Cd Body Burden Research Articles

Effects of Variations in Cadmium and Lead Levels in River Sediments on Local Foods and Body Burden of Local Residents in Non-Polluted Areas in Japan

This study was initiated to examine if variations in the concentrations of cadmium (Cd) and lead (Pb) in water environment may affect metal levels in local foods and body burden of local residents in non-polluted areas in Japan. Two nationwide databases have been made available on concentrations of Cd in locally harvested brown rice and of Cd and Pb in sediments in local river beds. These data were combined with published data on metal concentrations in polished rice, food duplicates, and blood and urine from the residents. Cd in river sediments correlated significantly with those in brown rice, food duplicates, blood, and urine. Cd in food duplicates correlated with Cd in rice. In contrast, Pb concentrations in the river sediments either did not correlate or correlated only weakly with Pb in biological materials or food duplicates. Possible implication of the different behavior between Cd and Pb regarding the intensity of correlation was discussed with reference to the different routes of exposure to the elements. In conclusions, the Cd body burden on local residents in Japan is significantly influenced by Cd levels in water in the general environment, whereas water-borne Pb did not show clear correlation with the Pb body burden.

Human retinal cadmium accumulation as a factor in the etiology of age-related macular degeneration

Cadmium is a naturally occurring, highly toxic, metallic element. It pollutes the environment as a result of industrial activity and accumulates in human tissues with a long biological half-life. Cadmium content has been demonstrated to increase in human retinal tissues as a function of age and tobacco smokers have approximately twice as much cadmium in retinal tissues than non-smokers. Smoking is also a key environmental risk factor for the retinal disease age-related macular degeneration (AMD). Recent studies have shown that urinary cadmium levels (a measure of Cd body burden) are higher in smokers who have AMD. We now report the Cd measurements in human retinal tissues from eyes afflicted with AMD compared to non-diseased eyes (controls) from age-matched donors. Human donor eyes frozen under argon gas were assessed for AMD severity using color stereoscopic fundus photographs and the Minnesota Grading System. Cadmium, zinc and, copper levels were measured in retinal tissues (neural retina, retinal pigment epithelium and choroid) using inductively coupled plasma mass spectrometry and graphite furnace spectrophotometry and values were normalized to tissue protein levels. Higher Cd levels were found in the neural retina and RPE for eyes afflicted with AMD compared to controls in males, differences were not statistically significant in females. The results indicate that higher retinal cadmium burdens are associated with the presence of AMD at least in males and suggest possible gender differences in the metabolism of metals in the human retina.

Metal accumulation and biomarker responses in Daphnia magna following cadmium and zinc exposure

Metal accumulation (quantified as body burden) and the responses of two biomarkers (metallothionein [MT] induction and superoxide dismutase [SOD] activity) in a freshwater cladoceran Daphnia magna were quantified after being exposed to different concentrations of Cd and Zn for 3 d. The Cd and Zn body burdens increased with increasing exposure concentrations. The responses of biomarkers were metal-specific and concentration-dependent. As a detoxification mechanism, MT was induced by exposure to Cd or Zn or Cd + Zn and was dependent on the exposure concentrations. Low concentrations of Cd or Zn exposure increased the SOD activity, which was, however, inhibited at higher metal exposure concentrations. Metallothionein concentrations in daphnids were significantly related to the metal body burden. The SOD activity was inversely related to Cd body burden, while it was independent of the Zn body burden. Survivorship of D. magna was high at lower Cd/MT ratios in the animals but then decreased linearly when the ratio exceeded six. In contrast, the relationship between survivorship and Zn/MT ratio was different due to the essentiality of Zn. Overall, MT induction was a useful indicator of metal pollution in cladocerans.

