T3 AM Ecological Risk Assessment (Part 2)
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in Ballroom 3

(BEC-1117-063231) A general dose-response model encompassing hormesis.

Beckon, W¹, Parkins, C², Maximovich, A³, Beckon, A⁴, ¹ U. S. Fish and Wildlife Service, Sacramento, CA, USA² Inspironix, Sacramento, USA³ Saint Petersburg State University, Saint Petersburg, Russian Federation⁴ Pomona College, Claremont, USA

ABSTRACT- Hormesis -- causing an adverse effect on organisms at high doses but causing a beneficial effect on the same organisms at lower doses -- is a ubiquitous but inadequately modeled phenomenon. Accurate modeling of hormesis is an essential step in establishing effective guidelines for the protection of human and ecosystem health, yet currently-used mathematical dose-response models of hormesis lack biological rationale and fit only limited sets of hormetic data. To model hormetic dose-response relationships more closely over a wider spectrum of data, we suggest a simple, biologically reasonable conceptual model of hormesis leading to a mathematical equation employing parameters, such as ED₅₀, that are useful to pharmacologists and toxicologists. This mathematical model can be used to test for the presence of hormesis, and it simplifies to the standard log-logistic function in the special case where no hormetic effect can be detected.

Key words: dose-response, hormesis, nonmonotonic, model