Tubular and glomerular kidney effects in the Chinese general population with low environmental cadmium exposure

Screening of bioactive components in Ferula assafo dried oleo-gum resin and assessment of its protective function against cadmium-induced oxidative damage, genotoxicity, and cytotoxicity in rats

Cadmium (Cd) is among the most ecologically harmful heavy metals. The purpose of this work was to identify the biologically active components in dried oleo-resin-gum of Ferula assafo extract (FAE) and assess their preventive efficacy against oxidative damage caused by Cd in rats. The biologically active components were identified using HPLC and GC-MS. Six groups of female Sprague-Dawley rats were randomly assigned and received oral treatment for two weeks. They consisted of the control group, the groups that got FAE at low or high doses (150 and 250 mg/kg b.w.), the group that received CdCl2 (2 mg/kg b.w.), and the groups that received CdCl2 + FAE at the low or high dose. Tissues and blood samples were collected for different assays and pathological examinations. The HPLC detected 11 polyphenol compounds, whereas the GC-MS identified 24 bioactive compounds. The in vivo study revealed that CdCl2 alone disrupted all biochemical indices, oxidative indicators, cytokines, antioxidant enzymes, pro and anti-apoptotic mRNA gene expression, increased DNA fragmentation percentage, and caused pathological alterations in hepatic and renal sections. FAE plus CdCl2 therapy considerably improved all indicators and the histological architecture of the kidney and liver, with the higher dose being more effective in improving all of the measured parameters. Therefore, FAE is a promising option for food and pharmaceutical applications to protect against oxidative damage caused by Cd exposure.

Health risk assessment of dietary cadmium exposure based on cadmium bioavailability in food: Opportunities and challenges

Long-term exposure to Cd through contaminated food can lead to multiple adverse health effects on humans. Although previous studies have covered global food Cd concentrations and dietary Cd exposures across different populations, there are increasing concerns regarding the adequacy of current food Cd safety standards to protect populations from adverse health effects. Moreover, incorporation of Cd relative bioavailability (Cd-RBA) in foods improves the accuracy of health risk assessment. However, factors influencing food Cd-RBA have not been systematically discussed, thereby hindering its application in risk assessment. This review aims to provide an overview of Cd contents in foods, discuss concerns regarding international food Cd concentration standards, explore factors influencing food Cd bioavailability, and highlight the opportunities and challenges in refining differences between dietary Cd intakes and body burdens. Our findings suggest that current safety standards may be insufficient to protect human health, as they primarily focus on kidney damage as the protective endpoint and fail to account for global and regional variations in food consumption patterns and temporal changes in dietary habits over time. Factors such as crop cultivars and food compositions greatly influence food Cd-RBA. To improve the accuracy of Cd health risk assessment, future studies should incorporate food Cd-RBA, sociodemographic characteristics, nutritional status, and incidental Cd exposure. This review highlights new insights into food Cd safety standards and Cd bioavailability, identifies critical knowledge gaps, and offers recommendations for refining health risk assessments. This information is essential to inform future bioavailability investigations, health risk assessment, and safety standard development.

Association between exposure to arsenic, cadmium, and lead and chronic kidney disease: evidence from four practical statistical models

BACKGROUND

Environmental exposure to arsenic (As), lead (Pb) and cadmium (Cd) may cause chronic kidney disease (CKD), with varying independent effects and unclear combined impact. This study aimed to evaluate these effects on CKD.

METHODS

1,398 individuals were included. Urine arsenic (UAs) was determined by atomic fluorescence method. Urinary cadmium (UCd) and blood lead (BPb) levels were determined by graphite-furnace atomic absorption spectrometry. CKD was defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2 or proteinuria. Generalized linear models (GLM), restricted cubic spline (RCS) models, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) models were employed to study the independent and combined effects of exposure to As, Pb and Cd on CKD risk.

RESULTS

Compared with non-CKD subjects, UAs, UCd, BPb, and creatinine adjusted urinary cadmium (UCdCr) were all significantly higher in CKD subjects. Compared with the lowest quartiles, the ORs (95%CIs) of CKD risk in the highest quartiles were 2.09 (1.16-3.74) for UAs, 2.84(1.56-5.18) for UCd, and 1.79 (1.05-3.06) for UCdCr, respectively. UAs, UCd, and UCdCr were all significantly positively associated with CKD risk in p-trend tests. RCS models revealed non-linear links between UAs, UCd, UCdCr and CKD risk, while a linear dose-response existed for BPb and CKD risk. The OR (95%CI) in WQS models were 1.72 (1.25-2.36) with UAs being the highest weighing metal(loid). BKMR models showed co-exposure mixture linked to higher CKD risk when the ln-transformed metal(loid)s above their 55th percentile. The ln-transformed UAs and UCdCr was significantly positively associated with CKD risk when the other two ln-transformed metals levels were all fixed at their different percentile levels. Synergism between Cd and Pb was also apparent.

CONCLUSIONS

Single As, and Cd exposure were positively associated with an increased CKD risk. Co-exposure to As, Pb and Cd was positively associated with CKD risk, with As playing a dominant role.

Health Hazards Associated with Dietary Exposure of Female Rat to Cadmium-Contaminated Cooked Rice: Biochemical, Hormonal, and Histopathological Analysis

The actual exposure, bioavailability, and body burden of dietary cadmium (Cd) vary with the food matrix. Here, we evaluated the health hazards of 45-day long-term exposure of growing Sprague-Dawley (SD) female rats to a natural and endogenous Cd-contaminated brown and white cooked rice dietary model. Cd was found mainly in the duodenum, kidney, and liver; the cecum and colon also contained substantial amounts of Cd in rats fed Cd-contaminated cooked white rice (cWR-test) but not Cd-contaminated cooked brown rice (cBR-test). Damage due to Cd exposure was reflected in liver dysfunction, altered estradiol levels, and distinctive pathologies in organ systems, although urinary Cd (U-Cd) excretion and blood Cd (B-Cd) were not detectable, suggesting that these are not the most accurate or appropriate biomarkers for evaluating dietary Cd exposure. Brown rice, despite being higher in Cd, can reduce Cd absorption and distribution in organs and increase the volume of Cd-containing feces, even achieving slightly higher excretion and lower apparent absorption rates of Cd than white rice, thereby reducing Cd damage to the body. The beneficial components of brown rice such as more dietary fiber, rice bran oil and polyphenol were speculated therefore to confer a degree of protection or repair. Nevertheless, the high apparent absorption levels observed here (> 5%) and signs of significant physical damage indicate that more stringent Cd intake guidelines and measures are needed to minimize Cd levels in rice.

Prenatal Exposure to Heavy Metals and Adverse Birth Outcomes: Evidence From an E-Waste Area in China

Electronic waste that has not been properly treated can lead to environmental contamination including of heavy metals, which can pose risks to human health. Infants, a sensitive group, are highly susceptible to heavy metals exposure. The aim of this study was to investigate the association between prenatal heavy metal exposure and infant birth outcomes in an e-waste recycling area in China. We analyzed cadmium (Cd), chromium (Cr), manganese (Mn), lead (Pb), copper (Cu), and arsenic (As) concentrations in 102 human milk samples collected 4 weeks after delivery. The results showed that 34.3% of participants for Cr, which exceeds the World Health Organization (WHO) guidelines, as well as the mean exposure of Cr exceeded the WHO guidelines. We collected data on the birth weight (BW) and length of infants and analyzed the association between metal concentration in human milk and birth outcomes using multivariable linear regression. We observed a significant negative association between the Cd concentration in maternal milk and BW in female infants (β = -162.72, 95% CI = -303.16, -22.25). In contrast, heavy metals did not associate with birth outcomes in male infants. In this study, we found that 34.3% of participants in an e-waste recycling area had a Cr concentration that exceeded WHO guidelines, and there was a significant negative association between prenatal exposure to the Cd and infant BW in females. These results suggest that prenatal exposure to heavy metals in e-waste recycling areas may lead to adverse birth outcomes, especially for female infants.

The Protective Potential of Aronia melanocarpa L. Berry Extract against Cadmium-Induced Kidney Damage: A Study in an Animal Model of Human Environmental Exposure to This Toxic Element

The impact of cadmium (Cd) on the function and structure of the kidney and the potential protective effect of an extract from Aronia melanocarpa L. berries were investigated in a rat model of low- and moderate-level environmental exposure to this heavy metal (1 and 5 mg Cd/kg feed for up to 24 months). The sensitive biomarkers of Cd-induced damage to the kidney tubules (N-acetyl-β-D-glucosaminidase (NAG), alkaline phosphatase (ALP), β2-microglobulin (β2-MG), and kidney injury molecule-1 (KIM-1) in the urine), clinically relevant early markers of glomerular damage (albumin in the urine and creatinine clearance), and other markers of the general functional status of this organ (urea, uric acid, and total protein in the serum and/or urine) and Cd concentration in the urine, were evaluated. The morphological structure of the kidney and inflammatory markers (chemerin, macrophage inflammatory protein 1 alpha (MIP1a), and Bcl2-associated X protein (Bax)) were also estimated. Low-level and moderate exposure to Cd led to damage to the function and structure of the kidney tubules and glomeruli. The co-administration of A. melanocarpa berry extract significantly protected against the injurious impact of this toxic element. In conclusion, even low-level, long-term exposure to Cd poses a risk of kidney damage, whereas an intake of Aronia berry products may effectively protect from this outcome.

