Pollutants in harp seals (Phoca groenlandica). II. Heavy metals and selenium

Between 1976 and 1978, 248 harp seals were sampled from five locations in the Northwest Atlantic and Arctic for heavy metal and selenium residue analyses in tissue. Significant loading was apparent only in blood, brain, kidney, liver and muscle. Samples were analysed for mercury (Hg), selenium (Se), copper (Cu), cadmium (Cd) and lead (Pb). The seals carried higher levels of Cd than of the other metals. Residue levels of Cd were highest in kidney tissue; levels of other metals were highest in liver. Both males and females bioaccumulated Cd, Hg and Se.Cd, Hg, Se and Cu residues were detected in tissue from neonatal seals, indicating that transplacental and transmammary transfer of these elements had occurred. Despite the passage of residues from mother to pup, females bore significantly higher levels of Hg and Cd than males. Conversely, levels of Cu, Se or Pb did not appear to differ significantly between sexes. There was considerable individual variation in residue levels. This, coupled with the extensive annual migration undergone by these animals, made it difficult to arrive at definite conclusions regarding geographic accumulation patterns.     

Toxic and essential trace metals in muscle, liver and kidney of bovines from a polluted area of Morocco

Toxic and essential trace metals were measured in muscle, bone, liver and kidney of bovine grazing on the municipal wastewater spreading field of Marrakech City (Morocco). Bovines were found to be seriously contaminated by toxic metals, for metal bioaccumulation. The high cadmium content seemed to contribute to a reduction in zinc and copper levels. The arithmetic mean concentrations of zinc, especially cadmium, and levels were higher in liver and kidney, specific target organs copper and cadmium in liver and kidney, were respectively: 126, 112 and 5.1 microg/g in liver; 89, 33 and 10.3 microg/g in kidney.     

Variation in cadmium content of caribou tissues from northern Québec

Samples of kidney, liver, skeletal muscle, heart, mesentery and rumen wall were collected during 1985-1986 in northern Québec from 121 caribou belonging to the Rivière George herd. Significant seasonal variations were found for cadmium concentration in kidneys, liver and skeletal muscles, the level being higher in winter than in autumn. The concentration in liver and kidneys increased with age, while the effect of this factor was complex in skeletal muscles. Sex-related differences were found in muscle and liver levels of cadmium. According to season, sex and age, mean dry-weight concentrations varied between 5.6 and 51.3 micrograms g-1 in kidneys, 1.7 and 4.0 micrograms g-1 in liver and 0 and 0.27 microgram g-1 in skeletal muscles. Season and sex-related differences could be explained by seasonal variation in cadmium intake and by the annual weight cycle exhibited by caribou kidneys and liver. Because of the relatively high cadmium content, it was recommended not to consume liver and kidneys of free-ranging caribou in Québec; this restriction did not apply to meat, heart, mesentery or rumen wall that contained limited concentrations of this heavy metal.     

The use of town refuse ash in urban agriculture around Jos, Nigeria: health and environmental risks

This paper reports on a study that examines the health and environmental risks of using town refuse ash in urban vegetable production in Jos, Nigeria, in terms of heavy metal accumulation in the food chain. Soil and crop samples, collected from five study farms, and samples of the river water used for irrigation, were analysed for seven heavy metals Fe, Mn, Zn, Cu, Ni, Cd and Pb. On the basis of the field data the paper discusses: (1) the potential soil deficiencies and toxicities; (2) the probable links between soil heavy metal levels and fertilisation practices; (3) the heavy metal concentrations in crop tissue in relation to crop growth and human health. The findings suggest that soil concentrations of the seven metals fall within 'typical' soil levels, and that there should not be any problems of either toxicities or deficiencies for crop growth. There was evidence of slight accumulation of Zn, Cu and Cd on some of the farms with a history of town refuse ash use. However, in all farms lettuce crops contained very large concentrations of Fe, and Pb concentrations that were 20 to 40 times higher than the WHO/FAO maximum recommended level in leafy vegetables for human consumption. The Cd content of carrot tissue was 10 times higher than the WHO/FAO recommended limit. The relatively small number of soil and crop samples precluded any formal attempt at correlating the concentrations of heavy metals found in the vegetable crops with the farm levels. Nevertheless, the data suggested that these were not linked. The paper goes on to consider various potential sources of the metals found in the crops, including irrigation water, town refuse ash and air-borne dust, and discusses additional health and environmental risks pertaining to the use of town refuse ash. Undoubtedly, the heavy Pb and Cd contamination of certain crops indicates the urgent need for future studies to ascertain the precise source of these metals, and although the practice of using town refuse ash does not appear to have resulted in large-scale contamination of soil in the farming area, there are a number of unsafe practices associated with it that call for the identification of strategies for the safe utilisation of urban waste in Jos.     

