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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
chronic toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP guideline study without detailed documentation.
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Unnamed
Year:
2007
Reference Type:
secondary source
Title:
Nickel Sulphate, CAS-No.: 7786-81-4, EINECS-No.: 232-104-9, RISK ASSESSMENT Final version March 2008, Chapters 0, 1, 2, 4, 5, 6 & 7 – human health only
Author:
Danish Environmental Protection Agency
Year:
2008
Bibliographic source:
European Union Risk Assessment Report

Materials and methods

Test guidelineopen allclose all
Qualifier:
equivalent or similar to guideline
Guideline:
other: OECD 451 Carcinogenicity studies
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
other: EPA OPPTS 870.4200
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Reference substance name:
10101-97-0
EC Number:
600-152-3
Cas Number:
10101-97-0
IUPAC Name:
10101-97-0
Constituent 2
Reference substance name:
Nickel sulphate
EC Number:
232-104-9
EC Name:
Nickel sulphate
Cas Number:
7786-81-4
IUPAC Name:
nickel(2+) sulfate
Constituent 3
Reference substance name:
nickel(II) sulfate hexahydrate
IUPAC Name:
nickel(II) sulfate hexahydrate
Details on test material:
- Name of test material (as cited in study report): Nickel sulfate hexahydrate
- Molecular formula (if other than submission substance): NiSO4*6H2O
- Molecular weight (if other than submission substance): 262.85
- Analytical purity: 99.99 %
- Purity test date: prior to test, week 51 and following study completion
- Stability under test conditions: yes
- Other: Source: Sigma Aldrich, USA

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, North Carolina
- Age at study initiation: approx. 6 weeks
- Weight at study initiation: males 118 - 147 g; females 93 - 112 g
- Fasting period before study: no data
- Housing: individually in stainless steel cages, rotated in a regular fashion
- Diet (e.g. ad libitum): purified municipal water ad libitum
- Water (e.g. ad libitum): PMI Nutrition International Certified Rodent Chow #5002 ad libitum
- Acclimation period: yes, but not specified


ENVIRONMENTAL CONDITIONS
- Temperature: 70 to 76 °F
- Humidity (%): 29 to 73
- Air changes (per hr): 10 to 15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
For each exposure group a specified amount of the test article and vehicle was mixed weekly. The mixtures were stirred continuously throughout each exposure period. The appearance of each test article preparation was determined and documented as clear colourless solution for 10 and 30 mg/kg/day and a clear pale blue solution for 50 mg/kg/day.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analytical concentration verification conducted throughout the study demonstrated that the exposure solutions were stable and properly prepared. All analyses were within ± 10 % of the nominal concentration.
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
once daily
Doses / concentrations
Remarks:
Doses / Concentrations:
10, 30 and 50 mg/kg bw/day (nickel sulfate hexahydrate)
Basis:
other: nominal dose
No. of animals per sex per dose:
60
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Doses were selected based on the data from a 90-day range finding study conducted with exposure levels of 0, 50, 75, 100, 125 and 150 mg/kg bw/day (nickel sulfate hexahydrate)

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations included: general health, mortality, moribundity


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly, starting on week 25 (including palpable mass examination: occurrence, size, location and description of any palpable masses, followed by persistence or disappearance being documented at the next weekly clinical observation)


BODY WEIGHT: Yes
- Time schedule for examinations: day -3, day 0, weekly during the first 13 weeks, once every 4 weeks thereafter and during week 103


FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes (g/animal/day)


HAEMATOLOGY: Yes
- Time schedule for collection of blood: week 54 (tail vein) and prior to scheduled euthanasia during week 104/105 (orbital plexus)
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10/sex/group
- Parameters examined: according to OECD 451 protocol (at least red blood cells, hemoglobin, hematocrit, MCH, MCHC, leukocytes, segmented neutrophils, eosinophils, basophils)


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: week 54 (tail vein) and prior to scheduled euthanasia during week 104/105 (orbital plexus)
- Animals fasted: No data
- How many animals: 10/sex/group
- Parameters examined: blood nickel concentration, other parameters according to OECD 451 protocol


URINALYSIS: Yes
- Time schedule for collection of urine: following exposure on day 1 during week 103
- Metabolism cages used for collection of urine: Yes (urine collection cages with fecal collection screens)
- Animals fasted: No data
- Parameters examined: urine and fecal nickel concentrations, creatinine, albumine

