Urinary cadmium excretion is correlated with calcaneal bone mass in Japanese women living in an urban area

A protocol for the prospective study of urinary cadmium with risk of fracture, bone loss, and muscle loss

Cadmium (Cd) is a heavy metal and natural element found in soil and crops with increasing concentrations linked to phosphate fertilizers and sewage sludge applied to crop lands. A large fraction of older US men and woman have documented Cd exposure. Cd exposure has proven health concerns such as risk of lung cancer from inhalation and impaired renal function; however, growing evidence suggests it also influences bone and muscle health. Given that low levels of Cd could affect bone and muscle, we have designed prospective studies using the two largest and most detailed US studies of bone health in older men and women: the Osteoporotic Fractures in Men Study and the Study of Osteoporotic Fractures. We are investigating the association of urinary cadmium (U-Cd), as a surrogate for long-term Cd exposure, with bone and muscle health. Building off suggestive evidence from mechanistic and cross-sectional studies, this will be the first well-powered prospective study of incident fracture outcomes, bone loss, and muscle loss in relation to U-Cd, an established biomarker of long-term Cd exposure. The following is a proposed protocol for the intended study; if successful, the proposed studies could be influential in directing future US policy to decrease Cd exposure in the US population similar to recent policies adopted by the European Union to limit Cd in fertilizers.

Cadmium exposure induces histological damage and cytotoxicity in the cardiovascular system of mice

Epidemiological studies have reported an association between chronic cadmium (Cd) exposure and increased cardiovascular risk; however, their causal relationship remains unclear. The aim of this study is to explore the effects of Cd exposure on the cardiac and arterial systems in mice. According to the concentration of cadmium chloride in drinking water, male mice were randomly divided into control and low-dose and high-dose Cd exposure groups. The intervention duration was 12 weeks. In cardiac tissues, Cd exposure led to focal necrosis, myofibril disarray, perivascular and interstitial fibrosis, and disorganized sarcomere structures. Cd also induced the apoptosis of cardiomyocytes and increased the expression levels of matrix metalloproteinase (MMP)-2 and MMP-14 in cardiac tissues. In the arterial tissues, Cd exposure damaged the intimal and medial layers of the aorta. Cd further reduced the viability of aortic smooth muscle cells in vitro. This study provides evidence for the Cd-induced damage of the cardiovascular system, which may contribute to various cardiovascular diseases.

A systematic review of adverse health effects associated with oral cadmium exposure

Scientific data characterizing the adverse health effects associated with dietary cadmium (Cd) exposure were identified in order to make informed decisions about the most appropriate toxicological reference value (TRV) for use in assessing dietary Cd exposure. Several TRVs are available for Cd and regulatory organizations have used epidemiologic studies to derive these reference values; however, risk of bias (RoB) evaluations were not included in the assessments. We performed a systematic review by conducting a thorough literature search (through January 4, 2020). There were 1714 references identified by the search strings and 328 studies identified in regulatory assessments. After applying the specific inclusion and exclusion criteria, 208 studies (Human: 105, Animal: 103) were considered eligible for further review and data extraction. For the epidemiologic and animal studies, the critical effects identified for oral Cd exposure from the eligible studies were a decrease in bone mineral density (BMD) and renal tubular degeneration. A RoB analysis was completed for 49 studies (30 epidemiological and 19 animal) investigating these endpoints. The studies identified through the SR that were considered high quality and low RoB (2 human and 5 animal) can be used to characterize dose-response relationships and inform the derivation of a Cd TRV.

An investigation of heavy metals in edible bird's nest from Indonesia using inductively coupled plasma mass spectrometry

Background and Aim:

In 2020, Indonesia, which has the highest global production of edible bird’s nest (EBNs), exported up to 1312.5 tons of this product at a value of USD 540.4 million. Recently, food safety aspects related to EBNs, including contamination with heavy metals, have become a serious concern. However, data on the presence and concentration of heavy metals in EBNs in Indonesia are not yet available. This study aimed to determine and compare the presence and concentrations of arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), and tin (Sn) in EBNs originating from several primary Indonesian islands. The study also analyzed the effect of washing on the heavy metal content in EBNs.

Materials and Methods:

A study on 44 swiftlet farmhouses (SFHs) was conducted to determine the concentrations of heavy metals in EBNs. The number of samples from the SFHs was allocated proportionally to the main EBN-producing islands in Indonesia, that is, Kalimantan, Sumatera, Sulawesi, and Java (22, 13, 7, and 2, respectively). The concentrations of the above five elements in the samples before washing (raw–unclean EBNs) and after washing (raw–clean EBNs) were determined by inductively coupled plasma mass spectrometry. Washing was conducted according to the general procedures at an EBN processing plant.

Results:

The raw–unclean EBNs from the four islands contained As, Pb, Cd, and Sn at varying concentrations. However, Hg was not detected in the raw–unclean EBN samples from Sulawesi. The raw–unclean EBNs from Kalimantan had lower concentrations of Pb and Cd compared with the other islands. The concentrations of As, Pb, Cd, and Sn in the EBNs decreased significantly after washing with clean water.

Conclusion:

Heavy metals (As, Hg, Pb, Cd, and Sn) were detected at a low level in most of the raw–unclean EBNs originating from the main Indonesian island where they were produced. The concentrations of all the heavy metals reviewed in the raw–unclean EBNs samples decreased significantly after washing.

The preferential accumulation of cadmium ions among various tissues in mice

Cadmium (Cd) is hazardous to human health because of its toxicity and long half-life of clearance. Many studies have explored the relationship between chronic Cd exposure and different human diseases. However, most of the studies limited the study targets of Cd toxicity to two or three organ systems. The goal of this study was to establish a mouse model of Cd accumulation in most organ systems and to particularly investigate the potential toxic effects of Cd to the cardiovascular system. Mice were divided into three groups: the control group, Cd-100 group, and Cd-200 group. In the control group, Cd was detected in the kidney, lung, liver, heart and urine but was undetectable in the aorta, intestine, thigh bone, spinal bone and serum. Upon chronic exposure in the Cd-100 and Cd-200 groups, Cd accumulated in all tissues, with a dramatic increase in concentration. We confirmed that Cd could accumulate significantly in the heart and aorta upon chronic exposure. This finding might help to explain the potential toxic effects of Cd on these organs. In addition, the calcium concentration in the bones and kidney declined when the exposure to Cd increased. This finding aligned with the negative effects of Cd on bony mineralization and the potential direct toxic effects of Cd on bones. The impacts of Cd on the cardiovascular system were explored. Histologically, chronic Cd exposure led to myocytes hypertrophy and myocardial architecture disarray in the Cd-100 group compared to those in the control group. Our research confirms that Cd can accumulate in all of the organs studied upon chronic exposure, and suggests that the toxicity of Cd accumulation may play important roles in mediating the pathophysiologic effects in these target organs, especially the bone and heart.

Standardized experimental model for cement dust exposure; tissue heavy metal bioaccumulation and pulmonary pathological changes in rats

•

Exposure model is a reliable method of studying pulmonary toxicity of aerosolized xenobiotics.

