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Genetic toxicity: in vitro

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in vitro gene mutation study in bacteria
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study was conducted on structural analogue and suitable for read across. Guideline GLP study.

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
equivalent or similar to
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
GLP compliance:
Type of assay:
bacterial reverse mutation assay

Test material



Target gene:
Histidine operon (hisG46, hisC3076, hisD3052); Lipopolysaccharide barrier (LPA); DNA excision repar (uvrB)
Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Metabolic activation system:
mammalian microsomal enzymes
Test concentrations with justification for top dose:
with s9 mix; 25, 50, 100, 250, 1000, and 5000 ug/plate
without s9 mix: 1, 5, 10, 25, 100, 500 ug/plate
Confirmatory assay:
with s9 mix; 50, 100, 250, 500, 1000, and 5000 ug/plate
without s9 mix: 5, 10, 25, 50, 100, 500 ug/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: ethanol
- Justification for choice of solvent/vehicle:
Negative solvent / vehicle controls:
Positive controls:
Positive control substance:
other: multiple postive controls (depedning on strain and metabolic activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

- Preincubation period:
- Exposure duration: 48 hours
- Expression time (cells in growth medium):
- Selection time (if incubation with a selection agent):
- Fixation time (start of exposure up to fixation or harvest of cells):

SELECTION AGENT (mutation assays):
SPINDLE INHIBITOR (cytogenetic assays):
STAIN (for cytogenetic assays):



- Method: growth inhibition

- Determination of polyploidy:
- Determination of endoreplication:
- Other:

Evaluation criteria:
TA98, TA100, WP2uvrA: A postive result must produce at least a 2-fold increase the mean revertants per plate of at least one tester strain over the mean revertants per plate fo the control. A dose response in the mean number of revertants per plate must also occur.
TA1535 and TA1537: A postive result must produce at least a 3-fold increase the mean revertants per plate of at least one tester strain over the mean revertants per plate fo the control. A dose response in the mean number of revertants per plate must also occur.

Results and discussion

Test results
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Cytotoxicity / choice of top concentrations:
Vehicle controls validity:
Untreated negative controls validity:
not examined
Positive controls validity:
Remarks on result:
other: all strains/cell types tested
Migrated from field 'Test system'.

Any other information on results incl. tables

Read-Across Justification for EC 249-109-7

EC 249-109-7 has not been tested for genetic toxicity in bacteria, however experimental data from a study with the structurally related substance EC 224-235-5 was 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,; 2. ECHA Practical Guide 6: How to Report Read-Across and Categories,; 3. OECD 2007. Guidance on grouping of chemicals. ENV/JM/MONO(2007)28).

The registered substance ZDDP EC 249-109-7, zinc bis(O,O-diisooctyl) bis(dithiophosphate), 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 224-235-5, zinc bis[O,Obis(2-ethylhexyl)] bis(dithiophosphate), 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 249-109-7 substance and EC 224-235-5 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 249-109-7 substance and EC 224-235-5 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 249-109-7 substance and EC 224-235-5 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 249-109-7 substance and EC 224-235-5 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

Interpretation of results (migrated information):
negative with metabolic activation
negative without metabolic activation