Distribution of Cd, Zn, Cu and Fe among selected tissues of the earthworm (Allolobophora caliginosa) and Eurasian woodcock (Scolopax rusticola)

We have measured the concentrations of heavy metals in soils, earthworms and tissues of woodcocks in Quaderna Valley, northern Italy. The soil concentration of metals analysed in this research is consistent with data reported by other authors for uncontaminated or slightly contaminated soils. In earthworms, metals were mostly accumulated in the encapsulating chloragogenous tissue; the positive correlation between Cu concentration in the soil and in earthworms is noteworthy. Heavy metal distribution in the tissues of woodcock showed that Cd accumulation in the kidney was linked to the diet. Cu and Fe were preferentially concentrated in the liver and Zn in the testis. Kidney Cd and Zn concentrations were higher in adults than in juveniles. In addition, a main kidney metallothionein isoform, containing Cd and Zn, was isolated. In the kidney, Cd levels were linearly correlated with the concentration of metallothionein. Of the investigated metals, Cd raises the greatest concern, due to the increasing soil contamination by human activities.     

Heavy metals in tissues of stranded short-finned pilot whales.

Selected tissues from four short-finned pilot whales that stranded at Cumberland Island National Seashore were analyzed for total cadmium, mercury and selenium by neutron activation. Cadmium reached a maximum mean wet weight concentration of 31.4 ppm in the kidney tissues. Maximum mean wet weight concentrations of mercury, 230.0 ppm, and selenium, 44.2 ppm, were found in the liver tissues. The lowest concentration of each metal was found in the blubber. Postmortem examination showed that the whales had no food in their stomachs. The whales must have been utilizing metabolic reserves, contaminated with residual concentrations of heavy metals, prior to beaching. This utilization of reserves probably resulted in the high concentrations of cadmium, mercury and selenium found in the liver and kidney tissues. Since the heavy metal concentrations were three to four times greater in the stranded whales, as compared to apparently healthy whales of the same species, it is suggested that heavy metal toxicosis may have been a factor contributing to this particular stranding.     

Testing the validity of a Cd soil quality standard in representative Mediterranean agricultural soils under an accumulator crop

The validity of a quality standard for cadmium (Cd) in representative agricultural Mediterranean soils under an accumulator crop (Lactuca sativa L.) is evaluated in this work considering both its effect on the crop growth (biomass production) and the metal accumulation in the edible part of the plant. Four soils with different properties relevant to regulate the behaviour of heavy metals were selected from the Valencian Region, a representative area of the European Mediterranean Region. For all soils, the effective concentration of added Cd causing 50% inhibition (EC₅₀) on the biomass production was much higher than the minimum legal concentration used to declare soils as contaminated by cadmium, i.e. 100 times the baseline value for Cd, in Spain (Spanish Royal Decree 9/2005). As expected, Cd toxicity in the crop was higher in the soils having less carbonate content. On the other hand, for all soils, from the second dose on, which represents 10-times the baseline value for Cd, the metal content in crops exceeded the maximum level established for leaf crops by the European legislation (Regulation EC no. 466/2001). Soil salinity and coarse textures make the accumulation of Cd in the edible part of the plant easier. Therefore, the legal baseline soil cadmium content established by the Spanish legislation seems not valid neither from the point of view of the effect on the crop growth nor from the point of view of the metal accumulation in the edible part of the plant. In order to realistically declare contaminated soils by heavy metals, soil quality standards should be proposed taking into account the soil properties. Further research in other agricultural areas of the region would improve the basis for proposing adequate soil quality standards for heavy metals as highlighted by the European Thematic Strategy for Soil Protection.     