•

Deposition of particles beyond the conducting zone and tissue bioaccumulation accompany exposure to cement dust (ECD).

•

Histoarchitectural alteration, body-organ weight discordance are indicators of acute ECD.

A controlled experimental model of exposure to aerosols particularly for cement dust was recently invented in a study from the laboratory that found high serum levels of heavy metals, decrease gastrointestinal motility, and altered hematological variables in cement dust exposed rats. However, reproducibility was not considered. This work aims at standardizing the model and investigating preliminary toxicological indicators. Thirty male rats used in this study were divided into 3 groups (n = 10). Group 1; control, while groups 2 and 3 were exposed to cement dust for 14 days and 28 days respectively. We assessed clinical signs of toxicity, tissue heavy metal concentration, histopathological, and body weight (BW) changes. We observed poor movement coordination, abnormal posture, cephalic fur loss. Evidence of ischemia and fibrotic pneumoconiosis were grossly observed in the lungs of the exposed groups. There was a significant increase in tissue level of heavy metals with pulmonary and gastric heavy metal content showing a trendy relationship during the period of the exposure as the value of Lead, Chromium, Cadmium, Iron, Calcium, and Nickel increased by nearly similar percentages in both tissues. Organs weights increased; the 14-day exposed (198 ± 31; 168 ± 22) and 28-day exposed (198 ± 22; 187 ± 26) groups had significantly reduced body weight at the first and second weeks of exposure compared to the control group (265 ± 26; 357 ± 40) respectively. Exposure to cement dust induced low bone density in the exposed rats (p < 0.05). Histopathological alterations include necrosis, inflammatory cellular infiltration, and alveolar hyperplasia suggestive of the proliferative response of pulmonary tissue to the dust. The operation of the standardized apparatus mimics a typical occupational exposure and the findings show that cement dust induces systemic toxicity via respiratory perturbation and body/organ weight discordance mediated by heavy metal bioaccumulation.

Relationship between osteoid formation and iron deposition induced by chronic cadmium exposure in ovariectomized rats

Itai-itai (Japanese, "It hurts! It hurts!") disease (IID), a form of osteomalacia, can be induced in ovariectomized rats by long-term administration of cadmium (Cd). This IID rat model shows severe anemia, severe nephropathy, and osteomalacia accompanied by iron (Fe) deposition at the mineralization front. We characterized the pathogenesis of Cd-induced bone lesions by investigating the relationship between Fe deposition and osteoid tissue formation in ovariectomized rats. The rats were injected with CdCl₂ (0.5 mg/kg) for 70 weeks, with or without co-injection of erythropoietin (EPO) for varying lengths of time to elucidate whether EPO prevents and/or cures anemia, and, with the restoration from anemia, lessens the osteoid tissue formation. Necropsies were performed at 25, 50, or 70 weeks. Fe deposition at the mineralization front of bone was found at 50 weeks and increased thereafter. Animals injected with EPO showed decreased Fe deposition, although there was no relation between EPO administration and osteoid formation in the femur. Because the increase in bone lesion severity was independent of the amount of Fe deposition, we suggest that Fe deposition is not involved in the etiology of Cd-induced femoral bone lesions.

Smoking-Induced Risk of Osteoporosis Is Partly Mediated by Cadmium From Tobacco Smoke: The MrOS Sweden Study

Cigarette smoking is a risk factor for osteoporosis and bone fracture. Moreover, smoking causes exposure to cadmium, which is a known risk factor for osteoporosis. It is hypothesized that part of smoking-induced osteoporosis may be mediated via cadmium from tobacco smoke. We investigated this hypothesis using mediation analysis in a Swedish cohort of elderly men. This study was performed in 886 elderly men from the Swedish cohort of the Osteoporotic Fractures in Men (MrOS) study. Urinary samples, bone mineral density (BMD), smoking data, and other background information were obtained at baseline in 2002-2004. Urinary cadmium was analyzed in baseline samples and adjusted for creatinine. The cohort was followed until August 2018 for fracture incidence, based on the X-ray register. Mediation analysis was conducted to evaluate the indirect effect (via cadmium) of smoking on both BMD and fractures. Time to first fracture was analyzed using the accelerated failure time (AFT) model and Aalen's additive hazard model. The mean level of urinary cadmium was 0.25 μg/g creatinine. There were significant inverse associations between smoking and total body, total hip, and trochanter BMD. The indirect effects via cadmium were estimated to be 43% of the total effects of smoking for whole-body BMD, and even more for total hip and trochanter BMD. Smoking was also associated with higher risk of all fractures and major osteoporosis fractures. The indirect effects via cadmium were largest in nonvertebral osteoporosis fractures and hip fractures, constituting at least one-half of the total effects, in both the AFT and Aalen's model. The findings in this study provide evidence that cadmium exposure from tobacco smoke plays an important role in smoking-induced osteoporosis © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Serum minerals (Ca, P, Co, Mn, Ni, Cd) and growth hormone (IGF-1 and IGF-2) levels in postmenopausal Saudi women with osteoporosis

Osteoporosis is reported to be common among Saudi women. Several minerals appear to be important determinants of insulin-like growth factor (IGF), the bioactivity of which regulates bone and mineral metabolism. Here we proposed that mineral status may alter the IGF system among individuals with osteoporosis. This study aims to evaluate the relationships between essential elements and IGF levels among postmenopausal Saudi women with osteoporosis. A total of 128 postmenopausal Saudi women aged ≥50 years old were recruited in this study. Diagnosis of osteoporosis was done by using dual-energy x-ray absorptiometry to determine the bone minerals density (BMD). Serum calcium and phosphate were determined using routine chemical analyzer. Serum Co, Mn, Ni, Cd were measured using inductively coupled plasma mass spectrometry. Serum IGF-1 and IGF-2 were determined using Luminex xMAP. Using stepwise linear regression analysis, only Cd was identified to be significantly associated with IGF1 in osteoporosis, explaining 3% (confidence interval 0.01-0.05; P = 0001) of the variance perceived. Our results suggest that Cd exposure indirectly affects BMD which may increase the risk of osteoporosis in postmenopausal women. Further longitudinal study using a larger sample size is recommended to determine causality of Cd levels and IGF-1.

Disruption of Bone Zinc Metabolism during Postnatal Development of Rats after Early Life Exposure to Cadmium

This current study was conducted to investigate whether bone tissue impairment induced by early life exposure to cadmium (Cd) during postnatal development could result from disruption to zinc (Zn) metabolism. For this reason, the offspring from mothers receiving either tap water, Cd, Zn or Cd + Zn during gestation and lactation periods were euthanized at PND21 and PND70. At the end of the lactation period (PND21), our results showed that exposure to Cd increased Cd accumulation and Zn depletion in the femur. Furthermore, calcium (Ca) level was reduced. At the molecular level, Cd induced an increase of MT-1 expression and caused an upregulation of ZIP2 accompanied with a down-regulation of ZnT5. Runx2, ALP, colα-1 and Oc mRNA levels were also decreased. In plasma, IGF-1 and osteocalcin concentrations were decreased. Further, Cd altered femoral growth by generating changes in the growth plate. Consequently, the toxic effect of Cd persisted at adult age (PND70) by decreasing bone volume (%BV/TV), bone mineral density (BMD) and Ca content and by increasing trabecular separation (Tb.Sp) in the distal femur. Interestingly, Zn supply provided total or partial corrections of several toxic effects of Cd. These data suggest that the increases of Zn bioavailability as well as the reduction of Cd accumulation in the femur following the changes in ZIP2 and ZnT5 expression are part of the mechanism involved in Zn protection against Cd toxicity on bone tissue.

