Nickel(2+) propionate

Endpoint summary

Description of key information

read across to nickel sulfate hexahydrate (CAS 101-97-0): oral NOAEL 10 mg/kg bw/d (OECD 451)

read across to nickel sulfate hexahydrate (CAS 101-97-0): inhal NOAEC 0.125 mg/m3 air (OECD 453)

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

chronic toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to section 13 for the read across-justification.

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEL

Effect level:

10 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

Key result

Critical effects observed:

no

Reference 2

Endpoint:

chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: EPA OPPTS 870.4200

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 451

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: CDF(344)/CrlBR

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: 6 weeks
- Weight at study initiation: 118 to 147 g for males and 93 to 112 g for females
- Housing: housed individually in suspended stainless steel cages that were rotated in a regular fashion
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: acclimated to the laboratory conditions prior to in-life initiation
- Other: The results of the pretest health screen (gross necropsy and serological analyses) conducted prior to in-life initiation indicated that the population of animals was suitable for study use. Serological analyses of blood samples fromfive male and five female sentinel animals conducted by BioReliance Corporation, Rockville, Maryland, during weeks 25, 51, 77 and 103 did not reveal the presence of any viral infections that would negatively impact the results of this study.

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

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: 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 a clear colorless solution for groups 2 and 3 (10 and 30 mg/kg bw/day) and a clear pale blue solution for group 4 (50 mg/kg bw/day).

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses were conducted by KAR Laboratories, Inc. (Kalamazoo, Michigan) prior to study initiation, during week 51, and following study completion to confirm the stability and purity of the test substance. Reverse osmosis deionized tap water was used for administration to control animals and in the preparation of the test article mixtures. Analytical concentration verification analyses 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:

daily

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

referred to as group 1

Dose / conc.:

10 mg/kg bw/day (nominal)

Remarks:

referred to as group 2

Dose / conc.:

30 mg/kg bw/day (nominal)

Remarks:

referred to as group 3

Dose / conc.:

50 mg/kg bw/day (nominal)

Remarks:

referred to as group 4

No. of animals per sex per dose:

60

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale:
Exposures for the 90-day range finding study were selected based on previous gavage studies of nickel sulfate hexahydrate in rats. Two reproductive studies using Sprague–Dawley rats indicated that graded daily exposures from 5 to 125 mg/kg bw/day for one and two generations (>90 days in two generation study) resulted in few overt signs of toxicity. These studies also demonstrated the onset of lethality from administration of nickel sulfate hexahydrate at 150 mg/kg bw/d.
The 90-day range-finding study of nickel sulfate hexahydrate administered by gavage was conducted using exposures of 0, 50, 75, 100, 125, and 150 mg/kg bw/d. Based on the data from the 90-day range-finding study, exposure levels of 10, 30 and 50 mg/kg bw/day were selected for the 2 year oral gavage carcinogenicity study.

-Rationale for animal assignment: Sixty female and sixty male animals were assigned to each exposure group using a computer randomization program.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: General health/mortality/moribundity checks were performed twice daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Detailed clinical observations were performed weekly and on the day of scheduled euthanasia (weeks 104–105). Beginning on week 25, detailed clinical observations included a palpable mass examination (including the occurrence, size, location and description of any palpable masses) followed by persistence or disappearance of these masses being documented at the next weekly clinical observation.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded prior to randomization (day −3), on day 0 (i.e., the start of exposure), weekly during the first 13 weeks, once every 4 weeks thereafter and during week 103.

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Individual food consumption (grams/animal/day) was recorded on day 0, weekly during the first 13 weeks and once every 4 weeks thereafter, with the final food consumption measurement during week 103.

HAEMATOLOGY: Yes
- Selected hematological parameters were measured in blood samples collected from 10 animals/sex/group during week 54 (via tail vein) and prior to scheduled euthanasia during week 104/105 (via orbital plexus). Hematology and clinical chemistry parameters were measured according to the OECD 451 protocol.