Current Levels of Environmental Exposure to Cadmium in Industrialized Countries as a Risk Factor for Kidney Damage in the General Population: A Comprehensive Review of Available Data

The growing number of reports indicating unfavorable outcomes for human health upon environmental exposure to cadmium (Cd) have focused attention on the threat to the general population posed by this heavy metal. The kidney is a target organ during chronic Cd intoxication. The aim of this article was to critically review the available literature on the impact of the current levels of environmental exposure to this xenobiotic in industrialized countries on the kidney, and to evaluate the associated risk of organ damage, including chronic kidney disease (CKD). Based on a comprehensive review of the available data, we recognized that the observed adverse effect levels (NOAELs) of Cd concentration in the blood and urine for clinically relevant kidney damage (glomerular dysfunction) are 0.18 μg/L and 0.27 μg/g creatinine, respectively, whereas the lowest observed adverse effect levels (LOAELs) are >0.18 μg/L and >0.27 μg/g creatinine, respectively, which are within the lower range of concentrations noted in inhabitants of industrialized countries. In conclusion, the current levels of environmental exposure to Cd may increase the risk of clinically relevant kidney damage, resulting in, or at least contributing to, the development of CKD.

Sex-Specific Associations of Urinary Metals with Renal Function: a Cross-sectional Study in China

BACKGROUND

Extensive studies have revealed the link between heavy metals and CKD. Compared to single meta-elements, mixture of metals reflect real-life metals exposure scenarios and are of interest. However, the mechanism of action of metal mixture on renal function is unclear.

METHODS

This study aimed to explore the potential relationship between urinary arsenic (As), cadmium (Cd), lead (Pb), manganese (Mn), and chromium (Cr) contents with estimated glomerular filtration rate (eGFR) levels in 2775 participants. The levels of metals in urine were determined by inductively coupled plasma-mass spectrometry. We used linear regression models and the Bayesian kernel machine regression (BKMR) to evaluate the association between metals and eGFR levels.

RESULTS

In linear regression analysis, urinary As (β = 2.723, 95%CI: 0.29, 5.157) and Pb (β = 3.081, 95%CI: 1.725, 4.438) were positively associated with eGFR in the total population. In the BKMR model, a mixture of the five metals had a positive joint effect on eGFR levels, while Pb (PIP = 0.996) contributed the most to eGFR levels. Pb was positively associated with eGFR levels in the total participants and women. As was positively correlated with eGFR levels in women. Pb and eGFR levels were positively correlated when the other metals were set at 25th, 50th, and 75th percentiles.

CONCLUSIONS

To the best of our knowledge, all five metals mixed exposure was positively associated with eGFR. Pb showed more important effects than the other four metals in the mixture, especially in women.

Kisspeptin as potential biomarker of environmental chemical mixture effect on reproductive hormone profile: A pilot study in adolescent males

BACKGROUND

Kisspeptin has been proposed as an effect biomarker to understand the mechanisms by which some environmental chemicals adversely affect the human reproductive system.

OBJECTIVE

To ascertain whether kisspeptin serum protein and DNA methylation levels are associated with exposure to several environmental chemicals (individually and as a mixture) and serum reproductive hormone levels in adolescent males.

METHODS

Three phenols (bisphenol A [BPA], methyl-paraben [MPB], and benzophenone-3 [BP3]); two toxic metals (arsenic and cadmium); and four metabolites of non-persistent pesticides, including insecticides (2-isopropyl-6-methyl-4-pyrimidinol [IMPy], malathion diacid [MDA], and dimethylcyclopropane carboxylic acid [DCCA]) and fungicides (ethylene thiourea [ETU]) were measured in first-morning urine samples of 133 adolescent males aged 15-17 years from the INMA-Granada cohort. In blood samples collected on the same day, KISS1 gene DNA methylation was measured at four CpGs from the Exon IV, as well as serum levels of kiss54 protein, total testosterone (T), estradiol (E₂), sex hormone binding-globulin, dehydroepiandrosterone sulfate, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). Multiple linear regression and mixture (quantile g-computation) models were fit.

RESULTS

Urinary MDA and DCCA concentrations were associated with higher kiss54 levels [% change (95%CI) for each log-unit increase in concentration = 2.90 (0.32;5.56), and 1.93 (0.45,3.43), respectively]; IMPy with lower DNA methylation percentage at CpG1 and total CpGs [% change (95%CI) = -1.15 (-1.96;-0.33): -0.89 (-1.73;-0.01), respectively]; and BP3 and DCCA with lower total CpGs methylation [-0.53 (-1.04;-0.01) and - 0.69 (-1.37;-0.01), respectively]. The pesticide mixture and the whole chemical mixture were associated with higher kiss54 [% change (95%CI) = 9.09 (3.29;15.21) and 11.61 (3.96;19.82), respectively] and lower methylation levels at several CpGs. Additionally, serum kiss54 in the third tertile was associated with higher LH levels [% change (95%CI) = 28.69 (3.75-59.63)], and third-tertile CpG1, CpG2, and total CpG methylation percentages were associated with lower FSH and E₂.

CONCLUSION

The findings of the present study and the negative correlation between serum kiss54 levels and KISS1 DNA methylation percentages suggested that kisspeptin may be a promising effect biomarker.

Insights into the health status of the general population living near an electroplating industry zone: metal elevations and renal impairment

A cross-sectional study was conducted in 2016 in Zhejiang Province, China, to evaluate the body burdens of metals and metalloids associated with renal dysfunction in populations living near electroplating industries. We recruited 236 subjects and performed physical examinations, determined the blood and urinary levels of arsenic (As), cadmium (Cd), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), and selenium (Se) by an inductively coupled plasma mass spectrometer (ICP-MS), and measured three renal impairment biomarkers, namely nacetyl-β-_D-glucosaminidase (NAG), retinol-binding protein (RBP), and β₂-microglobulin (BMG). The proportion of abnormal nasal symptoms in the exposure group (10.1%) was much higher than in the control group (0; p < 0.05). The blood and urinary levels of As, Cd, and Se in the exposure group were significantly higher than those in the control group (p < 0.05). The blood levels of Mn and Pb, as well as the urinary levels of Cr and Ni, were significantly higher in the exposure group than in the control group (p < 0.05). The exposure group demonstrated higher levels of NAG, RBP, and BMG than the control group (0.51 vs. 0.14 mg/g creatinine, 12.79 vs. 9.26 IU/g creatinine, and 1.39 vs. 0.78 mg/g creatinine, respectively; p < 0.05). Urinary BMG was positively correlated with urinary Cd levels (r = 0.223, p < 0.05), while urinary RBP was correlated with blood Cd levels (r = 0.151, p < 0.05) and urinary Cd, Cr, Ni, and Se levels (r = 0.220, 0.303, 0.162, and 0.306, respectively; p < 0.05). In conclusion, our study indicated that a population living in the vicinity of electroplating industries had high body burdens of certain metals and metalloids associated with non-negligible renal dysfunction.

Effects of mixed heavy metals on kidney function in premenopausal and postmenopausal women

OBJECTIVE

To evaluate the relationships between heavy metals (cadmium, lead, and mercury) and their mixtures and estimated glomerular filtration rate (eGFR) in premenopausal and postmenopausal women.

METHODS

Using data from the Korean National Health and Nutrition Examination Survey (2009-2017), multivariate linear regression models, marginal effects, and weighted quantile sum regression, we assessed the associations between single heavy metals and their mixtures and eGFR among 5,372 women.

RESULTS

Risks of reduced eGFR, comorbidities, and heavy metal exposure were found to be higher in postmenopausal women than in premenopausal women. A negative association of cadmium ( β = -2.97; 95% CI, -5.10 to -0.85) and a positive association of mercury ( β = 2.97; 95% CI, 1.49 to 4.44), with eGFR in postmenopausal women. Inverse associations of lead with eGFR in both premenopausal women ( β = -4.75; 95% CI, -6.04 to -3.46) and postmenopausal women ( β = -4.54; 95% CI, -6.96 to -2.13). Interactions were identified between lead and mercury, as well as cadmium and lead for eGFR among premenopausal women ( β = -2.04; 95% CI, -2.98 to -1.10) and postmenopausal women ( β = -3.52; 95% CI, -6.04 to -1.01), respectively. There was a negative association between mixed heavy metals and eGFR in both premenopausal women ( β = -2.23; 95% CI, -3.51 to -0.96) and postmenopausal women ( β = -3.86; 95% CI, -6.89 to -0.83). Lead was found as a key chemical related to reduced eGFR. Cutoff values for each heavy metal concentration related to eGFR were provided.

CONCLUSION

Postmenopausal women were more influenced by mixed heavy metals' effects on kidney function than premenopausal women. Early interventions (eg, water filtering, heavy metal yearly screening) in women, especially postmenopausal women, are needed to reduce the incidence of chronic kidney disease.

