2-(6-methoxybenzofuran-2-yl)-1,3-dimethyl-5-(methylsulphonyl)1H-benzimidazolium acetate

Endpoint summary

Description of key information

The acute oral LD50 and the acute inhalation LC50 of test item were considered to be >8000 mg/kg bw and > 2130 mg/m³, respectively.

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Rats: Tif: RAIf (SPF) strain.
- Weight at study initiation: ranged from 160 to 180 grams.
- Fasting period before study: the rats were starved during one night before starting the treatment.
- Housing: animals were housed in groups of 5 in Macroloncages (type 3).
- Diet: rat food - NAFAG, Gossau SG -, ad libitum.
- Water: ad libitum.
- Acclimation period: the animals were adapted to our laboratories for a minimum of 4 days.

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 1° C
- Relative humidity: 55 ± 5 %
- Photoperiod: 14 hours light cycle day.

Route of administration:

oral: gavage

Vehicle:

polyethylene glycol

Details on oral exposure:

Test item was suspended with polyethylene glycol (PEG 400). Before treatment the suspension was homogeneously dispersed with an Ultra-Turrax and during treatment it was kept stable with a magnetic stirrer.

Doses:

4640, 6000 and 7750 mg/kg bw

No. of animals per sex per dose:

5 males and 5 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days.
- Frequency of observations and weighing: physical condition and rate of deaths were monitored throughout the whole observation period.
- Necropsy of survivors performed: yes; surviving animals were submitted for necropsy whenever they died, survivors at the end of the observation period.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

ca. 7 700 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was observed at 4640 and 6000 mg/kg bw, while 3 females out of 5 died at the dose of 7750 mg/kg bw.

Clinical signs:

other: Within 2 hours after treatment the rats in all dosage groups showed sedation, dyspnoea, curved position and ruffled fur. The surviving animals recovered within 8 to 12 days.

Gross pathology:

No substance related gross organ changes were seen.

Dose mg/kg	Concentration % of formulation	No animals		Died within
				1 hr		24 hrs		48 hrs		7 days		14 days
		M	F	M	F	M	F	M	F	M	F	M	F
4640	30	5	5	0	0	0	0	0	0	0	0	0	0
6000	30	5	5	0	0	0	0	0	0	0	0	0	0
7750	30	5	5	0	0	0	3	0	3	0	3	0	3

Interpretation of results:

other: not classified, according to the CLP Regulation (EC) No 1272/2008

Conclusions:

LD50 (rat M/F): 7700 mg/kg

Executive summary:

Acute oral toxicity of the test substance was evaluated in a study conducted according to a methodology equivalent to OECD Guideline 401. Three groups each consisting of 5 males and 5 females were administered the test substance through oral route at the doses of 4640, 6000 and 7750 mg/kg bw. Within 2 hours after treatment the rats in all dosage groups showed sedation, dyspnoea, curved position and ruffled fur. The surviving animals had recovered within 8 to 12 days. No mortality was observed at 4640 and 6000 mg/kg bw, while 3 females out of 5 died at the dose of 7750 mg/kg bw. Surviving animals were killed and autopsied after an observation period of 14 days. No substance related gross organ changes were seen. Hence, based on the findings of the study, it can be concluded that the acute oral LD50 in rats of both sexes observed over a period of 14 days is approximately 7700 mg/kg bw.

Conclusion

LD50 (rat M/F): 7700 mg/kg

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

7 700 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

no

Test type:

traditional method

Limit test:

no

Species:

rat

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Rats: Tif: RAIf (SPF)
- Weight at study initiation: ranged from 170 to 185 grams.
- Housing: animals were segregated and kept in Macrolon cages, type 4 (10 animals to a cage).
- Diet: rat food - NAFAG, Gossau SG -, ad libitum.
- Water: ad libitum.
- Acclimation period: animals were adapted to our laboratoriesfor a minimum of 4 days.

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 1 °C
- Relative humidity: 55 ± 5 %
- Photoperiod: 10 hours light cycle day.

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Remark on MMAD/GSD:

Though MMAD/GSD were not determined, particle size distribution (> 40 % particles were of 1-3 µm, >30 % particles were of 0-1 µm for the concentration of 1505 mg/m³, while for the concentration of 2130 mg/m³, >70 % particles were of 0-1 µm size), indicated good respirability.