Sacrifice and pathology:

GROSS PATHOLOGY/HISTOPATHOLOGY:
All animals were subjected to a complete gross necropsy examination at the time of death or euthanasia. Tissues collected at necropsy from all animals were processed for histopathological evaluation. Slides were prepared by Histo Techniques (Powell, Ohio) and Charles River Laboratories-Pathology Associates (Frederick, Maryland) and were examined microscopically by a Charles River Laboratories board-certified veterinary pathologist.

Other examinations:

Near the end of the study (week 103), additional biological sampling was performed to provide data on nickel in urine, feces and blood. Immediately following exposure on 1 day during week 103, five females and five males from each exposure group were placed in urine collection cages equipped with fecal collection screens, and an ice bath for cooling collected urine samples. Blood was collected from the orbital plexus of each animal approximately 30 min and 24 h post-exposure and sent to WIL Research Laboratories, Inc. (Ashland, Ohio) for analysis of blood nickel concentration. Urine and fecal samples were collected from each cage approximately 24 h post-exposure and sent to KAR Laboratories, Inc. for urine and fecal analysis of nickel concentrations. Urine was analyzed also for creatinine and albumin concentrations. Other standard hematology and clinical chemistry parameters for blood as well as other standard urinalysis parameters for urine were measured by Charles River Laboratories.

Statistics:

In-life data: The data were initially tested for normality using Levene's test for equality of variance followed by the Shapiro–Wilks test for normality.
A p≤0.001 level of significance was required for either test to reject the assumptions. If both assumptions were fulfilled, a singlefactor ANOVA 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 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 nonparametric ANOVA procedure was used to evaluate intergroup differences (p≤0.05). The Dunn's multiple comparison test was applied if this ANOVA was significant, again utilizing significance levels of p≤0.05, 0.01 and 0.001.

Survival Data: Kaplan–Meier estimates of group survival rates were calculated, 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.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

The type and incidence of clinical signs observed in the treated groups were generally comparable to those observed in the control group.

Mortality:

mortality observed, treatment-related

Description (incidence):

There was a higher rate of mortality in groups 2–4 treated males and females during the first 24 weeks of this study which appeared to be nickel sulfate-related. Nickelinduced pulmonary toxicity secondary to aspiration of the nickel sulfate solution was a potential cause. A later exposure time after week 24 (since rats are nocturnal feeders and 10 mL/kg exposure volume early in the morning to animals with relatively full stomachs may have produced sufficient gastric back pressure to force a portion of the administered dose to the opening of the trachea where it was aspirated) was effective in increasing survival, possibly by reducing aspiration of the nickel sulfate.
Mortality during week 24-48: only one death in nickel sulfate-treated group 3.
For the entire 104 weeks period there was no apparent treatment-related effect on mortality in males. In females, there was an increasing exposure–response trend in mortality relative to the controls (p<0.008).

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights decreased in a exposure-dependent manner, with significantly decreased body weights observed in the two highest exposure groups for males and females (groups 3–4) Reductions in weight gain relative to controls at study week 103 reached the level of biological significance (i.e., >10% decrease) in the group 3 and 4 males and the group 4 females. This significant weight reduction indicates that the Maximum Tolerated Dose was reached in this study for both males and females.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

A few statistically significant differences in the hematology data were observed in the nickel sulfate-treated males and females. For example, there were increases in red blood cells, hematocrit and/or hemoglobin in some of the animals in the 30 and 50 mg/kg bw/day groups. These changes may be associated with dehydration or could be related to nickel effects on gene expression of erytropoetin (HIF-inducible factor). However, none of these differences was suggestive of a hyperplastic (i.e., leukemia) response and none of these changes was considered toxicologically meaningful since they were small and did not follow a consistent exposure-related pattern.

