Benchmark dose for cadmium-induced osteoporosis in women

Metals accumulation affects bone and muscle in osteoporotic patients: A pilot study

Osteoporosis is the most common bone disease, characterized by decreased bone mineral density (BMD) and often associated to decreased muscle mass and function. Metal exposure plays a role in the pathophysiology of osteoporosis and affects also muscle quality. The aim of this study was to assess the association between metal levels in bone and muscle samples and the degeneration of these tissues. A total of 58 subjects (30 male and 28 female) was enrolled and classified in osteoporotic (OP, n = 8), osteopenic (Ope, n = 30) and healthy (CTR, n = 20) subjects, according to BMD measures. Femoral head bone samples and vastus lateralis muscle samples were collected during hip arthroplasty surgeries. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis showed increased levels of Al, Cd and Pb in OP and Ope bone tissue compared to CTR subjects (p = 0.04, p = 0.005 and p = 0.01, respectively). Whereas, increased levels of Co, Cd and Pb were measured in OP and Ope muscle tissues, compared to CTRs (p < 0.001, p = 0.02 and p = 0.01, respectively). In addition, Al, Cd and Pb levels in bone and Cd and Co levels in muscle were negatively correlated with BMD. A negative association among Co, Cd, Cr and Hg levels and muscle fibers diameter was also observed in muscle tissues. This study assessed that metal exposure can affects bone and muscle tissue quality and may contribute to the onset and progression of musculoskeletal diseases such as osteoporosis. Therefore, it is important to implement metal exposure assessment and their impact on disease development, in order to manage and prevent metal accumulation effects on bone and muscle quality.

Association between Environmental Cadmium Exposure and Osteoporosis Risk in Postmenopausal Women: A Systematic Review and Meta-Analysis

Osteoporosis is a common and serious health issue among postmenopausal women. We conducted a systematic review and meta-analysis study to determine whether environmental exposure to cadmium (Cd) is a risk factor for postmenopausal osteoporosis. A PROSPERO-registered review of the literature was performed on studies evaluating the relationship between urinary Cd (UCd) concentration, an indicator of long-term Cd exposure, and bone mineral density or osteoporosis in women aged 50 years and older. PubMed, Embase, Science Direct, Web of Science, and B-on databases were searched for articles published between 2008 and 2021. The association between UCd levels and osteoporosis risk was assessed by pooled odds ratio (OR) and 95% confidence interval (CI) using random-effect models. Ten cross-sectional studies were included in the qualitative analysis, of which five were used for meta-analysis. We separately assessed the risk of osteoporosis in women exposed to Cd at low environmental levels (n = 5895; UCd ≥ 0.5 μg/g creatinine versus UCd < 0.5 μg/g creatinine) and high environmental levels (n = 1864; UCd ≥ 5 μg/g creatinine versus UCd < 5 μg/g creatinine). The pooled OR for postmenopausal osteoporosis was 1.95 (95% CI: 1.39−2.73, p < 0.001) in the low exposure level group and 1.99 (95% CI: 1.04−3.82, p = 0.040) in the high exposure level group. This study indicates that environmental Cd exposure, even at low levels, may be a risk factor for osteoporosis in postmenopausal women. Further research based on prospective studies is needed to validate these findings.

Urinary cadmium in relation to bone damage: Cadmium exposure threshold dose and health-based guidance value estimation

Cadmium (Cd) is a widespread heavy metal with osteotoxicity, and bone mineral density (BMD) is often used as an early sensitive biomarker of bone damage. This study retrieved worldwide epidemiological studies to conduct a systematic meta-analysis to explore the association between Cd exposure and bone damage. A random effect model was used to establish the relationship between urinary Cd (U-Cd) and BMD and explore the influence of covariate factors. The benchmark dose method was used to calculate the safety threshold of U-Cd when the BMD decrease within an acceptable range. Toxicokinetic (TK) model was used to estimate the health-based guidance value (HBGV) of dietary Cd exposure based on the U-Cd threshold. The 95% lower confidence interval of benchmark dose of U-Cd derived in this study was 1.71 μg/g Cr, and the HBGV of dietary Cd exposure was determined to be 0.64 μg/kg bw/day. Gender had the greatest influence on BMD, followed by body mass index (BMI), age, and race. This study conducted a comprehensive systematic analysis of global research and was the first exploration to quantify the decreased BMD caused by Cd exposure in a large-scale population. The results provided reference for the risk assessment of Cd exposure and the formulation of dietary exposure standards.

