Metal determinations in biological specimens of diseased and non-diseased hard metal workers

Biological monitoring of Co, Ta and W, using mainly neutron activation analysis, was carried out on the urine, blood, pubic hair and toe nails of 251 subjects occupationally exposed to hard metal dusts (23 individuals were diagnosed as ‘diseased subjects’, affected by asthma and/or lung fibrosis). Airborne dust at hard metal workplaces were also analyzed for Co and W content. Cobalt and tungsten exposure at workplaces varied widely and frequently exceeded the TLV (0.05 mg Co/m³). Cobalt in urine (CoU), which is better than Co in blood (CoB), could represent a valuable indicator in discriminating between exposed groups, but is of little value as an indicator of exposure for single individuals. The high concentrations of cobalt in pubic hair (CoH) and toe nails (CoN) could also be valuable indicators of exposure although they are not useful, however, in establishing quantitatively the levels of cobalt accumulation. Tungsten and tantalum in pubic hair (WH and TaH) and toe nails (WN and TaN) also seem to be useful indicators in proving hard metal exposure qualitatively. The determination of these two elements, rather than cobalt, in the bronchoalveolar lavage (BAL) is very useful in complementing the diagnosis of hard metal disease proving hard metal exposure. The analysis of the BAL subfractions showed that W and Ta were firmly incorporated into the macrophage fraction while Co was distributed between cellular fraction and supernatant, which suggests a different mobility of hard metals in pulmonary tissue. The metal concentrations determined when submitted to statistical analysis indicated a positive correlation with P < 0.001 for the pairs (CoB---CoU), (Co---W) in urine, and (Co---W) in toe nails. Multielement analysis of biological specimens from diseased subjects suggests that hard metal disease does not relate to Co, W and Ta levels in the specimens considered. The disease does not depend on sex, age, working age and length of hard metal exposure. These findings support the theory on the possible haptenic properties of Co which may induce hypersensitivity and immuno-related toxic effects.     

Hard metal lung disorders: analysis of a group of exposed workers

The experience gained during the last 5 years in the study of 36 male workers exposed to hard metal dusts (10 engaged in mixing, 12 in presintering, three in sintering and 11 in grinding) is presented. The mean age was 33.2 years (S.D., 11.8) and the mean number of years of exposure was 9.4 (S.D., 7.6). All subjects received a physical examination, chest X-rays, pulmonary function test (VC, FEV₁, expiratory flows, RV, DLco, and metacholine bronchial provocation test), skin tests, brochoalveolar lavage (BAL) and determination of trace metals in BAL, blood, uring, pubic hair and toe nails. Two cases of bronchial asthma, six cases of interstitial lung disease and one case with both disorders were identified; eight of these cases presented at BAL signs of alveolitis with different cytologic features. Among the other 27 asymptomatic subjects, two showed an aspecific bronchial hyperreactivity, four showed a reduced DLco, 12 showed an inverted ratio of CD4/CD8 lymphocytes in BAL without signs of alveolitis while one subject presented both an aspecific bronchial reactivity and a reduced DLco. The presence of aspecific bronchial hyperreactivity in asymptomatic subjects might represent a preclinal indicator of a possible evolution towards bronchial asthma. An altered DLco, alone or associated with an inverted CD4/CD8 ratio of BAL lymphocytes, might constitute an early sign of a possible evolution towards interstitial lung disease. The association of aspecific bronchial reactivity and reduced DLco might indicate the possible evolution towards a mixed form. Only to follow up of these subjects might confirm or exclude these hypotheses. The nine symptomatic subjects have been followed up in time; three have continued their job in better hygienic conditions, six have completely discontinued the exposure; five were treated with corticosteroids. The clinical evolution of both asthma and interstitial diseasehas been variable and poorly influenced by changed working conditions and steroid treatment (two cases improved, two worsened, and five remained stationary). In consideration of the possible evolution of hard metal disorders towards a respiratory insufficiency and because of the unpredictable and questionable response to treatment, a thorough periodical surveillance of the exposed seems necessary in order to make early diagnoses in those still in an asymptomatic phase.     

