N-(4-chlorophenyl)-2-[(4-methyl-2-nitrophenyl)azo]-3-oxobutyramide

Endpoint summary

Description of key information

Skin irritation/corrosion: no skin irritation or severe skin burns and eye damage
Eye irritation: no serious eye irritation or damage

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 23 NOV 1976 to 26 NOV 1976

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Reliability of the original study (GLP compliant guideline study) as such was 2 (Acceptable, well-documented study report which meets basic scientific principles). Additional downgrading owed to application of read across is considered to be redundant.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: FDA guideline (Fed. Reg. Vol. 38, No. 187, p. 27019, 1973)

Deviations:

not specified

GLP compliance:

no

Remarks:

study was performed previous to GLP implementation

Species:

rabbit

Strain:

Himalayan

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 1,5-2,0 kg
- Housing: single
- Diet: mixed feed ERKA 8300 (Robert Koch, Hamm, Germany), ad libitum
- Water: tap water, ad libitum

Type of coverage:

occlusive

Preparation of test site:

other: clipped/intact or clipped/scarified

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied: 500 mg

Duration of treatment / exposure:

24 h

Observation period:

48 h after end of exposure

Number of animals:

6

Details on study design:

TEST SITE
- Area of exposure: 2.5 x 2.5 cm gauze patch
- Type of wrap if used: PVC foil, elastic bandage

REMOVAL OF TEST SUBSTANCE
- Time after start of exposure: 24 h

SCORING SYSTEM: described in § 1500.41 in Fed. Reg. 38, No. 187, 27.09.1973, p. 27019, in accordance with OECD TG 404.
Scores were assessed 24, 48 and 72 h after start of exposure, which lasted for 24 h. For classification, the readings are stated here as immediately, 24 and 48 h after end of exposure.

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: 24 and 48 h

Score:

0

Max. score:

4

Reversibility:

other: not relevant since no effect

Remarks on result:

other: intact and scarified

Irritation parameter:

edema score

Basis:

mean

Time point:

other: 24 and 48 h

Score:

0

Max. score:

4

Reversibility:

other: not relevant since no effect

Remarks on result:

other: intact and scarified

Irritant / corrosive response data:

Erythema and edema scores immediately after exposure were 0 as well as at later time points.
The same results were observed with scarified skin

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test material is not irritating to skin under these test conditions. This conclusion is legitimate even though the applied testing regime differs from today's standard methods, as no skin responses were observed in 6/6 animals 24 and 48 h after exposure, which lasted 20 h longer than required by OECD TG 404.

Executive summary:

The test material was tested for skin irritancy according to FDA guidelines. Both intact and scarified skin sites of six rabbits were exposed to 500 mg test substance for 24 h under occlusive conditions and the skin responses were watched for 48 hours after end of exposure. Neither erythema nor edema were noted 24 and 48 h after end of exposure. The test material is not irritating to skin under these test conditions.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 23 NOV 1976 to 26 NOV 1976

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Reliability of the original study (GLP compliant guideline study) as such was 2 (Acceptable, well-documented study report which meets basic scientific principles). Additional downgrading owed to application of read across is considered to be redundant.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: FDA guideline (Fed. Reg. Vol. 38, No. 187, p. 27019, 1973)

Deviations:

not specified

GLP compliance:

no

Remarks:

study was performed previous to GLP implementation

Species:

rabbit

Strain:

Himalayan

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Housing: single
- Diet: mixed feed ERKA 8300 (Robert Koch, Hamm, Germany), ad libitum
- Water: tap water, ad libitum

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied: 100 mg

Duration of treatment / exposure:

24 h

Observation period (in vivo):

72 h

Number of animals or in vitro replicates:

6

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing: with physiological saline
- Time after start of exposure: 24 h

SCORING SYSTEM: basically in accordance with OECD TG 405.
Scores were read 1, 7, 24, 48 and 72 h after test substance application.