Estimation of health risks associated with dietary cadmium exposure

In much of the world, currently employed upper limits of tolerable intake and acceptable excretion of cadmium (Cd) (ECd/Ecr) are 0.83 µg/kg body weight/day and 5.24 µg/g creatinine, respectively. These figures were derived from a risk assessment model that interpreted β2-microglobulin (β2MG) excretion > 300 μg/g creatinine as a "critical" endpoint. However, current evidence suggests that Cd accumulation reduces glomerular filtration rate at values of ECd/Ecr much lower than 5.24 µg/g creatinine. Low ECd/Ecr has also been associated with increased risks of kidney disease, type 2 diabetes, osteoporosis, cancer, and other disorders. These associations have cast considerable doubt on conventional guidelines. The goals of this paper are to evaluate whether these guidelines are low enough to minimize associated health risks reliably, and indeed whether permissible intake of a cumulative toxin like Cd is a valid concept. We highlight sources and levels of Cd in the human diet and review absorption, distribution, kidney accumulation, and excretion of the metal. We present evidence for the following propositions: excreted Cd emanates from injured tubular epithelial cells of the kidney; Cd excretion is a manifestation of current tissue injury; reduction of present and future exposure to environmental Cd cannot mitigate injury in progress; and Cd excretion is optimally expressed as a function of creatinine clearance rather than creatinine excretion. We comprehensively review the adverse health effects of Cd and urine and blood Cd levels at which adverse effects have been observed. The cumulative nature of Cd toxicity and the susceptibility of multiple organs to toxicity at low body burdens raise serious doubt that guidelines concerning permissible intake of Cd can be meaningful.

Environmental exposure of the general population to cadmium as a risk factor of the damage to the nervous system: A critical review of current data

Nowadays, more and more attention has been focused on the risk of the neurotoxic action of cadmium (Cd) under environmental exposure. Due to the growing incidence of nervous system diseases, including neurodegenerative changes, and suggested involvement of Cd in their aetiopathogenesis, this review aimed to discuss critically this element neurotoxicity. Attempts have been made to recognize at which concentrations in the blood and urine Cd may increase the risk of damage to the nervous system and compare it to the risk of injury of other organs and systems. The performed overview of the available literature shows that Cd may have an unfavourable impact on the human's nervous system at the concentration >0.8 μg Cd/L in the urine and >0.6 μg Cd/L in the blood. Because such concentrations are currently noted in the general population of industrialized countries, it can be concluded that environmental exposure to this xenobiotic may create a risk of damage to the nervous system and be involved in the aetiopathogenesis of neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, as well as worsening cognitive and behavioural functions. The potential mechanism of Cd neurotoxicity consists in inducing oxidative stress, disrupting the activity of enzymes essential to the proper functioning of the nervous system and destroying the homoeostasis of bioelements in the brain. Thus, further studies are necessary to recognize accurately both the risk of nervous system damage in the general population due to environmental exposure to Cd and the mechanism of this action.

Urinary cadmium and peripheral blood telomere length predict the risk of renal function impairment: a study of 547 community residents of Shanxi, China

Few reports have investigated the predictive value of urinary cadmium (UCd) and telomere length on renal function impairment. Therefore, we constructed nomogram models, using a cross-sectional survey to analyze the potential function of UCd and telomere length in renal function impairment risk. We randomly selected two community populations in Shanxi, China, and general information of the subjects was collected through face-to-face questionnaire surveys. Venous blood of subjects was collected to detect absolute telomere length (ATL) by real-time quantitative chain reaction (RT-PCR). Collecting urinary samples detected UCd and urinary N-acetyl-β-d-glucosaminidase (UNAG). Estimated glomerular filtration rate (eGFR) was obtained based on serum creatinine (SCr). Nomogram models on risk prediction analysis of renal function impairment was constructed. After adjusting for other confounding factors, UCd (β = 0.853, 95% confidence interval (CI): 0.739 ~ 0.986) and ATL (β = 1.803, 95%CI: 1.017 ~ 1.154) were independent risk influencing factors for increased UNAG levels, and the risk factors for eGFR reduction were UCd (β = 1.011, 95%CI: 1.187 ~ 1.471), age (β = 1.630, 95%CI: 1.303 ~ 2.038), and sex (β = 0.181, 95%CI: 0.105 ~ 0.310). Using UCd, ATL, sex, and age to construct the nomogram, and the C-statistics 0.584 (95%CI: 0.536 ~ 0.632) and 0.816 (95%CI: 0.781 ~ 0.851) were obtained by internal verification of the calibration curve, C-statistics revealed nomogram model validation was good and using decision curve analysis (DCA) confirmed a good predictive value of the nomogram models. In a nomogram model, ATL, UCd, sex, and age were detected as independent risk factors for renal function impairment, with UCd being the strongest predictor.

Protective Effects of Astilbin Against Cadmium-Induced Apoptosis in Chicken Kidneys via Endoplasmic Reticulum Stress Signaling Pathway

Cadmium (Cd) can cause endoplasmic reticulum stress (ERS) and apoptosis in animals. The kidney is an organ seriously affected by Cd because it can accumulate metal ions. Astilbin (ASB) is a dihydroflavonol rhamnoside, which has an anti-renal injury effect. This study aimed to evaluate the protective effect of ASB on Cd-induced ERS and apoptosis in the chicken kidney. In this study, a total of 120 1-day-old chickens were randomly divided into 4 groups. Chickens were fed with a basic diet (Con group), ASB 40 mg/kg (ASB group), CdCl₂ 150 mg/kg + ASB 40 mg/kg (ASB/Cd group), and CdCl₂ 150 mg/kg (Cd group) for 90 days. The results showed that Cd exposure induced pathological and ultrastructural damages and apoptosis in chicken kidneys. Compared with the Con group, metallothionein (MT1/MT2) level, nitric oxide (NO) content, inducible nitric oxide synthase (iNOS) activity, ERS-related genes 78-kDa glucose-regulated protein (Grp78), protein kinase PKR-like endoplasmic reticulum kinase (Perk), activating transcription factor 4 (Atf4) and CAAT/enhancer-binding protein (C/EBP) homologous protein (Chop), and pro-apoptotic gene B-cell lymphoma 2 (Bcl-2)-associated X (Bax), caspase-12, caspase-9, caspase-3 expression levels, and apoptotic rate were significantly increased in the Cd group. The expression level of Bcl-2 was significantly decreased in the Cd group. ASB/Cd combined treatment significantly improves the damage of chicken kidneys by ameliorating Cd-induced kidney ERS and apoptosis. Cd can cause the disorder of the GRP78 signal axis, activate the PERK-ATF4-CHOP pathway, aggravate the structural damage and dysfunction of ER, and promote the apoptosis of chicken kidneys, while the above changes were significantly alleviated in the ASB/Cd group. The results showed that ASB antagonizes the negative effects of Cd and against Cd-induced apoptosis in chicken kidneys via ERS signaling pathway.

The Effects of Lead and Cadmium Co-exposure on Serum Ions in Residents Living Near a Mining and Smelting Area in Northwest China

In this study, we investigated the associations between cadmium (Cd) and lead (Pb) co-exposure, and serum ion levels in two populations living near a mining/smelting area and a nature reserve (control area), respectively. A total of 445 participants were included in this study. Their blood cadmium (BCd), blood lead (BPb), and serum ion levels were determined, and the association between exposure levels and serum ion levels was analyzed. The exposure levels of subjects living in the polluted area were significantly higher (p < 0.001). Lower levels of potassium, inorganic phosphorus, and iron were observed in subjects from the polluted area, whereas their sodium and chloride levels were higher (p < 0.01). The anion gap in their serum was also significantly lower. We observed positive dose-effect relationships between Cd and/or Pb exposure and serum sodium and chloride, and negative dose-effect relationships between Cd and/or Pb exposure and serum inorganic phosphorus, iron, as well as the anion gap. High Cd-Pb, high Cd, and high Pb exposure led to modification effects in potassium, calcium, inorganic phosphorus, and iron levels, and the anion gap. No synergistic effects were observed in our results. In conclusion, our data demonstrate that Cd and Pb exposure, alone or in combination, can lead to serum ion imbalances.

Effect of varying pH and co-existing microcystin-LR on time- and concentration-dependent cadmium sorption by goethite-modified biochar derived from distillers' grains

Cadmium (Cd) is one dangerous and widespread heavy metal that of great environmental concern. To cost-efficiently adsorb aqueous Cd under influence of various factors, this study succeeded in fabricating goethite-modified biochar (GBC) derived from distillers' grains (DGs) for Cd sorption of different concentrations (10-100 mg L^-1) at pH of 3, 6 and 8 with and without microcystin-LR (MC-LR). Sorption kinetics and isotherms data revealed that Cd sorption capacity of GBC and unmodified BC increased as pH elevated from 3 to 6 but stabilized when pH further elevated to 8. Pseudo-second-order and Langmuir models more accurately fitted to sorption data for both BCs, implying monolayer chemisorption of Cd onto BCs. GBC exhibited more robust sorption for each Cd concentration than unmodified BC, with the maximum sorption capacity of around 28 mg g^-1 at neutral and weak alkaline pH. Notably, goethite-modification obviously increased bulk polarity, specific surface area, porosity and surface oxygenic group abundance of BC, thus strongly enhancing Cd sorption by creating more sorption sites mainly via pore-filling, electrostatic attraction, and also via complexation and cation exchange. Co-existing MC-LR of 100 μg L^-1 did not obviously affect Cd sorption by both BCs for most Cd levels at each pH, mostly because sorption mechanisms diverged between MC-LR and Cd to largely avoid their competition for sorption sties. Thus, goethite could modify DG-BC as promising and cost-efficient sorbent for Cd even with co-existing MC-LR, especially at neutral and weak alkaline pH that common in the nature. This study was greatly implicated in modifying and applying DG-BC for Cd immobilization in MC-LR laden waters with various pH circumstances.