Nomogram to Predict Cadmium-Induced Osteoporosis and Fracture in a Chinese Female Population

Cadmium exposure may increase the risk of osteoporosis. However, there is no quick method to get bone mineral density (BMD) unless dual-energy X-ray absorptiometry (DXA) examinations were performed. In the present study, we aimed to identify associated factors to osteoporosis and fracture in a Chinese female population with cadmium exposure and develop nomograms to predict the risk. A total of 488 women was included in this study. Cadmium in blood (BCd) and urine (UCd) were determined as exposure biomarkers. BMD was determined using single-photon absorptiometry. Urinary N-acetyl-β-d-glucosaminidase (UNAG) and urinary albumin (UALB) were determined as renal function biomarkers. Osteoporosis was defined if T-score < - 2.5. Multiple logistic regression showed that age, BCd, and menopausal status were independent risk factors for osteoporosis. The odds (OR) value was 1.19 (95% confidence interval (CI): 1.14-1.25) for age, 1.05 (95% CI: 1.004-1.10) for BCd, and 4.75 (95% CI: 1.65-13.69) for menopausal status after adjusting with cofounders. Age and UCd were the independent risk factors for bone fracture. Nomograms were developed based on the associated factors. Age was the main determinant for osteoporosis or fracture. Receiver operating curve showed acceptable performance in predicting osteoporosis (area under the curve (AUC) = 0.93, 95CI: 0.90-0.96) and fracture (AUC = 0.67, 95% CI: 0.58-0.75). Linear discriminant analysis (LDA) further showed that 88.9% of osteoporosis and 68.4% of fractures were correctly classified. Our study develops nomograms that may be used to predict cadmium-induced osteoporosis or fracture if BMD data is not available.

A benchmark dose analysis for urinary cadmium and type 2 diabetes mellitus

Cadmium (Cd) is a heavy metal referred to as one of the environmental endocrine disruptors. The dose-dependent association between Cd and type 2 diabetes mellitus (T2DM) has been elucidated, but the corresponding threshold has not been established. To evaluate the urinary Cd levels associated with T2DM, we perform a benchmark dose (BMD) analysis based on data from the 1999-2006 National Health and Nutrition Examination Survey (NHANES). Weighted datasets were generated by the inverse probability of treatment weighting analysis to develop the robustness of our analysis. We inferred a strong positive association between urinary Cd and T2DM in unweighted and weighted populations. BMD and its low limit (BMDL) estimates for 5% benchmark responses (BMR) was 0.297 (0.198) and 0.190 (0.178) μg/g creatinine for each population, respectively. The sensitivity analysis by race, followed by weight of sum method showed similar estimates of urinary Cd level for the risk of developing T2DM, which are rather low and far less than those for the renal or bone disease development risk. This indicates that T2DM can be a sensitive outcome of Cd exposure and therefore should be taken into account in the development of standard regulatory limits for safe exposure to Cd.

Cadmium and Lead Levels in Blood and Arsenic Levels in Urine among Schoolchildren Living in Contaminated Glassworks Areas, Sweden

The Kingdom of Crystal, an area in southern Sweden famous for its many glassworks, is historically heavily burdened by pollution from this industry. Glass crust containing cadmium (Cd), lead (Pb), and arsenic (As) has been deposited around the area and used as filling. The purpose of this study was to monitor whether the high levels of metals in the contaminated soil were reflected in blood and urine among school children in this area. Blood and urine samples were collected from 87 children in 2017. The levels of cadmium (Cd-B) and lead (Pb-B) found in blood were determined by inductively coupled plasma mass spectrometry (ICP-MS). The speciation of As in urine (As-U) was performed by ion chromatography. The geometric mean of Cd-B and Pb-B among the children were 0.09 μg/L and 9.9 μg/L respectively. The geometric mean of inorganic As (AsIII and AsV) with metabolites in urine was 6.1 μg/L and 6.94 μg/g creatinine. Children in the study area had blood levels of Pb and Cd that correspond to levels generally found in Swedish children. The levels of inorganic As and its metabolites in urine were low and in the same magnitude as other children in Europe and the U.S.

