TEF to TEQ Converter

Calculate congener-specific and total reference-equivalent concentration using caller TEFs; all concentrations share one basis and no changing regulatory TEF table is embedded.

Description

Multiply each congener concentration by its supplied toxic-equivalency factor and sum reference-equivalent concentration.

Toxic equivalency factors, or TEFs, express relative potency against a common reference compound for a specified assessment framework. Toxic equivalents, or TEQ, combine concentration contributions on that reference basis. Factor choice depends on the congener set and assessment context.^[1]

This tool performs the weighted concentration sum using the factors you enter. It includes no factor table or automatic WHO-version selection. Concentrations must share a unit and measurement basis, such as pg/g on the same wet-weight or lipid-weight basis; the output retains that unit as reference-equivalent concentration.

When to use TEF to TEQ Converter

Use it to reproduce a TEQ worksheet with documented congener identities, measured concentrations, and a justified factor set.

How to use TEF to TEQ Converter and understand its results

Enter nonempty congenerConcentrations and toxicEquivalencyFactors arrays of equal length in matching congener order.
Use nonnegative finite values, confirm a common reference compound and concentration basis, and record the factor source and version separately.
Run the sum and inspect congenerEquivalentConcentrations and totalEquivalentConcentration to see individual contributions and the total.

equivalent concentration_i = concentration_i × TEF_i; total TEQ = Σ equivalent concentration_i

The tool does not normalize the factors or adjust concentrations between sample bases.

json

{
  "input": {
    "congenerConcentrations": [
      2,
      3
    ],
    "toxicEquivalencyFactors": [
      1,
      0.1
    ]
  },
  "output": {
    "congenerEquivalentConcentrations": [
      2,
      0.30000000000000004
    ],
    "totalEquivalentConcentration": 2.3
  }
}

Zero concentrations and zero factors contribute zero. The implementation accepts factors above one; TEFs are not absorption fractions. Empty lists, unequal lengths, and negative values are rejected.

Limitations and assumptions

No congener lookup, detection-limit substitution, sample-basis conversion, bioavailability correction, or factor uncertainty is included.

A numerically valid sum cannot establish that a factor framework applies to the species, endpoint, route, or mixture. TEQ is not an unweighted chemical concentration or a complete risk assessment.

Alternative or Complementary methods

Check the factor framework before comparing totals. Endpoint-grouped hazard indices and independent-action models answer different mixture questions and should retain their own assumptions and output definitions.

References

The 2022 WHO Reevaluation of Human and Mammalian Toxic Equivalency Factors (DeVito et al., 2024) — Regulatory Toxicology and Pharmacology

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