Is human hair a dosimeter for endogenous zinc and other trace elements?

This work incorporates an assessment of the potential of human hair to monitor ingestion of trace elements from the environment. Included is a report of a study of Zn levels in the facial hair of one of the authors, who was dosed with ZnSO₄. Daily doses increasing from 100 to 300 mg Zn were taken for 57 days. Analysis was by differential pulse anodic stripping voltammetry. No significant increase in beard Zn was found. Cd, Pb and Cu were measured simultaneously.Studies of dosing with other elements are reviewed and a generalized pool model for the deposition of ingested trace elements in hair is presented.It is suggested that the concept of hair as a monitor of endogenous elements is a simplistic one which is better modified by the pool model, the precise form of which varies with the element under consideration.     

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.     

Modeling metal bioaccumulation in a deposit-feeding polychaete from labile sediment fractions and from pore water

Estuarine sediments are often highly enriched in particle-reactive metal contaminants and because aquatic animals have often been shown to acquire metals predominantly from their diet, benthic animals feeding on deposited or resuspended sediments may also accumulate metals through this uptake pathway. Laboratory experiments were performed in which the surface deposit-feeding polychaete, Nereis succinea, was exposed to As(+ 5), Cd, and Cr(+ 3) in pore water or in estuarine sediments with and without enrichment with algal debris. These experiments generated metal uptake parameters (assimilation efficiency of ingested metal [AE], uptake rate constant of dissolved metal, efflux rate constants following dietary or aqueous metal exposures) used in a kinetic model of metal bioaccumulation. The model showed that > 97% of the body burden of these metals is accumulated through ingested sediment. The kinetic model was further modified to consider the geochemical fractionation of the metals in the sediments because metals bound to some fractions were shown to be unavailable to these polychaetes. The modified model substituted the AE term for each metal by the percentage of metal extracted in neutral and weak acid exchangeable fractions (termed “carbonex” fraction) multiplied by the slope of the regression between the metal AE and its fractionation in carbonex. The modified model generated predictions of As, Cd, and Cr body burdens in polychaetes at three different estuarine sites that matched independent field observations at these sites (r² = 0.84 for sediments without organic enrichment, r² = 0.87 with organic enrichment). Model predictions that relied on total metal concentrations showed weaker relationships (r² = 0.11-0.50). This study adds to the evidence for the dominance of dietary uptake of metals in aquatic animals and identifies a key sedimentary fraction of metals that can account for bioavailability of sediment-bound metals.     

Mammalian hair as an accumulative bioindicator of metal bioavailability in Australian terrestrial environments

The current study represents the first investigation of the suitability of marsupial and eutherian mammalian hair as indicator tissue for metal exposure and accumulation within contaminated Australian terrestrial ecosystems. A soil metal contamination gradient was established across 22 sites at increasing distances from a decommissioned Lead/Zinc smelter in NSW, Australia. Within each site, soil and small mammal populations were sampled. An Australian native marsupial, the insectivorous Brown Antechinus, Antechinus stuartii: Dasyuridae, and introduced rodents, the omnivorous Brown or Norway Rat, Rattus norvegicus: Muridae and the Black Rat, Rattus rattus: Muridae were assessed for hair concentrations of Cadmium (Cd), Copper (Cu), Lead (Pb) and Zinc (Zn). Metals in soil were most elevated at sites within close proximity to the smelter, with soil metal concentrations decreasing with distance from the smelter. The non-essential metals Pb and Cd were accumulated in hair, both metals exhibiting positive linear relationships with environmental exposure (soil metal concentrations). When the variables of weight and snout-vent length were considered, no further contribution in terms of explaining the variability in hair Cd or Pb was observed for all species examined. The essential metals Cu and Zn were regulated in hair, remaining similar across the metal contamination gradient. A significant negative correlation between snout-vent length and hair Cu concentration was found for the Brown Rat; greater hair Cu concentrations were found in smaller individuals of this species. Accumulation of Pb to hair was similar among species while concentrations of Cd in Brown Rat hair were higher than both Black Rat and Brown Antechinus hair. As each of the three aforementioned species exhibit similar bioaccumulation relationships for Pb, we suggest that sampling hair from introduced rodents (pest species) may provide a suitable proxy for the assessment of Pb bioavailability for a range of small mammals within Australian urban remnants.     

