NTP Study Reports
Abstract for TR-453 - Nickel Subsulfide
TR-453
Toxicology and Carcinogenesis Studies of
Nickel Subsulfide (CAS No. 12035-72-2) in F344 Rats and
B6C3F1 Mice (Inhalation Studies)
Chemical Formula: Ni3S2
Nickel subsulfide is used in the
manufacture of lithium batteries and is a major component in the
refining of certain nickel ores. Nickel subsulfide was nominated
as part of a class study of nickel compounds, for which there
was little information on the toxic and carcinogenic effects of
inhalation exposure. Male and female F334/N rats and B6C3F1 mice
were exposed to nickel subsulfide (at least 97% pure; the mean
value for the mass median aerodynamic diameter at each exposure
concentration ranged from 2.0 to 2.2 mm by inhalation 6 hours
per day, 5 days per week, for 16 days, 13 weeks, or 2 years. Genetic
toxicology studies were conducted in Salmonella typhimurium,
and mouse peripheral blood samples were analyzed for frequency
of micronucleated normochromatic erythrocytes.
16-DAY STUDY IN RATS
Groups of five male and five female
F344/N rats were exposed to atmospheres containing 0, 0.6, 1.2,
2.5, 5, or 10 mg nickel subsulfide/m3 (equivalent to
0, 0.44, 0.88, 1.83, 3.65, and 7.33 mg nickel/m3) 6
hours per day, 5 days per week for a total of 12 exposure days
during a 16-day period. Additionalmgroups of three male and
three female rats were exposed to 0, 0.6, 2.5, or 10 mg/m3
for tissue burden studies. One male exposed to 10 mg nickel subsulfide/m3
in the core study died on day 14; all other rats survived until
the end of the study. Final mean body weights and mean body weight
gains of males exposed to 5 or 10 mg nickel subsulfide/m3
and females exposed to 2.5, 5, or 10 mg/m3 were significantly
lower than those of the controls. Clinical findings of toxicity
on day 5 of the study included labored respiration in 10 mg/m3
males and 5 and 10 mg/m3 females and dehydration in
5 and 10 mg/m3 females. Absolute and relative lung
weights of 2.5, 5, and 10 mg/m3 males and all exposed
groups of females were significantlymgreater than those of the
controls, as was the absolute lung weight of 1.2 mg/m3
males. Inflammation of the lung and atrophy of the nasal olfactory
epithelium occurred in all exposed mgroups. The concentrations
of nickel in the lungs of exposedmgroups of rats increased with
exposure concentration (males, 7 to 67 mg nickel/g lung; females,
9 to 77 mg/g lung).
16-DAY STUDY IN MICE
Groups of five male and five female
B6C3F1 mice were exposed to atmospheres containing 0, 0.6, 1.2,
2.5, 5, or 10 mg nickel subsulfide/m3 for 6 hours per
day, 5 days per week for a total of 12 exposure days during a
16-day period. Additional groups of three male and three
female mice were exposed to 0, 0.6, 2.5, or 10 mg/m3
for tissue burden studies. All male and female mice exposed to
10 mg nickel subsulfide/m3 in the core study died before
the end of the study; the death of one female was accidental.
One control male, one control female, and one 1.2 mg/m3
male also died before the end of the study. Final mean body weights
and mean body weight gains of 5 mg/m3 males were significantly
lower than those of the controls. Clinical findings at day 5 included
labored respiration in 10 mg/m3 males and females.
The absolute lung weight of 5 mg/m3 males, the absolute
and relative lung weights of 10 mg/m3 males and 5 mg/m3
females, and the relative lung weight of 10 mg/m3 females
were significantly greater than those of the controls. Inflammation
of the lung occurred
in 2.5, 5, and 10 mg/m3 male and female mice, fibrosis
of the lung occurred in 5 mg/m3 males and females,
and lymphoid hyperplasia of the bronchial lymph nodes and atrophy
of the nasal olfactory epithelium occurred in 1.2, 2.5, 5, and
10 mg/m3 males and females. Nickel concentrations in
the lung of exposed male and female mice were greater than those
of the controls (males, 10 to 20 mg nickel/g lung; females, 8 to
20 mg/g lung)
13-WEEK STUDY IN RATS
Groups of 10 male and 10 female
F344/N rats were exposed to atmospheres containing 0, 0.15, 0.3,
0.6, 1.2, or 2.5 mg nickel subsulfide/m3 (equivalent
to 0, 0.11, 0.22, 0.44, 0.88, and 1.83 mg nickel/m3)
6 hours per day, 5 days per week for 13 weeks. Additional groups
of 18 male and 18 female rats were exposed to 0, 0.15, 0.6, or
2.5 mg/m3 for tissue burden studies. All core study
rats survived until the end of the study. Final mean body weights
and mean body weight gains of 2.5 mg/m3 males were
significantly lower than those of the controls; final mean body
weights of all other exposure groups were similar to those of
the controls. Chemical-related clinical findings included
labored respiration in 2.5 mg/m3 males and females
during weeks 2 through 7. In general, neutrophil and erythrocyte
counts, hematocrit values, and hemoglobin concentrations were
minimally increased in exposed rats. Absolute and relative lung
weights of all exposed groups were significantly greater than
those of the controls.
