, personal use of pesticides, and smoking. Men living in IRS villages with life-long exposure (17.6 (±6) years) at the current residence with multiple exposure modalities incurred the highest degree of physiological imbalance over and above circulating isomer concentrations. Further studies are needed to elucidate the health implications of these findings.

Polychlorinated biphenyls, indicators of thyroid function and thyroid autoantibodies in the Anniston Community Health Survey I (ACHS-I)

In this study, we examined associations between serum concentrations of 35 polychlorinated biphenyl (PCB) congeners, pesticides, and indicators of thyroid function in participants of the Anniston Community Health Survey (ACHS). Study subjects lived in the vicinity of a former PCB production facility and had PCB concentrations 2 to 3 times higher than similar age and race groups from the general population. We investigated associations among serum levels of thyroid hormones (thyroxin [T4], free thyroxin [fT4], triiodothyronine [T3], thyroid stimulation hormone [TSH]) and auto-antibodies (thyroglobulin antibody [TgAb] or thyroperoxidase antibody [TPOAb]) and combined indicators of thyroid function with the sum of PCBs, varying PCB groups, individual PCB congeners, and 8 pesticides. Logistic and linear regression models were adjusted for log10 transformed total lipids, age, sex, ethnicity, BMI, smoking, and family history of thyroid disease. We also performed analyses stratified by ethnicity and sex. Linear regression showed inverse associations between TT3 and thyroid-like PCBs (sum of PCBs 28, 52, 74, 101, 105, and 118; p = .0004), two pesticides (hexachlorobenzene, and pp'-DDE), and individual congeners (PCBs 74, 105). Null associations were observed between PCBs, pesticides, TSH, TT4, and fT4. Logistic regression analyses did not provide support for TT3 findings and found no association with other thyroid hormones, antibodies, or combined indicator of thyroid function. These results suggest there is little evidence that these chemicals have any major clinical effect on thyroid function in this highly PCB exposed population.

Associations between serum polybrominated diphenyl ethers and thyroid hormones in a cross sectional study of a remote Alaska Native population

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants. Arctic indigenous peoples are exposed to PBDEs through a traditional diet high in marine mammals. PBDEs disrupt thyroid homeostasis. The aim of this study was to assess the relationship between serum PBDEs and thyroid function in a remote population of St. Lawrence Island Yupik. Serum samples were collected from 85 individuals from St. Lawrence Island, Alaska and measured for concentrations of PBDEs, free and total thyroxine (T4), free and total triiodothyronine (T3), and thyroid stimulating hormone (TSH). The relationships between PBDEs and thyroid hormones were assessed using multiple linear regression fit with generalized estimating equations. Serum concentrations of several Penta-BDE congeners (BDE-28/33, 47, and 100) were positively associated with concentrations of TSH and free T3, while serum concentration of BDE-153 was negatively associated with total T3 concentrations. Both BDE-47 and 153 remained significantly associated with thyroid hormones when BDE-47, BDE-153, and BDE-209 were covariates in the same model. There were no significant relationships between serum concentrations of PBDEs and either free or total T4. Individual PBDEs are associated with thyroid hormones in serum from a remote population of Alaska Natives, and directions of effect differ by congener.

Determination of phenolic organohalogens in human serum from a Belgian population and assessment of parameters affecting the human contamination

Many in vitro or in vivo studies highlighted the potential deleterious effects of phenolic organohalogenated compounds (POHs) on the health, particularly on the thyroid system homeostasis, however few large scale human epidemiological studies have been carried out, especially in Europe. Further studies monitoring the human contamination by POHs, the sources of exposure and the influence of these compounds on thyroid health are still needed. Therefore we determined the concentrations of 16 POHs (pentachlorophenol (PCP), tetrabromobisphenol A (TBBPA), 4 bromophenols (BPs), 3 hydroxy-polybromodiphenylethers (OH-PBDEs) and 7 hydroxy-polychlorobiphenyls (OH-PCBs)) in serum from 274 people aged from 18 to 76years old living in Liege (Belgium) and the surrounding area. A questionnaire about their alimentary habits, life style and home environment was also administered to the volunteers. The predominant compound measured in the population was PCP (median concentration of 593.0pgmL^-1). 4-OH-CB 107, 4-OH-CB 146 and 4-OH-CB 187 were detected in all samples and contributed for 75% of the sum of OH-PCBs (ΣOH-PCBs). The median measured in our population for ΣOH-PCBs was 143.7pgmL^-1. TBBPA and 2,4,6-tribromophenol were detected in 31% and 63.8% of the samples respectively while the detection frequency observed for the other BPs and the OH-PBDEs was close to zero. We computed multivariate regression models in order to assess the influence of demographic and lifestyle parameters on the PCP and ΣOH-PCBs contamination levels. Significant correlation was found between the PCP concentration and sex, smoker status, sea fish consumption and level of education, although the model seemed to be a poor (R²=0.14) predictor of the PCP concentration. The model computed for ΣOH-PCBs was more explanatory (R²=0.61) and involved age, BMI and sea fish consumption. Finally, we assessed the parameters affecting the ΣOH-PCBs/ΣPCBs ratio. The model proposed involved age, BMI, smoker status and parent PCB level, and explained 41% of the variability of the ΣOH-PCBs/ΣPCBs ratio.

In utero and childhood DDT, DDE, PBDE and PCBs exposure and sex hormones in adolescent boys: The CHAMACOS study

Dichlorodiphenyltrichloroethane (DDT), polybrominated diphenyl ether (PBDE) flame retardants, and polychlorinated biphenyls (PCBs) are believed to be endocrine-disrupting chemicals (EDCs) in humans and animals. The purpose of this study is to examine the relationship of in utero and childhood exposure to these purported EDCs and reproductive hormones in adolescent boys who participated in CHAMACOS, an ongoing birth cohort in California's Salinas Valley. We measured o,p'- and p,p'-DDT, p,p'-DDE, PBDEs and PCBs in serum collected from mothers during pregnancy or at delivery and from their sons at 9 years. We measured concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and total testosterone (T) from 234 of their sons at 12 years. In adjusted models, we found that a 10-fold increase in maternal prenatal serum concentrations of BDE-153 was associated with a 22.2% increase (95% CI: 1.0, 47.9) in FSH, a 96.6% increase (95% CI: 35.7, 184.7) in LH, and a 92.4% increase (95% CI: 20.9, 206.2) increase in T. Similarly, BDE-100 concentrations were associated with increases in boys' LH levels. A 10-fold increase in total prenatal ΣPCBs was associated with a 64.5% increase (95% CI: 8.6, 149.0) in FSH, primarily driven by non- dioxin-like congeners. Boys' hormone levels were only marginally associated with prenatal DDT or DDE in primary models, but when boys' Tanner stage at age 12 was added to models, prenatal maternal DDT levels were associated with decreases in LH (adjusted percent change per 10-fold increase=-18.5%, 95% CI: -29.8, -5.4) and T (percent change=-18.2%, 95% CI: -30.2, -4.2) and DDE with LH (percent change=-18.3%, 95% CI: -32.9, -0.6). Exposures measured in the children's serum at 9 years also showed associations between BDE-153 and ΣPCBs. However, there is evidence that these associations appear to be mediated by child BMI. This study suggests associations on male hormones of 12year old boys related to exposure to certain EDC exposure prenatally. The implications on future reproductive function in puberty and adulthood should be determined.