Lead poisoning combined with cadmium in sheep and horses in the vicinity of non-ferrous metal smelters

The diagnosis of lead poisoning combined with cadmium in sheep and horses living on farmland in the vicinity of non-ferrous metal smelters in Baiyin of Gansu province in China was based on laboratory findings as well as clinical signs. The concentrations of lead, cadmium, copper and zinc in soils, water, forages, feed and blood, hair and tissues of affected sheep and horses were determined in the surroundings of the smelters in Baiyin and controls. Haematological values were also measured. The concentrations of these elements in soils, forages, water and feed were significantly higher than those in the control area (P<0.01). The contents of lead and cadmium were 9.3 and 690 times in forages, respectively, 10 and 35.6 times in feed. The concentrations of lead and cadmium in blood, hair and tissues of the affected sheep and horses were significantly higher than reference values and control animals (P<0.01). The occurrence of anaemia in affected animals belonged to a hypochromic and microcytic pattern. Lead and cadmium intake levels, estimated according to the ingestion rates of forages, illustrates that the apported lead and cadmium through the ingestion of vegetation growing in the closest sites to the smelters were approximately 6.0 mg Pb/kg body wt./day and 1.1 mg Cd/kg body wt./day in horses, 21.4 mg Pb/kg body wt./day and 4.0 mg Cd/kg body wt./day in sheep, surpassing the fatal dosages for horses of 1.7 mg Pb/kg body wt./day and for sheep of 4.4 mg Pb/kg body wt./day and 1.0 mg Cd/kg body wt./day. It is, therefore, suggested that the disease of sheep and horses in this region is caused by lead poisoning combined with cadmium, mainly due to environment heavy metal pollution by industrial activity. Meanwhile, as such levels of contamination in animal food and grain pose a significant potential risk to human health, these results have formed the basis for subsequent research on levels of metal contamination in human tissues from affected populations. Thus, it can be seen that knowledge of lead and cadmium concentrations in livestock in this region is important for assessing the effects of pollutants on domestic animals themselves and contaminant intakes by humans.     

Cadmium content of indicator and target organs in rats after graded doses of cadmium

Eleven groups of inbred Wistar rats, five males and five females in each group, received graded doses of CdCl₂, from 0–25 ppm, in the drinking water from conception until sacrifice at ten weeks of age. Litter‐size, weight and water consumption were recorded at different ages of the animals. The Cd levels of indicators as blood, hair, incisors and molars, and target organs as femur, kidney cortex, liver, spleen, heart, gastrocnemius muscle and adrenal glands were recorded by atomic absorption spectrophotometry. Cd in the drinking water had no influence on number of animals in each litter, water consumption and growth of the animals. The results further confirmed that the primary target organs of Cd were the soft tissues, but that Cd can to some degree accumulate in teeth and bone, especially molars. The Cd content of all tissues, both indicators and targets, was positively and significantly correlated with dose. The positive significant correlation between the Cd levels of hair or molars, and every target organ suggests that hair and molars of rats are very useful indicators of a Cd exposure in progress. It is supposed that rodent molars are comparable to human deciduous teeth. It is thus suggested that human deciduous teeth and human hair can be used as an indicator of a Cd exposure in progress.     