Influence of serum ferritin combined with blood cadmium concentrations on blood pressure and hypertension: From the Korean National Health and Nutrition Examination Survey

BACKGROUND

Previous studies have suggested that cadmium (Cd) exposure and serum ferritin levels may influence the development of hypertension.

OBJECTIVE

We evaluated whether the association between blood Cd levels and the development of hypertension could be modified by serum ferritin levels in a representative sample of the adult population of South Korea.

METHODS

We used data from the Korean National Health and Nutrition Examination Survey (2008-2012), a nationally representative, cross-sectional, population-based study. We included 5752 adults aged 19 years and older who had records of blood Cd and ferritin levels and blood pressure measurements. Multiple logistic regression was used to examine the association between Cd exposure and the development of hypertension, as well as the modifying effects of serum ferritin.

RESULTS

Men had higher levels of serum ferritin, and women had higher levels of Cd. Smoking in men was significantly associated with high blood pressure and risk of hypertension. Significantly fewer women were smokers, and the combination of abnormal serum ferritin levels and high Cd levels was significantly associated with high systolic blood pressure [odds ratio (OR) = 2.11; 95% confidence interval (CI) = 1.04-4.28], high diastolic blood pressure (OR = 2.07; 95% CI = 1.04-4.12), and increased hypertension risk (OR = 1.83; 95% CI = 1.03-3.25) in women who never smoked.

CONCLUSIONS

Our results provide further evidence that individuals with abnormal serum ferritin levels should limit their exposure to Cd to prevent hypertension.

Construction of Mode of Action for Cadmium-Induced Renal Tubular Dysfunction Based on a Toxicity Pathway-Oriented Approach

Although it is recognized that cadmium (Cd) causes renal tubular dysfunction, the mechanism of Cd-induced nephrotoxicity is not yet fully understood. Mode of action (MOA) is a developing tool for chemical risk assessment. To establish the mechanistic MOA of Cd-induced renal tubular dysfunction, the Comparative Toxicogenomics Database (CTD) was used to obtain genomics data of Cd-induced nephrotoxicity, and Ingenuity^® Pathway Analysis (IPA) software was applied for bioinformatics analysis. Based on the perturbed toxicity pathways during the process of Cd-induced nephrotoxicity, we established the MOA of Cd-induced renal tubular dysfunction and assessed its confidence with the tailored Bradford Hill criteria. Bioinformatics analysis showed that oxidative stress, DNA damage, cell cycle arrest, and cell death were the probable key events (KEs). Assessment of the overall MOA of Cd-induced renal tubular dysfunction indicated a moderate confidence, and there are still some evidence gaps to be filled by rational experimental designs.

Effects of Cadmium Exposure on the Immune System and Immunoregulation

Cadmium (Cd), a biologically non-essential heavy metal, is widespread in the environment, including the air, water, and soil, and is widely present in foods and quantum dot preparations. Cd enters the body primarily through inhalation and ingestion. Its biological half-life in humans is 10-35 years; therefore, Cd poses long-term health risks. While most studies on Cd toxicity have focused on organ and tissue damage, the immunotoxicity of Cd has drawn increasing attention recently. Cd accumulates in immune cells, modulates the function of the immune system, triggers immunological responses, and leads to diverse health problems. Cd acts as an immunotoxic agent by regulating the activity and apoptosis of immune cells, altering the secretion of immune cytokines, inducing reactive oxygen species (ROS) production and oxidative stress, changing the frequency of T lymphocyte subsets, and altering the production of selective antibodies in immune cells. This review summarizes the immunological toxicity of Cd, elucidates the mechanisms underlying Cd toxicity in terms of innate immunity and adaptive immunity, and discusses potential strategies to alleviate the adverse effects of Cd on the immune system.

Elevated cadmium and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in residents living near electroplating industries

This study aims to evaluate the body burdens of cadmium (Cd) associated with potential health impairment in residents living near electroplating industries. A total of 269 residents from exposure area and 106 from control area were recruited. We measured the blood and urinary Cd levels using an inductively coupled plasma mass spectrometer (ICP-MS); performed physical examinations; determined the urinary levels of β₂-microglobulin (β₂-MG), Nacetyl-β-_D-glucosaminidase (NAG), and 8-hydroxy-2'-deoxyguanosine (8-OHdG); and evaluated the associations between Cd and these biomarkers. Blood and urinary Cd levels in exposure group were statistically higher than in control group (1.712 vs. 1.159 μg/L; 1.980 vs. 1.740 μg/L, respectively, p < 0.05). Urinary β₂-MG and 8-OHdG levels in exposure group were also statistically higher (0.448 vs. 0.090 mg/L; 12.759 vs. 12.115 μg/L, respectively, p < 0.05), but urinary NAG levels showed no significant difference between the two groups (13.614 vs. 8.246 IU/L, p > 0.05). The proportion of abnormal nasal symptoms occurring in exposed subjects (88.8%) was much higher than in control subjects (78.2%, p < 0.05). Urinary Cd levels were positively correlated with blood Cd levels, urinary 8-OHdG, and NAG levels (r = 0.307, r = 0.185, r = 0.150, p < 0.05), but not correlated with urinary β₂-MG levels (p > 0.05). In conclusion, our study revealed that residents living in close proximity to electroplating industries had elevated body burdens of Cd levels, as well as slight renal dysfunction and DNA oxidation damage.

CircSPAG16 suppresses cadmium-induced transformation of human bronchial epithelial cells by decoying PIP5K1α to inactivate Akt

Circular RNAs (circRNAs) have been implicated to have important regulatory functions in chemical carcinogenesis via sponging microRNAs to regulate gene expression. Our study revealed a novel mechanism of circRNA in cadmium carcinogenesis through directly binding with protein. Here, we used cadmium-transformed human bronchial epithelial BEAS-2B cells to study the involvement and mechanism of circRNA in lung carcinogenesis caused by cadmium. By high-throughput sequencing, circSPAG16 was identified to be the most significantly downregulated circRNA in cadmium-transformed cells. CircSPAG16 was downregulated at Week 8, 12, 16, and 20 during cadmium-induced cell transformation. In addition, circSPAG16 overexpression prevented cadmium-induced transformation of BEAS-2B cells. Mechanistically, circSPAG16 inhibited the function of phosphatidylinositol 4-phosphate 5-kinase type-1 α (PIP5K1α) by binding with it. We demonstrated that PIP5K1α acted as an oncogene to activate Akt and promoted cancer hallmarks including proliferation, migration, invasion, and anchorage-independent growth in cadmium-transformed cells. CircSPAG16 overexpression inactivates PIP5K1α/Akt signaling in the transformed cells. Furthermore, PIP5K1α overexpression significantly rescued the inhibitory effects of circSPAG16 overexpression on pAkt and cancer hallmarks in cadmium-transformed cells. Collectively, our results revealed that circSPAG16 could prevent cadmium-induced transformation through binding with PIP5K1α to inactivate Akt. These results provide a novel regulatory mechanism of circRNA into carcinogenesis induced by cadmium.

The association between estimated glomerular filtration rate and cadmium exposure: An 8-year follow-up study

BACKGROUND

The associations between cadmium exposure and chronic kidney disease have rarely been reported in longitudinal studies. In this study, we investigated the associations between the estimated glomerular filtration rate and cadmium exposure in a cross-sectional study in a longitudinal cohort.

MATERIALS AND METHODS

In total, 790 subjects (≥35 years of age) living in southeastern China were included at 1998. Cadmium in blood (BCd) and urine (UCd) as well as renal dysfunction biomarkers, urinary N-acetyl-β d-glucosaminidase (UNAG) and albumin (UALB), were determined. 497 subjects were followed at 2006 and a total of 456 subjects were finally included after excluding subjects that did not have exposure or effects biomarkers. The BCd, UCd, UNAG and UALB were determined using baseline methods. At follow-up, the estimated glomerular filtration rate (eGFR) was computed using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Single nucleotide polymorphisms (SNPs) in metallothioneins 1A (MT1A) rs11076161 and MT2A rs28366003 in blood sample were detected using TaqMan allelic discrimination assays.

RESULTS

The median of UCd and BCd at baseline was 5.38 μg/g cr and 4.69 μg/L, respectively, and the median UCd and BCd at follow-up was 4.88 μg/g cr and 2.20 μg/L at follow-up. The mean eGFR at follow-up was 88.0 mL/min/1.73 m² and 15 subjects had new onset of eGFR <60 mL/min/1.73 m². The eGFR at follow-up was associated with baseline age (β = -0.66, 95% confidence interval (CI): 0.80 to -0.52), BCd (β = -0.46, 95% CI: 0.68 to -0.25) and UALB (β = -0.29, 95% CI: 0.41 to -0.16) after adjusting for confounders. Subgroup analysis in subjects who had low baseline UALB or subjects with or without hypertension showed similar results. A logistic regression model further showed that baseline BCd and UALB were independent risk factors for follow-up CKD. The odds ratios (ORs) were 1.09 (95% CI:1.03-1.16) for UALB, 1.16 (95% CI:1.01-1.33) for BCd, and 6.74 (0.87-29.63) for current hypertension. Baseline BCd, UALB and current hypertension were used to construct the nomogram. Linear discriminant analysis (LCA) showed that 87.6% of CKD was accurately predicted based on the three factors.