Pesticide exposure and thyroid function in an agricultural population in Brazil

Although numerous pesticides may interfere with thyroid function, however, epidemiological evidence supporting this relationship is limited, particularly regarding modern non-persistent pesticides. We sought to evaluate the association of agricultural work practices, use of contemporary-use pesticides, and OC pesticides residue levels in serum with circulating thyroid hormone levels in an agricultural population. A cross-sectional study was conducted with a random sample of 275 male and female farm residents in Farroupilha, South of Brazil. Information on sociodemographics, lifestyle and agricultural work was obtained through questionnaire. Blood samples were collected on all participants and analyzed for cholinesterase activity, serum residues of OC pesticides, and levels of free T4 (FT4), total T3 (TT3) and TSH. Non-persistent pesticides exposure assessment was based on questionnaire information on current use of pesticides, and frequency and duration of use, among others. Associations were explored using multivariate linear regression models. Total lifetime years of use of fungicides, herbicides and dithiocarbamates in men was associated with increased TSH accompanied by decrease in FT4, with evidence of a linear trend. In addition, there was an association between being sampled in the high pesticide-use season and increased TSH levels. Conversely, farm work and lifetime use of all pesticides were related with slight decrease in TSH and increased TT3 and FT4, respectively. In general, pesticide use was not associated with thyroid hormones in women. Subjects with detected serum concentrations of β-hexachlorocyclohexane, endrin, dieldrin, heptachlor epoxide B, γ-chlordane, transnonachlor, heptachlor, p,p'-dichlorodiphenylethane and endosulfan II experienced slight changes in TT3; however, associations were weak and inconsistent. These findings suggest that both cumulative and recent occupational exposure to agricultural pesticides may affect the thyroid function causing hypothyroid-like effects, particularly in men.

Association between organochlorine pesticide exposure and thyroid hormones in floriculture workers

Several studies have suggested that exposure to DDT may be related to changes in thyroid hormone levels in animals and humans, even though results across studies are inconsistent. The aim of this study was to assess the association between exposure to p,p'-DDE (a stable metabolite of DDT) and serum levels of thyroid hormones in floriculture workers. A longitudinal study was conducted on 136 male subjects from the States of Mexico and Morelos, Mexico, who were occupationally exposed to pesticides, during agricultural periods of high (rainy season) and low (dry season) levels of pesticide application. Using a structured questionnaire, a survey was carried out on socio-demographic characteristics, anthropometry, clinical history, alcohol and tobacco consumption, residential chemical exposure, and occupational history. Blood and urine samples were collected to determine serum levels of TSH, total T3, total T4, and p,p'-DDE, and metabolites of organophosphate pesticides (OP), respectively. The analysis of the associations between p,p'-DDE levels and thyroid hormone profile adjusting by potential confounding variables including urinary OP metabolites was carried out using multivariate generalized estimating equation (GEE) models. Our results showed that the geometric means of p,p'-DDE levels were 6.17 ng/ml and 4.71 ng/ml in the rainy and dry seasons, respectively. We observed positive associations between the serum levels of p,p'-DDE and those of total T3 (β=0.01, 95% CI: -0.009, 0.03), and total T4 (β=0.08, 95% CI:0.03, 0.14) and negative but no significant changes in TSH in male floricultural workers, supporting the hypothesis that acts as thyroid disruptor in humans.

Exposure to polychlorinated biphenyls and the thyroid gland - examining and discussing possible longitudinal health effects in humans

BACKGROUND

Many previous studies have dealt with the effect of polychlorinated biphenyls (PCBs) on the thyroid gland, but their findings are inconsistent. One problem of these studies has been their use of cross-sectional designs.

OBJECTIVES

The aim of the current study is to investigate longitudinal effects of PCBs on the thyroid gland, focusing on: morphological changes in thyroid tissue (i.e. thyroid volume), changes in thyroid hormones and in thyroid antibodies.

METHODS

A total of 122 individuals (Mage=44.7) were examined over a period of four years (t(1) until t(4)). Medical history was collected via interviews, an ultrasound examination was performed and blood samples were taken to determine plasma PCB levels, thyroid stimulating hormone (TSH), free triiodthyronine (fT3), free thyroxine (fT4), thyroid peroxidase antibodies (TPOab), thyreoglobulin antibodies (TGab) and thyroid-stimulating hormone receptor antibodies (TSHRab). Rank correlation coefficients and mixed effect models were performed controlling for age and total lipids.

RESULTS

There were negative correlations between higher chlorinated biphenyls and fT3, cross-sectionally as well as longitudinally. We also found an interaction effect of higher-chlorinated PCBs over time for fT4 as well as TSHRab. In case of high exposure, a decrease in fT4 and an increase in TSHRab level were found over time. In regards to the other variables, our findings yielded no clear results in the examined time period.

CONCLUSION

This is the first study to shows a PCB-related effect on fT3, fT4 and TSHRab over a four year period. The data also suggest that morphological and antibody findings remain inconsistent and do not allow for unambiguous interpretation.

PBDE flame retardants, thyroid disease, and menopausal status in U.S. women

BACKGROUND

Women have elevated rates of thyroid disease compared to men. Environmental toxicants have been implicated as contributors to this dimorphism, including polybrominated diphenyl ethers (PBDEs), flame retardant chemicals that disrupt thyroid hormone action. PBDEs have also been implicated in the disruption of estrogenic activity, and estrogen levels regulate thyroid hormones. Post-menopausal women may therefore be particularly vulnerable to PBDE induced thyroid effects, given low estrogen reserves. The objective of this study was to test for an association between serum PBDE concentrations and thyroid disease in women from the United States (U.S.), stratified by menopause status.

