Physicochemical characteristics and biological effects of nickel oxides

Metals, nonmetals and metalloids in cigarette smoke as hazardous compounds for human health

Cigarette smoke contains many chemicals that are harmful to both smokers and non-smokers. Breathing just a little cigarette smoke can be harmful. There are >7000 chemicals in cigarette smoke, at least 250 are known to be harmful and many of them can cause cancer. Currently, many studies reported the types of harmful organic compounds in cigarette smoke; instead, there are almost no works that describe the presence of inorganic compounds. In this work, a cost-effective self-made passive sampler (SMPS) was tested as a tool to collect different types of particulate matter (PM) from cigarette smoke containing metals as hazardous compounds (HCs). To determine the nature of the metals, nonmetals and metalloids as HCs, a direct qualitative analysis of the particulate matter (PM) was conducted without developing any special sample preparation procedure. For that, non-invasive elemental (Scanning Electron Microscope coupled to Energy Dispersive X-ray Spectrometry) and molecular (Raman microscopy) micro-spectroscopic techniques were used. Thanks to this methodology, it was possible to determine in deposited PM, the presence of metals such as Fe, Cr, Ni, Ti, Co, Sn, Zn, Ba, Al, Cu, Zr, Ce, Bi, etc. most of them as oxides but also embedded in different clusters with sulfates, aluminosilicates, even phosphates.

Electron microscopy of particles deposited in the lungs of nickel refinery workers

The size, morphology, and chemical composition of particles deposited in the lungs of two nickel refinery workers were studied by scanning and transmission electron microscopy. The particles were extracted from the lung tissue by low-temperature ashing or by dissolution in tetramethylammonium hydroxide. The suitability of both sample preparation techniques was checked with reference materials. Both approaches lead to Fe-rich artifact particles. Low-temperature ashing leads to oxidation of small (diameter < 2 μm) metallic Ni and Ni sulfide particles, dissolution in tetramethylammonium hydroxide to removal of sulfate surface layers. Silicates and alumosilicates are the most abundant particle groups in the lungs of both subjects. From the various metal-dominated particle groups, Ni-rich particles are most abundant followed by Fe-rich and Ti-rich particles. Ni appears to be present predominantly as an oxide. Pure Ni metal and Ni sulfides were not observed. The presence of soluble Ni phases was not investigated as they will not be preserved during sample preparation. Based on their spherical morphology, it is estimated that a large fraction of Ni-rich particles (50-60 % by number) as well as Fe-rich and Cu-rich particles (27-45 %) originate from high-temperature processes (smelting, welding). This fraction is much lower for silicates (3-5 %), alumosilicates (1-2 %), and Ti-rich particles (9-11 %). The absence of metallic Ni particles most likely results from low exposure to this species. The absence of Ni sulfides may be either ascribed to low exposure or to fast clearance.

Functionalized Magnetic Nanoparticles for Environmental Remediation

Water pollution by anthropogenic activities is proving to be of critical concern as the heavy metals affect aquatic organisms and can quickly disperse to large distances. This poses a risk to both human health and the aquatic biota. Hence, there is a need to treat the wastewater containing toxic metals before they are discharged into the water bodies. During recent years, magnetic nanoparticles came to the foreground of scientific interest as a potential adsorbent of novel wastewater treatment processes. Magnetic nanoparticles have received much attention due to their unique properties, such as extremely small size, high surface-area-to-volume ratio, surface modifiability, multi functionality, excellent magnetic properties, low-cost synthesis, and great biocompatibility. The multi-functional magnetic nanoparticles have been successfully applied for the reduction of toxic metal ions up to ppb level in waste-treated water. This chapter highlights the potential application of magnetic nanoparticles for the removal of heavy metals.

