Correlation between urinary cadmium and thyroid hormones in outdoor workers exposed to urban stressors

Cadmium Exposure was Associated with Sex-Specific Thyroid Dysfunction: Consistent Evidence from Two Independent Cross-Sectional Studies Based on Urinary and Blood Cadmium Measurements

Population-based studies on the association between cadmium (Cd) exposure and thyroid function are limited and have shown conflicting results. Two independent cross-sectional studies using different Cd biomarkers were carried out in six rural areas with different soil Cd levels in China. Thyroid dysfunction was defined based on levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4). Multivariable linear regression, multiple logistic regression, and restrictive cubic splines models were used to estimate the association between Cd and thyroid dysfunction. For both of the two independent studies, higher Cd levels were observed to be associated with lower TSH levels and higher risk of thyroid dysfunction. The negative relationship between urinary Cd and TSH was found in both total participants (β =  - 0.072, p = 0.008) and males (β =  - 0.119, p = 0.020) but not in females; however, the negative relationship between blood Cd and TSH was only found in females (β =  - 0.104, p = 0.024). Higher urinary Cd was associated with higher risk of thyroid dysfunction (OR = 1.77, p = 0.031), while higher blood Cd was associated with higher risk of thyroid dysfunction (OR = 1.95, p = 0.011). Results from the two independent cross-sectional studies consistently suggested that higher Cd levels were associated with sex-specific thyroid dysfunction.

Cadmium exposure and thyroid hormone disruption: a systematic review and meta-analysis

INTRODUCTION

This meta-analysis aimed to analyze the effect of cadmium (Cd) exposure on thyroid hormone disruption.

CONTENT

Databases including PubMed, Embase, Cochrane Library, and Scopus were searched for studies published up to December 14, 2022. Studies evaluating the association between Cd exposure (blood Cd [BCd] or urine Cd [UCd]) and thyroid function (thyroid-stimulating hormone [TSH], free thyroxine [FT4], total triiodothyronine [TT3]) or thyroid autoimmunity (thyroglobulin antibody [TgAb] or thyroperoxidase Ab [TPOAb]) were included.

SUMMARY AND OUTLOOK

This systematic review included 12 cross-sectional studies. Cd exposure showed a neutral association with TSH (pooled correlation=0.016, 95 % confidence interval [CI]=-0.013 to 0.045, p=0.277), FT4 (pooled correlation=0.028, 95 % CI=-0.005 to 0.061, p=0.098), and thyroid autoimmunity (pooled odds ratio=1.143, 95 % CI=0.820-1.591, p=0.430). However, Cd exposure showed a positive association with TT3 (pooled correlation=0.065, 95 % CI=0.050-0.080, p<0.001), which was consistent with the BCd and UCd subgroup analyses (pooled correlation=0.053 and 0.081, respectively, both p<0.001). Cd exposure was not associated with TSH, FT4, or thyroid autoimmunity but tended to increase with TT3.

Combining computational tools and experimental studies towards endocrine disruptors mitigation: A review of biocatalytic and adsorptive processes

The endocrine disruptors (EDCs) are an important group of emerging contaminants, and their mitigation has been a huge challenge due to their chemistry complexity and variety of these compounds. The traditional treatments are inefficient to completely remove EDCs, and adsorptive processes are the major alternative investigated on their removal. Also, the use of EDCs degrading enzymes has been encouraged due to ecofriendly approach of biocatalytic processes. This paper highlights the occurrence, classification, and toxicity of EDCs with special focus in the use of enzyme-based and adsorptive technologies in the elimination of EDCs from ambiental matrices. Numerous prior reviews have focused on the discussions toward these technologies. However, the literature lacks theoretical discussions about important aspects of these methods such as the mechanisms of EDCs adsorption on the adsorbent surface or the interactions between degrading enzymes - EDCs. In this sense, theoretical calculations combined to experimental studies may help in the development of more efficient technologies to EDCs mitigation. In this review, we point out how computational tools such as molecular docking and molecular dynamics have to contribute to the design of new adsorbents and efficient catalytic processes towards endocrine disruptors mitigation.