Accumulation of heavy metals in circumpolar willow ptarmigan (Lagopus l. lagopus) populations

A circumpolar survey of heavy metals in willow ptarmigan liver and kidney revealed considerable variations in Cd content in Canada and Scandinavia. The Cd content in central Canada was comparable with that in Scandinavia and Russia, at least for kidney. However, in both liver and kidney the median for Canada as a whole was much higher than in the other countries. Some Canadian locations had exceptionally high levels, several birds having >50 mg kg(-1) in liver and >400 mg kg(-1) in kidney. In Norway, the Cd content was highest in central mountain areas in south Norway and inland locations in the two northernmost counties. Five locations in central and north Norway showed mean Cd levels in kidney above 100 mg kg(-1). It is difficult to evaluate regional differences in Sweden, but most locations had the same Cd level as moderately contaminated locations in Norway. Cd levels in Russia were comparable to moderately contaminated locations in the other countries. Due to a high intake of willow, naturally rich in Cd, direct comparison of the Cd level in willow ptarmigan from different locations cannot reveal the effects of long-range pollution. The Pb concentration in willow ptarmigan kidney and liver varied significantly in Norway and Canada, but not in Sweden and Russia. Levels in Sweden and Russia were comparable to those in Canada and low levels in Norway. The highest median value from all locations within countries was found in Norway, both in liver and kidney. The highest Pb content was found in south Norway, indicating an effect of long-range pollution in willow ptarmigan. The level in western Canada was significantly higher than in central Canada. The Hg content in liver varied significantly from one location to another in all the countries and in kidney everywhere except Sweden. In Scandinavia, there is no distinct regional pattern. Canada had a significantly higher Hg level in central than western regions in both tissues the opposite of that found for Cd and Pb. Cu and Zn showed significant variations from one location to another in liver and kidney in Canada and Norway, but only in kidney in samples from Sweden. Comparison between western and central Canada revealed a significant difference for Cu in liver, samples from central Canada having more. There are no significant differences from one country to another, but some localities in Canada seem to have higher Cu concentrations in kidney than are found in Scandinavia and Russia.     

A field survey of metal binding to metallothionein and other cytosolic ligands in liver of eels using an on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS)

The effect of metal exposure on the accumulation and cytosolic speciation of metals in livers of wild populations of European eel with special emphasis on metallothioneins (MT) was studied. Four sampling sites in Flanders showing different degrees of heavy metal contamination were selected for this purpose. An on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS) was used to study the cytosolic speciation of the metals. The distribution of the metals Cd, Cu, Ni, Pb and Zn among cytosolic fractions displayed strong differences. The cytosolic concentration of Cd, Ni and Pb increased proportionally with the total liver levels. However, the cytosolic concentrations of Cu and Zn only increased above a certain liver tissue threshold level. Cd, Cu and Zn, but not Pb and Ni, were largely associated with the MT pool in correspondence with the environmental exposure and liver tissue concentrations. Most of the Pb and Ni and a considerable fraction of Cu and Zn, but not Cd, were associated to High Molecular Weight (HMW) fractions. The relative importance of the Cu and Zn in the HMW fraction decreased with increasing contamination levels while the MT pool became progressively more important. The close relationship between the cytosolic metal load and the total MT levels or the metals bound on the MT pool indicates that the metals, rather than other stress factors, are the major factor determining MT induction.     

Cadmium biosorption by free and immobilised microorganisms cultivated in a liquid soil extract medium: effects of Cd,pH and techniques of culture

Instead of soil clean-up, a process not very technically and economically suited to agricultural soil contaminated by heavy metals (with a low concentration of heavy metals but highly or potentially highly contaminated surfaces), the control of the transfer of cadmium from the soil to the crops may well be a convenient method. We tested the bacterium ZAN-044, the actinomycete R27 and a basidiomycete Fomitopsis pinicola isolated for their ability to biosorb Cd, in order to inoculate agricultural soils afterwards. We then compared the cadmium biosorption by viable microbial cells which were free or immobilised in alginate beads and incubated in a soil extract liquid medium at various pH values (5, 6 and 7) and cadmium concentrations (1 and 10 mg/l). The Cd concentration in the medium had the most important effect on the percentage of Cd biosorbed by the microorganisms, but the culture mode (free or immobilised cells) was not a side effect. In the case of F. pinicola and the actinomycete R27, the percentage of Cd biosorbed by free cells did not decrease when the Cd concentration in the medium increased (6-42% at the lowest Cd concentration to 11-48% at 10 mg Cd/l). On the other hand, with a low Cd concentration (1 mg Cd/l), the percentage of Cd biosorbed by the bacterium ZAN-044 was maximum (69%) at pH 7, while this bacterium did not grow at 10 mg Cd/l and it did not accumulate Cd. For the three micro-organisms tested, relatively low specific biosorptions of Cd were observed, when the microorganisms were cultivated with a soil extract medium ('poor' medium), comparatively to those with a 'rich' medium. Finally, the choice of microorganism for the inoculation of contaminated soils depends on the cadmium level in the medium and on the distribution of the metal between the biomass and the medium.     