Health risk assessment of heavy metal exposure to street dust in the zinc smelting district, Northeast of China

Heavy metal contamination in the street dust due to metal smelting in the industrial district of Huludao city was investigated. Spatial distribution of Hg, Pb, Cd, Zn and Cu in the street dust was elucidated. Meanwhile, noncancer effect and cancer effect of children and adults due to exposure to the street dust were estimated. The maximum Hg, Pb, Cd, Zn and Cu contents in the street dust are 5.212, 3903, 726.2, 79,869, and 1532 mg kg^− 1, and respectively 141, 181, 6724, 1257 and 77.4 times as high as the background values in soil. The trends for Hg, Pb, Cd, Zn and Cu are similar with higher concentrations trending Huludao zinc plant (HZP). The exponential equation fits quite well for the variations of Pb, Cd, Zn and Cu contents with distance from the pollution sources, but not for Hg. The biggest contribution to street dust is atmospheric deposition due to metal smelting, but traffic density makes slight contribution to heavy metal contamination. According to the calculation on Hazard Index (HI), in the case of noncancer effect, the ingestion of dust particles of children and adults in Huludao city appears to be the route of exposure to street dust that results in a higher risk for heavy metals, followed by dermal contact. The inhalation of resuspended particles through the mouth and nose is almost negligible. The inhalation of Hg vapour as the fourth exposure pathway to street dust is accounting for the main exposure. Children are experiencing the potential health risk due to HI for Pb larger than safe level (1) and Cd close to 1. Besides, cancer risk of Cd due to inhalation exposure is low.     

The significance of atmospheric deposition of heavy metals in four Danish lakes

The atmospheric deposition rate of heavy metals was determined throughout a seventeen month period at four lakes and a control station across Mid-Jutland, Denmark, and its significance was assessed in relation to the concentrations of Zn, Cu, Pb, and Cd in water, sediment and aquatic macrophytes (Phragmites australis (Cav.) Trin, Littorella uniflora (L.) Ashers., Isoetes lacustris L. and Juncus bulbosus L.) from Lake Hampen, Lake Meldgaard, Lake Sortesø, and Lake Gødstrup. Mean annual deposition rates of 1.81–2.77 mg Cu m^?2, 4.09–8.73 mg Pb m^?2, and 0.21–0.37 mg Cd m^?2 were determined. For Zn a mean deposition rate of 15 mg Zn m^?2 year^?1 was used (Hovmand, 1979). The atmospheric deposition per m² of Zn and Cu amounts to 0.2–37%, 0.05–4.3% and 3.4–107% of the contents present in the water column of the lakes, the upper 10 cm of the littoral sediment and in dense vegetation of aquatic macrophytes, respectively. Equivalent figures for Pb and Cd are 1.8–649%, 0.8–30.6%, and 16.8–951%. In the profundal sediments of the oligotrophic Lake Hampen, post-war atmospheric deposition has increased the heavy metal concentration and content up to 180 times. The Pb concentrations in sediments from different depths were significantly correlated with the post-war consumption of gasoline in Denmark. It is concluded that atmospheric deposition of heavy metals results in a significant contamination of lakes, especially oligotrophic lakes for which aerial fallout is the major source. It is further concluded that lake sediments uncontaminated with heavy metals are probably no longer found in Denmark.     

Interspecific comparison of cadmium and zinc contamination in the organs of four fish species along a polymetallic pollution gradient (Lot River, France)

The impact of cadmium (Cd) and zinc (Zn) discharges related to an old zinc ore treatment facility in the Lot River (France) was investigated in four fish species (the chub: Leusciscus cephalus, the roach: Rutilus rutilus, the perch: Perca fluviatilis and the bream: Abramis brama). The organisms were sampled in four stations along the polymetallic contamination gradient. Cd and Zn analysis were carried out in five organs (gills, posterior intestine, liver, kidneys and skeletal muscle) in order to highlight the potential pathways of uptake, storage and elimination of metals. The results indicate a very strong Cd contamination in fish collected downstream from the metal source. The kidneys have the highest cadmium concentrations, but the gills and the intestine, as exchange organs, present the largest variations between the stations in close relation with the contamination gradient. Cd concentrations measured in the liver vary only slightly among the sampling stations. Unlike the trends observed for Cd, Zn levels in fish populations are strongly regulated and do not follow ambient Zn concentrations. The concentrations measured vary also according to fish species, for both Cd and Zn. This study shows that the trophic habits can explain the interspecific differences in Cd bioaccumulation. Zn levels observed for each species in non-contaminated populations also help to understand metal bioaccumulation patterns in polluted sites, suggesting that the determinism of interspecific differences is constitutive.     