Zinc-biofortified wheat accumulates more cadmium in grains than standard wheat when grown on cadmium-contaminated soil regardless of soil and foliar zinc application

Zinc (Zn)-biofortified wheat may contribute to decreasing widespread human Zn deficiency. Such genotypes may also accumulate cadmium (Cd) in grains that would expect to be decreased by Zn application. However, the influence of soil and foliar Zn application on grain Cd accumulation in Zn-biofortified versus standard wheat is unknown. In our experiment, we grew standard (Faisalabad-2008) and Zn-biofortified (Zincol-2016) wheats in pots having uncontaminated (T₀) or Cd-spiked (8 mg kg^-1) soil. Plants in Cd-amended pots were treated with no Zn (T₁), 8 mg Zn kg^-1 to soil at sowing (T₂), 0.5% w/v ZnSO₄·7H₂O to foliage at booting and heading (T₃), or soil (as in T₂) + foliar (as in T₃) Zn application (T₄). Only in the uncontaminated control, grain yield of Faisalabad-2008 was greater than Zincol-2016. Any Zn application to Zincol-2016 grown in Cd-spiked pots increased grain yield compared with the uncontaminated control. In both cultivars, grain Zn concentration was influenced more by foliar than soil Zn application. However, Zincol-2016 had 6 to 14 mg more Zn kg^-1 in grains than Faisalabad-2008 in the comparable treatments. Cadmium exposure (T₁ vs. T₀) decreased grain yield of only Faisalabad-2008, and decreased grain Zn concentration only in Zincol-2016. Without any Zn application, grain Cd concentration in both cultivars exposed to Cd was above the permissible level (0.20 mg kg^-1). Zinc application decreased grain Cd concentration, although it remained above the permissible level in both cultivars except in Faisalabad-2008 when treated with soil + foliar Zn. Foliar Zn application decreased grain Cd concentration more than soil Zn application, and more in Zincol-2016 than Faisalabad-2008. In the comparable Cd-spiked treatments, Zincol-2016 had 73 to 134% higher grain Cd concentration than Faisalabad-2008. The Zn-biofortified genotypes accumulating toxic metals may pose serious health issues. Therefore, future breeding for biofortification should focus on the selective accumulation of Zn.

Study on the relationship between age and the concentrations of heavy metal elements in human bone

Background

Excessive amounts of heavy metals such as cadmium, chromium, cobalt, lead, thallium, and manganese are extremely harmful to the human body. These elements can accumulate in bone and impact bone metabolism. In this study, we investigated the relationship between age and the concentrations of these elements in human bone and blood.

Methods

Bone and blood samples were obtained from both older and younger patients. The concentrations of the elements under investigation were measured by inductively coupled plasma mass spectrometry (ICP-MS), and the specific concentrations in the bone and blood were then calculated.

Results

The results showed that with increasing age, the concentrations of chromium, cobalt, and thallium in bone decreased significantly, while the concentration of cadmium in bone markedly increased. However, there was no clear correlation between age and the concentrations of these heavy metals in blood. Notably, there was a close correlation between the concentration of cobalt in bone and the presence of osteopenia.

Conclusions

Senescence of the human body is accompanied by the shifting of cobalt, chromium, and thallium from the bone to the outer- bone. However, the concentration of cadmium in bone increases with age. These changes are very likely to be related to the equilibrium of bone metabolism in senescent individuals. In addition, only cobalt was shown to be significantly related to osteopenia.

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.

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.

Cadmium Exposure and Osteoporosis: A Population-Based Study and Benchmark Dose Estimation in Southern China

This study aimed to assess the association between osteoporosis and long-term environmental Cd exposure through diet in southern China. A total of 1116 subjects from a Cd-polluted area and a non-Cd-polluted area were investigated. All subjects met the criteria of having been living in the investigated area for more than 15 years and lived on a subsistence diet of rice and vegetables grown in that area. Besides bone mineral density, the levels of urinary markers of early renal impairment, such as urinary N-acetyl-β-D-glucosaminidase (NAG), α₁ -microglobulin, β₂ -microglobulin, and urinary albumin, were also determined. Urinary Cd concentrations of all studied subjects ranged from 0.21 to 87.31 µg/g creatinine, with a median of 3.97 µg/g creatinine. Multivariate linear regression models indicated a significant negative association of urinary Cd concentrations with bone mineral density. In logistic regression models, both categorical and continuous urinary Cd concentrations were positively associated with osteoporosis. Subjects in the second, third, and fourth quartiles of urinary Cd concentration had greater odds of osteoporosis compared with subjects in the first quartile (odds ratio [OR] = 3.07, 95% confidence interval [CI], 1.77 to 5.33; OR = 4.63, 95% CI, 2.68 to 7.98; OR = 9.15, 95% CI, 5.26 to 15.94, respectively). Additional adjustment for levels of urinary markers did not attenuate the associations. No evidence existed of an interaction between urinary Cd concentration and renal function using levels of urinary markers, and estimated glomerular filtration rate (eGFR). In all subjects, the benchmark dose and benchmark dose lower bound were 1.14 (0.61) and 2.73 (1.83) µg/g creatinine, with benchmark response set at 5% and 10%, respectively. The benchmark dose of urinary Cd was lower in women than in men. This study demonstrated an inverse association between the body burden of Cd and osteoporosis. The toxic effect of Cd on bone may occur in parallel to nephrotoxicity. © 2017 American Society for Bone and Mineral Research.