Higher cadmium exposure was associated with sex-specific thyroid dysfunction: Consistent evidence from two independent cross-sectional studies based on urinary and blood cadmium measurements

Population-based studies on the association between cadmium (Cd) exposure and thyroid function are limited and have shown conflicting results. Two independent cross-sectional studies using different Cd biomarkers were carried out in six rural areas with different soil Cd levels in China. Thyroid dysfunction was defined based on levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4). Both multivariable linear regression, multiple logistic regression and restrictive cubic splines models were used to estimate the association between Cd and thyroid dysfunction. For both of the two independent studies, higher Cd levels were observed to be associated with lower TSH levels and higher risk of thyroid dysfunction. The negative relationship between urinary Cd and TSH was found in both total participants (β = -0.072, p = 0.008) and males (β = -0.119, p = 0.020) but not in females, however, the negative relationship between blood Cd and TSH was only found in females (β = -0.104, p = 0.024). Higher urinary Cd (> 2.52 μg/g creatinine) was associated with higher risk of thyroid dysfunction, while higher blood Cd was associated with higher risk of hyperthyroidism status. The adjusted Odds Ratio (OR) for the risk of hyperthyroidism status was 3.48 (95%CI:1.36-8.92) and 6.94 (95%CI:1.23-39.31) times higher with every natural log unit higher in blood Cd in total participants and males, respectively. Results from the two independent cross-sectional studies consistently suggested that higher Cd levels were associated with sex-specific thyroid dysfunction.

Endocrine disrupting chemicals: effects on pituitary, thyroid and adrenal glands

BACKGROUND

In recent years, scientific research has increasingly focused on Endocrine Disrupting Chemicals (EDCs) and demonstrated their relevant role in the functional impairment of endocrine glands. This induced regulatory authorities to ban some of these compounds and to carefully investigate others in order to prevent EDCs-related conditions. As a result, we witnessed a growing awareness and interest on this topic.

AIMS

This paper aims to summarize current evidence regarding the detrimental effects of EDCs on pivotal endocrine glands like pituitary, thyroid and adrenal ones. Particularly, we directed our attention on the known and the hypothesized mechanisms of endocrine dysfunction brought by EDCs. We also gave a glimpse on recent findings from pioneering studies that could in the future shed a light on the pathophysiology of well-known, but poorly understood, endocrine diseases like hormone-producing adenomas.

CONCLUSIONS

Although intriguing, studies on endocrine dysfunctions brought by EDCs are challenging, in particular when investigating long-term effects of EDCs on humans. However, undoubtedly, it represents a new intriguing field of science research.

Urinary levels of phthalate esters and heavy metals in adolescents with thyroid colloid cysts

We aimed to evaluate 14 urinary phthalate metabolites and 4 toxic metals in adolescents having thyroid colloid cyst (TCC) and compare with age and sex-matched others without TCC. Phthalate metabolites were analysed with UPLC-MS/MS and heavy metals with ICP-MS. TCC ratios in tertile subgroups of pollutants were compared with multiple logistic regression analysis after adjusting for age, sex, z-scores for body mass index and urinary creatinine values. Adolescents having the highest tertile of mono (2-ethylhexyl) phthalic acid and mercury had increased odds and those with the highest tertiles of monocarboxy-isononyl phthalate, mono (3-carboxypropyl) phthalate, monoisobutyl phthalate had lower odds for TCC than counterparts. The odds of TCC were lower for those in the second and the third tertiles. No differences in TCC ratios were detected with other pollutants. Given phthalate esters' and toxic metals' specific interactions on TCC, further studies were necessary to assess the influence of chemicals on TCC.

