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PBT assessment

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PBT assessment: overall result

OS 1600
Type of composition:
legal entity composition of the substance
State / form:
Reference substance:
OS 1600
PBT status:
the substance is not PBT / vPvB

Persistence assessment:

Hydrolysis: The substance is hydrolytically unstable in water with a half-life < 4 min at pH 4, 7 and 9 and at 20 ºC (test method OECD 111, GLP study) and therefore the substance is not persistent. Nevertheless, the hydrolysis product MPKO is hydrolytically stable with a half-life > 1 year at pH 4, 7 and 9. In addition, a ready biodegradation test (CO2 evolution) indicates that both OS1600 and MPKO are not readily biodegradable (test method OECD 301B, GLP study).

Conclusion on P / vP properties: No conclusion can be reached based on available information.

Bioaccumulation assessment:

The substance hydrolyses very rapidly (half-life < 4 min) into MPKO and the corresponding methyltrisilanol. Moreover, the trisilanol undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. The relevant hydrolysis product that will eventually end up in the environment is MPKO. Based on a log Kow value for MPKO of 1.25 (test method OECD 107, GLP study). In addition, the estimated BCF for MPKO is 3.103 (EPI-Suite, BCFBAF v3.01). Therefore it can be concluded that the substance is not bioaccumulative.

Conclusion on B / vB properties: The substance is not fulfilling the criteria for Biaccumulable (B)

Toxicity assessment:

There is no long-term toxicity study available with fish and crustacea.

Toxicity to aquatic algae: NOEC (72h) = 36 mg/L (basis for effect: growth rate) (read-across, test method OECD 201, GLP study).

Moreover, regarding the acute aquatic toxicity:

- Short-term toxicity to fish: LC50 (96h) > 113 mg/L (based on mortality) (read-across, test method OECD 203, GLP study).

- Short-term toxicity to aquatic invertebrates: EC50 (48h) > 113 mg/L (based on mobility) (read-across, test method OECD 202, GLP study).

- Toxicity to aquatic algae: EC50 (72h) = 100 mg/L (based on growth rate) (read-across, test method OECD 201, GLP study).

The substance is not classified as CMR.

The substance is not classified as for STOT RE.

Conclusion on T properties: The substance is not fulfilling the criteria for Toxicity (T).


OS1600 is not a PBT or vPvB substance.