Relation of rice intake and biomarkers of cadmium for general population in Korea

Environmental exposure to cadmium can cause renal damage. Foods containing cadmium are generally regarded as the main environmental sources of human exposure to cadmium. In this study, foods that are ingested in large amounts, including rice and other types of food with a high concentration of cadmium, were investigated to determine the correlation between the foods' cadmium content and biomarkers. The datasets required for this study, including blood cadmium concentration, biomarker concentration, and data on the amount of consumption by food item, were obtained from KNHNES. Furthermore, data on food groups with high daily exposure to hazardous amounts of cadmium were obtained by monitoring raw food sources from 2010 to 2012. The investigation was then followed by correlation analysis, which was performed to assess the relationship between the amount of rice consumption and cadmium concentration. The Pearson coefficient analysis on the relationship between the amount of food consumption and the biomarker showed that the correlation between foods' cadmium content and blood cadmium and that of between foods' cadmium content and other biomarkers were confirmed as statistically significant in the case of the cadmium content of white rice, while, in the case of brown rice, it was confirmed by a few biomarkers.

Body burden of cadmium and its related factors: a large-scale survey in China

A survey of more than 6000 participants from four distinct non-polluted and polluted regions in China was conducted to evaluate the body burden of cadmium (Cd) on the Chinese populations using urinary Cd (UCd) as a biomarker. The findings revealed that the UCd level was 1.24 μg/g creatinine (μg/g cr) for the sample population from non-polluted Shanghai, and the UCd levels exceeded 5 μg/g cr, which is the health-based exposure limit set by the World Health Organization (WHO), in 1.1% of people. The mean UCd levels in moderately polluted (Hubei and Liaoning) and highly polluted areas (Guizhou) were 4.69 μg/g cr, 3.62 μg/g cr and 6.08 μg/g cr, respectively, and these levels were 2.9 to 4.9 times the levels observed in Shanghai. Notably, the UCd levels exceeded the recently updated human biomonitoring II values (i.e., intervention or "action level") in 44.8%-87.9% of people from these areas compared to only 5.1%-21.4% of people in Shanghai. The corresponding prevalence of elevated UCd levels (>WHO threshold, 5 μg/g cr) was also significantly higher (30.7% to 63.8% vs. 1.1%), which indicates that elevated Cd-induced health risks to residents in these areas. Age and region were significant determinants for UCd levels in a population, whereas gender did not significantly influence UCd.

Effects of Maternal Exposure to Cadmium Oxide Nanoparticles During Pregnancy on Maternal and Offspring Kidney Injury Markers Using a Murine Model

Nanoparticles (NP) are pervasive in many areas of modern life, with little known about their potential toxicities. One commercially important NP is cadmium oxide (CdO), which is used to synthesize other Cd-containing NP, such as quantum dots. Cadmium (Cd) is a well-known nephrotoxicant, but the nephrotoxic potential of CdO NP remains unknown, particularly when exposure occurs during pregnancy. Therefore, pregnant CD-1 mice were used to examine the effects of inhaled CdO NP (230 μg CdO NP/m(3)) on maternal and neonatal renal function by examining urinary creatinine and urinary biomarkers of kidney injury, including kidney injury molecule-1 (Kim-1) and neutrophil gelatinase-associated lipocalin (NGAL). Inhalation of CdO NP by dams produced a fivefold increase in urinary Kim-1 with no marked effect on urinary creatinine levels. Kim-1 mRNA expression peaked by gestational day (GD) 10.5, and NGAL expression increased from GD 10.5 to 17.5. In addition, histological analyses revealed proximal tubular pathology at GD 10.5. Neonatal Kim-1 mRNA expression rose between postnatal days (PND) 7 and 14, with mammary glands/milk being the apparent source of Cd for offspring. These studies demonstrate that, similar to what is seen with other Cd forms, Cd associated with inhaled CdO NP results in renal injury to both directly exposed dam and offspring. As commercial uses for nanotechnology continue to expand throughout the world, risks for unintentional exposure in the workplace increase. Given the large number of women in the industrial workforce, care needs to be taken to protect these already vulnerable populations.

