Bioconcentration Factor

Estimate kinetic BCF with and without growth dilution from externally fitted uptake/elimination rates; dietary uptake and time-varying exposure are excluded.

Description

Calculate kinetic water-to-organism bioconcentration factors with and without a supplied growth-dilution rate.

Bioconcentration describes uptake from water relative to loss from an organism. In a first-order kinetic model, an uptake coefficient divided by a loss rate gives a concentration factor. Organism growth can also lower measured concentration by spreading chemical mass across increasing body mass.^[1]

This tool treats elimination and growth dilution as separate supplied rates. Its steady-state BCF uses their sum; its growth-corrected BCF removes the growth term. The elimination input must therefore already exclude growth dilution.

Uptake uses L/kg/day and both loss rates use 1/day, giving outputs in L/kg. A BCF is a water-to-organism concentration relationship, not a predator–prey biomagnification ratio or a whole-food-web trend.

When to use Bioconcentration Factor

Use it to inspect a first-order kinetic BCF calculation from separately established uptake, elimination, and growth rates, or compare the arithmetic influence of growth dilution.

How to use Bioconcentration Factor and interpret its calculation

Enter positive uptakeLitersPerKgDay and eliminationPerDay from a compatible kinetic interpretation.
Enter nonnegative growthDilutionPerDay as the separate growth component and run the calculation.
Read steadyStateBcfLitersPerKg and growthCorrectedBcfLitersPerKg together. Confirm that growth has not already been included in the elimination input.

BCFsteady = k1/(kelimination + kgrowth); BCFgrowth-corrected = k1/kelimination

k1 is the water-uptake coefficient. Both factors retain L/kg units.

The implementation uses the supplied rates directly and does not subtract a growth rate from an observed total depuration rate. With positive uptake and elimination, adding a nonnegative growth term makes the steady-state factor no greater than the growth-corrected factor.

json

{
  "input": {
    "uptakeLitersPerKgDay": 2,
    "eliminationPerDay": 0.1,
    "growthDilutionPerDay": 0.1
  },
  "output": {
    "steadyStateBcfLitersPerKg": 10,
    "growthCorrectedBcfLitersPerKg": 20
  }
}

At zero growth dilution the two factors are equal. Zero elimination is rejected rather than represented by an infinite corrected factor. Zero uptake is also rejected, and no negative growth-rate input is accepted.

Limitations and assumptions

Rates are supplied rather than estimated from uptake or depuration data. The model assumes first-order behavior and an appropriate, compatible uptake coefficient; removing a growth term does not automatically reproduce a nongrowing organism with changed physiology.

No dietary uptake, lipid correction, steady-state attainment check, species selection, rate uncertainty, or regulatory classification is performed.

Alternative or Complementary methods

Use paired predator and prey concentrations for biomagnification, or a food-web regression for trophic magnification. Those metrics should be identified separately rather than substituted for a kinetic BCF.

References

Test No. 305: Bioaccumulation in Fish: Aqueous and Dietary Exposure (2012) — Organisation for Economic Co-operation and Development

Similar or alternative tools

Biomagnification Factor
Calculate wet-weight and lipid-normalized predator–prey ratios.
Trophic Magnification Factor
Estimate a concentration multiplier per supplied trophic-level increase.