Cadmium and lead in selected tissues of two commercially important fish species from the Adriatic Sea

Baseline levels of cadmium and lead were determined in muscle tissue and liver of hake (Merluccius merluccius) and red mullet (Mullus barbatus), two commercially important fish species from the eastern Adriatic. Concentrations of trace metals in liver (Cd: 6–183 μg kg⁻¹ w. wt. ; Pb: 39–970 μg kg⁻¹ w. wt.) were within the range of recently published data for the Mediterranean. In the muscle tissue, cadmium concentrations (4.1–29 μg kg⁻¹ w. wt.) were among the lowest reported values for the Mediterranean, whereas lead levels (49–158 μg kg⁻¹ w. wt.) were within the range of values reported for various coastal areas of the Mediterranean. Presented data on cadmium and lead content in the studied fish species provide no proof of the general pollution of the Adriatic. Obtained data were tested in relation to fish length. Metal concentrations in liver decreased with the increase in fish size, whereas no significant correlation was found between trace metal levels in the muscle tissue and the length of both species. Relationships between metal concentrations and sex were also tested, but they gave no significant results. A comparison of contaminant concentrations in the edible tissue of hake and red mullet with the Croatian legislation shows that the consumption of their meat is not harmful for humans, not even for the most endangered population from the coastal region.     

Metal levels in blood, muscle and liver of water snakes (Nerodia spp.) from New Jersey, Tennessee and South Carolina

Reptiles, particularly snakes, could serve as bioindicators of contamination because some are comparatively long-lived, exhibit different trophic levels, and are at the top of their food chains. We test the null hypothesis that there are no differences in the concentrations of heavy metals in the blood, muscle and liver of water snakes (Nerodia spp.) from rivers in New Jersey, Tennessee and South Carolina. While the former site is in an urban/suburban area, the latter two sites are relatively rural and are located on Department of Energy sites. For the snakes from New Jersey, there were significant differences in metal concentrations among tissues for all metals, the highest levels for arsenic and selenium were in liver and kidney, for cadmium were in the liver, for chromium and lead were in skin, and for mercury and manganese were in the muscle. Body length was not correlated with metal levels, and there were more significant correlations for skin with internal tissues than for blood with other tissues. There were more significant correlations for mercury than for other metals. In comparing metal levels among states, levels were generally higher for snakes collected from South Carolina. These data indicate that, since water snakes accumulate contaminants differentially as a function of location, they can be useful bioindicators of environmental exposure to contaminants. Moreover, because of their wide geographical distribution and use of varying trophic compartments, this genus can be useful for cross-site comparisons.     

Monitoring for Pb and Cd pollution using feral pigeons in rural, urban, and industrial environments of Korea

This study was aimed at evaluating the lead (Pb) and cadmium (Cd) contamination status using resident pigeons from rural (island), central urban (Seoul), and four industrial complex areas in Korea with varying traffic density as well as atmospheric metal pollution records. We also discussed the results with respect to metal exposure trends in urban area after introduction of lead-free gasoline in Korea. Mean concentrations of Pb and Cd in bone and kidney of pigeons from Seoul were comparable to those from industrial complex areas and were about 15-20 times those at the reference site. This suggests that exposure to metals in the urban environment is as high as in the industrial areas. Lead and Cd concentrations in lungs of pigeons from Seoul were significantly higher by more than three times in 2000 than in 1991 (p < 0.01), whereas the residues in liver, kidney, and bone remained at a similar level, despite the introduction of unleaded gasoline in 1993. The Pb and Cd concentrations in tissues of pigeons did not decrease as atmospheric metal levels decreased. Ingestion may be more important than inhalation in exposing pigeons to Pb and Cd in this study.     