Benchmark dose estimation of cadmium reference level for hypertension in a Chinese population

Cadmium exposure can cause high blood pressure or hypertension. Benchmark dose has been used to estimate the reference point of cadmium for kidney and bone damage. In this study, we observed the association of blood pressure and cadmium in blood (BCd) and evaluated the reference level of cadmium for hypertension using benchmark dose (BMD) approach. A total of 441 subjects were included in this study. Blood samples were collected from each individual for BCd determination. Blood pressure was measured by electronic sphygmomanometer. BMD and BMDL were calculated using BMD software corresponding to additional risk of 10%. The systolic blood pressure (SBP), diastolic blood pressure (DBP) and prevalence of hypertension increased with the increasing of BCd, especially for SBP (χ(2)=3.9, p=0.047 in men; χ(2)=4.3, p=0.037 in women). With a benchmark response of 10%, the BMDL10 for hypertension (high SBP) was 0.95μg/L and 1.02μg/L for women and men, respectively; the BMDL10 for hypertension (high DBP) was 1.8μg/L and 1.66μg/L for women and men, respectively. Our data evidenced that BCd was associated with elevation in blood pressure and hypertension, especially for women. The reference level of cadmium for hypertension with high SBP was lower than that of high DBP.

Histopathological analysis for osteomalacia and tubulopathy in itai-itai disease

BACKGROUND & AIMS

Cadmium (Cd) is a widespread environmental contaminant that causes both renal tubulopathy and osteomalacia. Osteomalacia is thought to be a result of renal tubulopathy, but there are few studies about the histopathological relationship between the two pathoses. Therefore, in the present study, we examined specimens from cases of itai-itai disease (IID), the most severe form of chronic cadmium poisoning, to evaluate the relationship between them.

METHODS

We analyzed kidney and bone specimens of 61 IID cases and the data regarding Cd concentration in kidney and bone. Tubulopathy was graded on the basis of a three-step scale (mild, moderate, and severe) using the following three items: the degree of proximal tubular defluxion, thickness of renal cortex, and weight of the kidney. Osteomalacia was evaluated using the relative osteoid volume (ROV).

RESULTS

There were 15 cases of mild, 19 cases of moderate, and 27 cases of severe tubulopathy. The average ROV was 24.9 ± 2.0%. ROV tended to increase as tubulopathy advanced in severity, and ROV was significantly higher in cases with severe tubulopathy than those with mild or moderate tubulopathy. ROV had a negative correlation with Cd concentration in the kidney but no correlation with that in the bone.

CONCLUSIONS

Our results suggest that the development of osteomalacia was related to the development of tubulopathy.

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

BACKGROUND

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

OBJECTIVES

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

DISCUSSION

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

CONCLUSION

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

The liver in itai-itai disease (chronic cadmium poisoning): pathological features and metallothionein expression

Cadmium (Cd) is a highly hepatotoxic heavy metal, which is widely dispersed in the environment. Acute Cd hepatotoxicity has been well studied in experimental animals; however, effects of prolonged exposure to Cd doses on the liver remain unclear. In the present study, to evaluate chronic Cd hepatotoxicity, we examined specimens from cases of itai-itai disease, the most severe form of chronic Cd poisoning. We compared 89 cases of itai-itai disease with 27 control cases to assess Cd concentration in organs. We also examined 80 cases of itai-itai disease and 70 control cases for histopathological evaluation. In addition, we performed immunohistochemistry for metallothionein, which binds and detoxifies Cd. Hepatic Cd concentration was higher than Cd concentration in all other organs measured in the itai-itai disease group, whereas it was second highest following renal concentration in the control group. In the liver in the itai-itai disease group, fibrosis was observed at a significantly higher rate than that in the control group. Metallothionein expression was significantly higher in the itai-itai disease group than that in the control group. Prolonged exposure to low doses of Cd leads to high hepatic accumulation, which can then cause fibrosis; however, it also causes high expression of metallothionein, which is thought to reduce Cd hepatotoxicity.