Health risk from heavy metals via consumption of food crops in the vicinity of Dabaoshan mine, South China

Heavy metal contamination of soils resulting from mining and smelting is causing major concern due to the potential risk involved. This study was designed to investigate the heavy metal (Cu, Zn, Pb and Cd) concentrations in soils and food crops and estimate the potential health risks of metals to humans via consumption of polluted food crops grown at four villages around the Dabaoshan mine, South China. The heavy metal concentrations in paddy and garden soils exceeded the maximum allowable concentrations for Chinese agricultural soil. The paddy soil at Fandong village was heavily contaminated with Cu (703 mg kg^− 1), Zn (1100 mg kg^− 1), Pb (386 mg kg^− 1) and Cd (5.5 mg kg^− 1). Rice tended to accumulated higher Cd and Pb concentration in grain parts. The concentrations of Cd, Pb and Zn in vegetables exceeded the maximum permissible concentration in China. Taro grown at the four sampled villages accumulated high concentrations of Zn, Pb and Cd. Bio-accumulation factors for heavy metals in different vegetables showed a trend in the order: Cd > Zn > Cu > Pb. Bio-accumulation factors of heavy metals were significantly higher for leafy than for non-leafy vegetable. The target hazard quotient (THQ) of rice at four sites varied from 0.66-0.89 for Cu, 0.48-0.60 for Zn, 1.43-1.99 for Pb, and 2.61-6.25 for Cd. Estimated daily intake (EDI) and THQs for Cd and Pb of rice and vegetables exceeded the FAO/WHO permissible limit. Heavy metal contamination of food crops grown around the mine posed a great health risk to the local population through consumption of rice and vegetables.     

The effect of graded doses of cadmium on lead,zinc and copper content of target and indicator organs in rats

Eleven groups of inbred Wistar rats, five males and five females in each group, received graded doses of CdCl₂, from 0–25 ppm, in the drinking water from conception until sacrifice at the age of ten weeks. The Pb, Zn and Cu levels of various indicators and target organs were recorded by atomic absorption spectrophotometry. Cd concentrations above 5 ppm caused a significant increase in Zn content of kidneys, liver, spleen, heart and adrenal glands in most of the experimental groups, and in addition a significant positive correlation between Cd and Zn in the same tissues. With concentrations above 10 ppm, Zn contents of epiphyses and diaphyses decreased significantly, and through all groups there was a significant negative correlation between Zn and Cd in diaphysis. This local Zn deficit may cause a retarded growth of long bones. Cd supply resulted in a significant decrease in Zn content of incisors and molars, but did not significantly affect the Cu content. Neither were Zn nor Cu concentrations in hair affected. Cd supply led to a significantly increased storage of Cu in liver, spleen, heart and skeletal muscle and a positive correlation between Cd and Cu content in the same tissues. Cd administration caused a significant decrease of Pb concentrations in molars, hair, kidney cortex, heart, skeletal muscle and adrenal glands in several of the experimental groups, and also a significant negative correlation between Pb and Cd content of molars, hair, kidney cortex, liver and heart. This can be a result of decreased uptake, increased excretion or changes in the distribution pattern of Pb.     

Lung cancer incidence in a Chinese high background area — Epidemiological results and theoretical interpretation

A survey of inhabitant exposures arising from the inhalation of radon and thoron daughters, and lung cancer mortality has been carried out in two adjacent areas in Guangdong province, China, designated as the “high background” and the “control” area. Annual exposure rates are 0.38 WLM/yr in the high background, and 0.16 WLM/yr in the control area, while age-adjusted mortality rates are 2.7 per 10⁵ living people of all ages in the high background, and 2.9 per 10⁵ in the control area. From this data we conclude that we are unable to determine the excess lung cancer rate over normal fluctuations below a cumulative exposure of about 15 WLM. This conclusion is supported by lung cancer mortality data from an Austrian high background area.     