The heavy metals lead and cadmium are cytotoxic to human bone osteoblasts via induction of redox stress

The heavy metals (HMs) lead and cadmium are persistent environmental pollutants capable of inducing ill-health in exposed individuals. One of the primary sites of accumulation and potential damage from HMs is bone, and we therefore examined the acute effects of lead and cadmium on human bone osteoblasts in vitro over a concentration range of 0.1 μM to 1mM, and for 3, 6, 12, 24, and 48 hour exposures. Incubation of osteoblasts with either lead or cadmium reduced cell viability in a concentrations and exposure durations dependent manner, as measured using MTT and LDH assays. Cytotoxicity was significant from 0.1 μM concentrations after 48 hour exposures. Both HMs damaged cellular bioenergetics with reductions of ATP production, mitochondrial complex activities, and aerobic respiration. There was a concomitant elevation of reactive oxygen species, with induction of redox stress measured as increased lipid peroxidation, and depleted cellular redox defense systems via reduced superoxide dismutase and catalase activity and cellular glutathione levels. Both HMs induced nuclear activation of Nrf2, presumably to increase transcription of antioxidant responsive genes to combat oxidative stress. Incubation of osteoblasts with HMs also compromised the secretion of procollagen type 1, osteocalcin, and alkaline phosphatase. Pre-incubation of osteoblasts with reduced glutathione prior to challenge with HMs lessened the cytotoxicity of the HMs, indicative that antioxidants may be a beneficial treatment adjunct in cases of acute lead or cadmium poisoning.

Evaluation of the association between urinary cadmium levels below threshold limits and the risk of diabetes mellitus: a dose-response meta-analysis

As cadmium levels are increasing in the environment, the adverse effects of cadmium exposure specifically associated with chronic diseases are receiving increasing attention. Several population-based studies have been conducted on the association between cadmium and diabetes mellitus (DM) but have reported controversial results. Here, we aimed to evaluate the association between cadmium exposure and DM. In this meta-analysis, a random effects model was used because there was evidence of heterogeneity among studies. A dose-response relationship was assessed through a restricted cubic spline model with three knots. The results showed a positive association between cadmium levels in the body and DM (OR = 1.27; 95% CI, 1.07-1.52). The cadmium levels in the body were defined on the basis of combined urinary and blood cadmium. Subgroup analysis further indicated a positive association between urinary cadmium levels and DM (OR = 1.31; 95% CI, 1.02-1.69). The dose-response analysis results showed a positive association between levels of urinary cadmium above 2.43 μg/g creatinine and DM, and the risk of DM increased by 16% for each l μg/g creatinine increase in urinary cadmium levels. The results from our meta-analysis indicate that cadmium levels in the body are positively associated with DM, and urinary cadmium levels above 2.43 μg/g creatinine are associated with an increased risk of DM.

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.

The effect of elemental content on the risk of dental fluorosis and the exposure of the environment and population to fluoride produced by coal-burning

Endemic fluorosis is a geochemical disease that affects thousands of people. Growing evidence from domestic and foreign studies indicate that fluorosis is associated with an abnormal level of the elements (such as F, Ca, Fe, Mg, Cu, Zn, P) in the environment and a population exposed to fluoride. To study the effect of the elemental content on the risk of dental fluorosis, the content of 25 elements in the environment produced by coal-burning and a population exposed to fluoride was determined. The results show that an abnormal level of various elements (including F, Al, Se, Zn, Cu, Fe, Mo, Mn, B, V, Ca, Mg, and P) in the population exposed to fluoride, which is related to the increasing or decreasing of the corresponding elements in the environment. Subsequent univariate and multivariate regression analyses show that high levels of F, Al, As, Pb and Cr were a risk factor for dental fluorosis, but not Se, Zn, Cu, B, Ca and P which were a protective factor for dental fluorosis. This study can provide a scientific basis for a further understanding of the causes of health damage caused by fluoride and the improvement of targeted prevention strategies.

Dietary Intake of Cadmium, Lead and Mercury and Its Association with Bone Health in Healthy Premenopausal Women

The bone is one of the relevant target organs of heavy metals, and heavy metal toxicity is associated with several degenerative processes, such osteoporosis and bone mineral alterations, that could lead to fractures. We aimed to study a presumed relationship between bone density, evaluated by quantitative bone ultrasound (QUS), dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) and the dietary intake of cadmium, lead and mercury in healthy premenopausal women. A total of 158 healthy, non-smoking, premenopausal women were incorporated into the study. A validated food frequency questionnaire (FFQ) was administered to assess intake during the preceding seven days. The median predicted dietary cadmium intake among the 158 women studied was 25.29 μg/day (18.62–35.00) and 2.74 μg/kg body weight/week (b.w./w) (1.92–3.83). Dietary lead intake was 43.85 μg/day (35.09–51.45) and 4.82 μg/kg b.w./w (3.67–6.13). The observed dietary mercury intake was 9.55 μg/day (7.18–13.57) and 1.02 μg/kg b.w./w (0.71–1.48). Comparisons, in terms of heavy metal intake, showed no significant results after further adjusting for energy intake. No statistically significant correlations between heavy metal intake and the QUS, DXA and pQCT parameters were observed. Levels of dietary exposure of cadmium, lead and mercury were mostly within the recommendations. We did not find associations between the QUS, DXA and pQCT parameters and the dietary intake of the studied heavy metals in healthy premenopausal women.

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.

Screening for Cd-Safe Cultivars of Chinese Cabbage and a Preliminary Study on the Mechanisms of Cd Accumulation

With the rapid progress of industrialization, the effects of environmental contamination on plant toxicity, and subsequently on human health, is a growing concern. For example, the heavy metal pollution of soil such as that caused by cadmium (Cd) is a serious threat. Therefore, screening for pollution-safe edible plants is an essential approach for growing plants under heavy metal-contaminated soils. In the current study, 35 Chinese cabbage (Brassica pekinensis L.) cultivars were selected with the aim of screening for Cd-safe cultivars (CSCs), analyzing their safety, and exploring the mechanism of Cd accumulation. Our field-culture experiments revealed that the Cd content in the edible parts of the cultivars were varied and were determined to possibly be CSCs. Hydroponics experiments were used to simulate six different degrees of soil contamination (high and low Cd concentrations) on possible CSCs. The results indicated a significant difference (p < 0.05) in Cd concentration in the cultivars, and verified the safety of these possible CSCs. The analyses of the transport coefficient and expression levels showed that the differences in Cd accumulation among the Chinese cabbage cultivars were related to the expression of genes involved in absorption and transport rather than a root-to-shoot translocation limitation.