Protective effect of zinc supplementation against cadmium-induced oxidative stress and the RANK/RANKL/OPG system imbalance in the bone tissue of rats

It was investigated whether protective influence of zinc (Zn) against cadmium (Cd)-induced disorders in bone metabolism may be related to its antioxidative properties and impact on the receptor activator of nuclear factor (NF)-κΒ (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system. Numerous indices of oxidative/antioxidative status, and Cd and Zn were determined in the distal femur of the rats administered Zn (30 and 60mg/l) or/and Cd (5 and 50mg/l) for 6months. Soluble RANKL (sRANKL) and OPG were measured in the bone and serum. Zn supplementation importantly protected from Cd-induced oxidative stress preventing protein, DNA, and lipid oxidation in the bone. Moreover, Zn protected from the Cd-induced increase in sRANKL concentration and the sRANKL/OPG ratio, and decrease in OPG concentration in the bone and serum. Numerous correlations were noted between indices of the oxidative/antioxidative bone status, concentrations of sRANKL and OPG in the bone and serum, as well as the bone concentrations of Zn and Cd, and previously reported by us in these animals (Brzóska et al., 2007) indices of bone turnover and bone mineral density. The results allow us to conclude that the ability of Zn to prevent from oxidative stress and the RANK/RANKL/OPG system imbalance may be implicated in the mechanisms of its protective impact against Cd-induced bone damage. This paper is the first report from an in vivo study providing evidence that beneficial Zn impact on the skeleton under exposure to Cd is related to the improvement of the bone tissue oxidative/antioxidative status and mediating the RANK/RANKL/OPG system.

Cadmium intake and systemic exposure in postmenopausal women and age-matched men who smoke cigarettes

Mean blood cadmium (B-Cd) concentrations are two- to threefold higher in smokers than in nonsmokers. The basis for this phenomenon is not well understood. We conducted a detailed, multifaceted study of cadmium exposure in smokers. Groups were older smokers (62±4 years, n = 25, 20% male) and nonsmokers (62±3 years, n = 16, 31% male). Each subject's cigarettes were machine smoked, generating individually paired measures of inhaled cadmium (I-Cd) versus B-Cd; I-Cd and B-Cd were each evaluated three times, at monthly intervals. Urine cadmium (U-Cd) was analyzed for comparison. In four smokers, a duplicate-diet study was conducted, along with a kinetic study of plasma cadmium versus B-Cd. Female smokers had a mean B-Cd of 1.21ng Cd/ml, with a nearly 10-fold range (0.29-2.74ng Cd/ml); nonsmokers had a lower mean B-Cd, 0.35ng Cd/ml (p < 0.05), and narrower range (0.20-0.61ng Cd/ml). Means and ranges for males were similar. Estimates of cadmium amounts inhaled daily for our subjects smoking ≥ 20 cigarettes/day were far less than the 15 µg Cd reported to be ingested daily via diet. This I-Cd amount was too low to alone explain the 3.5-fold elevation of B-Cd in our smokers, even assuming greater cadmium absorption via lungs than gastrointestinal tract; cadmium accumulated in smokers' lungs may provide the added cadmium. Finally, B-Cd appeared to be linearly related to I-Cd values in 75% of smokers, whereas 25% had far higher B-Cd, implying a possible heterogeneity among smokers regarding circulating cadmium concentrations and potentially cadmium toxicity.

Variation in benchmark dose (BMD) and the 95% lower confidence limit of benchmark dose (BMDL) among general Japanese populations with no anthropogenic exposure to cadmium

BACKGROUND

The use of benchmark dose (BMD) and the 95% lower confidence limit of benchmark dose (BMDL) have been gaining popularity not only in experimental studies but also in epidemiological studies including those on toxicology of cadmium (Cd), a ubiquitous hazardous element in the environment. However, the reproducibility of BMD and BMDL values has seldom been examined.

OBJECTIVES

This study was initiated to determine whether consistent BMD and BMDL values are obtained for similar non-exposed populations, i.e., the populations with no anthropogenic exposure to Cd in a single nation of Japan.

