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Genetic toxicity in vitro

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Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not specified
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Data taken from HPV Challenge Program website from which data have been entered into the HPVIS. Original posting date for substituted diphenylamine documents: December 20, 2001 Posting date for revised documents for substituted diphenylamines: October 24, 2003.
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay
Target gene:
Bacterial reverse mutation assay
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Details on mammalian cell type (if applicable):
No data
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
10% liver S9
Test concentrations with justification for top dose:
50, 150, 500, 1500, 5000 ug/plate
Vehicle / solvent:
Acetone
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
yes
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
9-aminoacridine
N-ethyl-N-nitro-N-nitrosoguanidine
other: 2-Aminoantracene (2AA); ENNG
Details on test system and experimental conditions:
System of testing: Salmonella typhymurium, strains TA-1535, TA-1537, TA-98, TA-100 and Escherichia coli strain WP2uvrA-
Metabolic activation: with and without

The positive controls were as follows:

Non-activation
TA100: N-ethy-N'-nitrosoquanidine (ENNG), 3 µg/plate
TA1535: ENNG, 5 µg/plate
TA1537: 9-aminoacridine, 5 µg/plate
TA98: 4-nitroquinoline-1-oxide, 0.2 µg/plate
WP2uvrA-: ENNG, 2 µg/plate

Activation (10% liver S9)
TA100: 2-Aminoantracene (2AA), 1 µg/plate
TA1535: 2AA, 2 µg/plate
TA1537: 2AA, 2 µg/plate
TA98: 2AA, 0.5 µg/plate
WP2uvrA-: 2AA, 10 µg/plate

The S. typhymurium strains were obtained from the University of California (Berkeley), and the E. coli strain was obtained from the British Industrial Biological Research Association. Overnight subcultures of the stock cultures were prepared in nutrient broth and incubated at 37°C for approximately 10 hours. The test material was dissolved in acetone to prepare the test concentrations noted above. Vehicle and positive controls were run in parallel with the test material.
Evaluation criteria:
A substance was considered positive if it induce a dose-related and statistically significant increase in mutation rate (at least twice the spontaneous reversion rate) in one or more strains with or without activation. (Note: In the event of two equivocal experiments a third experiment may be used.) To be considered negative the number of induced revetants compared to the spontaneous revertants should be less than two fold at each dose level employed, the intervals of which should be between two and five fold and extend to the limits imposed by toxicity, solubility or up to the maximum recommended dose of 5000 ug/plate. (Note: In this case the limiting factor was the maximum recommended dose.)
Statistics:
Not specified.
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not specified
Positive controls validity:
valid
Additional information on results:
No toxicity was observed to any of the strains. Precipitates were observed at 1500 ug/plate and 5000 ug/plate but did not interfere with scoring. No significant increase in the frequency of revetant colonies was recorded in any strain with or without activation, and the responses of the positive controls were satifactory.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
negative with and without metabolic activation

Cytotoxicity conc: With metabolic activation: None toxic
Without metabolic activation: None toxic
Executive summary:

Original posting date for substituted diphenylamine documents: January 15, 2002
Posting date for revised documents for substituted diphenylamines: October 24, 2003 and January 19, 2007.

No toxicity was observed to any of the strains. Precipitates were observed at 1500 ug/plate and 5000 ug/plate but did not interfere with scoring. No significant increase in the frequency of revetant colonies was recorded in any strain with or without activation, and the responses of the positive controls were satifactory.  

Endpoint:
in vitro cytogenicity / chromosome aberration study in mammalian cells
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24 September 2012 to 18 December 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
Deviations:
yes
Remarks:
Detailed under Any other information
Qualifier:
according to
Guideline:
EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)
Deviations:
yes
Remarks:
Detailed under Any other information
GLP compliance:
yes
Type of assay:
in vitro mammalian chromosome aberration test
Target gene:
chromosome aberrations in cultured peripheral human lymphocytes
Species / strain / cell type:
lymphocytes: cultured peripheral human lymphocytes
Details on mammalian cell type (if applicable):
Cultured peripheral human lymphocytes were used as test system. Peripheral human lymphocytes are recommended in international guidelines (OECD, EC).

Blood was collected from healthy adult, non-smoking, male volunteers.
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
phenobarbital and ß-naphthoflavone induced rat liver S9-mix
Test concentrations with justification for top dose:
Without S9-mix :10, 30 and 200 µg/ml culture medium
(24 h exposure time, 24 h fixation time).
10, 30 and 100 µg/ml culture medium
(48 h exposure time, 48 h fixation time).
With S9-mix : 10, 30 and 50 µg/ml culture medium
(3 h exposure time, 48 h fixation time).
Vehicle / solvent:
Dimethyl sulfoxide
Solvent for positive controls: Hanks’ Balanced Salt Solution (HBSS)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
dimethyl sulfoxide
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
mitomycin C
Details on test system and experimental conditions:
The objective of this study was to evaluate Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene for its ability to induce structural chromosome aberrations in cultured human lymphocytes (1), either in the presence or absence of a metabolic activation system (S9-mix).