Volatile Organic Compounds in Ventilating Air in Buildings at Different Sampling Points in the Buildings and their Relationship with the Prevalence of Occupant Symptoms

Total volatile organic compounds (TVOC) are determined in intake, room-supply and room air in 86 office rooms in 29 office buildings in northern Sweden. Measurements of formaldehyde were also made in room air. Building and room characteristics were identified and symptom reports collected from 1087 office workers. Concentrations of TVOC and formaldehyde in room air were low, with mean values of 71 µg/m³ and 31 µg/m³, respectively. The TVOC concentration was generally lower in room air than in supply air or intake air. The “loss” (difference in measured values) of TVOC from supply to room air was associated with raised concentrations of formaldehyde and raised prevalences of occupant symptoms. High TVOC concentrations in room air were associated with reduced prevalences of occupant symptoms.     

Of the necessity of knowledge of the natural pedo-geochemical background content in the evaluation of the contamination of soils by trace elements

In order to evaluate the contamination of the Dornach (Switzerland) site within the framework of the CEEM-Soil project, each participating team was allowed to take a maximum of 15 samples. The French team's sampling was organized in such a way as to answer the following questions: (i) what is the natural concentration of the soils at this site (local pedo-geochemical background content)?; (ii) what are the levels of Cd, Cu, Pb and Zn contamination of the soil?; (iii) what is the depth reached by the surface contamination that is derived from atmospheric fallout?; (iv) how is the contamination spread along the longest axis of the area under study? The relationships between total Fe and the trace metals have allowed local variations in the natural pedo-geochemical background content to be detected and thus permitted the anthropogenic contamination to be estimated. There would appear to be a low level of Pb contamination over all the site investigated (an increase of the order of 5-10 mg kg(-1) on the background level), limited to the surface humus-bearing layers. There is also a significant contamination by Cu over all of the site (an increase of the order of 30-40 mg kg(-1)). This contamination has remained in the surface horizons (0-20 cm). Very high Zn and Cd concentrations have been found in the four surface (0-4 cm) and deep horizons (15-70 cm) taken under the forest and very much lower values in the samples taken from cultivated soils. The most likely explanation is an unequal inheritance between the upper part of the site (wooded with thinner very clayey soils) and the lower cultivated part of the site (with thicker less clayey soils developed in a loamy material). For various reasons, it seems unlikely that a contamination of the wooded part should be so much higher than the cultivated part due to the interception of atmospheric dust by the trees. The local pedo-geochemical background Cd and Zn content of the upper wooded part proved to be clearly higher than that which would be encountered in most soils of Switzerland and France. Given this evaluation of the background content, it seems that only the surface horizons have been affected by Zn contamination (an addition of approx. 60-100 mg kg(-1)). In the case of Cd, the increase in concentrations is only 0.5-1 mg kg(-1) for the ploughed horizons, as well as the for the A horizons.     

Distribution and transport of sediment-bound metal contaminants in the rio grande de tarcoles, costa rica (Central America)

A reconnaissance survey of the extent of metal contamination in the Rio Grande de Tarcoles river system of Costa Rica indicated high levels of chromium (Cr) in the fine-grain bed sediments (<60 μm) of tributaries downstream from leather tanneries (50–83 times Cr background or 3000–5000 μg/g). In the main channel of the river downstream of the San Jose urban area, Cr contamination in sediments was 4–6 times background and remained relatively constant over 50 km to the mouth of the river. Sediments from a mangrove swamp at the river mouth had Cr levels 2–3 times above background. Similar patterns of dilution were observed for lead (Pb) and zinc (Zn) sediment contamination, although the contamination levels were lower. The high affinity of Cr towards particulate phases, probably as Cr(III), allows the use of Cr contamination levels for delineating regions of deposition of fine-grained sediments and dilution of particle associated contaminants during transport and deposition.     

