Zinc nitrate

Endpoint summary

Description of key information

Zinc nitrate was tested in a mouse local lymph node assay (Plodikova, 2010). Five Balb/c mice per group were exposed on the dorsum of both ears once a day by test and control substances during 3 consecutive days. Concentrations were 30%, 3%, 0.3% (w/v) in DAE 433 (mixture of 40% dimethylacetamide, 30% acetone and 30% ethanol). Lymph node lymphocyte proliferation was determined by tritiated thymidin incorporation. The ratio of the proliferation in treated groups to that in vehicular controls, termed the Stimulation Index, was determined. The test substance caused a dose dependent increase in radioisotope incorporation into the DNA of dividing lymphocytes, with a significant ratio of 4.19 at 30%. The test substance also showed a tendency to increased ear weight at the 30% concentration, which could also be a sign of irritation of the skin. The animals exposed to the test substance at all concentrations showed no further pathological skin reactions and no other negative clinical symptoms of intoxication throughout the experiment. The positive result could be due a contact allergen in mice but potential irritation effect does not rule out the possibility that it could be false positive result.

The skin sensitising potential of zinc nitrate was also investigated in guinea pigs to rule out whether it has an allergenic effect or not (Slais, 2010). A well-performed maximisation test, conducted according to OECD guideline 406, was carried out in albino guinea pigs. A pilot study for establishing of the dose for the main study was conducted first. Three guinea pigs were exposed to three doses (10, 70 and 500 mg/animal) of the Test item for 4 hours. The animals were observed for skin reaction 24, 48 and 72 hours after the exposure. Since no skin reaction was observed, a dose of 500 mg/animal was chosen for the main study. The tested animals in the main study were treated by three inductions – topic application with one week intervals. The negative control animals were treated only with Sterilux in the same manner. The positive control animals were treated with the reference item (2-mercaptobenzothiazole) in the dose of 0.5 mL/animal. Two weeks after the last induction, a topical challenge was performed in the treated and negative control animals. The positive control animals were treated with the reference item. At the intervals of 24 and 48 hours after the challenge exposure, the skin reaction of all the animals was evaluated. Daily clinical observations and weekly body weight values were recorded. No sensitizing effect of the Test item zinc nitrate was observed in any of the animals after the challenge exposure. The clinical observations of the animals were without any pathological findings related to the treatment. The body weight values of all the animals increased during the study without abnormalities and corresponded to the age of the animals. Non-continuous or patchy erythema was observed in two positive control animals after the challenge exposure; no reactions were observed in the negative control animals. Based on these results the test system was considered to be reliable. Under the test conditions used the Test item zinc nitrate was assessed to be not sensitizing.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

an in vitro skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study are available

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The metals industry has historical data to indicate that metals can induce false positives/negatives in LLNA studies; this is confirmed from experiences in test labs.
Zinc nitrate hexahydrate was tested for the sensitisation potential first in the murine local lymph node assay (LLNA). Zinc nitrate has a positive result in the LLNA test. Positive results in cell proliferation revealed that the test substance could be a contact allergen in mice but potential irritation effect does not rule out the possibility that it could be false positive result.
The current study (guinea pig maximisation test) should rule out whether the test material has an allergenic effect or not.

Species:

guinea pig

Strain:

other: albino

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Biotest s.r.o.
- Age at study initiation: 15-20 weeks
- Weight at study initiation: M: 492-1012g, F: 564-844g
- Housing: individually in environmentally monitored and ventilated experimental room No2, part 1, building No2
- Diet : standard pelletized diet diet KKK/O ad libitum
- Water: water of monitored quality ad libitum
- Acclimation period: 5days for the pilot study and 13 days for the main study

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To:

Route:

epicutaneous, open

Vehicle:

water

Concentration / amount:

500mg/animal

Route:

epicutaneous, open

Vehicle:

water

Concentration / amount:

500 mg/animal

No. of animals per dose:

in main study: 20 tested, 10 negative control
in pilot study: 3

Details on study design:

RANGE FINDING TESTS:
The pilot study with three animals was performed before the main test to provide data for establishing of the dose of the Test item to be used in the main study.
Three guinea pigs were administered topically on shaved skin of area 25×25 mm with three different doses of the Test item. The doses were 10 mg, 70 mg and 500 mg/animal. The Test item was moisturized with water to obtain a paste before the application. After the administration, the test area was covered with porous gauze dressing. The exposure lasted 4 hours. After the exposure, the test area was cleaned with water and the animals were observed for skin reaction 24, 48 and 72 hours after the exposure. Since no skin irritation was observed in any of the observation intervals, the dose of 500 mg/animal was used for induction and challenge exposures.