Nickel release and surface characteristics of fine powders of nickel metal and nickel oxide in media of relevance for inhalation and dermal contact

Differences in surface oxide characteristics and extent of nickel release have been investigated in two thoroughly characterized micron-sized (mainly <4 μm) nickel metal powders and a nickel oxide bulk powder when immersed in two different synthetic fluids, artificial sweat (ASW-pH 6.5) and artificial lysosomal fluid (ALF-pH 4.5) for time periods up to 24h. The investigation shows significantly more nickel released from the nickel metal powders (<88%) compared to the NiO powder (<0.1%), attributed to differences in surface properties. Significantly more nickel was released from the nickel metal powder with a thin surface oxide predominantly composed of non-stoichiometric nickel oxide (probably Ni(2)O(3)), compared to the release from the nickel metal powder with a thicker surface oxide predominantly composed of NiO and to a lesser extent Ni(2)O(3) (88% and 25% release after 24 h in ALF, respectively). Significantly lower amounts of nickel were released from the nickel metal powders in ASW (2.2% and <1%, respectively). The importance of particle and surface characteristics for any reliable risk assessment is discussed, and generated data compared with literature findings on bioaccessibility (released fraction) of nickel from powders of nickel metal and nickel oxide, and massive forms of nickel metal and nickel-containing alloys.

A pharmacokinetic model of the intracellular dosimetry of inhaled nickel

The potential associations between exposure to nickel compounds and cancer have been evaluated in both animal and epidemiological studies of occupationally exposed workers. The results of the epidemiological studies suggest that not all nickel compounds are equally carcinogenic, an observation supported by the animal bioassay results. Given the complexity and the differences in the modes of uptake of different forms of nickel by cells and the subsequent delivery of nickel to the nucleus, it would be expected that some forms of nickel would be more potent than others. A physiologically based pharmacokinetic (PBPK) model would be useful in estimating the cellular exposure to nickel resulting from inhalation of the different forms of nickel. To this end, a preliminary model of a tracheobronchial epithelial cell was developed to describe the differences in the extracellular and intracellular kinetics of the different classes of nickel compounds. Data available in the published literature were used to define the initial model parameters. The resulting cellular dosimetry model was able to describe kinetic data on three forms of nickel (soluble chloride and insoluble sulfide and subsulfide). This preliminary model development effort has identified critical data gaps that could be filled by additional research. The ultimate goal will be to integrate a refined cellular dosimetry model with published lung deposition/clearance and systemic distribution/clearance models for nickel. The use of such an integrated PBPK model would allow for more biologically based risk estimates for the inhalation of the different nickel compounds, as well as mixtures of these compounds.

Respiratory cancer risks associated with low-level nickel exposure: an integrated assessment based on animal, epidemiological, and mechanistic data

Increased lung and nasal cancer risks have been reported in several cohorts of nickel refinery workers, but in more than 90% of the nickel-exposed workers that have been studied there is little, if any evidence of excess risk. This investigation utilizes human exposure measurements, animal data from cancer bioassays of three nickel compounds, and a mechanistic theory of nickel carcinogenesis to reconcile the disparities in lung cancer risk among nickel-exposed workers. Animal data and mechanistic theory suggest that the apparent absence of risk in workers with low nickel exposures is due to threshold-like responses in lung tumor incidence (oxidic nickel), tumor promotion (soluble nickel), and genetic damage (sulfidic nickel). When animal-based lung cancer dose-response functions for these compounds are extrapolated to humans, taking into account interspecies differences in deposition and clearance, differences in particle size distributions, and human work activity patterns, the predicted risks at occupational exposures are remarkably similar to those observed in nickel-exposed workers. This provides support for using the animal-based dose-response functions to estimate occupational exposure limits, which are found to be comparable to those in current use.

The histone deacetylase inhibitor trichostatin A reduces nickel-induced gene silencing in yeast and mammalian cells

We have previously reported that nickel (Ni)-silenced expression of the URA3 gene in yeast (Saccharomyces cerevisiae) and gpt transgene in G12 Chinese hamster cells. In both cases, close proximity to a heterochromatic region was required for gene silencing. Yeast exposed to Ni exhibited reduced acetylation of the lysine residues in the N-terminal tail of histone H4. Ni-induced silencing of the gpt gene in mammalian cells involved hypermethylation of promoter region DNA. Yeast do not employ DNA methylation to silence gene expression. To determine if histone deacetylation participates in Ni-induced silencing of the URA3 and gpt genes, we exposed yeast and G12 hamster cells to the histone deacetylase inhibitor trichostatin A (TSA) prior to and concurrently with Ni. Treatment of yeast cells with 0.2-0.6mM NiCl(2) resulted in reduced expression of the URA3 gene as assessed by increased resistance to 1g/l 5-fluorotic acid (5-FOA). This effect was lessened when yeast were pre-treated with 50 microg TSA/ml. Similarly, treatment of G12 cells with 5 ng/ml TSA during and after exposure to 0.3 microg Ni(3)S(2)/cm(2) reduced silencing of the gpt gene as gauged by resistance to 10 microg/ml 6-thioguanine (6-TG). The ability of TSA alone and in combination with the DNA-demethylating agent (5-AzaC) to reactivate the gpt gene in Ni-silenced variants was also assessed. Although treatment with 100 ng/ml TSA for 48 h was partially effective in reactivating the gpt gene, treatment with 5 microM 5-AzaC was more efficacious. The greatest gpt gene reversion frequencies were observed following a sequential 5-AzaC/TSA treatment. Taken all together, our data from mammalian cells suggests that both DNA methylation and histone deacetylation participate in Ni-induced silencing of the gpt gene with DNA hypermethylation playing the more dominant role in maintaining the silenced state.