Effects of environmental cadmium and lead exposure on adults neighboring a discharge: Evidences of adverse health effects

The purpose of the study was to determine Pb and Cd concentrations in humans and to assess the effect of co-exposure to these metals on biomarkers of oxidative stress and nephrotoxicity. Blood and urine levels of Pb and Cd, oxidative stress and urinary renal biomarkers were measured in 77 subjects neighboring a discharge and 52 in the control site. Exposed subjects showed significantly higher levels of lead and cadmium in blood and urine than the controls. Excessive production of reactive oxygen species induced by these metals in exposed subjects conducted to a decrease in antioxidant defense system (GPx, Selenium, GSH) and an increase in lipid peroxidation (MDA). Moreover, changes in markers of nephrotoxicity (high urinary concentrations of total protein, RBP and CC16, as well as GSTα and LDH increased activities) suggested the occurrence of discrete and early signs of impaired renal function for the discharge neighboring population.

Association between blood cadmium level and bone mineral density reduction modified by renal function in young and middle-aged men

The association between cadmium exposure and bone mineral density (BMD) has not been well studied in young and middle-aged men. This study examined the relationship between the level of blood Cd (BCd) and BMD in a young to middle-aged representative male population while considering renal function. Using data from the 4th Korea National Health and Nutrition Examination Survey, 2008-2009, 1275 adult men aged 20-64 years were analyzed. BCd was measured by atomic absorption spectrophotometry and renal function was assessed by the estimated glomerular filtration rate (eGFR) with CKD-EPI formula. The risk of lower bone density was increased according to the increase in BCd levels after adjusting for eGFR and covariates, in which a significant interaction between BCd and eGFR existed. Significant negative associations between BCd and BMD were found: beta (p-value) were -0.03 (0.02), -0.04 (0.004) and -0.03 (0.04) in total femur, lumbar spine and femoral neck, respectively, which were limited to the people with eGFR≤lower 25%. Although, a causal relationship could not be determined because of a cross-sectional design in the present study, the results suggest low level Cd toxicity to bone via low eGFR and that measures to reduce environmental Cd exposure may be helpful to prevent bone loss in men.

Blood Cadmium Is Associated with Osteoporosis in Obese Males but Not in Non-Obese Males: The Korea National Health and Nutrition Examination Survey 2008-2011

Osteoporosis in males is becoming an important health concern in an aging society. The aim of this study was to investigate the associations between cadmium exposure and osteoporosis by considering the effect of obesity in aged males using a representative sample of the Korean population. Using the fourth and fifth Korea National Health and Nutrition Examination Survey data, 1089 males over 50 years of age were analyzed. The blood cadmium concentration was measured. The bone mineral density in the total hip, femur neck, and lumbar spine was measured using dual-energy X-ray absorptiometry. T-scores to determine the presence of osteoporosis were calculated using a Korean reference. Subjects were stratified into two groups according to obesity status (body mass index <25 kg/m² and ≥25 kg/m²). In comparison with obese subjects with blood cadmium <1.00 μg/L, those with blood cadmium >1.50 μg/L had odds ratios of 4.57 (95% confidence interval [CI] 1.49–14.01) and 5.71 (95% CI 1.99–16.38) at the femur neck and any site, respectively, after adjusting for potential confounders such as age, serum creatinine, vitamin D deficiency, smoking, alcohol drinking, and physical activity level. However, this association was not significant in non-obese males. In conclusion, the effect of cadmium on osteoporosis was different by obesity status in aged males.

Dietary phosphorus exacerbates bone loss induced by cadmium in ovariectomized rats

OBJECTIVE

Postmenopausal bone loss can be exacerbated by environmental contaminants, including the heavy metal cadmium (Cd). We hypothesized that incorporating phosphorus (P) into the diet would lead to the chelation of Cd into P, preventing its absorption and subsequent bone loss.

METHODS

To test this hypothesis, we used ovariectomized rats as a model of postmenopausal osteoporosis to examine the deleterious effects of Cd on bone with and without added P. Fifty 3-month-old ovariectomized Sprague-Dawley rats were assigned to five treatment groups (n = 10 per group) for 3 months as follows: (1) control; (2) 50 ppm Cd; (3) 50 ppm Cd plus 1.2% P; (4) 200 ppm Cd; and (5) 200 ppm Cd plus 1.2% P.

RESULTS

Cd plus P caused a significant loss of whole body (P = 0.0001 and P < 0.001) and femoral (P = 0.0005 and P < 0.001) bone mineral density (BMD) and bone mineral content, respectively, and a loss of fourth lumbar vertebra BMD and bone mineral content (P < 0.0001 and P < 0.001, respectively). Nonetheless, 200 ppm Cd plus 1.2% P had the most deleterious effects on whole body and femoral BMD. For femoral neck microstructural properties, 50 ppm Cd plus 1.2% P caused an increase in trabecular separation, whereas 200 ppm Cd plus 1.2% P caused a decrease in bone volume-to-total volume ratio, a decrease in trabecular number, and an increase in trabecular separation and structural model index.

CONCLUSIONS

Our findings indicate that Cd exposure, along with high intake of P, may be a public health hazard with respect to bone health.

Differences in the susceptibility to cadmium-induced renal tubular damage and osteoporosis according to sex

This study aimed to estimate the risks for renal tubular damage and osteoporosis in individuals with long-term environmental Cd exposure. This cross-sectional study comprised 1086 residents living in the vicinity of a copper refinery plant. As the urinary Cd levels increased, the proportion of female subjects with β₂-MG ≥300 μg/g creatinine also increased significantly, but this was not observed in the male subjects. The prevalence of osteoporosis was significantly higher in men with urinary Cd >5 μg/g creatinine than in those with urinary Cd ≤5 μg/g creatinine. This difference was not observed in the corresponding female groups. The association between increased urinary excretion of β₂-MG and decreased BMD was statistically significant only in the female subjects. We suggest that an increased Cd body burden directly decreases the BMD in male subjects; however, in female subjects, it first induces renal microtubular damage, which can lead to osteoporosis.

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 relationship between chemical elements in soil and whole blood, and fluorosis induced by coal-fired pollution

To study the relationship between chemical elements in soil and whole blood, and fluorosis induced by coal-fired pollution, ecological and case-control studies were carried out. We determined the concentrations of 11 chemical elements and pH values in soil in two fluorosis-affected counties in Chongqing, China, and analyzed the correlation between these values and prevalence of dental fluorosis. Ni, I, F, Hg, and pH values positively correlated with fluorosis prevalence (P < 0.05); these soil parameters may be related to coal-fired pollution fluorosis. Cu, Zn, Ca, Mg, and Fe concentrations in whole blood, and fluoride levels in urine of residents in epidemic and non-epidemic areas were determined. Cu, Zn, Mg, and Fe levels of the children in the case group were lower than those of the children in the external control group; urine fluoride level in the children in the case group was higher than that of the children in the internal and external control groups (P < 0.05). The levels of Mg, Fe, and urine fluoride were higher in the case adult group than in the internal adult control group (P < 0.05). Anti-fluoride elements were deficient in endemic areas.

