Phosphorodithioic acid, mixed O,O-bis(2-ethylhexyl and iso-Bu) esters, zinc salts

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study was conducted on structural analog and suitable for read across.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

GLP compliance:

yes

Type of assay:

micronucleus 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

Test animals

Species:

mouse

Strain:

CD-1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
- Age at study initiation: 8 weeks and 2 days
- Weight at study initiation: 28.9-36.4 g (male) and 23.1-29.0 g (female)
- Assigned to test groups randomly: yes
- Fasting period before study:
- Housing: five per cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 55 +/- 15
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12 hours


IN-LIFE DATES: From: To:

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

- Vehicle(s)/solvent(s) used: Peanut oil
- Justification for choice of solvent/vehicle:
- Concentration of test material in vehicle: 10 mL/kg
- Amount of vehicle (if gavage or dermal): 10 mL
- Type and concentration of dispersant aid (if powder):
- Lot/batch no. (if required):
- Purity:

Duration of treatment / exposure:

24, 48, and 72 hours

Frequency of treatment:

Once

Post exposure period:

24, 48, and 72 hours

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
7.13 mg/kg
Basis:

Doses / concentrations 2

Remarks:

Doses / Concentrations:
14.3 mg/kg
Basis:

Doses / concentrations 3

Remarks:

Doses / Concentrations:
28.5 mg/kg
Basis:

No. of animals per sex per dose:

5 males and 5 females per dose

Control animals:

yes, concurrent vehicle

Positive control(s):

cyclophosphamide
- Route of administration: sterile water
- Doses / concentrations: 60 mg/kg

Examinations

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
Range finding study performed to find the maximum tolerated dose

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):


DETAILS OF SLIDE PREPARATION:
Slides fixed with methanol and stained in May-Grunwald solution followed by Giemsa.

METHOD OF ANALYSIS:
Scored for micronuclei and the polychromatic erythrocyte (PCE) to normochromatic erythrocyte (NCE) cell ration.

OTHER:

Evaluation criteria:

Statistically sifnificant dose-related increase in micronucleated PCE's and the detection of a statictically sifnificant postive response for at least one dose level.

Statistics:

The frequency of micronucleated polychromatic erythrocytes between treated groups and vehicle controls were compared. Tests included Cochran-Armitage test for trend, a one-way analysis of variance and Dunnett’s procedure.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Read-Across Justification for EC 270-478-5

EC 270-478-5 has not been tested for genetic toxicity, however experimental data from OECD 471, OECD, 474, and OECD 476 studies with the structurally related substance EC 283-382-8 were available and suitable for read-across.

Consistent with ECHA and OECD Guidance, read-across can be performed to fill data gaps for a substance when one or more analogues have similarity from multiple lines of evidence including structural, physical-chemical, mechanistic, toxicological and/or ecotoxicological bases (REFERENCES: 1. ECHA Chapter R.7a: Endpoint specific guidance. Guidance on Information Requirements and Chemical Safety Assessment, http://wko.at/up/enet/chemie/TL_ChapterR7a.pdf; 2. ECHA Practical Guide 6: How to Report Read-Across and Categories, http://echa.europa.eu/doc/publications/practical_guides/pg_report_readacross_categ.pdf; 3. OECD 2007. Guidance on grouping of chemicals. ENV/JM/MONO(2007)28).

The registered substance ZDDP EC 270-478-5, phosphorodithioic acid, mixed O,O-bis(2-ethylhexyl and iso-Bu) esters, zinc salts, is a member of the group of inter-related ZDDP substances of similar structure and chemical properties that have previously been assessed as a category under the HPV program. For the purposes of read-across to fill data gaps for this substance the analogue ZDDP EC 283-382-8, phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts, is justified for use based on its similar structure, physical chemical properties, and fate and effects profile. For some endpoints where multiple reliable analogs exist, “worst case” data is selected based on the most precautionary test result, or based on reading across from lower molecular weight to higher or from higher water solubility to lower.

The following discussion provides multiple lines of evidence justifying this read across approach:

I. Category: EC 270-478-5 substance and EC 283-382-8 analog have been demonstrated to show sufficient structural and physicochemical similarity to be included in the High Production Volume (HPV) Chemical Challenge Program under the Zinc Dialkyldithiophosphate (ZDDP) category.

II. Manufacture/Usage:  EC 270-478-5 substance and EC 283-382-8 analog are substances that are generically referred to as zinc dialkylthiophosphate (ZDDP) that are produced under similar manufacturing procedures and are intended for multifunctional use as oil additives for antioxidancy and antiwear.

III. Chemical Similarity:EC 270-478-5 substance and EC 283-382-8 analog have the general empirical formula of C#H#O4P2S4Zn and are coordination complexes of zinc metal bonded to alkyldithiophosphate ligands. ZDDP complexes exist in reversible monomeric or dimeric forms (equilibrium dependent on temperature) and a basic form. The stereochemistry of the basic form can be described as four Zn atoms arranged around a tetrahedral oxide with six alkyldithiophosphate ligands. As a group, these ZDDPs share similar alcohol ester of dithiophosphate core structures, and variations that relate to alkyl chain length and the degree of branching of the alcohol. Using Tanimoto Fingerprint (ToxMatch Version 1.06 software) to model the chemical structures of the substances and its analog 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 and read-across is supported.

IV. Physicochemical Properties:EC 270-478-5 substance and EC 283-382-8 analog have similar values for average molecular weight (based on the monomer structure), log Kow, water solubility, and vapor pressure; or in some instances for read-across purposes “worst case” values are selected by going from a lower to a higher molecular weight, or from a higher to a lower water solubility.

V. Biologically Active Functional Groups: The ester group is a common functional group present in each of the analogue members, and is expected to exhibit similar biological activities with little influence from the length of carbon chain. Any potential breakdown products, via physical or biological processes, are also expected to result in structurally similar chemicals. In addition, non-random patterns have been observed for the toxicological effects (e.g., available data showed low levels of acute toxicity, lack of mutagenic potential, and a trend of change in ecotoxicity potential based on molecular weight). These common behaviors and consistent trends suggest a common mechanism and mode of action thereby providing further supporting evidence for the read-across among the ZDDP members.

 

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative