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Description of key information

Acute oral toxicity

This study was conducted to assess the acute toxicity of the test article, MIT.HCl, following a single oral administration to a small number of rats. The study design provides information for hazard assessment and classification and enables a chemical to be assigned to toxicity classes but severely restricts animal usage.

 

Individual female rats were dosed sequentially at the following dose levels until one of the stopping criteria (as defined in OECD 425) was met: 175, 550, 175, 550, 175 and 55 mg/kg bw. The test article was dispersed in purified water and administered at a dose volume of 10 mL/kg. Surviving animals were killed on Day 15 and all animals subsequently underwent a full necropsy.

 

Both animals dosed at 550 mg/kg bw were killedin extremiswithin 1 to 4 hours of dosing. One animal dosed at 175 mg/kg bw was found dead on Day 2.

 

Principal signs of reaction to treatment were piloerection and dyspnoea. Less common signs were hunched posture, ataxia, hypothermia and tonic convulsions. These signs developed immediately after dosing and lasted up to 4 hours post dosing.

 

All surviving rats achieved body weight gains during the first and second weeks of the study.

 

No macroscopic changes were noted at necropsy, except for pale lungs, red and thick fundus region of the stomach, gelatinous appearance of the mucosal surface of the fundus region of the stomach and small caecum which were noted in the animal dosed at 550 mg/kg bw that was killed in extremis 4 hours after dosing. These macrosocpic changes are commonly observed following the oral administration of an unpalatable or slightly irritant test article, with regurgitation and aspiration into pulmonary system and in isolated are considered not to associated with systemic toxicity.

 

Under the conditions of this study the rat acute oral LD50 was 175 mg/kg bw in female rats. Therefore, according to Annex I for Regulation (EC) 1272/2008 MIT.HCl must be classified in Category 3. The signal word "Danger" and hazard statement H301 "Toxic if swallowed" is required.

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:
22 August 2017 to 3 October 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 425 (Acute Oral Toxicity: Up-and-Down Procedure)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test type:
up-and-down procedure
Limit test:
no
Specific details on test material used for the study:
- Identification: MIT.HCl (Methyl isothiazolinone hydrochloric acid)
- CAS no.: 26172-54-3
- Source and lot/batch No.of test material: Sigma-Aldrich / 10013913
- Expiration date of the lot/batch: 30 Nov 2018
- Purity test date: 23 Nov 2016
- Purity: >99.9%
- Apperance: White to light beige powder
- Moelcular weight: 151.61 g/mol
- Storage condition of test material: 2 to 8°C, protected from light


Species:
rat
Strain:
Wistar
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Ltd., Margate
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: 8 to 11 weeks
- Weight at study initiation: 178 to 197 g
- Fasting period before study: evening before dosing
- Housing: groups of up to five during the acclimatisation period. From the day prior to dosing (Day-1), each rat was individually housed in a similar cage
- Diet: ad libitum to 5LF2 EU Rodent Diet 14% except for a period of fasting from the evening of the day prior to dosing (Day-1) until approximately 3 hours after dosing
- Water: Municipal water, ad libitum
- Acclimation period: 8 to 27 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 45-65%
- Air changes (per hr): 15-20 air changes/h
- Photoperiod (hrs dark / hrs light): 12 hours light/dark

IN-LIFE DATES: From: 22 August 2017 to 3 October 2017
Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Doses were administered orally, by gavage, using plastic syringes and rubber catheters employing a dose volume of 10 mL/kg bw. Each rat was dosed once on Day 1, by passing the tip of a catheter along the oesophagus and instilling the test article into the gastric lumen.
Doses:
55, 175, 550 mg/kg bw
No. of animals per sex per dose:
55mg/kg bw: 1 animal
175 mg/kg bw: 3 animals
550 mg/kg bw: 2 animals
2000 mg/kg bw: 3 animals
Control animals:
no
Details on study design:
One animal was dosed first at a dose of 175 mg/kg bw. As the animal survived, the dose for the next animal was increased to 550 mg/kg bw based on a dose progression factor of 3.2, based on the recommendations of OECD 425. This stepped nature of the OECD 425 design provides for the first few doses to function as a self-adjusting sequence.

