Associations of urinary cadmium with age and urinary proteins: further evidence of physiological variations unrelated to metal accumulation and toxicity

Non-occupational exposure to cadmium and breast cancer: A comprehensive and critical review

Breast cancer (BC) is a multifactorial disease with unresolved etiology. Environmental pollutants, primarily trace metals, play a pivotal role in the pathophysiological cascade of malignant tumors, including BC. In this up-to-date review, we comprehensively and critically examined the relationship between cadmium (Cd) and BC. For this purpose, peer-reviewed studies from relevant databases (PubMed, SCOPUS, and Cochrane Library) over the last 40 years were retrieved and analyzed. We found that in vitro and in vivo studies strongly support the view that Cd has harmful effects on breast health. According to the human studies, we found that Cd could be responsible for the development and progression of malignant breast tumors due to markedly higher levels in clinical matrices of cases (whole blood, urine, breast tissue, keratin materials) than in clinical matrices of controls. Cadmium does not appear to affect BC density. In contrast, Cd has been found to have a detrimental effect on sex hormones, disrupting the balance of estrogen and androgen. We found that studies looking at dietary Cd intake and BC risk generally (without measuring urine or blood Cd) do not support the association between dietary Cd intake and BC risk. In notable contrast, studies looking at dietary Cd intake and BC risk by measuring Cd in urine or blood generally support this association. The effect of airborne Cd on BC risk was weak, but in favor of specific histological forms, primarily ER-/PR- invasive tubular breast carcinomas. Regardless of the intake route of Cd into the body, it can be concluded that Cd has a harmful effect on breast health. However, well-designed longitudinal, mechanistic, meta-analytic, and other studies are urgently needed to confirm the exact role of environmental Cd in breast carcinogenesis.

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.

Increased risk of proximal tubular dysfunction due to occupational cadmium exposure: a survival analysis study

OBJECTIVES

The objective of the current study was to elucidate the relationship between blood cadmium (Cd-B) levels and proximal tubular dysfunction using urinary β2-microglobulin (B2M-U) as an indicator among workers in nickel-cadmium battery plants in Japan.

METHODS

Medical check-up data from 338 workers exposed to cadmium at 2 plants were collected from 1997 through 2020. Workers with at least 2 check-ups were included, excluding those with other renal dysfunctions. Proximal tubular dysfunction was defined as a B2M-U of 300 μg/g creatinine or higher in 2 or more consecutive check-ups. A multivariable Cox proportional-hazards regression model with time-dependent covariates was performed to analyze the relationship between Cd-B levels and the time to onset of proximal tubular dysfunction, adjusting for age, sex, and smoking history.

RESULTS

Of the 338 workers, 238 met the study eligibility criteria for the analyses. The geometric mean of Cd-B was 1.97 μg/L. The Cox proportional hazards analysis demonstrated that higher time-dependent Cd-B levels were significantly associated with an increased risk of proximal tubular dysfunction, with a hazard ratio of 1.17 (95% CI: 1.06-1.29).

CONCLUSIONS

Higher Cd-B levels are associated with an increased risk of proximal tubular dysfunction in workers exposed to cadmium, indicating an increased risk of renal disease under the current industrial health management in Japan. Continuous monitoring and improved management of cadmium exposure are necessary to protect workers' health even in developed countries such as Japan.

Internal and external microplastic exposure in young adults: A pilot study involving 26 college students in Changsha, China

OBJECTIVE

This study aimed to systematically assess the total environmental exposure to microplastics and determine the internal exposure levels in the human body.

METHODS

A total of 26 young college students were recruited. Exposure scenario estimation methods were used to establish evaluation models. The dietary and water intake behaviors of the participants were documented with questionnaires. The food and water consumed by the participants were sampled using weight and duplicate meal methods. Furthermore, air samples from the activity regions of the participants were collected. Fasting serum, 24-h urine, and fecal samples were also collected. Pyrolysis gas chromatography/mass spectrometry (Py-GCMS) helped identify the types and determine mass concentrations of microplastics across all samples, and the internal and external exposure levels of microplastics among the population were further evaluated.

RESULTS

Microplastics were frequently observed in food samples, with mass concentrations ranging from 2.50 to 91.30 μg/g. Water samples also contained microplastics, with concentrations ranging from 0.02 to 18.41 μg/g. Indoor and outdoor air contained PS, PE, PP, PVC, and PET. The exposure levels of young college students in Changsha to microplastics through dietary intake, water intake, and inhalation were quantified at 346.65 μg/kg bw/d, 41.17 μg/kg bw/d, and 59.57 μg/kg bw/d, respectively. Cumulatively, the total exposure to microplastics from these three sources was 460.20 μg/kg bw/d. Median microplastic levels in serum and feces samples were 20.81 μg/g and 97.36 μg/g, respectively. Additionally, urine samples indicated the presence of seven types of microplastics (PS, PE, PP, PVC, PET, PA66, and PMMA), with a median exposure level of 5.06 μg/g.

CONCLUSION

Among young college students in Changsha, the primary microplastic exposure source was dietary intake, followed by air and drinking water. The internal exposure level in serum was higher than that in urine.

Spatial - temporal mapping of urine cadmium levels in China during 1980 - 2040: Dietary improvements lower exposure amid rising pollution

Persistent cadmium exposure poses significant health risks to the Chinese population, underscored by its prevalence as an environmental contaminant. This study leverages a machine-learning model, fed with a comprehensive dataset of environmental and socio-economic factors, to delineate trends in cadmium exposure from 1980 to 2040. We uncovered that urinary cadmium levels peaked at 1.09 μg/g Cr in the mid-2000 s. Encouragingly, a decline is projected to 0.92 μg/g Cr by 2025, tapering further to 0.87 μg/g Cr by 2040. Despite this trend, regions heavily influenced by industrialization, such as Hunan and Guizhou, as well as industrial counties in Jilin, report stubbornly high levels of exposure. Our demographic analysis reveals a higher vulnerability among adults & adolescents over 14, with males displaying elevated cadmium concentrations. Alarmingly, the projected data suggests that by 2040, an estimated 41% of the population will endure exposure beyond the safety threshold set by the European Food Safety Authority. Our research indicates disproportionate cadmium exposure impacts, necessitating targeted interventions and policy reforms to protect vulnerable groups and public health in China.

Predictors of urinary heavy metal concentrations among pregnant women in Jinan, China

BACKGROUND

Toxic heavy metal exposure and insufficiency or excess of essential heavy metals may have negative effects on pregnant women's health and fetal growth. To date, the predictors of pregnant women's heavy metal exposure levels remain unclear and vary with different regions. The study intended to explore potential predictors of exposure to heavy metals individually and high co-exposure to heavy metal mixtures.

METHODS

We recruited 298 pregnant women in first trimester from prenatal clinics in Jinan, Shandong Province, China, and collected spot urine samples and questionnaire data on their demographic characteristics, lifestyle habits, consumption of food and dietary supplement, and residential environment. All urine samples were analyzed for seven heavy metals: cobalt (Co), molybdenum (Mo), strontium (Sr), arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg).

RESULTS

Factors associated with single heavy metal concentration were as follows: a) urinary As, Sr and Cd increased with women's age respectively; b) pregnant women with higher monthly household income per capita had lower Sr and Mo levels; c) pregnant women with intermittent folic acid supplementation and those not taking tap water as domestic drinking water had lower Sr concentrations; d) Cd was positively linked with consumption frequency of rice; e) Hg was adversely related to consumption frequency of egg and the women who took purified water as domestic drinking water had lower Hg exposure. In addition, pregnant women's age was positively associated with odds of high co-exposure to Co, As, Sr, Mo, Cd and Pb; while those with an educational level of college had lower odds of high exposure to such a metal mixture compared with those whose educational levels were lower than high school.

