Human exposure to heavy metals and related cancer development: a bibliometric analysis

As notifications on carcinogenicity of heavy metals increase, more and more attention is paid recently to heavy metals exposure. In our study, the human exposure to heavy metals and cancer knowledge epistemology was investigated using bibliometric analysis. The bibliometric data of the research articles were retrieved using following keywords: "heavy metal," "trace element", "cancer", "carcinogen", and "tumor" in the Scopus database. Specifically, 2118 articles published between 1972 and 2023 were found, covering a total of 1473 authors, 252 sources, and 2797 keywords. Retrospective data obtained from 251 documents and 145 journals were further analyzed by performance analysis and techniques of science mapping. The number of studies conducted in this field increased from one article published in 1972 to 18 articles published in 2022 in the study of Michael P Waalkes. The most impactful author regarding the number of published papers was Masoudreza Sohrabi with 7 publications. In the majority of the published papers, the most popular keywords were "cadmium" and "carcinogenicity". However, in recent 4 years, the emphasis has been placed more on epidemiology studies. Our study provides general knowledge about the trend of publication on the role of heavy metals in causing cancer. The leading researchers in the field of the effects of heavy metals on the development of cancer were identified in our studies. Our results might also create a better understanding of new and emerging issues and can be used as a comprehensive road map for future researchers.

Morin mitigates cadmium-induced testicular impairment by stimulating testosterone secretion and germ cell proliferation in mice

Cadmium (Cd) is one of the heavy metal pollutants present in the environment due to human intervention. It is well known that Cd causes toxicological effects on various organs, including the testes. Morin hydrate is a plant-derived bioflavonoid with antioxidant, anti-inflammatory, and anti-stress properties. Thus, the question can be raised as to whether Morin has an effect on Cd-intoxication-induced testicular impairment. Therefore, the aim of this study was to investigate the role of Morin on Cd-mediated disruption of testicular activity. Mice were divided into three groups: group 1 served as the control group, group 2 was given Cd (10 mg/kg) orally for 35 days, and group 3 was given Cd and Morin hydrate (100 mg/kg) for 35 days. To validate the in vivo findings, an in vitro study on testicular explants was also performed. The results of the in vivo study showed that Cd-intoxicated mice had testicular disorganization, reduced circulating testosterone levels, decreased sperm density, and elevated oxidative stress and sperm abnormality. The expression of the germ cell proliferation marker, germ cell nuclear acidic protein (GCNA), and adipocytokine visfatin were also downregulated. It was observed that Morin hydrate upregulated testicular visfatin and GCNA expression in Cd-intoxicated mice, along with improvement in circulating testosterone, testicular histology, and sperm parameters. Furthermore, the in vitro study showed that Cd-mediated downregulation of testicular visfatin and GCNA expression, along with the suppressed secretion of testosterone from testicular explants, was normalized by Morin treatment, whereas visfatin expression was not. Overall, these data indicate that environmental cadmium exposure impairs testicular activity through downregulation of visfatin and GCNA expression, and Morin might play a protective role against Cd-induced testicular toxicity.

Spatial patterns and the associated factors for breast cancer hospitalization in the rural population of Fujian Province, China

BACKGROUND

Despite the known increasing incidence of breast cancer in China, evidence on the spatial pattern of hospitalization for breast cancer is scarce. This study aimed to describe the disparity of breast cancer hospitalization in the rural population of Southeast China and to explore the impacts of socioeconomic factors and heavy metal pollution in soil.

METHODS

This study was conducted using the New Rural Cooperative Medical Scheme (NRCMS) claims data covering 20.9 million rural residents from 73 counties in Southeast China during 2015-2016. The associations between breast cancer hospitalization and socioeconomic factors and soil heavy metal pollutants were evaluated with quasi-Poisson regression models and geographically weighted Poisson regressions (GWPR).

RESULTS

The annual hospitalization rate for breast cancer was 101.40/100,000 in the studied area and the rate varied across different counties. Overall, hospitalization for breast cancer was associated with road density (β = 0.43, P = 0.02), urbanization (β = 0.02, P = 0.002) and soil cadmium (Cd) pollution (β = 0.01, P = 0.02). In the GWPR model, a stronger spatial association of Cd, road density and breast cancer hospitalization was found in the northeast regions of the study area while breast cancer hospitalization was mainly related to urbanization in the western regions.

CONCLUSIONS

Soil Cd pollution, road density, and urbanization were associated with breast cancer hospitalization in different regions. Findings in this study might provide valuable information for healthcare policies and intervention strategies for breast cancer.