On the potential of combining neutron activation analysis and particle induced X-ray emission (PIXE) for micro- and microdistribution analysis of hard metals in human tissues

Tungsten carbide and cobalt are the main components of hard metal alloy while other metals such as chromium, niobium, tantalum, titanium and vanadium are sometimes added in smaller amounts. Exposure to hard metal dusts can induce a lung fibrosis with cobalt playing a major role. In order to provide information on the role that each metal may have in causing this disease, determination of the total content and the distribution of inhaled metals in lung tissue of hard metal workers is of paramount importance. However, samples such as transbronchial biopsy and bronchoalveolar lavage (BAL), often used in the medical diagnosis of pneumoconiosis, only allow for a small amount of material. This calls for sensitive and accurate analytical procedures for microdetermination and distribution of metals in pulmonary tissue and cellular material, such as macrophages. This work proposes a combination of sophisticated analytical techniques such as neutron activation analysis (NAA), currently applied to the determination of the total concentration of more than 30 elements in biological specimens, and PIXE analysis, particularly microPIXE, which has a great potential for microdistribution analysis in small biological samples. Principles and perspectives for the combined use of these techniques for the analysis of human tissue are outlined and discussed. NAA: determination of hard metals in lung tissue are carried out by neutron irradiation (2 × 10¹⁴ neutrons cm⁻² s⁻¹) in the HFR reactor of Petten. After neutron activation, radiochemical separations of ⁶⁰Co, ¹⁸⁷W, ¹⁸²Ta, ⁵¹Cr followed by computer-based high resolution gamma ray spectrometry allow the measurement of these elements in pulmonary tissues with sensitivities ranging from 10⁻⁴ μg (Cr) to 10⁻⁶ μg (W). PIXE: this technique is multielemental and of relatively high sensitivity (μg/g) even in small total sample masses of from 10 to 100 μg, thus allowing the analysis of parts of needle biopsies. Whereas PIXE has been successfully applied to many medical problems, its usefulness is limited in the total samples analysis for cobalt-related hard metal disease, due to the low levels of cobalt in tissue combined with severe element interferences from the generally more abundant metal, iron. Nevertheless, microPIXE, a special variety of the method scanning over the sample with a focussed ion beam of about 2 × 2 μm², could complement the NAA findings in total samples in the sense of achieving a microdistribution analysis of hard metals (including cobalt) in suitable thin tissue sections.The availability of specialized facilities at the JRC such as the powerful HFR reactor (Petten), the NAA laboratories (Ispra) and the microPIXE facility (Geel) could represent a European ‘reference pole’ for the study of metals in tissues of hard metal diseased subjects.     

Chromium, cobalt and lanthanum in lung, liver and kidney tissue from deceased smelter workers

Lung, liver and kidney tissue concentrations of chromium, cobalt and lanthanum from 66 deceased copper smelter workers have been compared with 14 controls. Samples were taken in connection with ordinary autopsies at the local hospital. Neutron activation analysis was used. The mean exposure time for the smelter workers was 30 y, the mean time to date of death after termination of exposure was 7.4 y. A four-fold increase of chromium (p = 0.001) and a two-fold increase of cobalt (p less than 0.001) and lanthanum (p = 0.013) in lung tissue was found for smelter workers compared to controls. Of the smelters nearly one third died from malignancies (approximately 10% from respiratory cancer) and approximately 45% from cardiovascular disease. In the control group nearly 80% died from cardiovascular diseases and no malignancies were found. In lung tissues the concentration of chromium, cobalt and lanthanum did not decline with time after exposure had ended, indicating a long biological half-time. The causes of death could not be related to a single factor. The findings indicate a multifactorial genesis.     

Cobalt excretion in urine: results of a study on workers producing diamond grinding tools and on a control group

A study was carried out on cobalt (Co) excretion in the urine of 12 workers exposed to known cobalt concentrations in the stone cutting diamond wheel production and in six volunteers: four of these were exposed in the same work environment for a whole workshift and the other two were exposed to cobalt in a cabin under experimental conditions. The kinetics of the urinary excretion was multiphase: (i) a first stage of rapid elimination ( ); (ii) a second phase of slower elimination ( ); (iii) a longer period of retention, of the order of years, in subjects with higher exposure. In the control group (4 subjects), the excretion proved to be much faster in the first stage ( h). The different behaviour of the two groups could be related to the different body burden, of cobalt and/or to the possibility of different kinetics induced by continuous exposure to the metal. Moreover, 3 weeks after the removal of the workers from exposure the urinary cobalt concentrations were not within the normal limits of CoU for the general population, (even for workers exposed to cobalt levels of the same order as the TLV). The increase of CoU concentrations in the first 3 h after the end of exposure, stresses the problem of when urine samples for biological monitoring of the workers should be collected. The present study confirms the utility of CoU in discriminating between exposed and non-exposed subjects as well as in assessing high and low level exposure.     

Hard metal disease: clinical aspects

On the basis of the data available in the literature and of our experience, the clinical patterns of respiratory troubles which can be observed in workers exposed to inhalation of hard metal dusts can be schematized as follows: Irritation forms, mild and transient, or severe up to pulmonary oedema, dose-correlated, which occur in all subjects exposed to sufficiently high atmospheric concentrations; Asthmatic factors, either reversible after cessation of exposure or persistent after stopping the exposure, which occur in a relatively low percentage of exposed subjects and also apply to the states quoted below; Dyspnoic patterns due to alveolitis (lymphocytic alveolitis with inverted helper/suppressor ratio, or giant cell-eosinophilic alveolitis, with or without fibrotic changes of pulmonary interstitium); Interstitial sclerotics lung disease, associated with or without an alveolitic component. The present diagnostic potentialities, particularly bronchoalveolar lavage (BAL), have helped in defining the clinical patterns and have confirmed the fundamental role of individual susceptibility in the occurrence of clinical manifestations (with the exception of the irritation forms), but so far have not yet enabled us to clarify whether the different clinical patterns are the results of a single pathogenetic mechanism or constitute pathogenetically distinct entities.     

A combined ecological and epidemiologic investigation of metal exposures amongst Indigenous peoples near the Marlin Mine in Western Guatemala

In August 2009 a combined epidemiological and ecological pilot study was conducted to investigate allegations of human rights abuses in the form of exposures to toxic metals experienced by mine workers and Indigenous Mam Mayan near the Marlin Mine in Guatemala. In the human study there were no differences in blood and urine metals when comparing five mine workers with eighteen non-mine workers, and there were no discernible relationships between metal exposures and self-reported health measures in any study group. On the other hand, individuals residing closest to the mine had significantly higher levels of certain metals (urinary mercury, copper, arsenic, and zinc) when compared to those living further away. The levels of blood aluminum, manganese, and cobalt were elevated in comparison to established normal ranges in many individuals; however, there was no apparent relationship to proximity to the mine or occupation, and thus are of unclear significance. In the ecological study, several metals (aluminum, manganese, and cobalt) were found significantly elevated in the river water and sediment sites directly below the mine when compared to sites elsewhere. When the human and ecological results are combined, they suggest that exposures to certain metals may be elevated in sites near the mine but it is not clear if the current magnitude of these elevations poses a significant threat to health. The authors conclude that more robust studies are needed while parallel efforts to minimize the ecological and human impacts of mining proceed. This is critical particularly as the impact of the exposures found could be greatly magnified by expected increases in mining activity over time, synergistic toxicity between metals, and susceptibility for the young and those with pre-existing disease.     

Cobalt speciation in urine of hard metal workers. A study carried out by nuclear and radioanalytical techniques

A method for the determination of inorganic and organically-bound cobalt in human urine has been developed and applied to the urine of hard metal workers. The development was based on the use of the radionuclides ⁵⁷Co, ⁵⁸Co and ⁶⁰Co-labelled Co compounds such as Co-Vitamin B12 and CO²⁺ ions which allowed the study of their biotransformations in human and rat urine. The proposed procedure is based on the use of Chelex 100 resin which retains quantitatively the inorganic Co from the urine while the organic complexed form of the element is eluted. Cobalt is detected in both column and eluate by neutron activation analysis (NAA). The method has been applied to speciate inorganic and organically-bound Co in the urine of hard metal workers. There is a significant increase (P < 0.02) of the ratio inorganic/organic Co (2.3) in the urine of workers compared with controls (1.01), showing an increase of the inorganic fraction of Co in the urine of workers. The ratio was constant for the wide range of urinary Co analyzed (from 180 μg to 1254 μg Co/l). Therefore, the discrimination between inorganic and organic Co in urine should not represent progress in the biological monitoring of Co compared with the determination of total urinary Co. However, a large amount of organically-complexed Co is formed in the body of hard metal workers and excreted in urine, thus, investigationsof the nature of the organocobalt compounds are of fundamental importance in establishing their possible clinical significance.     