CONCLUSION

Predictors of single urinary heavy metal concentration included pregnant women's age (As, Sr and Cd), monthly household income per capita (Sr and Mo), folic acid supplementation (Sr), rice consumption frequency (Cd), egg consumption frequency (Hg) and the type of domestic drinking water (Sr and Hg). Pregnant women with older age, lower educational level tended to have high co-exposure to Co, As, Sr, Mo, Cd and Pb.

Blood metal/metalloid concentration of male subjects undergoing IVF/ICSI treatment outcomes: A prospective cohort study

BACKGROUND

Previous epidemiology studies reported that heavy metal/metalloid exposure is associated with the impairment of semen quality. However, it is still not clear whether the in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatment outcome will be affected after the heavy metal/metalloid exposure of the male partners.

METHODS

A prospective cohort study with a 2-year followed-up was conducted in a tertiary IVF center. A total of 111 couples undergoing IVF/ICSI treatment were initially recruited from November 2015 to November 2016. Male blood concentrations of heavy metal/metalloid including Ca, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Mo, Cd, Hg, and Pb were measured by inductively coupled plasma mass spectrometry, and the lab and pregnancy outcome data were followed up. The associations between male blood heavy metal/metalloid concentration and the clinical outcomes were analyzed by Poisson regression analysis.

RESULTS

Our results showed that none of the heavy metal/metalloid of male partners we investigated are significantly associated with the oocyte fertilization and good embryo (P ≥ 0.05); however, antral follicle count (AFC) was a protective factor for the oocyte fertilization (RR: 1.07, 95 % CI: 1.04-1.10). The blood Fe concentration of the male partner was positively associated (P < 0.05) with pregnancy in the first fresh cycle (RR:170.93, 95 % CI: 4.13-7082.04), cumulative pregnancy (RR: 23.61, 95 % CI: 3.25-171.64) and cumulative live birth (RR: 36.42, 95 % CI: 1.21-1092.54). In the first frozen embryo cycles, pregnancy was significantly associated (P < 0.05) with the blood Mn (RR: 0.01, 95 % CI:0.00-0.11) and Se concentration (RR: 0.01, 95 % CI:8.25 E-5-0.47) and female age (RR: 0.86, 95 % CI:0.75-0.99); live birth was significantly associated (P < 0.05) with the blood Mn concentration (RR: 0.00, 95 % CI: 1.14E-7-0.51).

CONCLUSIONS

Our results suggested that the higher male blood Fe concentration was positively associated with pregnancy in the fresh embryo transfer cycle, cumulative pregnancy, and cumulative live birth, whereas the higher male blood Mn and Se concentration were associated with lower chance of pregnancy and live birth in the frozen embryo transfer cycle. However, the underline mechanism of this finding still needs further investigation.

Research into the Association of Cadmium and Manganese Excretion with Thyroid Function and Behavioral Areas in Adolescents with Autism Spectrum Disorders

Thyroid dysfunction and toxic metal exposure have been linked to the increased risk of autism spectrum disorders (ASD); however, the relationship between those factors remains unclear. We aimed to evaluate the relationship between the serum level of hormones, namely thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), and urinary cadmium (U-Cd) and urinary manganese (U-Mn), in patients with ASD. The study group consisted of 129 adolescents with ASD, and the control group consisted of 86 healthy persons. Ion chromatography with spectrophotometric detection (IC-UV/ViS) was used to quantitatively determine Cd and Mn in all 24-h urine samples. These results indicate that severity of certain symptoms in autism is associated with thyroid function. Correlation analysis between Childhood Autism Rating Scale (CARS) results and the content of both U-Mn and U-Cd as well as fT3, fT4 and TSH values in ASD patients showed significantly positive correlation of CARS7 (visual reaction) with fT3 and fT4 and a negative correlation with TSH for the whole study group. In the group of adolescents over 14 years of age, it was also observed that CARS10 (anxiety reaction) negatively correlates with serum TSH levels, and among younger individuals, CARS9 (near receptor responsiveness, taste, smell) positively correlates with TSH.

Tobacco Smoke Exposure and Urinary Cadmium in Women from Northern Mexico

Cadmium (Cd), a carcinogenic metal also related to reproductive and cardiovascular diseases, is contained in tobacco and elevated concentrations of it in humans have been consistently associated with first-hand tobacco smoke; however, there is scarce and inconclusive evidence of the relationship between Cd and secondhand smoke (SHS) exposure. Our aim was to evaluate the association between exposure to tobacco, both active and SHS, with urinary Cd concentrations in Mexican women. In a cross-sectional analysis that included 998 women living in northern Mexico, we measured the concentration of creatinine-adjusted urinary Cd (µg-cadmium/g-creatinine) using inductively coupled plasma triple quadrupole (ICP-QQQ) in tandem mass spectrometry mode (MS/MS). We gathered tobacco smoking information through an in-person interview and formed seven groups: non-smokers without SHS exposure; non-smokers with SHS exposure; ex-smokers without SHS exposure <1 year of quitting; ex-smokers without SHS exposure ≥1 year of quitting, ex-smokers with SHS exposure <1 year of quitting; ex-smokers with SHS exposure ≥1 year of quitting and current smokers. The interview also yielded sociodemographic characteristics. We used linear multivariable regression models to estimate the association between Cd concentrations and tobacco smoke exposure. Compared to non-smokers without SHS exposure, we found higher Cd concentrations in ex-smokers with SHS exposure <1 year of quitting and current smokers (adjusted geometric means 0.51 vs. 1.01 and 0.69 µg-cadmium/g-creatinine, respectively). Our results do not support a conclusion that SHS exposure is a source of Cd body burden.

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.

Associations between blood metal/ metalloid concentration and human semen quality and sperm function: A cross-sectional study in Hong Kong

BACKGROUND

The association between metal/metalloid exposure on human sperm quality is still inconclusive. There is a lack of data on the effect of metal/metalloid on sperm function.

METHODS

The aim of this study was to clarify the association between blood metal/metalloid concentration and traditional and functional sperm parameters, the blood concentration of Pb, Hg, Cd, As, Ni, Mo, Zn, Cu, Se, Fe, Mg, Cr and Ca of 288 men in Hong Kong were assessed by inductively coupled plasma-mass spectrometry, and sperm parameters including sperm concentration, motility, morphology, vitality, total sperm count, total motile sperm count, sperm DNA fragmentation and sperm acrosome reaction were measured. Demographic and lifestyle questionnaires were also provided for all participants. Multivariable linear regression analysis was performed to test the association between blood metal/ metalloid concentration and semen parameters after adjusting for relevant confounding variables.

RESULTS

The results showed that moderate to high level of blood Pb concentration (>27.19 μg/L) appeared to be negatively associated with sperm morphology (P < 0.05); high level of blood Cd concentration (>1.44 μg/L) was negatively associated with sperm acrosome reaction (P < 0.05); Mo was positively associated with semen volume (P < 0.05), however, high level of blood Mo concentration (>13.52 μg/L) was negatively associated with sperm vitality (P < 0.05); high level of blood Zn concentration (>6.20 mg/L) was positively associated with sperm vitality (P < 0.05); moderate level of blood Fe concentration (526.89-566.63 mg/L) was positively associated with sperm acrosome reaction (P < 0.05); moderate level of blood Ca concentration (55.92-66.10 mg/L) was positively associated with semen volume (P < 0.05); however, lower level of blood Ca concentration (45.90-55.92 mg/L) was negatively associated with sperm morphology (P < 0.05).

CONCLUSIONS

Our results suggested that the sperm function could be affected by blood Cd and Fe concentration and traditional sperm parameters could be affected by blood concentration of Mo, Zn, Pb and Ca.