CRITICAL PERIOD OF SENSITIVITY FOR EFFECTS OF CADMIUM ON FROG GROWTH AND DEVELOPMENT

Cadmium is a ubiquitous pollutant in aquatic environments that can alter organismal physiology and ecology. Previous experiments found that ecological Cd exposures increased the growth and development of two North American anurans. However, the generality of these effects among species, the time period over which they occur, and the mechanisms responsible remain conjectural. The goal of the present study was to determine the critical period of sensitivity of Rana pipiens exposed to ecologically relevant levels of Cd. We exposed tadpoles to Cd (0 [control], 1.0, and 10.0 microg/L) from Gosner stage (GS) 25 to metamorphic climax. We assessed effects of Cd on amphibian length, survival, and development during premetamorphosis (GS 25-30) and prometamorphosis (GS 31-42). After 14 d of exposure, we staged tadpoles and recorded snout-vent length. Tadpoles were then pooled according to treatment and stage (GS < or =29 or GS > or =30) and allowed to undergo metamorphic development. Tadpoles exposed to 10 microg/L were significantly larger and more advanced in development by 14 d. Survival to forelimb emergence exceeded 90% in all treatments, and time to metamorphic climax was not different from that in controls. Body burdens of Cd were positively correlated with increasing treatment. Early amphibian development (premetamorphosis) was shown to be the critical period of sensitivity for growth and development. Whereas the freshwater criterion for Cd appears to be protective for survival, a lack of knowledge remains about the sublethal effects of chronic exposures of metal pollutants, especially as they relate to tissue concentrations at various stages of amphibian life history.

Metallothioneins 2 and 3 contribute to the metal-adapted phenotype but are not directly linked to Zn accumulation in the metal hyperaccumulator, Thlaspi caerulescens.

To study the role of metallothioneins (MTs) in Zn accumulation, the expression of TcMT2a, TcMT2b, and TcMT3 was analysed in three accessions and 15 F3 families of two inter-accession crosses of the Cd/Zn hyperaccumulator Thlaspi caerulescens, with different degrees of Zn accumulation. The highest expression levels were found in the shoots of a superior metal-accumulating calamine accession from St Laurent le Minier, with >10-fold TcMT3 expression compared with another calamine accession and a non-metallicolous accession. Moreover, F3 sibling lines from the inter-accession crosses that harboured the MT2a or MT3 allele from St Laurent le Minier had higher expression levels. However, there was no co-segregation of TcMT2a or TcMT3 expression and Zn accumulation. To examine the functions of TcMTs in plants, TcMT2a and TcMT3 were ectopically expressed in Arabidopsis. The transformant lines had reduced root length in control medium but not at high metal concentrations, suggesting that the ectopically expressed proteins interfered with the physiological availability of essential metals under limited supply. The Arabidopsis transformant lines did not show increased tolerance to Cd, Cu, or Zn, nor increased Cd or Zn accumulation. Immunohistochemical analysis indicated that in roots, MT2 protein is localized in the epidermis and root hairs of both T. caerulescens and Arabidopsis thaliana. The results suggest that TcMT2a, TcMT2b, and TcMT3 are not primarily involved in Zn accumulation as such. However, the elevated expression levels in the metallicolous accessions suggests that they do contribute to the metal-adapted phenotype, possibly through improving Cu homeostasis at high Zn and Cd body burdens. Alternatively, they might function as hypostatic enhancers of Zn or Cd tolerance.

Early kidney damage in a population exposed to cadmium and other heavy metals.

BackgroundExposure to heavy metals may cause kidney damage. The population living near the Avonmouth zinc smelter has been exposed to cadmium and other heavy metals for many decades.ObjectivesWe aimed to assess Cd body burden and early signs of kidney damage in the Avonmouth population.MethodsWe used dispersion modeling to assess exposure to Cd. We analyzed urine samples from the local population (n = 180) for Cd (U-Cd) to assess dose (body burden) and for three biomarkers of early kidney damage [N-acetyl-β-d-glucosaminidase (U-NAG), retinol-binding protein, and α-1-microglobulin]. We collected information on occupation, intake of homegrown vegetables, smoking, and medical history by questionnaire.ResultsMedian U-Cd concentrations were 0.22 nmol/mmol creatinine (nonsmoking 0.18/smoking 0.40) and 0.34 nmol/mmol creatinine (nonsmoking 0.31/smoking 0.46) in non-occupationally exposed men and women, respectively. There was a significant dose–response relationship between U-Cd and the prevalence of early renal damage—defined as U-NAG > 0.22 IU/mmol—with odds ratios of 2.64 [95% confidence interval (95% CI), 0.70–9.97] and 3.64 (95% CI, 0.98–13.5) for U-Cd levels of 0.3 to < 0.5 and levels ≥ 0.5 nmol/mmol creatinine, respectively (p for trend = 0.045).ConclusionU-Cd concentrations were close to levels where kidney and bone effects have been found in other populations. The dose–response relationship between U-Cd levels and prevalence of U-NAG above the reference value support the need for measures to reduce environmental Cd exposure.

