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Cytogenetic analyses of lymphocytes from workers in a nickel refinery
Mutation Research, 103 (1982) 185-190
185
Elsevier BiomedicalPress
Cytogenetic analyses of lymphocytes from workers in a nickel refinery Helga Waksvik I and Morten Boysen2 Departments of GeneticsI and Pathology 2, Norsk Hydro "s Institute for Cancer Research, The Norwegian Radium Hospital and The Norwegian Cancer Society, Montebello, Oslo 3 (Norway)
(Accepted 16 June 1981)
Epidemiological studies show that nickel refinery workers have a high risk of developing lung, sinonasal and laryngeal carcinomas (Pedersen et al., 1973; Sunderman, 1979). Studies in rodents show that certain nickel compounds are carcinogenic after administration by inhalation and parenteral injections. (For review Kazantzis and Lilly, 1979.) The mutagenic effect of various nickel compounds in vitro in several systems has been reported. Exposure of Chinese hamster V79 cells to NiC12 induces mutation at the HPRT locus (Miyaki et al., 1979). During DNA synthesis in E. coli, Ni2÷ increases misincorporation of bases (Miyaki et al., 1977). For FM3A cells from a C3H mouse mammary carcinoma the clastogenic properties of (CH3COOhNi, NiC12, NiS and K2Ni(CN)4 have been reported (Umeda and Nishimura, 1979; Nishimura and Umeda, 1979). In rat-embryo muscle cells the turbagenic properties of NiS have been studied (Swierenga and Basrur, 1968). The question is whether the nickel refinery process may constitute a genetic hazard for the workers. To our knowledge no chromosome studies have previously been performed of workers in nickel refineries. All subjects in this study worked at Falconbridge Nikkelverk, Kristiansand (Norway). Materials and methods
The raw material for nickel production at Falconbridge Nikkelverk is converter matte (about 50% Ni, 30% Cu, 20% S and some trace metals) which is refined through several processes including crushing, roasting, smelting and electrolysis. The workers involved in the first 3 processes are exposed by inhalation mainly to dry dust of heavy water-soluble NiO and Ni3S2 and those involved in the electrolysis process mainly to aerosols of water-soluble NiCI2 and NiSO4. 3 groups of subjects were studied (Tables 1-3). All but one in the control group (Table 3, case 24) were males. All subjects were apparently free of overt virus 0165-7992/82/0000-0000/$02.75 © ElsevierBiomedicalPress
186 TABLE 1 CHROMOSOMAL ABERRATIONS AND SCE MEAN VALUES (~c) IN NICKEL REFINERY WORKERS OCCUPATIONALLY EXPOSED TO NiO AND Ni3S2. AVERAGE AIR CONCENTRATION 0.5 mg Ni/m 3 AIR, RANGE 0.1-1.0 mg Ni/m 3 Subject
Age
Exposure (years)
Plasma conc. of Ni (#g/l)
Chromosomal aberrations (%)
1
23 26 24
7
5
1
2 3
41 54 45
9 6
18 10
2 1
4.5 4.4 5.0
4 5 6
59 25 25
33 7 3
6 4 3
14 17 27
0 1 0
4.8 5.2 4.9
7 8 9
45 60 42
23 29 23
1 1 1
4 7 5
0 1 2
4.8 4.5 4.8
Group average
44.0
21.2
4.2
11.9
0.9
4.8 range 4.4-5.2
Gaps
Breaks
SCE (~-)
TABLE 2 CHROMOSOMAL ABERRATIONS AND SCE MEAN VALUES (J) IN NICKEL REFINERY WORKERS OCCUPATIONALLY EXPOSED TO NiO AND Ni3S2. AVERAGE AIR CONCENTRATION 0.2 mg/m3 AIR; RANGE 0.1-0.5 mg Ni/rn3 Subject
Age
Exposure (years)
Plasma conc. of Ni 0zg/l)
Chromosomal aberrations (%)
SCE (~-)
Gaps
Breaks
30 4 failed
1 1 failed
4.8 5.1 4.9
10 11 12
57 48 50
29 26 31
4 12 3
13 14 15 16
46 55 55 55
8 25 22 26
4 4 5 5
23 17 18 30
1 1 2 3
4.4 4.7 4.9 5.3
17 18 19
55 45 52
31 28 26
4 4 7
5 23 15
1 0 2
4.8 4.4 4.8
Group average
51.8
25.2
5.2
18.3
1.3
4.9 range 4.4-5.3
disease and none was known to suffer from cancer when the blood sample was drawn. Only non-smokers, non-alcohol consumers and subjects without regular use o f drugs were selected. T h e g r o u p s were u n i f o r m as to p r e v i o u s e x p o s u r e to diagnostic X-rays, and none had received any form of therapeutic irradiation.
