Renal Cadmium Concentrations Research Articles

Hepatic and renal trace element concentrations in American alligators (Alligator mississippiensis) following chronic dietary exposure to coal fly ash contaminated prey

Little is known about the propensity of crocodilians to bioaccumulate trace elements as a result of chronic dietary exposure. We exposed 36 juvenile alligators (Alligator mississippiensis) to one of four dietary treatments that varied in the relative frequency of meals containing prey from coal combustion waste (CCW)-contaminated habitats vs. prey from uncontaminated sites, and evaluated tissue residues and growth rates after 12 mo and 25 mo of exposure. Hepatic and renal concentrations of arsenic (As), cadmium (Cd) and selenium (Se) varied significantly among dietary treatment groups in a dose-dependent manner and were higher in kidneys than in livers. Exposure period did not affect Se or As levels but Cd levels were significantly higher after 25 mo than 12 mo of exposure. Kidney As and Se levels were negatively correlated with body size but neither growth rates nor body condition varied significantly among dietary treatment groups. Our study is among the first to experimentally examine bioaccumulation of trace element contaminants in crocodilians as a result of chronic dietary exposure. A combination of field surveys and laboratory experiments will be required to understand the effects of different exposure scenarios on tissue residues, and ultimately link these concentrations with effects on individual health.

Differences in radionuclide and heavy metal concentrations found in the kidneys of barren-ground caribou from the western Northwest Territories 1994/95 to 2000/01

Aluminum, nickel, cadmium, mercury, and lead concentrations were measured in the kidney tissue of known aged barren-ground caribou wintering in the western Northwest Territories harvested during winter 1994/1995 and during winters 2000/2001 and 2001/2002. 40K, 137Cs, and 210Pb concentrations were measured in the kidney tissue of known aged barren-ground caribou during winter 2000/2001 and compared to concentrations in winter 1993/1994 reported in Macdonald et al. (1996). Renal concentrations of aluminum were higher (P<0.001)in winter 2000/2001 than winter 1994/1995. Contrastingly renal concentrations of mercury were lower (P<0.001) in winter 2000/2001 than 1994/1995. 137Cs (P<0.02), 40K (P=0.01), 210Pb (P<0.01) had lower renal concentrations in winter 2000/2001 than 1993/1994. Renal concentrations of cadmium (P<0.001) and 137Cs (P<0.04) had a positive relationship with caribou age. We also document renal concentrations of arsenic, copper, selenium, zinc, 232Th, 226Ra, and 235U in the kidneys of caribou harvested in winters 2000/2001 and 2001/2002. Renal zinc concentrations were positively correlated with the age of caribou.

Liver Parasites and Body Condition in Relation to Environmental Contaminants in Caribou (<i>Rangifer tarandus</i>) from Labrador, Canada

Over the last several decades, elders and hunters of the Innu Nation in Labrador, Canada, have expressed concerns over perceived declines in environmental health and the integrity of country food, including caribou. The primary objective of this study was to determine links between specific health parameters and contaminants found in caribou from the George River herd. Twenty-seven caribou killed by local Innu hunters between February and December 2001 were evaluated for gross and microscopic pathology, body condition, liver parasitology, and contaminant levels in kidney and fat. Overall, the sampled caribou appeared to be in adequate body condition for the time of year, and no clinically significant lesions were found. Concentrations of selenium, metals (Hg, Cd, and Pb), 20 organochlorine pesticides (HCB, a-HCH, g-HCH, aldrin, dieldrin, methoxychlor, mirex, a- and b-endosulfan, heptachlor, heptachlor epoxide, g-CHL, cis-CHL, trans-nonachlor, and o,p'- and p,p'-DDD, DDE, DDT), and 24 PCB congeners were within the ranges reported for caribou in Canada. In general, contaminant levels were relatively low, with the exception of cadmium in kidneys (geometric mean: 6.5 μg/g wet weight; range: 1.5–44.0 μg/g). Two types of liver parasites were found: the liver fluke Fascioloides magna (prevalence: 78%; geometric mean abundance: 4.2 flukes/caribou) and a tapeworm larva consistent with Taenia hydatigena (prevalence: 50%; geometric mean abundance: 0.6 larvae/caribou). Using multiple variable regression analysis, we found renal concentrations of cadmium to be positively associated, and selenium to be negatively associated, with F. magna abundance.