CONCLUSION

Baseline age, BCd and UALB were associated with follow-up eGFR, and baseline BCd and UALB were predictive factors for incidence of CKD.

Speciation and fate of toxic cadmium in contaminated paddy soils and rice using XANES/EXAFS spectroscopy

The present study was conducted to determine the Cd distribution and speciation in contaminated paddy soils and rice kernels using XANES/EXAFS spectroscopy. The morphology and crystallization of rice and soils were investigated using FE-SEM and XRD techniques. The EXAFS spectra of Cd in soil and rice kernels showed that cadmium oxides (CdO) in soil and rice kernels formed Cd clusters with Cd-O bond distances of 2.35 Å and 2.25 Å (coordination numbers of 2.3 and 3.8), respectively. The XRD patterns show that silica oxide (SiO₂, 2θ = 24.2) and aluminum oxide (Al₂O₃, 2θ = 35.7) were the main components detected. The FE-SEM analysis revealed that the surface characteristics and sizes of the rice kernels are smooth and uneven with particle sizes of 0.5-4 µm, while the soil particles are not uniform and aggregated. Furthermore, the distribution of toxic metals/metalloid (Cd, Pb, Cr, Ni, As, Cu, and Zn) accumulated in the contaminated paddy soils and rice crops were also examined. Interestingly, these results offered an insight into the accumulation mechanism and distribution of heavy metals in contaminated rice farming soils and rice crops.

Cadmium exposure triggers osteoporosis in duck via P2X7/PI3K/AKT-mediated osteoblast and osteoclast differentiation

Cadmium is a common environmental pollutant that accumulates in the bone and kidneys and causes severe health and social problems. However, the effects of Cd on the occurrence of osteoporosis and its mechanism of action in this process are unclear. To test whether Cd-induced osteoporosis is mediated via P2X7/PI3K/AKT signaling, duck bone marrow mesenchymal stem cells (BMSCs) and bone marrow macrophage cells (BMMs) were treated with Cd for 5 days, and duck embryos were treated with Cd_. Micro-CT analysis indicated that Cd-induced osteoporosis occurs in vivo, and histopathology and immunohistochemical analyses also revealed that Cd induced bone damage and the downregulation of osteogenic and bone resorption-related proteins. Cd exposure significantly inhibited the differentiation of BMSCs and BMMs into osteoblasts and osteoclasts in vitro, and promoted osteoblast and osteoclast apoptosis. Cd exposure significantly downregulated the P2X7/PI3K/AKT signaling pathway in vivo and in vitro, and inhibition of this signaling pathway significantly aggravated osteoblast and osteoclast differentiation. Cd exposure also upregulated the OPG/RANKL ratio in vivo and in vitro, further inhibiting osteoclast differentiation. These results demonstrate that Cd causes osteoporosis in duck by inhibiting P2X7/PI3K/AKT signaling and increasing the OPG/RANKL ratio. These results establish a previously unknown mechanism of Cd-induced osteoporosis.

Environmental Pollution and Chronic Kidney Disease

Chronic kidney disease (CKD) is a global public health problem associated with high rates of morbidity and mortality due to end-stage renal disease and cardiovascular disease. Safe and effective medications to reverse or stabilize renal function in patients with CKD are lacking, and hence it is important to identify modifiable risk factors associated with worsening kidney function. Environmental pollutants, including metals, air pollutant, phthalate and melamine can potentially increase the risk of CKD or accelerate its progression. In this review, we discuss the epidemiological evidence for the association between environmental pollution and kidney disease, including heavy metals, air pollution and other environmental nephrotoxicants in the general population.

Ameliorative effects of resveratrol against cadmium-induced nephrotoxicity via modulating nuclear xenobiotic receptor response and PINK1/Parkin-mediated Mitophagy

Cadmium (Cd) is a toxic pollutant with high nephrotoxicity in the agricultural environment. Resveratrol has been found to have a renoprotective effect but the underlying mechanisms of this have not yet been fully elucidated. The aim of this study is to illustrate the antagonism of resveratrol against Cd-induced nephrotoxicity. A total of 80 birds were divided randomly into 4 groups and treated via diet for 90 days as follows: control group (Con); 400 mg kg-1 resveratrol group (Resv); 140 mg kg-1 Cd group (Cd 140); and 140 mg kg-1 Cd + 400 mg kg-1 resveratrol group (Cd + Resv). It was observed that resveratrol treatment dramatically alleviated Cd-induced histopathological lesions of the kidney. Simultaneously, resveratrol mitigated Cd-induced oxidative stress by reducing MDA and H2O2 production, alleviating GSH depletion and restoring the activity of antioxidant enzymes (T-SOD, Cu-Zn SOD, CAT, GST and GSH-Px). Resveratrol activated NXRs (CAR/PXR/AHR/Nrf2) signaling pathways and exerted antidotal roles by enhancing the phase I and II detoxification systems to relieve oxidative damage. Moreover, resveratrol ameliorated Cd-induced ultrastructural abnormality and mitochondria dysfunction by recovering mitochondrial function-related factors VDAC1, Cyt C and Sirt3 upregulation and Sirt1, PGC-1α, Nrf1 and TFAM transcription restrictions. Resveratrol attenuated Cd-induced excessive mitochondrial fission and promoted mitochondrial fusion, which reversed PINK1/Parkin-mediated mitophagy initiation. Collectively, our findings explicate the potential protection against Cd-induced nephrotoxicity and mitochondria damage.

Cadmium and Lead Exposure, Nephrotoxicity, and Mortality

The present review aims to provide an update on health risks associated with the low-to-moderate levels of environmental cadmium (Cd) and lead (Pb) to which most populations are exposed. Epidemiological studies examining the adverse effects of coexposure to Cd and Pb have shown that Pb may enhance the nephrotoxicity of Cd and vice versa. Herein, the existing tolerable intake levels of Cd and Pb are discussed together with the conventional urinary Cd threshold limit of 5.24 μg/g creatinine. Dietary sources of Cd and Pb and the intake levels reported for average consumers in the U.S., Spain, Korea, Germany and China are summarized. The utility of urine, whole blood, plasma/serum, and erythrocytes to quantify exposure levels of Cd and Pb are discussed. Epidemiological studies that linked one of these measurements to risks of chronic kidney disease (CKD) and mortality from common ailments are reviewed. A Cd intake level of 23.2 μg/day, which is less than half the safe intake stated by the guidelines, may increase the risk of CKD by 73%, and urinary Cd levels one-tenth of the threshold limit, defined by excessive ß₂-microglobulin excretion, were associated with increased risk of CKD, mortality from heart disease, cancer of any site and Alzheimer's disease. These findings indicate that the current tolerable intake of Cd and the conventional urinary Cd threshold limit do not provide adequate health protection. Any excessive Cd excretion is probably indicative of tubular injury. In light of the evolving realization of the interaction between Cd and Pb, actions to minimize environmental exposure to these toxic metals are imperative.

Correlation between environmental low-dose cadmium exposure and early kidney damage: A comparative study in an industrial zone vs. a living quarter in Shanghai, China

To investigate heavy metal exposure in an industrial zone vs. a living quarter in Shanghai and explore the relationship between the heavy metal source and urine cadmium (Cd) and early kidney damage. Blood lead and urine Cd, manganese (Mn), mercury (Hg), arsenic (As) and EKD indexes were compared between residents in Exposure group (n = 168) and Control group (n = 168). It was found that PM_2.5 level in Exposure group was significantly higher than that in Control group, and serum Cys-C and urine Cd, NAG, mAlb, KIM-1 and Cd-MT levels in Exposure group were also significantly higher than those in Control group, suggesting that differences in urine Cd and heavy metal levels between the residents of the two groups may be due to different PM_2.5 concentrations in the environments of the two areas. Cd accumulation within the human body can induce kidney damage, probably through its potential hazard to the proximal tubular epithelial cells.

Abscisic acid (ABA)-importing transporter 1 (AIT1) contributes to the inhibition of Cd accumulation via exogenous ABA application in Arabidopsis

Soil cadmium (Cd) accumulation presents risks to crop safety and productivity. However, through an exogenous application of abscisic acid (ABA), its accumulation in plants can be reduced and its toxicity mitigated, thereby providing an alternative strategy to counteract Cd contamination of arable soil. In the present study, we demonstrated that exogenous ABA application alleviates Cd-induced growth inhibition and photosynthetic damage in wild-type (Col-0) Arabidopsis plants. However, these positive effects were weakened in the ABA-importing transporter (AIT1)-deficient mutant (ait1). Through further analysis, we found that upon ABA application, the decrease in Cd level significantly differed among ait1, Col-0, and the two AIT1-overexpressing transgenic plants (AIT1ox-1 and AIT1ox-2), suggesting that AIT1 mediates the Cd-reducing effects of ABA. ABA application also inhibited the expression of IRT1, ZIP1, ZIP4, and Nramp1 in Col-0 plants subjected to Cd stress. However, significant differences among the genotypes (ait1, Col-0 and AIT1ox) were only observed in terms of IRT1 expression. Overall, our findings suggest that the suppression of Cd accumulation and restoration of plant growth by exogenous ABA require the ABA-importing activity of AIT1 to inhibit IRT1 expression.

