Octamethylcyclotetrasiloxane

Endpoint summary

Additional information

There are several different metrics that are used to calculate bioaccumulation, so to ensure clarity, the various terminologies associated with aquatic bioaccumulation assessments are defined below:

Bioconcentration factor (BCF): Concentration of test substance in the fish or specified tissues thereof divided by the concentration of the chemical in the surrounding medium.

Biomagnification factor (BMF): Concentration of a substance in a predator relative to the concentration in the predator’s prey or food. (The dietary BMF from a laboratory test method that soley examines bioaccumulation from a dietary exposure cannot directly be compared to a BMF value from a field study in which both the water and dietary exposure may be combined.)

Depuration (loss) rate constant (k2): The numerical value defining the rate of reduction in the concentration of the test substance in the test fish (or specified tissues thereof) following the transfer of the test fish from a medium containing the test substance to a medium free of that substance (k₂ is expressed in day-1).

Kinetic bioconcentration factor (BCF_K): The ratio of the uptake rate constant,k₁, to the depuration rate constant,k₂when the concentration of the chemical is delivered in the surrounding medium (i.e. water only exposure).

Kinetic biomagnification factor (BMF_K): The ratio of the uptake rate constant, k₁, to the depuration rate constant, k₂, when the concentration of the chemical is delivered in the diet (i.e. dietary only exposure).

Growth corrected kinetic bioconcentration factor (BCF_Kg): The growth rate of the fish is corrected for in the BCF calculation either via the growth rate constant substraction method (i.e.growth rate, k_g, is subtracted from the total depuration rate constant, k₂) or via the mass based method (see OECD 305; Annex 5). Of note: There have been recent criticisms of the methodologies to correct for growth, specifically via the growth rate constant subtraction method (Gobas et al., 2019). Therefore these approaches were ultimately not deemed acceptable for the assessment of bioaccumulation for D4.

Growth corrected kinetic biomagnification factor (BMF_Kg): The growth rate of the fish is corrected for in the BMF calculation either via the growth rate constant substraction method (i.e. growth rate, k_g, is subtracted from the total depuration rate constant, k₂) or via the mass based method (see OECD 305; Annex 5). Of note: There have been recent criticisms of the methodologies to correct for growth, specifically via the growth rate constant subtraction method (Gobas et al., 2019). Therefore these approaches were ultimately not deemed acceptable for the assessment of bioaccumulation for D4.

 

Lipid normalised kinetic bioconcentration factor (BCF_KL): The kinetic BCF is normalised by fish lipid content. In some cases, a default 5% value for fish lipid content is used.

Lipid normalised kinetic biomagnification factor (BMF_KL): The kinetic BMF is normalised by fish and dietary lipid content. In some cases, a default 5% value for fish lipid content is used.

Lipid normalised, growth corrected kinetic bioconcentration factor (BCF_KgL): Kinetic BCF normalised to fish lipid content (sometimes a default fish lipid content of 5% is used) and corrected for growth dilution during the study period. Growth dilution can be accounted for either via the growth rate constant substraction method (i.e.growth rate, k_g, is subtracted from the total depuration rate constant, k₂) or via the mass based method (see OECD 305; Annex 5). Of note: There have been recent criticisms of the methodologies to correct for growth, specifically via the growth rate constant subtraction method (Gobas et al., 2019). Therefore these approaches were ultimately not deemed acceptable for the assessment of bioaccumulation for D4.

Lipid normalised, growth corrected kinetic biomagnification factor (BMF_KgL): Kinetic BMF normalised to fish and diet lipid content (sometimes a default fish lipid content of 5% is used) and corrected for growth dilution during the study period. Growth dilution can be accounted for either via the growth rate constant substraction method (i.e.growth rate,k_g, is subtracted from the total depuration rate constant, k₂) or via the mass based method (see OECD 305; Annex 5). Of note: There have been recent criticisms of the methodologies to correct for growth, specifically via the growth rate constant subtraction method (Gobas et al., 2019). Therefore these approaches were ultimately not deemed acceptable for the assessment of bioaccumulation for D4.

Lipid normalised steady-state bioconcentration factor (BCF_SSL): The BCFss is normalised to fish lipid content. In some cases, a default 5% value for fish lipid content is used.

Lipid normalised steady-state biomagnification factor (BMF_SSL): The BMFss is normalised to fish and diet lipid content. In some cases, a default 5% value for fish lipid content is used.

Steady-state bioconcentration factor (BCF_SS): The BCF does not change significantly over a prolonged period of time; the concentration of the test substance in the surrounding medium being constant during this period of time.

Steady-state biomagnification factor (BMF_SS): The BMF does not change significantly over a prolonged period of time.

Trophic Magnification Factor (TMF): A metric of thethe “average BMF” of the chemical in the sampled ecosystem at various trophic levels of a fod web.

Uptake rate constant (k₁): The numerical value defining the rate of increase in the concentration of test substance in test fish (or specified tissues thereof) when the fish are exposed to that chemical (k₁ is expressed in L kg-1 day-1).