Cobalt-beer cardiomyopathy. A clinical and pathologic study of twenty-eight cases

31-day study of cobalt(II) chloride ingestion in humans: pharmacokinetics and clinical effects

The United Kingdom Expert Group on Vitamins and Minerals concluded that ingesting cobalt (Co)-containing supplements up to 1400 μg Co/d is unlikely to produce adverse health effects. However, the associated blood Co concentrations and safety of Co-containing dietary supplements have not been fully characterized. Thus, blood Co kinetics and a toxicological assessment of hematological and biochemical parameters were evaluated following Co dietary supplementation in 5 male and 5 female volunteers who ingested approximately 1000 μg Co/d (10-19 μg Co/kg-d) as cobalt(II) chloride for a period of 31 d. Supplement intake was not associated with significant overt adverse events, alterations in clinical chemistries including blood counts and indicators of thyroid, cardiac, liver, or kidney functions, or metal sensitization. A non-clinically significant (<5%) increase in hemoglobin, hematocrit, and red blood cell (RBC) counts were observed in males but not females 1 wk after dose termination. Mean Co concentrations in whole blood/serum after 31 d of dosing were approximately two-fold higher in females (33/53 μg/L) than in males (16/21 μg/L). In general, steady-state concentrations of Co were achieved in whole blood and/or red blood cells (RBC) within 14-24 d. Temporal patterns of whole blood and serum Co concentrations indicated metal sequestration in RBC accompanied by slower whole blood clearance compared to serum. Data also indicated that peak whole blood Co concentrations up to 91.4 μg/L were not associated with clinically significant changes in clinical chemistries. In addition, Co blood concentrations and systemic uptake via ingestion were generally higher in females.

A biodistribution and toxicity study of cobalt dichloride-N-acetyl cysteine in an implantable MRI marker for prostate cancer treatment

PURPOSE

C4, a cobalt dichloride-N-acetyl cysteine complex, is being developed as a positive-signal magnetic resonance imaging (MRI) marker to localize implanted radioactive seeds in prostate brachytherapy. We evaluated the toxicity and biodistribution of C4 in rats with the goal of simulating the systemic effects of potential leakage from C4 MRI markers within the prostate.

METHODS AND MATERIALS

9-μL doses (equivalent to leakage from 120 markers in a human) of control solution (0.9% sodium chloride), 1% (proposed for clinical use), and 10% C4 solution were injected into the prostates of male Sprague-Dawley rats via laparotomy. Organ toxicity and cobalt disposition in plasma, tissues, feces, and urine were evaluated.

RESULTS

No C4-related morbidity or mortality was observed in the biodistribution arm (60 rats). Biodistribution was measurable after 10% C4 injection: cobalt was cleared rapidly from periprostatic tissue; mean concentrations in prostate were 163 μg/g and 268 μg/g at 5 and 30 minutes but were undetectable by 60 minutes. Expected dual renal-hepatic elimination was observed, with percentages of injected dose recovered in tissues of 39.0 ± 5.6% (liver), >11.8 ± 6.5% (prostate), and >5.3 ± 0.9% (kidney), with low plasma concentrations detected up to 1 hour (1.40 μg/mL at 5-60 minutes). Excretion in urine was 13.1 ± 4.6%, with 3.1 ± 0.54% recovered in feces by 24 hours. In the toxicity arm, 3 animals died in the control group and 1 each in the 1% and 10% groups from surgical or anesthesia-related complications; all others survived to scheduled termination at 14 days. No C4-related adverse clinical signs or organ toxicity were observed.

CONCLUSION

C4-related toxicity was not observed at exposures at least 10-fold the exposure proposed for use in humans. These data demonstrating lack of systemic toxicity with dual routes of elimination in the event of in situ rupture suggest that C4 warrants further investigation as an MRI marker for prostate brachytherapy.

Dose-response relationships for blood cobalt concentrations and health effects: a review of the literature and application of a biokinetic model

Cobalt (Co) is an essential component of vitamin B(12). As with all metals, at sufficiently high doses, Co may exert detrimental effects on different organ systems, and adverse responses have been observed in animals, patients undergoing Co therapy, and workers exposed to respirable Co particulates. Although blood Co concentrations are postulated to be the most accurate indicator of ongoing Co exposure, little is known regarding the dose-response relationships between blood Co concentrations and adverse health effects in various organ systems. In this analysis, the animal toxicology and epidemiology literature were evaluated to identify blood Co concentrations at which effects have, and have not, been reported. Where necessary, a biokinetic model was used to convert oral doses to blood Co concentrations. Our results indicated that blood Co concentrations of 300 μg/L and less have not been associated with adverse responses of any type in humans. Concentrations of 300 μg/L and higher were associated with certain hematological and reversible endocrine responses, including polycythemia and reduced iodide uptake. Blood Co concentrations of 700-800 μg Co/L and higher may pose a risk of more serious neurological, reproductive, or cardiac effects. These blood concentrations should be useful to clinicians and toxicologists who are attempting to interpret blood Co concentrations in exposed individuals.

High human exposure to cobalt and other metals in Katanga, a mining area of the Democratic Republic of Congo

BACKGROUND AND OBJECTIVES

The human health impact of the historic and current mining and processing of non-ferrous metals in the African Copperbelt is not known. This study assessed the exposure to metals in the population of Katanga, in the south east of the Democratic Republic of Congo, using biomonitoring.

