Changes In Cd Concentrations Research Articles

Distribution characteristics of selenium, cadmium and arsenic in rice grains and their genetic dissection by genome-wide association study.

High selenium (Se) and low cadmium (Cd) and arsenic (As) contents in rice grains were good for human health. The genetic basis and relationship of Se, Cd and As concentrations in rice grains are still largely unknown. In the present study, large variations were observed in Se, Cd and As concentrations in brown and milled rice in normal and Se treatment conditions in 307 rice accessions from 3K Rice Genomes Project. Se fertilizer treatment greatly increased Se concentrations but had no obvious changes in concentrations of Cd and As both in brown and milled rice. Total of 237 QTL were identified for Se, Cd and As concentrations in brown and milled rice in normal and Se treatment conditions as well as ratio of concentrations under Se treatment to normal conditions. Only 19 QTL (13.4%) were mapped for concentrations of Se and Cd, Se and As, and Se, Cd and As in the same or adjacent regions, indicating that most Se concentration QTL are independent of Cd and As concentration QTL. Forty-three favorable alleles were identified for 40 candidate genes by gene-based association study and haplotype analysis in 14 important QTL regions. Se-enriched rice variety will be developed by pyramiding favorable alleles at different Se QTL and excluding undesirable alleles at Cd and As QTL, or combining favorable alleles at Se QTL with the alleles at Se-sensitive QTL by marker-assisted selection.

China national food safety standards of cadmium in staple foods: Issues and thinking

<p indent="0mm">Cadmium (Cd), as a class one carcinogen, is easily transferred from soil to the food chain, representing a potential threat to human health. Rapid industrialization in China during the last three decades has caused widespread contamination in agricultural soils. As a result, a considerable proportion of the rice grain in some areas of southern China has concentrations of Cd exceeding the Chinese food safety standard. This problem has raised a widespread concern regarding food safety and brought a big debate in China about whether the current food safety standard is reasonable. The food safety standard of Cd is not only critical for assessing soil environmental quality, but also important to reduce the current elevated dietary Cd intake for the general population. In this perspective, we summarize the history of establishment and revision in Chinese food safety standards of Cd in staple foods and discuss whether the current Cd safety limits for both rice and wheat are reasonable in terms of the tolerable limit for dietary Cd intake, dietary pattern, the current exposure level of Cd for the general pollution, and social-economic and international trading factors. The dietary Cd intake for the general population has doubled over the last <sc>25 years,</sc> from <sc>13.8 μg/d</sc> in 1990 to <sc>32.7 μg/d</sc> in 2011–2015, with the latter being approximately 61% of the provisional tolerable intake recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The growing body of evidence suggests no safe Cd intake limit for human health and consequently, dietary intake of Cd should be reduced as much as possible. The milling (i.e., polishing) process has an uncertain effect on change in Cd concentration in polished rice compared to the brown rice because of the uncertainty of the Cd spatial distribution pattern in rice grain. Furthermore, polished rice has higher bioavailability of Cd to humans than brown rice. These differences should be considered when extrapolating the food safety standard between brown rice and polished rice. According to the current exposure level and risk of Cd through consumption of rice, we contend that the current food safety limit for rice grain <sc>(0.2 mg/kg)</sc> in China is lenient for both the southern and northern general populations. It is unadvisable to be looser in further revisions of Chinese food safety standards. For wheat grain, the current safety limit <sc>(0.1 mg/kg)</sc> is reasonable for the northern population but strict for the southern population. Given the current contamination status and national food security and safety, the principle of ALARA (as low as reasonably achievable) should be applied to guild the amendment of the national food safety standard of Cd. There are several scientific perspectives to be further studied. First, epidemiological studies are required to establish the tolerable intake limit suitable to the Chinese ethnic characteristics and dietary patterns. Second, the new food safety standard should consider the subgroup populations with high Cd exposure risk, including infants, children, and local farmers who mainly consume home-grown rice with elevated Cd concentrations in Cd-contaminated regions. To reduce Cd exposure to the local population, effective mitigation strategies include exchanging high Cd home-grown rice with low Cd rice and increasing dietary nutrients and human nutrition.