Effectiveness of maifanite in reducing the detrimental effects of cadmium on growth performance, cadmium residue, hematological parameters, serum biochemistry, and the activities of antioxidant enzymes in pigs

This study was conducted to investigate the toxicity of cadmium and to evaluate the effectiveness of maifanite in preventing cadmium-induced adverse effects. Thirty-two crossbred pigs (Duroc × Landrace × Large white, sex balanced, 17.25 ± 0.07 kg average body weight) were randomly allotted to one of four dietary treatments in a 2 × 2 factorial arrangement, with eight replicates per treatment and one pig per replicate. The dietary treatments included two cadmium (as CdCl2) doses (0.32 and 30.49 mg/kg) and two maifanite doses (0 and 1%). The results showed that pigs treated with cadmium decreased their average daily feed intake (P < 0.05) and increased (P < 0.05) the feed/gain ratio. Cadmium was found in the tissues of pigs that were fed with cadmium-contaminated diets, but the level of cadmium was much lower when maifanite was added to the cadmium-contaminated diets. Ingestion of diets that were artificially contaminated with cadmium (30.49 mg/kg of cadmium) reduced (P < 0.05) the number of lymphocytes, the total erythrocyte count, the hemoglobin level, and the hematocrit. However, the activities of serum aspartate aminotransferase and gamma glutamyltransferase were increased (P < 0.05). The total protein level was lower (P < 0.05) in pigs fed with cadmium-contaminated diets. The contents of malondialdehyde increased (P < 0.05), while the total antioxidant capacity and the activities of total superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and catalase decreased (P < 0.05) in pigs fed with cadmium-contaminated diets. Dietary addition of maifanite can, to some extent, prevent the negative effects associated with feeding cadmium diets (30.49 mg/kg of cadmium) to pigs.

Cadmium impact and osteoporosis: mechanism of action

CONTEXT

Cadmium (Cd) is a widespread environmental pollutant that is associated with increased risk of osteoporosis. It has been proposed that Cd's toxic effect on bone is exerted via impaired activation of vitamin D, secondary to the kidney effects.

OBJECTIVE

The present study was designed to investigate the damaging impact of Cd in drinking water on bone from biochemical and histopathological point of view.

MATERIALS AND METHODS

This study was conducted on 30, 3-months-old female Sprague Dawley rats exposed to cadmium chloride in a dose of 50 mg Cd/L in drinking water for 3 months. Serum was taken for determination of calcium, phosphorous levels, parathyroid hormone, 1,25 dihydroxy vitamin D(3), osteocalcin (OC) and bone specific alkaline phosphatase (BALP) activity.

RESULTS

The result revealed that Cd administration induces significant increase in serum calcium (Ca), phosphorous (P) and parathyroid hormone (PTH) levels in concomitant with significant reduction in serum vitamin D(3), osteocalcin (OC) levels and bone specific alkaline phosphatase (BALP) activity.

CONCLUSION

The present study provided clear evidence that long-term exposure to cadmium chloride produced marked abnormalities in bone biomarkers and increasing risk of fracture.

Bone mineral density and blood metals in premenopausal women

Exposure to metals, specifically cadmium, lead, and mercury, is widespread and is associated with reduced bone mineral density (BMD) in older populations, but the associations among premenopausal women are unclear. Therefore, we evaluated the relationship between these metals in blood and BMD (whole body, total hip, lumbar spine, and non-dominant wrist) quantified by dual energy X-ray absorptiometry in 248 premenopausal women, aged 18-44. Participants were of normal body mass index (mean BMI 24.1), young (mean age 27.4), 60% were white, 20% non-Hispanic black, 15% Asian, and 6% other race group, and were from the Buffalo, New York region. The median (interquartile range) level of cadmium was 0.30 μg/l (0.19-0.43), of lead was 0.86 μg/dl (0.68-1.20), and of mercury was 1.10 μg/l (0.58-2.00). BMD was treated both as a continuous variable in linear regression and dichotomized at the 10th percentile for logistic regression analyses. Mercury was associated with reduced odds of decreased lumbar spine BMD (0.66, 95% confidence interval: 0.44, 0.99), but overall, metals at environmentally relevant levels of exposure were not associated with reduced BMD in this population of healthy, reproductive-aged women. Further research is needed to determine if the blood levels of cadmium, lead, and mercury in this population are sufficiently low that there is no substantive impact on bone, or if effects on bone can be expected only at older ages.

Bone resorption and environmental exposure to cadmium in children: a cross--sectional study

BACKGROUND

Exposure to cadmium has been associated with osteoporosis and fracture risk in women and elderly, but studies in children are lacking. In the present study we investigate the association between markers of bone demineralization [urinary calcium (Ca) and deoxypyridinoline (DPD) excretion] and urinary cadmium (Cd) excretion (as an index of lifetime body burden).

METHODS

155 schoolchildren from 2 elementary schools in Lahore, Pakistan were included. Urinary Cd was measured as an index of lifetime exposure. We assessed the multivariate-adjusted association of exposure with markers of bone resorption, urinary DPD as well as with Ca excretion.

RESULTS

Urinary Cd averaged 0.50 nmol/mmol creatinine and was not influenced by age, height, weight and socio-economic status (SES). Independent of gender, age, height, weight and SES a doubling of urinary Cd was associated with a 1.72 times (p < 0.0001) increase in urinary DPD and, a 1.21 times (p = 0.02) increase in urinary Ca. Additional adjustment for urinary Ca revealed still significant associations between urinary Cd and urinary DPD. The shape of the association was linear without evidence of a threshold.

CONCLUSIONS

Even in young children, low-level environmental exposure to cadmium is associated with evidence of bone resorption, suggesting a direct osteotoxic effect with increased calciuria. These findings might have clinical relevance at older age.

Relationship between environmental exposure to cadmium and bone metabolism in a non-polluted area of Japan

OBJECTIVES

The purpose of this study was to investigate the effects of environmental low-grade cadmium exposure on bone in the population of a non-polluted area. We investigated the relationship between environmental cadmium exposure (via rice intake) and bone metabolism in middle-aged and elderly women living in a non-polluted area in Japan.

METHODS

Four hundred and twenty-nine women over the age of 39 years (54.6 ± 9.1 years; arithmetic mean ± SD) participated in this study in 2003. We investigated blood and urine, and rice intake, and performed ultrasonic bone evaluation, and obtained individual information about the subjects' health. Multiple regression analysis was performed in the statistical analysis.

RESULTS

The arithmetic mean of cadmium content in rice was 70.8 ± 44.7 μg/kg (AM ± SD). The geometric mean of daily cadmium intake (Cd intake) from rice calculated based on food consumption data was 9.12 μg/day (GSD 2.33). The geometric means of serum and urine cadmium concentrations were 1.57 μg/l (GSD 2.11) and 1.93 μg/g creatinine (cr.) (GSD 2.05), respectively. Multiple regression analysis showed positive correlations between (1) urinary free deoxypyridinoline (FDPD-U) and Cd intake (p < 0.05), (2) urinary cross-linked N-telopeptides of type I collagen (NTx-U) and Cd intake (p < 0.05), and (3) FDPD-U or NTx-U and cadmium concentration in urine (p < 0.01). No significant correlation between the parameters of ultrasonic bone evaluation and cadmium associated biomarkers was observed.