METHODS

Seventeen metals (including Cd, Co, Cu, Pb, U) and non-metals (including As) were measured by ICP-MS in urine spot samples from 351 subjects (32% women), aged 2-74 yr (mean 33 yr). Forty subjects (controls) lived 400 km outside the mining area; 311 subjects lived in the mining area, either very close (< 3 km) (n=179; 6 communities) or moderately close (3-10 km) (n=132; 4 communities) to mines or smelting plants.

RESULTS

For all metals (except Ni) urinary concentrations were significantly higher in subjects from the mining area than in control subjects. In subjects living very close to mines or smelting plants, the geometric means (25th-75th percentile) of urinary concentrations, expressed as microg/g creatinine, were 17.8 (10.9-29.0) for As, 0.75 (0.38-1.16) for Cd, 15.7 (5.27-43.2) for Co, 17.1 (8.44-43.2) for Cu, 3.17 (1.47-5.49) for Pb and 0.028 (0.013-0.065) for U, these values being significantly higher than those of subjects living 3-10 km from mines or industrial operations. Urinary Co concentrations were markedly elevated, exceeding 15 microg/g creatinine in 53% of the subjects, and even 87% of children (<14 yr), living very close to the mining areas. Urinary As was also high (79% above 10 microg/g creatinine in subjects living very close to the mining areas). Compared with background values from the US general population, subjects living very close to areas of mining or refining had 4-, 43-, 5- and 4-fold higher urinary concentrations of Cd, Co, Pb and U, respectively.

CONCLUSIONS

This first biomonitoring study of metal exposure in the African Copperbelt reveals a substantial exposure to several metals, especially in children. The urinary Co concentrations found in this population are the highest ever reported for a general population. The pathways of exposure and health significance of these findings need to be further investigated.

Erythropoiesis-stimulating agents and other methods to enhance oxygen transport

Oxygen is essential for life, and the body has developed an exquisite method to collect oxygen in the lungs and transport it to the tissues. Hb contained within red blood cells (RBCs), is the key oxygen-carrying component in blood, and levels of RBCs are tightly controlled according to demand for oxygen. The availability of oxygen plays a critical role in athletic performance, and agents that enhance oxygen delivery to tissues increase aerobic power. Early methods to increase oxygen delivery included training at altitude, and later, transfusion of packed RBCs. A breakthrough in understanding how RBC formation is controlled included the discovery of erythropoietin (Epo) and cloning of the EPO gene. Cloning of the EPO gene was followed by commercial development of recombinant human Epo (rHuEpo). Legitimate use of this and other agents that affect oxygen delivery is important in the treatment of anaemia (low Hb levels) in patients with chronic kidney disease or in cancer patients with chemotherapy-induced anaemia. However, competitive sports was affected by illicit use of rHuEpo to enhance performance. Testing methods for these agents resulted in a cat-and-mouse game, with testing labs attempting to detect the use of a drug or blood product to improve athletic performance (doping) and certain athletes developing methods to use the agents without being detected. This article examines the current methods to enhance aerobic performance and the methods to detect illicit use.

Inducible nitric oxide synthase attenuates adrenergic signaling in alcohol fed rats

Chronic, excessive alcohol consumption is associated with myocardial dysfunction in humans. The molecular mechanisms and cellular signaling pathways contributing to this cardiac dysfunction remain largely unknown. This study examined the effects of chronic alcohol consumption on myocardial function and cardiac myocyte signaling pathways. Adult male rats were fed a commercially prepared diet containing either ethanol (13 g/kg/d) or isocaloric control diet for 1 month. In vivo hemodynamics were measured in awake rats after inserting a catheter tip in the left ventricle under general anesthesia. Ventricular dysfunction was evidenced in awake, alcohol-fed rats by increased left ventricular end diastolic pressure, decreased systolic developed left ventricular pressure, and decreases in both positive and negative dp/dt compared with controls. Cardiac myocytes isolated from alcohol-fed rats also demonstrated an attenuated response to the beta-adrenergic agonist, isoproterenol, compared to controls. This response was significantly reversed by the nitric oxide synthase (NOS) inhibitor, N-monomethyl-L-arginine (L-NMMA). Western analyses confirmed inducible nitric oxide synthase (iNOS) protein synthesis in cardiac myocytes isolated from alcohol fed rats. It is therefore concluded that chronic alcohol ingestion results in iNOS-mediated attenuation of adrenergic signaling and depression in both systolic and diastolic function in rats.

Reversible cardiomyopathies

Cardiomyopathy represents a diverse and heterogenous group of disorders affecting the myocardium and ultimately resulting in cardiac dysfunction. The prevalence of heart failure is high (5 million symptomatic patients in the United States) and increasing. Cardiomyopathy is the leading cause of hospitalization in patients older than 65 years of age, resulting in enormous healthcare expenditure and lost productivity. Ischemic cardiomyopathy accounts for about half of these patients, but in several large clinical trials the prevalence of potentially reversible nonischemic cardiomyopathy is also significant, ranging from 20% to 50%. There is epidemiological evidence that the prognosis of these reversible nonischemic cardiomyopathies is better than ischemic or other nonreversible cardiomyopathies. Early and precise diagnosis of the etiology of heart failure is important for determining prognosis and effective treatments.

