Hexyltrimethoxysilane

Endpoint summary

Description of key information

Oral:  OECD TG 401: LD50 > 3500 mg/kg bw (read across from CAS 1067 -25 -0 and 3069 -40 -7)

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

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

Remarks:

Summary of available data used for the endpoint assessment of the target substance

Adequacy of study:

weight of evidence

Justification for type of information:

refer to the analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Sex:

male

Dose descriptor:

LD50

Effect level:

> 5 170 mg/kg bw

Based on:

test mat.

Remarks on result:

other: CAS 1067-25-0, ASTA Pharma, 1988

Sex:

female

Dose descriptor:

LD50

Effect level:

ca. 5 170 mg/kg bw

Based on:

test mat.

Remarks on result:

other: CAS 1067-25-0, ASTA Pharma, 1988

Sex:

male

Dose descriptor:

LD50

Effect level:

ca. 5 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: CAS 3069-40-7, ASTA Pharma, 1988

Sex:

female

Dose descriptor:

LD50

Effect level:

> 3 500 mg/kg bw

Based on:

test mat.

Remarks on result:

other: CAS 3069-40-7, ASTA Pharma, 1988

The key result of an oral LD50 >= 5170 mg/kg bw found with the source substance CAS 1067 -25 -0 is supported by an older study which is used as supporting study (INBIFO, 1979) where a LD50 for male rats was 7420 mg/kg bw.

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulations (EC) No 1272/2008.

Conclusions:

In acute oral toxicity studies conducted in compliance with the now deleted OECD 401, but not to GLP (reliability score 2), the LD50 values for the source substances trimethoxy(propyl)silane (CAS 1067-25-0) and trimethoxy(octyl)silane (CAS 3069-40-7) were > 3500 mg/kg bw, for male and female rats, respectively. As explained in the analogue justification, it is considered that the target and the source substances are unlikely to lead to differences in acute oral toxicity potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

3 500 mg/kg bw

Quality of whole database:

The available information comprises an adequate and reliable study (Klimisch score 2) from a source substance with similar structure and intrinsic properties. Read-across is justified based on common functional group(s) and similarities in PC/ECO/TOX properties. The selected study is thus sufficient to fulfil the standard information requirements set out in Annex VII, 8.5, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006.

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

No acute oral toxicity study on hexyl(trimethoxy)silane (CAS 3069-19-0) is available. Therefore, the hazard assessment for acute oral toxicity of the registered substance was performed based on the available data from the source substances trimethoxy(propyl)silane (CAS 1067-25-0) and trimethoxy(octyl)silane (CAS 3069 -40 -7). In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and following the Read across assessment framework (RAAF, ECHA 2017) read across from analogue substances has been applied to support the human health hazard assessment of hexyl(trimethoxy)silane (CAS 3069-19-0).

The acute oral toxicity study with the source substance trimethoxy(propyl)silane (CAS 1067 -25 -0) which was conducted in compliance with GLP and according to the now deleted OECD TG 401, reports an LD50 value of ≥ 5170 mg/kg bw, for male and female rats, respectively. These values indicate low acute toxicity by the oral route of the registered substance. The most common signs of toxicity were reduced locomotion, impaired co-ordination, loss of muscle tone and loss of righting reflex (ASTA Pharma, 1988). In an additional acute oral toxicity study similar to the now deleted OECD TG 401 and not to GLP with trimethoxy(propyl)silane identified an LD50 value in the rat of 7420 mg/kg bw (INBIFO, 1979a). The results of both experiments are in agreement with the low acute oral toxicity (lethality) potential of trimethoxy(propyl)silane (CAS 1067 -25 -0).

In an acute oral toxicity study with the source substance trimethoxy(ocytyl)silane (CAS 3069 -40 -7) that was comparable to the now deleted OECD 401, but not to GLP (reliability score 2) the LD50 was at least 3500 mg/kg bw for male and female rats (ASTA Pharma AG, 1988). Following a dose of 3236 mg/kg bw there were coordination disturbances, piloerection, chromodacryorrhea, increased salivation and red nasal discharge. Following a dose of 4752 mg/kg bw there was additionally decreased muscle tone, loss of righting reflexes and increased diuresis. Individually, tremor, vocalisation on handling, lacrimation, opacity of the cornea and green discoloured urine occurred in addition. The development of toxic effects was protracted, with coordination disturbances detected after two hours, and all other symptoms from days 2-5. All symptoms disappeared by day 21 of the observation period.

In conclusion, both source substances show low acute oral toxicity with a LD50 > 3500 mg/kg bw. The same low acute oral toxicity is considered for the target substance CAS 3069 -19 -0.

Justification for classification or non-classification

Reliable data from structural analogue substances on acute oral toxicity indicates that the registered substance does not meet the criteria for classification according to Regulation (EC) No. 1272/2008, and the available data are therefore conclusive but not sufficient for classification.