Zinc dilactate

Endpoint summary

Description of key information

The assessment of the potential of zinc lactate for sensitisation is based on read-across from lactic acid and zinc sulfate. Neither source substance is sensitising. Since within the time frame associated with induction of sensitisation it can be assumed that zinc lactate will be fully dissociated and exposure to zinc lactate will in fact be exposure to zinc(II) cations and lactate anions, information on zinc salts and lactic acid is fully relevant for zinc lactate.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Study period:

Not applicable

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The basic principle underlying the LLNA method used is to induce a primary proliferation of lymphocytes in the lymph node draining the site of test material application. An ear abrasion technique is employed which enhances penetration of the metal ion by removing the horny layer of the epidermis. It enables the detection of ear-swelling responses of weak contact allergens by increasing their LNC proliferation. This proliferation is proportional to the dose applied (and to the potency of the allergen) and provides a simple means of obtaining an objective and quantitative measurement of sensitisation. The LLNA assesses this proliferation, wherein the proliferation in test groups is compared to that in vehicle treated controls. The ratio of the proliferation in treated groups to that in vehicle controls (Stimulation Index), is determined, and must be at least three. The methods described here are based on the use of radioactive labelling to measure the proliferation of the lymph node cells.

GLP compliance:

not specified

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
- Age at study initiation: 6-8 wk

Vehicle:

other: 20 % ethanol

Concentration:

10 % test material in 20 % ethanol solution

No. of animals per dose:

Three

Details on study design:

MAIN STUDY:
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Local Lymph Node Assay
- Criteria used to consider a positive response: Stimulation index ≥ 3

TREATMENT PREPARATION AND ADMINISTRATION:
25 µL of test material was applied to the dorsum of both ears for three consecutive days. Prior to the test material treatment, the ears of each mouse were gently abraded using a 19 g needle. Four days following the initial application, draining lymph nodes were excised.

PREPARATION OF CELL SUSPENSION:
A single cell suspension of LNC was prepared by mechanical disaggregation through sterile 200 mesh steel gauge. The cells were washed twice with an excess phosphate-buffered saline (PBS) and resuspended in RPMI-1640 culture medium supplemented with 10 % fetal calf serum (FCS), 25 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (Hepes), 100 µg/mL penicillin and 100 U/mL streptomycin. The cell concentration was adjusted to give 5 x 10E6 cells/mL.
Lymphocyte suspensions were seeded into 96 well microtiter plates at a concentration of 1 x 10E6 cells/well (5 wells per animal), and cultured with 0.5 µCi [3H] methyl thymidine ([3H]TdR) for 18 h at 37 °C in a humidified atmosphere of 5 % CO2 in air.
The incorporation of [3H]TdR was measured using a liquid scintillation counter and expressed as mean counts per min (cpm) ± standard deviation per node of three animals for each test group.

Other: Compound solubility - Completely dissolved in 20 % ethanol solution

Positive control substance(s):

not specified

Statistics:

Not reported

Parameter:

SI

Remarks on result:

other: 10 % zinc sulfate = 1.41

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: Mean value cpm ± SD ( x 10-3) = 2.14 ± 0.77

Validity of ear abrasion technique: It does not affect the LNC response in the vehicle treated group.

Interpretation of results:

not sensitising

Conclusions:

Under the conditions of the test, the test material was determined to be non-sensitising to mice.

Executive summary:

A study was conducted to evaluate the skin sensitisation potential of the test material in mouse using a modified Local Lymph Node Assay. No guideline or GLP compliance was documented in the study report.

Groups of BALB/c mice (n = 3) were treated with 10 % concentration of test material or vehicle (20 % ethanol solution) by applying 25 µL to the dorsum of both abraded ears for three consecutive days. Four days following the initial application, draining lymph nodes were excised. A single cell suspension of LNC was prepared and the incorporation of [3H]TdR was measured using a liquid scintillation counter.

[3H]TdR incorporation (expressed as mean counts per min (cpm) ± standard deviation per node x 10^-3) was 2.14 ± 0.77 and the ratio of the proliferation in treated group to that in vehicle control (stimulation index) was 1.41.