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:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Numerous gross necropsy findings were observed for animals in the control and nickel sulfate-treated groups but the type and incidence of these findings observed for the treated animals were comparable to those observed in the control group, and were consistent with findings commonly seen in aging rats in a longterm study. None of the neoplastic or non-neoplastic microscopic findings was considered to be related to the experimental exposures. The non-neoplastic findings were either considered to be secondary to toxicity or incidental background occurrences rather than a direct effect of nickel sulfate. Some examples of non-neoplastic findings in the 50mg/kg bw/day males include: increases in yperplasia 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 and vacuolization of adrenal cortex. In the stomach, there was an increase in the erosion of glands, but a decrease in epithelial erosion. Decreases in atrophy of pancreatic acinus, mineralization of aorta, hyperplasia of thymus and presence of renal tubule pigment were also observed. Most of these effects were not observed in the 50 mg/kg bw/day female animals with the exception of the increases in bronchial inflammation, spleen and mandibular lymph node effects and the decreases seen for kidney pigmentation, eye effects and erosion of stomach glands. The increased bronchial inflammation seen in 50 mg/kg bw/day male and female rats was considered to be the indirect result of minor aspirations during gavage exposure.

Histopathological findings: neoplastic:

no effects observed

Details on results:

The pathology report, pathology peer-review and the pathology working group concurred that nickel sulfate hexahydrate did not cause any carcinogenic effects in this study. Analysis of the tumor data revealed only one statistically significant (p<0.001) increase in tumors corresponding to keratoacanthoma (tail) in the group 2 males. However, this finding is of questionable toxicologic significance since there was no exposure–response relationship, the incidence rate in the group 2 males (15%) was only slightly higher than the upper end of Haseman's historical control incidence for this tumor type (0–14%) and the incidence rate in the remaining control and treated groups (0–7%) was within the range of the CRL-Ohio historical incidence (0–2%) and the Haseman historical incidence (0–14%). No other tumor finding in this study was statistically significant.
No notable differences were observed between controls and treated animals for the hematology, biochemistry and urinalysis parameters measured during the toxicokinetic satellite study.
Nickel levels in feces increased in an exposure-dependent manner in the treated males and females. The relatively high fecal levels compared to the blood and urinary nickel levels demonstrated that the majority of the nickel the animals were exposed to was not systemically absorbed, but was excreted in the feces.

Dose descriptor:

LOAEL

Effect level:

6.7 other: Ni/kg bw/d

Sex:

male/female

Basis for effect level:

body weight and weight gain

Dose descriptor:

LOAEL

Effect level:

30 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

Dose descriptor:

NOAEL

Effect level:

2.2 other: Ni/kg bw/d

Sex:

male/female

Basis for effect level:

other: overall effects

Key result

Dose descriptor:

NOAEL

Effect level:

10 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects

Key result

Critical effects observed:

no

Conclusions:

The NOAEL of the test substance was determined to be 10 mg/kg bw/d.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

10 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Guideline and GLP study

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

chronic toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For justification of read across, please refer to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEC

Effect level:

0.125 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects

Remarks on result:

other: equivalent to 0.027 mg Ni/m3 air

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

0.25 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

lungs

Treatment related:

yes

Reference 2

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 1988 to May 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

other: F344/N

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Germantown, NY
- Housing: Hazleton 2000 whole-body chambers
- Diet: ad libitum during non-exposure periods
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 hr dark, 12 hr light

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

water

Remarks on MMAD:

MMAD / GSD: MMAD =2.08-2.52 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel multitiered whole exposure chambers (Hazleton, Aberdeen, MD, USA)
- Source and rate of air: High-efficiency particulate air filter (Flanders, Washington, DC)
- System of generating aerosols: Aerosols were generated by nebulization of test substance solutions (62.1 g/L in distilled and deionized water)
- Method of particle size determination: Aerosol concentration was determined by taking three 2-h filter samples throughout the exposure day.
Real-time determination of aerosol concentration was made using real time aerosol monitor - model S units. Aerosol size was determined using cascade impactors. (The range of mass median aerodynamic diameters and GSD obtained throughout the study were 2.2-2.5 um and GSD=2.2)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Aerosol concentration was determined by taking three 2-h filter samples throughout the exposure day. Real-time determination of aerosol concentration was made using real time aerosol monitor - model S units. Aerosol size was determined using cascade impactors.