Cobalt-related asthma: clinical and immunological aspects

Several clinical and experimental findings point to cobalt as the only sensitizer and causal agent of hard metal asthma. The clinical features have been clearly defined by bronchial provocation tests, with a prevalence of late phase responses. Epidemiology is still insufficient to configure prevalence and incidence rates for cobalt asthma. IgE and IgG antibodies with cobalt specificity have been demonstrated, but T-lymphocytes and eosinophyls involvement seem to be important in the mechanism of an allergic inflammation in the airways. Such an immunological pathogenesis links cobalt asthma with other manifestation of hard metal disease.     

Urinary thallium: critical problems, reference values and preliminary results of an investigation in workers with suspected industrial exposure

Using a sensitive ETA ASS method, urinary thallium (Tl-U) has been measured in a group of non-exposed individuals and in two groups of workers with suspected industrial exposure. In non-exposed subjects (72 healthy males aged 41 +/- 11 years) the Tl-U mean value was 0.22 mu/l (range 0.05-0.61). Significantly higher values were found in two groups of workers (30 and 21 subjects) employed in two cement factories and two cast iron foundries (mean Tl-U value: 0.38 and 0.33 mu/l, respectively; range 0.06-1.2). Thallium has been determined in coal, raw materials and, in one factory, also in environmental samples, but no detectable levels were found. The analytical problems connected to urinary thallium determination and the preliminary results of biological monitoring in non-exposed individuals and in workers are discussed.     

Occupational dermatitis in a highly industrialized Italian region: the experience of four occupational health departments

There is a need for several research centers to carry out coordinated large-scale evaluation of the spread of occupational irritant and allergic dermatitis. The Occupational Health Departments of Bergamo, Brescia, Lecco and Cremona therefore decided to join their experiences and bring together all the cases of occupational irritant and allergic dermatitis diagnosed by these Departments between 1993 and 1998. In this period, 1169 cases of occupational dermatitis were diagnosed, subdivided into 768 cases of allergic contact dermatitis (ACD), 337 of irritant contact dermatitis (ICD), 54 of urticaria and 10 of airborne contact dermatitis, and there has not been a trend towards increase of occupational dermatitis over the years. Our population included 724 males and 445 females and average latency after the beginning of exposure to occupational allergens was 8.01 years for ACD, 6.4 for ICD, 3.22 for urticaria and 5.57 for airborne contact dermatitis. The frequency of atopy was 33.9%, in females and 19.5% in males. The frequency of atopy was particularly high (89%) in subjects with urticaria. Among subjects with allergic dermatitis, 362 had had only one sensitization while 406 had had two or more sensitizations. The working areas where we found the highest number of ACD were metal working industry, building, health care workers and hairdressers and the frequency of ICD was high in metal workers and health care workers. Most of the cases of urticaria were diagnosed in health care workers (68.5%) and the main causing agent was latex. These are only preliminary data but occupations at risk and the substances expected to be the most frequent etiological agents do not differ significantly from those reported in the literature. It is hoped that as a result of this project there will be in the future: standardization of diagnostic procedures, uniform assessment of allergological risk in working environments not yet fully investigated, standardization of preventative measures and proper evaluation of their effectiveness.     

Absorption and excretion of cobalt in the hard metal industry

Absorption and excretion of cobalt in the hard metal industry was investigated by means of ambient air and urine measurements in three factories with high levels of environmental cobalt pollution. In the presence of poor hygiene conditions and permission to smoking during work, there was no relationship between cobalt ambient air and cobalt urine concentrations. Such a finding was therefore attributed to a substantial skin contact. A simple experiment of skin exposure to freshly mixed or waste powder on volunteers identified a ten-fold increase of cobalt in urine in the post-exposure samples, thus confirming the contribution of dermal exposure as a route of entry. An improvement in the hygiene of the working conditions helped to investigate the relationship between exposure and excretion level. Cobalt uptake through the different routes of entry may be substantial, and requires a more prolonged exposure-free period so that the excretion rate can be reduced to the reference population level.     