The European maximum level for cadmium in bovine kidneys is in Belgium only realistic for cattle up to 2 years of age

The effect of animal age on concentrations of cadmium, lead, arsenic, copper and zinc in bovine tissues (meat, kidney and liver) sampled from animals reared in contaminated areas or reference regions in Belgium was investigated. For cadmium concentrations in meat samples analysis of variance (ANOVA) showed an increasing trend with age. In addition, a significant positive linear relation (p < 0.05) was found between animal age and renal (R 2 = 0.56) or hepatic (R 2 = 0.39) cadmium levels. Lead concentrations in kidneys and liver also increased with age, but the effect was blurred, likely due to the internal remobilization of lead. For the other trace elements (arsenic, copper, zinc) no relationship could be found between their concentration in meat, kidneys or liver and animal age. Renal cadmium concentrations were predicted for bovines at different ages by using the slope of the linear regression equation, and by taking into account its 95% confidence interval. Calculations for 2-year-old animals from reference areas showed that in this group the European maximum level of 1 mg kg−1 for cadmium in kidneys would be exceeded in zero to 5% of cases. If a general rejection percentage of maximum 5% would be desirable for kidneys sampled in the reference areas (according to the ALARA principle–‘as low as reasonably achievable’–of European Union policy), then (1) kidneys from animals older than 2 years from the reference areas should a priori not be considered suitable to be placed on the market, or (2) the maximum level for cadmium in kidneys should be increased to 3 mg kg−1. The latter would bear negligible risks for the general population and the majority of high-level kidney consumers. On the other hand, bovine kidneys from the most contaminated areas are not suitable to be brought into the food chain because it is predicted that the maximum level is already exceeded by more than 5% of the 1-year-old animals.

Cephalopods and cetaceans as indicators of offshore bioavailability of cadmium off Central South Brazil Bight

Regarding Brazilian coast, industrial and urban developments are concentrated along Central South Brazil Bight. Samples from inshore and offshore species from the concerned area were analyzed, comprising 24 cetaceans (9 species) and 32 squids (2 species). Cadmium was determined by GFAAS and our results were in agreement with certified values (DOLT-2, NRCC). Mean cadmium concentration (in μg/g, wet weight) observed in the digestive gland of sexually mature Argentine short-finned squids ( Illex argentinus) was 1002.9. To our knowledge this is the highest cadmium level ever reported for a cephalopod. Concerning cetaceans, our results include one of the highest renal cadmium concentrations described for striped dolphins (71.29 μg/g, wet weight). Anthropogenic action, upwelling and cannibalism of Argentine short-finned squid on the studied area are possible reasons for such remarkable cadmium concentrations.

Metal bioaccumulation in the greater white-toothed shrew, Crocidura russula, inhabiting an abandoned pyrite mine site

Hepatic and renal concentrations of iron, magnesium, zinc, lead, copper, manganese, mercury, cadmium, molybdenum, chromium, and nickel were quantified in shrews ( Crocidura russula) inhabiting a pyrite mine site in Portugal. Several morphological parameters (body weight, residual index, and relative weights) were also examined to clarify the physiological effects of pollution. Shrews from the mine showed increased bioavailability of Fe, Pb, Hg, Cd, Mo, and Ni in comparison with reference specimens. Adult shrews had the highest Cd levels while Cr and Ni concentrations diminished. Intersexual differences were found for Mo and Ni. As a consequence of metal pollution, the relative hepatic weight was higher in shrews from the mine site when compared with reference specimens. These data indicate that C. russula is a good bioindicator of metal pollution. We also evaluated the toxic effects of Pb, Hg, Cd, and Ni, because several shrews from the polluted site showed high concentrations of these metals. To approximate at the real biological impact of abandoned mines, after this first step it is necessary to associate the bioaccumulation levels and morphological effects with other physiological, ecological and genetical biomarkers.