METHODS

Serum PBDE concentrations (BDEs 47, 99, 100 and 153) from the National Health and Examination Survey (NHANES) and reports on thyroid problems were available in the NHANES 2003-2004 cycle. Odds ratios (ORs) were calculated using multivariate logistic regression models accounting for population-weighted survey techniques and controlling for age, body mass index (BMI), education, smoking, alcohol consumption and thyroid medication. Menopause status was obtained by self-reported absence of menstruation in the previous 12 months and declared menopause.

RESULTS

Women in the highest quartile of serum concentrations for BDEs 47, 99, and 100 had increased odds of currently having thyroid disease (ORs: 1.5, 1.8, 1.5, respectively) compared to the reference group (1st and 2nd quartiles combined); stronger associations were observed when the analysis was restricted to postmenopausal women (ORs: 2.2, 3.6, 2.0, respectively).

CONCLUSION

Exposure to BDEs 47, 99, and 100 is associated with thyroid disease in a national sample of U.S. women, with greater effects observed post-menopause, suggesting that the disruption of thyroid signaling by PBDEs may be enhanced by the altered estrogen levels during menopause.

Polybrominated diphenyl ether exposure and reproductive hormones in North American men

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are flame retardant chemicals that are persistent organic pollutants. Animal experiments and some human studies indicate that PBDEs may adversely affect male reproductive function.

OBJECTIVES

To assess the association between PBDE exposure and reproductive hormones (RHs) in a North American male adult cohort.

METHODS

From 2010-11, we collected three serum samples from 27 healthy adult men. We assessed associations between PBDEs and RHs using mixed effect regression models.

RESULTS

PBDEs were inversely associated with inhibin-B. In older men, increased concentrations of BDE-47 and BDE-100 were significantly associated with a decrease in inhibin-B, and an increase in follicular stimulating hormone (FSH).

CONCLUSIONS

These findings suggest PBDE exposure may affect RHs in older men. We did not measure other parameters of male reproductive function and therefore these results are preliminary.

A Preliminary Link between Hydroxylated Metabolites of Polychlorinated Biphenyls and Free Thyroxin in Humans

BACKGROUND

Polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (HO-PCBs) interfere with thyroid hormone action both in vitro and in vivo. However, epidemiologic studies on the link between PCB exposure and thyroid function have yielded discordant results, while very few data are available for HO-PCBs.

OBJECTIVES

Our study aimed at investigating the relationship between clinically available markers of thyroid metabolism and serum levels of both PCBs and HO-PCBs.

SUBJECTS AND METHODS

In a group of 180 subjects, thyroid-stimulating hormone (TSH) and free thyroxin (fT4), 29 PCBs (expressed both in lipid weight and in wet weight) and 18 HO-PCBs were measured in serum.

RESULTS

In regression models, adjusted for gender, age, current smoking behavior, BMI and total lipid levels, serum levels of 3HO-PCB118 and 3HO-PCB180, and PCB95(lw), PCB99(lw) and PCB149(lw) were independent, significant predictors of fT4. A stepwise, multiple regression with gender, age, current smoking behavior, BMI and total lipid levels and all five previously identified significant compounds retained age, BMI, PCB95(lw), PCB99(lw) and 3HO-PCB180 as significant predictors of fT4. TSH levels were not predicted by serum levels of any of the PCBs or HO-PCBs.

CONCLUSIONS

Our study indicates that in vivo, circulating fT4 levels can be linked to serum levels of several PCBs and hydroxylated PCB metabolites.

Associations of bisphenol A and polychlorinated biphenyls with spermatogenesis and steroidogenesis in two biological fluids from men attending an infertility clinic

BACKGROUND

In the testis, steroid hormones play an important role in spermatogenesis, the production of semen, and the maintenance of secondary sex characteristics and libido. They may also play a role as a target for substances called endocrine disruptors (EDs). As yet, however, no complex study has been conducted evaluating the relationships between EDs and the steroid spectrum in the plasma and seminal plasma.

OBJECTIVES

To shed more light into mechanisms of EDs and the effects of bisphenol A (BPA) and polychlorinated biphenyls (PCBs) on human spermatogenesis and steroidogenesis.

METHODS

We determined BPA and 11 steroids in the plasma and seminal plasma of 191 men with different degrees of fertility, using a newly developed liquid-chromatography mass spectrometry method. Concurrently, plasma levels of 6 congeners of PCBs, gonadotropins, selenium, zinc and homocysteine were measured. Partial correlations adjusted for age, BMI and abstinence time were performed to evaluate relationships between these analytes.

RESULTS

Seminal BPA, but not plasma BPA, was negatively associated with sperm concentration (r=-0.198; p=0.009), sperm count (r=-0.178; p=0.018) and morphology (r=-0.160; p=0.044). Divergent and sometimes opposing associations of steroids and BPA were found in both body fluids. The sum of PCB congeners was negatively associated with testosterone, free testosterone, the free androgen index and dihydrotestosterone in plasma.

CONCLUSION

BPA may negatively contribute to the final state of sperm quality. Moreover, our data indicate that BPA influences human gonadal and adrenal steroidogenesis at various steps. Environmental levels of PCBs negatively correlated with androgen levels, but surprisingly without negative effects on sperm quality.

Effects of PCBs and PBDEs on thyroid hormone, lymphocyte proliferation, hematology and kidney injury markers in residents of an e-waste dismantling area in Zhejiang, China

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are two typical categories of contaminants released from e-waste dismantling environments. In China, the body burdens of PCBs and PBDEs are associated with abnormal thyroid hormones in populations from e-waste dismantling sites, but the results are limited and contradictory. In this study, we measured the serum levels of PCBs and PBDEs and the thyroid hormone free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) in 40 residents in an e-waste dismantling area and in 15 residents in a control area. Additionally, we also measured some lymphocyte proliferation indexes, hematologic parameters and kidney injury markers, including white blood cells, neutrophils, monocytes, lymphocytes, hemoglobin, platelets, serum creatinine and beta 2-microglobulin (β2-MG). The results indicated that the mean level of ΣPCBs in the exposure group was significantly higher than that in the control group (964.39 and 67.98 ng g(-1), p<0.0001), but the mean level of ΣPBDEs in the exposure group was not significantly higher than that in the controls (139.32 vs. 75.74 ng g(-1), p>0.05). We determined that serum levels of FT3, FT4, monocytes and lymphocytes were significantly lower, whereas the levels of neutrophils, hemoglobin, platelets and serum creatinine were significantly higher in the exposed group (p<0.05). The mean level of ΣPCBs was negatively correlated with levels of FT3, FT4, monocytes and lymphocytes (p<0.05) and positively correlated with levels of neutrophils, hemoglobin, serum creatinine and β2-MG (p<0.05). Additionally, the mean level of ΣPBDEs was positively correlated with levels of white blood cells, hemoglobin and platelets (p<0.05). Our data suggest that exposure to an e-waste dismantling environment may increase the body burdens of PCBs and the specific PBDEs congeners in native residents and that the contaminants released from e-waste may contribute to abnormal changes in body levels of thyroid hormone, hematology and kidney injury markers.