Endocrine-disrupting chemicals (EDCs) and cancer: new perspectives on an old relationship

PURPOSE

Environmental endocrine-disrupting chemicals (EDCs) are a mixture of chemical compounds capable to interfere with endocrine axis at different levels and to which population is daily exposed. This paper aims to review the relationship between EDCs and breast, prostate, testicle, ovary, and thyroid cancer, discussing carcinogenic activity of known EDCs, while evaluating the impact on public health.

METHODS

A literature review regarding EDCs and cancer was carried out with particular interest on meta-analysis and human studies.

RESULTS

The definition of EDCs has been changed through years, and currently there are no common criteria to test new chemicals to clarify their possible carcinogenic activity. Moreover, it is difficult to assess the full impact of human exposure to EDCs because adverse effects develop latently and manifest at different ages, even if preclinical and clinical evidence suggest that developing fetus and neonates are most vulnerable to endocrine disruption.

CONCLUSION

EDCs represent a major environmental and health issue that has a role in cancer development. There are currently some EDCs that can be considered as carcinogenic, like dioxin and cadmium for breast and thyroid cancer; arsenic, asbestos, and dioxin for prostate cancer; and organochlorines/organohalogens for testicular cancer. New evidence supports the role of other EDCs as possible carcinogenic and pregnant women should avoid risk area and exposure. The relationship between EDCs and cancer supports the need for effective prevention policies increasing public awareness.

The impact of endocrine disrupting compounds and carcinogens in wastewater: Implications for breast cancer

The incidence of breast cancer is often associated with geographic variation which indicates that a person's surrounding environment can be an important etiological factor in cancer development. Environmental risk factors can include exposure to sewage- or wastewater, which consist of a complex mixture of pathogens, mutagens and carcinogens. Wastewater contains primarily carbonaceous, nitrogenous and phosphorus compounds, however it can also contain trace amounts of chemical pollutants including toxic metal cations, hydrocarbons and pesticides. More importantly, the contamination of drinking water by wastewater is a potential source of exposure to mammary carcinogens and endocrine disrupting compounds. Organic solvents and other pollutants often found in wastewater have been detected in various tissues, including breast and adipose tissues. Furthermore, these pollutants such as phenolic compounds in some detergents and plastics, as well as parabens and pesticides can mimic estrogen. High estrogen levels are a well-established risk factor for estrogen-receptor (ER) positive breast cancer. Therefore, exposure to wastewater is a risk factor for the initiation, progression and metastasis of breast cancer. Carcinogens present in wastewater can promote tumourigenesis through various mechanisms, including the formation of DNA adducts, gene mutations and oxidative stress. Lastly, the presence of endocrine disrupting compounds in wastewater can have negative implications for ER-positive breast cancers, where these molecules can activate ERα to promote cell proliferation, survival and metastasis. As such, strategies should be implemented to limit exposure, such as providing funding into treatment technologies and implementation of regulations that limit the production and use of these potentially harmful chemicals.

Is Cadmium a Risk Factor for Breast Cancer - Results from a Nested Case-Control Study Using Data from the Malmö Diet and Cancer Study

BACKGROUND

Some studies have shown that cadmium (Cd) is associated with breast cancer risk. One hypothesis is that Cd has estrogen-like properties. This case-control study investigated the association between breast cancer risk and blood Cd (BCd) levels.

METHODS

All breast cancers in the Malmö Diet and Cancer cohort were identified through linkage to the Swedish Cancer Registry, baseline (1991-1996) through 2014. Two controls per case were selected from the same cohort. BCd was analyzed at baseline. Associations were analyzed using logistic regression.

RESULTS

Mean BCd was 0.51 μg/L among 1,274 cases and 0.46 among 2,572 controls. There was an overall increased risk of breast cancer [OR, 1.18; 95% confidence interval (CI), 1.05-1.36] per μg/L of BCd. An increased risk was, however, only found at high BCd [OR, 1.34 (95% CI, 1.05-1.73)] for BCd more than 1.20 μg/L. The group with the highest BCd was mainly smokers. A spline indicated that at BCd less than 1.0 μg/L, the OR was not increased. The association with BCd was stronger in current smokers and at body mass index (BMI) above 25, while no modification due to receptor status was found.

CONCLUSIONS

The results indicated increased risk of breast cancer only for high Cd exposure, which occurred mainly among smokers. This made it difficult to disentangle the effects of smoking and Cd, despite inclusion of smoking habits in the models.

IMPACT

This study provides support for reducing Cd exposure through smoking cessation and dietary choice. On the population level, preventive measures against Cd pollution are warranted.