Assessment of the variability of urinary cadmium for general adults

Cadmium (Cd) exposure has become a growing public health issue and the level of urinary Cd is commonly used as the internal biomarker of overall Cd exposure. There has been raised a concern whether the level of Cd in a single spot urine actually reflects individual internal exposure over a long-term period. We aimed to examine the variability of urinary Cd levels over three years. Levels of urinary Cd were determined repeatedly in 2238 general adults during a follow-up of three-year from a community-based prospective study. We estimated the intra-class correlation coefficients (ICCs) of urinary Cd level over three years using the three-level random-effects mixed models to assess their variations. We found that the Pearson correlations for urinary Cd over three years were 0.521 for uncorrected Cd, 0.632 for creatinine (Cr)-corrected Cd, and 0.551 for specific gravity (SG)-corrected Cd, respectively (all P < 0.001). Moderate reproducibility was obtained for urinary Cd over three years, where ICCs of the three methods all exceeded 0.50. Of note, Cr-corrected urinary Cd levels achieved high reproducibility [0.773, 95%CI (0.750-0.794)]. Additionally, positive dose-response associations of smoking amount with Cr-corrected urinary Cd level were observed (P trend <0.05). Our findings suggest that Cr-corrected urinary Cd level in a single measurement was a credible biomarker for the relatively long-term levels of urinary Cd in the general population and cigarette smoking plays a part of urinary Cd exposure.

Low-Level Cadmium Exposure and Atherosclerosis

PURPOSE OF REVIEW

Cadmium has been recognized as a potential risk factor for cardiovascular disease (CVD). We present a review of cadmium toxicity, its effect on cellular activities, and a summary of reported association between environmental cadmium exposure and CVD. We also discuss the possible therapeutic benefit of cadmium chelation.

RECENT FINDINGS

Experimental data suggest that cadmium affects several signaling pathways which may lead to endothelial dysfunction and vascular tissue damage, promoting atherosclerosis. This is further supported by epidemiological studies that have shown an association of even low-level cadmium exposure with an increased risk of clinical cardiovascular events. The Trial to Assess Chelation Therapy (TACT) provided inferential evidence for the cardiovascular benefit of treating toxic metal burden. However, at the present time, there is no direct evidence, but suggestive findings from clinical trials indicating that removal of cadmium from body stores may be associated with improved cardiovascular outcomes. An evolving body of evidence supports environmental cadmium exposure as a pro-atherosclerosis risk factor in CVD; however, the mechanisms for the proatherogenic effect of cadmium are still not completely understood. Further studies in translational toxicology are needed to fill the knowledge gaps regarding the molecular mechanisms of cadmium toxicity and the promotion of atherosclerosis.

Distribution and emissions of trace elements in coal-fired power plants after ultra-low emission retrofitting

Various hazardous trace elements emitted from anthropogenic activities are attracting increasing public awareness. This study comprehensively explored the distribution and emissions of trace elements in coal-fired power plants (CFPPs) after ultra-low emission retrofitting by conducting field experiments, literature surveys, and model calculations. High levels of volatile Hg and semi-volatile As/Pb were mainly observed in fly ash and gypsum (96.6%-98.5%), while the proportion of non-volatile Cr in bottom ash was 9.23%. The Hg and As/Pb removal efficiencies were remarkably improved by ultra-low emission retrofitting, increasing by 5.67% and 2.08%/2.63%, respectively. However, ULE retrofitting only slightly affected (0.17%) non-volatile elements. These improvements were mainly attributed to the low-low-temperature electrostatic precipitator. Owing to the enhanced particle-capturing efficiencies, the concentrations of trace elements in the emitted gas of the tested CFPPs were low, ranging from 0.21-1.50 μg/m³, but accounted for a high proportion of the gas phase (61.8%-100%). Based on the national database of coal quality and their behaviour in CFPPs, we found that most of the concentrations of trace elements emitted from Chinese CFPPs were significantly lower than the internationally existing emission limits. However, owing to the skewed distribution characteristics of the emitted concentrations, we suggest issuing or revising the corresponding emission limits and improving the control of intense trace element pollution in China.

Refinement of health-based guidance values for cadmium in the French population based on modelling

In France, part of the population is overexposed to cadmium by the diet. In our work, we first revised the tolerable daily intake (TDI) of 0.36 μg Cd.kg bw.d.^-1 proposed by the European Food Safety Authority (EFSA), derived from effects on kidneys and based on the critical urinary Cd concentration of 1.0 μg Cd.g^-1 creatinine for humans. After reviewing the epidemiological data on Cd toxicity published after 2011, bone effects were selected as the critical effects. Body burden data of 0.5 μg.g^-1 creatinine was chosen for the critical threshold for human urinary cadmium concentrations. To be used for the derivation of the new oral toxicological reference value, we used a modified physiologically based pharmacokinetic model (PBPK). The reverse calculation on the PBPK model gave a TDI of 0.35 μg Cd.kg bw^-1.day^-1. This TDI is compatible with a urinary Cd concentrations not exceeding 0.5 μg Cd.g^-1 creatinine, in a 60 year-old adult, assuming that ingestion is the only source of exposure to Cd at 60 years. After implementing the PBPK model with French physiological data, Cd biological reference values as a function of age were modelled so as to remain below the revised health-based guidance values.

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.

Association of urinary cadmium, circulating fatty acids, and risk of gestational diabetes mellitus: A nested case-control study in China

BACKGROUND

Previous studies have observed that cadmium (Cd) exposure of pregnant women was associated with increased risk of gestational diabetes mellitus (GDM). However, the potential mechanism still remains unclear. In addition, various animal studies have suggested that Cd exposure could affect fatty acids (FAs) metabolism, but data on humans are scant.

OBJECTIVES

We conducted a nested case-control study to investigate the associations of urinary Cd concentrations with levels of circulating FAs and risk of GDM in pregnant women, and further to examine the role of FAs in mediating the relationship between Cd exposure and risk of GDM.

METHODS

A total of 305 GDM cases were matched to 305 controls on pregnant women's age (±2 years) and infant's gender from a birth cohort study conducted in Wuhan, China. Urinary Cd concentrations and levels of plasma FAs between 10 and 16 gestational weeks were measured using inductively coupled plasma mass spectrometry and gas chromatography-mass spectrometry, respectively. Conditional logistic regressions models were used to estimate the associations of Cd concentrations and levels of FAs with the risk of GDM. Multiple linear regression models were applied to estimate the associations between Cd concentrations and levels of FAs. Mediation analysis was used to assess the mediating role of FAs in the association of Cd with the risk of GDM.

RESULTS

Urinary concentrations of Cd in cases (median: 0.69 μg/L) were significantly higher than controls (median: 0.59 μg/L, P < 0.05). Cd concentrations were positively associated with the risk of GDM (P_trend = 0.003). Compared to the first tertile of Cd, the adjusted odds ratios (95% confidence intervals) of GDM risk were 2.08 (1.29, 3.36) for the second tertile and 2.09 (1.32, 3.33) for the third tertile. Cd concentrations were positively correlated with levels of eicosadienoic acid and arachidonic acid/eicosapentaenoic acid ratio, but negatively correlated with levels of stearic acid, eicosapentaenoic acid, total odd-chain saturated fatty acids, total n-3 polyunsaturated fatty acids (PUFAs), and n-3 PUFAs/n-6 PUFAs ratio. We did not observe evidence that the association of Cd exposure and risk of GDM was mediated through FAs.

CONCLUSIONS

Our findings confirmed the association of higher Cd exposure with increased risk of GDM in pregnant women, and provided forceful epidemiological evidence for the relation of Cd concentrations and levels of FAs.