Statistics:
The median lethal dose level was determined by the maximum likelihood method using the Acute Oral Toxicity (OECD Test Guideline 425) Statistical Programme (AOT 425 StatPgm) version 1.0, 2001
Key result
Sex:
female
Dose descriptor:
LD50
Effect level:
ca. 175 mg/kg bw
Based on:
test mat.
Mortality:
Both animals dosed at 550 mg/kg bw were killed in extremis within 1 to 4 hours of dosing. One animal dosed at 175 mg/kg bw was found dead on Day 2.
Two of three animals dosed at 175 mg/kg bw and the animal dosed at 55 mg/kg bw survived.
Clinical signs:
No clinical signs were noted in the animal dosed at 55 mg/kg bw and in one animal dosed at 175 mg/kg bw.
Clinical signs noted in the other two animals dosed at 175 mg/kg bw were piloerection, decreased activity, hunched posture and ataxia. The clinical signs developed from one hour after dosing and were noted up to 4 hours after dosing.
Clinical signs noted in the two animals dosed at 550 mg/kg bw were piloerection, decreased activity, laboured breathing, semi-cold eyes, hypothermia, tonic convulsions and prone posture. One animal was killed in extremis 1 hour after dosing and the other animal was killed in extremis approximately 6.5 hours after dosing (refer to Table 7.2.1/01-1).
Body weight:
All surviving rats gained weight during the first and second weeks of the observation period.
Gross pathology:
Macroscopic changes noted at necropsy included pale lungs, red and thick fundus region of the stomach, gelatinous appearance of the mucosal surface of the fundus region of the stomach and small caecum which were limited to the animal dosed at 550 mg/kg bw that was killed in extremis 4 hours after dosing. These macroscopic changes are commonly observed following the oral administration of an unpalatable or slightly irritant test article, with regurgitation and aspiration into pulmonary system and in isolated are considered not to associated with systemic toxicity.
Other findings:
n/a

Table: 7.2.1/01-1: Results of acute oral toxicity study in rats dosed with MIT.HCl

Dose
(mg/kg bw)

Toxicological results *

Duration of signs

Time of death

LD50(mg/kg bw)
(14 days)

55

0/1/1

n/a

n/a

175 mg/kg bw

175

1/2/3

Piloerection: 4 h

Dyspnoea: 3 h

Hunched posture: 3 h

Ataxia: 2 h

Day 2

550

2/2/2

Piloerection: 6 h

Dyspnoea: 4 h

Prone posture / hypothermia / ptosis / tonic convulsion: immediately prior to death

1 h and 6.5 h post dosing

*     Number of animals which died/number of animals with clinical signs/number of animals used

 

Interpretation of results:
Category 3 based on GHS criteria
Conclusions:
Under the conditions of this study the rat acute oral LD50 was 175 mg/kg bw in female rats. Therefore, according to Annex I for Regulation (EC) 1272/2008 MIT.HCl must be classified in Category 3. The signal word "Danger" and hazard statement H301 "Toxic if swallowed" are required.
Executive summary:

This study was conducted to assess the acute toxicity of the test article, MIT.HCl, following a single oral administration to a small number of rats. The study design provides information for hazard assessment and classification and enables a chemical to be assigned to toxicity classes but severely restricts animal usage.

 

Individual female rats were dosed sequentially at the following dose levels until one of the stopping criteria (as defined in OECD 425) was met: 175, 550, 175, 550, 175 and 55 mg/kg bw. The test article was dispersed in purified water and administered at a dose volume of 10 mL/kg. Surviving animals were killed on Day 15 and all animals subsequently underwent a full necropsy.

 

Both animals dosed at 550 mg/kg bw were killedin extremiswithin 1 to 4 hours of dosing. One animal dosed at 175 mg/kg bw was found dead on Day 2.

 

Principal signs of reaction to treatment were piloerection and dyspnoea. Less common signs were hunched posture, ataxia, hypothermia and tonic convulsions. These signs developed immediately after dosing and lasted up to 4 hours post dosing.

 

All surviving rats achieved body weight gains during the first and second weeks of the study.

 

No macroscopic changes were noted at necropsy, except for pale lungs, red and thick fundus region of the stomach, gelatinous appearance of the mucosal surface of the fundus region of the stomach and small caecum which were noted in the animal dosed at 550 mg/kg bw that was killedin extremis4 hours after dosing. These macrosocpic changes are commonly observed following the oral administration of an unpalatable or slightly irritant test article, with regurgitation and aspiration into pulmonary system and in isolated are considered not to associated with systemic toxicity.

 

Under the conditions of this study the rat acute oral LD50 was 175 mg/kg bw in female rats. Therefore, according to Annex I for Regulation (EC) 1272/2008 MIT.HCl must be classified in Category 3. The signal word "Danger" and hazard statement H301 "Toxic if swallowed" are required.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
Value:
175 mg/kg bw
Quality of whole database:
Klimisch 1

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

Comparison with the CLP criteria

The acute oral LD50 in the rat of 175 mg/kg bw triggers classification according to Annex I for Regulation (EC) 1272/2008 MIT.HCl and must be classified in Category 3. The signal word "Danger" and hazard statement H301 "Toxic if swallowed" is required