Increases in the number of alveolar
macrophages, interstitial infiltrates, or incidences of chronic
inflammation of the lung occurred in all groups exposed to nickel
subsulfide concentrations of 0.3 mg/m3 or greater;
the severity of these lesions generally increased with increasing
exposure concentration. Increases in the number of alveolar macrophages
were observed in 0.15 mg/m3 males and females. Lymphoid
hyperplasia of the bronchial and mediastinal lymph nodes was observed
in rats exposed to 0.3 mg/m3 or greater. Most 0.6,
1.2, and 2.5 mg/m3 males and females had atrophy of
the nasal olfactory epithelium, and the severity generally increased
with increasing exposure concentration.
Nickel concentrations in the lung
increased with exposure concentration and were greater than those
in the controls in rats exposed for 13 weeks (males, 5 to 18 mg
nickel/g lung; females, 5 to 17 mg/g lung).
13-WEEK STUDY IN MICE
Groups of 10 male and 10 female
B6C3F1 mice were exposed to atmospheres containing 0, 0.15, 0.3,
0.6, 1.2, or 2.5 mg nickel subsulfide/m3 for 6 hours
per day, 5 days per week for 13 weeks. Additional groups of six
male and six female mice were exposed to 0, 0.15, 0.6, or 2.5
mg/m3 for tissue burden studies. Final mean body weights
of all exposure groups were similar to those of the controls.
No chemical-related clinical findings were observed. Lymphocyte
counts in 1.2 and 2.5 mg/m3 males were minimally greater
than that of the controls. Hemoglobin concentrations and erythrocyte
counts in 0.3, 0.6, 1.2, and 2.5 mg/m3 females were
minimally greater than those of the controls. Absolute and relative
lung weights of 1.2 and 2.5 mg/m3 males and females
were significantly greater than those of the controls. An increase
in alveolar macrophages was present in mice from the 0.3 mg/m3
and higher exposure groups. Chronic inflammation and fibrosis
were observed in the lung of 1.2 and 2.5 mg/m3 males
and females. Interstitial infiltrates of lymphocytes were observed
in mice exposed to 0.6, 1.2, or 2.5 mg/m3. Lymphoid
hyperplasia of the bronchial lymph nodes was observed in groups
exposed to 1.2 or 2.5 mg/m3.
Atrophy of the nasal olfactory
epithelium occurred in 0.6, 1.2, and 2.5 mg/m3 males
and females, and incidences and severity generally increased with
increasing exposure concentration.
At 13 weeks, nickel concentrations
in the lungs of exposed mice were greater than those of the controls
(males, 3 to 17 g nickel/g lung; females, 6 to 23 mg/g lung), and
these concentrations increased with increasing exposure concentration.
2-YEAR STUDY IN RATS
Survival, Body Weights,
Clinical Findings, and Hematology
Groups of 63 male and 63 female
F344/N rats were exposed to 0, 0.15, or 1 mg nickel subsulfide/m3
(equivalent to 0, 0.11, or 0.73 mg nickel/m3) by inhalation
for 6 hours per day, 5 days per week for 104 weeks. Survival of
exposed males and female rats was similar to that of the controls.
Mean body weights of males and females exposed to 0.15 mg/m3
were similar to those of the controls. Mean body weights of rats
exposed to 1 mg/m3 were lower than those of the controls
throughout the second year of the study. Chemical-related
clinical findings included rapid and shallow breathing following
exposure periods. Hematocrit values and hemoglobin concentrations
in 1 mg/m3 males and females and the erythrocyte count
in 1 mg/m3 males were mildly greater than those in
the controls.
Pathology Findings
In general, the
absolute and relative lung weights of exposed males and females
were significantly greater than those of the controls at 7 and
15 months. There were exposure-related
increases in the incidences of alveolar/bronchiolar adenoma in
males, alveolar/bronchiolar carcinoma in males and females, and
alveolar/bronchiolar adenoma or carcinoma (combined) in males
and females at 2 years. Nonneoplastic lung lesions generally observed
in exposed males and females included fibrosis; chronic active
inflammation; focal alveolar epithelial hyperplasia, macrophage
hyperplasia, and proteinosis; bronchial lymphoid hyperplasia;
and interstitial inflammation.
At 2 years, there were significant
exposure-related increases in the incidences of benign pheochromocytoma,
malignant pheochromocytoma, and benign or malignant pheochromocytoma
(combined) in males and of benign pheochromocytoma in females.
The incidence of adrenal medulla hyperplasia in 1 mg/m3
females was significantly greater than that of the controls
At 2 years, the incidences of
chronic active inflammation of the nose in 1 mg/m3
females and of olfactory epithelial atrophy in 1 mg/m3 males
and females were significantly greater than those of the controls.
The incidences of lymphoid hyperplasia
of the bronchial lymph node in exposed males at 7 and 15 months
and in exposed males and females at 2 years were significantly
greater than those of the controls. Incidences of macrophage hyperplasia
in the bronchial lymph node of exposed males at 15 months and
exposed males and females at 2 years were greater than those of
the controls.