Temporal and geographic trends in trace element concentrations in moose from Yukon, Canada

The Yukon Contaminants Committee has conducted a hunter survey since 1994, annually requesting tissue samples from successful moose hunters in the Yukon. Moose kidney, liver and muscle tissue were analyzed for arsenic, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, selenium and zinc. Levels of most trace elements measured were not of concern toxicologically or in terms of deficiencies. Although hepatic selenium concentrations in Yukon moose were high compared to moose from other locations, and to domestic cattle, no indications of selenium toxicity have been observed. Renal and hepatic concentrations of cadmium in Yukon moose were also high when compared with moose from other locations. Results from this study suggest that 1) some moose in this area may be suffering from sublethal effects of Cd toxicity, 2) moose in this area may have evolved a high level of natural cadmium tolerance, 3) moose in this area may have developed a high level of cadmium tolerance over their lifetimes, or 4) moose, as a species, have a high level of Cd tolerance. Health Canada has recommended limiting consumption of Yukon moose kidneys and livers to one/year/person. Cadmium concentrations were positively correlated with age in moose kidneys, while arsenic, copper, molybdenum and selenium showed a negative correlation. Renal chromium and zinc showed an increasing trend from 1994–2001, while copper showed a decreasing trend, although in all three cases the r-values and the changes over time were low. None of the other elements tested exhibited a significant change over time. Analysis of moose renal element concentrations with stream sediment element concentrations was carried out on an ecoregion basis, a game management zone basis and a moose home range basis. Results suggest that, at least to some degree, renal element concentrations in moose are affected by the geology of their environment, particularly for cadmium, arsenic and lead. The results of these analyses are consistent with the hypothesis that the high levels of cadmium found in Yukon moose are coming from naturally occurring geological sources, likely via hyperaccumulating plants such as willows.

Biomarker responses in nesting, common eiders in the Canadian arctic in relation to tissue cadmium, mercury and selenium concentrations.

Populations of many North American sea ducks are declining. Biomarkers may offer valuable insights regarding the health and fitness of sea ducks in relation to contaminant burdens. In this study we examined body condition, immune function, corticosterone stress response, liver glycogen levels and vitamin A status in relation to tissue concentrations of mercury, selenium and cadmium in female common eiders during the nesting period. The study was conducted in the eastern Canadian arctic during July, 2000. Hepatic mercury, selenium and renal cadmium concentrations ranged 1.5-9.8, 6.5-47.5 and 74-389 microg/g, dry wt, respectively. Mercury concentrations were negatively related to dissection body mass, heart mass and fat mass. Cadmium concentrations were negatively related to mass at capture and dissection mass after controlling for the mercury concentration-dissection mass relationship. Cell-mediated immunity was assessed by the skin swelling reaction to an injection of phytohemagglutinin-P, and was unrelated to metal concentrations. After adjusting the corticosterone concentration to account for the time between capture and sampling, there was a negative relationship between the residual corticosterone concentration and selenium. Liver glycogen concentrations were not significantly related to metal concentrations. Mercury concentrations were positively related to those of hepatic retinol and retinyl palmitate and the ratio of the retinol to retinyl palmitate in liver. They were negatively related to the ratio of plasma to liver retinol. Our findings do not indicate that exposure to metals may have adversely affected the health of these birds. They do, however, suggest that more research is required to elucidate mechanisms by which exposure to these metals could impact body condition.

