Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted on structural analogue and suitable for read across; in this study, background irritation present

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes

Type of study:

Buehler test

Justification for non-LLNA method:

During preparation of the original submission, reporting of an existing Buehler-type skin sensitisation test was considered more appropriate than sacrifice of further vertebrate animals in the newly adopted Local Lymph Node Assay.

Test material

Test material information

Constituent 1

Reference substance name:

Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts

EC Number:

283-392-8

EC Name:

Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts

Cas Number:

84605-29-8

IUPAC Name:

Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts

Details on test material:

Details on test material were described in the “JUSTIFICATIONS FOR READ-ACROSS”. It was present in section “ANY OTHER INFORMATION ON RESULTS INCL. TABLES”

In vivo test system

Test animals

Species:

guinea pig

Strain:

Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Sprague Dawley, Inc
- Age at study initiation: 6-11 weeks
- Weight at study initiation: 440-493 grams
- Housing: Housed individually in wire mesh suspension cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17.8-26.1
- Humidity (%): 30-70%
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12 hours

IN-LIFE DATES: From: To:

Study design: in vivo (non-LLNA)

Induction

Induction 1

Route:

epicutaneous, occlusive

Vehicle:

other: mineral oil

Induction 2

Concentration / amount:

Induction: 5% w/v
Challenge: 1% w/v

Challenge

Challenge 1

Route:

epicutaneous, occlusive

Vehicle:

other: mineral oil

Challenge 2

Concentration / amount:

Induction: 5% w/v
Challenge: 1% w/v

No. of animals per dose:

20 treated with test material, 10 naive control

Details on study design:

RANGE FINDING TESTS:
Priary Irritation after 6 hour patch aplication of test material in mineral oil at following concentrations:

Undiluted, 50, 25, 10, 5, 2.5, 1, 0.5 % w/v

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 3
- Exposure period: 6 hours
- Test groups:
- Control group:
- Site: Left shoulder
- Frequency of applications: 6 to 7 days
- Duration:
- Concentrations: 5%


B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 1 and 2 days (24 and 48 hours)
- Exposure period: 6 hours
- Test groups:
- Control group: 10 naive not previously exposed to test material
- Site:
- Concentrations: 1%
- Evaluation (hr after challenge): 24 and 48 hours


OTHER:

Challenge controls:

10 naive not previously exposed to test material

Positive control substance(s):

yes

Remarks:

1-Chloro-2,4,-Dinitrobenzene

Results and discussion

Positive control results:

Postive for skin sensitization

In vivo (non-LLNA)

Results

Results 1

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

1%

No. with + reactions:

3

Total no. in group:

20

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 1%. No with. + reactions: 3.0. Total no. in groups: 20.0.

Results 2

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

1%

No. with + reactions:

0

Total no. in group:

20

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 1%. No with. + reactions: 0.0. Total no. in groups: 20.0.

Results 3

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

1%

No. with + reactions:

1

Total no. in group:

10

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 1%. No with. + reactions: 1.0. Total no. in groups: 10.0.

Results 4

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

1%

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 1%. No with. + reactions: 0.0. Total no. in groups: 10.0.

Any other information on results incl. tables

JUSTIFICATIONS FOR READ-ACROSS

 

EC 270-608-0 has not been tested for skin sensitization effect, however experimental data on structurally related substances EC 283-392-8 are available and suitable for read-across. Justifications for read-across:

Chemical Similarity:

EC 283-392-8 and EC 270-608-0 consist of alkyl substituted phosphorodithioic acid structures complexed with zinc. These ZDDPs share similar core structures - alcohol ester of dithiophosphate, specific structural variations that relate to their alcohol group substituent are the alkyl chain length and the degree of branching of the alcohol charge (Table 1).

EC 283-392-8: phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-propyl) esters, zinc salts, referred to as “mixed isopropyl and 1,3-dimethylbutyl derivative”

EC 270-608-0: phosphorodithioic acid, mixed O,O-bis(iso-butyl and pentyl) esters, zinc salts – (CAS 68457-79-4), referred to as “mixed isobutyl and pentyl derivative”

Using Tanimoto Fingerprint (ToxMatch Version 1.06 software) to model chemical structures of the analogues showed comparable values for relevant molecular descriptors (e.g., number of H bond acceptor atoms), and gave a similarity index greater than 0.8 (values range from 0, no similarity to 1, identical; peer reviewed literature indicates that values greater than 0.6 are significantly similar); therefore chemical structures of the analogues have determined to be sufficiently close for there to be a reasonable expectation of similar toxicological effects.

Physicochemical Properties:

Standard physicochemical properties foe each substance were listed in Table 1. 

Table 1. Establishment of similarity between the data donating substance and the data accepting substance

EC	Alkyl Group	MW	Log Kow	Water Sol (ppm)	Vapor Pressure (Pa at 25 oC)
283-392-8 (Donate data)	C3/C6, branched	578	0.56	2736	6.9 x10^-3
270-608-0 (Accept data)	C4, branched C5, mixture of linear and branched	578	0.69	1625	2.5 x10^-3

These two substances have the same molecular weight, similar Log Kow, low vapor pressure, and they both are water soluble. The similarity of the physicochemical properties of these substances parallels their structural similarity. Also, non-random patterns were observed for the toxicological effects (e.g. available data showed low levels of acute toxicity effect, lacking of mutagenic effect in bacteria, consistent trend of change in ecotoxicity effect, etc.), these common behaviors and consistent trends suggest a common mechanism/mode of action, which provides supporting information for the read-across among these analogue members. The similarity of the physicochemical properties of these substances parallels their structural similarity.

Biologically Active Functional Groups:

The ester group presents in each of the analogue members, and is expected to exhibit similar biological activities. Non-random patterns were observed for the toxicological effects (e.g. available data showed low levels of acute toxicity effect, lacking of mutagenic effect in bacteria, consistent trend of change in ecotoxicity effect, etc), these common behaviors and consistent trends suggest a common mechanism/mode of action, with little influence from the length of carbon chain. These facts further supported read-across between the analogue members.

Available Data and Adequacy for Read-across:

EC 283-392-8 was evaluated for skin sensitizing effected using Buehler technique, and negative result was obtained.

By read across to its analogous substance, EC 270-608-0 was predicted to be non-sensitizing. This assessment was further supported by QSAR analysis of EC 270-608-0 which did not show structural alerts for sensitization (OECD toolbox 1.1.01). 

Conclusion:

Based on the abovementioned justifications, results from EC 283-392-8 were weighted and used to fill this data gap for EC 270-608-0. EC 270-608-0 was predicted to be non-sensitizing. Use of read-across will eliminate the need for new animal testing while allow meeting the data requirements.

Applicant's summary and conclusion

Interpretation of results:

not sensitising

Remarks:

Migrated information

Conclusions:

EC 283-392-8 was test for skin sensitizing potential. The irritation in 3/20 animals in the challenge phase scored after 24 hours did not persist to 48 hours, indicating an irritation response rather than a skin sensitization response.
Results from EC 283-392-8 were used to fill this data gap for EC 270-608-0. EC 270-608-0 was predicted to be non-sensitizing