Hydroxytrimethylsilane

Bioaccumulation: aquatic / sediment

Description of key information

Bioaccumulation: aquatic / sediment (HMDS): BCF: 1290 - 2410 l/kg (40 µg/l); 776 - 1660 l/kg (4 µg/l) (national method equivalent to OECD 305 C). Empirical average BCF: 1684 l/kg (40 µg/l); 1181 l/kg (4 µg/l) (calculated by the registrant from the experimental data). Lipid-normalised empirical average BCF: 1958 l/kg (40 µg/l) and 1374 l/kg (4 µg/l) (calculated by the registrant from the experimental data). Growth-corrected kinetic BCF: 1695 l/kg (40 µg/l); 1420 l/kg (4 µg/l) (calculated by registrant from the experimental data using first-order fish uptake/depuration model). Growth-corrected lipid-normalised kinetic BCF: 1971 l/kg (40 µg/l) and 1652 l/kg (4 µg/l) (calculated by registrant from the experimental data using first-order fish uptake/depuration model). In exposure modeling (EUSES 2.1.2) the growth-corrected lipid-normalised kinetic BCF value of 1971 l/kg (40 µg/l) will be used as a worst case.

Key value for chemical safety assessment

BCF (aquatic species):

1 971 L/kg ww

Additional information

BCF values of 1290 - 2410 l/kg (40ug/l); 776 - 1660 l/kg (4ug/l) have been determined for hexamethyldisiloxane with carp in separate exposures at two concentrations in a reliable study conducted according to an appropriate test protocol (Japanese Industrial Standard test method, essentially the same as OECD 305C), with acceptable restrictions. The restrictions were that there was no depuration and there was some variability in concentration in fish between replicates at later sampling points.

The study reports the range of BCF values at each exposure level; no steady state BCF (BCF_ss) values are reported.

Empirical average BCF values at each exposure level of 1684 l/kg (40 µg/l) and 1181 l/kg (4 µg/l) have been calculated by the registrant from the experimental data. Lipid-normalised empirical average BCF values (normalised to default fish lipid content of 5% wwt) are 1958 l/kg (40 µg/l) and 1374 l/kg (4 µg/l). Application of a first-order fish uptake/depuration model to the experimental data, by the registrant, produced an acceptable fit at both the low- and high-level L2 exposures, with uptake rate constants ranging from 84 to 1000 l kg^-1 day^-1 and growth-corrected depuration rate constants ranging from 0.059 to 0.59 day^-1. These values produce steady-state kinetic BCF (BCFk) values of 1420 and 1695 l/kg for the low- and high-level L2 exposures, respectively; these values are consistent with the empirical BCF values, indicating that steady-state concentrations of L2 were achieved in the carp. Lipid-normalised BCFk values are 1971 l/kg (40 µg/l) and 1652 l/kg (4 µg/l). The carp had a measured lipid content of 4.3% and the estimated freely-dissolved fraction of L2 in water is 100%, resulting in a lipid-adjusted, freely-dissolved BCFLW/fd values of 3.30 E+04 and 3.94 E+04 l/kg-lipid, for the low- and high-level exposures, respectively. These values, expressed as a biota/water fugacity ratio, Fbiota/water, produces values for the low- and high-level L2 exposures of 0.29 and 0.34, respectively. Fugacity ratio values less than 1.0 are indicative of materials that do not pose a bioaccumulation/biomagnifications risk to aquatic organisms.  For further information refer to Dow Corning Corporation, 2014. DOW CORNING TECHNICAL REPORT Kinetic Modeling Interpretation of Hexamethyldisiloxane (CAS RN 107-46-0) Fish Bioconcentration Data with the Common carp (Cyprinus carpio)). 2014. Attached to the EPSR.