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Description of key information

The oral LD50 value of Tributyl(ethyl) phosphonium diethylphosphate was established to be within the range of 50-300 mg/kg bw. According to the OECD 423 test guideline, the LD50 cut-off value was considered to be 300 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:
experimental study
Adequacy of study:
key study
Study period:
From 31 December 2018 to 24 February 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)
Version / remarks:
2001
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)
Version / remarks:
2008, inlcuding most recent amendments
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.1100 (Acute Oral Toxicity)
Version / remarks:
2002
Deviations:
no
Qualifier:
according to
Guideline:
other: Japanese Ministry of Agriculture, Forestry and Fisheries (JMAFF), 12 Nousan, Notification No 8147, November 2000, including the most recent partial revisions.
Version / remarks:
2000
Deviations:
no
GLP compliance:
yes
Test type:
acute toxic class method
Limit test:
no
Species:
rat
Strain:
other: Crl:WI (Han)
Sex:
female
Details on test animals and environmental conditions:
- Source: Charles River Deutschland, Sulzfeld, Germany.
- Females nulliparous and non-pregnant: yes
- Age at study initiation: Young adult animals (approx. 8-10 weeks old)
- Weight at study initiation: Body weight variation was within +/- 20% of the sex mean (160 - 197 grams).
- Fasting period before study: Animals were deprived of food overnight (for a maximum of 20 hours) prior to dosing and until 3-4 hours after administration of the test item. Water was available.
- Housing: Group housing of 3 animals per cage in labeled Makrolon cages containing sterilized sawdust as bedding material and paper as cage-enrichment.
- Diet: Free access to pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany).
- Water: Free access to tap water.
- Acclimation period: At least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Environmental controls for the animal room were set to maintain 18 to 24°C. The actual daily mean temperature during the study was 20 to 21°C.
- Humidity (%): relative target humidity of 40 to 70% (actual daily humidity was 36 to 53%). Deviations from the minimum level of target humidity occurred on three days during the study (lowest value was 36%). This study plan deviation is considered not to have affected the integrity of the study because it did not noticeably affect the clinical condition of the animals or the outcome of the study.
- Air changes (per hr): approx 10 air changes per hour with 100% fresh air (no air recirculation)
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 31 December 2018 to 24 February 2019
Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
GAVAGE METHOD: A single dose of test item was administered to the animals by oral gavage on Day 1, using a syringe with a plastic gavage cannula attached.

VEHICLE: Not applicable. The test item was administered as received.

CLASS METHOD
- Rationale for the selection of the starting dose: In the absence of relevant data on acute toxicity, a starting dose of 2000 mg/kg bw was selected.
Doses:
50 mg/kg bw
300 mg/kg bw
2000 mg/kg bw
No. of animals per sex per dose:
50 mg/kg bw: 6 (2 groups of three females in a stepwise manner)
300 mg/kg bw: 6 (2 groups of three females in a stepwise manner)
2000 mg/kg bw: 3
Control animals:
no
Details on study design:
Duration of observation period following administration: 14 days

Frequency of observations and weighing:
- Mortality/Viability: Twice daily. The time of death was recorded as precisely as possible.
- Body weights: Days 1 (pre-administration), 8 and 15.
- Clinical signs: Postdose observations were performed at periodic intervals on the day of dosing (at least three times) and once daily thereafter. The observation period was 14 days.

Necropsy of survivors performed: The animals surviving to the end of the observation period were sacrificed by oxygen/carbon dioxide procedure. All animals assigned to the study were subjected to necropsy and descriptions of all internal macroscopic abnormalities recorded.

