Ethylene bis(3-mercaptopropionate)

Endpoint summary

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:

03 May 2022 - 18 May 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Version / remarks:

17 December 2001

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)

Version / remarks:

30 May 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1100 (Acute Oral Toxicity)

Version / remarks:

2002

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Toxi-Coop Zrt., H-1122 Budapest, Magyar Jakobinusok tere 4B
- Females nulliparous and non-pregnant: yes
- Age at study initiation: approx. 8-9 weeks old
- Weight at study initiation: 178-193 g. The maximum difference of individual animal weights from the mean of the treatment group did not exceed 20%.
- Fasting period before study: yes, over night
- Housing: 3 animals/cage
- Diet (e.g. ad libitum): standard laboratory rat diet, ad libitum (SM Rat/Mouse, Breeding & Maintenance, ssniff Spezialdiäten GmbH (D-59494 Soest, Germany))
- Water (e.g. ad libitum): ap water from the municipal supply, ad libitum
- Acclimation period: At least 13 days
- Microbiological status when known: SPF


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 – 25 °C (target: 22 ± 3 °C)
- Humidity (%): 31 – 71 % (target: 30 – 70 %)
- Air changes (per hr): 15-20
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

propylene glycol

Details on oral exposure:

MAXIMUM DOSE VOLUME APPLIED: 10 mL/kg bw.


CLASS METHOD
- Rationale for the selection of the starting dose:
According to the guideline, the starting dose level should be that which is most likely to produce mortality in some of the dosed animals. As starting dose level for acute toxicity study, a dose of 300 mg/kg body weight (bw) was selected based on the information, provided by the Supplier, which indicate that the LD50 value of the test item is between 50 and 300 mg/kg bw.

Doses:

300, 2000 mg/kg bw

No. of animals per sex per dose:

3 females/group

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations: at least once during the first 30 minutes, at 1, 2, 3, 4 and 6 hours after the treatment and once daily for 14 consecutive days thereafter
- Frequency of weighing: days 0 (prior to dosing), 7 and 14 (prior to necropsy), terminal body weight of animals found dead was also recorded
- Necropsy of survivors performed: yes

Key result

Sex:

female

Dose descriptor:

LD50 cut-off

Effect level:

500 mg/kg bw

Based on:

test mat.

Mortality:

At the dose level of 2000 mg/kg bw, 2/3 animals were found dead on Day 0 and 1/3 on Day 1.
At the dose level of 300 mg/kg bw, one animal (out of 6) was found dead on Day 6, five animals survived.

Clinical signs:

other: 300 mg/kg bw: decreased activity, hunched back and irritability; 2000 mg/kg bw: Tonic convulsions with vocalization, decreased activity and prone position, hunched back, piloerection and continuous tremors

Gross pathology:

300 mg/kg bw
At the dose level of 300 mg/kg bw, one animal (out of 6; No. 1425) was found dead on Day 6. Dark red discoloration of the glandular mucosa of the stomach, duodenum, ileum and jejunum, furthermore red discoloration of the non-collapsed lungs could be observed in this animal.
One out of five surviving animals (No.: 1426) showed small, pale, diffuse mottled
discoloration liver in all lobes.
In the other 4 surviving animals, no macroscopic changes were observed.

2000 mg/kg bw
In the 2000 mg/kg bw group, two animals were found dead on Day 0 (No. 1430 and 1432) and one animal (No. 1423) was found dead on Day 1. In the stomach a mixture of clear liquid material and bedding was observed in all animals. Purple discoloration of stomach glandular mucosa was noted in two animals (No.: 1430, 1432) and purple discoloration of duodenum was observed in one animal (No.: 1432).
In addition, red/dark red discoloration of the non-collapsed lungs was noted in all animals.

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

Under the conditions of this study, the acute oral LD50 value of GDMP was found to be 300 < LD50 ≤ 2000 mg/kg bw in female Han:WIST rats.
According to the GHS criteria, the test item can be ranked as Category 4 for acute
oral exposure. The LD50 cut-off value is 500 mg/kg bw.