Assessment of exposure to toxic metals and measures to address deficiency of essential trace elements in young children in rural Hubei, China

Children are exposed to toxic metals via diet and environment, which results in adverse health effects. Several trace elements are important for the nutritional status of children; however, little information is available for rural regions in Asia. Our goal was to assess the body burden of lead, cadmium, and aluminum (Al) as toxic metals and calcium (Ca), zinc, copper, selenium (Se), strontium, and boron as trace elements in children. Multiple environmental samples, including soil, dust, fine particulates, drinking water, and food, were collected for each family. A survey was conducted by trained personnel to record detailed information about children attending a rural school. Twenty-four-hour urine samples were collected. The levels of toxic and essential trace elements were determined by inductively coupled plasma mass spectrometry. We found that the daily intake of toxic metals was below the recommended maximum, suggesting low health risks. More attention should be given to the ingestion of Al by the hand-to-mouth pathway. Ca deficiency was discovered to be a serious health problem for rural children, with Ca inadequacies reaching 96%. The excessive intake of Se-rich products from industry suggests an increased risk of toxicity. This study highlights the health risks to children who live in rural regions and the importance of dietary Ca supplementation in school meals.

Beneficial Impact of an Extract from the Berries of Aronia melanocarpa L. on the Oxidative-Reductive Status of the Submandibular Gland of Rats Exposed to Cadmium

Oxidative stress underlies the pathomechanisms of toxic action of cadmium (Cd), including its damaging impact on the oral cavity. This study investigated whether the administration of an extract from Aronia melanocarpa L. berries (AME), characterized by their strong antioxidative potential, may have a beneficial impact on the oxidative-reductive status of the submandibular gland in an experimental model of low-level and moderate human environmental exposure to cadmium. The main markers of the antioxidative status (glutathione reductase, superoxide dismutase, catalase, reduced glutathione, total antioxidative status (TAS)), total oxidative status (TOS), oxidative stress index (OSI = TOS/TAS), and lipid peroxides, as well as cadmium concentration, were evaluated in the submandibular gland tissue of female Wistar rats who received a 0.1% aqueous AME and/or a diet containing 0, 1, and 5 mg Cd/kg for 3 and 10 months. The treatment with cadmium decreased the activities of antioxidative enzymes (29%-74%), reduced glutathione concentration (45%-52%), and TAS and increased TOS, resulting in the development of oxidative stress and enhanced concentration of lipid peroxides in the submandibular gland. The administration of AME at both levels of exposure to cadmium offered significant protection against these actions of this xenobiotic. After the 10 month exposure to the 1 and 5 mg Cd/kg diet, TAS was decreased by 77% and 83%, respectively, TOS, OSI, and lipid peroxides concentration were increased by 50% and 52%, respectively, 11.8-fold and 14.4-fold, respectively, and 2.3-fold and 4.3-fold, respectively, whereas, in the case of the extract co-administration, the values of these parameters did not differ compared to the control group. The results indicate that the consumption of aronia products under exposure to cadmium may have a beneficial impact on the oxidative-reductive status of the submandibular gland and prevent oxidative stress development and enhanced lipid peroxidation in this salivary gland.

Speciation and fate of toxic cadmium in contaminated paddy soils and rice using XANES/EXAFS spectroscopy

The present study was conducted to determine the Cd distribution and speciation in contaminated paddy soils and rice kernels using XANES/EXAFS spectroscopy. The morphology and crystallization of rice and soils were investigated using FE-SEM and XRD techniques. The EXAFS spectra of Cd in soil and rice kernels showed that cadmium oxides (CdO) in soil and rice kernels formed Cd clusters with Cd-O bond distances of 2.35 Å and 2.83 Å (coordination numbers of 2.3 and 4.2), respectively. The XRD patterns show that silica oxide (SiO₂, 2θ  = 24.2) and aluminum oxide (Al₂O₃, 2θ = 35.7) were the main components detected. The FE-SEM analysis revealed that the surface characteristics and sizes of the rice kernels are smooth and uneven with particle sizes of 0.5-4 μm, while the soil particles are not uniform and aggregated. Furthermore, the distribution of toxic metals/metalloid (Cd, Pb, Cr, Ni, As, Cu, and Zn) accumulated in the contaminated paddy soils and rice crops were also examined. Interestingly, these results offered an insight into the accumulation mechanism and distribution of heavy metals in contaminated rice farming soils and rice crops.

A cross-sectional study on school-age children living near a municipal waste incinerator: Urinary metal levels and renal impairment assessment

To take an insight into the long-term accumulation of chromium (Cr) and cadmium (Cd) in school-age children living near an MWI and to assess their early renal impairment, we conducted a cross-sectional study in 2015. A total of 116 children from the exposure area and 122 from the control area were recruited. We measured the urinary levels of Cr (U-Cr) and Cd (U-Cd) by inductively coupled plasma mass spectrometry (ICP-MS), and detected three classic renal tubule indicators, including N-acetyl-β-_d-glucosaminidase (NAG), β2-microglobulin (BMG), and retinol binding protein (RBP). The U-Cd and U-Cr levels in children living near the MWI were 0.11 and 1.57 μg/g creatinine, respectively. Both the U-Cd and U-Cr levels in the exposure group were lower than those in the control group, although only U-Cd showed a statistical difference (p < 0.01). The U-NAG and U-RBP levels in the exposure group were also statistically lower than those in the control group (0.80 vs. 1.74 IU/g creatinine, 0.26 vs. 0.48 mg/g creatinine, respectively). The U-Cd level in this study was positively correlated with the U-NAG level (r = 0.26, p < 0.01), as the U-Cr level was also positively correlated with the levels of U-NAG, U-RBP, and U-BMG (r = 0.21, 0.33, 0.18, p < 0.01, respectively). This study indicates that children living close to this particular MWI may not suffer considerable long-term accumulation of Cd or Cr, nor early renal impairment.

The Role of Selenium in Arsenic and Cadmium Toxicity: an Updated Review of Scientific Literature

Arsenic (As) and cadmium (Cd) are elements arousing major public health concerns associated with environmental pollution, high toxicity potential, and carcinogenic nature. However, selenium (Se) at low doses and incorporated into enzymes and proteins has antioxidant properties and protects animals and humans from the risk of various diseases. It also has an exceptionally narrow range between necessary and toxic concentrations, which is a well-known hindrance in its use as a dietary supplement. The present article aims to update and expand the role of Se in As and Cd toxicity discussed in our earlier paper. In general, recent reports show that Se, regardless of its form (as selenite, selenomethionine, nanoSe, or Se from lentils), can reduce As- or Cd-mediated toxicity in the liver, kidney, spleen, brain, or heart in animal models and in cell culture studies. As was suggested in our earlier review, Se antagonizes the toxicity of As and Cd mainly through sequestration of these elements into biologically inert complexes and/or through the action of Se-dependent antioxidant enzymes. An increase in the As methylation efficiency is proposed as a possible mechanism by which Se can reduce As toxicity. However, new studies indicate that Se may also diminish As or Cd toxicity by activation of the Nrf2 pathway. In addition, this paper discusses possible signs of Se toxic effects, which may be a challenge for its future use in the therapy of As and Cd poisoning and provide future directions to address this issue.

Subchronic Exposure to Cadmium Causes Persistent Changes in the Reproductive System in Female Wistar Rats

Cadmium (Cd) is an environmental toxicant and endocrine disruptor in humans and animals, and recent studies have illustrated that the uterus is exceedingly sensitive to Cd toxicity. The aim of the study was to investigate the influence of subchronic (90 days) oral Cd exposure in daily doses of 0.09-4.5 mg/kg b.w. on the balance of sex hormones by estimating estradiol (E₂) and progesterone (P) concentrations in the uterus and plasma in comparison with the effects of 17β-E₂. Additionally, the uterine weight, histopathological changes in the uterus and ovaries, the regularity of the estrous cycle, Cd bioaccumulation in uterine tissue, and selected biochemical parameters of oxidative stress were determined. A long period of observation (three and six months following the administration period) was used to assess whether the existing effects are reversible. The lowest dose of Cd caused effects similar to 17β-E₂: an increase of E₂ concentration in the uterus, endometrial epithelium thickness, and disturbed estrous cycle with estrus phase prolongation. The obtained results suggest that Cd causes nonlinear response. Higher doses of Cd caused a significant decrease in E₂ concentration in the uterus and plasma, estrous cycle disturbances, endometrium atrophy, and structural damage in the ovaries. This dose additionally induces lipid peroxidation in the uterine tissues. It is noteworthy that a prolonged time of observation after terminating the exposure showed persistent changes in the concentration of E₂ in uterine tissue, as well as alterations in estrous cycle phases, and an increase in lipid peroxidation in the uterus. Moreover, significant positive correlations between the plasma E₂ concentration and endometrial epithelium thickness in all studied groups were found. In summary, subchronic oral Cd exposure of female rats may result in impaired fertility processes.

