(CANCER RESEARCH55, 5251-5256, November 15, 19951
Comparative Carcinogenic Effects of Nickel Subsulfide, Nickel Oxide, or Nickel
Sulfate Hexahydrate Chronic Exposures in the Lung1
June K. Dunnick,2 Michael R. Elwell, Ann E. Radovsky, Janet M. Benson, Fletcher F. Hahn, Kristan J. Nikula,
Edward B. Barr, and Charles H. Hobbs
National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709 (J. K. D., M. R. E., A. E. R.j. and Lovelace inhalation Toxicology Research
Institute, Albuquerque. New Mexico 87185 Ii. M. B., F. F. H., K. J. N., E. B. B., C. H. H.]
ABSTRACT
The relative toxicity and carcinogenicity of nickel sulfate hexahydrate
(NiSO4@6H2O),nickel subsulfide (Ni@S2),and nickel oxide (N1O) were
studied in F344/N rats and B6C3F1 mice after inhalation exposure for 6
h/day, 5 days/week, for 2 years. Nickel subsultlde (0.15 and 1 mg/rn3) and
nickel oxide (1.25 and 2.5 mg/rn3) caused an exposure-related
Increased
incidence of alveolar/bronchiolar neoplasms and adrenal medulla neo
pla.stns in male and female rats. Nickel oxide caused an equivocal expo
sure-related
increase
in alveolar/bronchiolar
neoplasms
in female
mice.
No exposure-related neoplastic responses occurred in rats or mice exposed
to nickel sulfate or in mice exposed to nickel subsulfide. These findings are
consistent with results from other studies, which show that nickel subsul
tide and nickel oxide reach the nucleus in greater
amounts
than the do
water-soluble nickel compounds such as nickel sulfate. It has been pro
posed that the more water-insoluble particles are phagocytized, whereas
the vacuoles containing nickel migrate to the nuclear membrane, where
they release nickel ions that effect DNA damage. The findings from these
experimental studies show that chronic exposure to nickel can cause lung
neoplasms
in rats,
and that
this response
is related
to exposure
that have shown an association between nickel exposure and cancer
(5, 6).
We have previously reported the results of inhalation toxicity
studies to nickel compounds commonly found in the workplace,
including nickel subsulfide, nickel oxide, or nickel sulfate. The nickel
oxide used in these studies was “high-temperature―
nickel oxide, a
type of nickel that may be formed during high-temperature operations
such as in the stainless steel industry. In the P344 rat and B6C3F1
mouse, the major toxicity occurs in the lung after exposures to these
nickel compounds. Nickel sulfate caused lung toxicity at lower expo
sure concentrations than did nickel subsulfide or nickel oxide (7).
Comparisons of the carcinogenic effects between nickel compounds
and differences in responses between rats and mice are described in
this paper, and information is provided for comparing results in
experimental models with those in humans.
MATERIALS
AND METHODS
to specific
types of nickel compounds.
Chemicals. Nickel subsulfide (a Ni3S2;MW, 240.2; CAS No. 12035-72-2)
and nickel oxide (NiO; green oxide, CalCined at 1350°C;MW, 74.7; CAS No.
1313-99-1)
INTRODUCTION
were
supplied
by the International
Nickel
Co.,
Ltd.
(Toronto,
Canada). Nickel sulfate hexahydrate (NiSO4@6H20;referred to as nickel sal
fate; MW, 262.9; CAS No. 10101-97-0) was obtained from Aldrich Chemical
Co. (Milwaukee, WI). Elemental analysis conducted on these compounds by
the Midwest Research Institute indicated overall purifies of 97—99%
(8—10).
The range of mass median aerodynamic diameters and o@obtained throughout
the study of Ni3S2,NiO, and NiSO4-6H20 were 2.0—2.2 @m
(@52.0), 2.22.5
p.m ([email protected]), and 2.2—2.5
gun ([email protected]), respectively.
Aerosol Characteristics. The exposure systems and methods for aerosol
generation and characterization have been described previously (8—10).The
animals were exposed in Hazieton 1000 (mice) and Hazleton 2000 (rats)
In 1932, the British Chief Inspector for Factories and Workshops
reported an increase in respiratory tract cancer in workers in the nickel
refinery in Wales (1). Further evidence that some hazard in the nickel
refinery caused these cancers was published some 25 years later, and
excess risks for respiratory cancer have been reported in other nickel
industries in Canada, Norway, and Russia (2, 3). Nickel is primarily
imported into the United States, where it is used in various industrial
processes including fabrication of metal products, metal plating, and
whole-body
chambers
(Lab Products,
Inc., Maywood,
NJ) for 6 h/day, 5
chemical and electric industries (4).
days/week,
for
102
weeks.
Ni3S2
and
NiO
aerosols
were
generated using 2'
Cohorts of nickel-exposed workers continue to be studied to deter
mine the parts and exposures of the refining processes that produce an and 4' fluid bed generators, respectively. Nickel sulfate aerosols were gener
ated by nebulization of nickel sulfate solutions. Aerosol concentration was
increased risk for cancer. However, it has not been possible to char
determined by taking three 2-h filter samples throughout the exposure day.
acterize specific risks from nickel exposures because exposures may
Real-time determination of aerosol concentration was made using real time
be multiple, including exposures to multiple nickel compounds, to aerosol monitor—modelS units. Aerosol size was determined using cascade
other chemicals in the workplace, or to cigarette smoke or alcohol.
impactors.