Maternal Polybrominated Diphenyl Ether (PBDE) Exposure and Thyroid Hormones in Maternal and Cord Sera: The HOME Study, Cincinnati, USA

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) reduce blood concentrations of thyroid hormones in laboratory animals, but it is unclear whether PBDEs disrupt thyroid hormones in pregnant women or newborn infants.

OBJECTIVES

We investigated the relationship between maternal PBDE levels and thyroid hormone concentrations in maternal and cord sera.

METHODS

We used data from the Health Outcomes and Measures of the Environment (HOME)Study, a prospective birth cohort of 389 pregnant women in Cincinnati, Ohio, who were enrolled from 2003 through 2006 and delivered singleton infants. Maternal serum PBDE concentrations were measured at enrollment (16 ± 3 weeks of gestation). Thyroid hormone concentrations were measured in maternal serum at enrollment (n = 187) and in cord serum samples (n = 256).

RESULTS

Median maternal serum concentrations of BDEs 28 and 47 were 1.0 and 19.1 ng/g lipid, respectively. A 10-fold increase in BDEs 28 and 47 concentrations was associated with a 0.85-μg/dL [95% confidence interval (CI): 0.05, 1.64] and 0.82-μg/dL (95% CI: 0.12, 1.51) increase in maternal total thyroxine concentrations (TT4), respectively. Both congeners were also positively associated with maternal free thyroxine (FT4). We also observed positive associations between BDE-47 and maternal total and free triiodothyronine (TT3 and FT3). A 10-fold increase in BDE-28 was associated with elevated FT3 concentrations (β = 0.14 pg/mL; 95% CI: 0.02, 0.26). In contrast, maternal PBDE levels were not associated with thyroid hormone concentrations in cord serum.

CONCLUSIONS

These findings suggest that maternal PBDE exposure, particularly BDEs 28 and 47, are associated with maternal concentrations of T4 and T3 during pregnancy.

In utero and childhood polybrominated diphenyl ether exposures and body mass at age 7 years: the CHAMACOS study

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are lipophilic flame retardants that bioaccumulate in humans. Child serum PBDE concentrations in California are among the highest worldwide. PBDEs may be associated with obesity by disrupting endocrine systems.

OBJECTIVE

In this study, we examined whether pre- and postnatal exposure to the components of pentaBDE mixture was associated with childhood obesity in a population of Latino children participating in a longitudinal birth cohort study in the Salinas Valley, California.

METHODS

We measured PBDEs in serum collected from 224 mothers during pregnancy and their children at 7 years of age, and examined associations with body mass index (BMI) at age 7 years.

RESULTS

Maternal PBDE serum levels during pregnancy were associated with higher BMI z-scores in boys (BMI z-score βadjusted = 0.26; 95% CI: -0.19, 0.72) but lower scores in girls (BMI z-score βadjusted = -0.41; 95% CI: -0.87, -0.05) at 7 years of age (pinteraction = 0.04). In addition, child's serum BDE-153 concentration (log10), but not other pentaBDE congeners, demonstrated inverse associations with BMI at age 7 years (BMI z-score βadjusted = -1.15; 95% CI: -1.53, -0.77), but there was no interaction by sex.

CONCLUSIONS

We estimated sex-specific associations with maternal PBDE levels during pregnancy and BMI at 7 years of age, finding positive associations in boys and negative associations in girls. Children's serum BDE-153 concentrations were inversely associated with BMI at 7 years with no difference by sex. Future studies should examine the longitudinal trends in obesity with PBDE exposure and changes in hormonal environment as children transition through puberty, as well as evaluate the potential for reverse causality.

Human exposure to PBDE and critical evaluation of health hazards

Polybrominated diphenyl ethers (PBDEs) are used in large quantities as flame-retardant additives in a number of commercial products. Biomonitoring data show that, in recent years, PBDE concentrations have increased rapidly in the bodies of wildlife and humans. Usually, PBDE levels in North America have been reported to be higher than those in Europe and Asia. Moreover, body burden of PBDEs is three- to ninefold higher in infants and toddlers than in adults, showing these last two age groups the highest levels of these compounds, due to exposure via maternal milk and through dust. Tetra-, Penta-, and Hexa-BDEs are the isomers most commonly found in humans. Based on studies on experimental animals, the toxicological endpoints of exposure to PBDEs are likely to be thyroid homeostasis disruption, neurodevelopmental deficits, reproductive changes, and even cancer. Experimental studies in animals and epidemiological observations in humans suggest that PBDEs may be developmental neurotoxicants. Pre- and/or postnatal exposure to PBDEs may cause long-lasting behavioral abnormalities, particularly on motor activity and cognition. This paper is focused on reviewing the current status of PBDEs in the environment, as well as the critical adverse health effects based on the recent studies on the toxic effects of PBDEs.

Monitoring chlorinated persistent organic pollutants in adolescents in Flanders (Belgium): concentrations, trends and dose-effect relationships (FLEHS II)

BACKGROUND

In 2007, the second cycle of the Flemish human biomonitoring survey started, with a main focus on 14-15 year-old adolescents.

OBJECTIVES

The main objectives were generating reference values for exposure markers, determining the pollution pressure in industrial hotspots and establishing dose-effect relationships between exposure to pollutants and hormone levels, sexual development, asthma and allergy, genotoxic and hematological markers.

METHODS

Geometric means with 95% confidence intervals (CI) were calculated for a reference population of 200 14-15 year-old adolescents. Stepwise multiple regression analyses with correction for confounders and covariates were performed to establish dose-effect relationships.

