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

Endpoint summary

Description of key information

Read across prediction for the target substance LD50: >2000 mg/kg bw
LD50 value of the source substance (PY 3): 8285 mg/kg bw

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1971

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Reliability of the original study (GLP compliant guideline study) as such was 2 (Basic data given, comparable to guideline). Additional downgrading owed to application of read across is considered to be redundant.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

no

Remarks:

study was performed previous to GLP implementation

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: in house breeding, SPF rats
- Weight at study initiation: mean: 104 g (84-118g)
- Fasting period before study: yes, 16 hours
- Diet: Standard ALTROMIN R (Altromin GmbH, Lage/Lippe, Germany)
- Water: tap water

Route of administration:

oral: gavage

Vehicle:

other: sesame oil

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 12.5%

- the highest concentration (15000 mg/kg bw) was applied in two portions à 7500 mg/kg bw within one hour

Doses:

4000, 6300, 10000, 15000 mg/kg bw

No. of animals per sex per dose:

10 females

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 7 days
- Frequency of observations and weighing: no data
- Necropsy of survivors performed: no data, but necropsy of animals which died

Sex:

female

Dose descriptor:

LD50

Effect level:

8 285 mg/kg bw

Based on:

test mat.

Mortality:

4000 mg/kg bw: 0/10
6300 mg/kg bw: 1/10
10000 mg/kg bw: 9/10
15000 mg/kg bw: 10/10

the animals died within 1.5 and 24 hours after application

Clinical signs:

other: clinical signs of animals which died: - imbalance, accelerated respiration, prone position, paralysis of the limbs - the pigment was excreted via faeces

Gross pathology:

- no macroscopic anomalies in the animals

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Single application of the test item to Wistar rats by gavage resulted in an LD50 of 8252 mg/kg bw. The test item has not to be classified for acute oral toxicity.

Executive summary:

Acute toxicity of the test item has been investigated in female SPF-Wistar rats (10 animals per dose group). The animals received 4000, 6300, 10000 or 15000 mg test item / kg bw by gavage (12.5% suspension in sesame oil). The post observation period was 7 days. The mortality was 0/10, 1/10, 9/10 and 10/10 in the 4000, 6300, 10000 or 15000 mg / kg bw dose group. The LD50 was calculated to be 8252 mg/kg bw. Animals which died showed imbalance, accelerated respiration, prone position and paralysis of the limbs. No pathologic findings were observed at necropsy.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Quality of whole database:

adequate reliability
Read across prediction LD50: >2000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

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 acute toxicity – oral endpoint
most up to date and most reliable study available

Justification for classification or non-classification

The predicted oral LD50 value of >2000 mg/kg bw (RA prediction for the target substance from the source substance PY 3) exceeds the threshold for classification. Thus the substance subject to registration does not meet criteria for classification according to REGULATION (EC) No 1272/2008.