Many of the studies that have found an association between nickel
Experimental Design. Core groups of 50 male and 50 female F344 rats
exposures and lung and/or nasal cancer have focused on “high-risk―(Taconic Farms, Germantown, NY) and 50 male and 50 female B6C3F1 mice
(Simonsen Laboratories, Giroy, CA) were exposed to nickel sulfate hexahy
cohorts. However, cancer was not found in all groups of exposed
drate, nickel subsulfide, or nickel oxide for 6 h/day, five days/week, for 2 years
nickel workers (5, 6). Excess mortality from nonmalignant respiratory
(Table 1).
effects or other disease have not been seen in epidemiological studies
The high exposure concentrations for nickel oxide and nickel sulfate were
selected
Received 6/16/95; accepted 9/18195.
The costs of publication of this article were defrayed in part by the payment of page
based on the minimal
to mild inflammatory
lung lesions
observed
in
the 13-week toxicity studies (7). In the nickel subsuifide study, the high
charges. This article must therefore be hereby marked advertisement in accordance with
18 U.S.C. Section 1734 solely to indicate this fact.
exposure
I This researchwas conductedunderInteragencyAgreementY0i-ES-30108 between
the National Institutes of Environmental Health Sciences and the United States Depart
on the severity of inflammatory lung lesions in the 13-week studies, which
corresponded to that observed in the high exposure level selected for the 2-year
ment of Energy. The in-life phase of the study was conducted at the Inhalation Toxicology
Research Institute which is operated for the United States Department of Energy under
contract DE-ACO4-76EV01013. The facilities used for this research were fully accredited
by the American Association for the Accreditation of Laboratory Animal Care.
2 To
whom
requests
for
reprints
should
be
addressed,
at
National
Institute
of
ronmental Health Sciences, Research Triangle Park, NC 27709.
3 The
abbreviations
lar; it., intratracheal.
used
are:
o@,
approximate
geometric
SD;
A/B,
alveolar/bronchio
Envi
concentration
nickel subsulfide
nickel
(1 mg/m3)
corresponded
to that used
study (11). The 0.15 mg/m3 concentration
oxide and nickel
sulfate
hexahydrate
in a previous
was selected
based
studies.
Additional animals were added for lung burden determinations at 7 or 15
months. Atomic absorption spectroscopy was used for determining nickel
burdens in the lung according to methods described previously (12).
Food (NIH-07 CertifIed Diet; Ziegler Brothers, Inc., Gardners, PA) was
provided during nonexposure periods. Water was provided ad libitum. A 12-h
5251
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CARCINOGENIC EFFECTS OF NICKEL EXPOSURE IN ThE LUNG
Table 1 Exposure level of nickel compound (or nickel; mg/rn3) in 2-year studies―
nickel subsulfide-exposed rats relative to controls were increased
more than in mice and correlated with a more severe inflammatory
and toxic response in the lung of rats at the exposure concentrations
Nickel sulfate hexahydrate (22.3% nickel)
Rats
0
Compound
0.125
0
Nickel
0.25
0.03
0.06
0.5
0.1 1
0
0
Nickel subsulfide (73.3% nickel)
Rats
Compound
Nickel
0.25
0.06
0.5
0.11
1.0
0.22
2-year
nickel oxide studies
.
0
0.15
1
toxic
Mice
Compound
0
0.11
0.73
at exposure
0
0.6
1.2
has been reported
Nickel
0
0.44
0.9
At 15-months,
0
0
Nickel
0 62
Mice
Compound
1 25
limit
25
2.0
values:
1 mg
NiJm3;
0.1
mg
NiJm3
(soluble
5.0
than
in mice
nickels).
nickel
subsulfide
or nickel
concentrations
and
oxide,
causing
death
of animals
of 2 mg/m3 in rats and 7 mg/m3 in mice as
previously
the lung
Complete necropsies were done on all animals. At necropsy, all
and tissues
were
examined
for grossly
visible
lesions,
tissues and lesions were preserved in 10% neutral-buffered
and all major
formalin, embed
ded in paraffin, sectioned, and stained with hematoxylin and eosin for micro
scopic examination.
Statistical Evaluation. The majority of neoplasms were considered to be
to the cause
of death
or not rapidly
lethal
was
36—65%
Noncarcinogenic
every 4 weeks.
incidental
studies
in subchronic
weight
studies
(7).
in the high-exposure
nickel
sulfate
33—41% more than controls; the high-exposure
lung weight in the
nickel subsulfide mice was 78—92% more than controls, and in rats,
day/night cycle was maintained. Body weight and clinical signs were recorded
Pathology.
than in the nickel sulfate
300% more; in the nickel oxide studies the high-exposure lung weight
@5
Nickel
organs
was greater
mice was 30—37%more than control lung weight, and in the rats,
Rats
Compound
a Threshold
studies.
correlated with a more severe inflammatory response after exposures
to nickel subsulfide and nickel oxide. Nickel sulfate was more acutely
Nickel oxide (76.6% nickel)
@
in these
The increase in lung weights of animals in the nickel subsulfide and
Mice
Compound
Nickel
@
.
used
and were evaluated
by
more
than
controls,
and
in rats,
86—94%
more.
Effects
A spectrum of exposure-related nonneoplastic respiratory tract lesions
seen after exposure to each of the nickels included focal alveolar/bron
chiolar hyperplasia,
inflammation,
and/or fibrosis of the lung and lymph
oid hyperplasia of the lung-associated lymph nodes. Atrophy of the
olfactory epithelium was also seen after exposure to nickel sulfate hexa
hydrate. Pigment (thought to represent nickel deposition) was also ob
served in the lung of animals exposed to nickel oxide. Qualitatively, the
inflammatory responses of interstitial fibrosis and intraalveolar macro
phage accumulation in the lung were similar in the three nickel com
logistic regression analysis (13, 14). Tests of significance
included pairwise
pounds
comparisons
a test
toxic lesions were considered to be more severe after exposure to nickel
oxide and nickel subsullide. Mice were more resistant to development of
focal hyperplastic and fibrotic lung lesions than were rats.
of each
exposure-related
exposed
group
with
controls
and
for overall
trends. Organ and body weight data were analyzed using
parametric multiple comparison procedures (15, 16), and lung burden data
were analyzed using nonparametric multiple comparison methods (17, 18).