Aetiological analysis and diagnosis of reproductive disorders in male dromedary camels

The purpose of this paper was to analyse the aetiology and methods of diagnosing reproductive disorders in male dromedary camels. Male camel infertility manifests as one of three conditions: post-coital infertility (IG), inability to copulate (IC) and lack of sexual desire (LSD). IG is mainly a testicular disorder that is linked to a deteriorated seminogram, arrested spermatogenesis, Sertoli cell-only syndrome and testicular degeneration. For IG diagnosis, semen analysis, testicular biopsy and fine-needle aspiration are gold standards. Testicular ultrasonography was generally inefficient. High serum FSH was found in IG camels with oligo- and azoospermia, implying primary spermatogenesis defects. The testis-expressed protein (TEX101) and the epididymis-expressed protein (ECM1) are reliable biomarkers for distinguishing between obstructive and non-obstructive azoospermia. IC manifests in two forms: phimosis (PHI) and erectile dysfunction (ED). PHI is frequently linked to preputial and penile pathologies, as well as leucocytosis, neutrophilia and elevated nitric oxide metabolites. The majority of camels with ED have normal genital organs, and the condition is associated with an increase in cardiac troponin I. LSD is a rare disorder brought on by hormonal imbalances, high temperatures, stress and debilitating diseases. In conclusion, IG diagnosis necessitates semen analysis, testicular biopsy or fine-needle aspiration, and FSH testing, whereas IC diagnosis requires preputial and penile examinations. Diagnostic aids include serum and seminal biomarkers.

Cadmium exposure and risk of breast cancer: A dose-response meta-analysis of cohort studies

BACKGROUND

Cadmium is a toxic heavy metal that has been implicated in breast cancer etiology, albeit with inconsistent results.

OBJECTIVE

To investigate the shape of the relation between cadmium exposure and breast cancer incidence and mortality in cohort studies.

DATA SOURCES

Following a literature search through April 14, 2020, we carried out a systematic review and dose-response meta-analysis to investigate the shape of the relation between cadmium exposure (assessed either through diet or urine excretion) and disease incidence and mortality.

STUDY ELIGIBILITY CRITERIA

For inclusion, a study had to report incidence or mortality for breast cancer according to baseline cadmium exposure category; be a prospective cohort, case-cohort or nested case-control study with a minimum one-year follow-up, and reporting effect estimates for all exposure categories.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies were evaluated using the ROBINS-E risk of bias tool. The effects in humans were assessed quantitatively using one-stage dose-response meta-analysis in a random effects meta-analytical model.

RESULTS

We identified 10 studies eligible for inclusion in the dose-response meta-analysis, six based on cadmium dietary intake, and four on urinary excretion levels. We found a marginal and imprecise positive relation between dietary cadmium intake and breast cancer, and no association when urinary cadmium excretion was used for exposure assessment. Compared to no exposure, at 20 µg/day of cadmium intake the summary risk ratio was 1.12 (95% confidence interval 0.80-1.56), while at 2 µg/g creatinine of cadmium excretion the summary risk ratio was 0.89 (95% confidence interval 0.38-2.14). Analysis restricted to post-menopausal women showed no association between either dietary or urinary cadmium and subsequent breast cancer incidence and mortality.

LIMITATIONS AND CONCLUSIONS

Overall, we found scant evidence of a positive association between cadmium and breast cancer. Available data were too limited to carry out stratified analyses according to age, smoking and hormone receptor status. Therefore, possible associations between cadmium exposure and breast cancer in selected subgroups cannot be entirely ruled out.

Emerging Links between Cadmium Exposure and Insulin Resistance: Human, Animal, and Cell Study Data

Recent research has helped clarify the role of cadmium (Cd) in various pathological states. We have demonstrated Cd involvement in pancreatic cancer, as well as the bioaccumulation of Cd in the pancreas. Bioaccumulation and increased toxicity suggest that Cd may also be involved in other pancreas-mediated diseases, like diabetes. Cd falls into the category of "hyperglycemic" metals, i.e., metals that increase blood glucose levels, which could be due to increased gluconeogenesis, damage to β-cells leading to reduced insulin production, or insulin resistance at target tissue resulting in a lack of glucose uptake. This review addresses the current evidence for the role of Cd, leading to insulin resistance from human, animal, and in vitro studies. Available data have shown that Cd may affect normal insulin function through multiple pathways. There is evidence that Cd exposure results in the perturbation of the enzymes and modulatory proteins involved in insulin signal transduction at the target tissue and mutations of the insulin receptor. Cd, through well-described mechanisms of oxidative stress, inflammation, and mitochondrial damage, may also alter insulin production in β-cells. More work is necessary to elucidate the mechanisms associated with Cd-mediated insulin resistance.