Free-ranging European bisons accumulate more cadmium in the liver and kidneys than domestic cattle in north-eastern Poland

It has been shown that free-ranging big game animals accumulate several-fold more cadmium (Cd) in the liver and kidneys than domestic animals. To examine possible reasons for this difference, in the present work we determined the concentrations of Cd in the liver and kidney cortex of European bisons (n=23) from Bia?owieza Forest (north-eastern Poland) and domestic cattle (n=15) from the same region; in addition, analyses of Cd in the grasses and soil as well as of soil pH were carried out. The accumulation of Cd in liver and kidney cortex of the female bisons correlated significantly with the age up to 7 years, but stabilized thereafter. The 7-12-year-old bisons had 2.14- and 2.25-fold higher concentrations of Cd in the liver and kidney cortex, respectively, than the age-matched domestic cattle. Notably, the Cd levels in the liver and kidneys of the 8-12-year-old cattle were comparable to those found in the 2-year-old and 4-6-year-old bisons, respectively. The content of Cd in the grasses from Bia?owieza Forest appeared to be 2.1-fold higher than that in the plants from the pastures. Similarly, the concentration of water-extractable Cd in the soil was 2.7-fold greater in Bia?owieza Forest than in the pastures, despite the fact that nitric acid-extractable Cd (total Cd) was similar in the soils from the two sites. The concentration of water-extractable Cd in the soil as well as the content of Cd in the grasses inversely correlated with soil pH, which appeared to be significantly lower in Bia?owieza Forest. These data indicate that soil pH is probably responsible for the higher concentrations of Cd in the feed and tissues of bisons as compared with those of domestic cattle.     

Transfer of 137Cs from Chernobyl debris and nuclear weapons fallout to different Swedish population groups

Data from measurements on the body burden of ¹³⁴Cs, ¹³⁷Cs and ⁴⁰K in various Swedish populations between 1959 and 2001 has been compiled into a national database. The compilation is a co-operation between the Departments of Radiation Physics in Malmö and Göteborg, the National Radiation Protection Authority (SSI) and the Swedish Defense Research Agency (FOI). In a previous study the effective ecological half time and the associated effective dose to various Swedish populations due to internal contamination of ¹³⁴Cs and ¹³⁷Cs have been assessed using the database. In this study values of human body burden have been combined with data on the local and regional ground deposition of fallout from nuclear weapons tests (only ¹³⁷Cs) and Chernobyl debris (both ¹³⁴Cs and ¹³⁷Cs), which have enabled estimates of the radioecological transfer in the studied populations.The assessment of the database shows that the transfer of radiocesium from Chernobyl fallout to humans varies considerably between various populations in Sweden. In terms of committed effective dose over a 70 y period from internal contamination per unit activity deposition, the general (predominantly urban) Swedish population obtains 20-30 μSv/kBq m^− 2. Four categories of populations exhibit higher radioecological transfer than the general population; i.) reindeer herders (∼700 μSv/kBq m^− 2), ii.) hunters in the counties dominated by forest vegetation (∼100 μSv/kBq m^− 2), iii.) rural non-farming populations living in sub-arctic areas (40-150 μSv/kBq m^− 2), and iv.) farmers (∼50 μSv/kBq m^− 2). Two important factors determine the aggregate transfer from ground deposition to man; i.) dietary habits (intakes of foodstuff originating from natural and semi-natural ecosystems), and ii.) inclination to follow the recommended food restriction by the authorities. The transfer to the general population is considerably lower (∼a factor of 3) for the Chernobyl fallout than during the 1960s and 70s, which is partly explained by a higher awareness of the pathways of radiocaesium to man both by the public and by the regulating authorities, and by the time-pattern of the nuclear weapons fallout during the growth season in Sweden.     

