Abstract:A risk assessment on zinc and zinc compouns was carried out withn the framework of Council Regulation 793/93/EEC on Existing Chemicals. This risk assessment basically followed the European Union (EU) technical guidance documents (TGDs). These TGDs are built on the current knowledge on quantitative risk assessments, mainly for organic chemicals. This article describes the tailor-made approach for the zinc risk assessment. This work lasted almost a decade and involved the contributions of all EU member states an… Show more
“…Such assessment factors can range from the division of toxicity test statistics (e.g. EC x (concentration needed for x% effect), no observed effect concentration) by a factor of 1000 down to division by a factor of 3 [29,30]. The observed greater-than-10-fold increase in sensitivity from P generation nematodes to the multigenerationally Ag-PVP-and AgNO 3 -exposed cohorts challenges this assessment factor-based approach.…”
The effects from multigenerational exposures to engineered nanoparticles (ENPs) in their pristine and transformed states are currently unknown despite such exposures being an increasingly common scenario in natural environments. Here, we examine how exposure over 10 generations affects the sensitivity of the nematode Caenorhabditis elegans to pristine and sulfidized Ag ENPs and AgNO 3 . We also include populations that were initially exposed over six generations but kept unexposed for subsequent four generations to allow recovery from exposure. Toxicity of the different silver forms decreased in the order AgNO 3 , Ag ENPs and Ag 2 S ENPs. Continuous exposure to Ag ENPs and AgNO 3 caused pronounced sensitization (approx. 10-fold) in the F2 generation, which was sustained until F10. This sensitization was less pronounced for Ag 2 S ENP exposures, indicating different toxicity mechanisms. Subtle changes in size and lifespan were also measured. In the recovery populations, the sensitivity to Ag ENPs and AgNO 3 resulting from the initial multigenerational exposure persisted. Their response sensitivity for all endpoints was most closely related to the last ancestral exposed generation (F5), rather than unexposed controls. The mechanisms of transgenerational transfer of sensitivity are probably organized through the epigenome, and we encourage others to investigate such effects as a priority for mechanistic toxicology.
“…Such assessment factors can range from the division of toxicity test statistics (e.g. EC x (concentration needed for x% effect), no observed effect concentration) by a factor of 1000 down to division by a factor of 3 [29,30]. The observed greater-than-10-fold increase in sensitivity from P generation nematodes to the multigenerationally Ag-PVP-and AgNO 3 -exposed cohorts challenges this assessment factor-based approach.…”
The effects from multigenerational exposures to engineered nanoparticles (ENPs) in their pristine and transformed states are currently unknown despite such exposures being an increasingly common scenario in natural environments. Here, we examine how exposure over 10 generations affects the sensitivity of the nematode Caenorhabditis elegans to pristine and sulfidized Ag ENPs and AgNO 3 . We also include populations that were initially exposed over six generations but kept unexposed for subsequent four generations to allow recovery from exposure. Toxicity of the different silver forms decreased in the order AgNO 3 , Ag ENPs and Ag 2 S ENPs. Continuous exposure to Ag ENPs and AgNO 3 caused pronounced sensitization (approx. 10-fold) in the F2 generation, which was sustained until F10. This sensitization was less pronounced for Ag 2 S ENP exposures, indicating different toxicity mechanisms. Subtle changes in size and lifespan were also measured. In the recovery populations, the sensitivity to Ag ENPs and AgNO 3 resulting from the initial multigenerational exposure persisted. Their response sensitivity for all endpoints was most closely related to the last ancestral exposed generation (F5), rather than unexposed controls. The mechanisms of transgenerational transfer of sensitivity are probably organized through the epigenome, and we encourage others to investigate such effects as a priority for mechanistic toxicology.
“…In fact, heavy metals have a significant toxicity for humans, animals, microorganisms and plants (Wagner 1994;Gaetke and Chow, 2003;HernandezOchoa et al, 2005;Quartacci et al, 2005;Bodar et al, 2006;Fotakis and Timbrell, 2006). Moreover, heavy metals are not subject to degradation processes and therefore remain almost indefinitely in the environment, although the bioavailability of these chemicals can change considerably depending on their interactions with the various soil constituents.…”
a b s t r a c tThe distribution of Cd, Cu, Pb and Zn between a contaminated soil and the tree species Paulownia tomentosa was investigated in a pilot-scale assisted phytoremediation study. The influence of the addition of EDTA, tartrate and glutamate at 1, 5 and 10 mM concentrations on metal accumulation by the plant and on metal mobilization in soil was evaluated. Root/shoot metal concentration ratios were in the range of 3-5 for Zn, 7-17 for Cu, 9-18 for Cd and 11-39 for Pb, depending on the type and concentration of complexing agent. A significant enhancement of metal uptake in response to complexing agent application was mainly obtained in roots for Pb (i.e. 359 mg kg À1 for EDTA 10 mM and 128 mg kg À1 for the control), Cu (i.e. 594 mg kg À1 for glutamate 10 mM and 146 mg kg À1 for the control) and, with the exception of glutamate, also for Zn (i.e. 670 mg kg À1 for tartrate 10 mM and 237 mg kg À1 for the control). Despite its higher metal mobilization capacity, EDTA produced a metal accumulation in plants quite similar to those obtained with tartrate and glutamate. Consequently the concentration gradient between soil pore water and plant tissues does not seem to be the predominant mechanism for metal accumulation in Paulownia tomentosa and a role of the plant should be invoked in the selection of the chemical species taken up. Metal bioavailability in soil at the end of the experiment was higher in the trials treated with EDTA than in those treated with tartrate and glutamate, the latter not being significantly different from the control. These findings indicated the persistence of a leaching risk associated to the use of this chelator, while an increase of the environmental impact is not expected when glutamate and tartrate are applied.
“…Further chemical investigations using equilibrium dialysis confi rmed rapid dissolution of ZnO nanoparticles with a saturation solubility of around 5 to 10 mg/L in our experimental system. Consideration of published species sensitivity distributions (Bodar et al 2005) indicates that 5 mg/L Zn is suffi cient to cause adverse effects to a majority of aquatic species, including invertebrates and fi sh, and not just to sensitive unicellular algae. Thus, the most likely cause of nano (or bulk) ZnO aquatic toxicity is via dissolution and not necessarily through any specifi c particulate effects.…”
Section: Aquatic Chemistry Of Metal Oxide Nanoparticlesmentioning
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