Global gene expression profiling in human lung cells exposed to cobalt

BACKGROUND

It has been estimated that more than 1 million workers in the United States are exposed to cobalt. Occupational exposure to 59 Co occurs mainly via inhalation and leads to various lung diseases. Cobalt is classified by the IARC as a possible human carcinogen (group 2B). Although there is evidence for in vivo and in vitro toxicity, the mechanisms of cobalt-induced lung toxicity are not fully known. The purpose of this work was to identify potential signatures of acute cobalt exposure using a toxicogenomic approach. Data analysis focused on some cellular processes and protein targets that are thought to be relevant for carcinogenesis, transport and biomarker research.

RESULTS

A time course transcriptome analysis was performed on A549 human pulmonary cells, leading to the identification of 85 genes which are repressed or induced in response to soluble 59 Co. A group of 29 of these genes, representing the main biological functions, was assessed by quantitative RT-PCR. The expression profiles of six of them were then tested by quantitative RT-PCR in a time-dependent manner and three modulations were confirmed by Western blotting. The 85 modulated genes include potential cobalt carriers (FBXL2, ZNT1, SLC12A5), tumor suppressors or transcription factors (MAZ, DLG1, MYC, AXL) and genes linked to the stress response (UBC, HSPCB, BNIP3L). We also identified nine genes coding for secreted proteins as candidates for biomarker research. Of those, TIMP2 was found to be down-regulated and this modulation was confirmed, in a dose-dependent manner, at protein level in the supernatant of exposed cells.

CONCLUSION

Most of these genes have never been described as related to cobalt stress and provide original hypotheses for further study of the effects of this metal ion on human lung epithelial cells. A putative biomarker of cobalt toxicity was identified.

Effect of cobalt ions on the metabolism of some volatile and polar compounds in the marine invertebrates Mytilus galloprovincialis and Actinia equina

The compositions of the volatile and polar fractions from two coexisting Black Sea invertebrates, the mussel Mytilus galloprovincialis and the beadlet anemone Actinia equina, were established. The main metabolites in the volatile fraction from the investigated animals appeared to be methyl esters of fatty acids and fatty aldehydes. In the polar fraction from both animals low concentrations of free acids and nitrogen-containing compounds were obtained. Free carbohydrates were in much higher concentrations in M. galloprovincialis than in A. equina. Some sterols, probably as polar conjugates, were identified mainly in A. equina. Significant changes among all compounds appeared after treatment of both invertebrates with two different concentrations of cobalt ions. The variety of changes in each invertebrate could be due to their different evolutionary status. The effect of cobalt ions was often stronger at medium cobalt-ion concentrations.

Cobalt release from glazed earthenware: Observations in a case of lead poisoning

In a case of lead poisoning caused by a Greek jug, high levels of whole blood cobalt were also recorded. Cobalt was probably released from the underglaze dye by juice stored in the jug. The element was rapidly eliminated from the circulation and no signs of cardiotoxicity were observed in the patient. This case illustrates a possibly novel route of alimentary cobalt exposure.

Effect of cobalt ions on lipid and sterol metabolism in the marine invertebrates Mytilus galloprovincialis and Actinia equina

The lipid and sterol fractions of the mussel Mytilus galloprovincialis and the anemone Actinia equina were analyzed before and after incubation with cobalt ions. There were significant changes in the lipid and sterol composition, strongly depending on the cobalt ions concentrations. The changes in the lipid composition of both invertebrates were different for neutral lipids and phospholipids. These changes concern the length of the fatty acid chains as well as their unsaturation. The cobalt ions inhibited the oxidation of sterols and their alkylation at C-24. Because of these results we can assume that some of the changes caused by cobalt ions might possess adaptive value.

Toxicological evaluation and metal bioavailability in pregnant rats following exposure to clay minerals in the diet

Silicate clays are frequently added to animal feeds to bind and reduce the bioavailability of mycotoxins in the gastrointestinal tract. However, the bioavailability of trace metals in these clay feed additives has not been thoroughly investigated. Clays that act nonselectively may interact with nutrients, minerals, and other feedborne chemicals to pose significant hidden risks. In this study, a calcium montmorillonite clay (Novasil Plus, NSP) commonly used as an enterosorbent for aflatoxins and a sodium montmorillonite clay (Swy-2) (Source Clay Minerals Repository, Columbia, MO) were examined. Clays were supplemented in the balanced diet of Sprague-Dawley rats during pregnancy at a level of 2% (w/w). Evaluations of toxicity were performed on gestation d 16 and included maternal body weights, maternal feed intakes, litter weights, and embryonic resorptions. Liver, kidneys, tibia, brain, uterus, pooled placentas, and pooled embryonic mass were collected and weighed. Tissues were lyophilized and neutron activation analysis (NAA) was performed. Elements considered by NAA included Al, Ba, Br, Ca, Ce, Co, Cr, Cs, Cu, Dy, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Ni, Rb, S, Sb, Sc, Se, Sm, Sr, Ta, Tb, Te, Th, Ti, Tl, U, V, Yb, Zn, and Zr. Inductively coupled plasma-mass spectroscopy further confirmed that Al was below detection limits (<0.5 ppm) in the brain. Animals supplemented with either NSP or Swy-2 were similar to controls with respect to toxicity evaluations and metal analysis, with the exception of decreased brain Rb following clay supplementation. Overall, the results of this study suggest that neither NSP nor Swy-2, at relatively high dietary concentrations, influences mineral uptake or utilization in the pregnant rat.