The Response of Thiols to Cadmium Stress in Spinach (Spinacia Oleracea L.).

The aim of this study is to examine the thiol species for the high cadmium (Cd) tolerance of spinach and provide information for the improvement of soil utilization. The spinach was cultured in aqueous solution with concentrations of Cd ranging from 1 to 9 mg/L. The time responses of glutathione (GSH) and phytochelatins (PCs, PC2-PC4) in the tissues of spinach were monitored via HPLC–MS/MS, and the concentrations of Cd in the roots, shoots and leaves were detected by ICP–OES. Data were analyzed via one-way ANOVA and Spearman correlation to assess the relationships among the types of thiols and the changes between types of thiols and Cd. As Cd stress increased, Cd concentrations in tissues also increased. The total thiol contents responded to Cd stresses with correlations r ranging from 0.394 (root), 0.520 (shoot) to 0.771 (leaf) (p < 0.01). GSH and PC3 were dominant on most of the days under Cd stress. The correlation r between improvements in GSH and increments of Cd concentration in roots was −0.808 (p < 0.01), and r between changes in PC3 and changes in Cd concentrations in leaves was −0.503 (p < 0.01). No correlation can be found between GSH and the subtypes of PCs in shoots, but strong positive correlations within the subtypes of PCs. Thiols can be produced in different tissues of spinach, while the shoots are only a transport tissue for GSH.

ISOLATION AND DIAGNOSIS OF CADMIUM-RESISTANT BACTERIA AND ITS POTENTIAL PHYTOREMEDIATION WITH THE BROAD BEAN PLANT

Results of the study proved that phytoremediation can be a promising technique to treat cadmium (Cd)-contaminated soil. Four bacteria types were isolated from the soil; two are autotrophic and others are heterotrophic. Autotrophic bacteria were dominant in soils with 42 mg Cd Kg-1. The total count and diversity of both bacteria types decreased with the increase of Cd in media and reached their minimum limit of tolerance at 60 mg Cd L-1 in terms of the heterotrophic bacteria, while the minimum limit of tolerance in the case of autotrophic bacteria was at 110 mg Cd L-1. The four isolates can form biofilms that ranged in thickness between 2.8–4.3 mm. The tolerant isolates belong to Rhizobium leguminosarum, Pseudomonas fluorescens, Actinobacteria, and Corynebacterium. Shoot and dry weight significantly varied according to the changes in Cd concentrations and isolate types. The level in either shoot or root exceeded critical levels, however, its concentration was higher in the root compared with the shoot. The effect of Cd on broad bean plants began at 80 and 100 mg Cd L-1. The broad bean plant was resistant to growing in the contaminated area by Cd even at 120 mg Cd Kg-1 DW. The presence of heterotrophic bacteria was noticeably useful for autotrophic bacteria, as well as, for enhancing Cd resistance. The study showed that cooperative phytoremediation could be a safe and active technique to apply in the field soil contaminated with heavy metals.

Enhanced Cd Phytoextraction by Solanum nigrum L. from Contaminated Soils Combined with the Application of N Fertilizers and Double Harvests.

It is very important to increase phytoremediation efficiency in practice in suitable climatic conditions for plant growth through multiple harvests. Solanum nigrum L. is a Cd hyperaccumulator. In the present experiment, after applying different types of N fertilizers (NH4HCO3, NH4Cl, (NH4)2SO4, CH4N2O), root and shoot biomasses and Cd phytoextraction efficiency of S. nigrum effectively improved (p < 0.05). Shoot biomasses of S. nigrum harvested at the first florescence stage plus the amounts at the second florescence stage were higher than those harvested at the maturation stage, which indicates that S. nigrum Cd phytoaccumulation efficiency was higher in the former compared to the latter as there was no clear change in Cd concentration (p < 0.05). The pH value and extractable Cd contents showed no changes, regardless of whether N fertilizer was added or not at different growth stages. In addition, after N fertilizer was applied, H2O2 and malondialdehyde (MDA) contents in S. nigrum in vivo were lower compared to those that had not received N addition (CK); similarly, the concentration of proline was decreased as well (p < 0.05). The activity of the antioxidant enzyme catalase (CAT), harvested at different growth periods after four types of N fertilizer applications, obviously decreased in S. nigrum shoots, while peroxidase (POD) and superoxide dismutase) (SOD) activities increased (p < 0.05). Our study demonstrated that (NH4)2SO4 treatment exerted the most positive effect and CH4N2O the second most positive effect on S. nigrum Cd phytoremediation efficiency in double harvests at florescence stages, and the growth conditions were better than others.

