Carcinogenicity, mutagenicity and teratogenicity of nickel

Review of Evidence for Environmental Causes of Uveal Coloboma

Uveal coloboma is a condition defined by missing ocular tissues and is a significant cause of childhood blindness. It occurs from a failure of the optic fissure to close during embryonic development,and may lead to missing parts of the iris, ciliary body, retina, choroid, and optic nerve. Because there is no treatment for coloboma, efforts have focused on prevention. While several genetic causes of coloboma have been identified, little definitive research exists regarding the environmental causes of this condition. We review the current literature on environmental factors associated with coloboma in an effort to guide future research and preventative counseling related to this condition.

Nickel: Human Health and Environmental Toxicology

Nickel is a transition element extensively distributed in the environment, air, water, and soil. It may derive from natural sources and anthropogenic activity. Although nickel is ubiquitous in the environment, its functional role as a trace element for animals and human beings has not been yet recognized. Environmental pollution from nickel may be due to industry, the use of liquid and solid fuels, as well as municipal and industrial waste. Nickel contact can cause a variety of side effects on human health, such as allergy, cardiovascular and kidney diseases, lung fibrosis, lung and nasal cancer. Although the molecular mechanisms of nickel-induced toxicity are not yet clear, mitochondrial dysfunctions and oxidative stress are thought to have a primary and crucial role in the toxicity of this metal. Recently, researchers, trying to characterize the capability of nickel to induce cancer, have found out that epigenetic alterations induced by nickel exposure can perturb the genome. The purpose of this review is to describe the chemical features of nickel in human beings and the mechanisms of its toxicity. Furthermore, the attention is focused on strategies to remove nickel from the environment, such as phytoremediation and phytomining.

Proteomic Assessment of Biochemical Pathways That Are Critical to Nickel-Induced Toxicity Responses in Human Epithelial Cells

Understanding the mechanisms underlying toxicity initiated by nickel, a ubiquitous environmental contaminant and known human carcinogen is necessary for proper assessment of its risks to human and environment. Among a variety of toxic mechanisms, disruption of protein responses and protein response-based biochemical pathways represents a key mechanism through which nickel induces cytotoxicity and carcinogenesis. To identify protein responses and biochemical pathways that are critical to nickel-induced toxicity responses, we measured cytotoxicity and changes in expression and phosphorylation status of 14 critical biochemical pathway regulators in human BEAS-2B cells exposed to four concentrations of nickel using an integrated proteomic approach. A subset of the pathway regulators, including interleukin-6, and JNK, were found to be linearly correlated with cell viability, and may function as molecular determinants of cytotoxic responses of BEAS-2B cells to nickel exposures. In addition, 128 differentially expressed proteins were identified by two dimensional electrophoresis (2-DE) and mass spectrometry. Principal component analysis, hierarchical cluster analyses, and ingenuity signaling pathway analysis (IPA) identified putative nickel toxicity pathways. Some of the proteins and pathways identified have not previously been linked to nickel toxicity. Based on the consistent results obtained from both ELISA and 2-DE proteomic analysis, we propose a core signaling pathway regulating cytotoxic responses of human BEAS-2B cells to nickel exposures, which integrates a small set of proteins involved in glycolysis and gluconeogenesis pathways, apoptosis, protein degradation, and stress responses including inflammation and oxidative stress.

Survey of some heavy metals in sediments from vehicular service stations in Jordan and their effects on social aggression in prepubertal male mice

Vehicle services create the potential for heavy metal accumulation in the working environment. This study assessed five vehicle services, namely body repair, oil exchange, mechanical repair, tire repair, electrical repair, and washing services for three types of vehicles: airplanes, buses, and cars. The results show that there are significant increases in the total contents of Fe, Cu, Pb, Zn, Ni, Mn, and Cr in ambient dust, with Fe being the highest and Cr the lowest. The main cause of the presence of these elements is due to the metals' corrosion from vehicle sources and petroleum residue. Variations in the concentrations with the type of service and within the same service at different locations were observed. In this study, the exposure of prepubertal male mice to industrial metal salts in drinking water at a concentration of 1000 ppm for 90 days was investigated. Exposure of male mice to lead acetate significantly reduced the social aggression of the resident untreated subjects. Additionally, this treatment resulted in decreasing weights of body, testes, preputial glands, and seminal vesicles. In comparison, no such effects were seen in mice given copper chloride or manganese chloride. The results show that only lead acetate produced a pattern of responses clearly indicative of altered gonadal function.

