Contaminants of emerging concern and aquatic organisms: the need to consider hormetic responses in effect evaluations

Abstract

Contaminants of emerging concern are widespread in the world’s waters, raising concerns regarding their effects on living organisms. To evaluate the effects of and predict risks associated with such chemicals, dose-response studies are needed, while the nature of the dose-response relationship is critical for the outcomes of such evaluations. Here, we summarize the literature reporting hormetic responses of aquatic organisms to contaminants of emerging concern. Hormesis is a biphasic dose response encompassing stimulatory responses to low doses and inhibitory responses to high doses. We demonstrate that it occurs widely in numerous aquatic organisms exposed to a wide array of contaminants, including nano/microplastics, suggesting potential effects at doses/concentrations that are considerably lower than the traditional toxicological threshold, which cannot be identified or predicted unless hormesis is considered in the study design. To tackle the effects and associated risks of nano/microplastics and other contaminants on aquatic organisms, hormesis should therefore be taken into account early in the design of studies as well as in relevant risk assessments.

Alterations to unionid transformation during agricultural and urban contaminants of emerging concern exposures

“…For these particular CEC mixtures, there may be synergistic or antagonistic effects present that could lead to detrimental effects to transformation at lower and higher concentrations for both agricultural and urban mixtures. Hormetic responses, wherein intermediate doses may be stimulating or therapeutic, are common among chemical stressors and could be at play (reviewed in Calabrese and Baldwin 2001 , Agathokleous et al 2021 ). Hormetic responses contrast with traditional thought on linear impacts of stressor concentration.…”

Polystyrene nanoplastics alter the ecotoxicological effects of diclofenac on freshwater microalgae Scenedesmus obliquus

“…This would increase the interacting components' bioavailability and accumulation, increasing their potential for toxicity. 44 ROS serve as secondary messengers in a variety of cellular activities against environmental stressors. 45 These reactive species could severely harm the cell membrane by peroxidation of polyunsaturated fatty acids and proteins.…”

“…This would increase the interacting components' bioavailability and accumulation, increasing their potential for toxicity. 44…”

Intraspecific variation of two duckweed species influences response to microcystin-LR exposure

“…Furthermore, cyanotoxins did not have linear impacts within both species. Such phenomena of low dose stimulation or general Ushaped, non-linear responses to toxin and toxicant exposure is common among plants and across aquatic taxa (Agathokleous et al, 2021;Calabrese and Blain, 2009). This suggests that the genetic makeup of duckweed populations differentially affect population-level responses to was not certified by peer review) is the author/funder.…”