The reported values were considered significant at the P < 0.05 level.
studied.
Carcinogenic
However,
at the exposure
concentrations
used, these
Effects
RESULTS
Nickel Oxide Studies. There was an increase in the incidence of
A/B
adenomas/carcinomas combined (A/B neoplasms) in male and
Survival and Body and Lung Weights
female rats exposed to nickel oxide at concentrations of 1.2 and 2.5
Survival of rats and mice exposed to nickel sulfate, nickel subsul
mg/m3 (Table 4). A slight increase in A/B adenomas occurred in
fide, and nickel oxide were in general similar to those of controls.
female mice exposed to 2.5 mg/m3. An increase in A/B adenomas/
Final mean body weights in both rats and mice were similar or 5—10% carcinomas combined occurred in female mice exposed to 1.2 mg/m3
lower than controls (Tables 2 and 3). Lung weights in exposed
(Table 5).
animals were greater than controls, and this was considered to be
The carcinogenic response in the lung of male and female rats
related to inflammatory lung reactions that occurred in response to exposed to nickel oxide was related to exposure because (a) the
these nickel exposures. The lung weights in the nickel oxide- and
incidence of A/B neoplasms was increased in both mid- and high
Table 2 Survival, body weight,and lung weigh: in
ratsExposure
nickel)00.1250.25
subsulfide (73.5%nickel)Nickel
(22.3% nickel)Nickel
0.151.000.621.22.5Male
(mg/m3)Nickelsulfatehexahydrate
oxide(78.6%
030
rats
Survival
Final mean body wei@ht―
Absolute lung weight
7-Month interim evaluation
99
1.67
15-Month interim evaluation16/54 2.1216/55
Female rats
Survival
101
21/55
98
1.62
1.65
1.89
2.4818/55
2.50
3.Otf13/53
21/53
98
1.87
2.27
2.38'
3.31@18/53
100
85
345C
6.84'14/54
1.72
2.2015/53
95
2.59c
1.85
2.46―
2.1515/53 3.30'12152 4.09'
22/5217/5328/5329/5426/5325/5328/5321/5326/5320/5326/5497979496789692901.251.221.221.45―[email protected]―1.65'1.78'@1.371.571.49i.82c1.522.52―4.14
Final mean body wei@ht―
Absolute lung weight
7-Month interim evaluation
15-Month interim evaluation
a Percent
b Organ
@
Cp
@
dp
relative
weight
93
to controls.
in grams.
o.os.
5252
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CARCINOGENIC EFFECTS OF NICKEL EXPOSURE IN THE LUNG
miceExposure
Table 3 Survival, body weight.and
nickel)00.250.5
oxide(78.6%
subsulfide (73.3%nickel)Nickel
(22.3% nickel)Nickel
0.61.201.252.55Male
(mg/m3)Nickelsulfatehexahydrate
mice
Survival
Final mean body wei@ht―
Absolute lung weight
7-Month interim evaluation
15-Month interim evaluation26/61
lung weight in
10
94
0.21
0.2423/61
97
0.20
0.2524/62
25/61
25/59
91
92
0.22
0.26
0.23
O.31@26/61
0.24
0.23
92
0.27
0.40'26/58
0.34c
0.41'19/57
93
0.19
0.21
93
93
0.24c
0.24'
0.2323/67 0.2529/66 0.31'23/69 0.38'
Female mice
34/6139/6045/6037/6038/5834/5938/6041/6440/6642/6338/6491948890869694900.220.210.220.250.19026d0.29c0.180.210.230.230.240.240.280.33'0.260.3
Survival
Final mean body wci@ht―
Absolute lung weight
7-Month interim evaluation
15-Month interim evaluation
a Percent
I, Organ
C p
relative
weight
to controls.
in grams.
o.oi.
dp < o.os.
exposure groups relative to concurrent and historical control rates, and
(b) the effects were observed in both male and female rats. A marginal
increase in A/B neoplasms was seen at the low and mid exposure
levels in female mice.
Nickel Subsulfide Studies. There was an increase in the incidence
of A/B adenomas, A/B carcinomas, and A/B adenoma/carcinomas
combined in male rats exposed to 1 mg/m3. The incidences of A/B
adenomas/carcinomas combined in male rats exposed to 0.15 mg/m3
and in female rats exposed to 0.15 and 1 mg/m3 (Table 3) were also
increased. No exposure-related neoplasms were observed in mice
exposed to nickel subsulfide (Table 5).
The carcinogenic response in the lung of male and female rats
exposed to nickel subsulfide was clear evidence for a carcinogenic
effect because neoplastic lung lesions were observed at both exposure
levels, the effect was observed in males and females, and the mci
dence for these neoplasms was increased relative to concurrent and
historical control rates.
Nickel Sulfate Studies. There were no increases in lung neoplasms
in rats or mice exposed to nickel sulfate (Tables 4 and 5). The A/B
neoplasms that were observed in the exposed groups were similar in
incidence and morphology to those observed in controls.
Description
@
of Lung Neoplasms
The A/B neoplasms in mice and in some rats in the nickel subsul
fide and nickel oxide studies had morphology consistent with spon
taneously occurring lung neoplasms in rodents. Typically, most A/B
carcinomas had cuboidal or low columnar epithelium in mixtures of
tubular, papillary, and alveolar growth patterns. Neoplastic cells in
carcinomas were pleomorphic and often stained deeply basophilic.