The influences of ambient and body calcium on cadmium and zinc accumulation in Daphnia magna

The dissolved uptake rate constant (k(u)), dietary assimilation efficiency (AE), and efflux rate constant (k(e)) of cadmium (Cd) and zinc (Zn) were quantified in a freshwater zooplankton Daphnia magna cultured at different ambient calcium (Ca) concentrations. The animals were first acclimated to different ambient Ca levels for 7 d from birth before the biokinetic measurements at corresponding Ca levels. With increasing ambient Ca level from 0.5 to 200 mg/L, the body Ca content increased from 0.91% (as tissue dry wt) to 3.75%. The k(u) for Cd decreased by nine times; for Zn it decreased by 2.6 times; and the AE decreased from 62 to 19% and from 46 to 24% for Cd and Zn, respectively. In contrast, Ca levels did not affect significantly the efflux rates of Cd and Zn. The effects of ambient and body Ca levels were separated by measuring the biokinetic parameters in both low--(0.5 mg/L) and high--(50 mg/L) Ca environments using the daphnids containing different body Ca levels. Ambient and body Ca levels had synergistic inhibitory effects on the AEs of Cd and Zn; however, the protective effects against dissolved uptake of Cd and Zn were explained fully by the effects of ambient Ca. The body Ca either had no significant effect (for Cd) or stimulative effects (for Zn). Multiphase biokinetic modeling using the measured parameters gave reasonable predictions of the body burdens of Cd and Zn in different Ca environments. Our results better explain the role of ambient and body Ca in the accumulation of Cd and Zn in D. magna.

Decoupling of cadmium biokinetics and metallothionein turnover in a marine polychaete after metal exposure

This study investigated the kinetics of Cd bioaccumulation, detoxification, subcellular distribution, and efflux in the nereid polychaete Perinereis aibuhitensis after Cd pre-exposure. Cd pre-exposure increased the Cd body burden in the worms, but did not affect the overall Cd uptake and efflux rates and metallothionein-like protein (MTLP) concentrations. During short-term exposure to dissolved Cd, Cd in the cytosolic fraction increased after Cd pre-exposure, and this fraction also increased during the Cd efflux period, indicating that the insoluble fraction of Cd was presumably lost at a faster rate than the loss of cytosolic Cd. Even though the MTLP concentration remained comparable after Cd pre-exposure, both the MTLP synthesis rate and the degradation rate increased, thus leading to a high MTLP turnover in the Cd-exposed worms. However, Cd uptake and efflux into different protein size fractions did not follow the patterns of MTLP synthesis and degradation, strongly suggesting that Cd kinetics is decoupled from the MTLP kinetics in the worms. Our study adds to an increasing body of evidence on the complicated relationship between metal biokinetics and MTLP kinetics in different groups of marine invertebrates which have strong contrasts in their metal handling strategies.

Effects of chronic dietary and waterborne cadmium exposures on the contamination level and reproduction of daphnia magna

Regulatory assessments of metal toxicity on freshwater organisms assume that toxic effects are caused by dissolved metals. In aquatic systems, organisms are exposed to both dissolved and particulate-bound metals. In this study, the chronic toxicity of dietary cadmium (Cd) on the reproduction and Cd body burden of Daphnia magna was investigated. Daphnids (<24 h) were successively exposed to dissolved Cd (8 h) and then to uncontaminated or contaminated algae (16 h) for 21 d. The results show a higher Cd burden in daphnids because of the addition of contaminated food and reveal that Cd uptake by D. magna from water and food was additive for the lowest Cd concentrations tested. Similar Cd distributions (cytosolic and insoluble fractions) were observed in the two groups of organisms, showing similar potential toxicity of Cd accumulated from the two exposure routes. Dietary Cd induces deleterious effects on D. magna reproduction. On the basis of Cd body burden of daphnids, the results support the claim that waterborne and dietary Cd exposures were additive in causing toxicity for Cd concentrations lower than 25 microg/L. At the highest Cd concentrations, the importance of dietary Cd on the daphnid contamination level decreases and confounding factors such as feeding rate reduction seem to appear, which induce an effect on neonate reproduction. In this study, we illustrate the need to take the dietary pathway into account in regulatory assessments and to establish effective concentrations with particulate-bound metals.