Association between Blood Heavy Metal Levels and Predicted 10-Year Risk for A First Atherosclerosis Cardiovascular Disease in the General Korean Population

Background: Atherosclerotic cardiovascular disease (ASCVD) is a preventable type of disease, thus, specifying factors that increase the occurrence of this type of disease is needed. Heavy metals such as cadmium (Cd), lead (Pb), and mercury (Hg) have been suggested as possible factors influencing the development of cardiovascular disease. We aimed to link blood heavy metal levels (Cd, Pb, Hg) with 10-year ASCVD risk scores. Methods: A population of 993 men and 1431 women who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) were included. The 2013 American College of Cardiology/American Heart Association (ACC/AHA) pooled cohort equations risk prediction model and Korean Risk Prediction Model (KRPM) were used as means for risk prediction. Following multivariate adjustment; blood Cd; Pb; and Hg levels were divided into quartiles for analysis using linear trends estimation and multiple regression models. Results: There was an overall positive trend between blood Cd, Pb, and Hg levels and 10-year ASCVD risk scores; KRPM risk score increasing by quartile for blood Cd (men p < 0.0001, women p = 0.0024), Pb (men p = 0.0097, women p = 0.0330), Hg (men p = 0.0096, women p = 0.0030) rates and pooled cohort equations risk score increasing by quartile for Cd (men p < 0.0001, women p = 0.0034) and Hg (men p = 0.0099, women p = 0.0010) with linear trends. Urban population showed a stronger relationship between blood Cd, Pb, and Hg levels and 10-year ASCVD risk score especially among men with multiple regression analysis. Conclusion: Blood Cd, Pb, and Hg levels are associated with ASCVD risk. Thus, they should be considered while developing preventive measures for ASCVD.

Levels and distribution of polybrominated diphenyl ethers in humans and environmental compartments: a comprehensive review of the last five years of research

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs), present in the environment, animals, and humans. Their levels, distribution, and human exposure have been studied extensively, and over the last decade, various legal measures have been taken to prohibit or minimize their production and use due to the increasing amount of evidence of their harmful effects on human and animal health.Our aim here was to make a comprehensive and up-to-date review of the levels and distribution of PBDEs in the aquatic environment, air, and soil, in indoor dust, and in humans. To fulfill this, we searched through Web of Science for literature data reported in the last five years (2015-2019) on levels of at least six key PBDE congeners in abovementioned matrices. According to our summarized data, significant PBDE mass concentrations/fractions are still being detected in various sample types across the world, which implies that PBDE contamination is an ongoing problem. Secondary sources of PBDEs like contaminated soils and landfills, especially those with electronic and electrical waste (e-waste), represent a particular risk to the future and therefore require a special attention of scientists.

Cadmium in Seminal Plasma of Fertile and Infertile Male Dromedary Camels

The objective of this study was to investigate the cadmium (Cd) profile in seminal plasma of male dromedary camel with impotentia generandi (post-coital infertility, IG group, n = 14) in comparison with known fertile males (FERT group, n = 5). Andrological examination was carried out for all animals. Semen was collected with electroejaculation and examined for volume, concentration, motility, viability, and abnormality. Seminal fluid was harvested after centrifugation and analyzed for Cd using atomic absorption spectrophotometer. Results showed that sperm concentration, motility, and viability were higher, while sperm abnormality was lower in IG group than in FERT group (P < 0.05). Cd was higher in seminal plasma of IG group than in FERT group (P = 0.04). Negative correlation was found between Cd concentration and sperm concentration (r = - 0.511, P = 0.04). There was also a tendency for negative correlation between Cd concentration and the testicular size (r = - 0.455, P = 0.05). In conclusion, Cd may be one of factors causing infertility in male dromedary camels.

Diallyl disulfide attenuation effect on transcriptome in rat liver cells against cadmium chloride toxicity

In this report, liver cells were treated with cadmium chloride (CdCl₂ ) and diallyl disulfide (DADS), a major compound from garlic to attenuate the toxic effect of Cd on transcriptome. The viability of Cd treated cells was reduced to 19.9% ± 2.4% in comparison to the untreated cells, whereas the viability of DADS pretreated cells was increased to 48.6% ± 2%. The attenuation effect of DADS was studied at shorter period (6 hours). Transcriptome analysis of CdCl₂ alone treated cells resulted in 2119 and 982 (up and down) regulated genes (≥ 2 or ≤ 2-fold), whereas pretreated cells with DADS resulted in 2597 and 1784 genes. These genes were known to function in many important biological processes. Affymetrix array analysis was validated by the pathway specific PCR array that exhibited the same trend of expression. The current study clearly shows the DADS attenuation effect on transcriptome in CdCl₂ -treated rat liver cells.

