Hormesis induced by persistent organic pollutants: Mechanisms, ecological implications, and challenges for risk...

Increasing research suggests that low-dose persistent organic pollutants (POPs) can elicit hormetic stimulatory effects on organisms, highlighting the need for a comprehensive synthesis of the literature to evaluate the prevalence, mechanisms, and implications of these non-linear responses. This review consolidates evidence supporting the hypothesis that hormesis describes a common and evolutionarily conserved adaptive strategy, consistently observed across a broad spectrum of POPs. The hormetic response of whole-organism endpoints such as growth is primarily driven by initial mild oxidative stress, which activates sophisticated adaptive signaling pathways, coordinated overexpression of defensive machinery, induction of antioxidant enzymes, and activation of detoxification pathways involving phase I/II enzymes. These responses are often transient and context-dependent, often influenced by exposure duration and other environmental factors, and thus may play a fundamental role as a dynamic survival strategy. The vast concentration range of stimulations, spanning several orders of magnitude (from nanograms to milligrams), suggests the broad environmental relevance of POP-induced hormesis. Hence, the widespread occurrence of POP-induced hormesis presents a significant challenge to conventional risk assessment frameworks, creating an urgent need to integrate these biphasic dose-response relationships into developing more accurate ecological and human health risks of POPs exposure.