The Source and Pathophysiologic Significance of Excreted Cadmium

In theory, the identification of the source of excreted cadmium (Cd) might elucidate the pathogenesis of Cd-induced chronic kidney disease (CKD). With that possibility in mind, we studied Thai subjects with low, moderate, and high Cd exposure. We measured urine concentrations of Cd, ([Cd]_u); N-acetyl-β-d-glucosaminidase, a marker of cellular damage ([NAG]_u); and β₂-microglobulin, an indicator of reabsorptive dysfunction ([β₂MG]_u). To relate excretion rates of these substances to existing nephron mass, we normalized the rates to creatinine clearance, an approximation of the glomerular filtration rate (GFR) (E_Cd/C_cr, E_NAG/C_cr, and E_β2MG/C_cr). To link the loss of intact nephrons to Cd-induced tubular injury, we examined linear and quadratic regressions of estimated GFR (eGFR) on E_Cd/C_cr, eGFR on E_NAG/C_cr, and E_NAG/C_cr on E_Cd/C_cr. Estimated GFR varied inversely with both ratios, and E_NAG/C_cr varied directly with E_Cd/C_cr. Linear and quadratic regressions of E_β2MG/C_cr on E_Cd/C_cr and E_NAG/C_cr were significant in moderate and high Cd-exposure groups. The association of E_NAG/C_cr with E_Cd/C_cr implies that both ratios depicted cellular damage per surviving nephron. Consequently, we infer that excreted Cd emanated from injured tubular cells, and we attribute the reduction of eGFR to the injury. We suggest that E_Cd/C_cr, E_NAG/C_cr, and eGFR were associated with one another because each parameter was determined by the tubular burden of Cd.

Biomarkers of cadmium, lead and mercury exposure in relation with early biomarkers of renal dysfunction and diabetes: Results from a pilot study among aging Canadians

Cadmium (Cd), lead (Pb) and mercury (Hg) are known nephrotoxicants that have been associated with the risk of developing type-2 diabetes (T2D). The aim of this pilot study was to explore relations between biomarkers of Cd, Pb and Hg exposure, early urinary biomarkers of renal dysfunction (kidney-injured molecule-1 (KIM-1), N-acetylglucosaminidase and retinol-binding protein (RBP)) and plasma biomarkers deemed predictive of the risk of developing T2D (adiponectin, leptin, branched-chain and aromatic amino acids), among 70 participants (age range: (46-87 yrs)) from the Canadian Longitudinal Study on Aging (CLSA) with normal glycemic control (glycated haemoglobin ≤ 6.5%) in all but four of them. Significant (p < 0.05) Spearman correlation coefficients were obtained between: plasma adiponectin and RBP (r = 0.42), urinary Cd (r = 0.32), blood Cd (r = 0.36); KIM-1 and CdU (r = 0.33) as well as HgU (r = 0.37); RBP and isoleucine (r = -0.28), leucine (r = -0.33), tyrosine (r = -0.3) and valine (r = -0.44); CdU and isoleucine and valine (r = -0.27 for both). Multiple linear regression analyses showed that some T2D-related biomarkers are confounders of associations between RBP and Hg or Cd biomarkers. Path analyses support a mediating effect of adiponectin on the relation between urinary Cd and RBP. Concluding, this pilot study originally investigated a comprehensive set of biomarkers on complex interactions between toxic metal exposure, renal function and T2D in a group of aging Canadians. Its findings warrant further investigation of longitudinal data in a greater number of participants.

The association between cumulative cadmium intake and osteoporosis and risk of fracture in a Chinese population

Bone is one of the target organs for cadmium toxicity. However, few studies have shown the association between cumulative cadmium intake and prevalence of osteoporosis and bone fracture. In the present study, we evaluated the association between cumulative cadmium intake and osteoporosis and risk of fracture in a Chinese population. A total of 790 subjects (488 women and 302 men) living in a control area and two cadmium-polluted areas were included. The cumulative cadmium intake was estimated by a food survey. The bone mineral density was determined by using single-photon absorptiometry. The cumulative cadmium intakes were 0.48, 2.14, and 11.00 g for men, and 0.42, 2.11, and 11.12 g in women in control, and moderately and heavily polluted areas, respectively. In women, the odds ratios (ORs) of subjects with a cadmium intake between 2.21 and 10.63 g and >10.63 g were 1.30 (95% CI: 0.58-2.94) and 2.36 (95% CI: 1.14-5.16), compared with those with a cadmium intake < 0.58 g after adjusting to the confounders for osteoporosis. The ORs of subjects with a cadmium intake >10.63 g were 2.34 (95% CI: 1.23-4.38) for all of the women and 2.62 (95% CI: 1.02-5.58) in women ≥ 60 years old, compared with those with a cadmium intake <10.63 g after adjusting to the confounders for bone fractures. In men, similar trends were observed, but no statistical significance was found. In addition, those subjects with renal tubular dysfunction showed high risk of bone fracture. Our results indicate that a high level of cumulative cadmium intake is associated with an increased rate of osteoporosis and fractures among women.

An interventional study of rice for reducing cadmium exposure in a Chinese industrial town

BACKGROUND

Reducing cadmium (Cd) exposure in Cd-polluted areas in Asia is urgently needed given the toxic effects of Cd. The short-term and long-term benefits of lowering Cd exposure are unknown because of its long half-life in the body.

OBJECTIVES

We aimed to investigate whether an intervention with low-Cd rice in a contaminated area of China reduced urinary Cd (UCd) levels and improved blood pressure and kidney function outcomes compared to no-intervention in consumers of high-Cd rice in the same region.

METHODS

106 non-smoking subjects were divided into three treatment groups: the intervention group (replacing homegrown high-Cd rice with market low-Cd rice, n = 34), the non-intervention group (continue eating high-Cd rice, n = 36) and the control group (continued eating low-Cd rice they have been eating for years, n = 36). The intervention period lasted for almost 8 months, during which participants were visited on up to 4 occasions and UCd, systolic and diastolic blood pressure (SBP, DBP), kidney function biomarkers (β2-microglobulin and N-acetyl-β-D-glucosaminidase) were measured.

RESULTS

After 3 months, the geometric mean UCd in the intervention (Int) group decreased significantly by 0.32 μg/g (p = 0.007), while changes were not significant in the non-intervention (non-Int) group (0.13 μg/g, p = 0.95) or the control group (-0.01 μg/g, p = 0.52). UCd in the Int group remained lower than in the non-Int group but higher than in the Control group through the end of follow up. DBP in the Int group decreased significantly from 80 mm Hg at month three (p = 0.03) and stayed around 74 mm Hg for the remainder of the study. SBP also decreased in the Int group but with variations similar to those observed in the other two groups. The two kidney biomarkers showed variations without a clear pattern.

CONCLUSION

This study suggested that UCd reflected both short-term (<3 months) and long-term Cd exposure. In addition, the low-Cd rice intervention showed initial benefits in lowering blood pressure levels, especially DBP, but not kidney biomarkers.

Associations of renal function with urinary excretion of metals: Evidence from NHANES 2003-2012

BACKGROUND

Urinary metals are considered measures of long-term exposures of metals, such as cadmium (Cd). Some studies indicate reduced renal function may affect the urinary excretion of several metals in general population making assessments difficult.

OBJECTIVES

To examine whether reduced renal function is associated with reduced urinary excretion of 12 metals or their metabolites and, in turn, an underestimated measure of Cd in general population.

METHODS

We conducted analyses using data from the National Health and Nutrition Examination Survey (NHANES) 2003-2012. Multiple linear regression models were used to examine the associations between urinary metal levels and estimated glomerular filtration rate (eGFR). Restricted cubic spline regression models were used to evaluate the nonlinearity.

RESULTS

Urinary metal levels significantly increased (p < 0.001) with increasing eGFR, except for antimony (p = 0.172). Urinary levels of arsenic, dimethylarsonic acid, cobalt, molybdenum and tungsten increased linearly with eGFR, while Cd, lead, mercury, barium, cesium and thallium increased nonlinearly (p < 0.001) with eGFR. Based on a restricted cubic spline regression model, we found, corresponding to a fixed blood Cd adverse cutpoint of 5 μg/L, predicted urinary Cd cutpoints substantially varied from 0.78-1.21 μg/g for urinary Cd between those aged <40 years and who had chronic kidney disease and those aged 60 years or over with normal renal function, respectively.