The behaviour of pharmaceuticals and heavy metals during struvite precipitation in urine

Separating urine from wastewater at the source reduces the costs of extensive wastewater treatment. Recovering the nutrients from urine and reusing them for agricultural purposes adds resource saving to the benefits. Phosphate can be recovered in the form of struvite (magnesium ammonium phosphate). In this paper, the behaviour of pharmaceuticals and heavy metals during the precipitation of struvite in urine is studied.When precipitating struvite in urine spiked with hormones and non-ionic, acidic and basic pharmaceuticals, the hormones and pharmaceuticals remain in solution for more than 98%.For heavy metals, initial experiments were performed to study metal solubility in urine. Solubility is shown to be affected by the chemical conditions of stored and therefore hydrolysed urine. Thermodynamic modelling reveals low or very low equilibrium solute concentrations for cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb). Experiments confirmed Cd, Cu and Pb carbonate and hydroxide precipitation upon metal addition in stored urine with a reaction half-life of ca. 7 days.For all metals considered, the maximum specific metal concentrations per gram phosphate or nitrogen showed to be typically several orders of magnitudes lower in urine than in commercially available fertilizers and manure. Heavy metals in struvite precipitated from normal stored urine could not be detected.Phosphate recovery from urine over struvite precipitation is shown to render a product free from most organic micropollutants and containing only a fraction of the already low amounts of heavy metals in urine.     

Trophic relationships in an Arctic food web and implications for trace metal transfer

Tissues of subsistence-harvested Arctic mammals were analyzed for silver (Ag), cadmium (Cd), and total mercury (THg). Muscle (or total body homogenates of potential fish and invertebrate prey) was analyzed for stable carbon (delta13C) and nitrogen (delta15N) isotopes to establish trophic interactions within the Arctic food chain. Food web magnification factors (FWMFs) and biomagnification factors for selected predator-prey scenarios (BMFs) were calculated to describe pathways of heavy metals in the Alaskan Arctic. FWMFs in this study indicate that magnification of selected heavy metals in the Arctic food web is not significant. Biomagnification of Cd occurs mainly in kidneys; calculated BMFs are higher for hepatic THg than renal THg for all predator-prey scenarios with the exception of polar bears (Ursus maritimus). In bears, the accumulation of renal THg is approximately 6 times higher than in liver. Magnification of hepatic Ag is minimal for all selected predator-prey scenarios. Though polar bears occupy a higher trophic level than belugas (Delphinapterus leucas), based on delta15N, the metal concentrations are either not statistically different between the two species or lower for bears. Similarly, concentrations of renal and hepatic Cd are significantly lower or not statistically different in polar bears compared to ringed (Phoca hispida) and bearded seals (Erignathus barbatus), their primary prey. THg, on the other hand, increased significantly from seal to polar bear tissues. Mean delta15N was lowest in muscle of Arctic fox (Alopex lagopus) and foxes also show the lowest levels of Hg, Cd and Ag in liver and kidney compared to the other species analyzed. These values are in good agreement with a diet dominated by terrestrial prey. Metal deposition in animal tissues is strongly dependent on biological factors such as diet, age, sex, body condition and health, and caution should be taken when interpreting magnification of dynamic and actively regulated trace metals.     

兰州某铝厂旧址周围土壤重金属污染及分布特征

研究了兰州某铝厂旧址周围土壤重金属形态特征,找出了该土壤中重金属元素的形态分布及变化规律,分析了引起7种重金属元素形态变化的主要因子。结果表明,该铝厂周围土壤重金属Cu、Mn、Ni、Pb、Zn、Cr、Cd污染严重。各重金属元素的含量随样品采集半径的增加而减少,7种重金属的形态分析结果表明,重金属污染主要以残渣态为主,Cd、Mn和Cr的弱酸态占有较大的比例,其中Cd的生态风险性最高。同时对重金属的环境效应和生态风险作出一定的评价,为治理和改善该地区土壤环境质量积累科学数据。     

Reproductive cycle and heavy metals in the organs of red mullet, Mullus barbatus (L.), from the northwestern Mediterranean.

Concentrations of the heavy metals Cd, Cu, Fe Mn, V and Zn have been measured in the principal tissues of the red mullet, Mullus barbatus (L.), during a complete sexual cycle. By comparison of metal levels during the reproductive and non-reproductive periods, it was found that concentrations as well as total amounts of Cu, Mn and Zn in liver and gonads of male and female mullets were dependent upon the stage of the sexual cycle. No relationship with the sexual cycle was noted for these metals measured in muscle, kidney, spleen or pyloric caecum. Because of the observed variation in liver and gonad metal concentrations, these tissues appear to be poor indicators of ambient levels of metals in the surrounding waters. However, muscle may prove useful as an indicator tissue owing to its apparent independence of effects of the sexual cycle.     