Tissue Burden Analyses
Nickel concentrations in the lungs
of exposed rats were greater than those of the controls at 7 months
(males, 6 to 9 mg nickel/g lung; females, 6 to 9 mg/g lung) and
15 months (males, 4 to 3 mg nickel/g lung; females, 4 to 7 mg/g
lung).
2-YEAR STUDY IN MICE
Survival, Body Weights, Clinical Findings, and Hematology
Groups of 80 male and 80 female
B6C3F1 mice were exposed to 0, 0.6, or 1.2 mg nickel subsulfide/m3
(equivalent to 0, 0.44, or 0.88 mg nickel/m3) by inhalation
for 6 hours per day, 5 days per week for 105 weeks. Survival of
exposed male and female mice was similar to that of the controls.
Mean body weights of 0.6 and 1.2 mg/m3 males and females
were less than those of the controls throughout the second year
of the study. Chemical-related clinical findings in male
and female mice included labored respiration following exposure
periods. The hematocrit value and the segmented neutrophil, monocyte,
lymphocyte, and total leukocyte counts in 1.2 mg/m3
females were greater than those in the controls.
Pathology Findings
Absolute and relative lung weights
of exposed males and females were generally significantly greater
than those of the controls at 7 and 15 months. The incidence of
alveolar/bronchiolar carcinoma in 0.6 mg/m3 females
and the incidences of alveolar/bronchiolar adenoma or carcinoma
(combined) in 0.6 mg/m3 males and 0.6 and 1.2 mg/m3
females were significantly less than those of the controls. In
general, the incidences of chronic active inflammation; bronchialization
(alveolar epithelial hyperplasia), macrophage hyperplasia and
proteinosis; interstitial infiltration; and fibrosis in exposed
groups of males and females were greater than those of the controls
at 7 and 15 months and at 2 years.
The incidences of atrophy of the
nasal olfactory epithelium and inflammation of the nose in exposed
mice were also generally greater than those of the controls. At
2 years, the incidences of degeneration of olfactory epithelium
in exposed females were significantly less than that of the controls.
The incidences of lymphoid hyperplasia
of the bronchial lymph node in 1.2 mg/m3 males at 15
months, in 0.6 and 1.2 mg/m3 females at 15 months,
and in 0.6 and 1.2 mg/m3 males and females at 2 years
were significantly greater than those of the controls. The incidences
of macrophage hyperplasia in 1.2 mg/m3 males at 7 and
15 months, in 0.6 and 1.2 mg/m3 females at 15 months,
and in 0.6 and 1.2 mg/m3 males and females at 2 years
were significantly greater than those of the controls.
Tissue Burden Analyses
Nickel concentrations in the lungs
of exposed mice were greater than those of the controls at 7 months
(males, 10 to 11 mg nickel/g lung; females, 10 to 14 mg/g lung)
and 15 months (males, 12 to 20 mg nickel/g lung; females, 15 to
26 mg/g lung).
GENETIC TOXICOLOGY
Nickel subsulfide was considered
to be equivocal in the Salmonella gene mutation assay overall.
Sporadic weakly positive and equivocal responses were obtained
in strain TA100 with and without S9 metabolic activation enzymes;
all other strain/activation combinations gave negative results.
No increase in the frequency of micronucleated erythrocytes was
observed in peripheral blood samples from male or female mice
exposed to nickel subsulfide by inhalation for 13 weeks.
CONCLUSIONS
Under the conditions of these
2-year inhalation studies, there was clear evidence of
carcinogenic activity of nickel subsulfide in male F344/N
rats based on increased incidences of alveolar/bronchiolar adenoma,
carcinoma, and adenoma or carcinoma (combined) and on increased
incidences of benign, malignant, and benign or malignant (combined)
pheochromocytoma of the adrenal medulla. There was clear evidence
of carcinogenic activity of nickel subsulfide in female F344/N
rats based on increased incidences of alveolar/bronchiolar carcinoma
and alveolar/bronchiolar adenoma or carcinoma (combined) and an
increased incidence of benign pheochromocytoma of the adrenal
medulla. There was no evidence of carcinogenic activity of
nickel subsulfide in male or female B6C3F1 mice exposed to 0.6
or 1.2 mg/m3.
Exposure of male and female rats
to nickel subsulfide by inhalation for 2 years resulted in inflammation,
hyperplasia, and fibrosis in the lung; inflammation and atrophy
of the olfactory epithelium in the nose; and hyperplasia in the
adrenal medulla (females). Exposure of male and female mice to
nickel subsulfide by inhalation for 2 years resulted in inflammation,
bronchialization, hyperplasia, and fibrosis in the lung and inflammation
and atrophy of the olfactory epithelium in the nose.
Synonyms: Heazlewoodite, nickel
subsulphide, nickel sulfide (3:2),
a-nickel sulfide (3:2) crystalline,
nickel sulphide, nickel tritadisulphide, trinickel disulfide
Report Date: July 1996
Pathology Tables, Survival and Growth Curves from NTP 2-year Studies
Target Organs & Incidences from 2-year Studies
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