CONCLUSION

Reduced renal function is associated with reduced urinary metals; and associations are also observed across the eGFR range not just in the reduced range. Urinary abnormal cutpoints of metals are likely dependent on eGFR and age. The associations between urinary exposure of metals and disease risk are likely underestimated without considering the modifying effect of renal function.

The references level of cadmium intake for renal dysfunction in a Chinese population

Recent several studies indicated that a more restrictive dietary intake guideline for cadmium should be made for sufficient health protection. In the present study, we showed the references level of food cadmium intake (FCd) and total cadmium intake (TCd) for renal dysfunction by using benchmark dose (BMD) approach. 342 subjects living in a control and a cadmium polluted area were included in this study. The FCd, TCd and cadmium in urine (UCd) and blood (BCd) were calculated or determined. Urinary β₂Microglobulin (UBMG) was determined as indicator of renal function. The median FCd, TCd, UCd and BCd were 1.4 g, 1.4 g, 3.1 μg/g creatinine(cr) and 1.3 μg/L in control and 3.3 g, 3.6 g, 13.5 μg/g cr and 12.1 μg/L in polluted area. The 95% lower confidence bounds of BMD (BMDLs) of FCd for renal dysfunction were 1.36-1.55 g (BMR = 10%) and 0.88-1.11 g (BMR = 5%). The BMDLs of TCd were 1.29-1.46 g (BMR = 10%) and 0.73-0.95 g (BMR = 5%). FCd and TCd are valuable markers for the predication of renal dysfunction induced by cadmium. The BMDLs of FCd were close to previous report in Japan and the BMDLs of TCd were lower than the critical standard previously reported, in particular at BMR of 5% which can be interpreted as representing the influence of smoking.

The association between dietary cadmium exposure and renal dysfunction - the benchmark dose estimation of reference levels: the ChinaCad study

The tolerable dietary intake of cadmium was recommended at provisional tolerable monthly intake of 25 μg kg^-1 body weight. However, several studies indicated that this tolerable level should be re-evaluated for sufficient health protection. In this study, we show the reference levels of dietary cadmium intake for renal dysfunction by using a benchmark dose (BMD) approach. A total of 790 subjects (302 men and 488 women) living in control and cadmium-polluted areas were included. The dietary cadmium intake was estimated by a food survey. Blood cadmium, urinary cadmium and renal function markers (microalbuminuria, N-acetyl-β-d-glucosaminidase [NAG] and its isoform B [NAGB], β₂ -microglobulin and retinol binding protein) in urine were measured. We calculated the 95% lower confidence bounds of BMD (BMDLs) of cumulative cadmium intake. In control and two polluted areas, the median cumulative cadmium intake was 0.5, 2.1 and 11.1 g. The odds ratio of the intermediate (1.0-3.0 g), second highest (3.0-11.0 g) and the highest cumulative cadmium intake (>11.0 g) compared with the lowest cumulative cadmium intake (<1.0 g) were 2.8 (95% CI: 1.4-5.8), 8.1 (95% CI: 3.8-17.2) and 11.4 (95% CI: 6.5-26.4) for urinary NAG and 6.6 (95% CI: 3.2-13.8), 14.8 (95% CI: 6.8-32.2) and 22.5 (95% CI: 10.7-47.5) for urinary NAGB. The BMDLs of cumulative cadmium intake were 1.1-1.2 g (benchmark response [BMR] = 5%) for urinary NAG, and were 0.7-0.9 g (BMR = 5%) for urinary NAGB, and were 1.3-1.4 g (BMR = 5%) for urinary β₂ -microglobulin. The BMDLs of cumulative cadmium intake in a Chinese population were lower than the critical standard previously reported. Further evaluations are needed for sufficient health protection.

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.

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.

Blood and urine cadmium concentrations and walking speed in middle-aged and older U.S. adults

Reduced physical performance is an important feature of aging, and walking speed is a valid measure of physical performance and mobility in older adults. Previous epidemiological studies suggest that cadmium exposure, even at low environmental levels, may contribute to vascular, musculoskeletal, and cognitive dysfunction, which may all be associated with reductions in physical performance. To this end, we investigated the associations of blood and urine cadmium concentrations with walking speed in middle-aged and older adults in the U.S. general population. We studied U.S. adults from the National Health and Nutrition Examination Survey 1999 to 2002 who were ≥50 years of age, who had determinations of cadmium in blood or in urine, and who had measurements of the time taken to walk 20 feet. Walking speed (ft/sec) was computed as walked distance (20 ft) divided by measured time to walk (in seconds). The weighted geometric means of blood and urine cadmium were 0.49 [95% confidence interval (CI): 0.47, 0.52] μg/L and 0.37 (95% CI: 0.34, 0.42) ng/mL, respectively. After adjusting for sociodemographic, anthropometric, health-related behavioral, and clinical risk factors and inflammation markers, the highest (vs. lowest) quintile of blood cadmium was associated with a 0.18 (95% CI: 0.10, 0.25) ft/sec reduction in walking speed (p-Trend <0.001). No association was observed for urine cadmium levels with walking speed. Cadmium concentrations in blood, but not in urine, were associated with slower gait speed. Our findings add to the growing volume of evidence supporting cadmium's toxicity even at low levels of exposure.

The physiological determinants of low-level urine cadmium: an assessment in a cross-sectional study among schoolchildren

BACKGROUND

Recent studies in children have reported associations of urinary cadmium (U-Cd), used as biomarker of Cd body burden, with renal dysfunction, retarded growth and impaired cognitive development in children. Little is known, however, about factors influencing U-Cd in children and likely to act as confounders.

METHODS

In a cross-sectional study involving 249 schoolchildren (mean age, 5.72 years; 138 boys), we measured the urine concentrations of cadmium, zinc, lead, albumin, alpha₁-microglobulin (A1M), retinol-binding protein, β₂-microglobulin and club cell protein (CC16). Determinants of U-Cd expressed per creatinine or adjusted to specific gravity were identified by multiple regression analyses.

RESULTS

Girls and boys had similar median concentrations of U-Cd (0.22 and 0.24 μg/L, 0.33 and 0.35 μg/g creatinine, respectively). When models were run without including creatinine or specific gravity among independent variables, urinary zinc, urinary A1M and age emerged as the strongest predictors of U-Cd expressed per g creatinine or adjusted to SG. When adding creatinine among predictors, urinary creatinine emerged as an additional strong predictor correlating negatively with U-Cd per g creatinine. This strong residual influence of diuresis, not seen when adding specific gravity among predictors, linked U-Cd to U-A1M or U-CC16 through secondary associations mimicking those induced by Cd nephrotoxity.

CONCLUSIONS

In young children U-Cd largely varies with diuresis, zinc metabolism and urinary A1M. These physiological determinants, unrelated to Cd body burden, may confound the child renal and developmental outcomes associated with low-level U-Cd.

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.