Effect of occupational cadmium exposure on the thyroid gland and associated inflammatory markers among workers of the electroplating industry

Cadmium (Cd) is widespread throughout the environment and is used in the electroplating industry. It has been found to have an effect on the endocrine system. However, its effects and their underlying mechanisms are still not clear. The aim of this study was to evaluate how cadmium exposure at work affected the levels of thyroid hormones and the associated inflammatory and oxidative markers. This study was conducted in an electroplating industry in Cairo, Egypt. Ninety male cadmium-exposed workers were matched with 90 male unexposed participants. A detailed questionnaire was designed and given to every participant in the study, and full clinical examinations were carried out. Blood samples were collected from all participants for determination of levels of serum cadmium, thyroid hormones, anti-thyroid peroxidase antibody (anti-TPO), interleukin-6 (IL-6), malondialdehyde (MDA), and tumor necrosis factor-alpha (TNF-α). Morning midstream urine samples were obtained to measure urine cadmium levels. Results showed that the total blood and urinary cadmium levels were significantly higher in the exposed group (2.38 ± 0.94 μg/L and 5.45 ± 1.92 μg/g creatinine, respectively) than in the unexposed group. The serum levels of anti-TPO antibody, TSH, MDA, IL-6, and TNF-α also were significantly higher in the cadmium-exposed group than in the unexposed group. Significant direct relationships were seen between the biological indices of cadmium exposure and anti-TPO antibodies, TSH, IL-6, TNF-α, and MDA. It was concluded that there is a link between occupational cadmium exposure and autoimmune hypothyroidism, inflammatory, and oxidative stress markers.

Thyroid hormones in relation to toxic metal exposure in pregnancy, and potential interactions with iodine and selenium

BACKGROUND

Several endocrine-disrupting metals may affect thyroid function, but the few available studies of exposure during pregnancy and thyroid hormones are inconclusive.

OBJECTIVE

To explore if environmental exposure to cadmium (Cd), lead (Pb), and methylmercury (MeHg) impacts thyroid function in pregnancy, and interacts with iodine and selenium status.

METHODS

Women in a Swedish birth cohort provided blood and urine samples in early third trimester. Concentrations of erythrocyte Cd, Pb, and Hg (n = 544), urinary Cd and iodine (n = 542) and plasma selenium (n = 548) were measured using inductively coupled plasma-mass spectrometry.Free and total thyroxine (fT4, tT4) and triiodothyronine (fT3, tT3), and thyroid stimulating hormone (TSH), were measured in plasma (n = 548) with electrochemiluminescence immunoassays. Metal-hormone associations were assessed in regression models, and metal mixture effects and metal-nutrient interactions were explored in Bayesian kernel machine regression (BKMR).

RESULTS

In multivariable-adjusted regression models, a doubling of urinary Cd was associated with a mean increase in tT4 of 2.7 nmol/L (95% CI: 0.78, 4.6), and in fT3 and tT3 of 0.06 pmol/L (0.02, 0.10) and 0.09 nmol/L (0.05, 0.13), respectively. A doubling of urinary Cd was associated with a -0.002 (-0.003, -0.001) and -0.03 (-0.05, -0.02) decrease in the fT4:tT4 and fT3:tT3 ratio, respectively. A doubling of erythrocyte Hg (>1 µg/kg) was associated with a decrease in fT3 and tT3 by -0.11 pmol/L (-0.16, -0.05) and -0.11 nmol/L (-0.16, -0.06), respectively, and a -0.013 (-0.02, -0.01) decrease in the fT3:fT4 ratio. BKMR did not indicate any mixture effect of toxic metals or interactions between metals and iodine or selenium in relation to the hormones.

CONCLUSION

Our findings suggest that exposure to Cd and Hg, at levels globally prevalent through the diet, may affect thyroid function during pregnancy, independently of iodine and selenium levels. Further studies on potential implications for maternal and child health are warranted.

Associations of exposure to cadmium, antimony, lead and their mixture with gestational thyroid homeostasis