Focal alveolar epithelial hyperplasia was part of the morphological
continuum toward neoplasia and consisted of discrete areas where
alveoli were lined by cuboidal cells that occasionally formed small
projections within alveolar lumens.
Some of the A/B neoplasms in rats exposed to nickel subsulfide or
nickel oxide had morphological features that differed from the typical
papillary or solid neoplastic proliferations of A/B epithelium typically
found in control rats. Different morphological features included a
prominent fibrous tissue component (Fig. 1) and/or areas of differen
tiation to stratified squamous epithelium in A/B carcinomas (Fig. 2).
In addition, inflammatory cells, cellular debris, and areas of squamous
differentiation or a prominent dense fibrous tissue component oc
curred in some A/B adenomas.
Other Carcinogenic Effects
A carcinogenic response was also seen in the adrenal medulla of
nickel subsulfide and nickel oxide rats (Table 6). There were no other
sites for exposure-related increases in neoplasms in rats or in mice
after exposure to nickel sulfate, nickel oxide, or nickel subsulfide.
Lung Burden Data
Analysis of the nickel lung burden data showed accumulation of
nickel in the lungs of rats and mice after exposure to nickel oxide,
whereas with nickel subsulfide and nickel sulfate, nickel was cleared
from the lungs. The lung burden at 7 or 15 months in rats and mice
was 1—2 Ni/g lung for nickel sulfate, 3—26p.g Ni/g lung for nickel
subsulfide, and 175—2,258p@gNi/g lung for nickel oxide (Table 7).
The lungs were enlarged particularly in the exposed groups of rats in
Table 4Alveolar/bronchiolarneoplasms
ratsNickel
sulfate hexahydrate(22.3% nickel)Nickel
nickel)00.1250.250.50
Exposure (mg/m3)
0
2'
2―53
4e52―
Female rats
Adenoma
Carcinoma
0
0
053
Adenoma/carcinoma
a Number of animals
bp
0.05.
( includes
data
for
oxide(78.6%
0.151.000.621.252.554―
Male rats
Adenoma
Carcinoma
Adenoma/carcinoma
@
in
subsulfide (73.5%nickel)Nickel
0
0
053
0
1
153
2
1
353
0
0
0
53
3
3
6b53
0
0
053
0
0
054
1
0
153
2
0
2
53
5
ice
6@e53
6b
7b
o53
11d54
5
4
9b53
1
053
I
3
2
2
i53
3
oe52
0
053
1
4
5b
6e54
examined.
one
squamous
cell
carcinoma.
dp < o.oi.
e p
<
o.os
vs.
historical
data
[1.4%,
3/210
(males);
1.4%,
4/208
(females)].
5253
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@e
@
.
CARCINOGENIC EFFECTS OF NICKEL EXPOSURE IN ThE LUNG
@
p
@
,‘-‘-)
@
p ‘@
‘,
“@I―@@
1@
@
..‘@;,-,
_%
,-
@‘
—
.
.;@v
@ri
_@
?
.
v4@;@@ e@ a,@
,@
@
‘;@@
.
.-*,i@
@
r
@
.
@
-
-@ “i.,-@': .,;@cw@?-@@@t,z:@4
@,.
. A'
4
1
@4@/
,p@
@‘
;?*7
@
@
‘
‘. ç
-@
@54@
@)@4@.'p%
Fig. 1. Alveolar/bronchiolar
•
.
“I
,,@
•@
$@)i
(@
‘
,
:@.4
carcinoma from a male rat exposed to 0. 15 mg/m3 nickel
subsulfide for 2 years. Note the extensive connective tissue between the neoplastic
epithelial cells. X240.
the nickel oxide and nickel subsulfide studies. Therefore, when the rat
lung burden data at 7 or 15 months are expressed as amount of nickel per
total lung, the nickel accumulation after nickel oxide exposures is em
phasized: 1—2 @g
Ni/lung for nickel sulfate; 9—29 @g
Ni/lung for nickel
subsufide; and 226—4573 @gNi/lung for nickel oxide.
DISCUSSION
@
@
@
@
The most significant findings from these studies were that nickel
subsulfide and nickel oxide caused lung neoplasms in rats, and nickel
oxide caused a marginal increase in lung neoplasms in mice (Table 8).
There was also inflammation, hyperplasia, and fibrosis in the lungs of
rats, and to a lesser extent in mice, exposed to all three nickel
compounds. No exposure-related lung neoplasms occurred in rats or
mice in the nickel sulfate studies.
In the nickel subsulfide rats, there were increases in lung neoplasms
at 0.15 and 1.0 mg/rn3 (0.1 1 and 0.73 mg Ni/m3) and in the nickel
oxide rats at 1.25 and 2.5 mg/m3 (1.0 and 2.0 mg Ni/m3) after nickel
exposures of more than 1 year. As a point of reference, the threshold
limit value for insoluble nickel compounds is 1 mg Ni/rn3, although
most work situations would involve lower nickel exposures (19).
The type of nickel compound is important in the eventual carcino
genic response. Under the conditions of these studies, the nickel
compound that was more rapidly cleared from the lungs (nickel
subsulfide) gave a stronger carcinogenic response than the nickel
compound retained in the lungs (nickel oxide). Thus, the amount of
nickel in the lung (which represents the difference between the
amount of nickel deposited in the lung and the amount removed by the
clearance mechanisms) does not predict the severity of the lung tumor
response. In these studies, nickel sulfate and nickel subsuffide were
cleared from the lung, whereas nickel oxide accumulated. This agrees
with previous studies, which showed that the half-life of nickel sulfate
in the rat lung is 1—3days (20), that of nickel subsuffide, 5 days, and
that of nickel oxide, approximately 120 days (21).
