CRA

Bio-accumulation

Little Pro on 2016-02-01 Views:  Update:2018-08-13

Bioconcentration Factor (BCF) is an indicator of a chemical substance’s tendency to accumulate in the living organism. It can be obtained by calculation method based on logPow or bio-accumulation test. Calculated BCF values are unitless and generally range from one to a million.

If an aquatic bioconcentration test (usually on fish) is conducted, BCF will be the concentration of test substance in/on the fish or specified tissues thereof (as mg/kg) divided by the concentration of the chemical substance in the surrounding medium (as mg/L or mg/Kg).

  • BCF = Concentration of the substance in fish (mg/kg)/Concentration of the substance in water (mg/L).

The unit of BCF is L/kg.  The bioconcentration factor (BCF) may also be expressed as the ratio of the uptake rate constant (k1) to the depuration rate constant (k2).

A chemical substance with high BCF will generally have low water solubility, a large Kow (octanol/water partition coefficient), and a large Koc (soil adsorption coefficient).

Bio-concentration Criteria and Chemical Risk Assessment

  • United States: a substance is considered to be not bioaccumulative if it has a BCF less than 1000, bioaccumulative if it has a BCF from 1000–5000 and very bioaccumulative if it has a BCF greater than 5,000.
  • EU REACH:a substance with a BCF>2000 will be regarded as bio-accumulative (B). A substance with a BCF>5000 will be regarded as very bio-accumulative (vB).

n-octanol/water partition coefficient is often used as a screening test for bio-accumulation test. The assumption behind this is that the uptake of an organic substance is driven by its hydrophobicity. For organic substances with a Log Kow value below 4.5 it is assumed that the affinity for the lipids of an organism is insufficient to exceed the bio-accumulation criterion i.e. a BCF value of 2000.

Please be noted that Kow is not applicable for surface reactive substances, mixtures with molecular weight distributions, organic metal compounds, low-purity samples (expect HPLC method) and inorganic compounds.

Testing Guidelines

References

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You have learned the definition of bio-accumulation and bio-concentration factor (BCF), testing guidelines, and bio-concentration criteria in US and USA. .

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