187
TABLE 3 C H R O M O S O M A L A B E R R A T I O N S A N D SCE M E A N VALUES (J') IN SUBJECTS E M P L O Y E D IN OFFICES A T T H E N I C K E L REFINERY ( C O N T R O L G R O U P )
Subject
Age
E m p l o y - Plasmac o n c . ment of Ni 0~g/l) (years)
Chromosomalaberrations (°70) Gaps
Breaks
SCE (k-)
20 21 22 23 24 25 26
47 59 48 44 48 53 59
14 33 29 27 3 13 29
1 1 1 1 1 1 1
3 3 4 5 3 3 4
1 0 1 0 1 1 0
4.8 5.8 4.4 6.3 4.9 4.7 5.0
Group average
51.2
21.1
1
3.7
0.6
5.1 range 4 . 4 - 6 . 3
Blood samples were taken into heparinized tubes and chilled to + 4°C during the transport to Oslo. Whole blood cultures were established in Ham's F-10 medium supplemented with fetal bovine serum as previously reported (Waksvik et al., 1981a). Chromosomal aberrations were studied in cells cultured for 48 h; 100 metaphases were analyzed for each subject and scored for gaps (achromatic lesions), breaks and exchanges. An aberration was scored as a break only when the distal part of the chromatid was dislocated. Sister-chromatid exchange (SCE) was scored in cells labeled wich BrdU (5-bromo-2'-deoxyuridine, 5/~g/ml) and cultured for 2 cell cycles with BrdU. The chromosome analyses were performed without access to other information than the name of the subject. The SCE value for each subject is given as the mean of 30 counted metaphases. The non-parametric Wilcoxon 2-sample rank sum test (Hollander and Wolfe, 1973) was applied to compare means. The nickel concentrations in plasma and the occupational atmosphere were measured (Andersen et al., 1978) in an atomic absorption spectrophotometer equipped with a graphite furnace and recorder (Perkin Elmer Corp., Norwalk, CT). Results and discussion
In each of the 2 groups of workers at the nickel refinery the increase in gaps was statistically significant (P < 0.003) compared with the control group (Tables 1-3). In experiments in vitro, gaps are induced in human lymphocytes by agents that crosslink the 2 complementary DNA strands (Bragger, 1974; Waksvik et al., 1977), react with one of the DNA strands (Bragger, 1974) or denature proteins by breaking S - S bonds (Bragger and Waksvik, 1978).