RESULTS

Geometric mean concentrations (with 95% CI) of 49.6 (45.7, 53.8), 70.8 (63.6, 78.8) and 8.34 (7.76, 8.97) n gg(-1) lipid for the sum of PCB 138, 153 and 180, p,p'-DDE and HCB were respectively 23%, 26% and 60% lower than those obtained five years earlier. Geometric mean concentrations of 108 (101, 114) and 32.1 (30.1, 34.2) pgCALUX-BEQg(-1) lipid were observed for the PCDD/Fs and dioxin-like PCBs, respectively. Multiple dose-effect relationships were observed between POPs and several effect markers, including positive (boys) and negative (girls) associations with data on sexual development and positive associations with asthma, animal allergy and free thyroxine (boys and girls).

CONCLUSIONS

Our findings suggest that chlorinated POP concentrations are decreasing over time and that even relatively low concentrations are associated with biological effects.

Persistent organic pollutants and male reproductive health

Environmental contaminants such as persistent organic pollutants (POPs) are man-made bioaccumulative compounds with long half-lives that are found throughout the world as a result of heavy use in a variety of consumer products during the twentieth century. Wildlife and animal studies have long suggested adverse effects of exposure to these compounds on human reproductive health, which, according to the endocrine disrupter hypothesis, are ascribed to the compounds’ potential to interfere with endocrine signaling, especially when exposure occurs during certain phases of fetal and childhood development. An extensive number of epidemiological studies have addressed the possible effects of exposure to POPs on male reproductive health, but the results are conflicting. Thus far, most studies have focused on investigating exposure and the different reproductive health outcomes during adulthood. Some studies have addressed the potential harmful effects of fetal exposure with respect to malformations at birth and/or reproductive development, whereas only a few studies have been able to evaluate whether intrauterine exposure to POPs has long-term consequences for male reproductive health with measurable effects on semen quality markers and reproductive hormone levels in adulthood. Humans are not exposed to a single compound at a time, but rather, to a variety of different substances with potential divergent hormonal effects. Hence, how to best analyze epidemiological data on combined exposures remains a significant challenge. This review on POPs will focus on current knowledge regarding the potential effects of exposure to POPs during fetal and childhood life and during adulthood on male reproductive health, including a critical revision of the endocrine disruption hypothesis, a comment on pubertal development as part of reproductive development and a comment on how to account for combined exposures in epidemiological research.

Thyroid hormones are associated with exposure to persistent organic pollutants in aging residents of upper Hudson River communities

The aim of this study was to evaluate the association between persistent organic pollutants (POPs) and thyroid hormones in an aging population. Forty-eight women and 66 men, aged 55-74 years and living in upper Hudson River communities completed a questionnaire and provided blood specimens. Serum was analyzed for thyrotropin (thyroid stimulating hormone, TSH), free (fT4) and total thyroxine (T4), total triiodothyronine (T3), and for POPs. POPs included 39 polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) determined by gas chromatography with electron capture detection (GC-ECD), and nine polybrominated diphenyl ethers (PBDEs) determined by high-resolution gas chromatography with high-resolution mass spectrometry detection (HRGC-HRMS). Multivariable linear regression analysis was used to evaluate associations between thyroid hormones and sums of POPs, adjusted for covariates and stratified by sex. Effects were expressed as differences in thyroid hormone levels associated with a doubling in the level of exposure. Among women, DDT+DDE increased T4 by 0.34μg/dL (P=0.04) and T3 by 2.78ng/dL (P=0.05). Also in women, sums of PCBs in conjunction with PBDEs elicited increases of 24.39-80.85ng/dL T3 (P<0.05), and sums of PCBs in conjunction with DDT+DDE elicited increases of 0.18-0.31μg/dL T4 (P<0.05). For men estrogenic PCBs were associated with a 19.82ng/dL T3 decrease (P=0.003), and the sum of estrogenic PCBs in conjunction with DDT+DDE elicited an 18.02ng/dL T3 decrease (P=0.04). Given age-related declines in physiologic reserve, the influence of POPs on thyroid hormones in aging populations may have clinical implications and merits further investigation.

Relationships of polychlorinated biphenyls and dichlorodiphenyldichloroethylene (p,p'-DDE) with testosterone levels in adolescent males

BACKGROUND

Concern persists over endocrine-disrupting effects of persistent organic pollutants (POPs) on human growth and sexual maturation. Potential effects of toxicant exposures on testosterone levels during puberty are not well characterized.

OBJECTIVES

In this study we evaluated the relationship between toxicants [polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p´-DDE), hexachlorobenzene (HCB), and lead] and testosterone levels among 127 Akwesasne Mohawk males 10 to < 17 years of age with documented toxicant exposures.

METHODS

Data were collected between February 1996 and January 2000. Fasting blood specimens were collected before breakfast by trained Akwesasne Mohawk staff. Multivariable regression models were used to estimates associations between toxicants and serum testosterone, adjusted for other toxicants, Tanner stage, and potential confounders.

RESULTS

The sum of 16 PCB congeners (Σ16PCBs) that were detected in ≥ 50% of the population was significantly and negatively associated with serum testosterone levels, such that a 10% change in exposure was associated with a 5.6% decrease in testosterone (95% CI: -10.8, -0.5%). Of the 16 congeners, the more persistent ones (Σ8PerPCBs) were related to testosterone, whereas the less persistent ones, possibly reflecting more recent exposure, were not. When PCB congeners were subgrouped, the association was significant for the sum of eight more persistent PCBs (5.7% decrease; 95% CI: -11, -0.4%), and stronger than the sum of six less persistent congeners (3.1% decrease; 95% CI: -7.2, 0.9%). p,p´-DDE was positively but not significantly associated with serum testosterone (5.2% increase with a 10% increase in exposure; 95% CI: -0.5, 10.9%). Neither lead nor HCB was significantly associated with testosterone levels.

CONCLUSIONS

Exposure to PCBs, particularly the more highly persistent congeners, may negatively influence testosterone levels among adolescent males. The positive relationship between p,p´-DDE and testosterone indicates that not all POPs act similarly.

CITATION

Schell LM, Gallo MV, Deane GD, Nelder KR, DeCaprio AP, Jacobs A; Akwesasne Task Force on the Environment. 2014. Relationships of polychlorinated biphenyls and dichlorodiphenyldichloroethylene (p,p´-DDE) with testosterone levels in adolescent males. Environ Health Perspect 122:304-309; http://dx.doi.org/10.1289/ehp.1205984.