Cadmium and Alzheimer's disease mortality in U.S. adults: Updated evidence with a urinary biomarker and extended follow-up time

Cadmium has been linked to impaired cognitive function in adults and may cause behavioral, physiological and molecular abnormalities characteristic of Alzheimer's disease (AD) in animals. Evidence linking cadmium and AD in humans is limited, but supportive. In the most recent epidemiologic study, blood cadmium in U.S. adults was positively associated with elevated AD mortality 7-13 years later. The association between urinary cadmium - an arguably more appropriate biomarker for studying chronic diseases - and AD mortality has not yet been explored. Further study of cadmium and AD mortality in an independent population, with longer follow-up, and stratified by sex is also needed. We sought to answer these questions using the U.S. National Health and Nutrition Examination Survey (NHANES) (1999-2006 cycles) and NHANES III (interviews in 1988-1994) datasets, separately linked to AD mortality as of 2011. We used survey-weighted Cox regression models predicting age at AD death and adjusted for race/ethnicity, sex, smoking status, education and urinary creatinine. An interquartile range (IQR; IQR=0.51ng/mL) increase in urinary cadmium was associated with 58% higher rate of AD mortality (hazard ratio (HR)=1.58, 95% CI: 1.20, 2.09. p-value=0.0009, mean follow-up: 7.5 years) in NHANES 1999-2006 participants. In contrast, in NHANES III participants, an IQR (IQR=0.78ng/mL) increase in urinary cadmium was not associated with AD mortality (HR=0.85, 95% CI: 0.63, 1.17, p-value=0.31, mean follow-up: 13 years). Also in the NHANES III sample however, when the maximum follow-up time was restricted to 12.7 years (i.e. the same as NHANES 1999-2006 participants) and urinary creatinine adjustments were not made, urinary cadmium was associated with elevated AD mortality (HR=1.11, 95% CI: 1.02, 1.20, p-value=0.0086). Our study partially supported an association between cadmium and AD mortality, but the sensitivity of results to follow-up time and creatinine adjustments necessitate cautious interpretation of the association. Further studies, particularly those on toxicological mechanisms, are required to fully understand the nature of the "cadmium-AD mortality" association.

Applying Cadmium Relative Bioavailability to Assess Dietary Intake from Rice to Predict Cadmium Urinary Excretion in Nonsmokers

Dietary Cd intake is often estimated without considering Cd bioavailability. Measured urinary Cd for a cohort of 119 nonsmokers with rice as a staple was compared to predicted values from rice-Cd intake with and without considering Cd relative bioavailability (RBA) in rice based on a steady state mouse kidney bioassay and toxicokinetic model. The geometric mean (GM) of urinary Cd and β₂-microglobulin was 1.08 and 234 μg g^-1 creatinine. Applying Cd-RBA in foods to aggregate Cd intake (41.5 ± 12.4, 48.0 ± 9.3, 48.8 ± 21.3% for rice, wheat, and vegetables), rice was the largest contributor (71%). For 63 participants providing paired urine and rice samples, the predicted GM of urinary Cd at 4.14 μg g^-1 based on total Cd in rice was 3.5 times that of measured value at 1.20 μg g^-1, while incorporating Cd-RBA to assess rice-Cd intake made the two closer with GM at 1.07 μg g^-1. The cohort findings were extended to a national scale, with urinary Cd for nonsmokers from rice Cd intake was mapped at province/city levels after considering rice Cd-RBA. Therefore, incorporating Cd bioavailability to assess dietary Cd intake is a valuable tool to accurately estimate human Cd exposure and associated health risk.

Temporal variability of urinary cadmium in spot urine samples and first morning voids

Cadmium is a carcinogenic heavy metal. Urinary levels of cadmium are considered to be an indicator of long-term body burden, as cadmium accumulates in the kidneys and has a half-life of at least 10 years. However, the temporal stability of the biomarker in urine samples from a non-occupationally exposed population has not been rigorously established. We used repeated measurements of urinary cadmium (U-Cd) in spot urine samples and first morning voids from two separate cohorts, to assess the temporal stability of the samples. Urine samples from two cohorts including individuals of both sexes were measured for cadmium and creatinine. The first cohort (Home Observation of Perinatal Exposure (HOPE)) consisted of 21 never-smokers, who provided four first morning urine samples 2-5 days apart, and one additional sample roughly 1 month later. The second cohort (World Trade Center-Health Program (WTC-HP)) consisted of 78 individuals, including 52 never-smokers, 22 former smokers and 4 current smokers, who provided 2 spot urine samples 6 months apart, on average. Intra-class correlation was computed for groups of replicates from each individual to assess temporal variability. The median creatinine-adjusted U-Cd level (0.19 and 0.21 μg/g in the HOPE and WTC-HP, respectively) was similar to levels recorded in the United States by the National Health and Nutrition Examination Survey. The intra-class correlation (ICC) was high (0.76 and 0.78 for HOPE and WTC-HP, respectively) and similar between cohorts, irrespective of whether samples were collected days or months apart. Both single spot or first morning urine cadmium samples show good to excellent reproducibility in low-exposure populations.

Exploring the Association Between Demographics, SLC30A8 Genotype, and Human Islet Content of Zinc, Cadmium, Copper, Iron, Manganese and Nickel

A widely prevalent single nucleotide polymorphism, rs13266634 in the SLC30A8 gene encoding the zinc transporter ZnT8, is associated with an increased risk for T2DM. ZnT8 is mostly expressed in pancreatic insulin-producing islets of Langerhans. The effect of this variant on the divalent metal profile in human islets is unknown. Additionally, essential and non-essential divalent metal content of human islets under normal environmental exposure conditions has not been described. We therefore examined the correlation of zinc and other divalent metals in human islets with rs13266634 genotype and demographic characteristics. We found that the diabetes risk genotype C/C at rs13266634 is associated with higher islet Zn concentration (C/C genotype: 16792 ± 1607, n = 22, C/T genotype: 11221 ± 1245, n = 18 T/T genotype: 11543 ± 6054, n = 3, all values expressed as mean nmol/g protein ± standard error of the mean, p = 0.040 by ANOVA). A positive correlation between islet cadmium content and both age (p = 0.048, R2 = 0.09) and female gender (women: 36.88 ± 4.11 vs men: 21.22 ± 3.65 nmol/g protein, p = 0.007) was observed. Our results suggest that the T2DM risk allele C is associated with higher islet zinc levels and support prior evidence of cadmium's higher bioavailability in women and its long tissue half-life.

Factors affecting the variability in the observed levels of cadmium in blood and urine among former and current smokers aged 20-64 and ≥ 65years

Data from National Health and Nutrition Examination Survey for 1999-2012 were used to evaluate factors that affect observed levels of blood cadmium (BCd) and urine cadmium (UCd) among former and current smokers aged 20-64 and ≥65 years. Adjusted levels (AGM) for BCd and UCd were higher among females as compared to males. The order of AGM for BCd by race/ethnicity for 20-64 years old was non-Hispanic white (NHW) < non-Hispanic black (NHB) and NHW > NHB for ≥65 years old. The order of AGMs for UCd for 20-64-year-old current smokers was NHW > NHB and NHW > NHB for former smokers. For 20-64-year-old current smokers, exposure to environmental tobacco smoke at home was associated with higher levels of BCd. Levels of both UCd and BCd increased with age, but the rate of increase was as much as seven times higher among ≥65 years old than 20-64 years old. For current smokers, the number of cigarettes smoked inside home was positively associated with the levels of BCd. For current smokers aged 20-64 years, the number of cigarettes smoked inside home was positively associated with the levels of UCd (p < 0.01), and the number of cigarettes smoked every day on the days they were smoked was also positively associated with the levels of UCd (p < 0.01). Among former smokers, levels of both UCd and BCd were positively associated (p < 0.1) with the number of cigarettes smoked per day at the time of quitting smoking and negatively associated with the time since smoking was quitted (p < 0.01).

Prevalence and associated demographic characteristics of exposure to multiple metals and their species in human populations: The United States NHANES, 2007-2012

Lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) are among the top 10 pollutants of global health concern. Studies have shown that exposures to these metals produce severe adverse effects. However, the mechanisms underlying these effects, particularly joint toxicities, are poorly understood in humans. The objective of this investigation was to identify and characterize prevalent combinations of these metals and their species in the U.S. NHANES population to provide background data for future studies of potential metal interactions. Exposure was defined as urine or blood levels ≥ medians of the NHANES 2007-2012 participants ≥6 years (n = 7408). Adjusted-odds ratios (adj-OR) and 95% confidence intervals were determined for covariates (age, gender, and race/ethnicity, cotinine and body mass index). Species-specific analysis was also conducted for As and Hg including iAs (urinary arsenous acid and/or arsenic acid), met-iAs (urinary monomethylarsonic acid and/or dimethylarsinic acid), and oHg (blood methyl-mercury and/or ethyl-mercury). For combinations of As and Hg species, age- and gender-specific prevalence was determined among NHANES 2011-2012 participants (n = 2342). Data showed that approximately 49.3% of the population contained a combination of three or more metals. The most prevalent unique specific combinations were Pb/Cd/Hg/As, Pb/Cd/Hg, and Pb/Cd. Age was consistently associated with these combinations: adj-ORs ranged from 10.9 (Pb/Cd) to 11.2 (Pb/Cd/Hg/As). Race/ethnicity was significant for Pb/Cd/Hg/As. Among women of reproductive age, frequency of oHg/iAs/met-iAS and oHg/met-iAs was 22.9 and 40.3%, respectively. These findings may help prioritize efforts to assess joint toxicities and their impact on public health.

