Abstract
Nanomaterials (NMs) are recommended to be tested in longer term exposures. Multigenerational (MG) studies are scarce and particularly important because effects can be transferred to the next generation. The current risk assessment framework does not include MG effects and this is a caveat for persistent materials. Here, the effects of copper NMs (CuONMs) and copper salt (CuCl2) were assessed in a MG exposure (4 generations in spiked soil + 2 generations in clean soil, F1 to F7 generations in total), with the standard soil model Enchytraeus crypticus, using relevant reproduction test effect concentrations (EC10, EC50), monitoring survival and reproduction. This represented ca. 1 year continuous exposure tests. MG effects varied with effect concentration and test materials: CuONMs caused increased toxicity for EC10 exposed organisms (EC50 did not change), and transfer to clean media reset effects, whereas CuCl2 reduced toxicity for EC10 and EC50, but the transfer to clean media “revived” the initial effects, i.e. close to EC50 levels in F7. Clearly CuONMs and CuCl2 cause different mechanisms of toxicity or response in the long term, not predictable based on short term or one generation studies. The present contributes for the improvement of risk assessment, adding important information for the long term exposure and effects.
Highlights
Continuous multigenerational (MG) exposure to chemicals may induce physiological adaptations such as increased tolerance[1, 2]
In the present study we aimed to investigate the effects of MG exposure to copper oxide NMs (CuONMs) and copper salt (CuCl2), using E. crypticus, a soil model representative[21,22,23]
Results for reproduction show that the selected EC10 and EC50 values were approximately confirmed in F1: this corresponded for CuONMs to 8% (±2.9) and 44% (±1.5) reduction, for CuCl2 to 12% (±4.4) and 44% (±2.6) reduction respectively
Summary
Continuous multigenerational (MG) exposure to chemicals may induce physiological adaptations such as increased tolerance[1, 2]. Adaptation can involve change in organisms’ genetic material, where e.g. most tolerant genes can be selected[4, 7]. This change in population genetics can be preserved along generations even when the stressor is removed[4]. Other studies, where only the parental generation was exposed, show transgenerational transfer of sensitivity[9]. There are studies with Caenorhabditis elegans[14] performed in simulated pore water (SPW), agar or agar media (instead of soil) studying the effects of gold NMs, the parental generation was exposed, showing increased toxicity in second (unexposed) generation, transgenerational effects. There are no MG effect studies performed for NMs
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