Executive summary:

A single dose oral treatment was performed with GDMP according to the acute toxic class method (OECD 423 and Commission Regulation (EC) No 440/2008 of 30 May 2008, B.1.tris) in Han:WIST rats.
Three groups of three female rats each were treated with the test item at a dose level of 300 (Groups 1 and Group 2) or 2000 (Groups 3) mg/kg body weight (bw). The treatment was carried out by gavage for each animal after an overnight food withdrawal. Food was made available again 3 hours after the treatment. The test item was administered in Polyethylene glycol 400 (PEG 400), at a concentration of 30 or 200 mg/mL and at a dose volume of 10 mL/kg bw.
Initially a group of three animals were treated at the starting dose level of 300 mg/kg bw (Group 1). As no mortality observed after approximately 24 hours, three further animals were treated at the same dose level (Group 2). There were no serious effects noted, therefore a third group of animals was treated at the dose level of 2000 mg/kg bw, which caused the death of 3/3 animals (Group 3). On the 6th day following the treatment, 1/3 animals died from the first dose group (300 mg/kg bw). No further animals were treated according to the study design of OECD 423.
Clinical observations were performed at least once during the first 30 minutes, 1, 2, 3, 4 and 6 hours after dosing and daily for 14 days thereafter, where possible. Body weight was measured on day 0 (prior to dosing), 7 and 14 (prior to necropsy), where possible. All animals were subjected to a necropsy and a macroscopic examination.

Mortality
At the dose level of 2000 mg/kg bw, 2/3 animals were found dead on Day 0 and 1/3 on Day 1.
At the dose level of 300 mg/kg bw, one animal (out of 6) was found dead on Day 6, five animals survived.

 

Clinical observations
300 mg/kg bw
Treatment at the dose level of 300 mg/kg bw caused clinical symptoms such as slight decreased activity (4/6; No. 1425, 1437, 1443, 1426), hunched back (4/6; No. 1425, 1437, 1443, 1426) and irritability (1/6; No. 1426) on the day of treatment. One animal (No. 1425) showed slight decreased activity with hunched back on Day 1 and moderate decreased activity, intermittent tremors, hunched back on Day 2. From three days
after the treatment moderate decreased activity, hunched back and piloerection could be  observed until Day 5. The animal was found dead on Day 6. Five out of six animals were symptom free as of Day 1 until the end of the observation period.

2000 mg/kg bw
Tonic convulsions with vocalization were observed twenty minutes after the treatment followed by moderate decreased activity and prone position at thirty minutes after the treatment in two out of three animals (No. 1430, 1432) at the dose level of 2000 mg/kg bw.
The animals were found dead at 1 hour after treatment.
In one animal (No. 1423) moderate decreased activity, hunched back, piloerection and continuous tremors were observed on the day of treatment. The animal was found dead on Day 1.

 

Body weight
There was no evidence of effects on body weight or body weight gain that could be attributed to treatment with the test item in the surviving animals.

Necropsy
300 mg/kg bw
At the dose level of 300 mg/kg bw, one animal (out of 6; No. 1425) was found dead on Day 6. Dark red discoloration of the glandular mucosa of the stomach, duodenum, ileum and jejunum, furthermore red discoloration of the non-collapsed lungs could be observed in this animal.
One out of five surviving animals (No.: 1426) showed small, pale, diffuse mottled discoloration liver in all lobes.
In the other 4 surviving animals, no macroscopic changes were observed.

2000 mg/kg bw
In the 2000 mg/kg bw group, two animals were found dead on Day 0 (No. 1430 and 1432) and one animal (No. 1423) was found dead on Day 1. In the stomach a mixture of clear liquid material and bedding was observed in all animals. Purple discoloration of stomach glandular mucosa was noted in two animals (No.: 1430, 1432) and purple discoloration of duodenum was observed in one animal (No.: 1432). In addition, red/dark red discoloration of the non-collapsed lungs was noted in all animals.