Effects of multiple effluents on resident fish from Junction Creek, Sudbury, Ontario

Junction Creek in Sudbury, Ontario, Canada receives effluent from three metal mining effluents (MMEs), as well as urban run-off and municipal sewage treatment plant (STP) discharges. The present study examined organismal and sub-organismal end-points in prespawning fathead minnow (FHM; Pimephales promelas) and creek chub (CC; Semotilus atromaculatus) collected in May 2004 from Junction Creek. Metal body burdens of Cd, Cu, Rb, Se, and Sr increased in a gradient down Junction Creek in both species. In general, male fish had lower body weights downstream of effluents, while females were unchanged or larger compared to reference fish. Livers were larger in FHM of both sexes downstream of STP and in CC downstream of two MMEs compared to reference fish, while gonad weight was unchanged. The most consistent finding was delayed development, increased cell death and increased eosinophilia in FHM testes collected downstream of all effluents, while female FHM and both sexes of CC gonads were relatively unaffected. In conclusion, the results of the current study in Junction Creek suggest that male FHM reproduction may be sensitive to multiple effluents, but failed to clearly establish whether MME or STP effluents were causative agents over urban inputs or historical contamination.

Urinary Cadmium and Age-related Macular Degeneration

To evaluate the association between urinary and blood cadmium (Cd) levels with age-related macular degeneration (AMD). Prospective case-control study. In 53 participants older than 60 years with AMD in both eyes and in 53 age-matched (+/- 3 years) controls without AMD, Cd levels were measured in blood and urine specimens (with and without creatinine adjustment) by using inductively coupled plasma-mass spectrometry. Data on age, gender, smoking status, and family history were obtained. By using color stereoscopic fundus photographs, the degree of AMD was graded using the Age-Related Eye Disease Study's 4-stage AMD severity scale. The inclusion criterion for AMD cases was a photographic severity level of two to four in both eyes. Median blood and urine Cd and median urine Cd/creatinine concentrations in cases and controls were compared by using the rank-sum test, stratifying for smoking status. Current and former smokers with AMD had median urine Cd/creatinine levels (1.18 microg/g; range, 0.84 to 1.44 microg/g) that were 97% higher than smokers without AMD (0.60 microg/g; range, 0.49 to 0.90 microg/g; P = .02), 111% higher than never smokers with AMD (0.56 microg/g; range, 0.40 to 0.80 microg/g; P < .001) and 107% higher than never smokers without AMD (0.57 microg/g; 0.40 to 0.65 microg/g; P < .001). Blood Cd levels, indicative of short-term exposure levels, were not associated with AMD (P >/= .06). A higher urinary Cd level, which reflects the total body burden of Cd, was associated with AMD in smokers. Accumulated Cd exposure may be important in the development of smoking-related AMD.

Lethal and sublethal effects of chronic cadmium exposure on northern leopard frog (Rana pipiens) tadpoles

Data on the chronic effects of cadmium on amphibians are lacking in spite of widespread anthropogenic contamination of terrestrial and aquatic systems. We exposed embryos and tadpoles of northern leopard frogs (Rana pipiens) to Cd (control, 0.25, 5.0, and 20.0 microg/L as CdCl2, nominal concentrations) in a static renewal system from embryonic stages to complete tail resorption. Survival of embryos (Gosner stage [GS] 17-25) was greater than 97% in all treatments. Tadpole survival was negatively correlated with dose and was significantly reduced in the 5.0 and 20.0 microg/L treatments compared with controls. Tadpole survival was greater than 80% through GS 42, forelimb emergence, for all other treatments. Tadpoles exposed to 0.25 and 5.0 microg/L exhibited increased growth by week 11; tadpoles exposed to 5.0 microg/L were significantly younger at forelimb emergence. Whole-tadpole body burdens of Cd were positively correlated with increasing Cd treatments. Cadmium was shown to alter growth and development in a native amphibian species at ecologically relevant concentrations. The existing chronic water quality criterion for Cd appears to be protective of amphibians. However, additional studies with other chemicals are needed to further explore the potential for adverse effects of contaminants on the complex life cycle of amphibians.

