2,4-di-tert-butylphenol

Endpoint summary

Description of key information

Acute toxicity oral: LD50 > 2000 mg/kg body weight
Acute toxicity dermal: LD50 > 5000 mg/kg bodyweight (non-guideline, read-across- 2,6 -DTBP)

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01/02/1991-07/03/1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline study (OECD 401)

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Manston, Kent, U.K.
- Age at study initiation: approximately five to eight weeks old
- Weight at study initiation: At the start of the main study the males weighed 141 - 167 g, and females 139 - 151 g
- Fasting period before study: overnight fast immediately before dosing and for approximately two hours after dosing
- Housing: the animals were housed in groups of five by sex in solid-floor polypropylene cages with sawdust bedding
- Diet (e.g. ad libitum): with the exception of an overnight fast immediately before dosing and for approximately two hours after dosing, food ad libitum (Rat and Mouse Expanded Diet No. 1, Special Diet Services Limited, Witham, Essex, UK)
- Water (e.g. ad libitum): with the exception of an overnight fast immediately before dosing and for approximately two hours after dosing, drinking water ad libitum
- Acclimation period: after minimum acclimatisation period of at least five days the animals selected at random and given a unique number within the study by indelible ink marking on the tail and a number written on a cage card


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-23°C
- Humidity (%): 42-55%
- Air changes (per hr): approximately 15 changes per hr
- Photoperiod (hrs dark / hrs light): 12 hrs dark / 12 hrs light

Route of administration:

oral: gavage

Vehicle:

arachis oil

Details on oral exposure:

VEHICLE
- Concentration in vehicle: range-finding study: 500, 200, 20 mg/ml. main study: 200 mg/ml
- Dose volume 10 ml/kg. The volume administered to each animal was calculated according to its fasted bodyweight at time of dosing.

MAXIMUM DOSE VOLUME APPLIED: 10 ml/kg

CLASS METHOD (if applicable)
- Rationale for the selection of the starting dose: A range-finding study was performed using pre-selected dose levels to determine the highest of these dose levels that caused no deaths

Doses:

Range-finding Study: 200, 2000 and 5000 mg/kg
Main Study: 2000 mg/kg

No. of animals per sex per dose:

Range-finding Study: 3
Main Study: 5

Control animals:

not specified

Details on study design:

- Duration of observation period following administration:
Range-finding study: five days
Main study: 14 days
- Frequency of observations and weighing:
Range-finding study: 1/2, 1, 2, and 4 hours after dosing and then daily for five days. Individual bodyweights were recorded on the day of dosing to allow calculation of individual treatment volumes.
Main study: 1/2, 1, 2 and 4 hours after dosing and subsequently once daily for 14 days. Individual bodyweights were recorded on the day of treatment (Day 0) and on Days 7 and 14
- Necropsy of survivors performed:
Range-finding study: no
Main study: yes, macroscopic observation

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Mortality:

Range-finding study: the female treated with 5000 mg/kg was found dead three days after treatment

Main study: no deaths

Clinical signs:

other: Main study: no signs of systemic toxicity were noted during the study

Gross pathology:

Main study: no abnormalities were noted at necropsy (killed day 14)

Individual clinical observations and mortality data in the range finding study

Dose level Mg/kg	Animal number & sex	Effects noted after dosing (hours)				Effects noted during period after dosing (days)
		1/2	1	2	4	1	2	3	4	5
5000	1-0 male	0	0	0	0	0	0	0	0	0
	2-0 female	0	0	0	0	0	LA	X
2000	1-1 male	0	0	0	0	0	0	0	0	0
	2-1 female	0	0	0	0	0	0	0	0	0
200	1-2 male	0	0	0	0	0	0	0	0	0
	2-2 female	0	0	0	0	0	0	0	0	0

Key:

L = lethargy

A = ataxia

X = animal dead

0 = no signs of systemic toxicity

Individual bodyweights and weekly bodyweight increases in the main study

Dose Level	Animal Number	Bodyweight (g) at Day			Increment (g) During Week
mg/kg	& Sex	0	7	14	1	2
2000	3 -0 Male	141	198	250	57	52
	3 -1 Male	167	216	275	49	59
	3 -2 Male	152	224	293	72	69
	3 -3 Male	144	214	267	70	53
2000	3 -4 Male	143	206	272	63	66
	4 -0 Female	151	192	220	41	28
	4 -1 Female	142	188	214	46	26
	4 -2 Female	140	178	206	38	28
	4 -3 Female	139	172	199	33	27
	4 - 4 female	139	185	212	46	27

Interpretation of results:

GHS criteria not met

Conclusions:

The acute oral median lethal dose (LD50) of the test material, DTBP, in the Sprague-Dawley strain rat was found to be greater than 2000 mg/kg bodyweight.

Executive summary:

A study was performed to assess the acute oral toxicity of the test material, DTBP, in the Sprague-Dawley strain rat. The method used followed that described in the OECD Guidelines for Testing of Chemicals (1981) No. 401 "Acute Oral Toxicity" referenced as Method B1 in Commission Directive 84/449/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

The results may be used as a basis for classification and labelling under annex VI of Council Directive 67/548/EEC (as adapted to technical progress by Commission Directive 83/467/EEC).