Maintaining thyroid homeostasis during pregnancy is vital for fetal development. The few studies that have investigated associations between metal exposure and gestational thyroid function have yielded mixed findings. To evaluate the association of exposure to a mixture of toxic metals with thyroid parameters in 824 pregnant women from the Rhea birth cohort in Crete, Greece. Concentrations of three toxic metals [cadmium (Cd), antimony (Sb), lead (Pb)] and iodine were measured in urine using inductively coupled plasma mass spectrometry and thyroid hormones [Thyroid Stimulating Hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3)] were measured in serum in early pregnancy. Associations of individual metals with thyroid parameters were assessed using adjusted regression models, while associations of the metal mixture with thyroid parameters were assessed using Bayesian Kernel Machine Regression (BKMR).Women with high (3rd tertile) concentrations of urinary Cd, Sb and Pb, respectively, had 13.3 % (95%CI: 2.0 %, 23.2 %), 12.5 % (95%CI: 1.8 %, 22.0 %) and 16.0 % (95%CI: 5.7 %, 25.2 %) lower TSH compared to women with low concentrations (2nd and 1st tertile). In addition, women with high urinary Cd had 2.2 % (95%CI: 0.0 %, 4.4 %) higher fT4 and 4.0 % (95%CI: -0.1 %, 8.1 %) higher fT3 levels, and women with high urinary Pb had 4 % (95%CI: 0.2 %, 8.0 %) higher fT3 levels compared to women with low exposure. The negative association of Cd with TSH persisted only when iodine sufficiency was unfavorable. BKMR attested that simultaneous exposure to toxic metals was associated with decreased TSH and increased fT3 and revealed a potential synergistic interaction of Cd and Pb in association with TSH. The present results suggest that exposure to toxic metals even at low levels can alter gestational thyroid homeostasis.

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.

Association of exposure to polycyclic aromatic hydrocarbons and heavy metals with thyroid hormones in general adult population and potential mechanisms

Air pollution and fuel emissions are the common sources of human exposure to polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Several studies have suggested potential associations between PAHs/heavy metals and thyroid hormones, however, reports have been inconsistent. In this study, we employed a subpopulation of the adults (n = 1254) who participated in the Korean National Environmental Health Survey 2015-2017, and investigated the association of PAHs and major heavy metals with thyroid hormones, and explored the underlying mechanisms of thyroid disruption. Four PAH metabolites and three heavy metals of lead (Pb), mercury (Hg), and cadmium (Cd) were measured either in urine or in total blood. In addition, thyroid hormones (T3 and T4), TSH, thyroxine-binding globulin (TBG), and thyroid autoantibodies were measured, and peripheral deiodinase activity (G_D) and thyroid's secretory capacity (G_T) were calculated. Urinary Hg was negatively associated with total T3 in both males and females, while it was positively associated with total T4 among females only. Urinary Hg was related to decreased G_D and increased G_T in both sexes. In contrast, urinary Cd was positively associated with total T3 and G_D in both male and female populations. Urinary Cd also showed a positive association with thyroid autoantibodies, but only in males. A multi-factor model considering co-exposure to multiple chemicals also resulted in similar associations. Among the measured PAH metabolites, only urinary 1-hydroxypyrene showed a negative association with total T3 in males. However, this association was marginal, and disappeared in a multi-chemical model. The present observations are suggestive that exposures to Hg and Cd might disrupt thyroid hormones, possibly through an alteration of deiodinase activity. Association of PAH exposure with thyroid hormone appears to be insignificant.

Impaired follicular development and endocrine disorders in female rats by prepubertal exposure to toxic doses of cadmium

Cadmium (Cd) has been associated with several physiological problems including reproductive and endocrine system dysfunction resulting in temporary infertility. The principal objective of this project was to investigate the effects of prepubertal exposure to toxic doses of Cd on puberty onset, the endocrine system, and follicular development. For this purpose, 16 female Sprague-Dawley rats weaned on postnatal day (PND) 21 were randomly divided into 4 groups (n = 4 per group). The treatments were as follows: 0, 25, 50, and 75 mg/kg/day of cadmium chloride (CdCl₂) by oral gavage from PND 21 to observation of first vaginal opening (VO). The results demonstrated that prepubertal exposure to different doses of CdCl₂ delays the age of VO, first diestrus, and first proestrus via altering the concentrations of estradiol and progesterone. The low level of these steroid hormones contributed to lower differentiation and maturation of follicles and it finally led to reduced ovarian reservoir of follicles and impaired follicular development. The number of atretic follicles and secondary follicles with premature cavity increased in rats that received a high dose of CdCl₂, whereas the number of secondary follicles and corpora luteum decreased in the same circumstances. Taken together, these data suggest that prepubertal exposure to toxic doses of Cd delays the onset of puberty via disorderliness in the concentration of steroid hormones and reduces the ovarian reservoir of follicles, as well as folliculogenesis.