CONCLUSIONS

The results of the present study suggest the possibility of bone metabolic disorder induced by environmental low-grade cadmium exposure. With respect to osteoporosis, a long-term follow-up survey is required to assess the tolerable intake of cadmium in environmental exposure.

The relationship between the bone mineral density and urinary cadmium concentration of residents in an industrial complex

BACKGROUND

An association between cadmium exposure and bone mineral density (BMD) has been demonstrated in elderly women, but has not been well studied in youths and men. Some studies report either no or a weak association between cadmium exposure and bone damage.

OBJECTIVES

This study was designed to investigate the relationship between the urinary cadmium (U-Cd) levels and BMD of females and males of all ages.

METHODS

A total of 804 residents near an industrial complex were surveyed in 2007. U-Cd and BMD on the heel (non-dominant calcaneus) were analyzed with AAS-GTA and Dual-Energy X-ray absorptiometry, respectively. Demographic characteristics were collected by structured questionnaires. Osteoporosis and osteopenia were defined by BMD cut-off values and T-scores set by the WHO; T score>-1, normal; -2.5<T score <-1, osteopenia; and T score <-2.5, osteoporosis. Logistic and multiple linear regressions were applied to estimate the association between U-Cd levels and BMD.

RESULTS

The U-Cd levels in females (0.64 μg/g creatinine) were higher than those in males (0.48 μg/g creatinine) (p<0.001). With the logistic regression model, osteopenia was associated with high U-Cd levels (≥ 1.0 μg/g creatinine) in females (OR=2.92; 95% CI, 1.51-5.64) and in males (OR=3.37; 95% CI, 1.09-10.38). With the multiple linear regression model, the BMD of the adult group was negatively associated with U-Cd (<0.05), gender (female, p<0.001) and age (p<0.001). The BMD of participants who were ≤ 19 years of age was negatively associated with gender (female, p<0.01), whereas it was positively associated with age and BMI (p<0.001). BMD was not associated with exercise, smoking habits, alcohol consumption, job or parental education.

CONCLUSION

Results suggested that U-Cd might be associated with osteopenia as well as osteoporosis in both male and female adults. Age and female gender were negatively associated with BMD in the adult group, whereas age was positively associated with BMD in the youth group. Cadmium exposure may be a potential risk factor for lower-BMD and osteopenia symptoms as well as for osteoporosis symptoms.

Cadmium and transport of ions and substances across cell membranes and epithelia

Toxic metals such as cadmium (Cd(2+)) pose serious risks to human health. However, even though the importance of Cd(2+) as environmental health hazards is now widely appreciated, the specific mechanisms by which it produces its adverse effects have yet to be fully elucidated. Cd(2+) is known to enter cells, it binds and interacts with a multitude of molecules, it may indirectly induce oxidative stress and interfere with gene expression and repair of DNA. It also interacts with transport across cell membranes and epithelia and may therefore disturb the cell's homeostasis and function. Interaction with epithelial transport, especially in the kidney and the liver, may have serious consequences in general health. A lot of research still needs to be done to understand the exact way in which Cd(2+) interferes with these transport phenomena. It is not always clear whether Cd(2+) has primary or secondary effects on cell membrane transport. In the present review we try to summarize the work that has been done up to now and to critically discuss the relevance of the experimental work in vitro with respect to the in vivo situation.

Cadmium exposure in the population: from health risks to strategies of prevention

We focus on the recent evidence that elucidates our understanding about the effects of cadmium (Cd) on human health and their prevention. Recently, there has been substantial progress in the exploration of the shape of the Cd concentration-response function on osteoporosis and mortality. Environmental exposure to Cd increases total mortality in a continuous fashion without evidence of a threshold, independently of kidney function and other classical factors associated with mortality including age, gender, smoking and social economic status. Pooled hazard rates of two recent environmental population based cohort studies revealed that for each doubling of urinary Cd concentration, the relative risk for mortality increases with 17% (95% CI 4.2-33.1%; P < 0.0001). Tubular kidney damage starts at urinary Cd concentrations ranging between 0.5 and 2 μg urinary Cd/g creatinine, and recent studies focusing on bone effects show increased risk of osteoporosis even at urinary Cd below 1 μg Cd/g creatinine. The non-smoking adult population has urinary Cd concentrations close to or higher than 0.5 μg Cd/g creatinine. To diminish the transfer of Cd from soil to plants for human consumption, the bioavailability of soil Cd for the plants should be reduced (external bioavailability) by maintaining agricultural and garden soils pH close to neutral (pH-H(2)O of 7.5; pH-KCL of 6.5). Reducing the systemic bioavailability of intestinal Cd can be best achieved by preserving a balanced iron status. The latter might especially be relevant in groups with a lower intake of iron, such as vegetarians, and women in reproductive phase of life. In exposed populations, house dust loaded with Cd is an additional relevant exposure route. In view of the insidious etiology of health effects associated with low dose exposure to Cd and the current European Cd intake which is close to the tolerable weekly intake, one should not underestimate the importance of the recent epidemiological evidence on Cd toxicity as to its medical and public health implications.

Occupational cadmium exposure and calcium excretion, bone density, and osteoporosis in men

Exposure to cadmium has been associated with osteoporosis and fracture risk in women and the elderly, but studies in middle-aged men are lacking. In 83 male (ex)workers (mean age 45 years; range 24 to 64 years) in a radiator factory using cadmium-containing solder, we investigated the association between urinary cadmium excretion (as an index of lifetime body burden); bone mineral density (BMD) in the distal forearm, hip, and lumbar spine (by dual-energy X-ray absorptiometry); and urinary calcium excretion. Geometric mean urinary cadmium concentration was 1.02 microg/g of creatinine (5th to 95th percentile 0.17 to 5.51 microg/g). BMD was negatively correlated with urinary exposure to cadmium. The partial correlation coefficients (r) adjusted for age, body-mass index, and current smoking were -0.30 (p = .008) for BMD in the forearm, -0.27 (p = .017) in the hip, and -0.17 (p = .15) in the spine. Urinary calcium correlated positively (r = 0.23, p = .044) with the urinary cadmium excretion. Adjusted for the same covariates, the risk of osteoporosis (defined as a T-score below -2.5 in at least one measured bone site) increased dose dependently. Compared with the lowest tertile of urinary cadmium, the risks were 4.8- and 9.9-fold higher in the middle and highest tertiles, respectively. Only four (5%) men had evidence of renal tubular dysfunction (beta(2)-microglobulin > 300 microg/g of creatinine). Even in the absence of renal tubular dysfunction, occupational exposure to cadmium is associated in men with lower BMD values, a higher risk of having osteoporosis, and a higher urinary calcium excretion, suggesting a direct osteotoxic effect of cadmium.

