Registration Dossier

Administrative data

Workers - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
64 mg/m³
Most sensitive endpoint:
effect on fertility
DNEL related information
Overall assessment factor (AF):
36
Modified dose descriptor starting point:
NOAEC
Acute/short term exposure
DNEL related information

Local effects

Acute/short term exposure
DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
9 mg/kg bw/day
Most sensitive endpoint:
effect on fertility
DNEL related information
Overall assessment factor (AF):
36
Modified dose descriptor starting point:
NOAEL
Acute/short term exposure
DNEL related information

Workers - Hazard for the eyes

Additional information - workers

Hexamethylcyclotrisiloxane (D3) is a volatile liquid with low water solubility and fairly high Log Kow. It hydrolyses rapidly, initially to hexamethyltrisiloxanediol (3663-50-1)and finally to dimethylsilanediol (DMSD, CAS 1066-42-8). Exposure may occur via the inhalation or dermal routes. Exposure may be to either the parent substance or the hydrolysis products.

 

There are adequate data available regarding the repeated dose toxicity of D3 via the inhalation route, but there are no reliable data of sufficient duration for the dermal and oral routes. 

The key repeated dose toxicity study was a 90-day inhalation study conducted in male and female rats, largely according to OECD 413 and with GLP compliance. The study identified a NOAEC value of 150 ppm (1.4 mg/l) in male and female rats. Overt toxicity and body weight effects were evident at 601 ppm (5.5 mg/l) which was identified as the LOAEC. 

Only one study examining toxicity to reproduction and development is available. This study was a combined repeated dose toxicity study with the reproduction/developmental toxicity screening test (OECD 422) in which the test material was administered via the inhalation route to rats. This screening study identified an NOAEC for reproductive effects of 500 ppm (4.55 mg/l) for the parental and foetal generations. The higher concentration, 2500 ppm (22.8 mg/l), which caused effects on maternal body weight, reduced litter size and number of implantation sites, was identified as the LOAEC (parental and foetal). This screening study did not identify any gross external abnormalities among the foetuses.

No quantitative DN(M)ELs could be derived for:

Acute toxicity – local effects

Long-term toxicity – local effects

Mutagenicity (substance is not mutagenic)

Carcinogenicity (no data to suggest that the substance is carcinogenic)

DNELs were derived for repeated dose toxicity but are higher than those based on reproductive toxicity.

The critical health effect is considered to be reduced litter size and number of implantation sites in the OECD 422 study. D3 is not classified as mutagenic, carcinogenic or sensitising.

The DNELs used for risk characterisation for workers are therefore:

DNEL (long-term, inhalation):64 mg/m3(7 ppm)

DNEL (long-term, dermal): 9 mg/kg bw/d

 

General Population - Hazard via inhalation route

Systemic effects

Acute/short term exposure
DNEL related information

Local effects

Acute/short term exposure
DNEL related information

General Population - Hazard via dermal route

Systemic effects

Acute/short term exposure
DNEL related information

General Population - Hazard via oral route

Systemic effects

Acute/short term exposure
DNEL related information

General Population - Hazard for the eyes

Additional information - General Population

Consumer exposure is not expected, therefore DNELs for consumers are not calculated.