The human body burden of polybrominated diphenyl ethers and their relationships with thyroid hormones in the general population in Northern China

This study was conducted to determine the human body burden of polybrominated diphenyl ethers (PBDEs) and then clarify the relationships between that and the disruption of thyroid hormones in the general population in Northern China. Between November 2010 and May 2011, 124 serum samples were obtained from volunteers from the provinces of Shanxi and Liaoning. Serum samples were prepared by solid-phase extraction and analyzed for BDE-17, 28, 47, 66, 99, 100, 153, 154, 183 and 209 by gas chromatography-negative chemical ionization mass spectrometry. The median concentration of the total PBDEs was 7.2 ng/g lipid weights (lw); concentrations ranged from 2.1 to 160.3 ng/glw. The PBDE profiles in this study differed from those of other general populations. BDE-209 was the most abundant congener (median, 5.0 ng/glw; range, non-detected - 157.1 ng/glw), accounting for more than 75% of the total PBDEs, followed by BDE-153. The total PBDE concentrations in men were significantly higher as compared to women. The donors' age was correlated with a few PBDE congeners, but was not correlated with the total PBDE concentrations. The overall level of PBDEs in this study was lower than that observed in general populations in Southern China, Europe, and North America. There were apparent correlations between concentrations of several PBDE congeners and thyroid hormones. Triiodothyronine (T₃) was correlated with BDE-99 and 209 and inversely correlated with BDE-17, 28, 47, 153, 183, and the summed tri- to hepta-PBDE congeners (∑₃₋₇PBDEs). Thyroid-stimulating hormone (TSH) was correlated with BDE-17, 28, 47, and 183 and inversely correlated with BDE-99. No correlation between free tetraidothyronine (FT₄) and PBDEs was observed. Logistic regression analysis results indicated that those with higher levels of BDE-17 or BDE-153 had significantly lower odds of having T₃ levels above the normal range compared to those with lower levels of BDE-17 or BDE-153. Association between FT₄ and BDE-153 disappeared after controlling for sex and age. However, there was no significant association between TSH and PBDEs. The results of the present study showed that even at a relatively low level, PBDEs might interfere with the thyroid hormone levels in the general population.

Long-term exposure to organochlorine pesticides and thyroid status in adults in a heavily contaminated area in Brazil

Organochlorine (OC) pesticides are endocrine disruptors altering the thyroid hormonal system. The aim of this study is to investigate the relationship between exposure to OC pesticides and thyroid status in adults from a rural area in Rio de Janeiro, Brazil, heavily contaminated with OC pesticides. A cross-sectional study was carried out in 303 men and 305 women >14 years old. Concentrations of 19 OC pesticides and levels of free thyroxine (T4), total triiodothyronine (T3), thyroid-stimulating hormone (TSH), anti-thyroperoxidase (TPOAb) and anti-thyroglobulin (TgAg) antibodies were analyzed in serum samples. Associations between OC pesticides concentrations and values of biochemical thyroid parameters were determined using multivariate regression models stratified by gender. Prevalence of subclinical hyperthyroidism and the presence of TPOAb antibodies were higher than those described for euthyroid populations elsewhere. After adjusting for confounders, total T3 levels were associated with lower concentrations of endosulphan 2 in men and with higher alpha-chlordane, p,p'-dichlorodiphenyltrichloroethane (DDT), endosulphan 2, and methoxychlor in women. Levels of free T4 showed inverse association with beta-hexachlorocyclohexane (HCH) and p,p'-DDT in men, and were positively associated with hexachlorobenzene (HCB), heptachlor, o,p'-DDT, and p,p'-DDT in women. TSH levels were associated with higher beta-HCH in men. A positive association was observed between exposure methoxychlor in males and presence of TPOAb, but no association with TPOAb was found in women. These results suggest that OC pesticides can affect the thyroid system through gender-specific mechanisms that may differ among compounds. Further detailed investigations and health monitoring should be warranted for this population.

Persistent toxic burdens of halogenated phenolic compounds in humans and wildlife

Halogenated phenolic compounds (HPCs) including hydroxylated polychlorobiphenyls (OH-PCBs) and hydroxylated polybromodiphenyl-ethers (OH-PBDEs) can be persistent organic pollutant (POP) metabolites or natural marine compounds. Structurally similar to thyroid hormones (THs), they are retained in blood, transported through selective barriers, and the cause of endocrine and neuronal POP effects. This study presents a meta-analysis of HPC burdens in human and wildlife tissues, including OH-PCBs, OH-PBDEs, Pentachlorophenol, and polybromophenols. HPC blood plasma levels were also compared to known in vitro and in vivo toxicological effect concentrations. Blood, highly perfused, and fetal tissues contained the highest levels of HPCs. Plasma concentrations of analyzed OH-PCBs/PBDEs ranged from 0.1 to 100 nM in humans and up to 240, 454, 800, and 7650 nM for birds, fish, cetaceans, and other mammals, respectively. These concentrations fully fall within the in vitro effect concentrations reported in literature for HPCs of 0.05-10000 nM. We strongly advise further study of HPC blood levels in the general population, children, and fetal tissue to establish background levels and the risk at sensitive development stages. As not all HPCs are, or can be, chemically analyzed, the application of additional bioanalysis might reveal an even greater toxicological relevance of HPCs. In addition, metabolic activation should always be included within in vitro hazard assessment of POPs.

Persistent organochlorine pollutants with endocrine activity and blood steroid hormone levels in middle-aged men

BACKGROUND

Studies relating long-term exposure to persistent organochlorine pollutants (POPs) with endocrine activities (endocrine disrupting chemicals) on circulating levels of steroid hormones have been limited to a small number of hormones and reported conflicting results.

OBJECTIVE

We examined the relationship between serum concentrations of dehydroepiandrosterone, dehydroepiandrosterone sulphate, androstenedione, androstenediol, testosterone, free and bioavailable testosterone, dihydrotestosterone, estrone, estrone sulphate, estradiol, sex-hormone binding globulin, follicle-stimulating hormone, and luteinizing hormone as a function of level of exposure to three POPs known to interfere with hormone-regulated processes in different way: dichlorodiphenyl dichloroethene (DDE), polychlorinated biphenyl (PCB) congener 153, and chlordecone.

METHODS

We collected fasting, morning serum samples from 277 healthy, non obese, middle-aged men from the French West Indies. Steroid hormones were determined by gas chromatography-mass spectrometry, except for dehydroepiandrosterone sulphate, which was determined by immunological assay, as were the concentrations of sex-hormone binding globulin, follicle-stimulating hormone and luteinizing hormone. Associations were assessed by multiple linear regression analysis, controlling for confounding factors, in a backward elimination procedure, in multiple bootstrap samples.

RESULTS

DDE exposure was negatively associated to dihydrotestosterone level and positively associated to luteinizing hormone level. PCB 153 was positively associated to androstenedione and estrone levels. No association was found for chlordecone.