Mechanism of cadmium poisoning on testicular injury in mice

Cadmium is a heavy metal that is toxic to humans and the reproductive system. The present study aimed to investigate the mechanisms of cadmium-induced reproductive toxicity in a male Institute of Cancer Research mouse model of cadmium poisoning. Changes in luteinizing hormone receptor (LHR), 17α-hydroxylase and endothelial nitric oxide (NO) synthase (eNOS) expression levels were examined. A total of 24 male mice (4-week-old) were randomly divided into four groups (normal control group and low, medium and high cadmium groups) and subjected to gavage treatment with normal saline or cadmium-containing saline solutions for 8 weeks prior to sacrifice. To assess testicular injury, serum androgen levels were determined by ELISA, testicular tissue pathological changes were evaluated using hematoxylin and eosin staining. In addition, LHR, 17α-hydroxylase and eNOS expressions levels were examined by western blotting, and apoptosis was examined with a terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The results demonstrated that the severity of testes injury increased with cadmium concentration. In addition, LHR, 17α-hydroxylase and eNOS expression levels increased with low and medium concentrations of cadmium; however, they were decreased following treatment with high concentrations of cadmium. The results from the present study demonstrated that cadmium altered LHR, 17α-hydroxylase and eNOS expression levels in testicular stromal cells, which may impact testosterone synthesis. Furthermore, NO was suggested to be involved in cadmium-induced testicular injury by measurements of eNOS expression in testicular stromal cells.

Impotentia generandi in male dromedary camels: heavy metal and trace element profiles and their relations to clinical findings and semen quality

The aim of this study was to investigate the profiles of cadmium (Cd), lead (Pb), selenium (Se), zinc (Zn), copper (Cu), molybdenum (Mo), iron (Fe), and manganese (Mn) in serum of dromedary camels with impotentia generandi and their associations with the clinical findings and semen analysis data. Sixteen male dromedary camels with impotentia generandi (IG group) and 5 fertile camels (FERT group) were used. The external and internal genital organs were examined using visual inspection, palpation, and ultrasonography. Semen was collected by electroejaculation and examined for volume, count, motility, viability, and abnormality. Blood was collected from all camels and serum was harvested. All serum samples were digested by concentrated acids and analyzed for heavy metals and trace elements by flame emission atomic absorption spectrophotometer. Results showed that the mean heavy metal and trace element concentrations in serum were in the following descending order Fe > Zn > Cu > Cd > Mo > Se > Mn > Pb. Cd was higher in IG than in FERT males (P = 0.02). Se was greater in FERT than in IG groups (P = 0.003). Zn was higher in in FERT than in IG groups (P = 0.001). There were positive correlations between Zn and sperm count (r = 0.59, P = 0.005) and sperm motility (r = 0.57, P = 0.005) and a tendency for negative correlation between Zn and sperm abnormalities (r = - 0.44, P = 0.05). In conclusion, Cd might be implicated as a cause of infertility in male camels. Deficiencies of Se and Zn may also have adverse impacts on male camel reproduction.

Review of polyphenol-rich products as potential protective and therapeutic factors against cadmium hepatotoxicity

Recently, the growing attention of the scientific community has been focused on the threat to health created by environmental pollutants, including toxic metals such as cadmium (Cd), and on the need of finding effective ways to prevent and treat the unfavorable health effects of exposure to them. Particularly promising for Cd, and thus arousing the greatest interest, is the possibility of using various ingredients present in plants, including mainly polyphenolic compounds. As the liver is one of the target organs for this toxic metal and disturbances in the proper functioning of this organ have serious consequences for health, the aim of the present review was to discuss the possibility of using polyphenol-rich food products (e.g., chokeberry, black and green tea, blueberry, olive oil, rosemary and ginger) as the strategy in protection from this xenobiotic hepatotoxicity and treatment of this heavy metal-induced liver damage. Owing to the ability of polyphenols to bind ions of Cd and the strong antioxidative potential of these compounds, as well as their abundance in dietary products, it seems to be of high importance to consider the possibility of using polyphenols as potential preventive and therapeutic agents against Cd hepatotoxicity, determined by its strong pro-oxidative properties. Although most of the data on the effectiveness of polyphenols comes from studies in animals, the fact that some of them are derived from experimental models that reflect human exposure to this metal allows us to assume that some polyphenol-rich food products may be promising protective agents against Cd hepatotoxicity in humans.