Physicochemical characteristics and toxicity of nickel oxide particles calcined at different temperatures

The physicochemical characteristics and cytotoxicity of two types of commercial nickel oxide particles (black and green nickel oxide) and five types of nickel oxide particles prepared by calcination of the black nickel oxide at 600-1000 degrees C were studied. Thermal analysis with mass spectroscopy showed that the black nickel oxide particles contained approximately 1.4% impurity, which seemed to be basic nickel carbonate. The calcination treatment at 600 degrees C increased the nickel content and decreased the oxygen content, but these remained constant in the particles treated at higher temperatures (700-1000 degrees C) and in the green nickel oxide particles. The water solubility of black nickel oxide particles was markedly greater than that of the other particles, especially in the first 24 h after mixing with water. The solubility of the calcined particles decreased with increasing calcination temperature. The cytotoxicity of these particles was evaluated by the viability of rat alveolar macrophages and by the inhibition of cell proliferation in Chinese hamster ovary cells. The black nickel oxide was the most cytotoxic of the particles examined, and this may be attributable, at least in part, to a rapid dissolution of nickel from the contained impurity. The toxicity of the calcined particles decreased with increasing calcination temperature. These results indicate that water solubility, which depends on calcination temperature, modulates the acute cytotoxicity of nickel oxide particles.

Carcinogenicity assessment of selected nickel compounds

The early epidemiological data indicated different carcinogenic risks from inhalation of different nickel compounds, but it was not clear what characteristics governed the intrinsic carcinogenic hazard of the various nickel compounds. Based on the earlier results, all soluble and insoluble nickel compounds were assumed to have the same carcinogenic mechanism albeit different potencies. Recent in vivo and in vitro studies challenged this assumption. In this paper an attempt is made to integrate the most relevant human, animal, and in vitro data into a general model that can help understand the different carcinogenic potentials of the various nickel compounds. In this perspective, it is recognized that there are two main components that could contribute to the development of lung cancer via exposure to certain nickel compounds. The first component corresponds to the heritable changes (genetic or epigenetic) derived from the direct or indirect actions of nickel compounds. The second component may be the promotion of cell proliferation elicited by certain nickel compounds. The different contributions of three nickel compounds to these two components are presented. This paper emphasizes the importance of recognizing the individuality of the different nickel species in reaching regulatory decisions and the fact that different risk assessment considerations may apply for compounds that appear to produce immortality and cancer by genetic/epigenetic mechanisms (like nickel subsulfide), compounds that may present a threshold for the induction of tumors in rats (like high-temperature nickel oxide), or compounds that may only have an enhancing effect on carcinogenicity (like nickel sulfate).

Exposure to nickel compounds and smoking in relation to incidence of lung and nasal cancer among nickel refinery workers

OBJECTIVES

To investigate the relation between occupational hazards among nickel refinery workers and their exposure to different forms of nickel over time and the interaction between smoking and total exposure to nickel.

METHODS

The cohort consisted of 379 workers with first employment 1916-40 and at least three years of employment and 4385 workers with at least one year of employment 1946-83. Data on smoking (ever or never) were available for almost 95% of the cohort. Two analyses were used, indirect standardisation from observed and expected numbers and Poisson regression.