Effects of nickel chloride on reproduction of the rat and possible antagonistic role of selenium

Nickel (10-100 ppm added as NiCl2) was studied to determine its effects on reproduction of Wistar rats. In nine experimental groups, females, males or both were exposed to nickel in drinking water. In one female group and one male group, the drinking water was also supplemented with 0.3 ppm selenium (added as Na2SeO3). Breeding success and the growth and viability of pups were recorded. Nickel, copper and zinc concentrations in kidneys, liver and skin (with fur) of the females, males and pups were determined with an atomic absorption spectrophotometer. In addition, histology of the male testes (from control and nickel-exposed groups) was studied. The female exposures started 14, 28 or 100 days before copulation and continued during pregnancy and lactation. When the males were exposed (for 28 or 42 days before copulation), NiCl2 reduced both the number of pregnancies and the number of pups born. In the testes, NiCl2 induced shrinkage of the seminiferous tubules, which seemed to close some of the tubules. In the tubules, NiCl2 decreased the number of basal spermatogonia. When the females or both parents were exposed to NiCl2, pup mortality during lactation was high. However, when the females were drinking NiCl2 supplemented with selenium, all the pups survived and development of the total mass of the litters was even better than in the control group. In the same way, in males, selenium supplementation of the drinking water protected those pups that were born; but fertility was lower than with the control treatment. In the tissues studied, nickel accumulated most in the kidneys and then in the liver and skin. In each type of organ, there was a clear dose response relationship. In the pups, in particular, selenium (given to the females) increased the amount of nickel in tissues compared with corresponding administration of nickel without selenium. In summary, selenium seemed to counteract the deleterious effects of NiCl2 on the reproduction of rats.

Detection of genotoxic effects of heavy metal contaminated soils with plant bioassays

Aim of the present study was the development of a bioassay which enables the detection of genotoxic effects of heavy metal contaminated soils. In the first part of the present study, the data base on metal effects in plant bioassays was extended. Four metal salts, namely Cr(VI)O3, Cr(III)Cl3, Ni(II)Cl2 and Sb(III)Cl3 were tested comparatively in MN tests with pollen tetrad cells of Tradescantia clone #4430 and in meristematic root tip cells of Vicia faba. With Cr6+ and Ni2+, clear-cut dose-effects were observed in a range between 0.75 and 10.0 mM, whereas this was not the case with Cr3+ (range tested 1.25-10 mM) and Sb3+ (range 0.30-5.25 mM). In Vicia, negative results were obtained with the four metal salts under all conditions of test. To compare the mutagenic potencies of the metals, the increases of the regression curves (k-values) were calculated, they indicate the number of MN induced per mM in 100 tetrad cells. The corresponding values for Cr6+ and Ni2+ are 0.87 and 1.05, respectively. It appears that the Tradescantia system is in particular sensitive towards those metal species which cause DNA damage in animals and man such as Cr6+, Cd2+, Ni2+, and Zn2+, whereas no clear positive results were obtained with less harmful metal ions such as Cu2+, Cr3+ or Sb3+. In the second part of the study, the mutagenic effects of four metal contaminated soils and two types of standardized leachates (pH 4.0 and pH 7.0) of these soils were tested in Tradescantia and in Vicia. In addition, chemical analyses were carried out to determine the metal concentrations in the soils and in the extracts. Two of the samples contained highly elevated levels of a number of metals (Zn, Pb, Cu, Cd, Sb, As), one soil came from the Central Austrian Alps and contained high As levels only. Direct exposure of the Tradescantia plants in the soils resulted in a drastic increase of the MN frequencies over the background. The lowest effect was seen with the Slovakian soil which contained in particular Sb and As (4.5-fold increase over the background), with the other soils, the induced frequencies were 11-15-fold over the control values. On the contrary, negative results were obtained upon exposure of Tradescantia cuttings in the leachates and upon implantation of germinated Vicia beans in the soils. The results of the present study indicate that Trad-MN assays with direct exposure of intact plants is an appropriate method which enables to detect genotoxic effects of metal contaminated soils in situ. This simple and fast biomonitoring assays might be a valuable supplement to analytical analyses of contaminated soils.

Metal-induced developmental toxicity in mammals: a review

It is well established that certain metals are toxic to embryonic and fetal tissues and can induce teratogenicity in mammals. The main objective of this paper has been to summarize the toxic effects that excesses of certain metals may cause on mammalian development. The reviewed elements have been divided into four groups: (a) metals of greatest toxicological significance (arsenic, cadmium, lead, mercury, and uranium) that are wide-spread in the human environment, (b) essential trace metals (chromium, cobalt, manganese, selenium, and zinc), (c) other metals with evident biological interest (nickel and vanadium), and (d) metals of pharmacological interest (aluminum, gallium, and lithium). A summary of the therapeutic use of chelating agents in the prevention of metal-induced developmental toxicity has also been included. meso-2,3-Dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) have been reported to be effective in alleviating arsenic- and mercury-induced teratogenesis, whereas sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) would protect against vanadium- and uranium-induced developmental toxicity.

