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Related Experiment Videos

The linear no-threshold model is less realistic than threshold or hormesis-based models: An evolutionary perspective.

David Costantini1, Benny Borremans2

  • 1UMR 7221 CNRS/MNHN, Muséum National d'Histoire Naturelle, Sorbonne Universités, 7 rue Cuvier, 75005, Paris, France; Behavioural Ecology & Ecophysiology Group, Department of Biology, University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium.

Chemico-Biological Interactions
|October 21, 2018
PubMed
Summary

The linear no-threshold (LNT) model for risk assessment is questioned. Hormetic models, supported by ecophysiology and evolutionary ecology, offer greater biological validity for stressor effects on organisms.

Keywords:
ConditioningEvolutionHormesisOxidative stressRadiationStress

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Area of Science:

  • Environmental Toxicology
  • Ecology
  • Evolutionary Biology

Background:

  • The linear no-threshold (LNT) model is the standard for human health risk assessment.
  • LNT assumes low-dose responses can be extrapolated from high-dose effects.
  • Recent observations challenge LNT's validity due to differing high- and low-dose responses.

Purpose of the Study:

  • To review the biological and evolutionary validity of the LNT risk model.
  • To compare LNT with threshold and hormetic models for stochastic biological effects.
  • To explore the plausibility of hormesis using a mathematical model.

Main Methods:

  • Literature review focusing on ecophysiology and evolutionary ecology.
  • Analysis of studies showing impacts of moderate stressor exposure on phenotype and fitness.
  • Development of a mathematical model for conditioning hormesis.

Main Results:

  • The LNT model shows limited biological validity for low and moderate stressor levels.
  • Threshold and particularly hormetic models demonstrate greater biological relevance.
  • Moderate stress exposure can significantly impact organismal fitness and phenotype.

Conclusions:

  • Hormetic models are more biologically and evolutionarily valid than LNT for risk assessment.
  • Conditioning hormesis is presented as an ecologically and evolutionarily plausible phenomenon.
  • The findings necessitate a re-evaluation of current risk assessment paradigms.