OTHER
Toxicokinetic evaluation: prior to scheduled euthanasia during week 104/105, blood was collected 30 min and 24 hours after gavage exposure.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes, at time of death or euthanasia (not further specified)
HISTOPATHOLOGY: Yes, tissues from all animals collected at necropsy (reported: pituitary gland, bronchi, spleen, mandibular lymph nodes, mesenteric lymph nodes, eye, adrenal, stomach, pancreas, aorta, thymus, kidneys)
Statistics:
Data on body weights, food consumption and hematology parameters (minimum of 3 animals/sex/group per interval) were initially tested for normality using Levene's test (Levene, 1960) for equality of variance followed by the Shapiro-Wilks test (Royston, 1995) for normality. A p ≤ 0.001 level of significance was required for either test to reject the assumptions. If both assumptions were fulfilled, a single-factor ANOVA (Gad and Weil, 1994) was applied, with animal grouping as the factor, utilizing a p ≤ 0.05 level of significance. If the parametric ANOVA was significant at p ≤ 0.05, Dunnett's test (Gad and Weil, 1994) was used to identify statistically significant differences between the control group and each nickel sulfate-treated group at the 0.05, 0.01 and 0.001 levels of significance. If either of the parametric assumptions was not satisfied, then the Kruskal-Wallis non-parametric ANOVA (Siegel, 1956) procedure was used to evaluate intergroup differences (p ≤ 0.05). The Dunn's multiple comparison test (Glantz, 1997) was applied if this ANOVA was significant, again utilizing significance levels of p ≤ 0.05, 0.01, 0.001.

Statistical analysis of survival rates for each group was performed by calculation of Kaplan-Meier estimates (Kaplan and Meier, 1958) by sex, and shown graphically. A log-rank dose response trend test of survival rates was performed utilizing dose coefficients. In addition, a log-rank test for survival was used to make pairwise comparisons of each treated group with the control group. Both the trend test and pairwise comparisons were conducted at the 0.05 significance level. Survival times in which the status of the animal's death was classified as an accidental death or terminal termination were considered censored values for the purpose of the Kaplan-Meier estimates and survival rate analyses.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
There was a variety of clinical signs noted throughout the study which was comparable to that in the control groups.
Increased mortality was observed in the treated groups due to pulmonary toxicity secondary to aspiration (dark red areas in the lungs) during the first 24 weeks of the study. There was no apparent treatment-related effect on mortality in the treated males. In females, there was an increasing exposure-response trend in mortality relative to controls (p ≤ 0.008).


BODY WEIGHT AND WEIGHT GAIN
Body weights decreased in a exposure-dependent manner, with significantly decreased body weights in the two highest exposure groups for males and females. Reductions in weight gain relative to controls at study week 103 reached the level of biological significance (i.e., > 10% decrease) in mid and high dose males and high dose females.

FOOD CONSUMPTION
Statistically significant decreases (males and females) and increases (females) in mean food consumption occurred sporadically in the treated groups. However, the differences were small (i.e., < 1g/animal/day) and did not parallel the decreased body weight gains.

HAEMATOLOGY
There were a few statistically significant differences in the treated animals, for example increases in red blood cells, hematocrit and/or hemoglobin in some animals of the mid and high dose groups. According to the authors, these changes may be associated with dehydration or nickel effects on gene expression of erytropoetin. However, none of these changes were considered toxicologically relevant since they were minor and lacked a consistent exposure-related pattern.

CLINICAL CHEMISTRY
No notable differences were observed between controls and treated animals during the toxicokinetic satellite study.

URINALYSIS
No notable differences were observed between controls and treated animals during the toxicokinetic satellite study.

GROSS PATHOLOGY
Numerous gross necropsy findings were observed, but type and incidence of these findings were comparable between animals in the control and the treated groups and were consistent with findings commonly seen in aging rats in a long-term study.