Background of the test system: Whole blood samples obtained from healthy male subjects were treated with an anti-coagulant (heparin) and cultured in the presence of a mitogen (phytohaemagglutinin). These stimulated human lymphocytes were used because they are sensitive indicators of clastogenic activity of a broad range of chemicals (1-5).
The stimulated lymphocytes were exposed to the test substance both in the absence and presence of a metabolic activation system (S9-mix). In combination with this metabolic activation system indirect chemical mutagens, i.e. those requiring metabolic transformation into reactive intermediates, can be tested for possible clastogenic effects in vitro.
At predetermined intervals after exposure of the stimulated human lymphocytes to the test substance, cell division was arrested in the metaphase stage of the cell cycle by addition of the metaphase-arresting chemical colchicine. Cells were harvested, stained and metaphase cells were analysed for the presence of structural chromosome aberrations such as breaks, gaps, minutes, dicentrics and exchange figures. Results from cultures treated with the test substance were compared with control (vehicle) treated cultures.
Chromosome aberrations were generally evaluated in the first post-exposure mitosis (i.e. 24 hours after exposure). However, since the appearance of the first post-exposure mitosis could be considerably delayed due to toxic insult to the cells, cells were also harvested 48 hours after exposure to cover the interval in which maximum aberration frequency was expected.
A test substance that induces a positive response in this assay is presumed to be a potential mammalian cell clastogenic agent

Test substance preparation: No correction was made for the purity/composition of the test compound.
Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene was dissolved in dimethyl sulfoxide of spectroscopic quality (SeccoSolv, Merck, Darmstadt, Germany).
Test substance concentrations were used within 3 hours after preparation.
The final concentration of the solvent in the culture medium was 1.0% (v/v).

Reference substances
Negative control: The vehicle for the test substance was dimethyl sulfoxide.

Positive controls
Without metabolic activation (-S9-mix): Mitomycin C (MMC-C; CAS no. 50-07-7, Sigma, Zwijndrecht, The Netherlands) was used as a direct acting mutagen at a final concentration of 0.5 and 0.75 µg/ml for a 3 h exposure period, 0.2 and 0.3 µg/ml for a 24 h exposure period and 0.1 and 0.15 µg/ml for a 48 h exposure period (protocol deviation 1).

With metabolic activation (+S9-mix): Cyclophosphamide (CP; CAS no. 50-18-0. Baxter B.V., Utrecht, The Netherlands) was used as an indirect acting mutagen, requiring metabolic activation, at a final concentration of 10 µg/ml for a 3 h exposure period (24 h fixation time).

Solvent for positive controls: Hanks’ Balanced Salt Solution (HBSS) (Invitrogen Corporation, Breda, The Netherlands), without calcium and magnesium.

All reference stock solutions were stored in aliquots at ≤-15°C in the dark. These solutions were thawed immediately before use.

Test system: Cultured peripheral human lymphocytes were used as test system. Peripheral human lymphocytes are recommended in international guidelines (OECD, EC).

Blood was collected from healthy adult, non-smoking, male volunteers. The Average Generation Time (AGT) of the cells and the age of the donor at the time the AGT was determined (December 2011) are presented below:

Dose range finding study: age 41, AGT = 13.9 h (24 h exposure period)
age 35, AGT = 13.9 h (48 h exposure period)
First cytogenetic assay: age 35, AGT = 13.9 h
Second cytogenetic assay: age 33, AGT = 15.8 h (24 and 48 h exposure period)
age 29, AGT = 15.3 h (3 h exposure period)

Cell culture
Blood samples: Blood samples were collected by venapuncture using the Venoject multiple sample blood collecting system with a suitable size sterile vessel containing sodium heparin (Vacuette, Greiner Bio-One, Alphen aan den Rijn, The Netherlands). Immediately after blood collection lymphocyte cultures were started.

Culture medium: Culture medium consisted of RPMI 1640 medium (Invitrogen Corporation), supplemented with 20% (v/v) heat-inactivated (56°C; 30 min) foetal calf serum (Invitrogen Corporation), L-glutamine (2 mM) (Invitrogen Corporation), penicillin/streptomycin (50 U/ml and 50 µg/ml respectively) (Invitrogen Corporation) and 30 U/ml heparin (Sigma, Zwijndrecht, The Netherlands).

Lymphocyte cultures: Whole blood (0.4 ml) treated with heparin was added to 5 ml or 4.8 ml culture medium (in the absence and presence of S9-mix, respectively). Per culture 0.1 ml (9 mg/ml) phytohaemagglutinin (Remel, Europe Ltd., United Kingdom) was added.

Environmental conditions: All incubations were carried out in a controlled environment in the dark, in which optimal conditions were a humid atmosphere of 80 - 100% (actual range 58 - 95%), containing 5.0 ± 0.5% CO2 in air, at a temperature of 37.0 ± 1.0°C (actual range 35.0 - 37.5°C). Temperature and humidity were continuously monitored throughout the experiment. The CO2 percentage was monitored once on each working day. Temporary deviations from the temperature (in the range of 35.0 - 36.0°C), humidity (with a maximum of 20%) and CO2 percentage (with a maximum of 1%) occurred that were caused by opening and closing of the incubator door, but the time of these deviations did not exceed 1 hour. Based on laboratory historical data these deviations are considered not to affect the study integrity. Temporary deviation in the humidity in the second cytogenetic assay are explained in protocol deviation 3.

