Back to Top

Extrapolated EC50 data and QSARs in calculation of new CFs and interpretation of trophic levels

4 posts / 0 new
Last post
Maria's picture
Extrapolated EC50 data and QSARs in calculation of new CFs and interpretation of trophic levels

I know that USEtox recommends measured EC50 data in calculation of new CFs. But when EC50 data is scarce, what is your recommendation regarding using other datasets, for example extrapolated EC50s from NOEC or LOEC (since EC50 is highyl correlated to those: Payet, 2004) or EC50s based on QSARs? 

I also wonder is LC50 is the same as EC50 with mortality as endpoint, and thus if LC50s can be used? For example, for fish, I have only found one measured EC50 data for over 20 chemicals under investigation, when searching 5+ different databases while LC50 is a very common endpoint for fish.

In additions USEtox recommends at least 3 different trophic levels. Could you please clarify what you mean by that? I would say that algae and aquatic plants belong to the same trophic levels, but at the same time they belong to two different phyla (or taxa) so do they count as one or two?

USEtox Team
USEtox Team's picture
Thank you for your questions.

Thank you for your questions.

When measured EC50 data are not available, we recommend to use as second option an extrapolation from NOEC/LOEC or QSARs. In such cases, it is worth mentioning the uncertainties related to this though along with the results.

Within USEtox®, we also use LC50 values as a type of EC50 values.

As for the trophic levels, our recommendations are based on the study of Larsen and Hauschild (2007).

hannaholmquist's picture
Extrapolation factor between chronic NOEC and chronic EC50?


In the answer to the quesion above it is stated that the second option to exprimetal chronic EC50 values is an extrapolation from NOEC/LOEC (chronic I assume). I wonder if this is correct and if so wat extrapoltion facor to use? In the USEtox 2 manual it is stated that "second priority is given to acute data, applying a acute-to-chronic extrapolation factor..."


Thank you in advance!

USEtox Team
USEtox Team's picture
Extrapolated data for human toxicity and ecotoxicity

For human toxicity, USEtox already used an extrapolation from NOAEL and/or LOAEL to ED50. For ecotoxicity, such extrapolation is currently in progress and wil most likely help extrapolating data from NOEC and/or LOEC to EC50. Meanwhile, it is indeed recommended currently for ecotoxicity to extrapolate from acute EC50 data unless specific regressions from chronic NOEC/LOEC data are available.