Duration of treatment / exposure:

6h /d

Frequency of treatment:

5 d/wk, 2 yr

Dose / conc.:

1 mg/m³ air (nominal)

Dose / conc.:

0.5 mg/m³ air (nominal)

Dose / conc.:

0.25 mg/m³ air (nominal)

Dose / conc.:

0.125 mg/m³ air (nominal)

Dose / conc.:

0 mg/m³ air (nominal)

No. of animals per sex per dose:

Groups of 63 to 65 male and 63 to 64 female rats

Control animals:

yes

Details on study design:

- Dose selection rationale: based on previous 13-week study

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: every 4 weeks

BODY WEIGHT: Yes
- Time schedule for examinations: every 4 weeks

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, complete necropsies were done on all animals. At necropsy, all organs and tissues were examined for grossly visible lesions, and all major tissues and lesions were preserved in 10 % neutral-buffered formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin for microscopic examination.
HISTOPATHOLOGY: Yes. Complete histopathology was performed on high-exposure and control groups and to a no-effect level in target tissues.

Other examinations:

Ni concentration in the lungs

Statistics:

Tests of significance included pairwise comparisons of each exposed group with controls and a test for overall exposure-related trends. Organ and body weight data were analyzed using parametric multiple comparison procedures, and lung burden data were analyzed using nonparametric multiple comparison methods. The reported values were considered significant at the P < 0.05 level.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The final mean body weights compared to the control group per 0.125 mg/m3, 0.25 mg/m3 and 0.5 mg/m3 exposure groups were 99 %, 101 % and 98 %, respectively for the male rats and 97 %, 97 % and 94 % for the females, respectively.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Lung weights in exposed animals were greater than controls, this was considered to be related to inflammatory lung reactions that occurred in response to test substance exposure. At 15 months, the lung weights of in the high exposure group was 33-41 % more compared to the control.

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

A spectrum of exposure-related nonneoplastic respiratory tract lesions seen after exposure included focal alveolar/bronchiolar hyperplasia, inflammation, and/or fibrosis of the lung and lymphoid hyperplasia of the lung-associated lymph nodes. Atrophy of the olfactory epithelium was also seen after exposure.

Histopathological findings: neoplastic:

no effects observed

Details on results:

GROSS & HISTOPATHOLOGY:
A spectrum of exposure-related nonneoplastic respiratory tract lesions included: focal alveolar/bronchiolar hyperplasia, inflammation, and/or fibrosis of the lung and lymph oid hyperplasia of the lung-associated lymph nodes, and atrophy of the olfactory epithelium.

There were no increases in lung neoplasms in rats or mice exposed to nickel sulfate. The A/B neoplasms that were observed in the exposed groups were similar in incidence and morphology to those observed in controls.

OTHER FINDINGS:
The lung burden at 7 or 15 months in rats and mice was 1-2 µg Ni/g lung.

Dose descriptor:

LOAEC

Effect level:

0.25 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: chronic active lung inflammation

Remarks on result:

other: equivalent to 0.056 mg Ni/m3

Key result

Dose descriptor:

NOAEC

Effect level:

0.125 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects

Remarks on result:

other: equivalent to 0.027 mg Ni/m3

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

0.25 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

lungs

Treatment related:

yes

Conclusions:

The NOAEL of the test substance as aerosol was found to be 0.125 mg/m3 air.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

0.125 mg/m³

Study duration:

chronic

Species:

rat

Quality of whole database:

Guideline and GLP study

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Reference 1

Endpoint:

chronic toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For justification of read across, please refer to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOAEC

Effect level:

0.125 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects

Remarks on result:

other: equivalent to 0.027 mg Ni/m3 air

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

0.25 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

lungs

Treatment related:

yes

Reference 2

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 1988 to May 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

other: F344/N

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Germantown, NY
- Housing: Hazleton 2000 whole-body chambers
- Diet: ad libitum during non-exposure periods
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 hr dark, 12 hr light