MAIN STUDY
A. INDUCTION EXPOSURE
Phases I. (Day 1), II.(Day 8) and III. (Day 15):
500mg/animal of the test item was applied on the shaved area of skin and covered with porous gauze dressing. The duration of induction exposures was 6 hours. After 6 hours, the Test item was removed and the application area was washed with water. The shaved skin area of control group animals was only covered with the 4-stratums of Sterilux ES (25×25 mm) and covered with adhesive non irritating tape. The shaved skin area of the positive control group animals was administered with the reference item in the dose of 0.5 mL/animal and covered with the 4-stratums Sterilux ES (25×25 mm) and adhesive non irritating tape.

B. CHALLENGE EXPOSURE
Provocation – challenge was performed two weeks after the last induction (Day 29). After shaving, a dose of 500 mg/animal of the Test item was moisturized with 0.5 mL water for injections to obtain a paste and applied on the shaved area (25×25 mm) of skin of all the tested and control (negative only) animals and covered with a porous gauze dressing. The challenge exposure was performed on the left hip of all the animals. The duration of
challenge exposure was 6 hours. After 6 hours, the Test item was removed and the application sites were cleaned with water.
The positive control group animals were administered in the same manner, but with the reference item in the dose of 0.5 mL/animal.
Twenty-one hours after the end of challenge exposure, the rests of fur on test area were shaved to ensure clear skin for skin reaction evaluation. In the intervals of 24 and 48 hours after the challenge, the exposure skin reaction of all the animals was evaluated.

OTHER: Clinical observations
-clinical observations and mortality:
once a day during acclimationand study period. Clinical Observations included: Signs of toxicity, changes in the skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous system, somatomotor activity and behaviour pattern, changes in gait, posture and response to handling, the presence of clonic or tonic movements and stereotypes.
-body weight: All guinea pigs were individually weighed at the delivery, immediately before the first administration and than weekly.
-skin reaction:
21 hours after removing the patch the challenge area was cleaned and closely-clipped
3 hours later (approximately 30 hours from the start of the challenge application) the skin reaction was observed and recorded according to the grades shown below.
24 hours after this observation a second observation (54 hours after the start) was made and once again recorded.
The skin reaction for erythema and oedema was graded according to following Magnusson and Kligman scale:

Reaction Numerical grading
No visible changes 0
Non-continuous or patchy erythema 1
Moderate and merged erythema 2
Severe erythema and oedema 3
The test system is considered reliable if the positive control group comprises min. 15% of the animals with positive reaction. This condition was fulfilled as 2/10 (20%) of the animals reacted positively.

Challenge controls:

positive control: 2-mercaptobenzothiazole, negative control: sterilux

Positive control substance(s):

yes

Remarks:

2-mercaptobenzothiazole

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

500mg/animal

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

no pathological changes. No changes in the gait, somatomotor activity or behavior pattern

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

500mg/animal

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

no pathological changes. No changes in the gait, somatomotor activity or behavior pattern

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no pathological changes. No changes in the gait, somatomotor activity or behavior pattern

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no pathological changes. No changes in the gait, somatomotor activity or behavior pattern

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

0.5mL/animal

No. with + reactions:

2

Total no. in group:

10

Clinical observations:

no pathological changes. No changes in the gait, somatomotor activity or behavior pattern

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

0.5mL/animal

No. with + reactions:

2

Total no. in group:

10

Clinical observations:

no pathological changes. No changes in the gait, somatomotor activity or behavior pattern

Remarks on result:

positive indication of skin sensitisation

The body weight gains of all the animals during the study corresponded to their age and were without any abnormalities.