RESULTS

During the follow up 1953-93, 203 new cases of lung cancer were observed v 68 expected (standardised incidence ratio (SIR) 3.0, 95% confidence interval (95% CI) 2.6-3.4) and 32 cases of nasal cancer were observed v 1.8 expected (SIR 18.0, 95% CI 12-25). The Poisson regression analysis showed an excess risk of lung cancer in association with exposure to soluble forms of nickel, with a threefold increase in relative risk (RR) (P < 0.001) and a multiplicative effect of smoking and exposure to nickel. The RRs were 1.1 (95% CI 0.2-5.1) for exposed workers who had never smoked and 5.1 (95% CI 1.3-20.5) for exposed workers who smoked.

CONCLUSION

It is not possible to state with certainty which specific nickel compounds are carcinogenic, but a significant excess risk was found for workers exposed to soluble nickel alone or in combination with other forms of nickel. The present study suggests a multiplicative effect of smoking and nickel exposure.

Mutagenicity of cobalt and reactive oxygen producers

Oxidative stress has been implicated in carcinogenesis yet there are chemicals that produce oxidative stress that are not carcinogenic. Mutations are the inherited results of DNA damage and are critical events in carcinogenesis. The mutagenicity of oxidative stress induced by peroxide, paraquat and cobalt compounds was examined in transgenic gpt+ Chinese hamster cell lines (G12 and G10). These two cell lines are known to be more sensitive to mutagens such as X-rays and UV than their parental V-79 cells. In these studies, the mutagenic activity of cobalt chloride, a metal that induces oxidative stress but is not carcinogenic, was measured to be 7.7 times higher than the spontaneous mutant frequency in G12, but was only 1.5 to 2.5 times higher than spontaneous mutant frequency in G10 cells. The mutant frequency of cobalt sulfide was somewhat lower. Hydrogen peroxide was found to be only weakly mutagenic in G12 cells, and treatment of cells with a combination of hydrogen peroxide and cobalt did not alter the mutation frequency induced by cobalt sulfide alone. Paraquat did not elicit mutagenesis in either cell line. These results indicate that agents producing oxidative stress are not necessarily mutagenic and these results are discussed in the context of the oxidative stress produced by other carcinogens such as nickel compounds.

Comparison of the standard and reduced pH Syrian hamster embryo (SHE) cell in vitro transformation assays in predicting the carcinogenic potential of chemicals

A comprehensive review of the Syrian Hamster Embryo (SHE) cell transformation literature was performed in order to catalogue the chemical/physical entities which have been evaluated for in vitro cell transformation potential. Both reduced pH (pH 6.7) and standard pH (pH 7.1-7.3) SHE cell testing protocols were considered. Based upon this analysis, over 472 individual chemical/physical agents and 182 combinations of chemical/physical agents have been tested under the standard pH conditions, while over 56 chemical/physical agents have been tested under reduced pH conditions. Of the 472 chemical/physical agents tested at the standard pH, 213 had in vivo carcinogenicity data available. Of these 213 chemical/physical agents, 177 were carcinogens while 36 were non-carcinogens. The results of testing the SHE transformability of these 213 chemical/physical agents indicates that the standard pH SHE cell transformation assay had a concordance of 80% (171/213), a sensitivity of 82% (146/177), and a specificity of 69% (25/36). Of these 213 chemical/physical agents, 53% (112/213) were tested more than once often in more than one laboratory, with a 82% (92/112) interlaboratory agreement rate, thus providing confirmatory results. Carcinogenicity data were available for 48 of the 56 chemical/physical agents tested for SHE cell transformation under the reduced pH conditions. The SHE cell transformation assay under reduced pH conditions had a concordance of 85% (41/48), a sensitivity of 87% (26/30), and a specificity of 83% (15/18). For Salmonella-negative carcinogens, the standard pH SHE assay correctly predicted carcinogenicity 75% (48/64) of the time while the reduced pH SHE assay correctly predicted carcinogenicity for Salmonella-negative carcinogens 78% (14/18) of the time. For chemical/physical agents tested under both the reduced pH and standard pH conditions, the standard pH and reduced pH SHE cell assays had a 69% (22/32) agreement rate. Under the reduced pH conditions, the SHE assay correctly predicted rodent carcinogenicity in 86% (25/29) of the chemicals tested under both reduced and standard pH conditions. Under standard pH conditions, the SHE assay correctly predicted rodent carcinogenicity in 69% (20/29) of the chemicals tested under both reduced and standard pH conditions. Collectively, these data indicate that the SHE cell transformation assay is predictive for rodent carcinogenicity under either reduced or standard pH conditions. Importantly, the assay displays better performance and appears to have improved carcinogen prediction capability under reduced pH conditions.