 

CONCLUSIONS
Under the conditions of this study, the acute oral LD50 value of the test item was found to be 300 < LD50 ≤ 2000 mg/kg bw in female Han:WIST rats. According to the GHS criteria, GDMP can be ranked as "Category 4" for acute oral exposure. The LD50 cut-off value is 500 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

500 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Preliminary remark:
Currently, do data on toxicokinetics/metabolism is available for this category. Based on structural features (e.g. sterical hindrance) it is however assumed, that ester cleavage would not be fast and complete, especially since the substances contain up to 6 ester functions, which are in addition sterically shielded. Therefore, it seems more reasonable to base the category hypothesis on structural similarity.
In addition, it is not clear yet, whether the strength of the effects vary in a predictable manner, or if no relevant variations occur. However, there are variations in structure (number of ester bonds and consequently number of free -SH groups) and physicochemical properties (especially water solubility and log Kow). It is assumed that these variations will also be reflected by variations in effect levels. Therefore, scenario 4 is the working hypothesis for the time being.
More data points within the category are needed to further strengthen the category hypothesis (refer to Data matrix toxicity endpoints (systemic effects)). The scenario selection will be re-evaluated after the studies are finished.
This currently selected scenario covers the category approach for which the read-across hypothesis is based on structural similarity. For the REACH information requirement under consideration, the property investigated in studies conducted with different source substances is used to predict the property that would be observed in a study with the target substance if it were to be conducted. Similar properties are observed for the different source substances; this may include absence of effects for every member of the category.
There are expected to be differences in strength of the effects forming a regular pattern. The prediction will be based on a worst-case approach. The read-across is a category approach based on the hypothesis that the substances in this category share structural similarities with common functional groups. This approach serves to use existing data on acute toxicity, repeated-dose toxicity, and reproductive toxicity endpoints for substances in this category.
The hypothesis corresponds to Scenario 4 of the RAAF. The substances GDMP, TMPMP, PETMP, and Di-PETMP are esters of a common acid, 3-mercaptopropionic acid (3-MPA). The key functionality of the substances within this category is the presence of free SH-groups. It is hypothesised that the strength of effects correlates with the number of SH-groups. In addition, differences in bioavailability are expected to influence the strength of effects.
For details, please refer to the category document attached to Iuclid section 13.

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 1 640 mg/m³ air

Based on:

test mat.

Exp. duration:

4 h

Interpretation of results:

GHS criteria not met

Conclusions:

Based on read-across from PETMP, the 4 h LC50 of GDMP is estimated to be > 1640 mg/m³

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

> 1 640 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Quality of whole database:

not required since data on two other routes of exposure are available

Additional information

An acute oral toxicity study is available for GDMP. An acute inhalation toxicity study is availabel for PETMP. A justification for read-across is attached to Iuclid section 13.

 

Acute oral toxicity

A single dose oral treatment was performed with GDMP according to the acute toxic class method (OECD 423 and Commission Regulation (EC) No 440/2008 of 30 May 2008, B.1.tris) in Han:WIST rats.
Three groups of three female rats each were treated with the test item at a dose level of 300 (Groups 1 and Group 2) or 2000 (Groups 3) mg/kg body weight (bw). The treatment was carried out by gavage for each animal after an overnight food withdrawal. Food was made available again 3 hours after the treatment. The test item was administered in Polyethylene glycol 400 (PEG 400), at a concentration of 30 or 200 mg/mL and at a dose volume of 10 mL/kg bw.
Initially a group of three animals were treated at the starting dose level of 300 mg/kg bw (Group 1). As no mortality observed after approximately 24 hours, three further animals were treated at the same dose level (Group 2). There were no serious effects noted, therefore a third group of animals was treated at the dose level of 2000 mg/kg bw, which caused the death of 3/3 animals (Group 3). On the 6th day following the treatment, 1/3 animals died from the first dose group (300 mg/kg bw). No further animals were treated according to the study design of OECD 423.
Clinical observations were performed at least once during the first 30 minutes, 1, 2, 3, 4 and 6 hours after dosing and daily for 14 days thereafter, where possible. Body weight was measured on day 0 (prior to dosing), 7 and 14 (prior to necropsy), where possible. All animals were subjected to a necropsy and a macroscopic examination.