Immune Function, Stress Response, and Body Condition in Arctic-Breeding Common Eiders in Relation to Cadmium, Mercury, and Selenium Concentrations

We examined relationships between trace metal concentrations in tissues of common eider ducks (cadmium, mercury, and selenium) and selected biomarkers of health (stress response, immune function, and body condition). This study was conducted at an eider nesting colony in the Canadian arctic in 1998 and 1999. Capture-induced stress, measured as the rise in corticosterone concentrations following capture, was positively related ( P=0.03) to renal cadmium concentration in 1998 when incubating eiders were sampled, but not in 1999 when prenesting eiders were sampled. Stress response was inversely related ( P=0.02) to selenium concentrations in 1999. Following capture and blood sampling in 1999, eiders were placed in a flight pen on-site for eight days in order to examine immune function. Cell-mediated immunity, measured as the skin-swelling response to an intradermal injection of phytohemagglutinin-P, (PHA-P), was positively related ( P=0.003) to hepatic selenium. The heterophil:lymphocyte ratio was inversely related ( P=0.08) to hepatic selenium. In 1998, selenium was positively related to body mass ( P=0.01), abdominal fat mass ( P=0.07), kidney mass ( P=0.03), and liver mass ( P=0.07). In 1999, hepatic mercury was negatively related to abdominal fat mass ( P=0.01), spleen mass ( P=0.07) and body mass at capture ( P=0.09) in prenesting eiders.

Concentrations of cadmium, mercury and selenium in blood, liver and kidney of common eider ducks from the Canadian arctic.

We determined concentrations of selected trace elements in livers, kidneys and blood samples from common eiders (Somateria mollissima borealis) from the eastern Canadian arctic during 1997 and 1998. Concentrations of total mercury and organic mercury were generally low in the livers of these birds (less than 6 and 4 microg g(-1) dry wt, respectively). Selenium ranged between 11-47 microg g(-1) in livers. Renal cadmium concentrations were among the highest ever published for this species (range: 47-281 microg g(-1)). The regressions of log-transformed concentrations of these trace elements in blood samples on those in liver or kidney were significant (all P-values < 0.05) and positive. However, except for organic mercury (R2 = 0.83), the co-efficients of determination were low to moderate (range of R2: 0.26-0.52), suggesting poor to moderate predictive capability. Furthermore, the relationships between total mercury in blood and liver changed between 1997 and 1998, suggesting that it would not be possible to predict consistently, concentrations of mercury in blood from those in liver based on samples taken in one year. Blood samples can be used to determine concentrations of these trace elements in common eiders (and probably other sea duck species as well). The use of blood samples is especially warranted when it is undesirable to kill the animal such as when working with rare or endangered sea duck species or when the objective is to relate trace element exposure to annual survival rates. However, the predictive equations developed here should not be used to predict expected concentrations in one type of tissue from those in the other.

Renal Cadmium Concentrations in Mice and Shrews Collected from Forest Lands Treated with Biosolids

AbstractThis study examined the long‐term effects of biosolids (mixed domestic‐industrial anaerobically digested sewage sludge) application to forested lands on kidney Cd concentration in omnivorous mice (Peromyscus sp.) and insectivorous shrews (Sorex sp.). Animals from eight biosolids‐treated sites, located in two different areas in western Washington, were examined and compared with those captured on seven control sites. Varying amounts of biosolids had been applied either 4, 11, or 15 yr previously. Kidney Cd was significantly greater in Sorex than in Peromyscus on all treatment sites. Though Cd levels in Peromyscus from some treatment sites were significantly increased over corresponding controls, levels from the highest dose treatment sites were comparable to controls found at other sites, so it is doubtful that biosolids had a significant long‐term effect on the omnivores. Cadmium levels in Sorex from all treatment sites except those receiving the lowest dose of biosolids were significantly greater than controls. Kidney Cd concentrations in shrews trapped from the 11‐yr postapplication sites were approximately equivalent to those in shrews trapped 2 yr after application on those same sites. However, the elevated levels of Cd found in Sorex, while highly significant statistically, did not appear to be biologically significant.