Transcriptome assembly and expression profiling of the molecular responses to cadmium toxicity in cerebral ganglia of wolf spider Pardosa pseudoannulata (Araneae: Lycosidae)

Cadmium (Cd) is a heavy metal that can cause irreversible toxicity to animals, and is an environmental pollutant in farmlands. Spiders are considered to be an excellent model for investigating the impacts of heavy metals on the environment. To date, the changes at the molecular level in the cerebral ganglia of spiders are poorly understood. Cd exposure leads to strong damage in the nervous system, such as apoptosis and necrosis of nerve cells, therefore we conducted a transcriptomic analysis of Pardosa pseudoannulata cerebral ganglia under Cd stress to profile differential gene expression (DGE). We obtained a total of 123,328 assembled unigenes, and 1441 Cd stress-associated DEGs between the Cd-treated and control groups. Expression profile analysis demonstrated that many genes involved in calcium signaling, cGMP-PKG signaling, tyrosine metabolism, phototransduction-fly, melanogenesis and isoquinoline alkaloid biosynthesis were up-regulated under Cd stress, whereas oxidative phosphorylation-related, nervous disease-associated, non-alcoholic fatty liver disease-associated, and ribosomal-associated genes were down-regulated. Here, we provide a comprehensive set of DEGs influenced by Cd stress, and heavy metal stress, and provide new information for elucidating the neurotoxic mechanisms of Cd stress in spiders.

Risk assessment of effects of cadmium on human health (IUPAC Technical Report)

Chemistry and Human Health, Division VII of the International Union on Pure and Applied Chemistry (IUPAC), provides guidance on risk assessment methodology and, as appropriate, assessment of risks to human health from chemicals of exceptional toxicity. The aim of this document is to describe dose-response relationships for the health effects of low-level exposure to cadmium, in particular, with an emphasis on causation. The term “cadmium” in this document includes all chemical species of cadmium, as well as those in cadmium compounds. Diet is the main source of cadmium exposure in the general population. Smokers and workers in cadmium industries have additional exposure. Adverse effects have been shown in populations with high industrial or environmental exposures. Epidemiological studies in general populations have also reported statistically significant associations with a number of adverse health effects at low exposures. Cadmium is recognized as a human carcinogen, a classification mainly based on occupational studies of lung cancer. Other cancers have been reported, but dose-response relationships cannot be defined. Cardiovascular disease has been associated with cadmium exposure in recent epidemiological studies, but more evidence is needed in order to establish causality. Adequate evidence of dose-response relationships is available for kidney effects. There is a relationship between cadmium exposure and kidney effects in terms of low molecular mass (LMM) proteinuria. Long-term cadmium exposures with urine cadmium of 2 nmol mmol−1 creatinine cause such effects in a susceptible part of the population. Higher exposures result in increases in the size of these effects. This assessment is supported by toxicokinetic and toxicodynamic (TKTD) modelling. Associations between urine cadmium lower than 2 nmol mmol−1 creatinine and LMM proteinuria are influenced by confounding by co-excretion of cadmium with protein. A number of epidemiological studies, including some on low exposures, have reported statistically significant associations between cadmium exposure and bone demineralization and fracture risk. Exposures leading to urine cadmium of 5 nmol mmol−1 creatinine and more increase the risk of bone effects. Similar associations at much lower urine cadmium levels have been reported. However, complexities in the cause and effect relationship mean that a no-effect level cannot be defined. LMM proteinuria was selected as the critical effect for cadmium, thus identifying the kidney cortex as the critical organ, although bone effects may occur at exposure levels similar to those giving rise to kidney effects. To avoid these effects, population exposures should not exceed that resulting in cadmium values in urine of more than 2 nmol mmol−1 creatinine. As cadmium is carcinogenic, a ‘safe’ exposure level cannot be defined. We therefore recommend that cadmium exposures be kept as low as possible. Because the safety margin for toxic effects in kidney and bone is small, or non-existent, in many populations around the world, there is a need to reduce cadmium pollution globally.