Interpretation of results:

GHS criteria not met

Conclusions:

No sensitizing effect of the Test item Zinc nitrate hexahydrate was observed in any of the animals after the challenge exposure. The clinical observations of the animals were without any pathological findings. The body weight values of all the animals increased during the study without abnormalities and corresponded to the age of the animals.
Non-continuous or patchy erythema was observed in two positive control animals after the challenge exposure; no reactions were observed in the negative control group. Based on these results the test system can be considered to be reliable.
Under the test conditions used the Test item Zinc nitrate hexahydrate was assessed to be not sensitizing.

Executive summary:

SUMMARY

The aim of the present study was to estimate a potential sensitization effect of the Test item Zinc nitrate hexahydrate on intact skin of the guinea pig (according to OECD 406 and EN ISO 10993-10 ).

METHOD

Three animals for the pilot study and 20 test animals, 10 negative control animals were used for the study. The Buehler test was chosen according to properties of the Test item.

A pilot study for establishing of the dose for the main study was conducted first. Three guinea pigs were exposed to three doses (10, 70 and 500 mg/animal) of the Test item for 4 hours. The animals were observed for skin reaction 24, 48 and 72 hours after the exposure. Since no skin reaction was observed, a dose of 500 mg/animal was chosen for the main study.

The tested animals in the main study were treated by three inductions – topic application with one week intervals. The negative control animals were treated only with Sterilux in the same manner. The positive control animals were treated with the reference item (2 -mercaptobenzothiazole) in the dose of 0.5 mL/animal. Two weeks after the last induction, a topical challenge was performed in the treated and negative control animals. The positive control animals were treated with the reference item. At the intervals of 24 and 48 hours after the challenge exposure, the skin reaction of all the animals was evaluated. Daily clinical observations and weekly body weight values were recorded.

RESULTS

No sensitizing effect of the Test item zinc nitrate hexahydrate was observed in any of the animals after the challenge exposure. The clinical observations of the animals were without any pathological findings related to the treatment. The body weight values of all the animals increased during the study without abnormalities and corresponded to the age of the animals.

Non-continuous or patchy erythema was observed in two positive control animals after the challenge exposure; no reactions were observed in the negative control animals. Based on these results the test system was considered to be reliable.

Under the test conditions used the Test item zinc nitrate hexahydrate was assessed to be not sensitizing.

Reference 3

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

Balb/c

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Breeding farm VELAZ s.r.o., Kolec u Kladna, Czech Republic
- Age at study initiation: 8-10 weeks
- Weight at study initiation: 18.7-21.7g
- Housing: maximum six in macrolon cages (35X20X15cm) with sterilized softwood shavings
- Diet: pelleted standard diet for experimental animals ad libitum (ST1 BERGMAN)
- Water: drinking tap water ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22.5-23.4
- Humidity (%): 41-48
- Photoperiod (hrs dark / hrs light): 12/12

Vehicle:

other: DAE 433 (mixture of 40% dimethylacetamide, 30% acetone and 30% ethanol)

Concentration:

30%, 3%, 0.3% (w/v)

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
in pilot experiment, the highest concentration 30% (maximum technically practicable concentration) was administered to 3 animals to assess and/or discard a possible systemic toxicity or high irritation of skin. The route of administration was the same as in the main study. During the pilot experiment no test item related effects were found in all three animals, respectively no clinical symptoms of systemic toxicity and no macroscopic changes (after necropsy) were detected.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: LLNA
- Criteria used to consider a positive response: if the simulation index (SI) is ≥3 , and the response increases in dose-related manner (dose-response relationship)
- dosage volume: 25µl/ear /animal

TREATMENT PREPARATION AND ADMINISTRATION:
all suspensions were prepared by mixing an appropriate amount of zinc bis(dihydrogen phosphate) (1.5g, 0.15g or 0.015g) and the vehicle to obtain the application form (3X5mL) in concentration of 30%, 3% or 0.3% (w/v). The suspensions were prepared before the start of application by mixing on mangetic stirrer and then were still mixed during application. Suspensions were prepared on each day immediately before administration (10-20min)

Positive control substance(s):

other: dinitrochlorobenzene

Statistics:

Kruskal-Wallis test: for the comparision of the measured effect in all treatment groups with the vehicle control group, as global test
Mann-Whitney test: for all 2-group comparisions