Metabolic activation system
Preparation of S9-fraction: In the dose range finding test and the first and second cytogenetic assay rat liver microsomal enzymes were routinely prepared from adult male Wistar rats (6), which were obtained from Charles River (Sulzfeld, Germany).
The animals were housed at WIL Research Europe in a special room under standard laboratory conditions, as described in the Standard Operating Procedures, and allowed to acclimatise for at least 5 days. The rats were orally dosed at three consecutive days with a suspension of phenobarbital (80 mg/kg body weight; Bufa B.V., IJsselstein, The Netherlands) and ß-naphthoflavone (100 mg/kg body weight; Sigma) in corn oil (they were denied access to food for 3 to 4 hours preceding each dosing). One day after the final exposure (24 h), the rats were sedated using oxygen/carbon dioxide and then killed by decapitation. The rats received a limited quantity of food during the night before sacrifice. The livers of the rats were removed aseptically, and washed in cold (0°C), sterile 0.1 M sodium phosphate buffer (pH 7.4) containing 0.1 mM Na2-EDTA (Merck, Darmstadt, Germany). The livers were minced in a blender and homogenised in 3 volumes of phosphate buffer with a Potter homogeniser. The homogenate was centrifuged for 15 min at 9000 g. The supernatant (S9) was transferred into sterile ampules, which were stored in liquid nitrogen (-196°C) for a maximum of 1 year.
The S9 batch was characterised in a bacterial reverse mutation assay in Salmonella typhimurium tester strain TA98 with the mutagens Benzo-(a)-pyrene (Sigma) and 2-aminoanthracene (Sigma) at concentrations of 5 µg/plate and 1 µg/plate, respectively. These mutagens require metabolic activation for exerting their mutagenic effects.
In the cytogenetic assay 2A rat liver microsomal enzymes (S9 homogenate) were obtained from Trinova Biochem GmbH, Giessen, Germany and was prepared from male Sprague Dawley rats that have been dosed orally with a suspension of phenobarbital (80 mg/kg body weight) and ß-naphthoflavone (100 mg/kg) (see protocol deviation 4).

Preparation of S9-mix: S9-mix was prepared immediately before use and kept on ice. S9-mix components contained per ml: 1.63 mg MgCl2.6H2O (Merck); 2.46 mg KCl (Merck); 1.7 mg glucose-6-phosphate (Roche, Mannheim, Germany); 3.4 mg NADP (Randox Laboratories Ltd., Crumlin, United Kingdom); 4 µmol HEPES (Invitrogen Corporation).
The above solution was filter (0.22 µm)-sterilized. To 0.5 ml S9-mix components 0.5 ml S9-fraction was added (50% (v/v) S9-fraction) to complete the S9-mix.
Metabolic activation was achieved by adding 0.2 ml S9-mix to 5.3 ml of a lymphocyte culture (containing 4.8 ml culture medium, 0.4 ml blood and 0.1 ml (9 mg/ml) phytohaemagglutinin). The concentration of the S9-fraction in the exposure medium was 1.8% (v/v).

Study design
Dose range finding test / First cytogenetic assay: In order to select the appropriate dose levels for the chromosome aberration test cytotoxicity data were obtained in a dose range finding test. Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene was tested in the absence and in the presence of 1.8% (v/v) S9-fraction.
Lymphocytes (0.4 ml blood of a healthy male donor was added to 5 ml or 4.8 ml culture medium, without and with metabolic activation respectively and 0.1 ml (9 mg/ml) Phytohaemagglutinin) were cultured for 48 h and thereafter exposed to selected doses of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene for 3 h, 24 h and 48 h in the absence of S9-mix or for 3 h in the presence of S9-mix. A negative control was included at each exposure time.
The highest tested concentration was determined by the solubility of the test substance in the culture medium at the 3 h exposure time. At the 24 and 48 h exposure time, the test substance was tested beyond the limit of solubility to obtain adequate toxicity data.
The test substance precipitated at concentrations of 100 µg/ml and upwards. The lymphocytes were cultured in duplicate at the 3 h exposure time and appropriate vehicle and positive controls were included.
After 3 h exposure to Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene in the absence or presence of S9-mix, the cells were separated from the exposure medium by centrifugation (5 min, 365 g). The supernatant was removed and cells were rinsed with 5 ml HBSS. After a second centrifugation step, HBSS was removed and cells were resuspended in 5 ml culture medium and incubated for another 20 - 22 h (24 h fixation time). The cells that were exposed for 24 h and 48 h in the absence of S9-mix were not rinsed after exposure but were fixed immediately (24 h and 48 h fixation time).
Cytotoxicity of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene in the lymphocyte cultures was determined using the mitotic index.
No cytotoxicity was observed in the duplicate cultures of the 3 h exposure time and the slides were scored for chromosome aberrations. The first cytogenetic assay was omitted.
Based on the results of the dose range finding test an appropriate range of dose levels was chosen for the second cytogenetic assay considering the highest dose level had an inhibition of the mitotic index of 50% or greater whereas the mitotic index of the lowest dose level was approximately the same as the mitotic index of the solvent control.

Second cytogenetic assay: The cytogenetic assay was carried out as described by Evans, 1984 (2) with minor modifications. Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene was tested in the absence and presence of 1.8% (v/v) S9-fraction in duplicate.
Lymphocytes were cultured for 48 h and thereafter exposed in duplicate to selected doses of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene for 24 h and 48 h in the absence of S9-mix and for 3 h in the presence of S9-mix.
After 3 h exposure, the cells exposed to Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene in the presence of S9-mix were separated from the exposure medium by centrifugation (5 min, 365 g). The supernatant was removed and the cells were rinsed once with 5 ml of HBSS and incubated in 5 ml culture medium for another 44 - 46 h (48 h fixation time).
The cells that were treated for 24 h and 48 h in the absence of S9-mix were not rinsed after exposure but were fixed immediately after 24 h and 48 h (24 h and 48 h fixation time).
Appropriate negative and positive controls were included in the second cytogenetic assay.

Chromosome preparation: During the last 2.5 - 3 h of the culture period, cell division was arrested by the addition of the spindle inhibitor colchicine (0.5 µg/ml medium) (Acros Organics, Geel, Belgium). Thereafter the cell cultures were centrifuged for 5 min at 365 g and the supernatant was removed. Cells in the remaining cell pellet were swollen by a 5 min treatment with hypotonic 0.56% (w/v) potassium chloride (Merck) solution at 37°C. After hypotonic treatment, cells were fixed with 3 changes of methanol (Merck): acetic acid (Merck) fixative (3:1 v/v).

