Reaction product of 2,4-bis(2-methylbutan-2-yl)phenol and phosphorous pentoxide

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24th January 2017- 23rd February 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

OECD 406

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes

Type of study:

Buehler test

Justification for non-LLNA method:

A Buehler test was used for R&D purposes and worldwide acceptance, so an LLNA should not ethically be completed based on animal welfare reasons. LLNA frequently gives false positives for irritating substances therefore Buehler test was used. The testing will also be submitted to other regulatory agencies that do not accept LLNA testing.

Test material

Test material information

impurity 1

Reference substance name:

2,4-di-tert-pentylphenol

EC Number:

204-439-0

EC Name:

2,4-di-tert-pentylphenol

Cas Number:

120-95-6

Molecular formula:

C16H26O

IUPAC Name:

2,4-bis(1,1-dimethylpropyl)phenol

Specific details on test material used for the study:

The test material is a UVCB

In vivo test system

Test animals

Species:

guinea pig

Strain:

Hartley

Sex:

male

Details on test animals and environmental conditions:

All animals were acclimated for at least five days. Animals were individually housed in wire mesh suspension cages. Cage cards incorporating study number and animal group code were used to identify each guinea pig. Animals were evaluated during the pre study acclimation period for signs of disease or physical abnormalities and only animals that appeared healthy were used on the study. Only animals with skin sites that were free from defects or alterations in coloration or texture were used. The animals to be tested were selected from the population of animals available for this study. The animals were randomly caged according to Standard Operating Procedures.
The animals were maintained on a 12-hour cycle light controlled room, at a temperature of 64° - 79°F and a relative humidity of 30-70%. The animals were maintained according to the recommendations contained in the National Academy Press 2011: “Guide for the Care and Use of Laboratory Animals.” The animals were supplied Purina Guinea Pig Chow and tap water ad libitum during both acclimation and test periods. There was daily access to feed analysis and water analysis was documented. There were no contaminants in either the feed or the water that would be expected to affect the outcome of this study.

Study design: in vivo (non-LLNA)

Induction

Route:

epicutaneous, semiocclusive

Vehicle:

other:

Remarks:

Mineral oil

Concentration / amount:

0.4ml of 75% concentration of test substance

Day(s)/duration:

6 hours

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Challenge

No.:

#1

Route:

epicutaneous, semiocclusive

Vehicle:

other: Mineral oil

Concentration / amount:

0.4ml of 25% concentration of test sample.

Day(s)/duration:

6hrs

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

20 animals were used both induction and challenge test

Details on study design:

A pilot study was conducted using 2 animals to determine the concentration that produced mild dermal irritation at the application site which is then used for the inductions dose and the highest non irritating concentration of the test substance is then used as the challenge dose. The application site is prepared by removing hair from the back and sides of the trunk and four sites are selected for the irritation screening, 0.4ml of 25%, 50%, 75% and 100% of the test substance were applied to the test site and secured with micropore tape and further secured with kendal adhesive tape then left for 6 hrs after which the tape is removed and the irritation scores are taken a day after.

Similarly, application sites were prepared on test animals by shaving off hair and test substance is applied and secured with tape for 6hours after which tape is taken off and excess material wiped off. The test substance was administered to 20 young adults’ male Guinea pigs by dermal application at a dose volume of 0.4ml per application site for the Inductions and challenge. The does was based upon the appropriate amount of material sufficient to saturate the cotton pad in the Hilltop Chamber and allow for good skin contact of the test substance. Animals are scored for Irritation (erythema) at 24 and 48hours after completion of exposure. All animal body weight are taken before and after the study. In the challenge study, 6 negative control animals were challenged with the test substance alongside 10 test animals.

All induction scores are recorded final challenge scores are reported after 24 and 48hrs.

Challenge controls:

6 Animals were used for the control groups and 4 were kept in case a rechallenge was required.

Positive control substance(s):

yes

Results and discussion

In vivo (non-LLNA)

Results

Results 1

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

Animals were dosed at 25% concentration for the challenge phase

No. with + reactions:

20

Total no. in group:

20

Remarks on result:

positive indication of skin sensitisation

Results 2

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

Animals were dosed at 25% concentration

No. with + reactions:

19

Total no. in group:

20

Remarks on result:

positive indication of skin sensitisation

Results 3

Key result

Reading:

1st reading

Hours after challenge:

6

Group:

negative control

Dose level:

Animals were dosed at 25% concentration

No. with + reactions:

1

Total no. in group:

6

Remarks on result:

no indication of skin sensitisation

Results 4

Group:

positive control

Remarks on result:

not measured/tested

Applicant's summary and conclusion

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

Following primary challenge of test substance, at 25% concentration, the incidence of grade 1 response or greater in the test group (20 of 20) was compared to that of the naive control group (1 of 6). The incidence and severity of these responses were significantly greater than those produced by the naive control group indicating that sensitization had been induced.

Executive summary:

The test substance was tested for dermal sensitization potential utilizing a Buehler Technique Guinea Pig Sensitization Protocol. The test substance was evaluated for sensitization potential by applying 0.4 ml at a 75% concentration directly into Hilltop Chambers® and applying them to the clipped left shoulder of twenty albino guinea pigs in the following manner: The animals were held gently, and the chambers were applied as quickly as possible to the clipped left shoulder. The chambers were secured with Micropore tape and further secured with Kendall adhesive tape. Approximately six hours later, the tape and chambers were removed. Two additional induction doses were conducted following the same procedure, at weekly intervals. Two weeks after the final application the animals received a topical primary challenge dose (6 hour contact), at 25% concentration, on a naive site located on the right shoulder. Animals were scored for irritation at 24 and 48 hours after initiation of the primary challenge application. Ten guinea pigs served as a naive control group, and remained untreated through the induction phase. Six naive control animals received only the primary challenge dose, at a 25% concentration. The four remaining guinea pigs were designated for a re-challenge, if necessary. Following primary challenge at 25% concentration, the incidence of grade 1 response or greater in the test group (20 of 20) was compared to that of the naive control group (1 of 6). The incidence and severity of these responses were significantly greater than those produced by the naive control group indicating that sensitization had been induced.