Transcriptional inhibition of TCDD-mediated induction of cytochrome P450 1A1 and alteration of protein expression in a zebrafish hepatic cell line following the administration of TCDD and Cd2

We studied the effects of Cd²⁺ on TCDD-mediated induction of the cytochrome P450 1A1 (cyp1a1) gene using a zebrafish liver cell line (ZFL). Our results showed that Cd²⁺ inhibited the TCDD-mediated induction of the cyp1a1 protein, enzyme activity, and mRNA expression level. Cd²⁺ also down-regulated levels of the aryl hydrocarbon receptor (ahr2) and the aryl hydrocarbon receptor nuclear translocator 2b (arnt2b) mRNAs. Compared with TCDD (3nM) treatment alone, co-treatment with Cd²⁺ (0-30μM) and TCDD (3nM) significantly inhibited the activity of the luciferase reporter gene constructs harboring the distal promoter region (P-2626/-2009) of CYP1A1 and the synthetic 3XRE gene promoter. This indicates that Cd²⁺ decreased the level of TCDD-induced cyp1a1 through transcriptional inhibition. Proteomic analysis was also used to evaluate the effect of Cd²⁺ on TCDD-altered protein expression in ZFL cells. The identified proteins are mainly enzymes of the glycolysis pathway and proteasomes, and have anti-oxidative and anti-stress effects.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

Cadmium exposure and its association with serum uric acid and hyperuricemia

Few studies have investigated the association between serum uric acid (UA) and cadmium exposure. Our previous study revealed a significantly higher blood cadmium (CdB) level in the Chinese population compared to populations in other countries. To determine whether CdB in Chinese adults is associated with serum UA and hyperuricemia, 2996 participants from the cross-sectional SPECT-China study were recruited. CdB was measured by atomic absorption spectrometry. Hyperuricemia was defined as a serum UA concentration ≥416.4 μmol/L for men and ≥356.9 μmol/L for women. Regression analyses were used to analyze the association of CdB with serum UA and hyperuricemia. We found that the median CdB level was higher in men with hyperuricemia (2.40 μg/L) than in men without hyperuricemia (1.98 μg/L, P < 0.05). A positive relationship between serum UA and CdB was found in Chinese men after adjusting for the estimated glomerular filtration rate (eGFR), current smoking status, diabetes, dyslipidemia, hypertension and body mass index and in participants with eGFR > 60 mL/min per 1.73 m². Further, the odds ratio of hyperuricemia increased with increasing CdB quartiles (P for trend < 0.05) in men. In conclusion, CdB was positively related to the serum UA level and to hyperuricemia in Chinese men but not in Chinese women.

Arsenite and Cadmium Activate MAPK/ERK via Membrane Estrogen Receptors and G-Protein Coupled Estrogen Receptor Signaling in Human Lung Adenocarcinoma Cells

Epidemiological evidence indicates that cadmium and arsenic exposure increase lung cancer risk. Cadmium and arsenic are environmental contaminants that act as endocrine disruptors (EDs) by activating estrogen receptors (ERs) in breast and other cancer cell lines but their activity as EDs in lung cancer is untested. Here, we examined the effect of cadmium chloride (CdCl2) and sodium arsenite (NaAsO2) on the proliferation of human lung adenocarcinoma cell lines. Results demonstrated that both CdCl2 and NaAsO2 stimulated cell proliferation at environmentally relevant nM concentrations in a similar manner to 17β-estradiol (E2) in H1793, H2073, and H1944 cells but not in H1792 or H1299 cells. Further studies in H1793 cells showed that 100 nM CdCl2 and NaAsO2 rapidly stimulated mitogen-activated protein kinase (MAPK, extracellular-signal-regulated kinases) phosphorylation with a peak detected at 15 min. Inhibitor studies suggest that rapid MAPK phosphorylation by NaAsO2, CdCl2, and E2 involves ER, Src, epidermal growth factor receptor, and G-protein coupled ER (GPER) in a pertussis toxin-sensitive pathway. CdCl2 and E2 activation of MAPK may also involve ERβ. This study supports the involvement of membrane ER and GPER signaling in mediating cellular responses to environmentally relevant nM concentrations of CdCl2 and NaAsO2 in lung adenocarcinoma cells.

Estrogenic endocrine disruptors: Molecular mechanisms of action

A comprehensive summary of more than 450 estrogenic chemicals including estrogenic endocrine disruptors is provided here to understand the complex and profound impact of estrogen action. First, estrogenic chemicals are categorized by structure as well as their applications, usage and effects. Second, estrogenic signaling is examined by the molecular mechanism based on the receptors, signaling pathways, crosstalk/bypassing and autocrine/paracrine/homeostatic networks involved in the signaling. Third, evaluation of estrogen action is discussed by focusing on the technologies and protocols of the assays for assessing estrogenicity. Understanding the molecular mechanisms of estrogen action is important to assess the action of endocrine disruptors and will be used for risk management based on pathway-based toxicity testing.