Characterization of hard metal dusts from sintering and detonation coating processes and comparative hydroxyl radical production

Dust samples from sintering and detonation coating hard-metal processes were characterized, compared, and contrasted for morphology, composition, and generation of hydroxyl radicals. Inhalation of respirable hard-metal (sintered carbide) dusts from hard-metal processes is known to cause fibrotic and asthmatic lung disease. Scanning electron microscopy/energy-dispersive X-ray analysis was used for morphology, composition, and elemental distribution. An electron spin resonance (ESR) spin trapping technique was used to detect hydroxyl radical generation. Samples were incubated with air-saturated buffer solutions containing a spin trap and analyzed by ESR for the presence of *OH in solution. Postdetonation coating samples often had surface contamination of Co on the WC particles, as shown by elemental mapping of individual particles; this was not evident in predetonation samples or unsintered materials in this study. ESR measurements show that both detonation-gun materials were capable of generating *OH , while the WC, cobalt, and presintered mixture did not produce detectable amounts of *OH radicals. The DMPO/*OH adduct formation was apparently facilitated by Fe-mediated reactions for predetonation dusts, and by Fe-mediated site-specific reactions for postdetonation dusts. The overspray materials from the detonation-gun process produced 9-fold more *OH radicals than the predetonation coating mixture. Overall, this study indicates there are substantial differences between postdetonation materials and both predetonation and unsintered hard-metal process materials with respect to morphology, elemental distribution, and *OH radical generation reactions and that these differences may be important in the toxic potential of those materials.

Cobalt

Cobalt is a relatively rare magnetic element with properties similar to iron and nickel. The two valance states are cobaltous (II) and cobaltic (III) and the former is the most common valance used in the chemical industry. Cobalt occurs in nature primarily as arsenides, oxides, and sulfides. Most of the production of cobalt involves the metallic form used in the formation of cobalt superalloys. The term "hard metal" refers to compounds containing tungsten carbide (80-95%) combined with matrices formed from cobalt (5-20%) and nickel (0-5%). For the general population, the diet is the main source of exposure to cobalt. In the occupational setting, exposure to cobalt alone occurs primarily during the production of cobalt powders. In other industrial exposures (e.g., hard metal, diamond polishing), additional agents (tungsten) modulate the toxicity of cobalt. Cobalt is an essential element necessary for the formation of vitamin B12 (hydroxocobalamin); however, excessive administration of this trace element produces goiter and reduced thyroid activity. In 1966, the syndrome "beer drinker's cardiomyopathy" appeared in Quebec City, Canada, and was characterized by pericardial effusion, elevated hemoglobin concentrations, and congestive heart failure. An interstitial pulmonary fibrosis has been associated with industrial exposure to hard metal dust (tungsten and cobalt), but not to cobalt alone. Exposure to cobalt alone produces an allergic contact dermatitis and occupational asthma. Treatment of cobalt toxicity is primarily supportive.

Human toxicity of cobalt-containing dust and experimental studies on the mechanism of interstitial lung disease (hard metal disease)

In the industry, the potential for exposure to cobalt metal dust is particularly important during the production of cobalt powder and the processing and use of hard metals and other cobalt-containing alloys. The different adverse health effects reported in these workers are reviewed. One of the main target organs is the respiratory tract, and this article concentrates on the lung parenchymal reactions induced by cobalt-containing dust. Clinical and epidemiological data indicate that this manifestation is rarely, if ever, induced by pure cobalt metal dust alone, but requires the concomitant inhalation of other compounds such as tungsten carbide in the hard metal industry (hard metal disease). Experimental studies demonstrate that cobalt metal and metallic carbides interact to produce an elective lung toxicity. Recent work on the mechanism of this interaction, which is based on the production of activated oxygen species, is reviewed. A practical implication in industrial hygiene should be that permissible exposure levels to Co dust might have to be different when exposure is to pure Co particles or an association with carbides.

An analytical comparison of cobalt cardiomyopathy and idiopathic dilated cardiomyopathy

Toxic cardiomyopathy (TC) has a rapid clinical course and morphologically resembles idiopathic dilated cardiomyopathy (IDC). To further characterize TC, we used light microscopy to compare lesions caused by cobalt (Co) to those of IDC. Cobalt levels were also measured as a chemical marker to differentiate TC from IDC. We reviewed cases with TC and IDC and excluded all cases with chemotherapy-induced myopathy and catecholamine toxicity as well as cases with possible infectious, ischemic, or hypersensitivity-induced myopathies. We compared the light microscopic findings of 12 TC cases of 12 cases of IDC, and measured trace Co levels on digested heart tissue samples. The TC cases had prominent myofibrillar loss and atrophy; no cases had neutrophil infiltration or frank myocyte necrosis. In contrast, IDC had minimal myofibril loss and atrophy. Cobalt levels in the range of 0.6 to 5.45 micrograms/g of dry tissue were obtained for the TC cases, while IDC demonstrated Co levels of 0.01-0.2 micrograms/g. Distinction between TC and IDC is predominantly a function of myocyte change, with TC showing myofibrillar loss and atrophy in the absence of inflammatory infiltrates and fibrosis; IDC is predominantly associated with myocyte hypertrophy, atrophy, and fibrosis.