Parameter:

SI

Value:

9.29

Test group / Remarks:

positive control

Remarks on result:

other: positive control

Parameter:

SI

Value:

1

Test group / Remarks:

negative control

Remarks on result:

other: negative control

Parameter:

SI

Value:

4.19

Test group / Remarks:

30% test substance

Remarks on result:

other: 30% test substance

Parameter:

SI

Value:

2.68

Test group / Remarks:

3% test substance

Remarks on result:

other: 3% test substance

Parameter:

SI

Value:

0.99

Test group / Remarks:

0.3% test substance

Remarks on result:

other: 0.3% test substance

group	radioisotope incorporation		ear weight
	mean disintegrations per minute (DPM)	SI	mean (mg)
negative control	799.43	1.00	23.66
positive control	7427.57	9.29+	38.88*
30%	3346.85	4.19 +	36.14*
3%	2138.49	2.68	24.18
0.3%	795.30	0.99	23.30

*= statistically significant p<0.05 (Mann-Whitney test)

+= values ≥3

Interpretation of results:

study cannot be used for classification

Remarks:

Test substance had a positive result in LLNA test, but potential irriation effect does not rule out the possibility that it could be false positive result.

Conclusions:

Test substance had a positive result in LLNA test, but potential irriation effect does not rule out the possibility that it could be false positive result.

Executive summary:

The test substance, zinc nitrate hexahydrate was tested for the assessment of skin sensitisation potential with the murine local lymph node assay.

The local lymph node assay (LLNA) with radionuclides was used. The testing was conducted according to the EU Method B.42, skin sensitization: local lymph node assay. In this study the contact allergenic potential of zinc nitrate hexahydrate was evaluated after topical application to female BALB/c mice. Five mice per group were exposed on the dorsum of both ears once a day by test and control substances during 3 consecutive days. Primary proliferation of lymphocytes in the lymph node draining the site of application was evaluated on the base on using radioactive labelling. The ratio of the proliferation in treated groups to that in vehicular controls, termed the Stimulation index, was determined. Statistical evaluation of ear weight was performed for elimination of false positive findings with certain skin irritants.

Concentrations: positive control DNCB: 0.5% (w/v) and zinc nitrate hexahydrate: 30%, 3%, 0.3% (w/v) in DAE 433.

The animals exposed to the test substance at all concentrations showed no pathological skin reactions and no other negative clinical symptoms of intoxication throughout the experiment. There was no significant difference in body weight increment of all groups in comparison to the vehicle control. The positive control substance DNCB elicted a reaction pattern with statistically significant increase in ear weight and stimulation index of cell proliferation 9.29, which was in congruence with his expected mode of action as a contact allergen.

The test substance showed a tendency to increased ear weight in the highest of concentrations tested. The result of skin irritation effect was considered as positive- it means the thest substance caused irritation of skin. Comparison of stimulation indexes between treated groups and control group revealed that the test substance caused significant increase in radioisotope incorporation into the DNA of dividing lymphocytes. This effect was dose dependent, with a significant ratio of 4.19 at 30%.

The test substance zinc nitrate hexahydrate had a positive result in LLNA test. Positive results in cell proliferation and no clinical symptoms of systemic toxicity revealed that the test substance zinc nitrate hexahydrate could be a contact allergen in mice but potential irriation effect does not rule out the possibility that it could be false positive result.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

While there is no particular study addressing respiratory sensitisation in experimental animals, there is no information suggesting zinc compounds to cause such effects animals.Taking into account the complete absence of skin sensitization potential of zinc compounds, respiratory sensitisation is not expected to be of concern for the zinc and zinc compounds.

Considering the absence of evidence of respiratory sensitization responses in humans, this endpoint is not expected to be of concern for zinc and zinc compounds.

Justification for classification or non-classification

The data on soluble zinc nitrate indicates a positive skin sensitisation potential in a study done with the Mouse local lymph node assay but no skin sensitisation potential was indicated in another study done with the Guinea pig maximization test. Since this latter test is known to be more trustful in studies with metals, no skin sensitization is expected and therefore classification for skin sensitization is not required according to EC criteria.