HISTOPATHOLOGY: NON-NEOPLASTIC
None of the findings were considered to be related to experimental exposure, they were either considered to be secondary to toxicity or incidental background occurrences. Some examples of non-neoplastic findings in high dose males include: Increases in hyperplasia of pars distalis of the pituitary gland, bronchial inflammation, lymphoid follicle atrophy of spleen, mandibular lymph node cystic degeneration, histiocytes infiltration of mesenteric lymph nodes, hyperkeratosis of the tail, eye mineralization, vacuolization of adrenal cortex, increase in the erosion of glands but decrease in epithelial erosion in the stomach, decrease in atrophy of pancreatic acinus, mineralization of aorta, hyperplasia of thymus, presence of renal tubule pigment.
Most of the effects were not seen in high dose females except the increases in bronchial inflammation, spleen and mandibular lymph node effects, decreases of kidney pigmentation, eye effects and erosion of stomach glands.

Increased bronchial inflammation was considered to be the indirect result of minor aspirations during gavage exposure.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
There were no treatment-related carcinogenic effects observed in this study. Only the incidence of keratoacanthoma (tail) was statistically significantly increased in low dose males (p < 0.001), but there was no dose-relationship, and the incidence rate (15%) was only slightly higher than the upper end of some of the reported historical control incidences for this tumor type.

HISTORICAL CONTROL DATA (if applicable)
The incidence of keratoacanthoma ranged between 0 to 14% (Haseman et al., 1998) and 0 to 2% (CRL-Ohio) in the two historical control databases utilized in this study.

OTHER FINDINGS
Toxicokinetic evaluation:
Steady state levels of nickel in blood increased with exposure, the nickel blood levels exceeded the control levels by a factor of approximately 100 for the low exposure group and over 350 in the two highest exposure groups. Twenty-four-hour urinary nickel levels also increased with exposure. Nickel levels in feces increased in an exposure-dependent manner, as well. The relatively high fecal levels compared to blood and urine demonstrated that the majority of nickel was not systemically absorbed, but was excreted in the feces.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
7.02 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: Recalculated value for Trinickel(2+) dicitrate from actual test substance
Dose descriptor:
LOAEL
Effect level:
21.1 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: body weight Recalculated value for Trinickel(2+) dicitrate from actual test substance
Dose descriptor:
NOAEL
Effect level:
10 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: Test substance: nickel sulfate hexahydrate
Dose descriptor:
LOAEL
Effect level:
30 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: body weight Test substance: nickel sulfate hexahydrate

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Male and female mortality during weeks 0 to 105:

Dose group

Male deaths/total (% mortality)

Female deaths/total (% mortality)*

0 mg/kg/d

36/60 (60)

14/60 (23)

10 mg/kg/d

29/60 (48)

20/60 (33)

30 mg/kg/d

30/60 (50)

26/60 (43)

50 mg/kg/d

34/60 (57)

27/60 (45)

*Increasing exposure-response trend in mortality relative to controls (p<0.008).

Summary of body weights at week 103:

Dose group

Male [g ± SD] (% of control)

Female [g ± SD] (% of control)

0 mg/kg/d

397 ± 49

285 ± 23

10 mg/kg/d

376 ± 49 (95)

273 ± 31 (96)

30 mg/kg/d

355 ± 46* (89)

263 ± 27* (92)

50 mg/kg/d

348 ± 42* (88)

257 ± 21* (90)

Male survival at week 103 was 27, 35, 34 and 31 animals for dose groups 0, 10, 30 and 50 mg/kg/d, respectively.

Female survival at week 103 was 47, 41, 37 and 35 animals for dose groups 0, 10, 30 and 50 mg/kg/d, respectively.

*p < 0.01

Summary of hematological changes§:

 

Males

Females

Hematological parameter

Week 54

Week 104/105

Week 54

Week 104/105

Red blood cells

--

G3: 13% (+)

--

--

Hemoglobin

--

--

--

G4: 11% (+)

Hematocrit

--

--

--

G3: 11% (+)

G4: 11% (+)

MCH

G3: 4% (-)

--

--

--

MCHC

G4: 5% (-)

--

--

--

Leukocytes

--

--

--

G2: 35% (+)

G3: 21% (-)

G4: 23% (-)

Seg neutrophils

--

--

--

G2: 29% (+)

G3: 34% (-)

G4: 28% (-)

Eosinophils

--

G4: 2900% (+)

--

--

Basophils

--

--

G3: 300% (+)

--

G1 (0 mg/kg/d); G2 (10 mg/kg/d); G3 (30 mg/kg/d); G4 (50 mg/kg/d)

§Only those groups with statistically significant increases (+) or decreases (-) compared to controls are shown.

Applicant's summary and conclusion