Cardiomyopathies and oxidative stress

Cardiomyopathies are the group of diseases affecting the cardiac muscle. Although they have never been related to oxidative stress diseases, an analysis of the causes of these pathologies reveals the presence of a pro-oxidative agent or that the intracardiocytic balance between oxidation and antioxidation has been broken. In support of this hypothesis, we analyse the pro-oxidative factors which co-operate with other factors or by themselves to promote the development of this group of pathologies. We show also data demonstrating that the tissue and cellular damages are characteristic of an oxidative stress situation. Finally, we present evidence that in some cases of particular cardiomyopathies, the use of antioxidative strategies greatly improves the health of the patients. Therefore, we suggest that the use of antioxidants can be an alternative or complementary therapy in this group of diseases.

Physiological and toxicological changes in the skin resulting from the action and interaction of metal ions

The human environment contains more than 50 metal or metalloid elements. At least 15 are recognized as trace elements, with zinc, calcium, copper, magnesium, and iron having specific roles in skin morphogenesis and function. The present review focuses on the presumed role of metal ions in the skin, their competition for carrier proteins, and membrane receptors. Evidence presented shows that the balance of trace metal ions is critical for normal skin and repair mechanisms following injury. Xenobiotic ions can impair this balance, leading to pathological change. The skin acts as an organ of elimination of excess trace metals and xenobiotic ions from the body, but mechanisms of voidance vary for different metals. Metal ions are an important cause of allergies, and evidence is presented to show that the majority of metals or metal compounds can induce allergic changes. Except for chromium and nickel, which are among the most common human allergens, animal models have provided little information. At least cadmium, thorium, lead, chromium, nickel, beryllium, and arsenic and proven or putative carcinogens in animals or humans on the basis of cytological or epidemiological evidence. However, only arsenic exhibits a clear predilection for the skin. Other metals such as gold can induce subcutaneous sarcoma following injection, but the relevance of this observation in terms of human occupational risk is discounted.

Cobalt myocardiopathy. A critical review of literature

Cobalt is regarded as being responsible for a form of myocardiopathy whose pathogenesis and clinical description must still find a specific place in the range of congestive myocardiopathies. In spite of this, epidemiological studies are not sufficient to prove the role of cobalt in inducing myocardiopathy in hard metal workers. This critical review intends to evaluate if hard metal exposure may induce toxic effects on the heart. In this context, the literature considered ranges from pioneer reports on 'beer drinkers' to the more recent papers concerning cases of patients occupationally exposed; subjects who, after a surgical operation died of fulminant heart failure and, lastly, hard metal workers who were examined for their cardiac function. Various pathogenetic mechanisms related to possible cardiac effects in hard metal workers have been analyzed. The most likely should be the inhibition of cellular respiration due to inhibition of the mitochondrial dehydrogenase.

Assessment of risks in occupational cobalt exposures

Exposure to cobalt can give rise to adverse health effects related to various organs or tissues, such as the respiratory organs, the skin, the hematopoietic tissues, the myocardium, the thyroid gland, as well as teratogenic and carcinogenic effects. In occupational and environmental health, it is important to identify effects that occur at relatively low exposure, i.e. the critical effects which are crucial for preventive action. The limited database available on cobalt toxicity makes it difficult to select critical effects. For dermal exposures, allergic dermatitis may be regarded as such an effect, even if this is a reversible condition and dose-response relationships need to be defined. For inhalation exposures, effects on the respiratory tract can be considered as critical effects. Evidence of cobalt carcinogenicity in humans is inadequate and cannot be evaluated quantitatively but an extra safety factor to be added on exposures estimated from other effects may well be needed. Risks for development of pneumoconiosis are likely to be dependent on physical and chemical characteristics of airborne cobalt containing particles, but such information is lacking in most studies. It has been recognised for many years that there is an excess risk of pneumoconiosis when exposure to cobalt containing dust exceeds 100 micrograms/m3. Recently considerably lower concentrations occurring in the cobalt diamond industry have given rise to such effects. Irritation of mucous membranes may occur at 5-10 micrograms/m3.

A 1982-1992 surveillance programme on Danish pottery painters. Biological levels and health effects following exposure to soluble or insoluble cobalt compounds in cobalt blue dyes