Contaminants and Sea Ducks in Alaska and the Circumpolar Region

We review nesting sea duck population declines in Alaska during recent decades and explore the possibility that contaminants may be implicated. Aerial surveys of the surf scoter (Melanitta perspicillata), white-winged scoter (M. fusca), black scoter (M. nigra), oldsqaw (Clangula hyemalis), spectacled eider (Somateria fischeri), and Steller's eider (Polysticta stellei) show long-term breeding population declines, especially the latter three species. The spectacled eider was recently classified threatened under the Endangered Species Act. In addition, three other diving ducks, which commonly winter in coastal areas, have declined from unknown causes. Large die-offs of all three species of scoters during molt, a period of high energy demand, were documented in August 1990, 1991, and 1992 at coastal reefs in southeastern Alaska. There was no evidence of infectious diseases in those scoters. The die-offs may or may not be associated with the long-term declines. Many scoters had elevated renal concentrations of cadmium (high of 375 micrograms/g dry weight [dw]). Effects of cadmium in sea ducks are not well understood. Selenium concentrations in livers of nesting white-winged scoters were high; however, the eggs they laid contained less selenium than expected based on relationships for freshwater bird species. Histological evaluation found a high prevalence of hepatocellular vacuolation (49%), a degenerative change frequently associated with sublethal toxic insult. Cadmium and selenium mean liver concentrations were generally higher in those birds with more severe vacuolation; however, relationships were not statistically significant. We do not know if sea duck population declines are related to metals or other contaminants.

Contaminants and sea ducks in Alaska and the circumpolar region.

We review nesting sea duck population declines in Alaska during recent decades and explore the possibility that contaminants may be implicated. Aerial surveys of the surf scoter (Melanitta perspicillata), white-winged scoter (M. fusca), black scoter (M. nigra), oldsqaw (Clangula hyemalis), spectacled eider (Somateria fischeri), and Steller's eider (Polysticta stellei) show long-term breeding population declines, especially the latter three species. The spectacled eider was recently classified threatened under the Endangered Species Act. In addition, three other diving ducks, which commonly winter in coastal areas, have declined from unknown causes. Large die-offs of all three species of scoters during molt, a period of high energy demand, were documented in August 1990, 1991, and 1992 at coastal reefs in southeastern Alaska. There was no evidence of infectious diseases in those scoters. The die-offs may or may not be associated with the long-term declines. Many scoters had elevated renal concentrations of cadmium (high of 375 micrograms/g dry weight [dw]). Effects of cadmium in sea ducks are not well understood. Selenium concentrations in livers of nesting white-winged scoters were high; however, the eggs they laid contained less selenium than expected based on relationships for freshwater bird species. Histological evaluation found a high prevalence of hepatocellular vacuolation (49%), a degenerative change frequently associated with sublethal toxic insult. Cadmium and selenium mean liver concentrations were generally higher in those birds with more severe vacuolation; however, relationships were not statistically significant. We do not know if sea duck population declines are related to metals or other contaminants.

The ecotoxicological significance of cadmium intake and residues in terrestrial small mammals

Little is known about the ecotoxicological hazard of cadmium to wild small mammals. This paper reviewed laboratory and field studies to determine: (i) intake and residue lowest-observable-adverse-effect-levels (LOAELs) for the ecologically important parameters of reproduction and development; (ii) whether these LOAELs are exceeded by wild small mammals on contaminated habitats and what adverse effects result; and (iii) which species may be at most risk from cadmium. The intake LOAEL in laboratory rodents was 3.5–7.5 mg kg −1 body wt day −1 and the residue LOAEL, based on cellular damage in the kidney, was a renal cadmium concentration of 105 mg kg −1 dry wt. On contaminated habitats, these LOAELs are exceeded by common shrews Sorex araneus but not by wild rodents. However, there is little evidence of adverse cadmium-mediated effects in common shrews and this species may be tolerant to cadmium exposure. Large cadmium concentrations in body organs may simply reflect an ability to store cadmium in a nontoxic, metallothionein-bound state. In contrast, studies suggest that microtine voles may be sensitive to cadmium and, despite their relatively low cadmium intake and accumulated residues, may suffer adverse effects. The need to establish dose-residue-effect relationships for intakes and residues which are appropriate for wild species and also based on ecologically important parameters is discussed.