Seasonal concentrations of cadmium and zinc in native pasture plants: consequences for grazing animals

Aboveground concentrations of Cd and Zn in various grazing plants at three stages of the growing season are reported. The plants were collected at a natural habitat exposed to extensive atmospheric deposition of heavy metals from other parts of Europe. Concentrations of both metals varied considerably among species, also among morphologically similar species growing in the same soil. The two metals correlated in the material as a whole, but the concentration variations were most pronounced for Cd. There were also seasonal variations (generally a concentration reduction during spring). Transfer of metals from twigs to leaves seemed to differ between 'high' and 'low' metal accumulators. The inter-species and seasonal variations in plant metal concentrations complicate assessments of metal exposure to grazing animals through diet. By using diet information from a study conducted in an area similar to the present one, we roughly estimated a daily intake of 1-2 mg Cd for moose (Alces alces) in the autumn. Among the plant species investigated, Populus and Salix species were by far the most important Cd contributors. In areas where high Cd accumulators grow more widely, the daily Cd intake by moose could be as high as 7 mg or more.     

Selenium in the environment

Selenium is one of the most widely distributed elements of the earth's crust. Much of the selenium in the earth's crust occurs associated with sulfide minerals. The presence or absence of selenium in any soil is dependent upon the composition of the parent material, and is also dependent upon leaching or processes subsequent to soil formation, that may have added selenium. Selenium can be easily oxidized from Se⁰ to Se⁺⁴ or Se⁺⁶. Selenium is usually recovered as a by-product of the refining of the sulfide ores of other metals such as copper. The greatest amounts of selenium are used for the manufacture of the photoelectric cell.Selenium is taken up by plants as selenate, selenite or organic selenium. Se⁷⁵ selenite in 30 minutes was translocated primarily to selenomethionine. In sheep or pigs the duodenum is the main site of Se⁷⁵ absorption. Selenium is excreted in the feces, the urine, and the expired air, the amounts and proportions depending upon the level and form of the intake, the nature of the rest of the diet, and the species. A dietary intake of 0.1 μg/g Se provides a satisfactory margin of safety for grazing sheep and cattle. In humans, the recommended daily allowance for selenium is between 100 to 200 μg/day. The toxicity of selenium to animals varies with the amounts of chemical forms of selenium ingested, with the duration and continuity of intake, and with the type and nature of the diet, especially its protein and sulfate content.Deficiency of selenium results in selenium responsive diseases in various animal species, such as muscular dystrophy, exudative diathesis and hepatosis dietetica. Selenium also prevents several type of chemically induced cancer in animals, and, where more selenium occurs in the environment, human cancer death rates are lower. Selenium deficient rats and lambs develop abnormal electrocardiograms accompanied by blood pressure changes. Human heart disease mortality is also lower in the high selenium areas. In China, a large clinical trial is underway showing that selenium prevents a congestive heart failure in children from severely selenium deficient areas.     

Trace metal determination in total atmospheric deposition in rural and urban areas

The wet, dry and total atmospheric depositions of some metals (Al, Cd, Cr, Cu, Fe, Na, Pb and Zn) were sampled at two sites and atmospheric fallout fluxes were determined for these locations. This work, led by two different research groups, allowed to reach two main goals: to define a simple analytical procedure to secure accurate shipboard sampling and analysis of atmospheric deposition, and to assess anthropogenic impacts of heavy metals to the environment. The first step about the validation step showed that the prevalent deposition type was dry deposition which represents 40, 60 and 80% for Cd, Cu and Pb, respectively. This prevalence of dry deposition in total atmospheric fallout supported the necessity of funnel wall rinsing which contains 30, 50 and 40% of collected Cd, Cu and Pb, respectively. Moreover, the reproducibility of atmospheric deposition collection was determined. The second step was performed by comparing two sampling sites. A rural sampling site, situated in Morvan's regional park (250 km south-east of Paris), was chosen for its isolation from any local and regional contamination sources. Fluxes obtained in this area were compared with those obtained at an urban site (Créteil, suburb of Paris) allowing comparison between urban and rural areas and demonstrating the impact of anthropogenic activities on atmospheric deposition of Cr, Cu and Pb.