In humans, it has also been shown that the amount of nickel
retained in the lung may not predict the carcinogenic response after
nickel exposure. In lung tissue specimens from 39 workers in the
nickel industry (22), the average nickel concentration for workers in
roasting and smelting operations was 330 ±380 p.g nickel/g dry lung
weight; for workers in electrolysis departments, 34 ±48
@@g;
and for
unexposed people, 0.76 ±0.39
(dry lung represents approxi
mately 20% “wet―
lung weight, the lung weight used in our studies in
rodents). Workers who were diagnosed with lung cancer (14 cases)
had the same lung nickel burdens at autopsy as did nickel workers (25
cases) who died of other causes. This study also found that lung
cancer occurred in workers from the electrolysis department (8 of 24),
as well as those from the roasting and smelting operations (6 of 15),
although those from the electrolysis department had lower lung nickel
burdens. Thus, both our studies and the studies in humans show that
a measurement of retained nickel does not necessarily predict the
extent of lung cancer after nickel exposures.
The formation of lung neoplasms in rodents after exposures to
nickel subsulfide and nickel oxide were considered to be specifically
related to the nickel exposures. Nickel subsulfide lung burdens at 15
months remained below 30 @gNi/g lung, but nickel lung burdens
increased in the nickel oxide studies to approximately 1000 @gNi/g
lung (>4000 @gNi/lung). The possible relationship between nickel
accumulation in the lung in the nickel oxide studies and the toxico
logical effects remains unclear at this time. Recent studies have shown
that repeated exposure to 0.62 and 2.5 mg NiO/m3 results in impaired
clearance of subsequent inhaled nickel oxide (23).
Rat carcinogenicity studies with other relatively nontoxic particles,
such as titanium dioxide [250 mg/m3 (24)J, talc [18 mg/m3 (25)], and
antimony trioxide [45 mg/m3 (26)], required higher aerosol concen
trations to produce a carcinogenic response than did the nickel com
pounds. For example, the carcinogenic response in the rat lung in talc
studies was seen at 18 mg/m3, and at this exposure, lung burden was
approximately 25 mg talc/g lung at 18 and 24 months. The lung tumor
response with these other substances may be due in part to accumu
lation of nontoxic particles.
Other studies have shown that nickel subsuffide is carcinogenic in the
rat after local injection (5), inhalation exposure (1 mg/m3) (11), and i.t.
administration
(27, 28), but not after i.t. administration
in hamsters
(29).
Nickel oxide has been shown to be carcinogenic after local injection in
rodents, but there have been no previous chronic inhalation studies with
this compound in rats. One long-term nickel oxide inhalation study
performed in hamsters (50 mg/m3) was negative for carcinogenic activity
(30).In contrast,nickelsulfatedoesnot producetumorsafterlocal
injection (5). Therefore, it appears that for the nickel compounds used in
these studies, the carcinogenic response after local injection predicts the
carcinogenic
response
after inhalation
exposure
in the rat.
Selection of the model system is important in assessing and pre
dicting the potential extent of environment disease. More chemical
related lung neoplasms were observed in nickel subsulfide- and nickel
oxide-exposed rats than in mice. In studies of other metals (e.g.,
.@
@@y?,@'H:.
•@M@@4g
@.
‘@
@.
\
.
‘.4.
@-:
@,
...
..
:4-
;- ‘
...
*[email protected]
...“o
@..
V-.-.
Fig. 2. Alveolar/bronchiolar carcinoma with areas of squamous differentiation
male rat exposed to 1.0 mg/m3 nickel subsulfide. X 150.
5254
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from a
CARCINOGENIC EFFECFS OF NICKEL EXPOSURE IN THE LUNG
miceNickel
nickel)Exposure
5Male
Table 5 Alveolar/bronchiolar
neoplasms in
sulfate hexahydrate (22.3% nickel)
(mg/in3)
0
69Adenoma
mice
11Carcinoma
6Adenoma/carcinoma
14Female
rats
Adenoma
3Carcinoma
2Adenoma/carcinoma
8a
Nickel subsulfide (73.3% nickel)
Nickel oxide (78.6%
0.25
0.5
1
0
6
1.2
0
1.25
2.5
61―
S
9
13
61
5
13
18
62
3
4
7
61
5
3
8
61
6
7
13
59
3
2
5
58
2
4
6
57
7
4
9
67
5
10
14
66
6
9
15
61―
3
4
7
f,4J
3
3
6
f@
2
9
10
f@f@
0
2
1
58
3
7
9
59
1
1
2
60
1
2
3
64
2
4
6
66
4
11
l5'@
63
lO@
4
12
64
examined.bp
Number of animals
<
o.os.Table
ratsNickel
nickel)Exposure
2.5Male
(mg/m3)
0
54Hyperplasia
rats
Benign pheochromocytoma
Malignant pheochromocytoma
35bFemale
Benign or malignant pheochromocytoma
54Hyperplasia
rats
@
@
6 Adrenal medulla prol(ferative lesions in
sulfate hexahydrate (22.3% nickel)
18―Malignant
Benign
pheochromocytoma
pheochromocytoma
Nickel subsulfide (73.3% nickel)
Nickel oxide (78.6%
0.125
0.25
0.5
0
0.15
1.0
0
0.62
1.2
54―
28
16
0
16
55
20
16
3
19
55
18
12
2
13
55
26
11
1
12
53
26
13
0
14
53
22
30―
2
30―
53
10
38b
10―
42―
54
25
27
0
27
53
27
24
0
24
53
26
26
1
27
52a
6
2
0
53
4
4
0
53
8
2
0
54
8
3
0
53
5
2
1
53
11
7
0
53
16b
36b
1
53
8
53
12
0
0
53
14
6
0
2
4
2
3
3
7
36b
18―a
Benign or malignant pheochromocytoma
24
32
6c
22―
0
6
examined.bp
Number of animals
o.oi.‘.