Preparation of slides: Fixed cells were dropped onto cleaned slides, which were immersed in a 1:1 mixture of 96% (v/v) ethanol (Merck)/ether (Merck) and cleaned with a tissue. The slides were marked with the WIL Research Europe study identification number and group number. At least two slides were prepared per culture. Slides were allowed to dry and thereafter stained for 10 - 30 min with 5% (v/v) Giemsa (Merck) solution in tap water. Thereafter slides were rinsed in tap-water and allowed to dry. The dry slides were automatically embedded in a 1:10 mixture of xylene (Klinipath, Duiven, The Netherlands)/pertex (Klinipath) and mounted with a coverslip in an automated coverslipper (Leica Microsystems B.V., Rijswijk, The Netherlands).

Mitotic index/dose selection for scoring of the cytogenetic assay: The mitotic index of each culture was determined by counting the number of metaphases from at least 1000 cells (with a maximum deviation of 5%). At least three analysable concentrations were used for scoring of the cytogenetic assay. Chromosomes of metaphase spreads were analysed from those cultures with an inhibition of the mitotic index of about 50% or above whereas the mitotic index of the lowest dose level was approximately the same as the mitotic index of the solvent control. Also cultures treated with an intermediate dose were examined for chromosome aberrations. In case Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene was not cytotoxic and/or difficult to dissolve in aqueous solutions, the highest concentration analysed at the 3 h exposure time was determined by the solubility in the culture medium. If dose related cytotoxicity was observed, the highest concentration analysed at the 24 and 48 h continuous exposure times was based on toxicity irrespective of the solubility of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene in the culture medium. However, the extent of precipitation may not interfere with the scoring of chromosome aberrations.

Analysis of slides for chromosome aberrations: To prevent bias, all slides were randomly coded before examination of chromosome aberrations and scored. An adhesive label with WIL Research Europe study identification number and code was placed over the marked slide. One hundred metaphase chromosome spreads per culture were examined by light microscopy for chromosome aberrations. In case the number of aberrant cells, gaps excluded, was ≥ 25 in 50 metaphases, no more metaphases were examined. Only metaphases containing 46 ± 2 centromeres (chromosomes) were analysed. The number of cells with aberrations and the number of aberrations were calculated.
Evaluation criteria:
A test substance was considered positive (clastogenic) in the chromosome aberration test if:
It induced a dose-related statistically significant (Chi-square test, one-sided, p < 0.05) increase in the number of cells with chromosome aberrations.
A statistically significant and biologically relevant increase in the frequencies of the number of cells with chromosome aberrations was observed in the absence of a clear dose-response relationship.

A test substance was considered negative (not clastogenic) in the chromosome aberration test if none of the tested concentrations induced a statistically significant (Chi-square test, one-sided, p < 0.05) increase in the number of cells with chromosome aberrations.

The preceding criteria are not absolute and other modifying factors might enter into the final evaluation decision.
Statistics:
The incidence of aberrant cells (cells with one or more chromosome aberrations, gaps included or excluded) for each exposure group outside the laboratory historical control data range was compared to that of the solvent control using Chi-square statistics:

(N-1) (ad-bc)2
X2 = --------------------------------
(a+b) (c+d) (a+c) (b+d)

where b = the total number of aberrant cells in the control cultures.
d = the total number of non aberrant cells in the control cultures.
n0 = the total number of cells scored in the control cultures.
a = the total number of aberrant cells in treated cultures to be compared with the control.
c = the total number of non aberrant cells in treated cultures to be compared with the control.
n1 = the total number of cells scored in the treated cultures.
N = sum of n0 and n1
(N-1) (ad-bc)2
If P X2 > ------------------------------- (one-tailed) is small (p< 0.05) the hypothesis that the
(a+b) (c+d) (a+c) (b+d)

incidence of cells with chromosome aberrations is the same for both the treated and the solvent control group is rejected and the number of aberrant cells in the test group is considered to be significantly different from the control group at the 95% confidence level.
Species / strain:
lymphocytes: cultured peripheral human lymphocytes
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Additional information on results:
Dose range finding test / First cytogenetic assay: At a concentration of 100 µg/ml the test substance precipitated in the culture medium. In the dose range finding study, at the 3 h exposure time, blood cultures were treated in duplicate with 10, 33 and 100 µg test substance/ml culture medium with and without S9-mix (first cytogenetic assay).
At the 24 h and 48 h continuous exposure time blood cultures were treated with 1, 3, 10, 33, 100, 333 and 1000 µg test substance/ml culture medium without S9-mix. The test substance was tested beyond the limit of solubility to obtain adequate toxicity data.
All dose levels were selected for scoring of chromosome aberrations.
Both in the absence and presence of S9-mix, Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene did not induce a statistically significant or biologically relevant increase in the number of cells with chromosome aberrations.
Both in the absence and presence of S9-mix, Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene did not increase the number of polyploid cells and cells with endoreduplicated chromosomes.

Second cytogenetic assay: To obtain more information about the possible clastogenicity of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene, a second cytogenetic assay was performed in which human lymphocytes were continuously exposed to the test substance in the absence of S9-mix for 24 or 48 hours. In the presence of S9-mix, cells were fixed after 48 hours following a 3 hour exposure to Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene. Further investigation showed that a concentration of 50 µg/ml already precipitated in the culture medium. The following dose levels were selected for the second cytogenetic assay:

Without S9-mix: 1, 3, 10, 30, 50, 100, 200 and 300 µg/ml culture medium
(24 and 48 h exposure time, 24 and 48 h fixation time).
With S9-mix: 10, 30 and 50 µg/ml culture medium
(3 h exposure time, 48 h fixation time).

