LBX98

Acute Toxicity: oral

Administrative data

Endpoint:

acute toxicity: oral

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Justification for type of information:

No data are available for the target substance. Acute oral LD50 values of 121mg/kg bw, 242 mg/kg bw and 207 mg/kg bw are reported for o-, m- and p-cresols, respectively. Acute oral LD50 values of ~980 mg/kg bw are reported for xylenol and ethylphenol. Data therefore demonstrate greater toxicity for the cresols compared to mixed xylenol isomers and mixed ethylphenol isomers, with some evidence that o-cresol is the more toxic of the cresol isomers. Based on the closest structural similarity, read-across using the xylenol study is required for this endpoint. No dermal toxicity data are available for any Category substance; a waiver is appropriate for the target substance for this endpoint based on the proposed classification of the target substance as corrosive. Robust inhalation toxicity data are available for any Category substance; a waiver is appropriate for the target substance for this endpoint based on the proposed classification of the target substance as corrosive. Experimental data for o-, m- and pcresols, 2,4-xylenol and 2,6-xylenol show that classification for skin corrosivity is appropriate. Data for 3,5-xylenol do not indicate that classification for skin irritation or corrosivity are required. Classification for skin corrosivity is therefore proposed for the target substance based on the weight of evidence and following a worst case approach. Experimental data for o-, m- and p-cresols and 3,5-xylenol show severe eye irritation. Classification for severe eye damage is therefore proposed for the target substance based on the weight of evidence. Skin sensitisation studies report negative results for p-cresol and 3,5-xylenol and a positive result for 2,4-xylenol. Classification for skin sensitisation is therefore proposed for the target substance based on the weight of evidence and following a worst-case approach.

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 425 (Acute Oral Toxicity: Up-and-Down Procedure)

Deviations:

yes

Principles of method if other than guideline:

Deviations: The dosage, postdosage and scheduled sacrifice periods were each extended for an additional 3 days. 30 rats were received at the testing facility rather than the 20 rats stated in the protocol. Rat 5389 in the 550 mg/kg/day dosage group was given 3 h and 4 h observations at 4 h 39 minsand 4 h 46 mins, respectively. These deviations are not considered to adversely affect the study integrity.

GLP compliance:

yes

Remarks:

Quality assurance statement only.

Test type:

up-and-down procedure

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Reaction mass of 2,4-xylenol and 2,5-xylenol

EC Number:

905-287-4

Cas Number:

1638758-52-7

Molecular formula:

(CH3)2C6H3OH

IUPAC Name:

Reaction mass of 2,4-xylenol and 2,5-xylenol

Test material form:

solid: bulk

Test animals

Species:

rat

Strain:

other: Crl:CD(SD)IGS BR VAF/Plus

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS- Source: Charles River Laboratories, Inc., Portage, Michigan, USA- Age at study initiation: 63 days (at arrival)- Weight at study initiation: 197 - 223 g (the day after arrival)- Fasting period before study: Fasted on the night before the dosage administration, with feed returned to the animals following the 4 h clinical observation.- Housing: Individually housed in stainless-steel wire-bottomed cages.- Diet (e.g. ad libitum): Certified Rodent Diet #5002 (PMI Nutrition International, Inc., St. Louis, Missouri, USA).- Water (e.g. ad libitum): Local water, passed through a reverse osmosis membrane, available ad libitum, via individual water bottles. Chlorine was added to the processed water as a bacteriostat.ENVIRONMENTAL CONDITIONS- Temperature (°C): 64 - 79°F (18 - 26°C)- Humidity (%): 30 - 70%- Air changes (per hr): Positive airflow, minimum of 10 changes per hour of HEPA filtered air. - Photoperiod (hrs dark / hrs light): 12 h dark / 12 h lightIN-LIFE DATES: From: 15 March 2004 To: 11 April 2004

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

VEHICLE- Concentration in vehicle: 35 mg/mL vehicle, 110 mg/mL vehicle and 350 mg/mL vehicle- Amount of vehicle (if gavage): 5 mL/kg- Justification for choice of vehicle: Not stated, guideline vehicle substance.- Lot/batch no. (if required): 062K0006- Purity: Not stated

Doses:

175, 550 and 1750 mg/kg/day

No. of animals per sex per dose:

All females, 1 rat for 175 mg/kg/day, 4 rats for 550 mg/kg/day, 4 rats for 1750 mg/kg/day,

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days- Frequency of observations and weighing: Pre-dose, at least once in the 30 mins after dosage, approx. hourly intervals for the first 4 h and then daily thereafter for observations. Body weights were recorded weekly during acclimation, daily during the dosing and observation period and at sacrifice. - Necropsy of survivors performed: yes- Other examinations performed: clinical signs, body weight, feed consumption

Results and discussion

Effect levels

Effect levels 1

Sex:

female

Dose descriptor:

LD50

Effect level:

980.62 other: mg/kg

Remarks on result:

other: Calculated from log10 values.

Effect levels 2

Sex:

male/female

Dose descriptor:

other: NOEL

Effect level:

ca. 175 mg/kg bw

Based on:

other: Adverse clinical signs at 550 mg/kg bw

Mortality:

3 rats died in the 1750 mg/kg dose group from treatment related effects.

Clinical signs:

Clinical observations which were determined to be dose related included: lacrimation, excess salivation and urine stained fur in both the 550 and 1750 mg/kg dose groups. Decreased motor activity, twitches, prostrate, ptosis, limited use of hindlimbs, lost proprioceptive positioning, no use of both hind and forelimbs, ataxia, lost righting reflex, tachypnea, impaired righting reflex and scant faeces were observed in the 1750 mg/kg dose group.

Body weight:

Body weight changes were reduced in the 550 and 1750 mg/kg dose groups compared to the rat in the 175 mg/kg dose group. However, all surviving rats gained weight after dose administration.

Gross pathology:

Necropsy confirmed the clinical observations. No gross lesions were found.

Other findings:

Feed consumption values, both absolute (g/day) and relative (g/kg/day) showed a dose dependent reduction in the day after dosing in the 550 and 1750 mg/kg dose groups. This trend continued until day 5 post dosing, after which the values remaind comparative to the 175 mg/kg dosed animal.

Any other information on results incl. tables

Three rats in the 1750 mg/kg/day dose group were found dead during the study. Eight of the nine test animals showed dose related effects. There were no deaths in the 175 and 550 mg/kg/day dose groups. Clinical observations which were determined to be dose related included: lacrimation, excess salivation and urine stained fur in both the 550 and 1750 mg/kg dose groups. Decreased motor activity, twitches, prostrate, ptosis, limited use of hindlimbs, lost proprioceptive positioning, no use of both hind and forelimbs, ataxia, lost righting reflex, tachypnea, impaired righting reflex and scant faeces were observed in the 1750 mg/kg dose group. Necropsy confirmed the clinical observations. No gross lesions were found.

Body weight changes were reduced in the 550 and 1750 mg/kg dose groups compared to the rat in the 175 mg/kg dose group. However, all surviving rats gained weight after dose administration. Feed consumption values, both absolute (g/day) and relative (g/kg/day) showed a dose dependent reduction in the day after dosing in the 550 and 1750 mg/kg dose groups. This trend continued until day 5 post dosing, after which the values remaind comparative to the 175 mg/kg dosed animal.

Table 1: Mortality results of the up and down procedure with ethyl phenols

Step	Dose (mg/kg)	Response	Include	Log10 dose
1	175	O	No	-
2	550	O	Yes	2.740
3	1750	X	Yes	3.243
4	550	O	Yes	2.740
5	1750	X	Yes	3.243
6	550	O	Yes	2.740
7	1750	X	Yes	3.243
8	550	O	No	-
9	1750	O	No	-
Total				17.949

O = alive, X = dead
Sum of log10 doses/# of eligible rats: 17.949/6 = 2.9915, antilog of 2.9915 = 980.62 mg/kg = LD50

Table 2: Summary of observations of adverse effects during study

Observation	175 mg/kg	550 mg/kg	1750 mg/kg
Death	0	0	3
Lacrimation	0/0	1/1	4/4
Decreased motor activity	0/0	0/0	4/4
Twitches	0/0	0/0	3/3
Prostrate	0/0	0/0	3/3
Excess salivation	0/0	1/1	2/2
Ptosis	0/0	0/0	2/2
Limited use of hindlimbs	0/0	0/0	2/2
Lost proprioceptive positioning	0/0	0/0	2/2
No use of both hind and forelimbs	0/0	0/0	2/2
Ataxia	0/0	0/0	2/2
Lost righting reflex	0/0	0/0	2/2
Tachypnea	0/0	0/0	2/2
Urine stained abdominal fur	0/0	4/2	5/1
Impaired righting reflex	0/0	0/0	1/1
Scant faeces	0/0	0/0	1/1
Clear perinasal substance	0/0	1/1	0/0
Chromorhinorrhea	0/0	1/1	0/0
Maximum possible incidence	14/1	56/4	17/4