Details on inhalation exposure:

DUST PRODUCTION
The dust was generated by injecting the test material with the help of a "Grafix Exaktomat Injector" into an air stream which was discharged into the exposure chamber through a nozzle under a pressure of 2 atm. at a rate of 20 l/min. The concentration and the particle size distribution of the dust in the vicinity of the animals was monitored at 1 hour intervals throughout the dust exposure. The concentration was determined gravimetrically by sampling the test atmosphere through a selectron filter of 50 mm diameter and with a pore size of 0.2 µm (Schleicher and Schuell, Feldbach, Switzerland) at an air flow rate of 10 l/min. The size distribution of the dust particles was measured with a Cascade Impactor with selectron filters of 25 mm diameter and with a pore size of 0.2 µm (Schleicher and Schuell) at an air flow rate of 17.5 l/min.

TESTING PROCEDURE
For inhalation the rats were kept on separate PVC tubes positioned radially around the exposure chamber such that snout and nostrils of the animals only were exposed to the dust. The exposure was started 15 minutes after onset of the dust production, when the dust had reached an even dispersal throughout the chamber. During the exposure period the relative humidity inside thechamber was between 48 and 52 % RH. After a 4 hour inhalation the rats were returned to their cages. Physical condition and incidence of death were monitored throughout an observation period of 14 days.

Duration of exposure:

4 h

Concentrations:

1505 and 2130 mg/m³

No. of animals per sex per dose:

10 males and 10 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days.
- Physical condition and incidence of death were monitored throughout an observation period of 14 days.
- Necropsy of survivors performed: yes

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2 130 mg/m³ air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

not determinable due to absence of adverse toxic effects

Mortality:

No mortality occurred through out the observation period.

Clinical signs:

other: During the 4-hour exposure period and the following 14 observation days, no toxic symptoms were observed.

Gross pathology:

No substance related gross organ changes were seen.

Interpretation of results:

study cannot be used for classification

Conclusions:

LC50 (rat M/F) > 2130 mg/m³

Executive summary:

Acute inhalation toxicity of the test substance was evaluated in a study conducted according to a methodology described by Sachsse et al (1973). Two groups each consisting of 10 males and 10 females were exposed to the dust of the test substance at the concentrations of 1505 and 2130 mg/m³. Though MMAD/GSD were not determined, particle size distribution (>40 % particles were of 1-3 µm, >30 % particles were of 0-1 µm for the concentration of 1505 mg/m³, while for the concentration of 2130 mg/m³, >70 % particles were of 0-1 µm size), indicated good respirability. No mortality occurred through out the observation period. The animals were sacrificed and autopsied after an observation period of 14 days. No substance related gross organ changes were seen. Hence, based on the findings of the study, it can be concluded that the LC50 of the test substance in rats of both sexes observed over a period of 14 days is greater than 2130 mg/m³.

Conclusion

LC50 (rat M/F) > 2130 mg/m³

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

ACUTE TOXICITY BY ORAL ROUTE

Three studies are available for assessment of the acute oral toxicity potential of test item.

In the key study, acute oral toxicity potential of the test substance was evaluated in a study conducted according to testing method and procedures equivalent to OECD Guideline 401. Three groups each consisting of 5 males and 5 females were administered the test substance through oral route at the doses of 4640, 6000 and 7750 mg/kg bw. Within 2 hours after treatment the rats in all dosage groups showed sedation, dyspnoea, curved position and ruffled fur. The surviving animals had recovered within 8 to 12 days. No mortality was observed at 4640 and 6000 mg/kg bw, while 3 females out of 5 died at the dose of 7750 mg/kg bw. Surviving animals were killed and autopsied after an observation period of 14 days. No substance related gross organ changes were seen. Hence, based on the findings of the study, it can be concluded that the acute oral in rats of both sexes observed over a period of 14 days is ca 7700 mg/kg bw.

Two supporting studies, conducted on samples characterized by a limited content of the test substance, are also available.

