Benzo[a]pyrene Toxic Equivalent Calculator

Ecology

Convert the measured concentration of a polycyclic aromatic hydrocarbon (PAH) into its benzo[a]pyrene toxic equivalent (BaP-TEQ) using a toxic equivalency factor (TEF). Benzo[a]pyrene is the reference carcinogen with a TEF of 1, and other PAHs are scaled relative to it. Enter the concentration and the TEF to get the equivalent benzo[a]pyrene dose.

Formula

BaP-TEQ = Concentration × TEF
  • The benzo[a]pyrene toxic equivalent (BaP-TEQ) expresses a PAH's carcinogenic potency as an equivalent amount of benzo[a]pyrene.
  • TEQ = concentration × toxic equivalency factor (TEF).
  • Benzo[a]pyrene is the reference compound with a TEF of 1; less potent PAHs have TEFs below 1 (e.g. many are 0.1, 0.01 or 0.001).
  • For a mixture, calculate the TEQ of each PAH and sum them to get the total BaP-TEQ of the sample.
  • TEF values come from regulatory and toxicological sources and can vary between schemes — use the set appropriate to your assessment.
  • Keep concentration units consistent (e.g. ng/m³ in air, or µg/kg in soil/food); the result carries the same unit.

5 ng/m³ of a PAH with TEF 0.1

Inputs
  • PAH Concentration (ng/m³): 5
  • Toxic Equivalency Factor (TEF): 0.1

BaP-TEQ = 5 × 0.1 = 0.5 ng/m³ benzo[a]pyrene equivalent. The PAH contributes the same carcinogenic risk as 0.5 ng/m³ of benzo[a]pyrene.

Frequently asked questions

What is benzo[a]pyrene toxic equivalent?
It expresses the carcinogenic potency of a PAH as an equivalent concentration of benzo[a]pyrene, the reference compound. TEQ = concentration × TEF.
What is a toxic equivalency factor (TEF)?
A TEF scales a compound's toxicity relative to benzo[a]pyrene, which has a TEF of 1. A PAH with TEF 0.1 is one-tenth as potent per unit mass.
How do I handle a mixture of PAHs?
Compute the TEQ for each PAH (concentration × its TEF) and add them together to get the total benzo[a]pyrene-equivalent toxicity of the sample.
Why is benzo[a]pyrene used as the reference?
It's one of the most studied and potent carcinogenic PAHs, so it's the standard benchmark against which other PAHs are weighted.