Appraisal of Metal Imbalances in the Blood of Thyroid Cancer Patients in Comparison with Healthy Subjects

Cancer incidence and mortality rates have been increasing rapidly worldwide. A growing body of evidence revealed that exposure to trace metals is the most important aetiology for development of the cancer. Therefore, present study was intended to evaluate the imbalances in the concentrations of selected metals (Na, K, Ca, Mg, Sr, Li, Fe, Zn, Cu, Co, Mn, Ag, Cd, Cr, Ni and Pb) in the blood of newly diagnosed thyroid cancer patients in comparison with counterpart healthy subjects/controls. Concentrations of the metals were quantified by flame atomic absorption spectrometry by employing nitric acid/perchloric acid-based wet digestion method. Average concentrations of Pb (774.6 μg/dL), Cr (757.9 μg/dL), Cd (472.5 μg/dL) and Ni (360.5 μg/dL) were found to be significantly higher in the blood of cancer patients than controls. Correlation study and multivariate analysis showed strong mutual relationships among Fe-Cd-Ca-Mg-Pb, Co-Sr-Zn, Li-Ag-Na-K and Cu-Ni in the blood of thyroid cancer patients while Na-K-Fe-Co-Pb, Zn-Sr-Cr, Ca-Mg and Li-Ag-Cu-Ni exhibited strong mutual associations in the blood of healthy donors. Significant variations in the trace metal levels were observed with the age, gender, habitat, food habits and smoking habits of both donor groups. Metal levels also exhibited considerable disparities with the stages and types of thyroid cancer. Multivariate analysis of the metal data revealed significantly divergent apportionment of the metals in the blood of cancer patients compared with the healthy group.

An assessment of sensitivity biomarkers for urinary cadmium burden

BACKGROUND

Excess cadmium (Cd) intake poses a general risk to health and to the kidneys in particular. Among indices of renal dysfunction under Cd burden measures are the urinary N-acetyl-β-D-glucosidase (UNAG) and urinary β2-microglobulin (Uβ2-MG) enzymes. However, the end-pointed values and the Cd burden threshold remain controversial because the scopes fluctuate widely.

METHODS

To ascertain the clinical benchmark dose of urinary Cd (UCd) burden for renal dysfunction, 1595 residents near a Cd site were surveyed. Urine was sampled and assayed. A benchmark dose low (BMDL) was obtained by fitting UCd levels and index levels.

RESULTS

We found that over 50% of the subjects were suffering from Cd exposure as their UCd levels far exceeded the national standard threshold of 5.000 μg/g creatinine (cr). Further analysis indicated that Uβ2-MG was more sensitive than UNAG for renal dysfunction. The BMDL for UCd was estimated as 3.486 U/g cr (male, where U is unit of enzyme) and 2.998 U/g cr (female) for UNAG. The BMDL for Uβ2-MG, which is released into urine from glomerulus after Cd exposure, was found to be 2.506 μg/g cr (male, where μg is the unit of microglobulin) and 2.236 μg/g cr (female).

CONCLUSIONS

Uβ2-MG is recommended as the sensitivity index for renal dysfunction, with 2.2 μg/g cr as the threshold for clinical diagnosis. Our findings suggest that Uβ2-MG is the better biomarker for exposure to Cd.

Identifying a critical window of maternal metal exposure for maternal and neonatal thyroid function in China: A cohort study

BACKGROUND

China, a developing country, has a particularly serious problem with metal pollution. We evaluated the association of metal exposure during pregnancy with maternal and neonatal thyroid function, and identified the critical window for maternal metal exposure effects on maternal and neonatal thyroid functions.

METHODS

The maternal urinary concentrations of mercury (Hg), cadmium (Cd), arsenic (As) and cesium (Cs) were determined in pregnant women during their first (n = 389) or third (n = 257) trimesters in a prospective cohort from 2014 to 2015 in Nanjing, China, using an inductively coupled plasma mass spectrometry (ICP-MS) instrument. Maternal serum-free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were measured by electrochemiluminescent microparticle immunoassays in the second and third trimesters. Neonatal TSH levels were detected 72 h after birth.