The Protective Impact of Black Chokeberry Fruit Extract (Aronia melanocarpa L.) on the Oxidoreductive System of the Parotid Gland of Rats Exposed to Cadmium

Cadmium (Cd) is a strongly toxic heavy metal with prooxidative properties. Since the exposure of the general population to this metal is predicted to increase, effective methods are being sought to prevent its negative actions. One of them involves the use of the antioxidant potential of polyphenol compounds contained in black chokeberry fruit extract and their capability of complex formation with Cd2+. The study objective was to investigate whether the administration of A. melanocarpa fruit extract rich in polyphenol compounds during low and moderate exposures to cadmium can protect the parotid gland against oxidative damage. The study was conducted using the experimental model on female Wistar rats which were given 0.1% aqueous extract of Aronia melanocarpa fruit (AE) and/or cadmium at a concentration of 1 (Cd1) or 5 (Cd5) mg Cd/kg feed for 3 and 10 months, and on control animals. The exposure to Cd attenuated the enzymatic antioxidant barrier (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx)) and increased the concentration of hydrogen peroxide (H2O2), protein carbonyl (PC) groups, and oxidized lipids (LPO) in parotid gland. These disorders led to a reduction in the total antioxidative status (TAS), an increase in the total oxidative state (TOS), and development of stress. The administration of AE at both levels of exposure to cadmium substantially improved the enzymatic antioxidant barrier (CAT, SOD, GPx) and prevented oxidative damage to cellular macromolecules (PC, LPO) and the increase in the level of H2O2, MPO, TOS, and stress indicator (OSI = TOS/TAS) in the parotid gland. Concluding, it should be stated that the consumption of aronia products may prevent oxidative/antioxidative imbalance induced by Cd and oxidative stress development in the parotid gland, thus protecting the gland from damage.

Cadmium exposure triggers mitochondrial dysfunction and oxidative stress in chicken (Gallus gallus) kidney via mitochondrial UPR inhibition and Nrf2-mediated antioxidant defense activation

Cadmium (Cd) is a widespread environmental pollutant that accumulates in living systems and represents a significant global health hazard. Cd poses a toxicity threat to both human and animal health, including that of birds. Further knowledge of Cd toxicology pathways will allow for a better understanding of Cd-induced nephrotoxicity. To evaluate Cd-induced nephrotoxicity through potential oxidative damage, male chickens were treated with 0 mg/kg, 35 mg/kg or 70 mg/kg CdCl₂ in diet for 90 days. Markedly, histopathology indicated renal tubular epithelial cell swelling, renal function CREA content abnormalities, biochemical and morphologic indices indicative of Cd-induced kidney injury. Cd toxicity induced the up-regulation of Nrf2 and downstream target genes that relieve oxidative stress. Meanwhile, Cd disrupted the homeostasis of trace elements and promoted oxidative damage. Cd interfered with mitochondrial unfolded protein response (UPR^mt)-related factors (SIRT1, SIRT3, PGC-1α, TFAM, Nrf1, and HTRA2) and disrupted the homeostasis of mitochondrial dynamics (OPA1, MFN1, MFN2, Fis1 and MFF), thereby exacerbating mitochondrial structural damage and mitochondrial dysfunction. In conclusion, our study demonstrated that the nephrotoxicity of Cd exposure results in oxidative stress and mitochondrial dysfunction by activating the Nrf2 signaling pathway and inhibiting UPR^mt in the kidneys.

Systematic evaluation of exposure to trace elements and minerals in patients with chronic kidney disease of uncertain etiology (CKDu) in Sri Lanka

Chronic kidney disease of uncertain etiology (CKDu) in areas in and around Sri Lanka's North Central Province has been identified as a major non-communicable disease due to its high prevalence and the burden on the public health system. Controversial evidence relating to the etiology and risk factors of CKDu has been reported. The most debated is the role of trace elements such as Cd and As in the pathogenesis of CKDu. Urine and hair samples collected from CKDu patients and healthy controls were measured for the concentration of different elements including Cd and As. To assess the possible environmental exposures, drinking water and rice samples collected from the affected areas as well as unaffected areas in the country were analyzed. Transmission electronic microscopic analysis of renal biopsies from CKDu patients was also performed. Analysis of drinking water and rice samples indicated that the levels of all minerals and trace elements analyzed including Cd and As were within the levels recommended by World Health Organization and Sri Lanka drinking water guidelines and did not suggest any form of contamination. Analysis of biological samples, including urine, hair and renal tissue, did not provide evidence to support Cd or As toxicity in CKDu patients. Overall, the observations of this integrated, comprehensive study, which included biological, environmental and pathological investigations, strongly support our previous reports on the absence of Cd and As toxicity in areas with high prevalence of CKDu. Further, these observations do not provide evidence on the involvement of Cd and As in pathogenesis of CKDu in Sri Lanka.

Toxic Metals and Chronic Kidney Disease: a Systematic Review of Recent Literature

PURPOSE OF REVIEW

Arsenic (As), cadmium (Cd), and lead (Pb) are ubiquitous toxicants with evidence of adverse kidney impacts at high exposure levels. There is less evidence whether environmental exposure to As, Cd, or Pb plays a role in development of chronic kidney disease (CKD). We conducted a systematic review to summarize the recent epidemiologic literature examining the relationship between As, Cd, or Pb with CKD.

RECENT FINDINGS

We included peer-reviewed studies published in English between January 2013 and April 2018 for As and Cd, and all dates prior to April 2018 for Pb. We imposed temporality requirements for both the definition of CKD (as per NKF-KDOQI guidelines) and environmental exposures prior to disease diagnosis. Our assessment included cohort, case-control or cross-sectional study designs that satisfied 5 inclusion criteria. We included a total of eight articles of which three, two, and four studies examined the effects of As, Cd, or Pb, respectively. Studies of As exposure consistently reported positive association with CKD incidence; studies of Pb exposure were mixed. We found little evidence of association between Cd exposure and CKD. Additional well-designed prospective cohort studies are needed and we present recommendations for future studies.

The association between lead and cadmium co-exposure and renal dysfunction

Both cadmium (Cd) and lead (Pb) exposure can induce kidney damage. However, the effects of combined exposure to Cd and Pb on renal function at environmental levels have not been fully clarified. In this study we investigated the renal function in a Chinese population co-exposed to Cd and Pb. A total of 331 subjects (215 women and 116 men), living in either a control or a polluted area, were included in this study. Cd and Pb in blood and urine (BCd, BPb, UCd, and UPb), and kidney effect markers including urinary N-acetyl-β-D-glucosaminidase (UNAG) and estimated glomerular filtration rate (eGFR), were determined, and the association between exposure markers and renal effect biomarkers were analyzed. The exposure levels in the polluted area were significantly higher than in the control area (all p < 0.01). The eGFR of subjects in the polluted area was decreased compared with that in the control area (p < 0.01). The subjects with high BCd/BPb (BCd ≥ 2 μg/L, BPb ≥ 100 μg/L) or high UCd/UPb (UCd ≥ 3 μg/g creatinine, UPb ≥ 10 μg/g creatinine) showed higher UNAG and UALB levels compared with other subgroups (p < 0.01). The probability of having elevated UNAG in subjects with high BCd/BPb was greater than those with low BCd/BPb [odds ratio (OR) = 2.6, 95% confidence interval (CI): 1.4-4.7), low BCd/high BPb (OR =3.1, 95% CI: 1.4-6.6), and high BCd/low BPb (OR = 1.7, 95% CI: 0.9-3.2). The OR of subjects with low UCd and high UPb, high UCd and low UPb, and high UCd/UPb were 2.9 (95% CI: 1.4-5.7), 3.3 (95% CI: 1.5-7.2), and 7.7 (95% CI: 4.0-14.7), respectively, compared with those with low UCd/UPb. The risk of decrease in eGFR was also higher in subjects with high UCd/UPb than for those with low UCd/UPb (OR = 7.2, 95% CI: 0.8-62.2). Our data demonstrate that Cd and Pb exposure, alone or in combination, are associated with renal impairment. In addition, co-exposure to Pb and Cd propagates the renal tubular dysfunction compared with Cd or Pb exposure alone.

Global burden of late-stage chronic kidney disease resulting from dietary exposure to cadmium, 2015

Chronic exposures to cadmium (Cd) are associated with reduced glomerular filtration rate (GFR), increasing the risk of chronic kidney disease (CKD). In support of the World Health Organization (WHO)'s initiative to estimate the global burden of foodborne diseases, a risk assessment was performed to estimate the Disability-Adjusted Life Years (DALYs) due to late-stage CKD associated with dietary exposures to cadmium. Using the distribution of population GFRs, the prevalence of CKD was calculated as the proportion of humans whose GFR fall in the ranges corresponding to Stage 4 or Stage 5 CKD. The increase in the CKD prevalence due to cadmium exposure was simulated based on a previously reported pharmacokinetic model describing the relationship between dietary cadmium intake and urinary cadmium (UCd), as well as a previously published dose-response relationship between UCd and GFR. Cadmium-related incidence rate, calculated as the change in the prevalence during a one-year period, were used to compute the mortality and DALY in all WHO regions. It is estimated that dietary cadmium would result in a median of 12,224 stage 4 and stage 5 new CKD cases per year worldwide, resulting in 2064 global deaths and 70,513 DALYs. These data translate into a median global burden of 1.0 DALY per 100,000 population, which account for 0.2% of the global DALYs of CKD. While these results suggest that the overall impact of dietary cadmium exposure on global CKD is low, they do indicate that reasonable efforts to reduce dietary exposure will result a positive public health impact. This would be particularly the case in areas with elevated levels of dietary cadmium.