Chronic Microplastic Exposure and Cadmium Accumulation in Blue Crabs.

Aquatic ecosystems are severely threatened by the presence of a multitude of pollutants. In seas and oceans, the amount of plastics continues to increase and there is great concern about toxic element accumulation. Specifically, cadmium (Cd), a toxic metal, is highly relevant to public health safety due to its ability to accumulate in the internal tissues of crustaceans; likewise, microplastics (MPs) are emerging as pollutants capable of causing alterations in marine organisms. The aim of this study was thus to evaluate the accumulation and distribution of Cd in the tissue of blue crabs (Callinectes sapidus) chronically exposed to MPs (25 μg L−1). In total, 24 crabs were exposed in water for 118 days to 2 types of MPs (virgin and oxidised). During the final 21 days of the experiment, the crabs were fed with tuna liver, a viscera in which Cd accumulates (mean of 7.262 µg g−1). The presence of MPs caused no changes in Cd concentrations in either the haemolymph or tissues (hepatopancreas, gills, and muscles) of the crabs, although for oxidised MPs, there was a positive correlation between Cd concentrations in the hepatopancreas and muscles, a relevant finding for food safety.

Changes in soil cadmium concentrations with time following cessation of phosphorus fertilizer inputs.

Cadmium (Cd) can accumulate in soil from the application of phosphorus fertilizer. However, there is little information on what happens to soil Cd concentrations when Cd inputs stop. This study used soil and pasture samples collected from a long-term field trial to measure changes in Cd concentrations in soil for 22 yr after Cd inputs from fertilizer had stopped and assessed whether the application of nitrogen (N) (50kg ha-1 yr-1 ) could increase plant uptake of Cd and reduce soil Cd concentrations. It was found that there was no significant change in total or labile soil Cd (1M CaCl2 extractable) concentrations after Cd inputs stopped. The application of N did not significantly (P<.05) increase dry matter yield or increase Cd solubility. As a result, N did not enhance plant uptake of Cd. A mass balance that included Cd loss via plant uptake and Cd leaching confirmed they were insufficient to result in a detectable decrease in soil Cd concentration over the 22-yr interval of the trial. It appears that even an acid soil with low amounts of carbon (2.67%), iron/aluminum oxides, and clay can still strongly retain Cd, preventing Cd depletion from the soil, despite stopping Cd inputs and trying to enhance plant uptake of Cd from the application of N fertilizer.

Influence of silicon on cadmium availability and cadmium uptake by rice in acid and alkaline paddy soils

The aim of this research was to study the inhibiting effects of cadmium uptake into plants by exogenous silicon between acid and alkaline paddy soils, especially, the effects of silicon without the differentiation of pH and accompanying ions. Therefore, without the interference of pH and accompany ions (Na+), the mechanisms of soil chemistry on cadmium (Cd) transformation and accumulation by Si application in the soil-plant system were examined. The acid and alkaline soils for the experiment were collected from the upper soil layer (0~20 cm) from two paddy fields. The Cd solution as CdNO3 and different levels of SiO2 as Na2SiO3 solutions were applied in the potted soils. To eliminate differences of nitrate and sodium among the treatments, 6.8, 6.8, and 1.7 g sodium nitrate was added into the CK, Si0Cd5, and Si90Cd5 treatments, respectively. The soil redox potential and pH during the experiments were determined. After harvest, changes in Cd concentrations in rice grains, stems, and roots were measured. Soil samples in close proximity to the rice roots were collected at harvest. The sequential extraction was employed to estimate the chemical speciation of Cd in the treated soils. The Si applications reduced Cd accumulation in rice plants, thereby increasing the rice yield. With increase of the dosages, the ratios of Cd contents in root, stem, and grain decreased significantly. The Eh and pH of the Si treatments were higher than application of Cd only. In the alkaline soil, Cd contents in the soil solutions of the Si treatments were higher than the Si0Cd5 treatment. In contrast, in the acid soil, the Cd contents in the soil solution of the Si treatments were lower than that Si0Cd5 treatment. In the acid soil, Si application improved the Cd adsorption by soil and alleviated Cd uptake by plants. Therefore, the alkaline soil reduced Cd phytoavailability by forming Si-Cd water-soluble complex, which could not be taken up by rice plants. The Si application significantly increased yield of rice and decreased Cd concentrations in the roots, stems, and grains of rice plants. In the alkaline soil, Cd and Si formed the Si-Cd water-soluble complex, which could not be taken up by the rice plants. In both soils, Si reduced the concentrations of acid extractable Cd and reducible Cd while promoting the formation of oxidable Cd and residual Cd, resulting in low soil Cd bioavailability.