Based on these observations the following doses were selected for scoring of chromosome aberrations:

Without S9-mix: 10, 30 and 200 µg/ml culture medium
(24 h exposure time, 24 h fixation time).
10, 30 and 100 µg/ml culture medium
(48 h exposure time, 48 h fixation time).
With S9-mix: 10, 30 and 50 µg/ml culture medium
(3 h exposure time, 48 h fixation time).

Both in the absence and presence of S9-mix, Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene did not induce a statistically significant or biologically relevant increase in the number of cells with chromosome aberrations.
Both in the absence and presence of S9-mix, Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene did not increase the number of polyploid cells and cells with endoreduplicated chromosomes.

Chemical analysis of dose preparations: The concentrations analysed in the samples prepared for use were in agreement with the nominal concentrations (i.e. mean accuracies 88 and 93%). Analysis of low and high formulations after storage yielded a relative difference of ≤ 10%. Based on this, the formulations were found to be stable when stored at room temperature under normal laboratory light conditions for at least 4 hours.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Chromosome aberrations in human lymphocyte cultures treated with Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene

 

In the absence of S9-mix in the second cytogentic assay (24h exposure time, 24 h fixation time)

Conc

DMSO

(1.0% v/v)

10

 μg/ml

30

μg/ml

200

 μg/ml

MMC-C

0.2μg/ml

Culture

A

B

A+B

A

B

A+B

A

B

A+B

A

B

A+B

A

B

A+B

Mitotic Index (%)

100

92

87

66

47

No. of Cells scored

100

100

200

100

100

200

100

100

200

100

100

200

100

100

200

No. of Cells with aberrations (+ gaps)a)

1

0

1

0

1

1

0

0

0

1

0

1

32

29

***)61

No. of Cells with aberrations (- gaps)

1

0

1

0

1

1

0

0

0

1

0

1

30

25

***)55

g’

 

 

 

 

 

 

 

 

 

 

 

 

2

3

 

g”

 

 

 

 

 

 

 

 

 

 

 

 

4

3

 

b’

 

 

 

 

 

 

 

 

 

1

 

 

14

7

 

b”

 

 

 

 

1

 

 

 

 

 

 

 

15

10

 

m’

1

 

 

 

 

 

 

 

 

 

 

 

4

2

 

m”

 

 

 

 

 

 

 

 

 

 

 

 

1

3

 

exch.

 

 

 

 

 

 

 

 

 

 

 

 

4

3

 

dic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

d’

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

misc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

total aberr (+ gaps)

1

0

 

0

1

 

0

0

 

1

0

 

44

31

 

total aberr

 (- gaps)

1

0

 

0

1

 

0

0

 

1

0

 

38

25

 

 

In the absence of S9-mix in the second cytogenetic assay (48h exposure time, 48h fixation time)

Conc

DMSO

(1.0% v/v)

10

μg/ml

30

μg/ml

100

μg/ml

MMC-C

 0.1μg/ml

Culture

A

B

A+B

A

B

A+B

A

B

A+B

A

B

A+B

A

B

A+B

Mitotic Index (%)

100

93

89

32

53

No. of Cells scored

100

100

200

100

100

200

100

100

200

100

100

200

100

100

200

No. of Cells with aberrations (+ gaps)a)

0

0

0

0

0

0

0

0

0

1

0

1

28

28

***) 56

No. of Cells with aberrations (- gaps)

0

0

0

0

0

0

0

0

0

1

0

1

24

24

***) 48

g’

 

 

 

 

 

 

 

 

 

 

 

 

3

3

 

g”

 

 

 

 

 

 

 

 

 

 

 

 

2

4

 

b’

 

 

 

 

 

 

 

 

 

1

 

 

5

6

 

b”

 

 

 

 

 

 

 

 

 

 

 

 

10

11

 

m’

 

 

 

 

 

 

 

 

 

 

 

 

1

2

 

m”

 

 

 

 

 

 

 

 

 

 

 

 

4

3

 

exch.

 

 

 

 

 

 

 

 

 

 

 

 

5

1

 

dic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

d’

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

misc.

 

 

 

poly

2poly

 

 

 

poly

 

 

p

p,poly

total aberr (+ gaps)

0

0

 

0

0

 

0

0

 

1

0

 

31

32

 

total aberr (- gaps)

0

0

 

0

0

 

0

0

 

1

0

 

26

25

 

The numerical variation polyploidy (poly) was not counted as an aberration.

 

In the presence of S9-mix in the second cytogenetic assay (3h exposure time, 48h fixation time)

Conc

DMSO

(1.0% v/v)

10

μg/ml

30

μg/ml

50

μg/ml

CP 10

μg/ml

Culture

A

B

A+B

A

B

A+B

A

B

A+B

A

B

A+B

A

B

A+B

Mitotic Index (%)

100

109

129

116

-b)

No. of Cells scored

100

100

200

100

100

200

100

100

200

100

100

200

100

100

200

No. of Cells with aberrations (+ gaps)a)

0

0

0

1

0

1

1

0

1

0

0

0

30

29

***) 59

No. of Cells with aberrations (- gaps)

0

0

0

1

0

1

0

0

0

0

0

0

28

28

***) 56

g’

 

 

 

 

 

 

1

 

 

 

 

 

 

1

 

g”

 

 

 

 

 

 

 

 

 

 

 

 

2

1

 

b’

 

 

 

1

 

 

 

 

 

 

 

 

16

14

 

b”

 

 

 

 

 

 

 

 

 

 

 

 

17

11

 

m’

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

m”

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

exch.