Transformation of rat tracheal epithelial cells to immortal growth variants by particulate and soluble nickel compounds

The cytotoxicity and transforming activity of nickel subsulfide, nickel oxide and nickel sulfate was studied by assays of colony-forming efficiency and of transformation of rat tracheal epithelial (RTE) cells to enhanced growth variants (EGVs) and immortal growth variants (IGVs). Nickel subsulfide caused dose-dependent cytotoxicity between 1 and 5 micrograms/ml, whereas the cytotoxic range of nickel oxide and nickel sulfate was 50-200 micrograms/ml and 60-130 micrograms/ml, respectively. At lower concentrations, nickel sulfate caused modest (up to 126%) growth stimulation. During the initial 24-h treatment period, internalized nickel subsulfide particles were observed in phagocytic vesicles in cells near the periphery of all RTE cell colonies, whereas nickel oxide particles were not internalized but had adhered to both the cells and the tissue culture dish. After 7-10 days of the transformation assay, nickel subsulfide particles were no longer visible, but nickel oxide particles remained on the dish for the duration of the 5 week assay. During weeks 3-5 of the transformation assay, internalized nickel oxide particles were observed in non-vacuolated cells at the periphery of the colonies. All 3 nickel compounds significantly (p < 0.05) increased the transformation frequency of RTE cells to EGVs at moderately cytotoxic concentrations; the order of potency was Ni3S2 > NiO = NiSO4. MNNG, the positive control, was twice as active as nickel subsulfide at 1/3 the concentration and 1/6 the duration of treatment. EGVs induced by MNNG, nickel subsulfide and nickel sulfate were cloned and converted to IGVs at frequencies of 44, 24 and 43%, respectively. In contrast, EGVs transformed by nickel oxide rarely converted to IGVs (13%). All nickel-induced IGVs were immunohistochemically epithelial, mitotically active, aneuploid and exhibited high plating efficiencies. Our results suggest that respiratory epithelial cells are targets for the transforming capabilities of several nickel compounds but that the potency and mechanism of transformation by various forms of nickel may be different according to the physico-chemical properties of each compound.

Mutagenic responses of nickel oxides and nickel sulfides in Chinese hamster V79 cell lines at the xanthine-guanine phosphoribosyl transferase locus

Mutagenesis of several insoluble nickel compounds--crystalline nickel sulfide NiS, nickel subsulfide Ni3S2, nickel oxides (black and green) and soluble NiCl2 was studied in three Chinese hamster cell lines--at the hprt gene of the well-defined V79 cell line, and at gpt in two transgenic derivative cell lines G12 and G10. The transgenic cell line G12 responded very strongly to the insoluble Ni compounds, such that the gpt mutagenesis was at least 20 times higher than the spontaneous mutagenesis and in some experiments was even higher. In contrast the response of the G10 cells was much lower--the mutant frequencies only increased 2-3 times over the controls. In V79 cells, NiS and NiO (black) did not induce a mutagenic response at hprt. Soluble NiCl2 also exhibited no mutagenic activity in V79 cells and induced considerably lower activity than the insoluble compounds in the transgenic G12 cells. Following vitamin E pretreatment of G12 cells for 24 h prior to nickel exposure, increased cell survival was observed for several insoluble Ni compounds whereas vitamin E had no effect on NiCl2 cytotoxicity. With vitamin E pretreatment, significantly lower mutagenic responses in G12 cells were also noted for some insoluble Ni compounds, while no such effect was observed for NiCl2.

Metal carcinogenesis: mechanistic implications

Cancer epidemiology has identified several metal compounds as human carcinogens. Recent evidence suggests that carcinogenic metals induce genotoxicity in a multiplicity of ways, either alone or by enhancing the effects of other agents. This review summarizes current information on the genotoxicity of arsenic, chromium, nickel, beryllium and cadmium compounds and their possible roles in carcinogenesis. Each of these metals is distinct in its primary modes of action; yet there are several mechanisms induced by more than one metal, including: the induction of cellular immunity and oxidative stress, the inhibition of DNA metabolism and repair and the formation of DNA- and/or protein-crosslinks.