Interactions of alpha Ni3S2 with guinea pig alveolar macrophages and liberation of inflammatory mediators

Our previous investigation presented evidence of interaction between alpha Ni3S2 and membranous and cellular lipids of lung cells, resulting in significant increases in linoleic, linolenic and arachidonic acids. The present work was designed to follow the metabolic fate of arachidonic acid in alpha Ni3S2-exposed guinea pig alveolar macrophages (GPAM) in culture (50 microM alpha Ni3S2 for 3 days). The metabolites of arachidonic acid were assessed by HPLC coupled with UV or electrochemical detection. The concentrations of malondialdehyde (MDA), hydroxyeicosatetraenoic acid (HETE), leukotrienes (LT) and reduced glutathione (GSH) were measured. In exposed cells a significant increase of MDA, a breakdown product of lipid peroxidation, was observed. In addition, the enzymatic reduction of 5-hydroperoxyeicosatetraenoic acid (5-HPETE) by the associated oxidation of GSH to GSSG increased 5-HETE in GPAM cells and decreased GSH. 5-Hydroperoxyeicosatetraenoic acid was furthermore converted to epoxides, such as leukotriene A4, and we also quantified in exposed cells a significant increase of its subsequent catabolites LTB4, LTC4 and LTE4. Direct measurements of MDA and other metabolites of arachidonic acid clearly show that exposure of GPAM cells to alpha Ni3S2 enhances lipid peroxidation. This lipid peroxidation is an autocatalytic free-radical process and could be responsible for DNA damage. Furthermore, alpha Ni3S2 intoxication induces the release of proinflammatory products, such as leukotrienes, and the decrease of glutathione.

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.

Biodegradation of orthodontic appliances. Part II. Changes in the blood level of nickel

The purpose of this study is to determine whether orthodontic patients accumulate measurable concentrations of nickel in their blood during their initial course of orthodontic therapy. Blood samples were collected at three different time periods: before the placement of orthodontic appliances, 2 months after their placement, and 4 to 5 months after their placement. The study involved 31 subjects, 18 females and 13 males, who had malocclusions that required the use of a fully banded and bonded edgewise appliance. The age of the subjects in the study ranged between 12 and 38 years. The blood samples were frozen and shipped to a commercial medical laboratory for analysis by atomic absorption spectrophotometry. The three blood samples for each patient were analyzed in succession on the same day to eliminate equipment variance that could occur if blood samples were analyzed on separate days. A total of 93 blood samples were sent for analysis. From the findings in this study the following can be concluded: (1) Patients with fully banded and bonded orthodontic appliances did not show either a significant or consistent increase in nickel blood levels during the first 4 to 5 months of orthodontic therapy. (2) Orthodontic therapy using appliances made of alloys containing nickel-titanium did not result in a significant or consistent increase in the blood levels of nickel. The results obtained from both parts of this investigation indicate that orthodontic appliances used, in their "as-received" condition, corrode in the oral environment releasing both nickel and chromium, in amounts significantly below the average dietary intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutagenicity of soluble and insoluble nickel compounds at the gpt locus in G12 Chinese hamster cells

Nickel is an established human and animal carcinogen, but efforts to demonstrate its mutagenicity in a number of cell types have not been successful. In this report we describe the mutational response to nickel compounds in the G12 cell line, an hprt deficient V79 cell line containing a single copy of the E. coli gpt gene. This cell line has a low spontaneous background, making it suitable for assessment of mutagenic responses to environmental contaminants. When G12 cells were treated with insoluble particles of crystalline nickel sulfide < 5 microns in diameter, a strong, dose-dependent mutagenic response was observed up to 80 times the spontaneous background. Of 48 mutant gpt(-) clones isolated that were induced by insoluble nickel, all were capable of DNA amplification of the gpt sequences by polymerase chain reaction (PCR). The ability to produce full-length PCR products is an indication that large deletions of gene sequences have not occurred. When G12 cells were treated with soluble nickel sulfate, the mutational response was not significantly increased over the spontaneous background. This difference in mutagenic response reflects a large difference in the mutagenic potential of soluble and insoluble nickel compounds, which reflects the carcinogenic potential of these forms of nickel.

Toxicity of some heavy metals in vivo and in vitro in Helianthus annuus

To compare the toxicity of some heavy metals in vivo and in vitro, the effects of six metals, aluminum (Al), cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) were studied in the oil-yielding plant Helianthus annuus. The percentage of seed germination and cytotoxic effects at different concentrations and durations of treatment as well as the growth rate of callus tissues in vitro were compared to ascertain the concentrations that can either support plant growth or cause lethality. Highest toxicity to the plant system was observed from the effects of Pb both at high and low concentrations whereas Zn was the least toxic; and similar effects were seen in vivo and in vitro. The clastogenic effects of Al, Cd, Cu, and Ni were dependent on concentration and length of treatment. Cu and Zn showed less severe cytotoxic damages than Al, Cd, Pb, and Ni. In vitro growth could be supported at 100-1000 times the diluted concentrations of the metals in comparison to in vivo treatment.