Effect of elevated atmospheric CO2 concentration on growth and physiology of wheat and sorghum under cadmium stress

ABSTRACT Elevated concentrations of carbon dioxide (e[CO2]) affect plant growth and physiological characteristics, including metal accumulation, and the activity of anti-oxidant enzymes. These effects were investigated in cadmium (Cd) tolerant wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor (L.) Moench.) cultivars. Plants were grown at the ambient and elevated CO2 levels, with four concentrations of Cd (0, 10, 20 and 40 mg kg−1) added to the soil. After 60 days, subsamples were tested for chlorophylls and carotenoids, protein, enzyme activities and morphological characteristics. Results showed that e[CO2] increased plant height, leaf area, and the dry weight of shoots and roots (P < 0.01). In addition, it decreased the Cd concentration in the shoots and roots of wheat, and increased the same concentrations for sorghum. With increasing Cd, the activities of the anti-oxidants, SOD and GSH-px increased in wheat. The differences in enzyme activity parallel the changes in Cd concentration in the plants of both species.

Effects of Ammonium Chloride Fertilizer and its Application Stage on Cadmium Concentrations in Wheat (Triticum aestivum L.) Grain

Chloride (Cl) in saline soil increases the cadmium (Cd) concentration in crops. Here, we conducted a field experiment to investigate changes in Cd concentrations in wheat grain after the application of the Cl-containing fertilizer ammonium chloride (NH4Cl), with the aim of reducing its potential health risk. Effects of the application stage of NH4Cl fertilizer and leaching treatment (i.e., heavy rainfall) were also investigated in field and pot experiments. Both field and pot experiments showed that the Cd concentration of wheat grain was higher with NH4Cl fertilizer than with ammonium sulfate or urea fertilizers. Grain Cd concentration in wheat fertilized with NH4Cl at the tillering–jointing and flowering stages in the field experiment was 0.223 mg kg–1, which was about 1.5 times higher than that fertilized with urea. This finding is important because, in Japan, compound fertilizers containing NH4Cl are commonly used in fields for wheat cultivation. NH4Cl fertilizer application at the tillering–jointing and flowering stages had nearly equal effects on the Cd concentration in wheat grain. Basal dressing with NH4Cl fertilizer increased Cd concentrations in wheat grain to a greater extent than topdressing (at thetillering–jointing and flowering stage applications) in a pot experiment that was protected from rain. Leaching treatment (assuming two lots of 100 mm rainfall) negated the effect of NH4Cl fertilizer application on Cd concentration in wheat grain. We recommend the use of ammonium sulfate or urea preferentially as the nitrogen fertilizer because heavy rainfall rarely occurs during this period in Japan.

Placental transfer and concentrations of cadmium, mercury, lead, and selenium in mothers, newborns, and young children.