RESULTS

Hg (>0.162 µg/L), Cd (>0.084 µg/L), As (>0.348 µg/L) and Cs (>0.093 µg/L) were detectable in 76.9%, 90.1%, 100% and 100% of maternal urine samples from women in the first trimester of pregnancy. In the multiple adjusted linear regression models, maternal exposures to Hg and Cd in the first trimester were positively associated with maternal TSH levels in the second trimester (P < 0.01, P = 0.02). Moreover, maternal exposures to Cd and Cs in the first trimester were positively associated with neonatal TSH levels (P = 0.04, P = 0.02). In the Bayesian kernel machine regression (BKMR) model, the results were stable and consistent with the linear regression model.

CONCLUSIONS

Maternal exposure to Hg, Cd and Cs in the first trimester was related to TSH levels in mothers and newborns. Efforts to identify maternal and neonatal thyroid disruptors should carefully consider the effects of exposure to these metals.

Sex-specific effects of blood cadmium on thyroid hormones and thyroid function status: Korean nationwide cross-sectional study

Previous studies on blood cadmium (BCd) and changes in thyroid hormone levels are controversial. We investigated whether thyroid hormone levels and thyroid function status were associated with BCd according to sex in the Korean population. Our study included 1972 participants based on the 2013 Korea National Health and Nutrition Examination Survey (KNHANES) data. Participants whose thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels were altered physiologically or medically were excluded. Changes in TSH, fT4, and anti-thyroid peroxidase antibody (TPOAb) in men and women were analyzed by different characteristics: age, body mass index (BMI), smoking status, drinking status, BCd, and urine iodine-to-creatinine ratio (UI/Cre). Thyroid function status was classified as hypothyroidism, euthyroidism, and hyperthyroidism as defined by TSH and fT4 levels. Among the total participants, there was a negative correlation between BCd and fT4 (r=-0.067, p = 0.003). In men (n = 1057), fT4 levels decreased with increasing BCd quartile (p-for-trend = 0.002). After adjustment for age, BMI, smoking status, UI/Cre, and TPOAb, the association between BCd and hypothyroidism was significant in men (odds ratio = 1.813, p = 0.032) but not in women. These results suggest that cadmium accumulation is closely associated with thyroid dysfunction, and there is a difference in metabolic capacity according to sex.

Occupational exposure to pesticides and thyroid function in Brazilian soybean farmers

INTRODUCTION

Agriculture production has been supported especially by the use of pesticides for crop protection and pest control. Although the agricultural production has been increased by pesticides use, these substances also reach non-target organisms and may become a risk to the health of farmers. Several epidemiological studies in human have investigated the association between exposure to pesticides and altered serum levels of thyroid hormones, reporting both positive and negative results. Overall, the impact of pesticides on human thyroid function is still limited.

OBJECTIVE

The aim of this study was to access serum levels of free thyroxin (FT4), total triiodothyronine (TT3), thyroid-stimulating hormone (TSH), and butyrylcholinesterase (BChE) in soybean farmers in southern Brazil.

METHODS

The exposed group was composed by 46 rural workers and 27 subjects not exposed to pesticides composed the control group. All subjects had blood samples collected by venipuncture in order to analyze the serum levels of FT4, TT3, TSH and BChE.

RESULTS

The results showed a significant decreasing in TSH and increasing in TT3 and FT4 in rural workers, compared to control group. BChE levels were lower in exposed group than in control group. The results suggest that farmers are exposed to mixtures of pesticides with endocrine disruptor properties.

Associations of blood metal exposure with thyroid hormones in Chinese pregnant women: A cross-sectional study

BACKGROUND

Few epidemiological studies have investigated associations of exposure to multiple metals with thyroid hormone homeostasis, especially for the pregnant women.

METHODS

Among all the 1644 participants enrolled in Hangzhou Birth Cohort Study (HBCS) at baseline, a total of 915 pregnant women with complete data of interest were analyzed. Eleven metals were measured in blood samples collected around 25 weeks gestation. Serum levels of thyroid hormones including free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), total thyroxine (TT4) and thyroid-stimulating hormone (TSH) were abstracted from the medical records. Relationships between tertiles of metal levels (setting the lowest tertile as the reference) and percent changes in thyroid hormones were estimated by multivariable adjusted linear regression models.