TOOL USED TO ASSESS SCORE: hand-slit lamp / fluorescein at 48 and 72 h reading

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

other: 24, 48 and 72 h

Score:

0

Max. score:

4

Reversibility:

other: not relevant since no effect

Irritation parameter:

iris score

Basis:

mean

Time point:

other: 24, 48 and 72 h

Score:

0

Max. score:

2

Reversibility:

other: not relevant since no effect

Irritation parameter:

conjunctivae score

Remarks:

redness

Basis:

mean

Time point:

other: 24, 48 and 72 h

Score:

0

Max. score:

3

Reversibility:

other: not relevant since no effect

Irritation parameter:

chemosis score

Basis:

mean

Time point:

other: 24, 48 and 72 h

Score:

0

Max. score:

4

Reversibility:

other: not relevant since no effect

Irritant / corrosive response data:

Redness of the conjunctiva was observed in all six animals at the 1 h reading (scores 1) . This effect was still obervable at the 7 h reading, but was completely reversible 24 h after application (score 0). Chemosis was noted in three animals at the 1 h reading (individual scores are 1). This effect was reversible at the 7 h reading. No other effects on the eyes were observed.

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test material was not irritating to eyes in all animals under test conditions which are basically in accordance with todays standard methods regarding dosing, exposure duration, scoring system and reading time points. Therefore, it is concluded that the submission substance is not irritating to eyes.

Executive summary:

Test material was subject to a test of eye irritancy according to FDA guidelines (Fed. Reg. Vol. 38, No. 187, p. 27019, 1973). 100 mg of substance were applied to one eye of six animals each. The eyes were washed 24 h after application and eye responses were noted for 72 h. Slight effects on the conjunctiva 1 and 7 hours after start of the exposure were no longer visible at later time points. No effects were observed 24, 48 and 72 hours after start of the exposure.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Read Across Hypothesis

The read across approach covers two Monoazo Yellow Pigments. The pigments encompassed are:

CAS no.	EC no.	Substance Name (C.I. Name)	Substance Name	Substance Role
57206-89-0	260-618-3		N-(4-Chlorophenyl)-2-[(4-methyl-2-nitrophenyl)azo]-3-oxobutyramide	target
6486-23-3	229-355-1	PIGMENT YELLOW 3	2-[(4-chloro-2-nitrophenyl)azo]-N-(2-chlorophenyl)-3-oxobutyramide	source

 

The read across hypothesis is that both substances – based on a very similar chemical structure – have very similar physical-chemical properties, which also govern their toxicokinetic behavior, their toxicity, ecotoxicity and environmental behaviour. These properties

·       very low solubility in water but also in organic solvents

·       non-degradability

lead to inert behaviour and negligible bioavailability for both humans and environmental organisms. This hypothesis is supported by absence of relevant effects in any of the tests for any endpoint (see Data Matrix).

Three dimensional single crystal X-ray analysis (Herbst and Hunger, 2004) showed that the Monoazo Yellow Pigments have a very stable lattice, which is stabilized by intramolecular hydrogen bonds into an almost planar configuration. This, together with relatively high molecular masses suggests low bioavailability. This is supported by the very limited solubility in any kind of media.

Both substances decompose at temperatures below 300 °C. And both are only soluble to a limited extend in water andn-octanol. Water solubility is about 9.3 µg/L (target) and 7.5 μg/L (source). Solubility inn-octanol is low (target: 43.7 mg/L and source 6.0 mg/L). The corresponding n-octanol/water partitioning coefficients were calculated to be 3.67 for the target and 2.9 for the source substance. These values are well below the limit of concern of 4.5 considered to be critical for bioaccumulative properties.

Overall the available toxicological data from the source substance should easily and reliably be used to predict specific endpoints of the target substance.

List of endpoints covered

The read across approach is applied to the following endpoints:

-        Skin irritation

-        Eye irritation

-        Acute toxicity, oral route         

-        Short-term toxicity testing on Daphnia

 

Purities/Impurities

Both substances are synthesized in the same manner by azo coupling in aqueous media. Therefore they share a similar impurity profile. Both substances are of very high purity with > 97%. No noteworthy impurities have been identified. Impurities are most likely derived from the raw materials used.

