Decamethylcyclopentasiloxane

Toxicity to soil macroorganisms except arthropods

Description of key information

LC50 (28-day): >4074 mg/kg dry weight, Eisenia andrei, reliability 2 NOEC (56-day): ≥4074 mg/kg dry weight, reproduction and growth, Eisenia andrei, reliability 2

LC50 (28-day): >76 mg/kg (nominal); >41 mg/kg (mean measured), for effects on survival and weight change of adult earthworms, Eisenia fetida. 

NOEC (28-day): 76 mg/kg (nominal); 41 mg/kg (mean measured), for effects on survival and weight change of adult earthworms, Eisenia fetida.

EC50 (56-day): >76 mg/kg (nominal); >41 mg/kg (mean measured) for effects on reproduction of Eisenia fetida

NOEC (56-day): 76 mg/kg (nominal); 41 mg/kg (mean measured) for effects on reproduction of Eisenia fetida.

Additional information

A 28-day LC₅₀ value of >4074 mg/kg dry weight and a 56-day NOEC of ≥4074 mg/kg dry weight have been determined for the effects of the test substance on mortality, and on reproduction and growth, respectively of Eisenia andrei (Velicogna et al., 2011).

A soil stability test with D5, under OECD 222 conditions was carried out to determine whether OECD 222 testing was possible (Knoerr, 2015). The organic carbon content of the soil was 3%. The soil was spiked with D5 at close to the sorption capacity of D5 relative to the organic carbon content of the soil. This was calculated to be 76 mg/kg dw, based on the organic carbon content of the soil and the solubility of D5 in organic carbon. The soil stability study included an assessment of homogeneity, which indicated that the test substances was homogeneously mixed with the soil after rolling on a mixer for approximately 24 hours. The soil stability study indicated that when the soil moisture content was maintained above 20% by weight, evaporative losses were minimal over the course of 56 days. It also showed that when the moisture content dropped below 20%, the test article degradation was accelerated. The Water Holding Capacity (WHC) of the test soil was determined to be 59.1%. OECD 222 recommends to conduct the test at 40% to 60% of the WHC. Therefore, an OECD 222 study in this soil would be conducted at a moisture content of 23.6 to 35.5%.

Subsequent to the soil stability study, a 56-d toxicity to earthworm's test was carried out (Smithers Viscient, 2015). No effects were observed at a measured concentration of 41 mg/kg dw. 28-d LC₅₀ values of >76 mg/kg nominal concentration and >41 mg/kg mean measured concentration, and NOECs of 76 mg/kg nominal concentration and 41 mg/kg mean measured concentration, were determined for effects of D5 on survival and weight change of adult earthworms, Eisenia fetida.

In the same test, 56-d EC₅₀ values of >76 mg/kg nominal concentrations and >41 mg/kg mean measured concentration, and NOECs of 76 mg/kg nominal concentration and 41 mg/kg mean measured concentration, were determined for effects of D5 on reproduction of Eisenia fetida.

Reference: Knoerr, SM (2015); Non Regulated Study: Assessment of Homogeneity and Stability of 14C-Decamethylpentacyclosiloxane in Natural Soil; Testing Facility: Dow Corning Corporation, Health and Environmental Sciences (HES), 2200 W. Salzburg Road, Auburn, MI 48611; Study Number: 12493-116; Report Date: 05 February 2015.