Mortality
At the dose level of 2000 mg/kg bw, 2/3 animals were found dead on Day 0 and 1/3 on Day 1.
At the dose level of 300 mg/kg bw, one animal (out of 6) was found dead on Day 6, five animals survived.

 

Clinical observations
300 mg/kg bw
Treatment at the dose level of 300 mg/kg bw caused clinical symptoms such as slight decreased activity (4/6; No. 1425, 1437, 1443, 1426), hunched back (4/6; No. 1425, 1437, 1443, 1426) and irritability (1/6; No. 1426) on the day of treatment. One animal (No. 1425) showed slight decreased activity with hunched back on Day 1 and moderate decreased activity, intermittent tremors, hunched back on Day 2. From three days
after the treatment moderate decreased activity, hunched back and piloerection could be  observed until Day 5. The animal was found dead on Day 6. Five out of six animals were symptom free as of Day 1 until the end of the observation period.

2000 mg/kg bw
Tonic convulsions with vocalization were observed twenty minutes after the treatment followed by moderate decreased activity and prone position at thirty minutes after the treatment in two out of three animals (No. 1430, 1432) at the dose level of 2000 mg/kg bw.
The animals were found dead at 1 hour after treatment.
In one animal (No. 1423) moderate decreased activity, hunched back, piloerection and continuous tremors were observed on the day of treatment. The animal was found dead on Day 1.

 

Body weight
There was no evidence of effects on body weight or body weight gain that could be attributed to treatment with the test item in the surviving animals.

Necropsy
300 mg/kg bw
At the dose level of 300 mg/kg bw, one animal (out of 6; No. 1425) was found dead on Day 6. Dark red discoloration of the glandular mucosa of the stomach, duodenum, ileum and jejunum, furthermore red discoloration of the non-collapsed lungs could be observed in this animal.
One out of five surviving animals (No.: 1426) showed small, pale, diffuse mottled discoloration liver in all lobes.
In the other 4 surviving animals, no macroscopic changes were observed.

2000 mg/kg bw
In the 2000 mg/kg bw group, two animals were found dead on Day 0 (No. 1430 and 1432) and one animal (No. 1423) was found dead on Day 1. In the stomach a mixture of clear liquid material and bedding was observed in all animals. Purple discoloration of stomach glandular mucosa was noted in two animals (No.: 1430, 1432) and purple discoloration of duodenum was observed in one animal (No.: 1432). In addition, red/dark red discoloration of the non-collapsed lungs was noted in all animals.

 

Under the conditions of this study, the acute oral LD50 value of the test item was found to be 300 < LD50 ≤ 2000 mg/kg bw in female Han:WIST rats. According to the GHS criteria, GDMP can be ranked as "Category 4" for acute oral exposure. The LD50 cut-off value is 500 mg/kg bw.

 

 

Acute inhalation toxicity

A study on the acute inhalation toxicity of PETMP on rats was conducted in accordance with OECD TG 403. Two groups of rats were nose-only exposed to actual liquid aerosol at concentrations of 1505 and 3363 mg/m³ air. Mortality did not occur up to the maximum technically attainable concentration. Clinical signs suggestive of respiratory tract irritation (laboured and irregular breathing patterns, bradypnea, muzzle area with red encrustations) occurred concentration-dependent and were essentially reversible within the first post-exposure week. The 4 h LC50 was >3363 mg/m³

 

After correction for molecular weight differences, the LC50 for GDMP is estimated to be >1640 mg/m³.

 

Justification for classification or non-classification

Based on teh availabel data, GDMP is assumed to be harmful if swallowed (LD50 =500 mg/kg bw, Acute Tox 4, H302) and non-toxic if inhaled (no mortality at highest attainable concentration).