Verifying the composition of certain commercial nickel compounds

Forty commercial samples chosen from three families of nickel compounds were purchased and chemically analyzed. The selection included 21 basic nickel carbonates, 5 nickel sulfides, and 14 nickel oxides sold by 18 producers or distributors in eight countries. The analytical results were compared with the information provided on the container labels. A number of errors were found in the label information ranging from minor inconsistencies and incomplete information to actual misrepresentation of the product. For example, nickel(II) oxides containing only 1-2% Ni(III) are being offered for sale as "nickel(III) oxide, Ni(2)O(3)." Thus researchers should not accept at face value the chemical identity presented by producers or distributors in catalogs and on labels. Since significant variations in biological properties have been found within each of these three families of nickel compounds, researchers should carefully establish which particular member of a family is being studied. Unfortunately, the literature on the biological effects of nickel compounds contains numerous studies where this was not done. Attributing the results of such studies to other or, worse, to all members of the same family of nickel compounds may introduce significant errors into risk assessments.

A rapid digestion method for analysis of nickel compounds in tissue by electrothermal atomic absorption spectrometry

Quantification of nickel in animal soft tissue is of toxicological interest. A digestion method applying the use of microwave ovens for irradiating samples in Teflon digesters was developed. An acid mixture containing nitric acid (16 M, 1.0 ml g-1 tissue), hydrochloric acid (6 M, 0.5 ml g-1 tissue) and H2O2 (30%, 1.0 ml g-1 tissue) and irradiation at 600 W for 5 min were required for complete dissolution of tissue matrices and nickel compounds. Analyses of Ni in National Bureau of Standards Reference Material 1566 oyster tissue gave 0.87 +/- 0.24 micrograms g 1(mean +/- SD, n = 5), which was in agreement with the NBS certified value of 1.03 +/- 0.19 micrograms g-1. Recoveries of 1-300 micrograms Ni added as nickel sulfate (highly soluble), nickel subsulfide (moderately soluble in biological fluids and acid) or nickel oxide (green high-temperature oxide, low solubility in biological fluids and acid) to lung, liver, lymph node and kidney were quantitative, except in the case of nickel sulfate added to kidney, where recovery was less than quantitative for 1-10 micrograms Ni. The method appears effective for digestion of a variety of tissues requiring Ni analyses.

Superoxide dismutase activity and novel reactions with hydrogen peroxide of histidine-containing nickel(II)-oligopeptide complexes and nickel(II)-induced structural changes in synthetic DNA

At physiologic pH values, histidine-containing nickel(II) oligopeptides reduced the flux of superoxide anion (O2-) generated in the hypoxanthine/xanthine oxidase system. The postulated involvement of the Ni(III)/Ni(II) redox couple in this apparent dismutation receives indirect support from electron-spin resonance data. These complexes also catalyzed the disproportionation of hydrogen peroxide, a process which generates active intermediates capable of hydroxylating p-nitrophenol and oxidizing uric acid to allantoin. An oxene moiety, namely [Nio]2+, is postulated as the active species in these H2O2-dependent reactions. Spectral analysis showed that monovalent, divalent and trivalent ions induced cooperative conformational changes in synthetic polydeoxynucleotides. For the nickel(II) ion, resistance to DNase-I activity clearly showed that an alternating G-C sequence is required for the observed transitions. It is concluded that the ability of nickel(II) peptide complexes to participate in active oxygen biochemistry suggests a possible role for nickel as a chemical promoter of cancer, whereas the capacity of the nickel(II) ion to induce conformational changes in DNA could, in principle, affect gene expression. Of course, the validity of both hypotheses require that the observed reactions be verified as biologically significant.