<
@
0.05.cadmium
P
nickelbeen compounds) exposure-related lung neoplasms have also
inThus,found to occur more frequently in rats than in mice (31, 32).
thesemodel
these findings suggest that the rat may be more sensitive as a
than the mouse for metal-induced toxic and carcinogenic
responses in the lung, and also a better model system for predicting
disease in humans. It should be noted that the mouse is more susceptible to the formation of other chemically-induced lung neoplasms
from epoxide and halogenated chemicals (8—10).
mice.and
Whereas the relationship of increased adrenal medullary tumors
exposure to nickel subsulfide or nickel oxide is clear, the mechanism for this increase is uncertain. It is possible that a small amount
of nickel may reach the adrenal medulla and cause a direct carcino
genic effect at that site. There is some distribution of nickel subsulfide
to extrarespiratory tissues (e.g. , kidney), but a significant increase in
nickel was not detected beyond the respiratory tissues with nickel
oxide exposures. A similar increase in adrenal tumors has also been
seen in inhalation studies with an unrelated inert particle (talc). It is
possible that an unknown secondary mechanism related to chronic
pulmonary inflammation may be related to the observed increase in
tumors in the adrenal medulla.
Nasopharyngeal carcinoma in humans has been attributed to
exposure (6). In our studies, there was no evidence of carcinogenesis
the nasal cavity in either rats or mice. The preponderance of
sinonasai neoplasms in humans have been classified as anaplastic, undif
ferentiated, or squamous cell carcinoma (33). In nickel sulfate (jre
chronice and chronic) and nickel subsulfide (prechronic) inhalation ro
dent studies (7), the olfactory epithelium, rather than the respiratory or
squamous mucosa, was the target site for chemical-related toxicity.
Nickel sulfate was not carcinogenic in the lung of rats or
However, in prechonic studies at higher exposure, this compound
resulted in mortality and necrotizing pneumonia at concentrations that
were nonlethal with exposure to nickel subsulfide and nickel oxide. It
has been found that exposure to the water-soluble nickel salts (i.e.,
nickel sulfate) may have a synergistic role with oxidic or other forms
of nickel in causing lung and nasal neoplasms in nickel refinery
workers (6). Experimental studies have shown that water-soluble
nickel salts enhance the cytotoxicity and mutagenicity of DNA
damaging agents by inhibiting DNA repair processes (34). The inhi
bition of DNA repair may be one mechanism by which the water
TableoxideNickel
7 Lung burden analyses in the studies ofnickel sulfate hexahydrate, nickel subsulfide, and nickel
sulfate hexahydrate (22.3% nickel)
Exposure (mg/m3)
0
0.12
0.25
0.5
Nickel subsulfide (73.3% nickel)
1
0
0.15
0.6
1
Nickel oxide (78.6% nickel)
1.2
0
0.62
1.25
2.5
5
7-Month interim evaluation
Male rats
1b69—175388701———1—69—173477713—112—1011—1624421,034—122—1014—169533861———1—43—3287461,116———2—47—262706949—I12—1526—3319591,7
Female rats
Male mice
Female mice
15-Month interim evaluation
Male rats
Female rats
Male mice
Female mice
a Results
were below
b Values
represent
the limit of detection.
mean
amount
of nickel
(@xg nickel/g
lung).
Lung
burden
groups
included
5—7 animals.
5255
Downloaded from cancerres.aacrjournals.org on June 16, 2017. © 1995 American Association for Cancer Research.
CARCINOGENIC EFFECrS OF NICKEL EXPOSURE IN THE LUNG
Table 8 LeveIs of carcinogenic
activityNickel
14. Dinse, G. E., and Haseman, J. K. Logistic regression analysis of incidental tumor data
from animal carcinogenicity experiments. Fundam. Appi. Toxicol., 6: 44—52,1986.
15. Dunnett, C. W. A multiple comparison procedure for comparing several treatments
with a control. J. Am. Stat. Assoc., 50: 1096—1121, 1955.
16. Williams, D. A. The comparison of several dose levels with a zero dose control.
sulfatehexahydrateNickel
subsulfideNickel
oxideMale
ratsNoClear
(lung, adrenal
(lung, adrenal
Biometrics, 28: 519—531,1971.
medulla)Some
medulla)Female
ratsNoClear
(lung, adrenal
17. Shirley, E. A non-parametric equivalent of Williams' test for contrasting increasing
dose levels of a treatment. Biometrics, 33: 386—389, 1977.
18. Dunn, 0. J. Multiple comparisons using rank sums. Technometrics, 6: 241-251, 1964.
19. American Conference of Govemmental Industrial Hygienists. Threshold limit values
for chemical substances and physical agents and biological exposure indices for
(lung, adrenal
medulla)Some
medulla)Male
miceNoNoNoFemale
miceNoNoEquivocal
(lung)
1993—1994.
Cincinnati, OH: American Conference of Governmental Industrial Hy
soluble nickel salts have a synergistic role in enhancing
carcinogenesis after exposure to other nickel compounds.