Following a range-finding study, a group of ten fasted animals (five males and five females) was given a single oral dose of test material, as a suspension in arachis oil B.P. at a dose level of 2000 mg/kg bodyweight. The animals were observed for fourteen days after the day of dosing and were killed for gross pathological examination.

There were no deaths. No signs of systemic toxicity were noted during the study.

All animals showed expected gain in bodyweight during the study. No abnormalities were noted at necropsy.

The acute oral median lethal dose (LD50) of the test material, DTBP, in the Sprague-Dawley strain rat was found to be greater than 2000 mg/kg bodyweight. No symbol and risk phrases are required according to EEC labeling regulations.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

Sufficient to address requirements.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
2,4-DTBP which is structurally similar to 2,6-DTBP

Reason / purpose for cross-reference:

read-across source

Preliminary study:

The rats had no local injuries and showed no signs of systemic illness following dermal exposure.

Key result

Sex:

not specified

Dose descriptor:

LD0

Effect level:

10 mL/kg bw

Based on:

other: technical containing 70-80% 2,6-di-tert-butylphenol

Mortality:

None

Clinical signs:

other: No data

Gross pathology:

No data

Interpretation of results:

GHS criteria not met

Conclusions:

Not classified for dermal toxicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

5 000 mg/kg bw

Quality of whole database:

Sufficient to address requirements.

Additional information

Acute toxicity oral:

The key study describing the oral toxicity of 2,4-DTBP in the Sprague-Dawley strain rat, resulted in a LD50 value greater than 2000 mg/kg bw (Tuffnell, PP 1991). Two further supporting studies in rats are available in which LD50 values of 3250 mg/kg bw and greater than 50 mg/kg bw (the only dose investigated) were determined (Mürmann P, 1983 and Mallory VT, 1985 respectively). Whilst Tuffnell reported no evidence of systemic toxicity in animals dosed up to 2000 mg/kg bw, Mürmann observed diarrhoea, ruffled fur, squatting position, diuresis, staggering, ataxia, abdominal position and sedation from 20 minutes post dosing at 1990, 2835 and 3570 mg/kg bw: In this study 1 male treated at 1990 mg/kg died; 2 males and 2 females treated at 2835 mg/kg died and 2 males and 4 females treated at 3570 mg/kg died. After 6 days the animals were free of signs of toxicity however, excessive loss of bodyweight was present in some animals treated at 2835 and 3570 mg/kg bw. In Mallory's study a single dose level of 50 mg/kg bw was investigated; no systemic effects were reported.

The findings from these studies confirm the low level of oral toxicity in the rat. No symbol and risk phrases are required according to EEC labelling regulations.

Key study (Tuffnell, PP 1991):

The method used followed that described in the OECD Guidelines for Testing of Chemicals (1981) No. 401 "Acute Oral Toxicity" referenced as Method B1 in Commission Directive 84/449/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

The results may be used as a basis for classification and labelling under annex VI of Council Directive 67/548/EEC (as adapted to technical progress by Commission Directive 83/467/EEC).

Following a range-finding study, a group of ten fasted animals (five males and five females) was given a single oral dose of test material, as a suspension in arachis oil B. P. at a dose level of 2000 mg/kg bodyweight. The animals were observed for fourteen days after the day of dosing and were killed for gross pathological examination.

There were no deaths. No signs of systemic toxicity were noted during the study.

All animals showed expected gain in bodyweight during the study. No abnormalities were noted at necropsy.

Dermal toxicity:

2,4 -DTBP is structurally similar to 2,6 -DTBP and has a log Kow close in value to 2,6 -DTBP with slightly higher water solubility. These similarities support the use of read-across to 2,6 -DTBP studies in addition to 2,4 -DTBP data and it is considered scientifically un-necessary to conduct a dermal acute toxicity study.

Several studies were performed with 2,6-DTBP dating from 1955 to 1959. These studies were non-guideline and non-GLP but demonstrate that 2,6-di-tertbutylphenol is not toxic by dermal exposure and should not therefore be classified. Two studies were performed using rats and two studies using rabbits. No effects due to local injury or systemic illness were observed up to 33 g/kg bw. A value of 5000 mg/kg bw will be used in the risk assessment.

To further support the use of read-across to 2,6-DTBP, a non-guideline rabbit dermal toxicity study with 2,4-DTBP (Mallory, VT) in which rabbits were treated at 200 mg/kg for 24 hours with an occluded exposure is reported. Although slight to severe erythema, edema and necrosis were reported there were no deaths and the dermal LD50 was concluded to be greater than 200 mg/kg.

Justification for classification or non-classification

Acute toxicity oral:

In accordance with EU CLP (Regulation (EC) No. 1272/2008), classification is not required for acute oral toxicity based on the available data.

 

Acute toxicity dermal:

In accordance with EU CLP (Regulation (EC) No. 1272/2008), classification is not required for acute dermal toxicity based on the available data.