There is an emerging hypothesis that exposure to cadmium (Cd), mercury (Hg), lead (Pb), and selenium (Se) in utero and early childhood could have long-term health consequences. However, there are sparse data on early life exposures to these elements in US populations, particularly in urban minority samples. This study measured levels of Cd, Hg, Pb, and Se in 50 paired maternal, umbilical cord, and postnatal blood samples from the Boston Birth Cohort (BBC). Maternal exposure to Cd, Hg, Pb, and Se was 100% detectable in red blood cells (RBCs), and there was a high degree of maternal-fetal transfer of Hg, Pb, and Se. In particular, we found that Hg levels in cord RBCs were 1.5 times higher than those found in the mothers. This study also investigated changes in concentrations of Cd, Hg, Pb, and Se during the first few years of life. We found decreased levels of Hg and Se but elevated Pb levels in early childhood. Finally, this study investigated the association between metal burden and preterm birth and low birthweight. We found significantly higher levels of Hg in maternal and cord plasma and RBCs in preterm or low birthweight births, compared with term or normal birthweight births. In conclusion, this study showed that maternal exposure to these elements was widespread in the BBC, and maternal-fetal transfer was a major source of early life exposure to Hg, Pb, and Se. Our results also suggest that RBCs are better than plasma at reflecting the trans-placental transfer of Hg, Pb, and Se from the mother to the fetus. Our study findings remain to be confirmed in larger studies, and the implications for early screening and interventions of preconception and pregnant mothers and newborns warrant further investigation.

Combined toxicity of cadmium and lead on the earthworm Eisenia fetida (Annelida, Oligochaeta)

Cadmium (Cd) and lead (Pb) in soil have received extensive attention due to their potential toxicological effects. This study analyzed the combined toxicity of Cd and Pb on the earthworm Eisenia fetida. Cellulase activity and DNA damage were chosen as toxic endpoints. Factorial analysis was applied to identify the interaction of Cd and Pb. The results showed that single Pb and Cd could increase the cellulase activity and DNA damage of coelomocytes. The combination of both metals could significantly inhibit cellulase activity. For low Cd concentration, the addition of Pb could increase the DNA damage. However, for high Cd concentration, Pb could decrease the DNA damage. Factorial analysis showed that the changes of Cd concentrations exerted the highest influence on the combined toxicity, followed by factor “Cd⁎Pb” and “Pb”. The combined toxicological effects between Cd and Pb were complex, which might be influenced by the competition adsorption of both metals in soil and biomembrane and their bioavailability. The results of this study are useful for understanding of combined toxicity of Cd and Pb on terrestrial invertebrates.

Geostatistical analyses of heavy metal distribution in reclaimed mine land in Xuzhou, China

The aim of this study was to determine the ecological safety of reclaimed lands from subsided areas that had been filled with mining wastes and fly ash for agricultural purposes in the Liuxin mining area, Xuzhou, China. Both chemometric techniques and geostatistics were utilized to test the concentrations of As, Hg, Pb, Cu, Cd, Cr and Zn in reclaimed soils and in control soil at different depths. Results showed that, relative to local soil background values, the degree of variation in Hg, Cu, Cd and Pb at the majority of sampling points was large, especially for Cu in the control soil, Zn in the gangue site was also high, while As and Cr concentrations in the fly ash site and control soil were low. With reference to the China soil quality standard, besides Cd and a few samples of As, Zn and Cu, the other heavy metal concentrations were all lower than the standard. Based on this, the seriously high Cd levels were studied. To describe the regularity of the change in Cd concentration with depth, the polynomial fitting model was adopted and was found to be feasible. To achieve quantitative analysis from qualitative description, the Kriging interpolation model was applied to investigate the regular distribution of Cd. This model proved to have high precision at the fly ash site.

Cadmium Concentration and Metallothionein Expression in Prostate Cancer and Benign Prostatic Hyperplasia of Humans

Cadmium (Cd) causes various genitourinary disorders and is a carcinogen for prostate cancer. Metallothionein (MT) is a protein that detoxifies heavy metals. We evaluated changes in Cd concentration and MT expression in human prostate cancer (CaP) and benign prostatic hyperplasia (BPH). Our goal was to clarify the relationship between Cd concentration and MT expression in prostatic diseases. The experimental group consisted of 18 patients who underwent radical prostatectomy for CaP. The control group consisted of 35 patients who underwent transurethral resection of the prostate for BPH. Tissue samples were acquired from the gross tumor site and from resected chips. We determined Cd concentration by atomic absorption, MT expression by immunoblotting, and immunohistochemical staining. The significance of between-group differences for these outcomes was analyzed using Student's t tests. There was no statistically significant difference in Cd concentration between the CaP and BPH groups. Immunoblots from both groups revealed a single band. The relative intensity of the MT band was 0.58 +/- 0.09 in the BPH group and 0.17 +/- 0.03 in the CaP group. MT expression in patients with BPH was 3.4-fold higher than in those with CaP. MT may bind heavy metals and protect patients from CaP. Additional studies are needed to reveal the factors that influence the expression of MT in prostate epithelial cells, and to analyze the free and compound forms of Cd at the same time.