 

 

 

 

 

 

 

 

 

 

 

 

2

4

 

dic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

d’

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

misc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

total aberr (+ gaps)

0

0

 

1

0

 

1

0

 

0

0

 

37

33

 

total aberr (- gaps)

0

0

 

1

0

 

0

0

 

0

0

 

35

31

 

a)Abbreviations use for various types of aberrations are listed in APPENDIX 2 (detailed under Overall Remarks). Misc. = (miscellaneous) aberrations not belonging to the ones mentioned above.

b)CP was fixed after 24 hours. Therefore, the mitotic index could not be calculated as percentage of control.

*) Significantly different from control group (Chi-square test), *P < 0.05, **P < 0.01 or ***P < 0.001.

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

It is concluded that this test is valid and that Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene is not clastogenic in human lymphocytes under the experimental conditions described in the report.
Executive summary:

Evaluation of the ability of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene to induce chromosome aberrations in cultured peripheral human lymphocytes (with repeat experiment).

 

This report describes the effect of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene on the number of chromosome aberrations in cultured peripheral human lymphocytes in the presence and absence of a metabolic activation system (phenobarbital and ß-naphthoflavone induced rat liver S9-mix). The possible clastogenicity of the test substance was tested in two independent experiments.

 

The study procedures described in this report were based on the most recent OECD and EC guidelines.

 

Batch EL2B27G336 of Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene was a clear red-brown viscous liquid. The test substance was dissolved in dimethyl sulfoxide.

 

The concentrations analysed in the samples prepared for use were in agreement with the nominal concentrations (i.e. mean accuracies 88 and 93%). Analysis of low and high formulations after storage yielded a relative difference of ≤ 10%. Based on this, the formulations were found to be stable when stored at room temperature under normal laboratory light conditions for at least 4 hours.

 

In the first cytogenetic assay, Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene was tested up to 100 µg/ml for a 3 h exposure time with a 24 h fixation time in the absence and presence of 1.8% (v/v) S9-fraction. The test substance precipitated in the culture medium at this dose level.

 

In the second cytogenetic assay, the test substance was tested up to 200 µg/ml for a 24 h continuous exposure time with a 24 h fixation time and up to 100 µg/ml for a 48 h continuous exposure time with a 48 h fixation time in the absence of S9-mix. Appropriate toxicity was reached at these dose levels. In the presence of S9-the test substance was tested up to 50 µg/ml for a 3 h exposure time with a 48 h fixation time. The test substance precipitated in the culture medium at this dose level.

 

The number of cells with chromosome aberrations found in the solvent control cultures was within the laboratory historical control data range. Positive control chemicals, mitomycin C and cyclophosphamide, both produced a statistically significant increase in the incidence of cells with chromosome aberrations, indicating that the test conditions were adequate and that the metabolic activation system (S9-mix) functioned properly.

 

Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene did not induce a statistically significant or biologically relevant increase in the number of cells with chromosome aberrations in the absence and presence of S9-mix, in either of the two independently repeated experiments.

 

No effects of the test substance on the number of polyploid cells and cells with endoreduplicated chromosomes were observed both in the absence and presence of S9-mix. Therefore it can be concluded that Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4-trimethylpentene does not disturb mitotic processes and cell cycle progression and does not induce numerical chromosome aberrations under the experimental conditions described in this report.

 

Finally, it is concluded that the test is valid and that Benzenamine, N-phenyl-, reaction products with styrene and 2,4,4 -trimethylpentene is not clastogenic in human lymphocytes under the experimental conditions described in the report.

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not specified
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay
Target gene:
Not specified
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
E. coli WP2 uvr A
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
10% Liver S9
Test concentrations with justification for top dose:
50, 150, 500, 1500, 5000 ug/plate
Vehicle / solvent:
Acetone
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
yes
Remarks:
Acetone
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
9-aminoacridine
N-ethyl-N-nitro-N-nitrosoguanidine
Remarks:
without activation Migrated to IUCLID6: 9-aminoacridine, 4-nitroquinoline-1-oxide
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
yes
Remarks:
Acetone
True negative controls:
not specified
Positive controls:
yes
Positive control substance:
other: 2-Aminoantracene (2AA),
Remarks:
with activation
Details on test system and experimental conditions:
The S. typhymurium strains were obtained from the University of California (Berkeley), and the E. coli strain was obtained from the British Industrial Biological Research Association. Overnight subcultures of the stock cultures were prepared in nutrient broth and incubated at 37°C for approximately 10 hours. The test material was dissolved in acetone to prepare the test concentrations noted above. Vehicle and positive controls were run in parallel with the test material. The positive controls were as follows:
Non-activation
TA100: N-ethy-N’-nitrosoquanidine (ENNG), 3 μg/plate
TA1535: ENNG, 5 μg/plate
TA1537: 9-aminoacridine, 80 μg/plate
TA98: 4-nitroquinoline-1-oxide, 0.2 μg/plate
WP2uvrA-: ENNG, 2 μg/plate
Activation (10% liver S9)
TA100: 2-Aminoantracene (2AA), 1 μg/plate
TA1535: 2AA, 2 μg/plate
TA1537: 2AA, 2 μg/plate
TA98: 2AA, 0.5 μg/plate
WP2uvrA-: 2AA, 10 μg/plate
A preliminary toxicity study was conducted to select the appropriate dose levels. Five doses of the test material and the vehicle control (acetone) were tested in duplicate. In addition, 0.1 ml of the maximum concentration of the test material and 2 ml of the molten medium were overlayed onto an agar plate. After 48 hours incubation at 37°C the plates were assessed for revertant colonies.
Two experiments were conducted to assess reproducibility.
Evaluation criteria:
A substance was considered positive if it induced a dose-related and statistically significant increase in mutation rate (at least twice the spontaneous reversion rate) in one or more strains with or without activation. (Note: In the event of two equivocal experiments a third experiment may be used.) To be considered negative the number of induced revetants compared to the spontaneous revertants should be less than two fold at each dose level employed, the intervals of which should be between two and five fold and extend to the limits imposed by toxicity, solubility or up to the maximum recommended dose of 5000 ug/plate. (Note: In this case the limiting factor was the maximum recommended dose.)
Statistics:
Not specified
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
not specified
Untreated negative controls validity:
not examined
Positive controls validity:
not specified
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
not specified
Untreated negative controls validity:
not examined
Positive controls validity:
not specified
Additional information on results:
No toxicity was observed to any of the strains. Precipitates were observed at 1500 ug/plate and 5000 ug/plate but did not interfere with scoring. No significant increase in the frequency of revetant colonies was recorded in any strain with or without activation, and the responses of the positive controls were satifactory.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
negative with and without metabolic activation