The mechanisms for how nickel compounds cause carcinogenic effects
is an area of continuing investigation. In vitro studies have shown that
water-insoluble nickel compounds are more readily phagocytized than
the water-soluble nickel compounds and, therefore, will reach the nucleus
of the cell in greater amounts than will the water-soluble nickel com
pounds (35—40).Nickel subsulfide produces a high level of oxidants in
the nuclei of cells, which could directly damage protein and DNA (41,
42). Other in vitro studies suggest that nickel may cause gene alterations
by enhanced DNA methylation and heterochromatin condensation, cans
ing inactivation of Critical tumor suppressor or senescence genes (43, 44).
Our findings of the carcinogenic response in the rat lung after
exposure to nickel subsulfide or nickel oxide agree with epidemiology
findings, which show that exposure of workers particularly to the
oxidic and sulfidic nickel compounds may lead to an increased risk of
lung cancer (6). The epidemiology studies also suggest that exposure
to soluble nickel salts enhances the risk associated with exposure to
less soluble forms of nickel.
The authors gratefully acknowledge the contributions of the technical staff
of the Inhalation Toxicology Research Institute and Des. Robert Goyer and
Ronald Herbert (National Institutes of Environmental Health Sciences) for
discussions
and review
“3Ni
in F3441Nrats after intratracheal instillation of nickel sulfate solutions. Environ.
Res., 43: 168—178,1987.
21. Benson, J. M., Barr, E. B, Bechtold, W. E., Cheng, Y. S., Dunnick, J. K., Eastin,
W. E., Hobbs, C. H., Kennedy, C. H., and Mapples, K. R. Fate of inhaled nickel oxide
and nickel subsulfide in F344/N rats. Inhal. Toxicol., 6: 167—183,1994.
22. Andersen, I., and Svenes, K. B. Determination of nickel in lung specimens of thirty-nine
autopsied nickel workers@lot. Arch. Occup. Environ. Health, 61: 289-295, 1989.
23. Benson, J. M., Chang, I., Cheng, Y. S., Hahn, F. F., Kennedy, C. H., Barr, E. B.,
Maples, K. R., and Snipes, M. B. Particle clearance and histopathology in lungs of
F344/N rats and B6C3F1 mice inhaling fickle oxide or nickel sulfate. Fundam. Appl.
Toxicol., in press, 1995.
24. Lee, K. P., Trolchimowicz, H. J., and Reinhardt, C. R. Pulmonary response of rats
exposed to titanium dioxide (Ti02) by inhalation for two years. Toxicol. Appl.
Pharmacol., 79: 179—192,1985.
25. National Toxicology Program. Toxicology and carcinogenesis studies of talc in
F344/N rats and B6C3F, mice. TR 421. NIH Publ. No. 93-3152. Research Triangle
Park, NC: NIH, 1993.
26. Groth, D. H., Stettler, L E., Burg, J. R., Busey, W. M., Grant, G. C., and Wong, L
Carcinogenicity effects of antimony trioxide and antimony ore concentrate in rats. J.
Toxicol. Environ. Health, 18: 607—626, 1986.
27. PoU, F., Ziem, U., Reiffer, F. J., Huth, F., Ernst, H., and Mohr, U. Carcinogenicity
studies on fibres, metal compounds, and some other dusts in rats. Exp. Pathol., 32:
129—152,1987.
28. Yarita, T., and Nettesheim, P. Carcinogenicity of nickel subsulfide for respiratory
tract mucosa. Cancer Rca., 38: 3140—3145.
29. Muhle, H., Belimann, B., Takenaka, S., Fuhst, R., Mohr, U., and Pott, F. Chronic
effects of intratracheally instilled nickel-containing particles in hamsters. In: E.
Nieboer and J. 0. Nriagu (eds.), Nickel and Human Health: Current Perspectives,
ACKNOWLEDGMENTS
their helpful
gienists, 1993.
20. Medinsky, M. A., Benson, J. M., and Hobbs, C. H. Lung clearance and disposition of
four cadmiumcompoundsinhaledby rats ToxicoLEnviron.Chem., 27: 153-162, 1990.
32. Heinrich, U., Peters, L, Ernst, H., Rigginghausen, S., Dasenbrock, C., and Konig, H.
Investigation on the carcinogenic effects of various cadmium compounds after inha
lation exposure in hamsters and mice. Exp. Pathol., 37: 253—258,1989.
33. Sunderman, F. W., Morgan, L. G., Andersen, A, Ashely, D., and Forouhar, F.
Histopathology of sinonasal and lung cancers in nickel refinery workers. Ann. Clin.
of the manuscript.
REFERENCES
1. Bridge, J. D. Annual Report of the Chieflnspector
pp. 467—479.New York: John Wiley and Sons, Inc., 1992.
30. Wehner, A. P., Busch, R. H., Olson, R. J., and Craig, D. K. Chronic inhalation of nickel
oxide and cigarette smoke by hamsters. Am. Ind. Hyg. Assoc. J., 36: 801—810,1975.
31. Glaser, U., Hochrainer, D., Otto, F. J., and Oldiges, H. Carcinogenicity and toxicity of
of Factories and Workshops for the
Year 1932, pp. 103—104.
London, UK: His Majesty's Stationery Office, 1933.
2. Doll, R. Cancer of the lung and nose in nickel workers. Br. J. md. Med., 15: 217—223,
1958.
3. Morgan, J. 0. Some observations on the incidence of respiratory cancer in nickel
workers. Br. J. md. Med., 15: 224—234, 1958.
4. United States Bureau of Mines. Nickel. In: Mineral Commodity Summaries 1991, pp.
110—1
1 1. Washington, DC: United States Department of the Interior, Bureau of
Mines, 1991.