The Effects of Processing Methods and Storage on Cadmium Levels in Pacific Oysters (Crassostrea gigas)

ABSTRACT The effects of processing and storage on cadmium (Cd) levels in Pacific oysters (Crassostrea gigas) were examined. The oysters were 2.75 yrs old and were analyzed for Cd at various points in the processing line including: shucked (S), shucked and drained (SD), and shucked, drained, washed and jar-packed (S-WJ). The effects of high pressure processing (HPP) followed by washing and jar-packing were also examined. Jar-packed oysters from groups S-WJ and HPP were held under refrigerated storage and were analyzed at 0, 5 and 10 days. Some processing methods had significant effects on the Cd levels in oysters. Draining nectar from the oysters resulted in significant increases in Cd concentrations, followed by significant decreases as a result of washing and jar-packing. HPP-treated oysters that were washed and jar-packed showed further decreases in Cd. Ten days of jar-packed storage resulted in a gradual decrease in wet weight Cd concentration for both the HPP (from 1.1 to 0.8 mg/kg) and the S-WJ groups (from 1.4 to 0.9 mg/kg). Total tissue Cd levels decreased significantly during storage of oysters in Group S-WJ, while tissue weights increased significantly. These findings suggest that changes in Cd concentration may have been due to a combination of a release of Cd by the oyster tissue and a dilution of the available Cd due to water uptake.

Iron and copper accumulation in the brain of coxsackievirus-infected mice exposed to cadmium

Cadmium (Cd) is a potentially toxic metal widely distributed in the environment and known to cause adverse health effects in humans. During coxsackievirus infection, the concentrations of essential and nonessential trace elements (e.g., iron (Fe), copper (Cu), and Cd) change in different target organs of the infection. Fe and Cu are recognized cofactors in host defence reactions, and Fe is known to be associated with certain pathological conditions of the brain. However, whether nonessential trace elements could influence the balance of essential trace elements in the brain is unknown. In this study the brain Fe, Cu, and Cd contents were measured through inductively coupled plasma mass spectrometry and their distributions determined by nuclear microscopy in the early phase (day 3) of coxsackievirus B3 (CB3) infection in nonexposed and in Cd-exposed female Balb/c mice. In CB3 infection the brain is a well-known target that has not been studied with regard to trace element balance. The brain concentration of Cu compared with that of noninfected control mice was increased by 9% ( P < 0.05 ) in infected mice not exposed to Cd and by 10% (not significant) in infected Cd-exposed mice. A similar response was seen for Fe, which in infected Cd-exposed mice, compared to noninfected control mice, tended to increase by 16%. Cu showed an even tissue distribution, whereas Fe was distributed in focal deposits. Changes in Cd concentration in the brain of infected mice were less consistent but evenly distributed. Further studies are needed to define whether the accumulation and distribution of trace elements in the brain have an impact on brain function.

Relationship between shell weight and cadmium content in whole digestive gland of the Japanese scallop Patinopecten yessoensis (Jay)

Seasonal and age-specific variations of cadmium (Cd) concentration in the digestive gland were investigated in the Japanese scallop Patinopecten yessoensis from Peter the Great Bay, Sea of Japan, with different degrees of Cd pollution. The seasonal changes in Cd concentrations of the digestive gland were inversely proportional to the dry weight of the gland. Concentrations of Cd and total Cd content (mug Cd per organ) increased with age (age-specific) to the same extent in contaminated and uncontaminated areas. There was also a strong positive correlation between Cd content in the whole digestive gland and shell weight and it is proposed that this relationship can be used as a new criterion for comparative evaluation of Cd levels in scallops from different areas We hypothesize that Cd is uptaken into scallops in proportion to the amount of calcium that absorbed through ion channels, and in addition, Cd in the digestive gland is in immobile forms (e.g. metal-rich granules) that accumulate with age. Moderate environmental pollution has no effect on the relationship between Cd content and shell size and the observed decrease in growth performance of the scallops from polluted areas may be due to other factors.