Cytotoxicity conc: With and without metabolic activation: None toxic
Precipitation conc: 1500 and 5000 ug/plate
Genotoxic effects: With and without metabolic activation: negative
Executive summary:

Study conducted to OECD and EU test guidelines in compliance with GLP.

Results: Cytotoxicity conc: With and without metabolic activation: None toxic

Precipitation conc: 1500 and 5000 ug/plate

Genotoxic effects: With and without metabolic activation: negative

 

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

Mutagenicity, in vivo and in vitro

Link to relevant study records
Reference
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
Study period:
Not specified
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
not specified
GLP compliance:
yes
Type of assay:
micronucleus assay
Species:
mouse
Strain:
CD-1
Sex:
male
Details on test animals and environmental conditions:
Not specified
Route of administration:
oral: gavage
Vehicle:
Corn oil
Details on exposure:
Not applicable.
Duration of treatment / exposure:
single dose
Frequency of treatment:
Once
Post exposure period:
24 and 48 hours
Remarks:
Doses / Concentrations:
0, 500, 1000 and 2000 mg/kg
Basis:
actual ingested
No. of animals per sex per dose:
Five male mice per dose.
Control animals:
yes, concurrent vehicle
Positive control(s):
Cyclophosphamide
Tissues and cell types examined:
polychromaticerythrocytes (PCE) and nonchromatic erythrocytes (NCE)
Details of tissue and slide preparation:
Bone marrow cells were harvested 24 and 48 hours after dosing. All dose levels, the vehicle control and a positive control (Cyclophosphamide) were evaluated at the 24 hours. At 48 hours, only the vehicle control and high dose were evaluated.
Bone marrow was taken from the hind limbs. Slides were prepared from the bone marrow extracts, fixed with methanol and stained in May Grunwald Solution and Giemsa. Two thousand micronucleated polychromatic erythrocytes were evaluated for micronuclei.
Evaluation criteria:
The ratio of polychromatic erythrocytes (PCE) to nonchromatic erythrocytes (NCE) cells was determined from the first 500 erythrocytes on each slide.
Statistics:
Statistical analyses were performed using Analysis of Variance and Dunnett’s t-test.
Sex:
male
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
not specified
Negative controls validity:
not specified
Positive controls validity:
not specified
Additional information on results:
The test substance did not produce any signs of clinical toxicity. Statistically lower PCE:NCE ratios, while not dose related, did strongly indicate that the test substance was cytotoxic to the bone marrow. The test substance did not produce any statistically significant increase in micronucleated PCEs relative to the vehicle control at the 24-hour and 48-hour harvest interval.
The positive control induced a statistically significant increase in micronucleated PCEs compared to the vehicle control.
Conclusions:
Interpretation of results (migrated information): negative
The test substance was tested up to the limit dose (2000 mg/kg) and did not cause chromosome damage in the mouse bone marrow micronucleus assay under the conditions of this test.
Executive summary:

Study conducted to OECD test guidelines in compliance with GLP. Data included for OECD SIDS dossier. The test substance did not produce any signs of clinical toxicity. Statistically lower PCE:NCE ratios, while not dose related, did strongly indicate that the test substance was cytotoxic to the bone marrow. The test substance did not produce any statistically significant increase in micronucleated PCEs relative to the vehicle control at the 24-hour and 48-hour harvest interval. The positive control induced a statistically significant increase in micronucleated PCEs compared to the vehical control. Result: The test substance was tested up to the limit dose (2000 mg/kg) and did not cause chromosome damage in the mouse bone marrow micronucleus assay under the conditions of this test.

Read across to supporting substance, CAS No. 68442 -68 -2, by structural analogue. This substance has been supported under Environmental Protection Agency’s (EPA’s) High Production Volume (HPV) Challenge Program. The American Chemical Councils RAPA Panel, has derived a “Substituted Diphenylamines” category of chemicals for this substance, please refer to EPA reference 201-14700A located at

 

http://www.epa.gov/hpv/pubs/summaries/subdipha/c13378rt.pdf

 

Relying on several factors specified in EPA’s guidance document on “Development of Chemical Categories in the HPV Challenge Program,” in which use of chemical categories is encouraged, the following closely related chemicals constitute a chemical category:

 

Structural Similarity. A key factor supporting the classification of these chemicals as a category is their structural similarity (see Figure 1). All share a common starting material; Diphenylamine (Benzenamine, N-phenyl-, CAS# 122-39-4), a common synthetic pathway, and all compounds in this category are diamines with various substitutions.