24-Hour Provoked Urine Excretion Test for Heavy Metals in Children with Autism and Typically Developing Controls, a Pilot Study

Introduction. The complementary and alternative medicine practice of prescribing chelators to children with autism is based on the premise that the chronic symptoms of autism can be ameliorated by reducing heavy metal body burden. However, there has not been definitive evidence, published to date, to support the assertion that children with autism are at increased risk of an excess chelatable body burden of heavy metals. The oral chelator meso-2,3-dimercaptosuccinic acid (DMSA) can be used diagnostically to mobilize heavy metals from extravascular pools, enhancing the identification of individuals who have a chelatable body burden. Methods. Seventeen children with autism and five typically developing children were enrolled in a pilot study to test for chelatable body burden of Arsenic (As), Cadmium (Cd), Lead (Pb), and Mercury (Hg). Evaluation included a questionnaire regarding potential exposure to heavy metals, diet restrictions, a baseline 24-hour urine collection, and a DMSA-provoked urine collection. Urine collections were sent for As, Cd, Pb, and Hg quantification by Inductively Coupled Plasma-Mass Spectrometry. Unprovoked reference ranges were used in the interpretation of all collections. Results. Fifteen autistic children and four typically developing children completed the study. Three autistic subjects excreted one metal in greater quantity during the provoked excretion than baseline. Two of these were very close to the limit of detection. In the third case, the provoked excretion of mercury was between the upper limit of normal and lower limit of the potentially toxic reference range. Fish was removed from this child's diet for greater than one month, and the provoked excretion test repeated. The repeat excretion of mercury was within the normal range. Conclusion. In the absence a proven novel mode of heavy metal toxicity, the proportion of autistic participants in this study whose DMSA provoked excretion results demonstrate an excess chelatable body burden of As, Cd, Pb, or Hg is zero. The confidence interval for this proportion is 0–22%.

Chronic exposure of mice to environmentally relevant, low doses of cadmium leads to early renal damage, not predicted by blood or urine cadmium levels

Mice were exposed to cadmium (Cd) concentrations ranging from 0 to 100mg CdCl2/l in the drinking water for 1, 4, 8, 16 and 23 weeks. Urine samples were taken regularly, Cd content was determined in blood, liver, kidney and urine and histological analyses of the kidney were performed.Kidney cortex Cd content increased linearly with time and dose, while blood levels reached a plateau at 8 weeks and liver at 16 weeks in mice exposed to 100mg CdCl2/l after which both started to decrease. Urinary Cd levels were not correlated with the kidney Cd content.A multivariate regression model taking into account the actual Cd intake, calculated from the volume of water taken in by each animal and the exposure concentration, confirmed that blood is an indicator of acute exposure, while kidney Cd content is a reliable indicator of chronic exposure. The urinary protein content was significantly increased from 16 weeks on in mice exposed to 100mg CdCl2/l (p<0.05), while other signs of proximal tubular damage (glucosuria, enzymuria) were not detected. Histologically more vacuoles and lysosomes were present in the proximal tubule cells with increasing time and dose.The results indicate that chronic exposure to low doses of Cd induced functional and histological signs of early damage at concentrations in or below the ones generally accepted as safe. Our study does not corroborate the statement that urine Cd levels are a reliable indicator of total Cd body burden, at least when the body burden is low.