METHODS

Cd (an exposure marker), α(1)-microglobulin (α(1)-MG), β(2)-microglobulin (β(2)-MG) and N-acetyl-β-D-glucosaminidase (NAG) (three effect markers of tubular dysfunction) levels in the urine of adult Japanese women from five previous publications of this study group were examined. Overall, data were available for 17,375 cases (in 16 prefectures) regarding Cd, α(1)-MG and β(2)-MG, and 6,409 cases (in ten prefectures) regarding NAG. The data were used to calculate BMD and BMDL values taking advantage of the hybrid approach (Budtz-Jǿrgensen et al. in Biometrics 57:698-706, 2001). It was possible to calculate BMD and BMDL values for α(1)-MG and β(2)-MG for all of the 16 prefectures with 17,375 cases, whereas the values for NAG were successfully calculated for nine prefectures with 5,843 cases.

RESULTS

The application gave BMD values of 1.92, 2.46 and 2.32 μg Cd/g cr for α(1)-MG, β(2)-MG and NAG, respectively, and BMDL values of 1.83, 2.32 and 2.09 μg Cd/g cr. Large inter-prefectural variations were observed in the BMD and BMDL; there was about fourfold difference both in BMD and in BMDL calculated for α(1)-MG and β(2)-MG in 16 prefectures, and the variation was greater (i.e., by about sevenfold) in BMD and BMDL for NAG in nine prefectures. A survey of relevant literature revealed variation in BMD and BMDL values of similar folds as observed in the present analyses in five studies of Japanese populations. Multiple regression analyses taking BMD or BMDL as a dependent variable and age, CR concentration and Cd concentration as independent variables showed both BMD and BMDL were significantly influenced by Cd concentration in cases of α(1)-MG and β(2)-MG, whereas BMD and BMDL for NAG was by CR.

CONCLUSIONS

Even when the analysis was conducted in a single nation, both BMD and BMDL for the Cd effect markers varied by ca. fourfold when examining α(1)-MG or β(2)-MG and the values varied by ca. sevenfold for NAG among Cd-non-exposed populations. The most influential factors in the study population may include urine density and Cd levels in the urine.

Assessment of dietary cadmium exposure in Sweden and population health concern including scenario analysis

The median dietary cadmium exposure for adults in Sweden is around 1 μg/kg/week and the upper 95th and 99th percentiles are 1.6-1.8 and 1.9-2.2 μg/kg/week, respectively. Potatoes and wheat flour were the most important food categories, contributing with 40-50% to the exposure. Differences in dietary patterns between high and low exposed individuals were observed; for high exposed individuals, seafood and spinach contributed with an exposure similar to that low exposed individuals received from potatoes and wheat flour. Consequences of differences in methodology used for exposure assessment are discussed. The median exposure is a factor 2 lower compared to that estimated by the European Food Safety Authority (EFSA). It is also a factor 1.4 lower compared to that of the assessment used for development of the EFSA tolerable weekly intake (TWI). The potential importance of this latter fact was addressed by adjusting the present assessment to that used for TWI derivation. While the percentage of the population exceeding the TWI was <1% for the present data, it was around 3% for adjusted data, which is more in line with observations at the level of urinary cadmium. Scenario analysis was also performed to addresses the consequence of increasing/decreasing cadmium occurrence levels.

Environmental exposure to POPs and heavy metals in urban children from Dhaka, Bangladesh

Persistent organic pollutants (POPs) and heavy metals are well known environmental pollutants. Even though numerous studies have been carried out to assess human exposures to these compounds, there is still a lack of data on humans from developing countries, especially in underprivileged children. The objective of this study was to assess the exposure to POPs and heavy metals in children from Dhaka, Bangladesh. One specific aim was to investigate whether children working at, or living close to, open waste disposal sites (WDSs) were more heavily exposed than other urban children. In 2008, blood and serum were collected from 73 children aged 7-16 from five neighbourhoods. Some of the children lived and worked at WDSs (N = 31), others lived next to a WDS (N = 17), whereas some children lived far from such sites (N = 25). Blood levels of lead (B-Pb), cadmium (B-Cd), and selenium (B-Se) were determined by ICP-MS for all subjects. The metal levels were high, with B-Pb overall mean 120 μg L(-1) (range 40-220), B-Cd 0.74 μg L(-1) (0.22-4.1), and B-Se 120 μg L(-1) (81-170). There were no marked differences between children from the different neighbourhoods, or between WDS workers and other children. PCB levels were low and with no contrast between neighbourhoods, for CB-153 the overall mean was 7.0 ng g(-1) fat (2.8-51). In contrast, high levels of DDTs were observed in all children, for 4,4'-DDE 1300 ng g(-1) fat (420-4600), and for 4,4'-DDT 326 ng g(-1) fat (44-1400), indicating ongoing exposure. PBDE levels were low, and BDE-209 was quantitated mainly in children working at or living close to WDSs. In conclusion, the high levels of DDTs, lead and cadmium observed in children from Dhaka are of concern. Many children were exposed at levels where health effects have been observed, or at levels without safety margins.