 

Read Across Justification

The pigments of this approach are structurally similar and contain a substituted phenyl moiety, an azo moiety, and an oxobutyramide moiety. Minor differences are due to the number of Cl- (2 or 1) and methyl-substituents (0 or 1) and its different ring position. Both are solids, which decompose at high temperatures. The solubility of both pigments in water and n-octanol is very limited, < 10 μg/L and < 44 mg/L, respectively, resulting in a low partition coefficient in n-octanol/water (log Pow < 3.7), which is far below the limit of concern considered to be critical for bioaccumulative properties. When suspended in water both pigments yield nearly neutral pH values, which are entirely different from extreme values causing skin or eye corrosive reactions.

Monoazo Yellow Pigments generally show very limited biodegradability, which is assumed to be due to their unavailability for microorganisms. Lacking bioavailability is probably also the reason for the absence of any relevant mammalian toxicity: Both pigments didn’t show relevant toxic effect after single oral exposure up to the limit dose, skin sensitizing effect, or mutagenic properties.

These data indicate that the presence, number, position and identity of substituents do not influence the physico-chemical, ecotoxicological and toxicological behaviour of the pigments in a significant way.

In conclusion, structural similarities with very similar physico-chemical properties, environmental fate, and mammalian toxicity enable the prediction of acute oral toxicity and skin/eye irritation/corrosion of the target substance based on known properties of the source substance. Fulfillment of data requirements by read across from source to target substance is justified.

Data Matrix

Substance Role	Target	Source
Chemical name	N-(4-chlorophenyl)-2-[(4-methyl-2-nitrophenyl)azo]-3-oxobutyramide	PY 3
CAS no	57206-89-0	6486-23-3
Physicochemical Properties
State of the substance at 20° C and 101,3 kPa	Yellow solid	Yellow solid
Melting/freezing point	236 °C; decomp. 253 °C	255 °C; decomp. 256 °C
Relative density	1.4262 g/cm^3at 27°C	1.5640 g/mL at 23 °C
Vapour pressure	<0.001 Pa at 20°C	<0.000001 Pa (EPIWin estimate in agreement with "column 2")
Water solubility	9.3 µg/L at 23°C	7.5 μg/L at 24-25 °C
pH value of an aqueous suspension	6.8	7.5
Partition coefficient n-octanol/water	3.67	2.9
Flammability	No ignition (BZ 1)	non-flammable (BZ 2)
Explosive properties	not explosive	not explosive
Self-ignition temperature	No self-ignition (neat substance), 260 °C (1:1 mixt. with kieselguhr)	no self-ignition (neat substance), 260 °C (1:1 mixt. with kieselguhr)
Oxidizing properties (Ox reduction potential)	not oxidizing (Method A.17)	not oxidising (UN-Test O.1)
Stability in organic solvents and identity of relevant de-gradation products	No data	>72 h in DMSO and in 1,2-propylene glycol
Solubility in org. solvents: octanol solubility	43.7 mg/L at 23°C	5.96 mg/L at 25-26 °C
Mammalian Toxicity
skin irritation	RA: not irritating	not irritating
eye irritation	RA: not irritating	not irritating
Skin sensitisation	not sensitising	not sensitising
In vitrogene mutation study in bacteria	not mutagenic (Prival modif.)	not mutagenic (Prival modif.)
Acute toxicity, oral route	RA: LD50 rat: >2000 mg/kg bw	LD50 rat (f) = 8285 mg/kg bw
Ecotoxicology
Short-term toxicity testing on Daphnia	RA:EC50> 100 mg/L	EC50> 100 mg/L

 

Justification for selection of skin irritation / corrosion endpoint:
most up to date and most reliable study available

Justification for selection of eye irritation endpoint:
most up to date and most reliable study available

Justification for classification or non-classification

After treatment with the test item (source substance PY 3) all mean scores determined for skin and eye irritation were markedly below the threshold for classification. Furthermore no signs of corrosive properties were observed. Thus the substance subject to registration (target substance) does not meet criteria for classification according to REGULATION (EC) No 1272/2008.