Hormesis-induced gap between the guidelines and reality in ecological risk assessment

Guidelines of ecological risk assessment (ERA) used worldwide, based on S-shaped threshold dose-response curve, fail to consider hormesis, a biphasic dose-response model represented as a J-shaped or an inverted U-shaped curve, that occurs in real-life environment. Now that humans are routinely exposed to chemicals below the threshold where hormetic stimulation prevails, it is noteworthy that over-strictness about chemical control also means a waste of limited resources. So hormesis leads to the gap between guidelines with S-shaped model and reality with hormesis model concerning ERA. In this study, hormetic effects of sulfachloropyridazine (SCP) on the bioluminescence of Aliivibrio fischeri ( A. f ) under 41 conditions to simulate the real environment were investigated and compared with ERA practice by some parameters, such as no observed effect concentration (NOEC), hormetic-stimulatory range (HSR) and goal concentration (GC). Not only is the reproducibility of hormesis in real-life contexts confirmed, binomial distribution (p = 0.644 > 0.05) of the relative position of GC and HSR is also found, revealing a 50% probability for GC to falls in HSR, which proves the over-strictness of ERA both qualitatively and quantitatively. This study provides a novel view for ERA that hormetic principles should dominate, and conditions where S-shaped dose-response model works should be singled out on a specific basis to bridge the hormesis-induced gap.