Benchmark dose for cadmium-induced osteoporosis in women

We applied a hybrid approach to estimate the benchmark dose (BMD) and the lower 95% confidence limit (BMDL) for cadmium-induced bone effects in a population with low environmental exposure. Morning urine samples were collected by 794 Swedish women, aged 53-64 years, participating in a population-based study. We measured urinary cadmium (U-Cd), a marker of long-term exposure, and bone mineral density, expressed as its T-score (reference: 20-year old women) of the non-dominant wrist. BMD and BMDL, adjusted for relevant covariates, corresponding to an additional risk (BMR) of 5% or 10% were calculated, with the background risk at zero exposure set at 1% or 5%. With a BMR of 5% and a background risk of having low bone mineral density (at U-Cd = 0) of 1% or 5% (corresponding to T-score cut-offs -2.75 and -2.09, respectively), the BMD of U-Cd ranged 1.8-3.7 microg/g creatinine, and the BMDL ranged 1.0-2.1 microg/g creatinine. For a 5% BMR of osteoporosis (T-score < -2.5), the BMD was 2.9 microg/g creatinine and the BMDL 1.6 microg/g creatinine. The lowest obtained BMD of U-Cd for wrist bone mineral density was only slightly higher than the lowest reference concentration previously reported for cadmium-related kidney effects. Our results provide additional scientific support for the low tolerably weekly intake (TWI) of cadmium set by the European Food Safety Authority in 2009.

The effects of low environmental cadmium exposure on bone density

Recent epidemiological data indicate that low environmental exposure to cadmium, as shown by cadmium body burden (Cd-U), is associated with renal dysfunction as well as an increased risk of cadmium-induced bone disorders. The present study was designed to assess the effects of low environmental cadmium exposure, at the level sufficient to induce kidney damage, on bone metabolism and mineral density (BMD). The project was conducted in the area contaminated with cadmium, nearby a zinc smelter located in the region of Poland where heavy industry prevails. The study population comprised 170 women (mean age=39.7; 18-70 years) and 100 men (mean age=31.9; 18-76 years). Urinary and blood cadmium and the markers of renal tubular dysfunction (beta(2)M-U RBP, NAG), glomerular dysfunction (Alb-U and beta(2)M-S) and bone metabolism markers (BAP-S, CTX-S) as well as forearm BMD, were measured. The results of this study based on simple dose-effect analysis showed the relationship between increasing cadmium concentrations and an increased excretion of renal dysfunction markers and decreasing bone density. However, the results of the multivariate analysis did not indicate the association between exposure to cadmium and decrease in bone density. They showed that the most important factors that have impact on bone density are body weight and age in the female subjects and body weight and calcium excretion in males. Our investigation revealed that the excretion of low molecular weight proteins occurred at a lower level of cadmium exposure than the possible loss of bone mass. It seems that renal tubular markers are the most sensitive and significant indicators of early health effects of cadmium intoxication in the general population. The correlation of urinary cadmium concentration with markers of kidney dysfunction was observed in the absence of significant correlations with bone effects. Our findings did not indicate any effects of environmental cadmium exposure on bone density.

Interactions between concentrations of chemical elements in human femoral heads

Environmental and occupational exposure to various metals has been a major public health concern and the subject of many studies. With the development of industry and transportation, environmental pollution has markedly worsened. As a result, metals are now ubiquitous and are absorbed into the body with food, drinking water, and polluted air. Exposure to these elements leads to numerous health problems, affecting almost every system of the human body, including the skeletal system. Bone is a specific research material that is difficult to obtain, therefore chemical analyses of metal concentrations in this tissue are rarely found in the literature. Nevertheless, bone, due to its long regeneration period, can serve as a biomarker of a long-term metal accumulation resulting from environmental or occupational exposure. Our study was conducted on bone samples harvested from inhabitants of the Upper Silesia region during hip replacement surgery. Femoral heads removed during surgery were sectioned into slices and further subdivided into samples comprising articular cartilage, cortical bone, and trabecular bone. Concentrations of 12 trace elements were measured with an atomic absorption spectrophotometry method. We found significant correlation between concentrations of these metal elements in the samples of cortical bone. This is determined not only by the physiological functions of these metals in hydroxyapatite, but also by the specific mineral structure of the bone tissue.

Cadmium osteotoxicity in experimental animals: mechanisms and relationship to human exposures

Extensive epidemiological studies have recently demonstrated increased cadmium exposure correlating significantly with decreased bone mineral density and increased fracture incidence in humans at lower exposure levels than ever before evaluated. Studies in experimental animals have addressed whether very low concentrations of dietary cadmium can negatively impact the skeleton. This overview evaluates results in experimental animals regarding mechanisms of action on bone and the application of these results to humans. Results demonstrate that long-term dietary exposures in rats, at levels corresponding to environmental exposures in humans, result in increased skeletal fragility and decreased mineral density. Cadmium-induced demineralization begins soon after exposure, within 24 h of an oral dose to mice. In bone culture systems, cadmium at low concentrations acts directly on bone cells to cause both decreases in bone formation and increases in bone resorption, independent of its effects on kidney, intestine, or circulating hormone concentrations. Results from gene expression microarray and gene knock-out mouse models provide insight into mechanisms by which cadmium may affect bone. Application of the results to humans is considered with respect to cigarette smoke exposure pathways and direct vs. indirect effects of cadmium. Clearly, understanding the mechanism(s) by which cadmium causes bone loss in experimental animals will provide insight into its diverse effects in humans. Preventing bone loss is critical to maintaining an active, independent lifestyle, particularly among elderly persons. Identifying environmental factors such as cadmium that contribute to increased fractures in humans is an important undertaking and a first step to prevention.

Association of environmental cadmium exposure with periodontal disease in U.S. adults

BACKGROUND

Periodontal disease is a complex, multifactorial, chronic inflammatory disease that involves degradation of periodontal structures, including alveolar bone. Cadmium adversely affects bone remodeling, and it is therefore possible that environmental Cd exposure may be a risk factor for periodontal-disease-related bone loss.

OBJECTIVE

We examined the relationship between environmental Cd exposure and periodontal disease in U.S. adults.

METHODS

We analyzed cross-sectional data from the third National Health and Nutrition Examination Survey (NHANES III). We defined periodontal disease as clinical attachment loss of at least 4 mm in > 10% of sites examined. We used multivariable-adjusted logistic regression analyses to estimate the association between creatinine-corrected urinary Cd levels and periodontal disease.

RESULTS

Of the 11,412 participants included in this study, 15.4% had periodontal disease. The age-adjusted geometric mean urine Cd concentration (micrograms per gram creatinine) was significantly higher among participants with periodontal disease [0.50; 95% confidence interval (CI), 0.45-0.56] than among those without periodontal disease (0.30; 95% CI, 0.28-0.31). Multivariable-adjusted analyses, which included extensive adjustments for tobacco exposure, showed that a 3-fold increase in creatinine-corrected urinary Cd concentrations [corresponding to an increment from the 25th (0.18 microg/g) to the 75th (0.63 microg/g) percentile] was associated with 54% greater odds of prevalent periodontal disease (odds ratio = 1.54; 95% CI, 1.26-1.87). We observed similar results among the subset of participants who had limited exposure to tobacco, but only after removing six influential observations.

CONCLUSION

Environmental Cd exposure was associated with higher odds of periodontal disease.