188
The increase of gaps in the group mainly exposed to NiO and Ni3S2 points to these compounds as a possible cause. Both compounds are known to be carcinogens (IARC, 1976). However, Paton and Allison (1972) found no chromosomal aberrations in human lymphocytes treated in vitro with NiO. It is not clear whether the cells had a significant exposure to the insoluble compound as no doses or toxicity are given. The mitotic abnormalities seen in rat-embryo muscle cells treated in vitro with Ni3S2 may be due to the possibility that nickel interferes with the sulfhydryl groups involved in the spindle mechanism (Swierenga and Basrur, 1968). NiCl2 and NiSO4 do not seem to induce tumors in experimental animals (for review, Kazantzis and Lilly, 1979) whereas the incidence of malignant tumors of the respiratory tract in workers exposed mainly to these compounds is increased (Pedersen et al., 1973). In mutagenicity tests with Salmonella typhimurium, NiCI2 gave negative results, and NiSO4 was toxic but not mutagenic to intracellular bacteriophage T4 in E. coli (Kazantzis and Lilly, 1979). The difference in the percentage of gaps between the 2 groups of nickel workers was not statistically significant. No statistically significant relation between the increase of gaps and plasma nickel concentrations, time of exposure or age of the subjects was found. Breaks did not differ significantly from the controls, and exchanges were not found. In experiments in vitro the inducibility of chromosomal aberrations by nickel compounds may be time-related. In FM3A cells from a C3H mouse mammary carcinoma, Umeda and Nishimura (1979) found that treatment with NiC12 and (CH3COO)ENi induced few chromosomal aberrations, NiS induced a low but definite increase and K2Ni(CN)4 induced only gaps. The difference in the inducibility of chromosomal aberrations was related neither to difference in the solubilities of the nickel compounds nor difference in the amount of nickel incorporated into cells (Nishimura and Umeda, 1979). However, after treated cells had been washed and re-incubated in the control medium the cells showed chromosomal aberrations consisting not only of gaps but also of breaks and exchanges, and Nishimura and Umeda suggest a time relation. We found no increase of the mean SCE value in the groups of nickel workers compared with the control group. In vitro, SCE can be induced by mutagens/carcinogens (Perry and Evans, 1975) and the SCE test has been widely used as a short-term method, but for mutagen/carcinogen exposure in vivo, SCE has given ambiguous results. Treatment of human lymphocytes in vitro with high concentration of Ni3S2 leads to a marginal, not dose-dependent, increase of SCE (Saxholm et al., 1981). The mean age is not the same in all groups. Ranking for age does not give the same sequence as ranking for chromosomal aberrations. Age dependency of SCE among adults has been found (Waksvik et al., 1981b). Environmental factors other than occupational may influence the chromosome parameters. As far as possible we have eliminated such factors from our material. Care was taken to evaluate whether
189 the s u b j e c t s i n v e s t i g a t e d h a d r e c e n t l y u n d e r g o n e d i a g n o s t i c o r t h e r a p e u t i c i r r a d i a t i o n o r h a d s u f f e r e d f r o m virus diseases. P e r s o n a l h a b i t s such as s m o k i n g , a l c o h o l c o n s u m p t i o n a n d d r u g i n t a k e were also c o n s i d e r e d . In o u r m a t e r i a l it seems r e a s o n a b l e to a s s u m e t h a t d i f f e r e n c e s in t h e c h r o m o s o m a l p a r a m e t e r s are d u e to the w o r k i n g c o n d i t i o n s . A l t h o u g h nickel c o m p o u n d s a r e p r o b a b l y the m a i n m u t a g e n i c agents, nickel r e f i n e r y w o r k e r s a r e also e x p o s e d to several o t h e r m e t a l s a n d p o s s i b l e u n i d e n t i f i e d agents t h a t m a y be i m p o r t a n t . W e c o n c l u d e t h a t g a p s m a y b e a useful p a r a m e t e r in the m o n i t o r i n g o f p o p u l a t i o n s e x p o s e d to m u t a g e n s / c a r c i n o g e n s . T h e c h r o m o s o m a l a l t e r a t i o n s s h o w n b y the increase o f g a p s s h o w t h a t the nickel r e f i n e r y process m a y c o n s t i t u t e a genetic h a z a r d at least to s o m a t i c cells.
Acknowledgements W e t h a n k Dr. A r n e H 0 g e t v e i t , F a l c o n b r i d g e N i k k e l v e r k , for p r o c u r i n g subjects for this study. T h e t e c h n i c a l assistance o f R e i d u n N o r u m is g r e a t l y a p p r e c i a t e d .