Exchange rates of cadmium between a burrowing mayfly and its surroundings in nature

We conducted a reciprocal transfer of nymphs of the burrowing mayfly Hexagenia limbata between two rivers harboring populations of this insect that differed in their cadmium (Cd) concentrations. We measured Cd uptake and loss rates simultaneously in the field at several levels of biological organization: in the gut and body of whole nymphs as well as in three subcellular fractions. The most marked changes in Cd concentrations occurred in the insect's gut, where Cd was largely associated with heat-stable proteins, a fraction that includes the metal-binding protein metallothionein. Because most of the Cd that entered nymphs was detoxified in this manner, we would not expect it to have direct toxic effects; however, it would be readily transferred to higher trophic levels. Our data on subcellular partitioning suggest that there is a fast-exchanging pool of Cd bound to heat-stable proteins such as metallothionein and a slow-exchanging pool bound to either or both of the remaining fractions (heat-denatured proteins; remainder, which includes exoskeleton and granules). Nymphs of H. limbata responded rapidly to changes in bioavailable Cd, which suggests that they would be useful for monitoring changes in ambient Cd for weeks or months in the field. A one-compartment model successfully explained the changes we observed in nymph Cd values. Furthermore, values of the model constant for Cd loss were close to those reported for Hexagenia rigida in the laboratory, which suggests that accumulation patterns observed in the laboratory can be representative of those measured in nature.

Cadmium Bioavailability from Edible Sunflower Kernels: A Long-Term Study with Men and Women Volunteers

Sunflower kernels (SFK) contain natural Cd in somewhat higher amounts than most other foods. This study was designed to determine if a change in the body burden of Cd could be measured in volunteers who consumed a controlled amount of SFK for 48 weeks. Healthy men and women between 23 and 59 years of age were divided into three groups each by age, sex, and weight. For 48 weeks, one group consumed 255 g (9 oz) of SFK/week, a second group consumed 113 g SFK and 142 g peanuts/week, and a third group consumed 255 g peanuts/week. SFK contained 0.52 μg Cd/g and peanuts contained 0.11 μg Cd/g. The consumption of 255 g SFK/week increased the average estimated intake of Cd from ∼65 to ∼175 μg/week. Although the consumption of Cd-containing SFK significantly increased the estimated Cd intake, there were no significant changes in Cd concentration in red blood cells, Cd excretion in the urine, or Cd concentrations in new hair growth. However, fecal Cd excretion significantly increased as the amount of SFK consumption increased. N-Acetyl-β-D̄-glucosaminidase, a marker for kidney dysfunctions, was not significantly changed by consuming SFK-Cd. Overall, the results suggest that the consumption of Cd in the form of SFK at 9 oz (255 g)/week for 48 week had no adverse effect on the body burden of Cd.

Changes in cadmium concentrations in Antarctic ice and snow during the past 155,000 years

Changes in Cd concentrations in Antarctic ice and snow during the last full climatic cycle (the past 155,000 yrs) have been investigated by analysing various sections of the Dome C and Vostok deep Antarctic ice cores and several blocks of recent Antarctic snow. Each sample was mechanically decontaminated using ultraclean procedures and then analysed for Cd by the new ultrasensitive laser excited atomic fluorescence technique. Cd concentrations are found to have been highly variable in ancient Antarctic ice and therefore in the past pristine south polar atmosphere during the last climatic cycle, the highest values being observed during the cold terminal stages of the last and next to last ice ages. Concentrations measured in recent Antarctic snows are comparable with those in Antarctic Holocene ice several thousand years old, which suggests that the anthropogenic influence is probably still negligible for this heavy metal in the south polar atmosphere. For some of the samples, measured Cd concentrations can be simply accounted for by rock and soil dust and volcanic emissions, while for others there is a significant excess over the contributions from these two sources.