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Administrative data

Description of key information

Acute Oral Toxicity - Fixed Dose Method OECD Guideline 420, limit dose: LD50 >2000 mg/kg bw  (Acute Inhalation Toxicity) (OECD Guideline 403), modified: whole-body, 5M/5F, one dose of 4.9 mg/l (vapour): LC50 >4.9 mg/l

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LD50
2 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LC50
4 900 mg/m³

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

2,4,6,8,10 -Pentamethylcyclopentasiloxane did not show any evidence of toxicity, barring some slightly ruffled fur, at a dose level of 2000 mg/kg body weight after single oral administration to six female rats, observed over a period of 14 days.

In an acute inhalation study in rats, a mixture of the registered substance and a structurally related substance

(2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-88-9) at 54%)

was tested at a limit dose of 4.9 mg/l (as per OECD guideline at the time the study was performed). No mortality or clinical signs of toxicity were observed.

No acute dermal toxicity test is available.

This result is supported by results from a 14-day repeated dose range finding study with a related substance HD4 (2370-88-9, 2,4,6,8-Tetramethylcyclotetrasiloxane). No mortalities were observed at 1000 ppm (9.8 mg/l); onemale animal (out of 5 animals) in the 4000 ppm (39 mg/l) group was killedin extremisand there was one female (out of 5 animals) spontaneous death in this dose group. This study wasconducted in preparation for the ongoing 28-day repeated dose inhalation toxicity study with HD4.

Given the absence of any toxic effect at 4.9 mg/l in the acute study as well as in the acute irritation/ corrosion studies and in the repeated dose study at a higher dose level, no classification is required. 

Read-across justification

Read-across to the submission substance is justified because: (i) the test substance includes ca.50% by weight of the submission substance, and (ii) the second component is a close structural analogue of the submission substance.

 

Also, HD5 is one of a number of cyclic siloxanes containing no functional groups for which acute toxicity data are available. The results of all available studies, summarised in Table 5.2.3, are in agreement and show that none of the substances in this analogue group is acutely harmful by any exposure route.

Table 5.2.3 Acute toxicity data for cyclic siloxanes

CAS Number

556-67-2

2370-88-9

541-02-6

Mixture of 2370-88-9 / 6166-86-5

6166-86-5

540-97-6

Name

Octamethylcyclotetrasiloxane

2,4,6,8-tetramethylcyclotetrasiloxane

 

Decamethylcyclopentasiloxane

 

2,4,6,8,10-pentamethylcyclopentasiloxane

 

Dodecamethylcyclohexasiloxane

Synonym

D4

HD4

D5

HD4/HD5

HD5

D6

Acute oral toxicity LD50(mg/kg bw)

>4800

(Löser, 1979)

>2000

(Reconsile, 2010a)

>5000

(Toxikon, 1990a)

 

>2000

(Reconsile, 2010b)

>2000

(Notox, 1999a)

Acute dermal toxicity LD50(mg/kg bw)

>2400

(Ramm, 1985)

-

>2000

(WIL, 1977)

 

-

>2000

(Notox, 1999b)

Acute inhalation toxicity LC50(mg/l)

36 mg/l

(Dow Corning Corporation, 1994)

-

8.7 mg/l

(RCC, 1994)

>5 mg/l (Dow Corning Corporation, 2002a)

-

-

 


Justification for classification or non-classification

Based on the available data, no classification for acute oral and inhalation toxicity is required for the registered substance according to Regulation (EC) No 1272/2008.

Acute toxicity, oral:

LD50 (female rat): greater than 2000 mg/kg body weight

Based upon the referred classification criteria (Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008), 2,4,6,8,10-pentamethylcyclopentasiloxane is not classified with respect to acute oral toxicity in the rat.

Acute toxicity, Inhalation: LC50, rat >4.9 mg/l

This result is supported by results from a 14-day repeated dose range finding study with a related substance HD4 (CAS 2370-88-9, 2,4,6,8-tetramethylcyclotetrasiloxane). No mortalities were observed at 1000 ppm (9.8 mg/l); one male animal (out of 5 animals) in the 4000 ppm (39 mg/l) group was killed in extremis and there was one female (out of 5 animals) spontaneous death in this dose group. This study was conducted in preparation for the 28-day repeated dose inhalation toxicity study with HD4.

Given the absence of any toxic effect at 4.9 mg/l in the acute study as well as in the acute irritation/ corrosion studies and in the repeated dose study at a higher dose level, no classification is required.