Cadmium-induced bone effect is not mediated via low serum 1,25-dihydroxy vitamin D

Cadmium is a widespread environmental pollutant, which is associated with increased risk of osteoporosis. It has been proposed that cadmium's toxic effect on bone is exerted via impaired activation of vitamin D, secondary to the kidney effects. To test this, we assessed the association of cadmium-induced bone and kidney effects with serum 1,25-dihydroxyvitamin D (1,25(OH)(2)D); measured by enzyme immunoassay. For the assessment, we selected 85 postmenopausal women, based on low (0.14-0.39 microg/L) or high (0.66-2.1 microg/L) urinary cadmium, within a cross-sectional population-based women's health survey in Southern Sweden. We also measured 25-hydroxy vitamin D, cadmium in blood, bone mineral density and several markers of bone remodeling and kidney effects. Although there were clear differences in both kidney and bone effect markers between women with low and high cadmium exposure, the 1,25(OH)(2)D concentrations were not significantly different (median, 111 pmol/L (5-95th percentile, 67-170 pmol/L) in low- and 125 pmol/L (66-200 pmol/L) in high-cadmium groups; p=0.08). Also, there was no association between 1,25(OH)(2)D and markers of bone or kidney effects. It is concluded that the low levels of cadmium exposure present in the studied women, although high enough to be associated with lower bone mineral density and increased bone resorption, were not associated with lower serum concentrations of 1,25(OH)(2)D. Hence, decreased circulating levels of 1,25(OH)(2)D are unlikely to be the proposed link between cadmium-induced effects on kidney and bone.

Urinary cadmium and osteoporosis in U.S. Women >or= 50 years of age: NHANES 1988-1994 and 1999-2004

BACKGROUND

Urinary cadmium (U-Cd) has been associated with decreased peripheral bone mineral density (BMD) and osteoporosis. This association, however, has not been confirmed using femoral BMD, the international standard for diagnosing osteoporosis, at levels < 1.0 microg Cd/g creatinine.

OBJECTIVES

Our goal was to investigate the statistical association between U-Cd, at levels or= 50 years of age.

METHODS

We drew data from the National Health and Nutrition Examination Surveys for 1988-1994 (n = 3,207) and 1999-2004 (n = 1,051). Osteoporosis was indicated by hip BMD cutoffs based on the international standard and self-report of physician diagnosis. We analyzed U-Cd levels for association with osteoporosis using multiple logistic regression.

RESULTS

Women >or= 50 years of age with U-Cd levels between 0.50 and 1.00 microg/g creatinine were at 43% greater risk for hip-BMD-defined osteoporosis, relative to those with levels

CONCLUSIONS

Results suggest that U.S. women are at risk for osteoporosis at U-Cd levels below the U.S. Occupational Safety and Health Administration's 3-microg/g safety standard. Given null findings among smokers, dietary Cd, rather than tobacco, is the likely source of Cd-related osteoporosis risk for the U.S. female population >or= 50 years of age.

Collapse

Key Words

• bone mineral density
• cadmium
• femur
• hip
• osteoporosis
• women

Collapse

MESH Headings

• Aged
• Aged, 80 and over
• Bone Density
• Cadmium/urine
• Creatinine/urine
• Female
• Humans
• Middle Aged
• Nutrition Surveys
• Osteoporosis/epidemiology
• Osteoporosis/urine
• Regression Analysis
• United States/epidemiology

Collapse

Grants Collapse

Affiliation(s)

Carolyn M Gallagher Graduate Program in Public Health, Stony Brook University Medical Center, Stony Brook, New York 11790, USA.
John S Kovach
Jaymie R Meliker

Collapse

Bone resorption and environmental exposure to cadmium in women: a population study

BACKGROUND

Environmental exposure to cadmium decreases bone density indirectly through hypercalciuria resulting from renal tubular dysfunction.

OBJECTIVE

We sought evidence for a direct osteotoxic effect of cadmium in women.

METHODS

We randomly recruited 294 women (mean age, 49.2 years) from a Flemish population with environmental cadmium exposure. We measured 24-hr urinary cadmium and blood cadmium as indexes of lifetime and recent exposure, respectively. We assessed the multivariate-adjusted association of exposure with specific markers of bone resorption, urinary hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), as well as with calcium excretion, various calciotropic hormones, and forearm bone density.

RESULTS

In all women, the effect sizes associated with a doubling of lifetime exposure were 8.4% (p=0.009) for HP, 6.9% (p=0.10) for LP, 0.77 mmol/day (p=0.003) for urinary calcium, -0.009 g/cm(2) (p=0.055) for proximal forearm bone density, and -16.8% (p=0.065) for serum parathyroid hormone. In 144 postmenopausal women, the corresponding effect sizes were -0.01223 g/cm(2) (p=0.008) for distal forearm bone density, 4.7% (p=0.064) for serum calcitonin, and 10.2% for bone-specific alkaline phosphatase. In all women, the effect sizes associated with a doubling of recent exposure were 7.2% (p=0.001) for urinary HP, 7.2% (p=0.021) for urinary LP, -9.0% (p=0.097) for serum parathyroid hormone, and 5.5% (p=0.008) for serum calcitonin. Only one woman had renal tubular dysfunction (urinary retinol-binding protein >338 microg/day).

CONCLUSIONS

In the absence of renal tubular dysfunction, environmental exposure to cadmium increases bone resorption in women, suggesting a direct osteotoxic effect with increased calciuria and reactive changes in calciotropic hormones.

Estimation of Polish cigarettes contamination with cadmium and lead, and exposure to these metals via smoking

To estimate exposure to cadmium (Cd) and lead (Pb) through cigarette smoking, the concentrations of both metals in the blood or/and urine of smokers (20 cigarettes or more per day for 10 years or longer) and their non-smoking counterparts inhabiting an environmentally unpolluted area (Bialystok, Poland) were evaluated, as well as Cd and Pb contents in the cigarette brands (produced in Poland) smoked by the participants, including intact cigarettes, pre-smoking (tobacco, paper and filter) and post-smoking (butt, ash and smoke) cigarette components. Blood and urinary Cd concentrations in the smokers have been already reported by us to be 2-4 times higher than in the non-smokers (Galazyn-Sidorczuk et al. Polish Journal of Environmental Studies, 13 (Suppl.1):91-95, 2004). All the other measurements are the subject of the present paper. Pb concentration in the blood of the cigarette smokers (52.12 +/- 15.51 microg l(-1)) was higher by 29% than in the non-smokers (40.42 +/- 11.19 microg l(-1)). The mean Cd and Pb contents in the cigarettes were 0.6801 +/- 0.1765 and 0.6853 +/- 0.0746 microg per cigarette, respectively. Under cigarette burning, performed using a machine for self-acting burning, on average 33% of Cd and 11% of Pb present in the whole cigarette was released into the smoke. For Cd, unlike Pb, there was a high positive correlation between the metal content in cigarettes and tobacco and its release into the smoke. Moreover, the subjects smoking cigarettes containing the highest Cd amount had higher blood Cd concentration than smokers of other cigarette brands. The results give clear evidence that in the case of inhabitants of areas unpolluted with Cd and Pb habitual cigarette smoking, due to tobacco contamination, creates a serious source of chronic exposure to these metals, especially to Cd.