References Andersen, I., W.Torjussen and H. Zachariasen (1978) Analysis for nickel in plasma and urine by electrothermal atomic absorption spectrometry, with sample preparation by protein precipitation, Clin. Chem., 24, 1198-1202. Br0gger, A. (1974) Caffeine induced enhancement of chromosome damage in human lymphocytes treated with methyl methanesulphonate, mitomycin C and X-rays, Mutation Res., 23,353-360. Br0gger, A., and H. Waksvik (1978) Further evidence that the chromatid gap is a folding defect, Hereditas, 89, 131-132. Hollander, M., and D.A. Wolfe (1973) Nonparametric statistical methods, Wiley, New York. IARC (1976) Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man, IARC, Lyon, Vol. 11. Kazantzis, G., and L. Lilly (1979) Mutagenic and carcinogenic effects of metals, in: L. Friberg, G.F. Nordberg and V.B. Vouk (Eds.), Handbook on the Toxicology of Metals, Elsevier, Amsterdam, pp. 237-272. Miyaki, M., I. Murata, M. Osabe and T. Ono (1977) Effect of metal cations on misincorporation by E. coli DNA polymerases, Biochem. Biophys, Res. Commun., 77,854-860. Miyaki, M., N. Akamatsu, T. Ono and H. Koyama (1979) Mutagenicity of metal cations in cultured cells from Chinese hamster, Mutation Res., 68,259-263. Nishimura, M., and M. Umeda (1979) Induction of chromosomal aberrations in cultured mammalian cells by nickel compounds, Mutation Res., 68,337-349. Paton, G.R., and A.C. Allison (1968) Chromosome damage in human cell cultures induced by metal salts, Mutation Res., 16, 332-336. Pedersen, E.A., C. H0getveit and A. Andersen (1973) Cancer of respiratory organs among workers at a nickel refinery in Norway, Int. J. Cancer, 12, 32-41. Perry, P., and H.J. Evans (1975) Cytological detection of mutagen-carcinogen exposure by sister chromatid exchange, Nature (London), 258, 121-125. Saxholm, H.J.K., A. Reith and A. Br0gger 0981) Oncogenic transformation and cell lysis in the C3H/10TV2 cells and increasedsister chromatid exchange in human lymphocytes by nickel subsulphide, Cancer Res., 41, 4136-4139.
190 Sunderman Jr., F.W. (1979) Carcinogenicity and anticarcinogenicity of metal compounds, in: P. Emmelot and E. Kriek (Eds.), Environmental Carcinogenesis, Elsevier, Amsterdam, pp. 165-192. Swierenga, S.H.H., and P.K. Basrur (1968) Effect of nickel on cultured rat embryo muscle cells, Lab. Invest., 19, 663-674. Umeda, M., and M. Nishimura (1979) Inducibility of chromosomal aberrations by nickel compounds in cultured mammalian cells, Mutation Res., 67, 221-229. Waksvik, H., A. Bregger and J. Stene (1977) Psoralen/UVA treatment and chromosomes, I. Aberrations and sister chromatid exchange in human lymphocytes in vitro and synergism with caffeine, Hum. Genet., 38, 195-207. Waksvik, H., O. Klepp and A. Bregger (1981a) Chromosome analyses of nurses handling cytostatic agents, Cancer. Treat. Rep., 65,607-610. Waksvik, H., P. Magnus and K. Berg (1981b) Effects of age, sex and genes on sister chromatid exchange, Clin. Genet., 20, in press.
185
Elsevier BiomedicalPress
Cytogenetic analyses of lymphocytes from workers in a nickel refinery Helga Waksvik I and Morten Boysen2 Departments of GeneticsI and Pathology 2, Norsk Hydro "s Institute for Cancer Research, The Norwegian Radium Hospital and The Norwegian Cancer Society, Montebello, Oslo 3 (Norway)
(Accepted 16 June 1981)
