Reaction mass of decamethyltetrasiloxane; dodecamethylpentasiloxane; hexamethyldisiloxane; octamethyltrisiloxane

Endpoint summary

Additional information

No data are available for toxicity of the whole substance to aquatic or sediment dwelling organisms.

Available data have been read-across from each constituent of the multiconstituent substance.

Constituent HMDS

Reliable short-term toxicity tests results are available for the effects of Constituent HMDS on freshwater fish (Oncorhynchus mykiss), and algae (Selenastrum capricornutum (new name: Pseudokirchneriella subcapitata)).

Studies for invertebrates (Daphnia magna) exist but were not considered to be reliable. However, in accordance with Column 2 specific rules for adaptation from Column 1 of Annex VII of the REACH Regulation, the short-term invertebrate study does not need to be conducted because a long-term aquatic toxicity study on invertebrates is available.

A 96-hour LC₅₀ value of 0.46 mg/l (expressed as measured concentration) has been determined for effects of HMDS on mortality of O. mykiss.

A 70-hour ErC₅₀ value of >0.55 mg/l and ErC₁₀ of 0.09 mg/l have been determined for the effects of HMDS on growth rate of S. capricornutum.

In a long-term test a 21-day EC₅₀ value of 0.30 mg/l and NOEC of 0.08 mg/l have been determined for the effects of HMDS on reproduction of Daphnia magna.

No reliable experimental test results are available for long-term toxicity of HMDS to fish. A read-across 90-day NOEC of ≥27 μg/l (0.027 mg/l) has been determined for the effects of structurally-similar substance octamethyltrisiloxane (L3, CAS 107-51-7) on early-life stages of Oncorhynchus mykiss.

An estimated chronic NOEC of 0.020 mg/l for fish for HMDS is available using a reliable QSAR method.

 

Reliable studies are available for toxicity to microorganisms.

A NOEC (3 h) value of ≥100 mg/l and an EC₅₀ value of >100 mg/l have been determined in an activated sludge respiration inhibition study.

 

Constituent L3

Reliable test data are available describing the short-term toxicity of L3 to fish, invertebrates and algae:

Fish: A 96-hour LC₅₀ value of >19 μg/l has been determined for the effects of L3 on mortality of Oncorhynchus mykiss based on mean measured concentrations. The results were obtained under flow-through test conditions.

Invertebrates: A 48-hour EC₅₀ value of >20 μg/l has been determined for the effects of L3 on mobility of Daphnia magna based on mean measured concentrations. The results were obtained under flow-through test conditions.

Algae: A 72-hour EC₅₀ value of >9.4 μg/l and NOEC of ≥9.4 μg/l have been determined for the effects of L3 on growth rate and biomass (yield) of Pseudokirchneriella subcapitata based on mean measured concentrations. The results were obtained under sealed test conditions.

 

Data are also available describing the long-term toxicity of L3 to fish and invertebrates:

Fish: A NOEC of ≥27 μg/l (time-weighted mean measured concentration) has been determined in an early life stage test in which effects on embryo survival, larval hatch and growth (length and dry weight) of Oncorhynchus mykiss were evaluated over a 90-day period (including a period of approximately 6 weeks after controls were free-feeding). The test results were obtained under flow-through exposure conditions.

Invertebrates: A 21-day NOEC of ≥15 μg/l has been determined for effects on growth and reproduction of Daphnia magna. The results were obtained under flow-through test conditions and are expressed as time-weighted mean measured concentrations.

 

There are no microorganism toxicity data available for L3, therefore good quality data for the structurally-related substance L4 (decamethyltetrasiloxane, CAS 141-62-8), have been read across. A 3hr EC₅₀ value of >100 mg/l (loading rate) was determined for L4.

 

Constituent L4

Reliable short-term data are available describing the toxicity of L4 to freshwater fish and algae:

Fish: A 96-hour LC₅₀ value of >6.3 μg/l (mean measured; highest concentration tested) has been determined for the effects of L4 on mortality of Oncorhynchus mykiss based on mean measured exposure concentrations. In view of the use of flow-through test conditions it is likely that the test organisms were exposed primarily to the parent substance.

Algae: A 72-hour EC₅₀ value of >2.2 μg/l and NOEC of ≥2.2 μg/l have been determined for the effects of L4 on growth rate of the freshwater algae Pseudokirchneriella subcapitata. The results are expressed as geometric mean measured concentrations.

 

Data are also available describing the long-term toxicity of L4 to fish and invertebrates:

A 96-hour LC₅₀ value of >6.3 μg/l (mortality) and 60-day post-hatch NOEC of ≥7.9 μg/l (hatching, larval survival, abnormal appearance and behaviour) have been determined for the effects of L4 on Oncorhynchus mykiss based on geometric mean measured exposure concentrations and time-weighted average measured concentrations, respectively.

A 21-day NOEC value of ≥4.9 μg/l based on adult mortality, reproduction and growth has been determined for the effects of L4 on Daphnia magna under flow-through conditions and expressed relative to mean measured concentrations.

A data waiver is applicable to the short-term toxicity to invertebrates endpoint since long-term data are available.

 

An EC₅₀ value of >100 mg/l for toxicity to microorganisms was determined in a reliable ASRI study conducted according to an appropriate test protocol, and in compliance with GLP.

 

Constituent L5

There are no short-term toxicity data with L5 for aquatic invertebrates and algae. Data are available for short-term toxicity of L5 to fish:

A 96-hour LC₅₀ value of >75 ng/l has been determined for effects of L5 on mortality of Oncorhynchus mykiss based on mean measured concentrations of the substance in a flow-through test.

Short-term aquatic toxicity data for invertebrates is not required because reliable long-term aquatic toxicity data for invertebrates is available.

Toxicity to aquatic algae data have been read-across from a structural analogue, L4 (decamethyltetrasiloxane, CAS 141-62-8):

A 72-hour EC₅₀ value of >2.2 μg/l and NOEC of ≥2.2 μg/l have been determined for the effects of L4 on growth rate of the freshwater algae Pseudokirchneriella subcapitata, based on geometric mean measured concentrations.

 

Long-term toxicity data with L5 are available for aquatic invertebrates:

A 21-day EC₅₀ of >47 ng/l and NOEC of ≥47 ng/l have been determined for the effects of L5 on adult mortality, reproduction and growth of Daphnia magna. The data have been obtained in flow-through tests and are expressed relative to mean measured concentrations of the substance. These concentrations were measured in test media prepared at a nominal concentration that corresponded with the water solubility of the substance (70 ng/l).

 

The key result for long-term toxicity in fish with L5 is good quality data from the structurally-related substance L4 (decamethyltetrasiloxane, CAS 141-62-8). A 60-day post-hatch NOEC of ≥7.9 µg/l (time weighted mean measured) has been determined for the effects of L4 on hatching, larval survival, abnormal appearance and behaviour of Oncorhynchus mykiss in the fish early-life stage test (OECD 210).

 

There are no reliable data available with L5 for toxicity to microorganisms.

A 3-hour EC₅₀ value of >100 mg/l (ASRI) is read-across from the structurally-related substance L4 (CAS 141-62-8).