In one case, 5 male and 5 female rats received the test item at the single dose of 5000 mg/kg bw by oral intubation. No mortality was observed through the duration of the study. Clinical signs like dyspnoea, ruffled furs and curved body position were observed. The animals recovered within 11 days. No effect on body weight gains was seen. No substance related gross organ changes were seen during the gross pathological examination. The LD50 was determined to be higher than 5000 mg/kg bw.

In the other, four groups of 5 male and 5 female rats received the test item at the doses of 3000, 5000, 7000 and 8000 mg/kg bw by oral intubation. No mortality was observed through the duration of the study. Dyspnoea, exophthalmos, curved position and ruffled fur were the clinical signs observed at all dose levels. Further clinical signs of sedation and diarrhoea were observed at the higher doses of 5000, 7000 and 8000 mg/kg bw. The surviving animals recovered within 7 to 12 days. One female died at 5000 mg/kg bw, while 2 males and 3 females died at 8000 mg/kg bw. No effect on body weight gains was seen. No substance related gross organ changes were seen during the gross pathological examination. The LD50 was identified to be of approximately 8000 mg/kg bw.

ACUTE TOXICITY BY INHALATION ROUTE

Acute inhalation toxicity of the test substance was evaluated in a study conducted according to a methodology similar to OECD guideline 403. Two groups each consisting of 10 males and 10 females were exposed to the dust of the test substance at the concentrations of 1505 and 2130 mg/m3. Though MMAD/GSD were not determined, particle size distribution (> 40 % particles were of 1-3 µm, > 30 % particles were of 0-1 µm for the concentration of 1505 mg/m³, while for the concentration of 2130 mg/m³, > 70 % particles were of 0 -1 µm size), indicated good respirability. No mortality occurred throughout the observation period. The animals were sacrificed and autopsied after an observation period of 14 days. No substance related gross organ changes were seen. Based on the findings of the study, it can be concluded that the LC50 of the test substance in rats of both sexes observed over a period of 14 days is greater than 2130 mg/m³.

ACUTE TOXICITY BY DERMAL ROUTE

According to the Commission Regulation (EU) 2016/863, amending Annexes VII and VIII to REACH Regulation (EC) No 1907/2006, testing by the dermal route does not need to be conducted if no systemic effects have been observed in in vivo studies with dermal exposure (e.g. skin irritation, skin sensitisation). Furthermore, it is explained that scientific analysis of available data from in vivo acute toxicity studies have shown that substances that are not toxic via the oral route may be expected with high certainty to be also non-toxic via the dermal route. Therefore, testing those substances via the dermal route does not provide essential information for their safety assessment. The amendment is the consequence of studies and scientific debates, concluding that an adaptation of point 8.5.3 of Annex VIII to REACH is justified in order to not require information on acute dermal toxicity for substances that have shown no toxicity in acute oral toxicity test up to the limit dose of 2000 mg/kg bw.

In the oral acute toxicity test, no signs of systemic toxicity were recorded at the dose of 2000 mg/kg bw. In addition, data on topical application of the test item to rabbits and guinea pigs is available to investigate skin irritation and sensitization effects are available. In the skin sensitisation study, no signs of toxicity have been noted in all animals exposed to the test item, even when the exposed skin area was abraded before test substance application allowing a deeper penetration of the test material in the damaged skin.

During the key skin irritation test, no erythema or edema were seen with the exposed intact skin; slight irritation was observed with abraded skin of 3 rabbits. Based on the findings of the study, it was concluded that the substance is not a skin irritant.

Justification for classification or non-classification

According to the CLP Regulation (EC) No 1272/2008, 3.1 Acute toxicity section, substances can be allocated to one of four toxicity categories based on acute toxicity by the oral, dermal or inhalation route according to the numeric criteria. Acute toxicity values are expressed as (approximate) LD50 (oral, dermal) or LC50 (inhalation) values or as acute toxicity estimates (ATE).

The oral LD50 value was established to be greater than 2000 mg/kg body weight, therefore the test substance is out of any classification limit for acute oral toxicity (oral acute toxicity category 4: 300 < ATE ≤ 2000 mg/kg bw).

Inhalation exposure is unlikely and the substance is not expected to be harmful/toxic by dermal route.

In conclusion, the test substance does not meet the criteria to be classified for oral acute toxicity, according to the CLP Regulation (EC) No 1272/2008.