Distribution of 23 elements in the kidney,liver and lungs of workers from a smeltery and refinery in north Sweden exposed to a number of elements and of a control group

The levels of antimony, arsenic, cadmium, caesium, chromium, cobalt, copper, gold, iron, lanthanum, lead, manganese, mercury, molybdenum, phosphorus, rubidium, scandium, selenium, silver, tellurium, tin, tungsten and zinc in the kidney, liver and lungs of autopsy specimens from exposed workers in North Sweden, as well as from a control group, have been assayed quantitatively. The workers had been exposed to several elements and their compounds, e.g. lead, mercury, arsenic and cadmium, for long periods in arsenic, lead or selenium plants and in a lead or copper smelter.The chemical analysis was by neutron activation analysis and atomic absorption spectrophotometry.Median levels of antimony, arsenic, cadmium, chromium, cobalt, lanthanum, lead or selenium in kidney, liver or lungs in the exposed worker group were found to be about 2 to 16 times as great as the corresponding levels for the control group. Long biological half-life values were observed for these elements, especially in lung tissue.     

Health problems in Galena, Kansas: a heavy metal mining Superfund site

Health problems at a heavy metal mining Superfund site were surveyed using prevalence information from 1980-85. Current environmental exposures include lead and cadmium in drinking water, mine wastes, and surface soils. Age- and sex-specific illness rates in whites in an exposed town (Galena) were compared with similar rates in two control towns. Multivariate analyses of morbidity data examined statistically significant risk factors for relevant illness in the three towns. Mortality rates for 1980-85 for white residents of Galena and for the U.S. were compared using univariate analysis. Among residents of the three towns who had lived there at least 5 years prior to 1980, there was either a statistically significant or borderline excess reported prevalence in Galena of chronic kidney disease (females aged greater than or equal to 65), heart disease (females aged greater than or equal to 45), skin cancer (males aged 45-64), and anemia (females aged 45-64). Multivariate analyses revealed statistically significant associations of stroke, chronic kidney disease, hypertension, heart disease, skin cancer, and anemia with variables related to Galena exposure. Personal physicians were contacted to confirm the information provided by the subjects; validity was good for all reported illnesses except chronic kidney disease. A statistically significant excess of deaths from hypertensive disease (females aged greater than or equal to 65), ischemic heart disease (males and females aged greater than or equal to 65), and stroke (females aged greater than or equal to 65) was found in residents of Galena City. This study confirms that environmental agents in Galena are associated with, and may have contributed to, the causation of several chronic diseases in residents of this community. Further studies are recommended.     

Relationship between "chelatable lead" and the indicator of exposure and effect in current and past occupational exposure

The behaviour of blood (PbB) and two biological indicators of effect: erythrocyte protoporphyrin (EP) and urinary aminolaevulinic acid (ALAU), were studied in subjects who had ceased working with inorganic lead for at least one year. The relationships between these indices and chelatable lead (PbU-EDTA) were also analysed. As a comparison, a group of subjects currently exposed to inorganic lead was studied. At a given PbU-EDTA level, the PbB values were significantly lower in the workers with past exposure than those found in currently exposed subjects. The relationship between EP and PbU-EDTA illustrates that, for corresponding levels of chelatable lead, the values of the erythrocyte metabolite are identical in the two groups. Considering the EP-PbB relationship, however, at a given PbB level the protoporphyrin values appear distinctly more altered in the subjects with past exposure. The relationship between ALAU and PbU-EDTA shows that, at a given PbU-EDTA level the urinary metabolite in past exposed subjects is distinctly lower than in currently exposed workers, while the relationship between ALAU and PbB shows that, at similar blood lead values, the ALAU levels are identical in both groups. On the basis of these results, it is concluded that in subjects with past exposure, erythrocyte protoporphyrin can be used in establishing the persistence and extent of an "active deposit" of lead in the organism, while PbB and ALAU are of very limited value.     

Tentative reference values for some elements in broncho-alveolar lavage fluid.

The concentrations of Fe, Mn, Pb and Cr have been determined in broncho-alveolar lavage (BAL) fluid of 25 subjects without occupational or abnormal environmental exposure to metals, using the AAS method. The numerous factors which can interfere with the results in pre-analytical and in analytical phases are stressed. Metals concentrations in BAL are expressed in micrograms/l. They were not correlated with the volume of fluid recovered, the total cells, alveolar macrophages and erythrocytes. The results were not modified by stratification considering age and sex. Iron concentrations were higher than others, probably due to higher environmental exposure and partly to its essential role in humans. The diagnostic significance of element determination in BAL fluid and the relationship with exposure and lung load is discussed.     

