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Differences between BCF, BAF and BMF

Little Pro on 2017-04-25 Views:  Update:2018-10-17

Bio-concentration factor (BCF), bio-accumulation factor (BAF) and biomagnification factor (BMF) can be used in assessing the bioaccumulation potential of a substance. In this article, we will summarize their definition and differences.

Comparison of BCF, BAF and BMF

BCF, BAF and BMF all belong to bio-accumulation data and they are obtained from different studies. Their units are also different. In EU, a valid BCF or BAF > 2000 or 5000 indicates bio-accumulative (B) or very bio-accumulative (vB).

Item Definition Unit Testing Method

BCF*

Concentration of test substance in fish or other tissue (mg/kg)/Concentration of the substance in water (mg/L). L/kg
  • OECD TG 305-I: Aqueous Exposure Bioconcentration Fish Test 
BMF ** Concentration of a substance in a predator (mg/kg)/Concentration in the predator’s prey (or food) at steady-state (mg/kg) Unitless
  • OECD TG 305-III: Dietary Exposure Bioaccumulation Fish Test
BAF *** Concentration of test substance in the test organism (g/kg)/Concentration of the substance in the surrounding medium such as sediment or soil (g/kg). Unitless
  • OECD TG 315 Bioaccumulation in Sediment-dwelling Benthic Oligochaetes
  • OECD TG 317 Bioaccumulation in Terrestrial Oligochaetes 

* BCF is the result of a balance between the rate of chemical uptake from the water via the respiratory surface of the test organism (i.e, gills and/or skin) and the elimination of the chemical from the organism. It may also be expressed as the ratio of the uptake rate constant(k1) to the depuration rate constant (k2). 

** For strongly hydrophobic substances (Log Kow > 5 or high Koc and a water solubility below ~ 0.01-0.1 mg/L), testing via aqueous exposure is difficult. In this case, a dietary study in fish is better. A BMF will be identified instead of BCF.

*** BAF is a result of both bio-concentration and bio-magnification. It takes into account of both the exposure from respiratory surface and the dietary exposure. 

Reference

ECHA guidance on information requirements and chemicals safety assessment R.11 PBT assessment

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