Extract from Aronia melanocarpa L. Berries Prevents Cadmium-Induced Oxidative Stress in the Liver: A Study in A Rat Model of Low-Level and Moderate Lifetime Human Exposure to this Toxic Metal

The study investigated, in a rat model of low-level and moderate environmental exposure to cadmium (Cd; 1 or 5 mg Cd/kg diet, respectively, for 3 to 24 months), whether the co-administration of 0.1% extract from Aronia melanocarpa L. berries (AE) may protect against oxidative stress in the liver and in this way mediate this organ status. The intoxication with Cd, dose- and duration-dependently, weakened the enzymatic antioxidative barrier, decreased the concentrations of reduced glutathione and total thiol groups, and increased the concentrations of oxidized glutathione, hydrogen peroxide, xanthine oxidase, and myeloperoxidase in this organ. These resulted in a decrease in the total antioxidative status, increase in the total oxidative status and development of oxidative stress (increased oxidative stress index and malondialdehyde concentration) and histopathological changes in the liver. The administration of AE at both levels of Cd treatment significantly improved the enzymatic and nonenzymatic antioxidative barrier, decreased pro-oxidant concentration, and protected from the development of oxidative stress in the liver and changes in its morphology, as well as normalized the serum activities of liver enzymes markers. In conclusion, consumption of aronia products may prevent Cd-induced destroying the oxidative/antioxidative balance and development of oxidative stress in the liver protecting against this organ damage.

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.

Cadmium exposure and early renal effects in the children and adults living in a tungsten-molybdenum mining areas of South China

Adverse health effects related to accumulative cadmium (Cd) exposure have aroused widespread attention from the public in China. Knowledge on the relationships between Cd exposure and early renal effects is particularly limited for children, who are more susceptible to absorbing metals than adults. A typical Cd-polluted area of South China was selected to determine the Cd exposure and related early renal effects of the general population, including children. In total, 211 children and 806 adults were enrolled in the study. The urinary levels of Cd (U-Cd), β₂-microglobulin (U-BMG), retinol binding protein (U-RBP), and N-acetyl-β-D-glucosaminidase (U-NAG) were measured. The relationship between U-Cd and ranked indicators of early renal effects was examined by multiple regression analysis. The average U-Cd ranged from 7.01 μg/g creatinine (boys) to 13.55 μg/g creatinine (women) in the Cd-polluted areas. These values are much higher than those of the control group and those that have been reported by other countries. In agreement with previous studies, environmental Cd pollution resulted in elevated Cd accumulation in the bodies of children, and it increased the concentration of NAG in their urine. Similarly, environmental Cd pollution increased NAG and BMG in the urine of adults. Multivariate models showed that the urinary excretion of BMG, RBP, and NAG was positively associated with Cd levels in the urine of both children and adults. The reference thresholds of U-Cd in relation to elevated U-BMG, U-RBP, and U-NAG were higher in children than adults after standardization for other covariates. These results reinforce the need to control and regulate the sources of environmental Cd contamination and to promote more effective risk management measures, especially for vulnerable groups.

Environmental exposure to cadmium-a risk for health of the general population in industrialized countries and preventive strategies

Cadmium (Cd) is a heavy metal belonging to the group of the main chemical pollutants of the natural and occupational environment in economically developed countries. The forecasts indicate that contamination of the environment with this toxic metal, and thus the exposure of the general population, will increase. Food (particularly plant products) is the main source of the general population exposure to this element. Moreover, an important, and often the main, source of intoxication with Cd is habitual tobacco smoking. Recent epidemiological studies have provided numerous evidence that even low-level environmental exposure to this toxic metal, nowadays occurring in numerous economically developed countries, creates a risk for health of the general population. The low-level lifetime exposure to this metal may lead to the damage to the kidneys, liver, skeletal system, and cardiovascular system, as well as to the deterioration of the sight and hearing. Moreover, it has been suggested that environmental exposure to this xenobiotic may contribute to the development of cancer of the lung, breast, prostate, pancreas, urinary bladder, and nasopharynx. Taking the above into account, the aim of this review article is to draw more attention to Cd as an environmental risk factor for the health of the general population and the need to undertake preventive actions allowing to reduce the risk of health damage due to a lifetime exposure to this toxic metal.

Lead, Mercury, and Cadmium Exposure in the Korean General Population

BACKGROUND

Lead (Pb), mercury (Hg), and cadmium (Cd) are well-known environmental pollutants. They are unnecessary in the biological processes of humans. This study was performed to estimate the representative background exposure levels to the metals by measuring concentrations in whole blood of the Korean general population.

METHODS

This population-based cross-sectional study included 4,000 subjects (1,886 males and 2,114 females) 0-83 years of age in 2010 and 2011. Adult subjects (≥ 19 years of age) were collected by sex- and age-stratified probability method, and preschool- and school-aged subjects were recruited by a cluster sampling method. Written consent was provided prior to blood sampling. Pb and Cd blood concentrations were determined by a flameless atomic absorption spectrophotometry, and blood Hg was analyzed by a direct Hg analyzer.

RESULTS

The geometric mean, median and 95th percentile of blood Pb was 1.82 μg/dL, 1.83 μg/dL, and 3.78 μg/dL, respectively. The respective values were 2.92 μg/L, 2.87 μg/L, 9.12 μg/L for Hg, and 0.56 μg/L, 0.59 μg/L, 2.20 μg/L for Cd. Blood Pb and Hg were higher in males than in females, but no sex difference was observed, respectively, in subjects 0-4 years of age for Pb and in subjects less than 20 years for Hg. However, blood Cd was higher in females than in males and no sex difference was observed in subjects < 30 years of age.

CONCLUSION

This study provides representative data of human exposure to Pb, Hg, and Cd covering whole age groups of the general population in Korea.

Low-Level Environmental Cadmium Exposure Induces Kidney Tubule Damage in the General Population of Korean Adults

Cadmium (Cd) is the most potent nephrotoxic heavy metal and may affect bone; it also has a long biological half-life in the human body. This study was designed to assess the effect of environmental low-level Cd exposure on kidney function and bone in the general population. The subjects of this cross-sectional study were 1907 healthy Korean adults who had not been exposed to Cd occupationally. We analyzed the concentrations of Cd in the urine, markers of renal tubule damage, such as β₂-microglobulin (β₂-MG) and N-acetyl-β-D-glucosaminidase (NAG) activity in the urine, calculated the estimated glomerular filtration rate (eGFR) using serum creatinine, and measured bone mineral density (BMD). Also, we analyzed malondialdehyde (MDA) levels in the urine. The geometric mean concentration of Cd in urine was higher in women (1.36 μg/g creatinine) than in men (0.82 μg/g creatinine). Urinary Cd was significantly positively correlated with urinary β₂-MG and NAG activity, whereas it was negatively correlated with eGFR and BMD. The risk of renal tubule damage was significantly associated with urine Cd level, and the association remained significant after controlling for various confounding variables. However, no association was observed between urinary Cd level and glomerular dysfunction or bone damage. The concentration of MDA was increased with urinary Cd level in a dose-dependent manner. These findings suggest that low-level environmental Cd exposure may cause microscopic damage to renal tubules through oxidative stress but might not impair kidney glomeruli or bones.

Urine cadmium levels and albuminuria in a general population from Spain: A gene-environment interaction analysis

BACKGROUND

The interaction of cadmium with genes involved in oxidative stress, cadmium metabolism and transport pathways on albuminuria can provide biological insight on the relationship between cadmium and albuminuria at low exposure levels.

OBJECTIVES

We tested the hypothesis that specific genotypes in candidate genes may confer increased susceptibility to cadmium exposure.

METHODS

Cadmium exposure was estimated by inductively coupled plasma mass spectrometry (ICPMS) in urine from 1397 men and women aged 18-85years participating in the Hortega Study, a representative sample of a general population from Spain. Urine albumin was measured by automated nephelometric immunochemistry. Abnormal albuminuria was defined as urine albumin greater than or equal to 30mg/g.

RESULTS

The weighted prevalence of abnormal albuminuria was 6.3%. The median level of urine cadmium was 0.39 (IQR, 0.23-0.65) μg/g creatinine. Multivariable-adjusted geometric mean ratios of albuminuria comparing the two highest to the lowest tertile of urine cadmium were 1.62 (95% CI, 1.43-1.84) and 2.94 (95% CI, 2.58-3.35), respectively. The corresponding odds ratios of abnormal albuminuria were 1.58 (0.83, 3.02) and 4.54 (2.58, 8.00). The association between urine cadmium and albuminuria was observed across all participant subgroups evaluated including participants without hypertension, diabetes or chronic kidney disease. We observed Bonferroni-corrected statistically significant interactions between urine cadmium levels and polymorphisms in gene SLC30A7 and RAC1.

CONCLUSIONS

Increasing urine cadmium concentrations were cross-sectionally associated with increased albuminuria in a representative sample of a general population from Spain. Genetic variation in oxidative stress and cadmium metabolism and transport genes may confer differential susceptibility to potential cadmium effects.