Epidemiological studies show that nickel refinery workers have a high risk of developing lung, sinonasal and laryngeal carcinomas (Pedersen et al., 1973; Sunderman, 1979). Studies in rodents show that certain nickel compounds are carcinogenic after administration by inhalation and parenteral injections. (For review Kazantzis and Lilly, 1979.) The mutagenic effect of various nickel compounds in vitro in several systems has been reported. Exposure of Chinese hamster V79 cells to NiC12 induces mutation at the HPRT locus (Miyaki et al., 1979). During DNA synthesis in E. coli, Ni2÷ increases misincorporation of bases (Miyaki et al., 1977). For FM3A cells from a C3H mouse mammary carcinoma the clastogenic properties of (CH3COOhNi, NiC12, NiS and K2Ni(CN)4 have been reported (Umeda and Nishimura, 1979; Nishimura and Umeda, 1979). In rat-embryo muscle cells the turbagenic properties of NiS have been studied (Swierenga and Basrur, 1968). The question is whether the nickel refinery process may constitute a genetic hazard for the workers. To our knowledge no chromosome studies have previously been performed of workers in nickel refineries. All subjects in this study worked at Falconbridge Nikkelverk, Kristiansand (Norway). Materials and methods
The raw material for nickel production at Falconbridge Nikkelverk is converter matte (about 50% Ni, 30% Cu, 20% S and some trace metals) which is refined through several processes including crushing, roasting, smelting and electrolysis. The workers involved in the first 3 processes are exposed by inhalation mainly to dry dust of heavy water-soluble NiO and Ni3S2 and those involved in the electrolysis process mainly to aerosols of water-soluble NiCI2 and NiSO4. 3 groups of subjects were studied (Tables 1-3). All but one in the control group (Table 3, case 24) were males. All subjects were apparently free of overt virus 0165-7992/82/0000-0000/$02.75 © ElsevierBiomedicalPress
186 TABLE 1 CHROMOSOMAL ABERRATIONS AND SCE MEAN VALUES (~c) IN NICKEL REFINERY WORKERS OCCUPATIONALLY EXPOSED TO NiO AND Ni3S2. AVERAGE AIR CONCENTRATION 0.5 mg Ni/m 3 AIR, RANGE 0.1-1.0 mg Ni/m 3 Subject
Age
Exposure (years)
Plasma conc. of Ni (#g/l)
Chromosomal aberrations (%)
1
23 26 24
7
5
1
2 3
41 54 45
9 6
18 10
2 1
4.5 4.4 5.0
4 5 6
59 25 25
33 7 3
6 4 3
14 17 27
0 1 0
4.8 5.2 4.9
7 8 9
45 60 42
23 29 23
1 1 1
4 7 5
0 1 2
4.8 4.5 4.8
Group average
44.0
21.2
4.2
11.9
0.9
4.8 range 4.4-5.2
Gaps
Breaks
SCE (~-)
TABLE 2 CHROMOSOMAL ABERRATIONS AND SCE MEAN VALUES (J) IN NICKEL REFINERY WORKERS OCCUPATIONALLY EXPOSED TO NiO AND Ni3S2. AVERAGE AIR CONCENTRATION 0.2 mg/m3 AIR; RANGE 0.1-0.5 mg Ni/rn3 Subject
Age
Exposure (years)
Plasma conc. of Ni 0zg/l)
Chromosomal aberrations (%)
SCE (~-)
Gaps
Breaks
30 4 failed
1 1 failed
4.8 5.1 4.9
10 11 12
57 48 50
29 26 31
4 12 3
13 14 15 16
46 55 55 55
8 25 22 26
4 4 5 5
23 17 18 30
1 1 2 3
4.4 4.7 4.9 5.3
17 18 19
55 45 52
31 28 26
4 4 7
5 23 15
1 0 2
4.8 4.4 4.8
Group average
51.8
25.2
5.2
18.3
1.3
4.9 range 4.4-5.3
disease and none was known to suffer from cancer when the blood sample was drawn. Only non-smokers, non-alcohol consumers and subjects without regular use o f drugs were selected. T h e g r o u p s were u n i f o r m as to p r e v i o u s e x p o s u r e to diagnostic X-rays, and none had received any form of therapeutic irradiation.