 

Similarity of Physicochemical Properties. The similarity of the physicochemical properties of these materials parallels their structural similarity. All are off-white to light brown solids or viscous liquids intended for use as antioxidants in finished rubber articles or as antidegradant additives that extend the useful life of heavy-duty industrial functional fluids used in high-speed, high-temperature and/or high-load applications. As a class, these amine-based antidegradant compounds are less migratory (more polymer-bound) and less staining than the Substituted p-Phenylenediamine antidegradants. The use of these materials requires that they be stable under high temperatures. Their low volatility is due to their low vapor pressure, highly viscous or solid form. The existing information for these materials indicates that they have low water solubility and high flash points.

 

Toxicological Similarity. Review of existing published and unpublished test data for Substituted Diphenylamines shows the aquatic and mammalian toxicity among the materials within this category are similar.

 

Mammalian Toxicology - Mutagenicity. Data from bacterial reverse mutation assays, in vitro and in vivo chromosome aberration studies, as well as additional supporting in vitro and in vivo genetic toxicity studies were reviewed, and the findings indicate a low concern for mutagenicity either for aryl or alkyl substituted materials. Similarly, the data for a mixed aryl/alkyl substituted molecule also indicates a lack of mutagenicity. Data are available for several members of the category or close structural analogs, and these data can be bridged to the other members of the category. Therefore, for the purposes of the HPV Program, the category has been adequately tested for mutagenicity, and no additional mutagenicity testing is proposed.

 

Conclusion. Based upon the data reviewed in “Substituted Diphenylamines” category of chemicals, the physicochemical and toxicological properties of the Substituted Diphenylamine category members are similar and follow a regular pattern as a result of that structural similarity. Therefore, the definition of a chemical category has been met, and read across is considered appropriate for the category of chemical.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vivo:

The substance was negative in the following tests:

1) Ames Test x 2- salmonella/ e.coli

2) Chromosome aberration test - human lymphocytes.

3) In-vivo Micronucleus Test – mice (read-across)

Two separate bacterial reverse mutation tests showed that the substance does not have any mutagenic properties in different Salmonella strains. In addition, no genotoxic properties have been seen in in-vitro chromosome aberration nor in an in-vivo Micronucleus Test in mice with a structurally very similar compound. Repeat-dose studies with oral treatment in rats did not reveal any tumorigenic properties which could be related to the administration of the test substance. Consequently, additional testing of the test substance in an in vitro gene mutation study in mammalian cells does not appear scientifically necessary and this test has been waived.

The following information is taken into account for any hazard / risk assessment:

Genetic toxicity "in vitro" is discussed below.

Value used for CSA:Genetic toxicity: negative

This substance has been supported under Environmental Protection Agency’s (EPA’s) High Production Volume (HPV) Challenge Program. The American Chemical Councils RAPA Panel, has derived a “Substituted Diphenylamines” category of chemicals for this substance, please refer to EPA reference 201-14700A located at

 

http://www.epa.gov/hpv/pubs/summaries/subdipha/c13378rt.pdf

 

Relying on several factors specified in EPA’s guidance document on “Development of Chemical Categories in the HPV Challenge Program,” in which use of chemical categories is encouraged, the chemicals constitute a chemical category on the following basis:

 

Structural Similarity. A key factor supporting the classification of these chemicals as a category is their structural similarity (see Figure 1). All share a common starting material; Diphenylamine (Benzenamine, N-phenyl-, CAS# 122-39-4), a common synthetic pathway, and all compounds in this category are diamines with various substitutions.

 

Similarity of Physicochemical Properties. The similarity of the physicochemical properties of these materials parallels their structural similarity. All are off-white to light brown solids or viscous liquids intended for use as antioxidants in finished rubber articles or as antidegradant additives that extend the useful life of heavy-duty industrial functional fluids used in high-speed, high-temperature and/or high-load applications. As a class, these amine-based antidegradant compounds are less migratory (more polymer-bound) and less staining than the Substituted p-Phenylenediamine antidegradants. The use of these materials requires that they be stable under high temperatures. Their low volatility is due to their low vapor pressure, highly viscous or solid form. The existing information for these materials indicates that they have low water solubility and high flash points.

 

Toxicological Similarity. Review of existing published and unpublished test data for Substituted Diphenylamines shows the aquatic and mammalian toxicity among the materials within this category are similar.

 

Mammalian Toxicology - Mutagenicity. Data from bacterial reverse mutation assays, in vitro and in vivo chromosome aberration studies, as well as additional supporting in vitro and in vivo genetic toxicity studies were reviewed, and the findings indicate a low concern for mutagenicity either for aryl or alkyl substituted materials. Similarly, the data for a mixed aryl/alkyl substituted molecule also indicates a lack of mutagenicity. Data are available for several members of the category or close structural analogs, and these data can be bridged to the other members of the category. Therefore, for the purposes of the HPV Program, the category has been adequately tested for mutagenicity, and no additional mutagenicity testing is proposed.

 

Conclusion. Based upon the data reviewed in “Substituted Diphenylamines” category of chemicals, the physicochemical and toxicological properties of the Substituted Diphenylamine category members are similar and follow a regular pattern as a result of that structural similarity. Therefore, the definition of a chemical category has been met, and read across is considered appropriate for the category of chemical.


Justification for selection of genetic toxicity endpoint
All studies are negative; hence the in vivo study is selected for completeness purposes.

Justification for classification or non-classification

The above studies have all been ranked reliability 1 according to the Klimisch et al system. This ranking was deemed appropriate because the studies were conducted to GLP an in compliance with agreed protocols. Sufficient dose ranges and numbers are detailed; hence it is appropriate for use based on reliability and animal welfare grounds. As the effects are considered adaptive rather than toxicological, no classification is proposed.

The above results triggered no classification under the CLP Regulation (EC No 1272/2008). No classification for mutagenicity is therefore required.