Cytogenetic analysis of chromosomal aberrations of peripheral lymphocytes in workers occupationally exposed to nickel

The authors carried out a cytogenetic examination of chromosomal aberrations of peripheral lymphocytes (100 cells evaluated in each sample) with simultaneous monitoring of the level of exposure by means of determination of nickel in the urine, serum and hair. The series included 21 workers occupationally exposed to nickel at two workshops producing NiO (6 persons) and NiSO4 (15 persons) in a chemical plant. At the same time a comparable control group, i.e., 19 workers of the same chemical plant but without any direct occupational nickel exposure (clerks, service men, etc.), were examined in the same way. In the exposed group chromosomal aberrations of peripheral lymphocytes were detected with an average value of 6.41 +/- 1.9% (range 2-14%); in the group producing NiO it was, on the average, 9.5 +/- 3.2% (range 7-14%) whereas in the NiSO4 production workers it was only 5.2 +/- 1.9% (range 2-10%). There was a dependence of chromosomal aberrations of peripheral lymphocytes on the exposure time and on the nickel content of the biological material. Significantly increased values (in contrast to the normal value of chromosomal aberrations of peripheral lymphocytes, up to 2%) were detected in the control group as well (average value of 4.05 +/- 2.27%, range 1-10%). The authors explain this fact by the nickel-polluted environment of the whole observed chemical plant.

Mutagenicity of various chemicals including nickel and cobalt compounds in cultured mouse FM3A cells

Employing a suspension culture of FM3A cells, we examined the cytotoxic and mutagenic effects of various chemical compounds. Mutagenicity of various types of mutagens (MNNG, ENNG, sterigmatocystin, mitomycin C, Trp-P-1, and X-rays) was sensitively detected by this assay. Mutagenicity of Trp-P-2 was detected in the presence of an activating enzyme system. Nickel(II) and cobalt(II) compounds (NiCl2, Ni(CH3COO)2, nickel complex [(C2H5)4N]2 [NiCl4], CoCl2, and a cobalt complex [(C2H5)4N]2-[CoCl4]) were cytotoxic to FM3A cells at concentrations of over 1 X 10(-4) M, and produced 2-6-fold increases of the control in the average number of 6-thioguanine-resistant (6TGr) colonies over a very narrow concentration range of 2-4 X 10(-4) M. Comparison of the mutagenicity of various chemical compounds suggested that some of the nickel(II) and cobalt(II) compounds were very weak mutagens.

Changes in protein phosphorylation in wild-type and nickel-resistant cells and their involvement in morphological elongation

Treatment of wild-type Balb/c-3T3 cells with NiCl2 or N6,2-O-dibutyl-adenosine 3',5'-monophosphate (Bt2-cAMP) resulted in a high degree and frequency of cellular elongation. Nickel-resistant Balb/c-3T3 cells (B200) treated with Bt2-cAMP elongated at the same exposure concentration as wild-type cells. In contrast, treatment of the nickel-resistant cells with both non-cytotoxic and cytotoxic doses of NiCl2 failed to induce elongation. Nickel-resistant cells had two-thirds of the total protein-phosphorylation activity of wild-type cells. Both cAMP and NiCl2 enhanced phosphorylation of specific proteins in intact wild-type cells as detected by 32p autoradiography of these proteins separated on two-dimensional gels. A nickel-dependent phosphorylation of specific proteins is seen following NiCl2 treatment of wild-type cells but was not observed in B200 cells. In contrast, the pattern of Bt2-cAMP-stimulated protein phosphorylation was quite similar in both wild-type and nickel-resistant cells. Although it is unclear at present how nickel ions affect the cellular protein-phosphorylation system, these results suggested that targets controlling cellular elongation are sensitive to nickel, are altered in nickel-resistant cells and appear to involve protein phosphorylation. Further characterization of these targets may help in understanding the mechanisms of nickel carcinogenesis.