Importance of metallothioneins in the cadmium detoxification process in Daphnia magna

Good knowledge of the relationship between toxic metals and biological systems, particularly the sub-cellular fraction, could be a suitable early indicator of toxic effects. These effects and the sub-cellular behaviour of cadmium were studied with a widely used species in freshwater toxicity bioassays, Daphnia magna. In spite of this very commonplace usage in ecotoxicological studies, very few data are available on its toxicant metabolism and in particular metal homeostasis. Combining multi-tools analysis, a soluble protein was found: it is heat-stable, rich in sulfhydryl groups (differential pulse polarography), characterised by a molecular mass of approximately 6.5 kDa, with a G-75 chromatographic profile corresponding to the rabbit metallothioneins monomer, with few if any aromatic-containing amino acids, it binds metals (e.g. Cd, Cu), and its concentration increases with Cd exposure. This evidence led us to hypothesise that metallothioneins (MTs) are present in D. magna. Up to 75% of the Cd body burden with Cd exposure is bound to the MTs fraction. The increase in the Cd concentration in the surrounding medium and concomitantly in daphnids induces sub-cellular reorganisation of essential metals such as Cu and Zn. The rate of metals in the soluble cellular fraction and associated with MTs increases with the Cd body burden. Monitoring sub-cellular distribution of metals after exposure in the natural environment could be very useful for ecotoxicological assessment.

Alteration of dissolved cadmium and zinc uptake kinetics by metal pre‐exposure in the black sea bream (Acanthopagrus schlegeli)

We first examined the uptake kinetics of Cd and Zn in the juvenile marine black sea bream (Acanthopagrus schlegeli) over a wide range of ambient Cd and Zn concentrations, and the relationships with metal accumulation (uptake rate and amount of nonexchangeable surface binding) were established for different fish tissues. Both Cd and Zn accumulation in the body increased linearly with exposure time after the initial metal surface binding. The dissolved Cd and Zn uptake rate constants were 2.64 and 6.50 L/kg/d, respectively, and the kinetics followed a first-order process. No evidence of biphasic transport was found, in contrast to the situation in freshwater fish. Viscera were the most important sites of metal uptake, and gills were the second most important sites. The black sea breams were then acclimated at different Cd or Zn concentrations from either waterborne or dietary source for one week, and the alteration of metal uptake kinetics or subcellular distribution and metallothionein (MT) induction were further quantified. The Cd body burden was enhanced up to 8.6- and 49-fold after waterborne and dietary Cd pre-exposure, respectively. Cadmium pre-exposure also altered the tissue-specific subcellular Cd distribution and significantly elevated tissue MT levels. In contrast, the black sea breams were able to regulate Zn accumulation, and waterborne or dietary Zn pre-exposure had only weak influences on Zn body burden and redistribution. Both Cd and Zn pre-exposures enhanced the metal uptake rate constants, whereas the nonexchangeable surface bindings were less impacted by these pre-exposures. We demonstrated a positive relationship between the Cd uptake rate and Cd or MT concentration in the fish. Pre-exposure to metals may substantially modify the kinetics of metal uptake.

Influence of metal exposure history on the bioaccumulation and subcellular distribution of aqueous cadmium in the insect Hydropsyche californica

The influence of metal exposure history on rates of aqueous Cd accumulation, elimination, and subcellular distribution was examined in the aquatic insect Hydropsyche californica. Specimens were obtained from a reference site and a metal-contaminated site and returned to the laboratory where they were continuously exposed to aqueous Cd (518 ng/L, nominal) for 6 d, followed by 9 d of depuration. Rates of Cd accumulation and elimination were similar in insects from the two sites. Efflux rate constants, k((e), ranged from 0.20 to 0.24/d (t 1/2 approximately 3 d). Immediately following exposure, the cytosol accounted for 40% of the body burden in insects from both sites; however, 89 +/- 2% of the cytosolic Cd was associated with metallothionein-like proteins (MTLP) in insects from the contaminated site, compared to 60 +/- 0% in insects from the reference site. The concentration of Cd bound to non-MTLPs (representing potentially Cd-sensitive proteins) was significantly greater in the insects from the reference site (134 +/- 7 ng/g) than in those from the contaminated site (42 +/- 2 ng/g). At the end of the depuration period, 90% of the accumulated Cd body burden had been eliminated, and Cd concentrations in MTLPs and non-MTLPs were similar between the sites. Results suggested that differences in exposure history had no influence on the bioaccumulation of Cd, but did affect the concentrations of Cd bound to MTLP during Cd exposure in these insects.

