Progress in the studies on hormesis of low-dose pollutants

Abstract

Hormesis can be defined as a biphasic dose-response relationship characterized by low-dose simulation and high-dose inhibition. Given that environmental pollutants are more often found at lower doses, hormesis research has become a recent hot spot in toxicology. This study summarizes current progress on hormesis research, which can be discussed in three contexts: The universality of hormesis, hormesis mechanisms, and the quantification of hormetic responses. The universality of hormesis has been verified, but the degree to which hormesis should be taken into risk assessments and risk management plans remains controversial. Regarding mechanisms, we discuss how our mechanistic understanding of hormesis has come a long way but still lacks strong experimental support, which leads to uncertainty as to the exact underlying causes of hormesis. This study also describes the hormesis quantitative research process and points out that due to an incomplete mechanistic understanding of hormesis, quantitative research has progressed slowly and lacks accurate quantitative characterization parameters and prediction models. Finally, we discuss that a future trend may be to investigate hormesis quantitative characterization parameters based on toxicity mechanism and to establish a quantitative prediction model of hormesis that incorporates those parameters.