Cadmium and proliferation in human uterine leiomyoma cells: evidence of a role for EGFR/MAPK pathways but not classical estrogen receptor pathways

BACKGROUND

It has been proposed that cadmium (Cd) is an environmental "metalloestrogen" and that its action is mediated via the estrogen receptor (ER). Cd mimics the effects of estrogen in the rat uterus, and blood Cd concentrations positively correlate with ER levels in uteri of women with fibroids.

OBJECTIVES

In the present study we explored whether Cd could stimulate proliferation of estrogen-responsive human uterine leiomyoma (ht-UtLM) cells and uterine smooth muscle cells (ht-UtSMCs) through classical interactions with ERα and ERβ, or by nongenomic mechanisms.

METHODS

We used estrogen response element (ERE) reporters, phosphorylated receptor tyrosine kinase arrays, Western blot analysis, estrogen binding, and cell proliferation assays to evaluate the effects of Cd on ht-UtLM cells and ht-UtSMCs.

RESULTS

Cd stimulated growth of both cell types at lower concentrations and inhibited growth at higher concentrations (≥ 50 μM). Cd did not significantly bind to ERα or ERβ, nor did it show transactivation in both cell types transiently transfected with ERE reporter genes. However, in both cells types, Cd (0.1 μM and 10 μM) activated p44/42 MAPK (ERK1/2), and a MAPK inhibitor (PD98059) abrogated Cd-induced cell proliferation. Cd in ht-UtLM cells, but not in ht-UtSMCs, activated the growth factor receptors EGFR, HGFR, and VEGF-R1 upstream of MAPK. Additional studies in ht-UtLM cells showed that AG1478, an EGFR inhibitor, abolished Cd-induced phosphorylation of EGFR and MAPK.

CONCLUSIONS

Our results show that low concentrations of Cd stimulated cell proliferation in estrogen-responsive uterine cells by nongenomic activation of MAPK, but not through classical ER-mediated pathways.

Non-renal effects and the risk assessment of environmental cadmium exposure

BACKGROUND

Exposure to cadmium (Cd) has long been recognized as a health hazard, both in industry and in general populations with high exposure. Under the currently prevailing health risk assessment, the relationship between urinary Cd (U-Cd) concentrations and tubular proteinuria is used. However, doubts have recently been raised regarding the justification of basing the risk assessment on this relationship at very low exposure.

OBJECTIVES

Our objective was to review available information on health effects of Cd exposure with respect to human health risk assessment.

DISCUSSION

The associations between U-Cd and urinary proteins at very low exposure may not be due to Cd toxicity, and the clinical significance of slight proteinuria may also be limited. More importantly, other effects have been reported at very low Cd exposure. There is reason to challenge the basis of the existing health risk assessment for Cd. Our review of the literature found that exposure to low concentrations of Cd is associated with effects on bone, including increased risk of osteoporosis and fractures, and that this observation has implications for the health risk assessment of Cd. Other effects associated with Cd should also be considered, in particular cancer, although the information is still too limited for appropriate use in quantitative risk assessment.

CONCLUSION

Non-renal effects should be considered critical effects in the health risk assessment of Cd.

Cadmium toxicity and treatment

Cadmium is a heavy metal of considerable toxicity with destructive impact on most organ systems. It is widely distributed in humans, the chief sources of contamination being cigarette smoke, welding, and contaminated food and beverages. Toxic impacts are discussed and appear to be proportional to body burden of cadmium. Detoxification of cadmium with EDTA and other chelators is possible and has been shown to be therapeutically beneficial in humans and animals when done using established protocols.

Metals and breast cancer

Metalloestrogens are metals that activate the estrogen receptor in the absence of estradiol. The metalloestrogens fall into two subclasses: metal/metalloid anions and bivalent cationic metals. The metal/metalloid anions include compounds such as arsenite, nitrite, selenite, and vanadate while the bivalent cations include metals such as cadmium, calcium, cobalt, copper, nickel, chromium, lead, mercury, and tin. The best studied metalloestrogen is cadmium. It is a heavy metal and a prevalent environmental contaminant with no known physiological function. This review addresses our current understanding of the mechanism by which cadmium and the bivalent cationic metals activate estrogen receptor-α. The review also summarizes the in vitro and in vivo evidence that cadmium functions as an estrogen and the potential role of cadmium in breast cancer.