高地应力硬岩矿山诱导致裂非爆连续开采初探——以开阳磷矿为例

 在阐述深部金属矿硬岩在高地应力作用下储能特征的基础上,分析随着金属矿山开采深度的不断增加,诱导致裂矿岩非爆连续开采方法实现的可能性。实现非爆连续开采硬岩矿山有2个必要条件：一是高效能采掘设备,二是有发育的岩体节理等结构。高地应力矿区岩体开挖卸载后,应力重分布会造成岩体强度的弱化,不稳定块体增加及地下水渗流条件改善,为机械开采提供了有利条件。通过对开阳磷矿深部磷矿体进行的地质调查和对深部磷矿体矿开展的高应力硬岩矿山非爆开采试验,进一步论证高应力诱导致裂硬岩的可行性。通过诱导工程和测试诱导巷道的松动圈范围,证明卸荷作用下岩体的节理、裂隙迅速扩展,诱导巷道的松动圈范围超出爆破松动区范围;松动圈内矿体可实现高效率机械化开采,从而实现硬岩矿山的非爆连续开采;比较独头掘进和开挖诱导巷道下多自由面掘进的效果,诱导致裂条件下开采效率得到显著提升,而且还改善了块度分布。     

Suppression of IL-6 level in human peripheral blood mononuclear cells stimulated with PHA/LPS after occupational exposure to chromium

The toxic metals alter the immune response of animals as well as humans. In addition to the well documented and numerous toxic effect of chromium on various target organs, number of studies shown that acute and chronic exposure to inorganic chromium may result in impairment of immune functions in the experimental systems. Immunosuppression appears to be more subtle effect of exposure to heavy metals. Therefore, we have taken two different groups of chromium exposed individuals. These were leather tanning workers and chromeplaters. These groups of individuals were regularly exposed to chromium. All the leather tanning workers were highly exposed to chromium having a mean of 96.60+/-113.95 mg/dl (range 12.4-417.21 mg/dl). A suspension of exposed and unexposed human PBMC (0.5x10(6) cells/ml) prepared and cultured in RPMI-1640 supplemented with 10% FCS for 18 h in the presence or absence of PHA (5 microg/ml) and LPS (10 ng/ml) which used for stimulation of IL-2, IL-4, TNF-alpha, IL-10 and IL-6, respectively. The levels of Th1/Th2 cytokine: IL-2, IL-4, TNF-alpha, IL-10 and IL-6 were evaluated in the sera and PHA/LPS stimulated culture supernatant of human PBMCs of chromium exposed workers. In these workers the level of IL-6 was 543.95+/-123.75 pg/ml and 388.40+/-61.24 pg/ml in PHA/LPS stimulated culture supernatant of normal individuals and highly chromium exposed workers, which was significant (P<0.05). This observation suggests that IL-6 levels were suppressed in chromium exposed groups as compared to unexposed healthy volunteers. Although the level of IL-2 in PHA stimulated culture supernatant of PBMCs was suppressed in chromium exposed individuals but it was not significant, IL-4 and IL-10 could not be detected. However, there was no difference in TNF-alpha levels in sera samples as well as unstimulated culture supernatant of h-PBMCs of chromium exposed individuals as compared to control.     

Assessment of nickel and cobalt release from 200 unused hand-held work tools for sale in Denmark - Sources of occupational metal contact dermatitis?

Introduction

Nickel and cobalt allergy remain frequent in dermatitis patients. It is important to determine possible nickel and cobalt exposures at work as these may offer important information to regulators and physicians who perform patch testing. Clinical relevance of metal exposure is usually assessed by the treating physician via the medical history and by presentation of allergic contact dermatitis.

Objectives

To screen unused non-powered hand-held work tools for nickel and cobalt release by using colorimetric spot tests.

Materials & methods

A random selection of 200 non-powered hand-held work tools for sale in 2 retailers of home improvement and construction products were analyzed qualitatively for metal release using the colorimetric nickel and cobalt spot tests.

Results

Nickel release was identified from 5% of 200 work tools using the dimethylglyoxime (DMG) test. In 8 of 10, positive results were located to the metal ring that acts like a cuff and is located at the end of the grip. The positive DMG test results were not related to specific categories of work tools. The cobalt spot test gave no positive test reactions.

Conclusions

It appears that the proportion of work tools that release nickel, in amounts that may result in allergic nickel dermatitis, has decreased markedly, when results were compared with a Swedish study performed more than a decade ago. No cobalt release was detected but it should be underscored that hard-metal tools were not examined. Other sources of cobalt may explain the relatively high levels of cobalt allergy in dermatitis patients.