This paper provides a short overview of cobalt-related diseases with particular reference to the potential carcinogenicity of cobalt compounds, and a review of a 10-year surveillance programme on plate painters exposed to cobalt in two Danish porcelain factories. Clinical experience and epidemiological studies have demonstrated that cobalt exposure may lead to severely impaired lung function, i.e. hard metal lung disease and occupational cobalt-related asthma, contact dermatitis and cardiovascular effects. However, the evidence for the carcinogenicity of cobalt and cobalt compounds is considered inadequate (IARC, 1991). Most frequently, exposure to cobalt occurs simultaneously with exposure to other elements known to pose a health risk, (e.g. nickel, arsenic, chromium, tungsten). The importance of cobalt as sole causal agent in hard metal lung diseases, cardiomyopathy and cancer are still a matter of controversy. In the two Danish porcelain factories, cobalt blue underglaze dyes have been used since 1888. In contrast to the exposure experience of hard metal factories, the exposure of plate painters occurs with only low trace levels of other potentially harmful compounds such as the carcinogenic metals nickel, arsenic and chromium. Consequently, the nearly-pure cobalt exposure makes the plate painters an attractive group for studies on the health effects of cobalt. During the period 1982-1992 the surveillance programme showed a profound reduction in the urine level of cobalt (Co-U) from 100-fold to 10-fold above the median level of the unexposed control subjects. In the same period, the airborne cobalt exposure declined from 1356 nmol/m3 to 454 nmol/m3, the Danish occupational exposure limit being 845 nmol/m3. In 1982, when the cobalt exposure was above the occupational exposure limit, the plate painters showed a chronic impaired lung function. The obstructive effects may be similar to some of the effects observed in hard metal workers. In 1988, a study on the effect of cobalt exposure at low levels revealed no inhibitory effects on thyroid function, but the ratio between T4 and T3 increased, indicating that low cobalt exposure may have an impact on the metabolism of thyroid hormones. Parallel studies were conducted on the metabolism and excretion of cobalt. The gastrointestinal uptake of soluble CoCl was considerably higher than the uptake of insoluble cobalt(II) oxide. In addition, it was demonstrated that ingestion of controlled amounts of the soluble cobalt compound resulted in significantly higher concentrations of cobalt in urine and blood (Co-B) from females compared with males (P < 0.01). Future studies will involve epidemiology and genotoxicity to evaluate the previous and present cancer risk, and detailed process-related exposure assessment studies to select the methods most reliable for surveillance of low-dose cobalt exposure.

Cardiac function study in hard metal workers

The induction of cardiac effects in hard metal workers is uncertain. This study investigates cardiac function of a group of 31 hard metal workers with or without pulmonary disease. The average duration of exposure to cobalt containing dusts was 10.4 years (range 1-30), while the environmental levels of cobalt exposure ranged from 0.09 to 13.6 mg/m3 Co. Cardiac function has been studied by: ECG (electrocardiogram), exercise test (ET), ECG 24 h according to Holter (ECGH), echocardiogram (ECHO) and radionuclide angiocardiography with 99Tc (RNA). The aims of this work were (i) to show the existence of cobalt myocardiopathy in the workers analyzed and, (ii) to find an early indicator of cardiac dysfunction which could be used in the clinical examination of hard metal workers. Within the group of patients with hard metal lung disease, cases of myocardiopathy of doubtful aetiology have been found. The cardiac indexes obtained through RNA show ventricular dysfunction in healthy hard metal workers which could be a manifestation of initial pulmonary artery hypertension or of an early occult cor pulmonale due to an unknown fibrotic lung disease.

Acute cobalt exposure and oxygen radical scavengers in the rat myocardium

Excessive amounts of cobalt are cardiotoxic, although the mechanism for this toxicity remains unclear. We studied the effects of acute cobalt exposure on the activities of free radical scavengers in the myocardium in 5 groups of rats. Six rats served as a control group and were given a daily subcutaneous injection of 1 ml saline for 8 days. The other 4 groups of rats received a daily injection subcutaneously of cobalt chloride in doses of 1 mg/kg bw, 5 mg/kg bw, 20 mg/kg bw and 50 mg/kg bw, respectively for 8 days. There was a marked and dose-dependent accumulation of cobalt in the myocardium of the cobalt exposed rats. Creatine kinase, copper-zinc superoxide dismutase (CuZn-SOD) and alpha-tocopherol content did not differ between the control and the cobalt exposed groups. The activity of glutathione peroxidase increased, while the activity of manganese-superoxide dismutase (Mn-SOD) was significantly reduced in the cobalt exposed groups. There was an inverse relationship (r = 0.60, P < 0.0001) between the cobalt content and Mn-SOD activity in the myocardium. These results suggest that acute cobalt cardiotoxicity may involve a reduction of intrinsic scavengers resulting in an increased vulnerability to oxygen free radical toxicity.

Determination of cobalt in urine by gas chromatography-mass spectrometry employing nickel as an internal standard

A gas chromatographic-mass spectrometric method for the determination of cobalt in biological materials employing stable enriched 62Ni as an internal standard and using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described. The method involves the addition of a known amount (1 microgram) of 62Ni to the sample, the formation of the chelate and the determination by selected-ion monitoring of the m/z 571/574 ratio, which corresponds to 59Co/62Ni. No appreciable memory effect was observed, and an acceptable dynamic range of 100 was found. There was good agreement between the cobalt concentration values determined by gas chromatography-mass spectrometry and electrothermal atomic absorption spectrometry. The present method has high sensitivity and can be used for the quantitation of cobalt at concentrations as low as 1 microgram/l. The use of enriched 62Ni circumvents the problem caused by endogenous nickel and simultaneously provides data on the nickel concentration in the biological sample without any additional experimental effort.

Binding of dietary cobalt to sarcoplasmic reticulum proteins

It has previously been shown that cobalt accumulates in the myocardium of rats, mainly the sarcoplasmic reticulum (SR) and the mitochondrial inner membrane. In order to investigate the mode of accumulation of cobalt in the SR, rats were given a dietary cobalt supplementation of 40 mg of CoSO4 x 7H2O kg-1 body wt, after which the rats were sacrificed and the sarcoplasmic reticulum was isolated. The SR proteins were subjected to analysis by polyacrylamide gel electrophoresis followed by protein staining and determination of the content of cobalt in each protein band. The major cobalt-binding protein was found to have a molecular weight of about 100,000; a 200,000 molecular weight protein was also found to bind cobalt, although less extensively. These results suggest that cobalt is bound to the monomeric and dimeric forms of Ca(2+)-ATPase in the SR of the myocardium.