Cadmium in caribou and muskoxen from the Canadian Yukon and Northwest territories

Cadmium, zinc, copper and metallothionein concentrations were measured in liver and kidney tissue of caribou and muskoxen collected from various sites in the Canadian Yukon and Northwest Territories. Cadmium concentrations in caribou tissues were substantially higher than in muskoxen for all age classes and were comparable to concentrations reported for caribou from northern Quebec and Norway. No geographical site differences in cadmium concentration were observed. Cadmium concentrations were positively correlated with age for both caribou and muskoxen. The highest cadmium concentration observed (166 μg/g dry wt.) was in renal tissue of a 15-year-old caribou. Metal concentrations tended to be higher in spring than in fall for animals of comparable age. Renal cadmium concentrations were highly correlated with metallothionein concentrations, especially for cadmium concentrations exceeding 20 μg/g (dry wt.). It is estimated that the regular weekly consumption of kidney tissue from Arctic caribou of any age, and from muskoxen older than 1 year, will probably cause the WHO provisional weekly tolerable intake of cadmium to be exceeded.

Renal binding of cadmium in the rat following intragastric exposure

Renal binding of cadmium was compared in groups of rats administered cadmium intragastrically or subcutaneously in doses resulting in similar renal cadmium concentration. In rats administered cadmium intragastrically the renal concentrations of copper and metallothionein were lower, suggesting disturbance in copper metabolism. These changes were alleviated gradually in the post-exposure period. In experiments with 64Cu it has been shown that intragastric exposure to cadmium reduced copper absorption to ab about 21% of that in the control rats, thus explaining the poor copper availability for renal binding of cadmium in the form of Cd, Cu-metallothionein. Changes in zinc uptake were less strongly marked and were limited to slight decrease of zinc content in the kidneys.

On the role of metallothionein in cadmium induced renal toxicity.

Metallothionein plays an important role in the metabolism and toxicity of cadmium. Human beings are exposed to increasing amounts of cadmium. The critical organ in long term cadmium exposure is the kidney. Some groups in the population fall within the risk zone for developing renal tubular dysfunction from cadmium exposure. After absorption, cadmium is to a large extent distributed to the liver where it is bound to and induces the synthesis of metallothionein. Subsequently metallothionein-bound cadmium is slowly released into blood and efficiently taken up by renal tubular cells after glomerular filtration. The biological half-time of cadmium in the human kidney is considered to be very long: 10-15 years and this explains the life-long accumulation of cadmium, reaching a toxic concentration of approximately 200 ug/g in excessively exposed individuals. Human adult renal metallothionein has a natural content of cadmium which also induces the resynthesis of this protein upon its catabolism. This could be one explanation of the long biological half-time which has been reported for cadmium. Injection of metallothionein-bound cadmium can induce renal tubular kidney dysfunction at lower renal cadmium concentrations (10-20 ug/g), probably because of the fast catabolism and relatively slow synthesis of metallothionein in renal cells. A model of these and other mechanisms causing tubular kidney damage in cadmium exposure is presented.

Mechanisms of cardiovascular regulation in male rabbits chronically exposed to cadmium.