CONCLUSIONS

These results suggested that the endocrine response pattern, estimated by determining blood levels of steroid hormones, varies depending on the POPs studied, possibly reflecting differences in the modes of action generally attributed to these compounds. It remains to be investigated whether this response pattern is predictive of the subsequent occurrence of disease.

Associations between brominated flame retardants in house dust and hormone levels in men

Brominated flame retardants (BFRs) are used in the manufacture of a variety of materials and consumer products in order to meet fire safety standards. BFRs may persist in the environment and have been detected in wildlife, humans and indoor dust and air. Some BFRs have demonstrated endocrine and reproductive effects in animals, but human studies are limited. In this exploratory study, we measured serum hormone levels and flame retardant concentrations [31 polybrominated diphenyl ether (PBDE) congeners and 6 alternate flame retardants] in house dust from men recruited through a US infertility clinic. PBDE congeners in dust were grouped by commercial mixtures (i.e. penta-, octa- and deca-BDE). In multivariable linear regression models adjusted by age and body mass index (BMI), significant positive associations were found between house dust concentrations of pentaBDEs and serum levels of free T4, total T3, estradiol, and sex hormone binding globulin (SHBG), along with an inverse association with follicle stimulating hormone (FSH). There were also positive associations of octaBDE concentrations with serum free T4, thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone and an inverse association of decaBDE concentrations with testosterone. Hexabromocyclododecane (HBCD) was associated with decreased SHBG and increased free androgen index. Dust concentrations of bis-tribromophenoxyethane (BTBPE) and tetrabromo-diethylhexylphthalate (TBPH) were positively associated with total T3. These findings are consistent with our previous report of associations between PBDEs (BDE 47, 99 and 100) in house dust and hormone levels in men, and further suggest that exposure to contaminants in indoor dust may be leading to endocrine disruption in men.

Rodent thyroid, liver, and fetal testis toxicity of the monoester metabolite of bis-(2-ethylhexyl) tetrabromophthalate (tbph), a novel brominated flame retardant present in indoor dust

BACKGROUND

Bis-(2-ethylhexyl) tetrabromophthalate (TBPH) is widely used as a replacement for polybrominated diphenyl ethers (PBDEs) in commercial flame retardant mixtures such as Firemaster 550. It is also used in a commercial mixture called DP 45. Mono-(2-ethyhexyl) tetrabromophthalate (TBMEHP) is a potentially toxic metabolite.

OBJECTIVES

We used in vitro and rodent in vivo models to evaluate human exposure and the potential metabolism and toxicity of TBPH.

METHODS

Dust collected from homes, offices, and cars was measured for TBPH by gas chromatography followed by mass spectrometry. Pregnant rats were gavaged with TBMEHP (200 or 500 mg/kg) or corn oil on gestational days 18 and 19, and dams and fetuses were evaluated histologically for toxicity. We also assessed TBMEHP for deiodinase inhibition using rat liver microsomes and for peroxisome proliferator-activated receptor (PPAR) α and γ activation using murine FAO cells and NIH 3T3 L1 cells.

RESULTS

TBPH concentrations in dust from office buildings (median, 410 ng/g) were higher than in main living areas in homes (median, 150 ng/g). TBPH was metabolized by purified porcine esterases to TBMEHP. Two days of TBMEHP exposure in the rat produced maternal hypothyroidism with markedly decreased serum T3 (3,3´,5-triiodo-l-thyronine), maternal hepatotoxicity, and increased multinucleated germ cells (MNGs) in fetal testes without antiandrogenic effects. In vitro, TBMEHP inhibited deiodinase activity, induced adipocyte differentiation in NIH 3T3 L1 cells, and activated PPARα- and PPARγ-mediated gene transcription in NIH 3T3 L1 cells and FAO cells, respectively.

CONCLUSIONS

TBPH a) is present in dust from indoor environments (implying human exposure) and b) can be metabolized by porcine esterases to TBMEHP, which c) elicited maternal thyrotoxic and hepatotoxic effects and d) induced MNGs in the fetal testes in a rat model. In mouse NIH 3T3 L1 preadipocyte cells, TBMEHP inhibited rat hepatic microsome deiodinase activity and was an agonist for PPARs in murine FAO and NIH 3T3 L1 cells.

Serum and follicular fluid concentrations of polybrominated diphenyl ethers and in-vitro fertilization outcome

There is evidence of endocrine disruption and reproductive effects in animals following exposure to certain PBDEs, but human studies are limited. The goal of this study was to investigate the use of serum and follicular fluid as biomarkers of exposure to PBDEs and to explore whether a relationship between PBDE exposure and early pregnancy loss exists. We measured 8 PBDE congeners in archived serum and ovarian follicular fluid samples from 65 women undergoing in-vitro fertilization (IVF). Logistic regression models were used to predict the odds of failed embryo implantation associated with higher levels of PBDEs among the women in the study. There were moderate Kendall's Tau-beta correlations between serum and follicular fluid concentrations of BDE 28, 47, 100 and 154 (T(β)=0.29-0.38, all p-values<0.005), but BDE 99 and 153 were not correlated between the two matrices (T(β)<0.2, p-values>0.05). Women with detectable concentrations of BDE 153 (39% had detectable levels) in follicular fluid had elevated odds of failed implantation compared with women who had non-detectable concentrations (adjusted OR=10.0; 95%CI: 1.9 to 52; p=0.006; adjusted by age and body mass index). These findings suggest that exposure to BDE 153 may be associated with failed embryo implantation. Due to our observation of only moderate correlations between matrices, serum PBDE concentrations may not be a good indicator of follicular fluid concentrations when studying early pregnancy endpoints in women undergoing IVF.

Polychlorinated biphenyl exposure, diabetes and endogenous hormones: a cross-sectional study in men previously employed at a capacitor manufacturing plant

BACKGROUND

Studies have shown associations of diabetes and endogenous hormones with exposure to a wide variety of organochlorines. We have previously reported positive associations of polychlorinated biphenyls (PCBs) and inverse associations of selected steroid hormones with diabetes in postmenopausal women previously employed in a capacitor manufacturing plant.

METHODS

This paper examines associations of PCBs with diabetes and endogenous hormones in 63 men previously employed at the same plant who in 1996 underwent surveys of their exposure and medical history and collection of bloods and urine for measurements of PCBs, lipids, liver function, hematologic markers and endogenous hormones.