Maximum possible incidence = (days x rats)/number of rats examined per group
N/N = total number of observations/number of rats with observation

 

 

Table 3: Summary of body weight data

Rat body weight (g)	175 mg/kg	550 mg/kg	1750 mg/kg^a
Day 1	203 ± 0.0	216.0 ± 14.4	225.8 ± 14.9
Day 2	219.0 ± 0.0	223.5 ± 22.7	229.0 ± 0.0
Day 3	216.0 ± 0.0	234.2 ± 19.5	220.0 ± 0.0
Day 4	227.0 ± 0.0	235.0 ± 19.1	234.0 ± 0.0
Day 5	228.0 ± 0.0	240.0 ± 22.4	246.0 ± 0.0
Day 6	233.0 ± 0.0	236.2 ± 19.0	254.0 ± 0.0
Day 7	241.0 ± 0.0	239.8 ± 21.4	258.0 ± 0.0
Day 8	239.0 ± 0.0	243.0 ± 25.1	255.0 ± 0.0
Day 9	241.0 ± 0.0	247.5 ± 24.6	262.0 ± 0.0
Day 10	246.0 ± 0.0	248.0 ± 22.2	262.0 ± 0.0
Day 11	261.0 ± 0.0	250.0 ± 18.8	268.0 ± 0.0
Day 12	254.0 ± 0.0	251.0 ± 17.6	272.0 ± 0.0
Day 13	263.0 ± 0.0	249.8 ± 24.0	279.0 ± 0.0
Day 14	263.0 ± 0.0	252.5 ± 24.0	276.0 ± 0.0

Mean ± SD
^a= Excludes values for rats found dead.

 

Table 4: Summary of feed consumption data

Feed consumption (g/day)	175 mg/kg	550 mg/kg	1750 mg/kg^a
Day 1-2	17.0 ± 0.0	11.8 ± 3.9	1.0 ± 0.0
Day 2-3	17.0 ± 0.0	19.8 ± 3.5	1.0 ± 0.0
Day 3-4	17.0 ± 0.0	18.5 ± 5.4	12.0 ± 0.0
Day 4-5	18.0 ± 0.0	17.7 ± 1.2	17.0 ± 0.0
Day 5-6	17.0 ± 0.0	18.0 ± 5.0	20.0 ± 0.0
Day 6-7	20.0 ± 0.0	20.5 ± 1.7	24.0 ± 0.0
Day 7-8	19.0 ± 0.0	19.2 ± 5.1	22.0 ± 0.0
Day 8-9	22.0 ± 0.0	19.2 ± 4.4	22.0 ± 0.0
Day 9-10	17.0 ± 0.0	21.5 ± 1.3	26.0 ± 0.0
Day 10-11	24.0 ± 0.0	19.0 ± 1.6	24.0 ± 0.0
Day 11-12	16.0 ± 0.0	20.5 ± 3.3	24.0 ± 0.0
Day 12-13	17.0 ± 0.0	18.5 ± 3.1	25.0 ± 0.0
Day 13-14	20.0 ± 0.0	18.2 ± 3.3	21.0 ± 0.0
Day 1-14	18.5 ± 0.0	18.7 ± 2.2	18.4 ± 0.0

Mean ± SD
^a= Excludes values for rats found dead.

Applicant's summary and conclusion

Executive summary:

Based on this study, the LD50 for ethyl phenols was determined to be 980.62 mg/kg. Mortality occurred in three of the four rats given the highest dose of 1750 mg/kg. Adverse clinical signs were observed at doses of 550 and 1750 mg/kg. A single dose of 175 mg/kg had no observable effect during the study.

The above results are suitable to be used for read across for Reaction mass of 2,4-xylenol and 2,5-xylenol, due to the category being based on structural similarity and comparable physicochemical properties, leading to similar (eco)toxicological properties.