Protective effect of zinc against cadmium hepatotoxicity depends on this bioelement intake and level of cadmium exposure: a study in a rat model

It was estimated, in a rat model of moderate and relatively high chronic human exposure to cadmium (Cd), whether enhanced zinc (Zn) consumption may prevent Cd-induced liver injury and if the possible protective effect of this bioelement depends on its intake. For this purpose, the structure and function of the liver of the rats that received Zn (30 and 60mg/l) or/and Cd (5 and 50mg/l) for 6months were evaluated. The treatment with Cd led to, dependent on the exposure level, pathological changes in the liver, including enhanced apoptosis and induction of inflammatory and necrotic processes. Moreover, the serum activities of hepatic marker enzymes (alanine transaminase and aspartate transaminase) and the concentration of proinflammatory cytokine - tumor necrosis factor α were increased. The supplementation with 30 and 60mg Zn/l (enhancing daily Zn intake by 79% and 151%, respectively) partially or totally prevented from some of the Cd-induced changes in the liver structure and function; however, it provided no protection from necrosis, and the administration of 60mg Zn/l during the higher Cd exposure even intensified this process. At both levels of Cd treatment, the use of 30mg Zn/l was more effective in preventing liver injury than that of 60mg Zn/l. The hepatoprotective impact of Zn may be explained, at least partly, by its antioxidative, antiapoptotic and anti-inflammatory action, ability to stimulate regenerative processes in the liver tissue, and indirect action resulting in a decrease in the liver pool of the non-metallothionein-bound Cd(2+) ions able to exert toxic action. The results provide strong evidence that enhanced Zn consumption may be beneficial in protection from Cd hepatotoxicity; however, its excessive intake at relatively high exposure to Cd may intensify liver injury.

The involvement of oxidative stress in the mechanisms of damaging cadmium action in bone tissue: a study in a rat model of moderate and relatively high human exposure

It was investigated whether cadmium (Cd) may induce oxidative stress in the bone tissue in vivo and in this way contribute to skeleton damage. Total antioxidative status (TAS), antioxidative enzymes (glutathione peroxidase, superoxide dismutase, catalase), total oxidative status (TOS), hydrogen peroxide (H(2)O(2)), lipid peroxides (LPO), total thiol groups (TSH) and protein carbonyl groups (PC) as well as Cd in the bone tissue at the distal femoral epiphysis and femoral diaphysis of the male rats that received drinking water containing 0, 5, or 50mg Cd/l for 6 months were measured. Cd, depending on the level of exposure and bone location, decreased the bone antioxidative capacity and enhanced its oxidative status resulting in oxidative stress and oxidative protein and/or lipid modification. The treatment with 5 and 50mg Cd/l decreased TAS and activities of antioxidative enzymes as well as increased TOS and concentrations of H(2)O(2) and PC at the distal femur. Moreover, at the higher exposure, the concentration of LPO increased and that of TSH decreased. The Cd-induced changes in the oxidative/antioxidative balance of the femoral diaphysis, abundant in cortical bone, were less advanced than at the distal femur, where trabecular bone predominates. The results provide evidence that, even moderate, exposure to Cd induces oxidative stress and oxidative modifications in the bone tissue. Numerous correlations noted between the indices of oxidative/antioxidative bone status, and Cd accumulation in the bone tissue as well as indices of bone turnover and bone mineral status, recently reported by us (Toxicology 2007, 237, 89-103) in these rats, allow for the hypothesis that oxidative stress is involved in the mechanisms of damaging Cd action in the skeleton. The paper is the first report from an in vivo study indicating that Cd may affect bone tissue through disorders in its oxidative/antioxidative balance resulting in oxidative stress.