Hence, under the conditions of the test, the test material was determined to be non-sensitising to mice.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1986-07-01 to 1986-09-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 81-6 (Skin Sensitisation)

Principles of method if other than guideline:

The test guideline describes a modification of the Buehler closed patch technique.

GLP compliance:

yes

Type of study:

Buehler test

Justification for non-LLNA method:

The Buehler test is an accepted method for hazard identification of skin sensitising substances as recommended in "ECHA guidance R.7a: Endpoint specific guidance".

Species:

guinea pig

Strain:

Hartley

Sex:

female

Details on test animals and environmental conditions:

Young adult, female, outbred, Hartley guinea pigs were obtained from Charles River Breeding Laboratories, Inc. Portage, MI facility). Animals were housed individually in galvanized steel, wire-bottomed cages that conformed to the size standards specified in DHEW Publication (NIH) 78.23. The cages on each rack were numbered in a standard manner and a list of random numbers was generated by computer program for the number of cage positions used on each rack. After receipt, each animal was removed from the shipping container, housed in the appropriate randomly selected cage, and assigned a sequential animal number unique within ABC. The sequential animal number was listed on a cage card affixed to the front of each animal1s cage.
The animals were quarantined for at least 7 days after receipt and observed daily during the quarantine period for mortality, morbidity, and abnormal signs. Animals were examined during quarantine and only those considered to be in good health were used in this study. The quarantine and study room was cleaned daily and the cages were cleaned and sanitized as specified in ABC Standard Operating Procedures. Urine and feces feil through the wire mesh floor onto animal caging board. The cage boards were changed daily during the quarantine and study periods.
The animal room was well ventilated and air-conditioned. The temperature and humidity were monitored daily in this room during the quarantine and study periods; there were no deviations
from temperature and humidity ranges of 73 +5°F and 30-70%, respectively, which were considered to have had an adverse effect on the study. The animal room was lighted from approximately 6:00 a.m. to 6:00 p.m. (12-hour light/dark cycle) using automatic timers. The test article applications were completed between 9:59 a.m. and 10:29 a.m. during all 3 phases of the study (range-finding, nduction, and challenge).
Purina Guinea Pig Chow 5025 was fed ad libitum to all animals. Filtered tap water was provided ad libitum through an automatic watering system.

Route:

epicutaneous, occlusive

Vehicle:

water

Concentration / amount:

3, 10, 30, or 100% test article

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100%

No. of animals per dose:

10

Details on study design:

The duration of testing was 2 days for range-finding and 35 days for the main study. Two (2) female guinea pigs were used in preliminary range-finding trials. Ten (10) female guinea pigs were used in each main study group (test and naive control).
Animals were assigned to the study by sequential animal number (see IV.A. for randomization procedures). However, any animal deemed unsuitable was not used, and the next acceptable sequentially numbered animal was used. The hair on the back or left flank, (induction) and/or flank (range-finding and challenge) of each animal was closely clipped with Oster electric clippers equipped with a number 40 (surgical) blade prior to dermal application. The hair was reclipped as necessary for subsequent induction applications and for dermal evaluations.
A 0.5 milliliter sample of the test article (100%) and 0.5 milliliter samples of 30, 10, or 31 suspensions of the test article in deionized water were placed on separate 4x4 centimeter Webril patches, attached to Blenderm tape, and each of these concentrations was applied to a prepared site on a range-finding animal (2 concentrations were evaluated per animal). The 100% test article concentration was selected for induction and challenge applications since dermal reactions were minimally irritating at this range-finding test site. After two induction applications the concentration was reduced to 30% and the test site was changed to the left flank. During the induction phase, 10 guinea pigs assigned to the test group received two 0.5 milliliter applications of the test article (100%) and seven 0.5 milliliter applications of the test article (30%) on 4x4 centimeter Webril patches attached to Blenderm tape. The 10 guinea pigs assigned to the naive control group remained untreated during the test group induction phase.
The induction applications were made 3 times each week (Monday, Wednesday, and Friday) until all 9 induction applications had been applied. Two weeks after the ninth induction application, each animal of both the test group and the naive control group received a single 0.5 milliliter challenge application of the test article (100%) on the right flank. Webril patches (4x4 centimeter) attached to Blenderm tape were also used at the challenge.
During the range-finding, induction, and challenge phases, the Webril patches containing the test article were applied to the prepared sites and the entire trunk of each animal was wrapped with an impervious binder consisting of plastic wrap, adhesive tape, and masking tape. After a 6 hour (+_ 30 minutes) exposure period, the binders and patches were removed. The sites on each animal were evaluated for erythema, edema, and other lesions 24 and 48 hours (+ 2 hours at each interval) after the test article applications (range-finding, each induction, and the challenge). Dermal reaction scores were assigned using the grading system presented in Table l of this report. Other dermal reactions observed were also recorded. Individual body weight values were determined for range- finding animals prior to application and prior to sacrifice. Individual body weight values were determined for test animals and naive control animals on the day of the initial induction application (day 0) and on the day of the 48-hour challenge evaluations (day 35). All animals were observed for abnormal clinical signs and mortality at least once daily during testing. All range-finding and main study animals were euthanized by asphyxiation with carbon dioxide and discarded at termination of testing.