5. LARC. IARC Monographs on the Evaluation of Carcinogenic Risk to Humans.
Chromium, Nickel and welding, Vol 49. Lyon, France: IARC, 1990.
6. Doll, R., Andersen, A., Cooper, W. C., Cosmatos, I., Cragle, D. L, Easton, D.,
Enterline, P., Goldberg, M., Metcalfe, L., Norseth, T., Peto, J., Rigaut, J., Roberts, R.,
Seilkop, S. K., Shannon, H., Speizer, F., Sunderman, F. W., Jr., Thornhill, P., Warner,
J. S., Weglo, J., and Wright, M. Report of the international committee on nickel
carcinogenesis in man. Scand. J. Work Environ. & Health, 16: 1—82,1990.
7. Dunnick, J. K., Elwell, M. R., Benson, J. M., Hobbs, C. H., Hahn, F. F., Haley, P. J.,
Cheng, Y. S., and Eidson, A. F. Lung toxicity after 13-week inhalation exposure to
nickel oxide, nickel subsulfide, or nickel sulfate hexahydrate in F344/N rats and
B6C3F, mice. Fundam. AppI. Toxicol., 12: 584—594, 1989.
8. National Toxicology Program. Toxicology and Carcinogenesis Studies of Nickel
Subsulfide. NIH PubI. No. 94-3369. Research Triangle Park, NC: NIH, 1994.
9. National Toxicology Program. Toxicology and Carcinogenesis Studies of Nickel
Oxide. NIH PubI. No. 94-3363. Research Triangle Park, NC: NIH, 1994.
10. National Toxicology Program. Toxicology and Carcinogenesis Studies of Nickel Sulfate
Hexahydrate. NIH PubI. No. 94-3370. Research Triangle Park, NC: NIH, 1994.
11. Ottolenghi, A. D., Haseman, J. K., Payne, W. W., Falk, H. L., and MacFarland, H. N.
Inhalation studies of nickel sulfide in pulmonary carcinogenesis of rats. J. Natl.
Cancer Inst., 54: 1165—1170,1975.
12. Benson, J. M., Eidson, A. F., Hanson, R. L, Henderson, R. F., and Hobbs, C. H. A
rapid digestion method for analysis of nickel compounds in tissue by electrothermal
atomic absorption spectrometry. J. Appl. Toxicol., 9: 219—222, 1989.
13. Dinse, 0. E., and Lagakos, S. W. Regression analysis of tumour prevalence data.
Appl. Statist., 32: 236—248,1983.
Lab. Sci., 19: 44—50,1989.
34. Hartwig, A., Mullenders, L. H. R., Schepegrell, R., Kasten, U., and Beyersmann, D.
Nickel(ll) interferes with the incision step in nucleotide excision repair in mammalian
cells. Cancer Rca., 54: 4045-4051, 1994.
35. Costa, M., Zhuang, Z., Huang, S., Cosentino, S., Klein, C. B., and Salnikow, K.
Molecular mechanisms of nickel carcinogenesis. Sci. Total Environ., 148: 194—199,
1994.
36. Costa, M., and Molienhauer, H. H. Carcinogenic activity of particulate metal corn
pounds is proportional to their cellular uptake. Science (Washington DC), 209:
515—517,1980.
37. Abbracchio, M. P., Heck, J. D., and Costa, M. The phagocytosis and transforming
activity of crystalline metal sulfide particles are related to their negative surface
charge. Carcinogenesis (Land.), 3: 175—180,1982.
38. Abbracchio, M. P., Simmons-Hansen, J. S., and Costa, M. Cytoplasmic dissolution of
phagocytized crystalline metal sulfide particles: a prerequisite for nuclear uptake of
nickel. J. Toxicol. Environ. Health, 9: 663—676, 1982.
39. Evans, R. M., Davies, P. J. A., and Costa, M. Video time-lapse microscopy study of
phagocytosis and intracellular fate of crystalline nickel sulfide particles in cultured
mammalian cells. Cancer Res., 42: 2729—2735,1982.
40. Costa, M. Molecular mechanisms of nickel carcinogenesis. Annu. Rev. Pharmacol.
Toxicol., 31: 321—337,1991.
41. Huang, X., Klein, C. B., and Costa, M. Crystalline Ni3S2 specifically enhances the
formation of oxidants in the nuclei of CHO cells as detected by dichlorofluorescein.
Carcinogenesis (Land.), 15: 545—548,1994.
42. Lee, Y. W., Pons, C., Tummolo, D. M., Klein, C. R., Rossman, T. G., and Christie,
N. T. Mutagenicity of soluble and insoluble nickel compounds at the gpt locus in G12
Chinese hamster cells. Environ. Moi. Mutagen., 21: 365—371,1993.
43. Klein, C. B., Conway, K, Wang, X. W., Bhamra, R., Un, X., Cohen, M. D., Annab, L,
Barrett@J. C., and Costa, M. Senescence of nickel-transformed cells by an X chromosome:
possible epigeneticcontrol. Science (WashingtonDC), 251: 796—799,
1991.
44. Lee, Y. W., Klein, C. B., Kargacin, B., Sainikow, K., Kitahara, J., Dowjat, K.,
Zhitkovich, A., Christie, N. T., and Costa, M. Carcinogenic nickel silences gene
expression by chrornatin condensation and DNA methylation: a new model for
epigenetic carcinogens. MoI. Cell. Biol., 15: 2547—2557, 1995.
5256
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Comparative Carcinogenic Effects of Nickel Subsulfide, Nickel
Oxide, or Nickel Sulfate Hexahydrate Chronic Exposures in the
Lung
June K. Dunnick, Michael R. Elwell, Ann E. Radovsky, et al.
Cancer Res 1995;55:5251-5256.
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