Alcohol-related cardiomyopathy in the Seychelles

OBJECTIVE

To determine the frequency and features of alcohol-related cardiomyopathy in the Seychelles.

DESIGN AND SUBJECTS

The study was multifaceted investigation involving: a randomised cross-sectional survey of drinking habits in the general population; a cross-sectional survey of blood alcohol levels in patients admitted to hospital; a prospective case series of all consecutive patients hospitalised with alcohol-related cardiomyopathy; a retrospective review of medical records; and an analysis of volatile oils and trace metals in alcoholic drinks.

SETTING

Data on drinking habits were obtained from a randomised sample of 1309 adults from the total population of the Seychelles (66,000). All clinical data were obtained from patients in the Victoria Hospital, which is the single reference hospital of the country.

INTERVENTION

Hospitalised patients with alcohol-related cardiomyopathy were treated initially with vitamin B1 and/or diuretics.

RESULTS

The survey of alcohol habits revealed that 75% of the male population were regular alcohol consumers, with 19% of men consuming more than 100 g of alcohol per day. The estimated annual consumption of alcohol per capita was 26.4 L for men and 3.5 L for women. The survey of blood alcohol levels showed that 28% of male and 13% of female patients had raised alcohol levels at hospital admission. Throughout 1989, 96 patients were diagnosed as having alcohol-related cardiomyopathy and 12 of these had beriberi. The majority of young patients responded with marked diuresis within four hours of a single administration of thiamine. Overall, one-third of all male medical admissions were due to alcohol-related disease. The pathological effects of alcohol consumption were detected in 47% of autopsies and in 20% there was evidence of alcohol-related cardiomyopathy.

CONCLUSIONS

These findings confirm the high frequency of alcohol-related disease in general and cardiomyopathy in particular.

The intracellular distribution of cobalt in exposed and unexposed rat myocardium

The intracellular distribution of cobalt was analysed in the myocardium of exposed and unexposed rats. The exposed rats were given a dietary cobalt supplementation of 40 mg CoSO4.7 H2O/kg body weight for 8 weeks. The mitochondrial fraction showed the greatest relative increase in cobalt: 0.09 ng/mg protein in the unexposed rats to 8.43 ng/mg protein in the exposed rats. In the exposed rats the submitochondrial particles had the highest levels of cobalt: 19.43 ng/mg protein, followed by the sarcoplasmatic reticulum: 12.3 ng/mg protein. The microsomal 44,000 g supernatant also showed an increase, although the levels remained low (0.51 ng/mg protein in the exposed animals). Apparently the calcium-storing organelles had the highest levels of cobalt. This could affect calcium flux in myocardial cells and, secondarily, tension development in cardiac muscle.

The effect of cobalt on mitochondrial ATP-production in the rat myocardium and skeletal muscle

Cobalt has been shown to accumulate in the myocardium of uraemic patients and has been suggested as a myocardial toxin inhibiting mitochondrial respiration. In order to study the cellular effects of cobalt exposure three groups of rats (n = 12 per group) were fed a diet containing 12% protein without supplementation or with 20 mg and 40 mg CoSO4 7 H2O/kg body weight/day respectively. After 8 weeks the hearts and soleus muscles were removed. Cobalt in tissues and in four cell fractions were analysed with neutron-activation analysis (ng/g wet weight and ng/mg protein respectively). Mitochondrial respiration was analysed as ATP-production rate using pyruvate + malate and palmitoyl-carnitine + malate as substrate. The ATP-production from pyruvate + malate was unchanged in both heart and skeletal muscle in the exposed animals. With palmitate as substrate, the heart muscle showed a slightly lower ATP-production rate (p less than 0.05) after the 20 mg cobalt dose, but the rate was unchanged in the group with higher cobalt intake. No changes in ATP-production rate from palmitate was observed in soleus muscle. The microsomal (100,000 g) fraction in the myocardial cells contained significantly higher cobalt concentrations compared to the mitochondrial fraction in both the unexposed (1.4 ng/mg protein vs 0.19, p less than 0.05) and exposed rats (53.4 ng/mg protein vs 13.2, p less than 0.005). In conclusion, cobalt showed a large accumulation in myocardial cells, without significant effects on mitochondrial ATP-formation rate from oxidation of pyruvate or palmitate and with the highest cobalt content contained in the microsomal (100,000 g) fraction.

A comparison of cobalt(II) and iron(II) hydroxyl and superoxide free radical formation

We have employed the electron spin resonance spin-trapping technique to study the reaction of Co(II) with hydrogen peroxide in a chemical system and in a microsomal system. In both cases, we employed the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and were able to detect the formation of DMPO/.OH and DMPO/.OOH. DMPO/.OOH was the predominant radical adduct formed in the chemical system, while the two adducts were of similar concentrations in the microsomal system. The formation of both of these adducts in either reaction system was inhibited by the addition of superoxide dismutase or catalase, and by chelating the cobalt with either ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). The incorporation of the hydroxyl radical scavengers ethanol, formate, benzoate, or mannitol inhibited the formation of DMPO/.OH in both systems. We also repeated the study using Fe(II) in place of Co(II). In contrast to the Co(II) results, Fe(II) reacted with hydrogen peroxide to yield only DMPO/.OH, and this adduct formation was relatively insensitive to the presence of added superoxide dismutase. In addition, Fe(II)-mediated DMPO/.OH formation increased when the iron was chelated to either EDTA or DTPA rather than being inhibited as for Co(II). Thus, we propose that Co(II) does not react with hydrogen peroxide by the classical Fenton reaction at physiological pH values.