RESULTS

Five metals [arsenic (As), selenium (Se), manganese (Mn), nickel (Ni), antimony (Sb)] were significantly linked to decreased levels of one or more thyroid hormones based on trend tests in the single-metal models. Percent changes [95% confidence intervals (CIs)] in thyroid hormones for the third tertiles of metals remained significant between FT3 and As [-3.53% (-5.48%, -1.54%)]; and between TT3 and As [-4.19% (-7.00%, -1.31%)]; and between FT4 and Mn [-2.05% (-3.49%, -0.58%)], Sb [-1.99% (-3.44%, -0.52%)] in the multiple-metal models.

CONCLUSIONS

Thyroid hormone concentrations were reversely related to the levels of blood metals of As, Mn and Sb among Chinese pregnant women. Additional prospective studies are warranted to confirm the causality. Paper capsule: Exposure to multiple metals was reversely associated with one or more thyroid hormones in the Chinese pregnant women.

Overview of Cadmium Thyroid Disrupting Effects and Mechanisms

Humans are exposed to a significant number of chemicals that are suspected to produce disturbances in hormone homeostasis. Hence, in recent decades, there has been a growing interest in endocrine disruptive chemicals. One of the alleged thyroid disrupting substances is cadmium (Cd), a ubiquitous toxic metal shown to act as a thyroid disruptor and carcinogen in both animals and humans. Multiple PubMed searches with core keywords were performed to identify and evaluate appropriate studies which revealed literature suggesting evidence for the link between exposure to Cd and histological and metabolic changes in the thyroid gland. Furthermore, Cd influence on thyroid homeostasis at the peripheral level has also been hypothesized. Both in vivo and in vitro studies revealed that a Cd exposure at environmentally relevant concentrations results in biphasic Cd dose-thyroid response relationships. Development of thyroid tumors following exposure to Cd has been studied mainly using in vitro methodologies. In the thyroid, Cd has been shown to activate or stimulate the activity of various factors, leading to increased cell proliferation and a reduction in normal apoptotic activity. Evidence establishing the association between Cd and thyroid disruption remains ambiguous, with further studies needed to elucidate the issue and improve our understanding of Cd-mediated effects on the thyroid gland.

Health Risks to Ecological Workers on Contaminated Sites - the Department of Energy as a Case Study

BACKGROUND

At most contaminated sites the risk to workers focuses on those 'hazardous waste workers' directly exposed to chemicals or radionuclides, and to the elaborate approaches implemented to protecting their health and safety. Ecological workers generally are not considered.

OBJECTIVES

To explore the risks to the health and safety of ecological workers on sites with potential chemical and radiological exposures before, during or after remediation of contamination. To use the U.S. Department of Energy as a case study, and to develop concepts that apply generally to sites contaminated with hazardous or nuclear wastes.

METHODS

Develop categories of ecological workers, describe their usual jobs, and provide information on the kinds of risks they face. Ecological activities include continued surveillance and monitoring work on any sites with residual contamination, subject to institutional controls and engineered barriers following closure as well as the restoration.

RESULTS

The categories of ecological workers and their tasks include 1) Ecological characterization, mapping and monitoring, 2) biodiversity studies, 2) Contaminant fate and transport, 3) On-going industrial activities 4) Remediation activities (environmental management), 5) Environmental restoration, 6) Post-cleanup surveillance and monitoring, and 7) Post-closure future site activities. There are a set of functional activities that can occur with different frequencies and intensities, including visual inspection, collecting biological samples, collecting media physical samples, collecting biological debris, restoration planting, and maintaining ecosystems.

CONCLUSIONS

Ecological workers face different exposures and risks than other environmental cleanup workers. Many of their tasks mimic shift work with long hours leading to fatigue, and they are exposed to biological as well as chemical/radiological hazards. DOE and other entities need to examine the risks to ecological workers on site with an eye to risk reduction.