Determination of nickel in lung specimens of thirty-nine autopsied nickel workers

Lung specimens from 39 nickel refinery workers autopsied during the period from 1978 to 1984 were analyzed for nickel. Fifteen of the workers were employed in the Roasting and Smelting Department, where exposure to nickel was predominantly in the form of nickel-copper oxides, Ni3S2 and metallic dust. The remaining 24 men worked in the Electrolysis Department. Exposure in this group was considered to be mostly to the water-soluble compounds, NiSO4 and NiCl2, but also to a lesser degree to water-insoluble nickel compounds such as nickel-copper oxides and sulphides. The arithmetic mean +/- SD for nickel concentration in lung tissues expressed in micrograms g-1 dry wt for the 39 workers was 150 +/- 280. In the workers employed in the Roasting and Smelting Department, the average nickel concentration was 330 +/- 380; for those who worked in the Electrolysis Department it was 34 +/- 48. Lung tissue from 16 autopsied persons not connected with the refinery had an average nickel concentration of 0.76 +/- 0.39. Statistical analysis based on log-normal distributions of the measured nickel concentrations allowed three major conclusions to be formulated: (1) nickel refinery workers exhibit elevated nickel levels in lung tissues at autopsy; (2) workers of the Electrolysis Department and the Roasting Smelting Department constitute distinct groups with respect to the accumulation of nickel in lung tissue; (3) workers who were diagnosed to have lung cancer had the same lung nickel concentrations at autopsy as those who died of other causes.

Toxicity and carcinogenicity of nickel compounds

The toxicity and carcinogenicity of nickel compounds are considered in three broad categories: (1) systemic toxicology, (2) molecular toxicology, and (3) carcinogenicity. The systemic toxicity of nickel compounds is examined based upon human and animal studies. The major organs affected are discussed in three categories: (1) kidney, (2) immune system, and (3) other organs. The second area of concentration is molecular toxicology, which will include a discussion of the chemistry of nickel, its binding to small and large molecular weight ligands, and, finally, its cellular effects. The third major area involves a discussion of the carcinogenicity and genotoxicity of nickel compounds. This section focuses on mechanisms, using studies conducted in vivo and in vitro. It also includes a discussion of the assessment of the carcinogenicity of nickel compounds.

Comparative in vitro cytotoxicity of nickel oxides and nickel-copper oxides to rat, mouse, and dog pulmonary alveolar macrophages

Metal oxides containing either Ni alone (NiO's) or both Ni and Cu (Ni-CuO's) are encountered during Ni refining. Six NiO compounds calcined at temperatures ranging from less than 650 to 1045 degrees and four Ni-CuO's containing from 6.9 to 28% Cu and 44 to 69% Ni were screened for their in vitro cytotoxicity to alveolar macrophages (AM). NiO's were less toxic to rat AM than were the Ni-CuO compounds. The toxicity of the Ni-CuO compounds increased with increasing Cu content and decreasing Ni content of the molecules, indicating that the toxicity was due to the Cu content of the molecules. AM obtained from beagle dogs, F344/N rats, and B6C3F1 mice displayed the following species sensitivities: dog greater than rat = mouse, with dog AM being most sensitive. The observed differences in species sensitivities correlated with differences in the phagocytic abilities of dog, rat, and mouse AM, with the ranking of phagocytic abilities of the AM in decreasing order of ability being dog greater than rat greater than mouse.

Acute nickel toxicity in electroplating workers who accidently ingested a solution of nickel sulfate and nickel chloride

Thirty-two workers in an electroplating plant accidently drank water contaminated with nickel sulfate and chloride (1.63 g Ni/liter). Twenty workers promptly developed symptoms (e.g., nausea, vomiting, abdominal discomfort, diarrhea, giddiness, lassitude, headache, cough, shortness of breath) that typically lasted a few hours but persisted 1-2 days in 7 cases. The Ni doses in workers with symptoms were estimated to range from 0.5 to 2.5 g. In 15 exposed workers who were tested on day 1 postexposure, serum Ni concentrations ranged from 13 to 1,340 micrograms/liter and urine Ni concentrations ranged from 0.15 to 12 mg/g creatinine. Ten subjects (with initial urine Ni concentrations greater than 0.8 mg/g creatinine) were hospitalized and treated for 3 days with intravenous fluids to induce diuresis, resulting in a mean elimination half-time (T1/2) for serum Ni of 27 hours (SD +/- 7 hour), which was significantly shorter (p less than .001) than the mean T1/2 of 60 hours (SD +/- 11 hours) in 11 subjects who did not receive intravenous fluids. Laboratory tests showed transiently elevated levels of blood reticulocytes (N = 7), urine albumin (N = 3), and serum bilirubin (N = 2). All subjects recovered rapidly, without evident sequellae, and returned to work by the eighth day after exposure.