RESULTS

PCB exposure was positively associated with diabetes and age and inversely associated with thyroid stimulating hormone and triiodothyronine-uptake. History of diabetes was significantly related to total PCBs and all PCB functional groupings, but not to quarters worked and job score, after control for potential confounders. None of the exposures were related to insulin resistance (HOMA-IR) in non-diabetic men.

CONCLUSIONS

Associations of PCBs with specific endogenous hormones differ in some respects from previous findings in postmenopausal women employed at the capacitor plant. Results from this study, however, do confirm previous reports relating PCB exposure to diabetes and suggest that these associations are not mediated by measured endogenous hormones.

Thyroid hormone metabolism and environmental chemical exposure

BACKGROUND

Polychlorinated dioxins and -furans (PCDD/Fs) and polychlorinated-biphenyls (PCBs) are environmental toxicants that have been proven to influence thyroid metabolism both in animal studies and in human beings. In recent years polybrominated diphenyl ethers (PBDEs) also have been found to have a negative influence on thyroid hormone metabolism. The lower brominated flame retardants are now banned in the EU, however higher brominated decabromo-diphenyl ether (DBDE) and the brominated flame retardant hexabromocyclododecane (HBCD) are not yet banned. They too can negatively influence thyroid hormone metabolism. An additional brominated flame retardant that is still in use is tetrabromobisphenol-A (TBBPA), which has also been shown to influence thyroid hormone metabolism.Influences of brominated flame retardants, PCDD/F's and dioxin like-PCBs (dl-PCB's) on thyroid hormone metabolism in adolescence in the Netherlands will be presented in this study and determined if there are reasons for concern to human health for these toxins. In the period 1987-1991, a cohort of mother-baby pairs was formed in order to detect abnormalities in relation to dioxin levels in the perinatal period. The study demonstrated that PCDD/Fs were found around the time of birth, suggesting a modulation of the setpoint of thyroid hormone metabolism with a higher 3,3', 5,5'tetrathyroxine (T4) levels and an increased thyroid stimulating hormone (TSH). While the same serum thyroid hormone tests (- TSH and T4) were again normal by 2 years of age and were still normal at 8-12 years, adolescence is a period with extra stress on thyroid hormone metabolism. Therefore we measured serum levels of TSH, T4, 3,3',5- triiodothyronine (T3), free T4 (FT4), antibodies and thyroxine-binding globulin (TBG) in our adolescent cohort.

METHODS

Vena puncture was performed to obtain samples for the measurement of thyroid hormone metabolism related parameters and the current serum dioxin (PCDD/Fs), PCB and PBDE levels.

RESULTS

The current levels of T3 were positively correlated to BDE-99. A positive trend with FT4 and BDE-99 was also seen, while a positive correlation with T3 and dl-PCB was also seen. No correlation with TBG was seen for any of the contaminants. Neither the prenatal nor the current PCDD/F levels showed a relationship with the thyroid parameters in this relatively small group.

CONCLUSION

Once again the thyroid hormone metabolism (an increase in T3) seems to have been influenced by current background levels of common environmental contaminants: dl-PCBs and BDE-99. T3 is a product of target organs and abnormalities might indicate effects on hormone transporters and could cause pathology. While the influence on T3 levels may have been compensated, because the adolescents functioned normal at the time of the study period, it is questionable if this compensation is enough for all organs depending on thyroid hormones.

Assessment of impact of internal exposure to PBDEs on human thyroid function--comparison between congenital hypothyroidism and normal paired blood

In this work, we investigated exposure levels, distribution patterns, and potential harmful impacts of polybrominated diphenyl ethers (PBDEs) on thyroid hormone activity in 26 children with congenital hypothyroidism and their mothers' pair and 12 normal control pairs. The average concentration of PBDEs in congenital hypothyroidism (median: 22.16 ng/g lipid) was higher than in normal controls (median: 14.76 ng/g lipid), but there was no statistical difference between the two groups. The BDE congeners were dominated by penta- to hepta-BDEs, but the greater brominated congeners (e.g., BDE 197, 196, 207, and 208) were relatively abundant in congenital hypothyroidism. BDE 138 was only observed in the congenital hypothyroidism cases. The maternal transfer and transport ratio of individual BDE congeners was shown for BDE 28 (0.588, p < 0.001), BDE 47 (0.564, p < 0.001), BDE 49 (0.712, p < 0.001) and BDE 119 (0.477, p = 0.002). The thyroid hormones were most obviously influenced by the internal exposure to PBDEs in normal mothers, showing a positive relationship with TSH (0.641 with BDE 154; 0.591 with BDE 153) and FT4 (0.584 with BDE 49; 0.572 with BDE 66) and a negative relationship with T3 (-0.577 with BDE 154) in the normal infants group. No significant correlations were observed in the congenital hypothyroidism cases.

Thyroid effects of endocrine disrupting chemicals

In recent years, many studies of thyroid-disrupting effects of environmental chemicals have been published. Of special concern is the exposure of pregnant women and infants, as thyroid disruption of the developing organism may have deleterious effects on neurological outcome. Chemicals may exert thyroid effects through a variety of mechanisms of action, and some animal experiments and in vitro studies have focused on elucidating the mode of action of specific chemical compounds. Long-term human studies on effects of environmental chemicals on thyroid related outcomes such as growth and development are still lacking. The human exposure scenario with life long exposure to a vast mixture of chemicals in low doses and the large physiological variation in thyroid hormone levels between individuals render human studies very difficult. However, there is now reasonably firm evidence that PCBs have thyroid-disrupting effects, and there is emerging evidence that also phthalates, bisphenol A, brominated flame retardants and perfluorinated chemicals may have thyroid disrupting properties.

Serum concentrations of p, p'-DDE, HCB, PCBs and reproductive hormones among men of reproductive age

Exposure to polychlorinated biphenyls (PCBs) has been associated with changes in reproductive hormone levels, however most groups studied have been highly exposed. We investigated the association of PCBs, hexachlorobenzene (HCB) and p, p'-DDE with serum sex hormones in 341 adult men from a US infertility clinic with exposure levels consistent with those observed in the general population. In crude regression models we observed several negative associations of PCBs and HCB with steroid hormone-binding globulin (SHBG) and total and free testosterone. After adjustment for lipids, age and BMI, nearly all significant associations were attenuated. A negative relationship remained between PCB 118 and SHBG (p<0.01), and relationships of dioxin-like PCBs with SHBG and total testosterone, and between PCB 118 and total testosterone, were suggestive. These results suggest a minimal relationship between PCB exposures at low background levels similar to those observed in the general population of the US and circulating reproductive hormones.