Positive control substance(s):

yes

Remarks:

dinitrochlorobenzene (historical data)

Positive control results:

Erythema and edema according to Draize (1979) and for other dermal reactions at 24 and 48 hours following each induction and challenge application. Results are presented for testing on 3 groups of 10 guinea pigs. In the first 24 hrs of the challenge test, 8, 8 and 10 out of 10 animals showed positive sensitization reaction to the positive control (DNCB), and 48 hours after the beginning of the test, 8, 8 and 9 out of 10 animals still presented positive reaction to DNCB.

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

Only one challenge dose

No. with + reactions:

9

Total no. in group:

10

Clinical observations:

All effects observed were deemed irritation, not sensitization

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

One dose level only

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

All effects observed were deemed irritation, not sensitization

Interpretation of results:

not sensitising

Conclusions:

In a dermal sentitisation test (modification of the Buehler closed patch technique), lactic acid was tested negative for skin sensitisation.

Executive summary:

This study was conducted to evaluate the contact dermal sensitization potential of the test article, SY-83, using a method described in the EPA guidelines, 1982 (modification of the Buehler Closed Patch Technique) as described in American Biogenics Corporation (ABC) protocol A330. No mortalities occurred and all animals gained body weight. The test article (100 %) produced very slight erythema at 3 sites and very slight edema at l site after the 1st induction. Erythema grades increased in severity after the 2nd induction application. One site was graded as severe erythema, however, this grade was given a 4 due to pinpoint pitting of the skin and scab formation, not for redness. Due to the increase of severity of the reactions, the concentration of the test article was reduced to 30 % and the induction site was changed to the left flank. Very slight erythema was noted after the 5th induction application. Grades ranging from very slight to severe erythema were noted from the 7th to the 9th induction applications. Again, the severe (grade 4) reactions were given this grade due to pinpoint pitting of the skin and the eschar formation, not for redness.

After the challenge application, the test article (100 %) produced grade 4 erythema in up to 6 test animals. These gradings were very sirnilar in character as those seen during the induction pplications, that is, pinpoint pitting of the skin and eschar formation, very little redness. These reactions were considered to be irritation reactions, not sensitization reactions. Other reactions noted at challenge for the test animals were very slight to moderate erythema, and very slight to moderate edema. The test article (100 %) produced grade 4 erythema in up to 8 naive control animals. These gradings were also pinpoint pitting of skin and eschar formation with very little redness. These reactions were considered to be irritation reactions, not sensitization reactions. Other reactions noted for the naive control animals were very slight to moderate erythema and very slight to moderate edema. The reactions seen in the naive control animals at the challenge application were similar to the reactions seen for the test group animals and the test article, SY-83, was not considered to be a contact dermal sensitizer.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the negative results of the read-across partners lactic acid and zinc sulphate, no classification for sensitisation of zinc lactate is warranted.