Correlation among cadmium levels in river sediment, in rice, in daily foods and in urine of residents in 11 prefectures in Japan

The objective of this study is to examine if overall correlation exists among cadmium levels (Cd) in the general environment, dietary Cd intake, and Cd body burden of local residents. Eleven prefectures in Japan were selected as the areas where large-scale data on Cd levels in urine of adult women (40-49 and 50-59 years of age, respectively) were available to calculate geometric mean (GM) values for each of the prefecture. Other data were cited from published or previously established databases on Cd in the sediments of river bottoms (as a representative of Cd in the environment), Cd in rice for local consumption, and Cd in daily food duplicate samples collected from local women populations, and calculated for GM values for the prefectures. The GM values were subjected to correlation matrix and regression analysis. Marginally significant (P < 0.10) correlation was detected between Cd in sediment and Cd in rice. Furthermore, correlation of Cd in sediment was significant with Cd in total foods (P < 0.05) and possibly with Cd in urine (P < 0.05-0.10). Importance of data on Cd in rice paddy soil as a missing link is discussed. Correlation was demonstrated in the flow of Cd transport from the environment (expressed as Cd contents in river sediments) to humans (in terms of Cd in urine) among general populations in Japan.

Urinary cadmium and mortality among inhabitants of a cadmium-polluted area in Japan

The influence of cadmium (Cd) body burden on mortality remains controversial. Excess mortality and the dose–response relationship between mortality and urinary cadmium excretion were investigated in this study among environmentally exposed subjects. A 15-year follow-up study was carried out on 3119 inhabitants (1403 men and 1716 women) of the Cd-polluted Kakehashi River basin, whose urinary Cd concentration was examined in a 1981–1982 health impact survey. The mortality risk of high urinary Cd (⩾10 μg/g Cr) subjects after adjustment for age using Cox's proportional hazard model was higher than that of moderate urinary Cd (<10 μg/g Cr) subjects in both sexes. When the subjects were divided into five groups according to the amount of urinary Cd (<3, 3–5, 5–10, 10–20, ⩾20 μg/g Cr), the mortality risk was significantly increased among the subjects with urinary Cd⩾3 μg/g Cr in proportion to the increases in the amount of urinary Cd concentration after adjustment for age, especially in women. Furthermore, special causes of death among high and moderate urinary Cd were investigated, and mortality risk ratio for heart failure, which is a cause of death often diagnosed in cases with a gradual deterioration culminating in death, was significantly increased in both sexes, compared with the moderate urinary Cd subjects. Also, in women the mortality risk for renal diseases in the high urinary Cd subjects was significantly higher than that in the moderate urinary Cd subjects. These results suggest that a causal association between Cd body burden and mortality exists among inhabitants environmentally exposed to Cd but that no special disease may be induced except renal diseases.

The toxicokinetics of cadmium in carp under normoxic and hypoxic conditions

Temporal depletion of oxygen, i.e. hypoxic events, frequently occurs in natural waters. It has been suggested that accumulation of micro-pollutants increases in aquatic animals as a result of an increased ventilation rate during such occasions. The observed increased toxicity under hypoxia of micro-pollutants may support this hypothesis, but for heavy metals the available uptake studies are contradictory. The present study tests whether accumulation of cadmium in common carp, Cyprinus carpio (L.) is increased under hypoxia and if the toxicokinetics are altered. A cadmium toxicity study was performed in which the cadmium uptake rates were determined using the radiotracer 109Cd under hypoxia and normoxia. The cadmium toxicokinetics were studied with radiotracer experiments at 100% air saturation, 50%, and 25% saturation from 6.5 nmol/L Cd at 25 °C. We could confirm the higher sensitivity of carp to cadmium under hypoxia. Hypoxic conditions did not influence the uptake rates or the accumulation dynamics. Therefore, the increased sensitivity of carp for Cd under hypoxia cannot be explained by a higher Cd body burden, initiated by a higher uptake rate or lower elimination rate under hypoxia. Additional, possible indirect effects, such as internal anoxia due to gill damage, could play a role in Cd toxicity under hypoxia.