187
TABLE 3 C H R O M O S O M A L A B E R R A T I O N S A N D SCE M E A N VALUES (J') IN SUBJECTS E M P L O Y E D IN OFFICES A T T H E N I C K E L REFINERY ( C O N T R O L G R O U P )
Subject
Age
E m p l o y - Plasmac o n c . ment of Ni 0~g/l) (years)
Chromosomalaberrations (°70) Gaps
Breaks
SCE (k-)
20 21 22 23 24 25 26
47 59 48 44 48 53 59
14 33 29 27 3 13 29
1 1 1 1 1 1 1
3 3 4 5 3 3 4
1 0 1 0 1 1 0
4.8 5.8 4.4 6.3 4.9 4.7 5.0
Group average
51.2
21.1
1
3.7
0.6
5.1 range 4 . 4 - 6 . 3
Blood samples were taken into heparinized tubes and chilled to + 4°C during the transport to Oslo. Whole blood cultures were established in Ham's F-10 medium supplemented with fetal bovine serum as previously reported (Waksvik et al., 1981a). Chromosomal aberrations were studied in cells cultured for 48 h; 100 metaphases were analyzed for each subject and scored for gaps (achromatic lesions), breaks and exchanges. An aberration was scored as a break only when the distal part of the chromatid was dislocated. Sister-chromatid exchange (SCE) was scored in cells labeled wich BrdU (5-bromo-2'-deoxyuridine, 5/~g/ml) and cultured for 2 cell cycles with BrdU. The chromosome analyses were performed without access to other information than the name of the subject. The SCE value for each subject is given as the mean of 30 counted metaphases. The non-parametric Wilcoxon 2-sample rank sum test (Hollander and Wolfe, 1973) was applied to compare means. The nickel concentrations in plasma and the occupational atmosphere were measured (Andersen et al., 1978) in an atomic absorption spectrophotometer equipped with a graphite furnace and recorder (Perkin Elmer Corp., Norwalk, CT). Results and discussion
In each of the 2 groups of workers at the nickel refinery the increase in gaps was statistically significant (P < 0.003) compared with the control group (Tables 1-3). In experiments in vitro, gaps are induced in human lymphocytes by agents that crosslink the 2 complementary DNA strands (Bragger, 1974; Waksvik et al., 1977), react with one of the DNA strands (Bragger, 1974) or denature proteins by breaking S - S bonds (Bragger and Waksvik, 1978).
188
The increase of gaps in the group mainly exposed to NiO and Ni3S2 points to these compounds as a possible cause. Both compounds are known to be carcinogens (IARC, 1976). However, Paton and Allison (1972) found no chromosomal aberrations in human lymphocytes treated in vitro with NiO. It is not clear whether the cells had a significant exposure to the insoluble compound as no doses or toxicity are given. The mitotic abnormalities seen in rat-embryo muscle cells treated in vitro with Ni3S2 may be due to the possibility that nickel interferes with the sulfhydryl groups involved in the spindle mechanism (Swierenga and Basrur, 1968). NiCl2 and NiSO4 do not seem to induce tumors in experimental animals (for review, Kazantzis and Lilly, 1979) whereas the incidence of malignant tumors of the respiratory tract in workers exposed mainly to these compounds is increased (Pedersen et al., 1973). In mutagenicity tests with Salmonella typhimurium, NiCI2 gave negative results, and NiSO4 was toxic but not mutagenic to intracellular bacteriophage T4 in E. coli (Kazantzis and Lilly, 1979). The difference in the percentage of gaps between the 2 groups of nickel workers was not statistically significant. No statistically significant relation between the increase of gaps and plasma nickel concentrations, time of exposure or age of the subjects was found. Breaks did not differ significantly from the controls, and exchanges were not found. In experiments in vitro the inducibility of chromosomal aberrations by nickel compounds may be time-related. In FM3A cells from a C3H mouse mammary carcinoma, Umeda and Nishimura (1979) found that treatment with NiC12 and (CH3COO)ENi induced few chromosomal aberrations, NiS induced a low but definite increase and K2Ni(CN)4 induced only gaps. The difference in the inducibility of chromosomal aberrations was related neither to difference in the solubilities of the nickel compounds nor difference in the amount of nickel incorporated into cells (Nishimura and Umeda, 1979). However, after treated cells had been washed and re-incubated in the control medium the cells showed chromosomal aberrations consisting not only of gaps but also of breaks and exchanges, and Nishimura and Umeda suggest a time relation. We found no increase of the mean