Cadmium-induced multistep transformation of cultured Indian muntjac skin fibroblasts

During the past five years we have made a series of cadmium-transformed and resistant fibroblast cell lines by continuous low-level exposure to cadmium. In the present paper we describe the use of four of these lines with varying degrees of transformation to investigate the multistep nature of cadmium carcinogenesis. These include: (a) M cell, an immortal but nontransformed muntjac skin fibroblast line; (b) CCR5, a morphologically transformed and cadmium-resistant line derived from M cells after 20-months continuous exposure to small step-wise increases in cadmium; (c) SCR5, a tumorigenic line derived by selection (in the absence of cadmium) of rapidly growing CCR5 agar colonies; (d) T1, a line derived from an SCR5 tumour growing in a nude mouse. We have compared the morphological characteristics of the four cell lines using light and electron microscopy and evaluated their ability to grow in liquid culture, soft agar and nude mice. We have also examined the changes which have occurred in their cytoskeletons and extracellular matrices using fluorescent antibodies to actin, tubulin and fibronectin and related these to the strength of their cell-cell and cell-substrate attachments and to their levels of transformation and tumorigenesis. We have shown that, while some changes occur in a single step (e.g. intracellular cytoskeletal changes), others are gradual (e.g. changes in extracellular matrix, focus formation and ability to grow in soft agar). We conclude that continuous exposure to low levels of cadmium can initiate growth and structural changes which subsequently lead to cell transformation and tumorigenesis on the removal of cadmium. Though change with cadmium was slow, many of the transformed characteristics are similar to those reported for viral and chemically transformed cells.

Tumorigenicity of nickel subsulfide in Strain A/J mice

The pulmonary tumor response of Strain A mice has been reported to be a rapid and efficient predictor of carcinogenic potential for a variety of chemicals. The route of exposure has usually been by intraperitoneal injection (i.p.) of solubilized materials. We compared intratracheal (i.t.) instillation as a more representative route typical of human exposures, with i.p. injection of nickel subsulfide, a potent animal carcinogen. Animals were sacrificed either 20 weeks after the first dosing, or were held until 45 weeks after the first dosing. Urethane, a positive control, produced a significant increase in pulmonary tumor response after i.t. instillation as well as i.p. injection. For nickel subsulfide treated animals, there was no evidence of a dose-related increase in pulmonary tumor response in any i.p. or i.t. treatment group when compared with age-matched controls.

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.

Nickel sensitivity: effects of prolonged oral intake of the element

25 nickel-sensitive females were given 10 mg NiSO4 in water in a single dose. 18 experienced generalized or localized flare-ups. 15 days later, 17 of the 25 patients were given gradually increasing daily doses of NiSO4 in water for 3 months. 14 ended the trial without flare-up, 3 had to stop because of intense worsening of cutaneous manifestations. A relationship does exist between the daily oral intake of nickel and its clinical manifestations, but it is not uniform and depends on the changing quantities and, above all, on the manner of intake. It would seem that a 10 mg NiSO4 oral challenge represents a sudden and large intake of the element to which the majority of sensitized subjects are not able to adapt. On the other hand, a gradual intake permits a majority of subjects to adapt to the element. We hypothesize that this behaviour is more likely due to intestinal adaptivity than to immunological tolerance.

Investigations on the quantitative determination of nickel and chromium in human lung tissue. Industrial medical, toxicological, and occupational medical expertise aspects

Nickel (Ni) and some of its relatively insoluble compounds as well as chromates may be able to induce cancer in the region of the lungs, as well as in the nose and paranasal sinuses after occupational exposure. Latency periods may amount to 20 years and more. The results of recent investigations have shown that these metals cumulate in the lung tissue after inhalation of relatively insoluble chromium and nickel compounds. The quantitative detection of these heavy metals in samples of pulmonary tissue hence permits the amount of past exposure to be estimated. To establish the normal values, samples of pulmonary tissue from 30 normal subjects were investigated for chromium and nickel content. The samples were taken from different segments and lobes of the lungs, taking topographical anatomical criteria into consideration. In addition, 15 persons who had formerly been exposed to nickel and/or chromium (11 nickel refinery workers, of whom 10 had died of lung cancer, 2 stainless steel welders, 1 foundry worker, 1 electrical technician) were also investigated. From the results of 495 tissue samples from the normal group, median chromium concentrations between 130 and 280 ng/g were calculated, with median nickel concentrations of 20-40 ng/g (wet weight). If these values are related to the nickel concentrations measured in refinery workers, values 112-5,860 times higher were found. The concentrations were about 500 times higher than normal for nickel, and about 60 times higher than normal for chromium in the stainless steel welders. For the foundry workers who died of lung cancer, chromium and nickel concentrations in the normal range were calculated, with the exception of the nickel concentrations in the upper and lower lobes of the right lung. The very high nickel concentrations found in the samples of lung tissue from former nickel refinery workers should be regarded as a guideline with regard to the appraisal of the causal relationship between lung cancer and occupational exposure to relatively insoluble nickel compounds. This result is also supported by epidemiological investigations on this subgroup and must thus be considered etiologically conclusive. For the welders, chromium and nickel concentrations were found that were markedly above normal, but as yet there is no epidemiologically reliable verification for the increased occurrence of malignancies in this occupational group.(ABSTRACT TRUNCATED AT 400 WORDS)

