Bioconcentration Factor Calculator

Calculate bioconcentration and biomagnification of chemicals through food chains.

Chemical concentration in water Cw (μg/L) (μg/L)

BCF (L/kg, or enter log Kow to estimate) (L/kg)

Log Kow to estimate BCF (if BCF unknown)

BCF ≈ 10^(0.85 log Kow - 0.70)

Biomagnification factor BMF (1-10)

Each trophic level multiplier

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Three Related but Distinct Terms

These are frequently used interchangeably and should not be. Each describes a different uptake route.

Term	Uptake route	Measured in
BCF	From water only	Controlled laboratory exposure
BAF	From water and diet	Field studies
BMF	Increase per trophic level	Predator/prey concentration ratio

BCF is a laboratory measure that isolates uptake across the gills and skin. BAF is what actually happens in the field, where diet often dominates for strongly lipophilic compounds. BMF describes the step up from prey to predator, and it is the multiplication of BMF across several levels that produces the extreme concentrations seen in top predators.

Why Top Predators Accumulate Most

Each trophic step multiplies. With a BCF of 100,000 from water into small fish, and a BMF of 3 at each of three subsequent levels, the concentration in an eagle is 27 times that in the first fish and 2.7 million times that in the water.

This is the mechanism behind the DDT and eagle story, and behind mercury advisories for large predatory fish. The compounds most affected share two properties: high lipophilicity (log K_ow above 5) and resistance to metabolism. A lipophilic compound that organisms can metabolise does not accumulate this way.

BCF (L/kg)	Regulatory interpretation
< 100	Low concern
100–1,000	Moderate
1,000–5,000	Bioaccumulative
> 5,000	Very bioaccumulative

Worked Examples

Example 1: PCB in Great Lakes: Cw=0.001μg/L, BCF=100,000

C_fish=0.001×100000/1000

Result: C_fish=0.1 μg/kg → eagle with BMF=3: 0.3→0.9 μg/kg

DDT food chain magnification example

Example 2: Methylmercury: BCF~50000, Cw=0.0001μg/L

C_fish=5 μg/kg

Result: Above FDA action level of 1 μg/g = 1000 μg/kg? No — but accumulates

Tuna advisories from methylmercury

Example 3: Four trophic levels

BCF 100,000 into small fish, BMF 3 at each of three steps

Result: 27× concentration in the top predator

Multiplication across levels is what makes top predators the sentinel species for persistent organic pollutants.

Example 4: Lipophilic but not bioaccumulative

Compound with log K_ow = 6 but rapidly metabolised

Result: Low measured BCF

Metabolism clears it faster than it accumulates. This is why measured BCF is required rather than estimates from log K_ow alone.

Common Mistakes

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Using BCF where BAF is appropriate

BCF measures uptake from water only. For strongly lipophilic compounds, dietary intake dominates in the field and BAF is substantially higher.

⚠️

Assuming lipophilicity alone predicts accumulation

Metabolism matters as much. A compound organisms can readily break down will not accumulate regardless of its log K_ow.

⚠️

Ignoring trophic multiplication

A modest BMF becomes extreme over several levels. Assessing risk at one trophic level understates exposure for top predators.

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Applying fish BCF values to mammals or birds

Uptake and elimination differ substantially between taxa. Fish BCF is measured for gill uptake and does not transfer directly.

Frequently Asked Questions

BCF vs BAF vs BMF?

BCF (bioconcentration factor): from water only. BAF (bioaccumulation factor): all routes including food. BMF (biomagnification factor): ratio between trophic levels. BAF = BCF × BMF^(trophic level). Top predators show highest concentrations.

Regulatory significance?

EU: BCF>2000 L/kg triggers PBT (persistent, bioaccumulative, toxic) screening. US EPA: BCF>1000 = bioaccumulative. PFAS and legacy POPs: high BCF because fluorine and halogen bonds resist biodegradation.

What is the difference between BCF, BAF and BMF?

BCF is uptake from water only, measured in the laboratory. BAF includes dietary uptake and is measured in the field. BMF is the concentration increase from prey to predator.

What BCF value triggers regulatory concern?

Above 1,000 L/kg is generally considered bioaccumulative and above 5,000 very bioaccumulative, though exact thresholds vary by jurisdiction.

Why do top predators have the highest concentrations?

Because biomagnification multiplies at each trophic step. Three steps at a factor of three each gives a 27-fold increase over the first level.

Does high log K_ow guarantee bioaccumulation?

No. Metabolic clearance can prevent accumulation even for very lipophilic compounds, which is why measured BCF is preferred over estimates.

Formula Explorer connections

Interpretation: This formula connects molecular properties, material structure or environmental transport to a macroscopic behavior or exposure estimate. Assumption: Use parameters measured for the same material, solvent, temperature and environment. Empirical correlations may not transfer outside their calibration range.

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