Cobalt in the environment and its toxicological implications

Cobalt is an essential trace element which is widely distributed in nature. Most of cobalt consumed is used in the manufacture of alloys, and although not released extensively in the environment, it may represent a hazard to human health. In addition, excess dietary cobalt produces toxic effects in animals. Polycythemia and hyperglycemia with transitory damage to pancreatic alpha-cells have been widely reported after cobalt administration. Cobalt salts induce respiratory deficiency in yeast. CoCl2 increased sister chromatid exchange (SCE) in P388D1 cells and in lymphocytes from two donors. So far it has not been possible to induce cancer in experimental animals using cobalt by any other route than by injection. Ingestion of cobalt may lead to reproductive changes in the male rat such as loss of testicular volume and darkening of testicle color. On the other hand, oral administration of cobalt did not produce teratogenicity or significant fetotoxicity in the rat at daily doses as high as 100 mg CoCl2/kg. However, cobalt affected the period of late gestation as well as the postnatal development of the pups. Occupational toxicology of cobalt, hygienic and epidemiologic aspects, and treatment of cobalt poisoning are also topics of special interest. Cobalt is a metal with marked allergenic potential. Asthma, interstitial lung disease and combined asthma and alveolitis have been described as occupational health hazards. EDTA, DTPA, and N-acetyl-L-cysteine have been suggested as possible antidotes in cobalt intoxication.

The organ distribution of liposome-encapsulated and free cobalt in rats. Liposomes decrease the cardiac uptake of the metal

Rats were administered intravenously liposome-encapsulated or free cobalt, and the organ distribution of the metal was explored using Co57 tracer. Two hours after administration, the cobalt level in the heart was about 40% of the control when given in sphingomyelin (SM)/cholesterol (CH) (1:1 mole ratio) liposomes. These vesicles also tended to decrease the uptake of cobalt in the kidney and the carcass, and to increase it in the spleen and the bones. Liposomes prepared from soybean phosphatidylcholine (SPC)/CH (1:1) had no effect on the uptake of cobalt in the heart, whereas increased its level in the spleen, liver and lung. The time-course of cobalt deposition in the organs displayed substantial variation with the different preparations. Most importantly, no buildup of cobalt level was observed in the heart when the metal was administered in SM/CH vesicles. While confirming known effects of liposomes on the organ-distribution of entrapped drugs, our findings suggest that administration of cobalt in SM/CH liposome-encapsulated form may result in decreased cardiotoxicity and thus increased safety of cobalt-treatment in some anemias.

Blood and urinary concentrations as estimators of cobalt exposure

Methods for determining low levels of cobalt in blood and urine within a normal range have been developed. Mineralizing by using small amounts of nitric acid, ion exchange separation, and electrothermal atomic absorption measurements are the techniques used. The normal content of cobalt is 8.5 nmol/L (range 1.7-20.4 nmol/L) in blood and 6.8 nmol/L (range 1.7-37.3 nmol/L) in urine in a nonoccupational cobalt-exposed group. After exposure, cobalt is excreted rapidly in urine. When exposure is relatively high, there is rapid continuous decrease in excretion for about 24 hr followed by a slower excretion phase. When exposure is low, the excretion of cobalt in urine is relatively constant but may be 4-10 times higher than in non-exposed persons. The slow excretion can continue at least 4 wk after exposure. Variations of cobalt concentrations in blood are smaller but follow the exposure. When blood and urine concentrations of cobalt were compared on a Friday afternoon, the correlation coefficient was 0.82. When the average exposure to cobalt for the whole week was compared with the cobalt concentration in urine, the correlation coefficient on Friday afternoon was 0.79 and on Monday morning 0.81. For blood, the correlation coefficient was 0.87 on Friday afternoon and 0.76 on Monday morning.

Developmental toxicity of cobalt in the rat

To determine the potential developmental toxicity of cobalt, pregnant Sprague-Dawley rats were given by gavage a daily dose of 0, 25, 50; and 100 mg/kg cobalt(II) chloride on d 6-15 of gestation. Females were sacrificed on d 20. Maternal effects included significant reductions in weight gain and food consumption, particularly at 100 mk/kg.d. Hematocrit, hemoglobin concentration, mean corpuscular volume, mean corpuscular hemoglobin, and reticulocytes were increased significantly in the 100-mg/kg.d group. No treatment-related changes were recorded in the number of corpora lutea, total implants, resorptions, the number of live and dead fetuses, fetal size parameters, or fetal sex distribution data. Increased incidence of stunted fetuses per litter was the only adverse finding at 50 and 100 mg/kg.d group. However, this increase was not statistically significant. Examination of fetuses for gross external abnormalities, skeletal malformations, or ossification variations revealed that cobalt did not produce teratogenicity or significant fetotoxicity in the rat at doses as high as 100 mg/kg.d.