SCE value in the groups of nickel workers compared with the control group. In vitro, SCE can be induced by mutagens/carcinogens (Perry and Evans, 1975) and the SCE test has been widely used as a short-term method, but for mutagen/carcinogen exposure in vivo, SCE has given ambiguous results. Treatment of human lymphocytes in vitro with high concentration of Ni3S2 leads to a marginal, not dose-dependent, increase of SCE (Saxholm et al., 1981). The mean age is not the same in all groups. Ranking for age does not give the same sequence as ranking for chromosomal aberrations. Age dependency of SCE among adults has been found (Waksvik et al., 1981b). Environmental factors other than occupational may influence the chromosome parameters. As far as possible we have eliminated such factors from our material. Care was taken to evaluate whether
189 the s u b j e c t s i n v e s t i g a t e d h a d r e c e n t l y u n d e r g o n e d i a g n o s t i c o r t h e r a p e u t i c i r r a d i a t i o n o r h a d s u f f e r e d f r o m virus diseases. P e r s o n a l h a b i t s such as s m o k i n g , a l c o h o l c o n s u m p t i o n a n d d r u g i n t a k e were also c o n s i d e r e d . In o u r m a t e r i a l it seems r e a s o n a b l e to a s s u m e t h a t d i f f e r e n c e s in t h e c h r o m o s o m a l p a r a m e t e r s are d u e to the w o r k i n g c o n d i t i o n s . A l t h o u g h nickel c o m p o u n d s a r e p r o b a b l y the m a i n m u t a g e n i c agents, nickel r e f i n e r y w o r k e r s a r e also e x p o s e d to several o t h e r m e t a l s a n d p o s s i b l e u n i d e n t i f i e d agents t h a t m a y be i m p o r t a n t . W e c o n c l u d e t h a t g a p s m a y b e a useful p a r a m e t e r in the m o n i t o r i n g o f p o p u l a t i o n s e x p o s e d to m u t a g e n s / c a r c i n o g e n s . T h e c h r o m o s o m a l a l t e r a t i o n s s h o w n b y the increase o f g a p s s h o w t h a t the nickel r e f i n e r y process m a y c o n s t i t u t e a genetic h a z a r d at least to s o m a t i c cells.
Acknowledgements W e t h a n k Dr. A r n e H 0 g e t v e i t , F a l c o n b r i d g e N i k k e l v e r k , for p r o c u r i n g subjects for this study. T h e t e c h n i c a l assistance o f R e i d u n N o r u m is g r e a t l y a p p r e c i a t e d .
References Andersen, I., W.Torjussen and H. Zachariasen (1978) Analysis for nickel in plasma and urine by electrothermal atomic absorption spectrometry, with sample preparation by protein precipitation, Clin. Chem., 24, 1198-1202. Br0gger, A. (1974) Caffeine induced enhancement of chromosome damage in human lymphocytes treated with methyl methanesulphonate, mitomycin C and X-rays, Mutation Res., 23,353-360. Br0gger, A., and H. Waksvik (1978) Further evidence that the chromatid gap is a folding defect, Hereditas, 89, 131-132. Hollander, M., and D.A. Wolfe (1973) Nonparametric statistical methods, Wiley, New York. IARC (1976) Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man, IARC, Lyon, Vol. 11. Kazantzis, G., and L. Lilly (1979) Mutagenic and carcinogenic effects of metals, in: L. Friberg, G.F. Nordberg and V.B. Vouk (Eds.), Handbook on the Toxicology of Metals, Elsevier, Amsterdam, pp. 237-272. Miyaki, M., I. Murata, M. Osabe and T. Ono (1977) Effect of metal cations on misincorporation by E. coli DNA polymerases, Biochem. Biophys, Res. Commun., 77,854-860. Miyaki, M., N. Akamatsu, T. Ono and H. Koyama (1979) Mutagenicity of metal cations in cultured cells from Chinese hamster, Mutation Res., 68,259-263. Nishimura, M., and M. Umeda (1979) Induction of chromosomal aberrations in cultured mammalian cells by nickel compounds, Mutation Res., 68,337-349. Paton, G.R., and A.C. Allison (1968) Chromosome damage in human cell cultures induced by metal salts, Mutation Res., 16, 332-336. Pedersen, E.A., C. H0getveit and A. Andersen (1973) Cancer of respiratory organs among workers at a nickel refinery in Norway, Int. J. Cancer, 12, 32-41. Perry, P., and H.J. Evans (1975) Cytological detection of mutagen-carcinogen exposure by sister chromatid exchange, Nature (London), 258, 121-125. Saxholm, H.J.K., A. Reith and A. Br0gger 0981) Oncogenic transformation and cell lysis in the C3H/10TV2 cells and increasedsister chromatid exchange in human lymphocytes by nickel subsulphide, Cancer Res., 41, 4136-4139.
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