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

water

Remarks on MMAD:

MMAD / GSD: MMAD =2.08-2.52 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel multitiered whole exposure chambers (Hazleton, Aberdeen, MD, USA)
- Source and rate of air: High-efficiency particulate air filter (Flanders, Washington, DC)
- System of generating aerosols: Aerosols were generated by nebulization of test substance solutions (62.1 g/L in distilled and deionized water)
- Method of particle size determination: Aerosol concentration was determined by taking three 2-h filter samples throughout the exposure day.
Real-time determination of aerosol concentration was made using real time aerosol monitor - model S units. Aerosol size was determined using cascade impactors. (The range of mass median aerodynamic diameters and GSD obtained throughout the study were 2.2-2.5 um and GSD=2.2)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Aerosol concentration was determined by taking three 2-h filter samples throughout the exposure day. Real-time determination of aerosol concentration was made using real time aerosol monitor - model S units. Aerosol size was determined using cascade impactors.

Duration of treatment / exposure:

6h /d

Frequency of treatment:

5 d/wk, 2 yr

Dose / conc.:

1 mg/m³ air (nominal)

Dose / conc.:

0.5 mg/m³ air (nominal)

Dose / conc.:

0.25 mg/m³ air (nominal)

Dose / conc.:

0.125 mg/m³ air (nominal)

Dose / conc.:

0 mg/m³ air (nominal)

No. of animals per sex per dose:

Groups of 63 to 65 male and 63 to 64 female rats

Control animals:

yes

Details on study design:

- Dose selection rationale: based on previous 13-week study

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: every 4 weeks

BODY WEIGHT: Yes
- Time schedule for examinations: every 4 weeks

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, complete necropsies were done on all animals. At necropsy, all organs and tissues were examined for grossly visible lesions, and all major tissues and lesions were preserved in 10 % neutral-buffered formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin for microscopic examination.
HISTOPATHOLOGY: Yes. Complete histopathology was performed on high-exposure and control groups and to a no-effect level in target tissues.

Other examinations:

Ni concentration in the lungs

Statistics:

Tests of significance included pairwise comparisons of each exposed group with controls and a test for overall exposure-related trends. Organ and body weight data were analyzed using parametric multiple comparison procedures, and lung burden data were analyzed using nonparametric multiple comparison methods. The reported values were considered significant at the P < 0.05 level.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The final mean body weights compared to the control group per 0.125 mg/m3, 0.25 mg/m3 and 0.5 mg/m3 exposure groups were 99 %, 101 % and 98 %, respectively for the male rats and 97 %, 97 % and 94 % for the females, respectively.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Lung weights in exposed animals were greater than controls, this was considered to be related to inflammatory lung reactions that occurred in response to test substance exposure. At 15 months, the lung weights of in the high exposure group was 33-41 % more compared to the control.

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

A spectrum of exposure-related nonneoplastic respiratory tract lesions seen after exposure included focal alveolar/bronchiolar hyperplasia, inflammation, and/or fibrosis of the lung and lymphoid hyperplasia of the lung-associated lymph nodes. Atrophy of the olfactory epithelium was also seen after exposure.

Histopathological findings: neoplastic:

no effects observed

Details on results:

GROSS & HISTOPATHOLOGY:
A spectrum of exposure-related nonneoplastic respiratory tract lesions included: focal alveolar/bronchiolar hyperplasia, inflammation, and/or fibrosis of the lung and lymph oid hyperplasia of the lung-associated lymph nodes, and atrophy of the olfactory epithelium.

There were no increases in lung neoplasms in rats or mice exposed to nickel sulfate. The A/B neoplasms that were observed in the exposed groups were similar in incidence and morphology to those observed in controls.

OTHER FINDINGS:
The lung burden at 7 or 15 months in rats and mice was 1-2 µg Ni/g lung.