Problems in establishing norm values for nickel and chromium concentrations in human pulmonary tissue

In 15 random autopsies, nickel (Ni) and chromium (Cr) were determined quantitatively by atomic absorption spectrometry (AAS) in human lung tissue to evaluate norm values. None of the deceased persons had had an occupational exposure to Cr or Ni or their compounds. In all, 22 tissue samples were taken from each lung at specific topographical anatomical locations. The analytical procedure is described in detail. The results showed substantial variation in concentrations both within a single lung and also between individuals. Median values found were 204 ng/g for Cr and 25.6 ng/g for Ni. Topographical concentrations of Cr and Ni were 1.3-1.9 times higher in the upper lung areas. In view of the variability in metal concentration, analysis of only one part of lung tissue is not sufficient for determining the content of the entire lung. The evaluation of norm values is an important precondition for appraisal of Cr and Ni accumulation in human pulmonary tissue that may be due to occupational exposure.

Effects of metals on chromosomes of higher organisms

An analysis of the available data on the clastogenic effects of metals and their compounds on higher organisms indicates some general trends. Following chronic exposure to subtoxic doses, a decrease in mitotic frequency and an increase in the number of chromosomal abnormalities are observed. These effects are usually directly proportional to the dose applied and the duration of treatment within the threshold limits. Recovery after acute treatment is inversely related to the dosage. The ultimate expression of the effects depends on certain factors, including the mode and vehicle of administration; the form administered; the test system used; the rate of detoxification, distribution, and retention in the different tissues; and interaction with foreign and endogenous substances as well as the mode of action with the biological macromolecules. In mammals, the clastogenic activity of the metals within each vertical group of the periodic table is directly proportional to the increase in atomic weight, electropositivity, and solubility of the metallic cations in water and lipids, except for Li and Ba. This pattern of inherent cytotoxicity increases with successive periods in the horizontal level. It is enhanced by the formation of covalent and coordinate covalent complexes by heavy metals with the biological macromolecules. In plants, the solubility of the metals in water is of much greater importance. The degree of dissociation of metallic salts and the rate of absorption affect significantly the frequency of chromosomal aberrations. In assessing the effects of environmental metal pollution, the presence of other metals and toxic chemicals and the level of nutrition should be taken into account, since in nature, metals occur in combination and these factors modify the cytotoxic effects to a significant extent.

Cancer risk from inorganics

Inorganic metals and minerals for which there is evidence of carcinogenicity are identified. The risk of cancer from contact with them in the work place, the general environment, and under conditions of clinical (medical) exposure is discussed. The evidence indicates that minerals and metals most often influence cancer development through their action as cocarcinogens. The relationship between the physical form of mineral fibers, smoking and carcinogenic risk is emphasized. Metals are categorized as established (As, Be, Cr, Ni), suspected (Cd, Pb) and possible carcinogens (Table 6), based on the existing in vitro, animal experimental and human epidemiological data. Cancer risk and possible modes of action of elements in each class are discussed. Views on mechanisms that may be responsible for the carcinogenicity of metals are updated and analysed. Some specific examples of cancer risks associated with the clinical use of potentially carcinogenic metals and from radioactive pharmaceuticals used in therapy and diagnosis are presented. Questions are raised as to the effectiveness of conventional dosimetry in accurately measuring risk from radiopharmaceuticals.

Effect of nickel sulfate on cellular proliferation and Epstein-Barr virus antigen expression in lymphoblastoid cell lines

Nickel is found in high levels in the environment of the high-risk areas for nasopharyngeal carcinoma (NPC) of China. Epstein-Barr virus (EBV) is associated with NPC and the interaction of nickel and EBV may be a contributive cofactor to the development of NPC. The study of the in vitro effect of nickel sulfate on cell proliferation and EBV-antigen expression demonstrated that nickel increases cell proliferation of some EBV-positive lymphoblastoid cell lines and increases early antigen expression of Raji cells. Nickel exerted variable effects on viral capsid antigen (VCA): increasing VCA-positive cells in B95-8 cells while decreasing VCA in P3HR-1 cells. It is proposed that the uptake of nickel in NPC high-risk areas could be one of the factors responsible for cancer development in the nasopharynx in China.