Low cadmium exposure in males and lactating females-estimation of biomarkers

BACKGROUND

Urine cadmium (Cd) and renal function biomarkers, mostly analysed in urine spot samples, are well established biomarkers of occupational exposure. Their use and associations at low environmental level are common, but have recently been questioned, particularly in terms of physiological variability and normalisation bias in the case of urine spot samples.

AIM

To determine the appropriateness of spot urine and/or blood Cd exposure biomarkers and their relationships with renal function biomarkers at low levels of exposure. To this end, we used data from Slovenian human biomonitoring program involving 1081 Slovenians (548 males, mean age 31 years; 533 lactating females, mean age 29 years; 2007-2015) who have not been exposed to Cd occupationally.

RESULTS

Geometric means (GMs) of Cd in blood and spot urine samples were 0.27ng/mL (0.28 for males and 0.33 for females) and 0.19ng/mL (0.21 for males and 0.17 for females), respectively. Differing results were obtained when contrasting normalisation by urine creatinine with specific gravity. GMs of urine albumin (Alb), alpha-1-microglobulin (A1M), N-acetyl-beta-glucosaminidase (NAG), and immunoglobulin G (IgG) were far below their upper reference limits. Statistical analysis of unnormalised or normalised urine data often yielded inconsistent and conflicting results (or trends), so association analyses with unnormalised data were taken as more valid. Relatively weak positive associations were observed between urine Cd (ng/mL) and blood Cd (β=0.11, p=0.002 for males and β=0.33, p<0.001 for females) and for females between urine NAG and blood Cd (β=0.14, p=0.04). No associations were found between other renal function biomarkers and blood Cd. Associations between Cd and renal function biomarkers in urine were stronger (p<0.05, β=0.11-0.63). Mostly, all of the associations stayed significant but weakened after normalisation for diuresis. In the case of A1M, its associations with Cd were influenced by current smoking and blood Pb in males and by pre-pregnancy smoking and blood Se in females (β up to 0.34, p<0.001). Statistical analysis of unnormalised or normalised urine data often yielded inconsistent and conflicting results (or trends), so association analyses data with unnormalised were taken as more valid.

CONCLUSIONS

The observed uncertainties introduced by urine normalisation, particularly by creatinine, confirm blood Cd as a superior low-Cd exposure biomarker versus urine Cd in cases when 24h urine is unattainable. Evidence that A1M can be positively related to Cd, smoking (current or pre-pregnancy), Pb, and Se status, points to the versatile biological functions of A1M.

Dietary predictors of urinary cadmium among pregnant women and children

BACKGROUND

Cadmium is a toxic metal with modifiable exposure sources including diet. In pregnant women and children, unique dietary habits may contribute to DCd, and the relationship of diet to overall cadmium exposure can depend on specific factors during these transitional time periods.

OBJECTIVES

This study aimed to identify and quantify food sources of DCd, describe the distribution of UCd, and determine the relationship of DCd and intake of specific foods with UCd, stratified by maternal smoking history, among pregnant women and children in a well-characterized Mexico City birth cohort.

METHODS

Our sample included 192 pregnant women (third trimester) and 223 children (7-15years). DCd was calculated using FFQ and the U.S. TDS. We also measured UCd, maternal history of smoking, and additional covariates.

RESULTS

Pregnant women and children had geometric mean UCd concentrations of 0.19±0.78μg/L and 0.14±0.60μg/L, respectively. On average, estimated daily DCd intake was 9.3±3.5μg for women and 12.2±5.4μg for children. Adjusted linear regression models showed a positive association between DCd and UCd among women (p=0.03) and children (p=0.03) without a maternal history of smoking. Intake of fruit and vegetables among women and potato consumption among children were positively associated with UCd.

CONCLUSIONS

Pregnant women and their children are exposed to cadmium at dietary and urinary levels similar to those previously reported. Higher estimated DCd for children than for women could be attributed to the different FFQs or related to dietary pattern changes between age groups. DCd contributed to UCd in those without a maternal smoking history.

Is Urinary Cadmium a Biomarker of Long-term Exposure in Humans? A Review

Cadmium is a naturally-occurring element, and humans are exposed from cigarettes, food, and industrial sources. Following exposure, cadmium accumulates in the kidney and is slowly released into the urine, usually proportionally to the levels found in the kidneys. Cadmium levels in a single spot urine sample have been considered indicative of long-term exposure to cadmium; however, such a potentially exceptional biomarker requires careful scrutiny. In this review, we report good to excellent temporal stability of urinary cadmium (intraclass correlation coefficient 0.66-0.81) regardless of spot urine or first morning void sampling. Factors such as changes in smoking habits and diseases characterized by increased excretion of proteins may produce short-term changes in urinary cadmium levels. We recommend that epidemiologists use this powerful biomarker in prospective studies stratified by smoking status, along with thoughtful consideration of additional factors that can influence renal physiology and cadmium excretion.

Human biomonitoring of heavy metals in the vicinity of non-ferrous metal plants in Ath, Belgium

BACKGROUND

A previous study revealed an environmental contamination by heavy metals in the vicinity of two non-ferrous metal plants in Ath, Belgium. The purpose of the current cross-sectional study was to estimate exposure of the population to heavy metals in the vicinity of the plants, in comparison with population living further away.

METHODS

We did a random sampling in the general population of Ath in two areas: a central area, including the plants, and a peripheral area, presumably less exposed. We quantified cadmium, lead, nickel, chromium and cobalt in blood and/or urine of children and adults in three age groups: (i) children aged 2.5 to 6 years (n = 98), (ii) children aged 7 to 11 years (n = 74), and (iii) adults aged 40 to 60 years (n = 106). We also studied subclinical health effects by quantifying retinol-binding protein and microalbuminuria, and by means of a Strengths and Difficulties Questionnaire.

RESULTS

We obtained a participation rate of 24 %. Blood lead levels were significantly higher in young children living in the central area (18.2 μg/l ; 95 % CI: 15.9-20.9) compared to the peripheral area (14.8 μg/l ; 95 % CI: 12.6-17.4). We observed no other significant mean difference in metal concentrations between the two areas. In the whole population, blood lead levels were higher in men (31.7 μg/l ; 95 % CI: 27.9-36.1) than in women (21.4 μg/l ; 95 % CI: 18.1-25.3). Urine cadmium levels were 0.06 μg/g creatinine (95 % CI: 0.05-0.07), 0.21 μg/g creatinine (95 % CI: 0.17-0.27), and 0.25 μg/g creatinine (95 % CI: 0.20-0.30) for children, men, and women, respectively.

CONCLUSIONS

Despite higher blood lead levels in young children living close to the plants, observed metal concentrations remain in the range found in other similar biomonitoring studies in the general population and are below the levels of concern for public health.