A dynamic model to calculate cadmium concentrations in bovine tissues from basic soil characteristics

A chain model was developed to calculate the flow of cadmium from soil, drinking water and feed towards bovine tissues. The data used for model development were tissue Cd concentrations of 57 bovines and Cd concentrations in soil, feed and drinking water, sampled at the farms were the bovines were reared. Validation of the model occurred with a second set of measured tissue Cd concentrations of 93 bovines of which age and farm location were known. The exposure part of the chain model consists of two parts: (1) a soil-plant transfer model, deriving cadmium concentrations in feed from basic soil characteristics (pH and organic matter content) and soil Cd concentrations, and (2) bovine intake calculations, based on typical feed and water consumption patterns for cattle and Cd concentrations in feed and drinking water. The output of the exposure model is an animal-specific average daily Cd intake, which is then taken forward to a kinetic uptake model in which time-dependent Cd concentrations in bovine tissues are calculated. The chain model was able to account for 65%, 42% and 32% of the variation in observed kidney, liver and meat Cd concentrations in the validation study.     

Heavy metal contents in horticultural crops of a representative area of the European Mediterranean region

Heavy metal content (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) was analysed in the edible parts of two types of horticultural crops (leaf and inflorescence crops) from 30 agricultural fields in Castellón (Spain), a representative area of the European Mediterranean region. Selected soil properties relevant to control the mobility and bioavaibility of heavy metals were analysed for the general characterisation of these agricultural soils. The levels of clay, high percentages of organic matter and the presence of carbonate seem to suggest an important retention of heavy metals by these components in most of these soils. However, the high salinity in some fields (>4 dS/m) seems to facilitate the mobility of some heavy metals (e.g. Cu). The mean values of total contents of heavy metals in soils were similar to values obtained in other works on Spanish agricultural soils. However, there were some fields with a metal content (particularly Cu, Pb or Zn) higher than these works, reflecting an important anthropogenic source. In seven fields, the crop contents of Cd and/or Pb were higher than the maximum levels established by the Commission Regulation no. 466/2001 for horticultural crops. Heavy metal contents in leaf crops were higher than in inflorescence crops, except for Zn. The differences for Cd, Cr, Cu, Fe and Mn contents between these two types of crops were statistically significant. The analysis of crop heavy metal contents showed a higher absorption and/or accumulation of heavy metals in leaf crops than in inflorescence crops. Differences in crop characteristics seem to be responsible for the differential accumulation of heavy metals. Furthermore, agronomic practices and other sources of heavy metals (e.g. atmospheric deposition for Cd and Pb) may also have some influence on crop accumulation. Given the relevance of horticultural crops in the Mediterranean diet, it is highly necessary to extend the experience of this work to other areas of the European Mediterranean region.     

Review of toxicity test results submitted in support of pesticide tolerance petitions.

A long term-low level exposure (LLE) experiment was conducted on rats to determine the metabolic patterns for realistic environmental dietary levels of cadmium. Male rats fed with 61 ppb of cadmium ad libitum, 50 labelled with ¹⁰⁹Cd radiotracer as cadmium chloride via drinking mineral water and 11 unlabelled via food for 2 years. The diet was characterized in its metal content by neutron activation analysis to obtain the total dietary intake of different elements.The kidney was found to be the tissue with the major concentration of cadmium which accumulated continuously during the experiment.The variation of the accumulation pattern of Cd concentration in the liver and intestine indicated an initial rapid increase of Cd during the first 100 days. After this period an apparent equilibrium was attained in both these tissues until the end of the study.The intracellular distribution of cadmium in kidneys, liver, intestine and pancreas were similar, the cytosol fractions containing about 80% of the cellular cadmium. Dialysis experiments indicated that significant amounts of cadmium were able to be associated with cellular organelles, the mitochondria representing the most important organelle capable of binding cadmium.The cytoplasmatic Cd-profiles obtained at various stages of the experiment showed that the metal was only bound to a low-molecular-weight component, cadmium-binding protein (CdBP), which represents the specific cellular-binding component for cadmium under the long term-low level exposure (LLE) conditions.No significant variations in the concentrations of the elements in different organs were observed in animals supplemented with ¹⁰⁹Cd in respect to ¹⁰⁹Cd untreated controls.