Biological monitoring of nickel

Measurements of nickel in body fluids, excreta, and tissues from humans with occupational, environmental, and iatrogenic exposures to nickel compounds are comprehensively reviewed. Correlations between levels of human exposures to various classes of nickel compounds via inhalation, oral, or parenteral routes and the corresponding concentrations of nickel in biological samples are critically evaluated. The major conclusions include the following points: Measurements of nickel concentrations in body fluids, especially urine and serum, provide meaningful insights into the extent of nickel exposures, provided these data are interpreted with knowledge of the exposure routes, sources, and durations, the chemical identities and physical-chemical properties of the nickel compounds, and relevant clinical and physiological information, such as renal function. Nickel concentrations in body fluids should not, at present, be viewed as indicators of specific health risks, except in persons exposed to nickel carbonyl, for whom urine nickel concentrations provide prognostic guidance on the severity of the poisoning. In persons exposed to soluble nickel compounds (e.g., NiCl2, NiSO4), nickel concentrations in body fluids are generally proportional to exposure levels; absence of increased values usually indicates non-significant exposure; presence of increased values should be a signal to reduce the exposure. In persons exposed to less soluble nickel compounds (e.g., Ni3S2,NiO), increased concentrations of nickel in body fluids are indicative of significant nickel absorption and should be a signal to reduce the exposures to the lowest levels attainable with available technology; absence of increased values does not necessarily indicate freedom from the health risks (e.g., cancers of lung and nasal cavities) associated with exposures to certain relatively insoluble nickel compounds.

Mutagenicity of nickel sulphate in Drosophila melanogaster

Nickel sulphate was injected into Drosophila melanogaster males at different concentrations in order to test the chemical for the induction of SLRL and SCL in germ cells. Nickel sulphate induced SLRL at concentrations tested, with the peak of activity at premeiotic and postmeiotic stages. It failed to produce SCL except at the highest concentration tested, where induction of XO males was significant for the pooled data.

Mutagenic effects of some water-soluble metal compounds in a somatic eye-color test system in Drosophila melanogaster

Nickel, cadmium, lead, arsenic, manganese and chromium salts as well as MeHgOH were screened for mutagenicity, using a sensitive somatic eye-color test system in Drosophila melanogaster. The test is based on the insertion of a mobile element which causes instability in the white locus that is somatically enhanced by mutagens. This white locus expression is combined with a mutation, zeste, in another gene, to produce a light yellow eye color. Larval feeding with mutagens causes somatic mutations in the eye imaginal disc cells that develop into easily detectable red spots in the yellow eyes of adult males. Survival tests showed large differences in the toxicity of different metals, but only hexavalent chromium increased the frequency of somatic mutations above the control level. When combined treatments were carried out with MMS and various metals, sodium arsenite caused a reduction of the MMS-induced mutation frequency while methylmercury increased the frequency of somatic spots.

Lack of synergistic effect between arsenic, mercury and ethyl methane sulfonate on the frequency of chromosomal aberrations in mice

The influence of arsenic and mercury on the frequency of chromosome aberrations induced by ethylmethane sulfonate was studied in mice. No synergistic effects could be demonstrated in somatic and germ cells of mice given a combined treatment of arsenic trioxide solution (As2O3, 12 mg per kg body weight) or of mercuric chloride solution (HgCl2, 6 mg per kg body weight) with ethylmethane sulfonate (EMS, 200 mg per kg body weight).

Pulmonary clearance of intratracheally administered 63Ni3S2 in strain A/J mice

The pulmonary clearance of particulate 63Ni3S2 was evaluated in strain A/J mice following the intratracheal instillation of 3 microCi of 63Ni3S2 (1.66 micron, mass median diameter). Lung and tissue burdens were determined from serially sacrificed animals using scintillation counting techniques. Lung clearance over the 35-day observation period could be separated into two distinct components with initial and final phase biological half-times corresponding to 1.2 and 12.4 days, respectively. Radioactivity was detected in the blood, liver, kidney, and femur within 4 hr, and was eliminated at rates comparable to that in the lung. Excretion involved primarily urinary (60% of dose eliminated) but also fecal (40% of dose eliminated) pathways. The data are consistent with the relatively rapid translocation, solubilization, and elimination of particulate 63Ni3S2 from the body.

Recovery of mouse embryos after short-term in vitro exposure to toxic nickel chloride

The development of preimplantation mouse embryos in vitro was adversely affected by the addition of nickel chloride (NiCl2 X 6H2O) to the culture medium. For day 3 (4-8 cell) embryos developmental cessation occurred after 48 h in culture, in NiCl2 X 6H2O-containing medium. However, transfer to NiCl2 X 6H2O-free medium after 5 min, 1 h, and 3 h exposure, resulted in regaining of the developmental capacity for a proportion of the exposed embryos. The in vivo development, in pseudopregnant recipients, of in vitro nickel-exposed embryos was not significantly different from that in control embryos. The results indicated that the effect of NiCl2 X 6H2O on the development of day 3 mouse embryos in vitro was reversible after a short exposure period.

The mutagenic activity of nickel in Corynebacterium sp

Ni2+ ions exhibit a mutagenic effect on the bacterial strain Corynebacterium sp. 887 (hom). The mutagenic activity of the divalent nickel was demonstrated by both the simplified fluctuation test and the so-called clone method. However, when using the clone method and low nickel concentrations the frequency of induced mutants decreases considerably as compared with the control and Ni2+ ions have an antimutagenic effect under these conditions.