Male rabbits received 20 micrograms/ml of cadmium in drinking water for nine months. At the end of the treatment aortic vascular resistance was increased, whereas maximum rate of increase in left ventricular pressure, aortic blood flow, stroke volume, cardiac output, left ventricular minute work, and left ventricular stroke work were reduced. Arterial blood pressure, heart rate, and the index of myocardial oxygen consumption were not modified. The exposed rabbits also showed reduced pressor responses to vagotomy, increased cardiovascular responses to angiotensin I and II and isoprenaline, and lower responses to serotonin and guanethidine; the bradycardia induced by clonidine was augmented; the cardiovascular effects of bilateral carotid occlusion, hexamethonium, phenylephrine, histamine, acetylcholine, tyramine, papaverine and verapamil were unaltered. In the treated rabbits cadmium was appreciably higher in the kidney than in the heart; however, renal concentrations of cadmium were lower than those reported as critical for workers exposed to cadmium. Zinc was increased in the kidney but not in the heart, whereas copper remained unchanged in the examined organs. In rabbits treated with cadmium the increased aortic vascular resistance and the reduced myocardial contractility contribute to preserve a haemodynamic equilibrium without alteration of blood pressure and heart rate; the question of whether a similar condition may be present in people exposed to cadmium with normal cardiovascular parameters is discussed.

Dietary exposure to cadmium and health effects: impact of environmental changes.

Cadmium exposure, metabolism, and effects are described especially in relation to dietary intakes. Data on dietary intakes in several countries have been complied from studies using the duplicate diet method or fecal analysis. These two methods seem to give more accurate data than estimates based on cadmium concentrations in food classes and food consumption (composite method). The present data on absorption and retention of ingested cadmium indicate that normally less than 5% is ingested, but absorption may increase in women who have iron deficiency. Earlier estimates of the critical concentration in renal cortex being about 200 mg/kg wet weight still seem to be valid. New information is available on present renal levels and their distribution in the general population. The present margin of safety with regard to risk for renal effects is small. To predict future health risks from increases in dietary cadmium due to environmental changes such as acid deposition, it is necessary that the models used are based on correct assumptions. Of interest are the distributions of dietary intake, gastrointestinal absorption, and renal cadmium concentrations. These distributions are normal or lognormal, and since standard deviations are used when estimating risks, it is of paramount importance that the standard deviations are estimated as accurately as possible. At present it is not possible to quantify the effects attributed to acid rain only; account must be also be taken of cadmium added to, e.g., soil by use of sewage sludge and other fertilizers. In addition to risks to human health, cadmium also poses a threat to horses, which generally have renal cadmium concentrations several times higher than adult humans. It is recommended that horses should be monitored in areas when acid deposition is high. Such monitoring might provide valuable information about impact of acid rain.

Dietary Exposure to Cadmium and Health Effects: Impact of Environmental Changes

Cadmium exposure, metabolism, and effects are described especially in relation to dietary intakes. Data on dietary intakes in several countries have been complied from studies using the duplicate diet method or fecal analysis. These two methods seem to give more accurate data than estimates based on cadmium concentrations in food classes and food consumption (composite method). The present data on absorption and retention of ingested cadmium indicate that normally less than 5% is ingested, but absorption may increase in women who have iron deficiency. Earlier estimates of the critical concentration in renal cortex being about 200 mg/kg wet weight still seem to be valid. New information is available on present renal levels and their distribution in the general population. The present margin of safety with regard to risk for renal effects is small. To predict future health risks from increases in dietary cadmium due to environmental changes such as acid deposition, it is necessary that the models used are based on correct assumptions. Of interest are the distributions of dietary intake, gastrointestinal absorption, and renal cadmium concentrations. These distributions are normal or lognormal, and since standard deviations are used when estimating risks, it is of paramount importance that the standard deviations are estimated as accurately as possible. At present it is not possible to quantify the effects attributed to acid rain only; account must be also be taken of cadmium added to, e.g., soil by use of sewage sludge and other fertilizers. In addition to risks to human health, cadmium also poses a threat to horses, which generally have renal cadmium concentrations several times higher than adult humans. It is recommended that horses should be monitored in areas when acid deposition is high. Such monitoring might provide valuable information about impact of acid rain.