Dose descriptor:

LOAEC

Effect level:

0.25 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: chronic active lung inflammation

Remarks on result:

other: equivalent to 0.056 mg Ni/m3

Key result

Dose descriptor:

NOAEC

Effect level:

0.125 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects

Remarks on result:

other: equivalent to 0.027 mg Ni/m3

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

0.25 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

lungs

Treatment related:

yes

Conclusions:

The NOAEL of the test substance as aerosol was found to be 0.125 mg/m3 air.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

0.125 mg/m³

Study duration:

chronic

Species:

rat

Quality of whole database:

Guideline and GLP study

Additional information

No data on the substance itself is available. Therefore, read across to nickel sulfate hexahydrate (source substance 2) was applied.

Oral

An oral carcinogenicity study according to OECD 451 and EPA OPPTS 870.4200 was conducted with nickel sulfate hexahydrate (Heim et al., 2007). Male and female Fischer CDF(344)/CrlBR rats were assigned to the dose groups 0 (group 1), 10 (group 2), 30 (group 3) or 50 mg/kg bw/d (group 4). The test group animals (60 males and 60 females per dose) received the test material daily via gavage (amount 10 mL, vehicle: water) for a period of 104 weeks. For the entire 104 weeks period there was no apparent treatment-related effect on mortality in males. In females, there was an increasing exposure–response trend in mortality relative to the controls (p<0.008). Body weights decreased in a exposure-dependent manner, with significantly decreased body weights observed in the two highest exposure groups for males and females (groups 3–4). Reductions in weight gain relative to controls at study week 103 reached the level of biological significance (i.e., >10% decrease) in the group 3 and 4 males and the group 4 females. This significant weight reduction indicates that the Maximum Tolerated Dose was reached in this study for both males and females. No notable differences were observed between controls and treated animals for the hematology, biochemistry and urinalysis parameters measured during the toxicokinetic satellite study. The results of this study indicate that nickel sulfate hexahydrate does not cause carcinogenicity to rats when administered orally. Based on the decreased body weights the NOAEL of the test substance was determined to be 10 mg/kg bw/d.

Inhalation

An inhalation carcinogenicity study was conducted similar to OECD Guideline 453 with F344/N rats (Dunnick et al., 1995). The test animals were exposed to the test material nickel sulfate hexahydrate as aerosol in the following nominal concentrations: 0, 0.125, 0.25, 0.5 and 1 mg test substance/m3 air. One dose group consisted of 63 to 65 male and 63 to 64 female rats. The animals were treated for 2 years, 6h/d for 5 days per week. Detailed clinical observations were performed every 4 weeks during the study. After study termination, complete necropsies were done on all animals. As a result, no effects concerning clinical signs or mortality were observed. The final mean body weights compared to the control group per 0.125 mg/m3, 0.25 mg/m3 and 0.5 mg/m3 exposure groups were 99 %, 101 % and 98 %, respectively for the male rats and 97 %, 97 % and 94 % for the females, respectively. The lung weights in the exposed animals were greater than in the controls, this was considered to be related to inflammatory lung reactions that occurred in response to test substance exposure. At 15 months, the lung weights of in the high exposure group was 33-41 % more compared to the control. There were no increases in lung neoplasms in rats exposed to the test substance. A spectrum of exposure-related non-neoplastic respiratory tract lesions seen after exposure included focal alveolar/bronchiolar hyperplasia, inflammation, and/or fibrosis of the lung and lymphoid hyperplasia of the lung-associated lymph nodes. Atrophy of the olfactory epithelium was also seen after exposure. Based on the inflammatory effects in the lung the NOAEC of the test substance as aerosol was determined to be ca. 0.125 mg/m3 air, equivalent to 0.027 mg Ni/m3 air.

 

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008

The studies were considered reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. Based on the results, the target and source substance are to be classified for specific target organ toxicity after repeated inhalation exposure with STOT Rep. Exp.1 and labelled with H372 (Causes damage to organs (lung) through prolonged or repeated exposure), according to Regulation (EC) No 1272/2008 (CLP), as amended for the fifteenth time in Regulation (EU) No 2020/1182.