Metallic elements in fossil fuel combustion products: amounts and form of emissions and evaluation of carcinogenicity and mutagenicity

Metallic elements contained in coal, oil and gasoline are mobilized by combustion processes and may be emitted into the atmosphere, mainly as components of submicron particles. The information about the amounts, composition and form of metal compounds is reviewed for some fuels and combustion processes. Since metal compounds are always contained in urban air pollutants, they have to be considered whenever an evaluation of biological impact of air pollutants is made. The value of currently used bioassays for the evaluation of the role of trace metal compounds, either as major biologically active components or as modifiers of biological effects of organic compounds is assessed. The whole animal bioassays for carcinogenicity do not seem to be an appropriate approach. They are costly, time-consuming and not easily amenable to the testing of complex mixtures. Some problems related to the application and interpretation of short-term bioassays are considered, and the usefulness of such bioassays for the evaluation of trace metal components contained in complex air pollution mixtures is examined.

Carcinogenesis tests of nickel arsenides, nickel antimonide, and nickel telluride in rats

Carcinogenicity of nickel arsenides (NiAs, Ni11As8, Ni5As2, NiAsS), nickel antimonide (NiSb), and nickel telluride (NiTe) was tested by IM administration to male Fischer rats (14 mg Ni/rat). Three negative control groups received similar IM injections of glycerol vehicle, ferronickel alloy (NiFe), or nickel titanate (NiTiO3); two positive control groups received nickel oxide (NiO) or ferronickel sulfide (Ni4FeS4) at equivalent dosages (14 mg Ni/rat). Within 2 years, the incidences of sarcomas at the injection site were: 0/20 (0%) in NiAs-treated rats, 8/16 (50%) in Ni11As8-treated rats; 17/20 (85%) in Ni5As2-treated rats; 14/16 (85%) in NiAsS-treated rats; 17/29 (59%) in NiSb-treated rats; and 14/26 (54%) in NiTe-treated rats. No local sarcomas occurred in the negative control groups, including 40 glycerol-treated rats, 16 NiFe-treated rats, and 20 NiTiO3-treated rats; in the positive control groups, local sarcomas occurred in 14/15 (93%) of NiO-treated rats and 15/15 (100%) of Ni4FeS4-treated rats. The 99 sarcomas that were induced by the various nickel compounds included 67 rhabdomyosarcomas, 11 fibrosarcomas, 15 osteosarcomas, 1 fibrous histiocytic sarcoma, and 5 undifferentiated sarcomas; metastases were found in 57 sarcoma-bearing rats. This study demonstrates that Ni11As8, Ni5As2, NiAsS, NiSb, and NiTe are carcinogenic for rats. Since Ni11As8, Ni5As2, and NiAsS are likely to be formed during oil shale retorting, environmental contamination by nickel arsenides in spent shale products could conceivably pose a carcinogenic hazard if large-scale production of petroleum from oil share is established.

Application of the in vitro embryo culture to the study of the mutagenic effects of nickel in male germ cells

In vitro embryo cultures were utilized to determine the mechanism of preimplantation loss of embryos derived from matings 3 and 4 weeks after treatment of male Balb/c mice with 56 mg/kg nickel nitrate. Treated and control males were allowed to mate with superovulated females weekly for 5 weeks following treatment, and the number of cleaved eggs as well as development of embryos to blastocysts and implantation were determined. Controls included also males treated with a dose of 40 mg/kg nickel nitrate which previously had been shown to be ineffective in the dominant lethal test. Fertilizing capacity of the spermatozoa as well as development of the cultured embryos were not influenced by a dose of 40 mg/kg nickel nitrate. A dose of 56 mg/kg significantly reduced, the fertilization rate 3 and 4 weeks after treatment but did not affect development of 2-cell embryos. These results demonstrate that the preimplantation loss induced by nickel treatment of males is due to toxic effect on spermatids and spermatogonia and not to a clastogenic action.

Mutagenicity tests with nickel salts in the male mouse

The ability of NiCl2 and Ni(NO3)2 to induce chromosome aberrations in vivo in male mouse has been tested by the micronucleus test and the dominant lethality test. NiCl2 as well as Ni(NO3)2 failed to produce micronuclei in polychromatic erythrocytes whereas cyclophosphamide, used as positive control, raised their incidence markedly. In contrast to the results obtained with cyclophosphamide, NiCl2 and Ni(NO3)2 did not increase the rate of post-implantation death. These compounds decreased significantly, however, the rate of pregnancy as well as the amount of pre-implantation loss. Taking into account also the data in the literature, it is concluded that nickel probably has no clastogenic properties in mammals.