Other examinations performed: none.
Statistics:
No statistical analysis was performed (The method used is not intended to allow the calculation of a precise LD50 value).
Key result
Sex:
female
Dose descriptor:
LD50 cut-off
Effect level:
300 mg/kg bw
Based on:
test mat.
Mortality:
At 2000 mg/kg bw: all animals were found dead on day 1.
At 300 mg/kg bw: no mortality occurred in the first dose group and all animals were found dead on Day 1 for the second dose group.
At 50 mg/kg bw: no mortality occurred
Clinical signs:
At 2000 mg/kg bw, clonic spasms and salivation were seen prior to the death of the animals.
At 300 mg/kg, for the first dose group, hunched posture, uncoordinated movements, piloerection and/or salivation were noted on Day 1. At 300 mg/kg, for the second dose group, lethargy, clonic spasms, flat and/or hunched posture, quick or slow breathing, piloerection, exophthalmos (both eyes), salivation and/or ptosis were seen prior to the death of the animals.
At 50 mg/kg, hunched posture and salivation were noted on Day 1.
Body weight:
The mean body weight gain shown by the surviving animals over the study period was considered to be similar to that expected for normal untreated animals of the same age and strain.
Gross pathology:
Abnormalities of the eyes (gray-white, cloudy, left side) and/or stomach (several red-brown foci glandular mucosa) were found in the animals treated at 2000 mg/kg that died during the study. Macroscopic post mortem examination of the other animals (300 mg/kg) that died during the study did not reveal any abnormalities.
No test item related abnormalities were found at macroscopic post mortem examination of the surviving animals. The several reddish foci on the thymus of one animal treated at 50 mg/kg is occasionally seen in rats of this age and strain and was therefore considered not related to treatment.
Interpretation of results:
Category 3 based on GHS criteria
Conclusions:
In an acute oral toxicity study with rats, performed according to OECD/EC test guidelines, an oral LD50 value of Tributyl(ethyl) phosphonium diethylphosphate was established to be within the range of 50-300 mg/kg bw. According to the OECD 423 test guideline, the LD50 cut-off value was considered to be 300 mg/kg bw.
Executive summary:

An assessment of acute oral toxicity with Tributyl(ethyl) phosphonium diethylphosphate in rats (Acute Toxic Class Method) was performed according to OECD guideline 423 and in accordance with GLP principles. Initially, Tributyl(ethyl) phosphonium diethylphosphate was administered by oral gavage to three female Wistar rats at 2000 mg/kg bw. In a stepwise procedure four additional groups of three females were dosed; two groups at 300 mg/kg bw and two groups at 50 mg/kg body weight. All animals were subjected to daily observations and weekly determination of body weight. Macroscopic examination was performed on the day of death or after terminal sacrifice (Day 15).

At 2000 mg/kg, all animals were found dead on Day 1. At 300 mg/kg, no mortality occurred in the first dose group and all animals were found dead on Day 1 for the second dose group. At 50 mg/kg, no mortality occurred. At 2000 mg/kg bw, clonic spasms and salivation were seen prior to the death of the animals. At 300 mg/kg, for the first dose group, hunched posture, uncoordinated movements, piloerection and/or salivation were noted on Day 1. At 300 mg/kg, for the second dose group, lethargy, clonic spasms, flat and/or hunched posture, quick or slow breathing, piloerection, exophthalmos (both eyes), salivation and/or ptosis were seen prior to the death of the animals. At 50 mg/kg, hunched posture and salivation were noted on Day 1. The mean body weight gain shown by the surviving animals over the study period was considered to be similar to that

expected for normal untreated animals of the same age and strain. Abnormalities of the eyes (gray-white, cloudy, left side) and/or stomach (several red-brown foci glandular mucosa) were found in the animals treated

at 2000 mg/kg that died during the study. Macroscopic post mortem examination of the other animals (300 mg/kg) that died during the study did not reveal any abnormalities. No test item related abnormalities were found at macroscopic post mortem examination of the surviving animals.

The oral LD50 value of Tributyl(ethyl) phosphonium diethylphosphate in Wistar rats was established to be within the range of 50 -300 mg/kg bw. According to the OECD 423 test guideline, the LD50 cut-off value was considered to be 300 mg/kg bw.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
Value:
300 mg/kg bw
Quality of whole database:
GLP study according to standard guidelines.

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

Justification for classification or non-classification

The oral LD50 value of the test substance in Wistar rats was established to be within the range of 50 -300 mg/kg body weight and therefore the substance should be classified as toxic if swallowed (Acute Oral Tox 3, H301) according tho the CLP and the UN GHS. oxicity according to the EC/1272/2008 CLP criteria.