Association of cadmium in urine and blood with age in a general population with low environmental exposure

A recent study reported a nonlinear and nonmonotonic relationship between urinary cadmium (U-Cd) and age and questioned the long-held view that U-Cd is a reliable biomarker of Cd body burden at low exposure levels. In order to reassess the significance of U-Cd as biomarker of Cd body burden, we studied the lifetime trend of U-Cd as functions of diuresis in a cross-sectional study. Cadmium was measured with an inductively coupled plasma mass spectrometer (ICP-MS) for the general population taking part in the Metals and Health Survey in Jiangsu (MHSJ), China, with ages ranging from 2.8 to 86.8 years (n = 1235). Variations in U-Cd and B-Cd with age were modeled using natural cubic splines. Factors associated with U-Cd were analyzed with Pearson correlation and linear regression models. As results, nonsmoking men had peak U-Cd at approximately 60 years, after which it decreased. In nonsmoking women, U-Cd increased from 2.8 years to 50 years, then leveled off. In both genders, B-Cd increased from birth to approximately 30 years and then leveled off. U-Cd, expressed in per liter, was consistently associated with B-Cd and U-creatinine, regardless of smoking status. U-Cd and B-Cd were not significantly higher in former smokers than never smokers. Our study suggests that individual U-Cd level are correlated with B-Cd and U-creatinine, and needed to be appropriately adjusted for B-Cd and U-creatinine, when it is used for a biomarker of kidney burden of Cd.

Urinary Cadmium and Risk of Invasive Breast Cancer in the Women's Health Initiative

Cadmium is a widespread heavy metal pollutant that may act as an exogenous estrogenic hormone. Environmental cadmium exposure has been associated with risk of breast cancer in retrospective studies. We prospectively assessed the relationship between cadmium exposure, evaluated by creatinine-normalized urinary cadmium concentration, and invasive breast cancer among 12,701 postmenopausal women aged ≥50 years in a Women's Health Initiative study of bone mineral density. After a median of 13.2 years of follow-up (1993-2010), 508 cases of invasive breast cancer and 1,050 comparison women were identified for a case-cohort analysis. Multivariable Cox regression was used to calculate hazard ratios and 95% confidence intervals. Risk of breast cancer was not associated with urinary cadmium parameterized either in quartiles (comparing highest quartile with lowest, hazard ratio = 0.80, 95% confidence interval: 0.56, 1.14; P for trend = 0.20) or as a log-transformed continuous variable (per 2-fold higher urinary cadmium concentration, hazard ratio = 0.94, 95% confidence interval: 0.86, 1.03). We did not observe an association between urinary cadmium and breast cancer risk in any subgroup examined, including never smokers and women with body mass index (weight (kg)/height (m)(2)) less than 25. Results were consistent in both estrogen receptor-positive and estrogen receptor-negative tumors. Our results do not support the hypothesis that environmental cadmium exposure is associated with risk of postmenopausal breast cancer.

Confusion about Cadmium Risks: The Unrecognized Limitations of an Extrapolated Paradigm

BACKGROUND

Cadmium (Cd) risk assessment presently relies on tubular proteinuria as a critical effect and urinary Cd (U-Cd) as an index of the Cd body burden. Based on this paradigm, regulatory bodies have reached contradictory conclusions regarding the safety of Cd in food. Adding to the confusion, epidemiological studies implicate environmental Cd as a risk factor for bone, cardiovascular, and other degenerative diseases at exposure levels that are much lower than points of departure used for setting food standards.

OBJECTIVE

The objective was to examine whether the present confusion over Cd risks is not related to conceptual or methodological problems.

DISCUSSION

The cornerstone of Cd risk assessment is the assumption that U-Cd reflects the lifetime accumulation of the metal in the body. The validity of this assumption as applied to the general population has been questioned by recent studies revealing that low-level U-Cd varies widely within and between individuals depending on urinary flow, urine collection protocol, and recent exposure. There is also evidence that low-level U-Cd increases with proteinuria and essential element deficiencies, two potential confounders that might explain the multiple associations of U-Cd with common degenerative diseases. In essence, the present Cd confusion might arise from the fact that this heavy metal follows the same transport pathways as plasma proteins for its urinary excretion and the same transport pathways as essential elements for its intestinal absorption.

CONCLUSIONS

The Cd risk assessment paradigm needs to be rethought taking into consideration that low-level U-Cd is strongly influenced by renal physiology, recent exposure, and factors linked to studied outcomes.

CITATION

Bernard A. 2016. Confusion about cadmium risks: the unrecognized limitations of an extrapolated paradigm. Environ Health Perspect 124:1-5; http://dx.doi.org/10.1289/ehp.1509691.

Dietary Intake Estimates and Urinary Cadmium Levels in Danish Postmenopausal Women

BACKGROUND

Cadmium is a known carcinogen that can disrupt endocrine signalling. Cigarette smoking and food are the most common routes of non-occupational exposure to cadmium. Cadmium accumulates in the kidney and can be measured in urine, making urine cadmium (U-Cd) a biomarker of long-term exposure. However dietary-cadmium (D-Cd) intake estimates are often used as surrogate indicator of cadmium exposure in non-smoking subjects. It is therefore important to investigate the concordance between D-Cd estimates obtained with Food Frequency Questionnaires and U-Cd.

METHODS

U-Cd levels were compared with estimated dietary-cadmium (D-Cd) intake in 1764 post-menopausal women from the Danish Diet, Cancer and Health cohort. For each participant, a food frequency questionnaire, and measures of cadmium content in standard recipes were used to judge the daily intake of cadmium, normalized by daily caloric intake. Cadmium was measured by ICP-MS in spot urine sampled at baseline and normalized by urinary creatinine. Information on diet, socio-demographics and smoking were self-reported at baseline.

RESULTS

Linear regressions between U-Cd and D-Cd alone revealed minimal but significant positive correlation in never smokers (R2 = 0.0076, β = 1.5% increase per 1 ng Cd kcal(-1), p = 0.0085, n = 782), and negative correlation in current smokers (R2 = 0.0184, β = 7.1% decrease per 1 ng Cd kcal(-1) change, p = 0.0006, n = 584). In the full study population, most of the variability in U-Cd was explained by smoking status (R2 = 0.2450, n = 1764). A forward selection model revealed that the strongest predictors of U-Cd were age in never smokers (Δ R2 = 0.04), smoking duration in former smokers (Δ R2 = 0.06) and pack-years in current smokers (Δ R2 = 0.07). Food items that contributed to U-Cd were leafy vegetables and soy-based products, but explained very little of the variance in U-Cd.

CONCLUSIONS

Dietary-Cd intake estimated from food frequency questionnaires correlates only minimally with U-Cd biomarker, and its use as a Cd exposure indicator may be of limited utility in epidemiologic studies.

Association of cadmium with diabetes in middle-aged residents of abandoned metal mines: the first health effect surveillance for residents in abandoned metal mines

OBJECTIVE

The aim of this study was to determine the association between urinary cadmium (U-cd) concentration and diabetes in middle-aged Korean residents of abandoned mines using the first Health Effect Surveillance for Residents in Abandoned Metal mines (HESRAM).

METHODS

This study was cross-sectional study conducted on 719 residents between 40-70 years in 38 abandoned metal mines in Korea. Data was collected by HESRAM from 2008 to 2011. The correlation coefficient of U-cd and fasting blood glucose, odds ratio in urinary cadmium tertiles and diabetes prevalence was analyzed according to the sex category.

RESULTS

The correlation coefficient U-cd concentration and fasting blood glucose was 0.182 in male. Logistic regression analysis in male revealed a third tertile odds ratio of U-cd (2 μg/g creatinine < U-cd) while diabetes prevalence was 1.81 (95 % CI 1.05-3.12) with adjusted age, BMI, smoking and alcohol consumption, region, family income. On the other hand, the odds ratio for third tertile of U-cd (3 μg/g creatinine < U-cd) between diabetes prevalence in female was 1.39 (95 % CI 0.52-3.72) in addition to adjusted menopausal status.

CONCLUSIONS

Environmental exposure to cadmium in abandoned mine residents was associated with diabetes in male. Closed monitoring and periodic evaluation of the health effects of chronic environmental exposure on abandoned mines residents will be needed.