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  • 1
    Article
    Article
    Biological Surface Coating and Molting Inhibition as Mechanisms of TiO 2 Nanoparticle Toxicity in Daphnia magna (Mechanisms of nTiO2 Toxicity to D. magna) (2011)
    Details
    Language: English
    In: PLoS ONE, 2011, Vol.6(5), p.e20112
    Description: The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (∼100 nm initial mean diameter) titanium dioxide (nTiO 2 ) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC 50 ) and 0.73 mg/L (96-h EC 50 ). However, nTiO 2 disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC 50 ) based on measured concentrations. Moreover, we showed that nTiO 2 (∼100 nm) is significantly more toxic than non-nanosized TiO 2 (∼200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO 2 toxicity in D. magna that involves the coating of the organism surface with nTiO 2 combined with a molting disruption. Neonate D. magna (≤6 h) exposed to 2 mg/L nTiO 2 exhibited a “biological surface coating” that disappeared within 36 h, during which the first molting was successfully managed by 100% of the exposed organisms. Continued exposure up to 96 h led to a renewed formation of the surface coating and significantly reduced the molting rate to 10%, resulting in 90% mortality. Because coating of aquatic organisms by manmade NP might be ubiquitous in nature, this form of physical NP toxicity might result in widespread negative impacts on environmental health.
    Keywords: Research Article ; Biology ; Chemistry ; Earth Sciences ; Materials Science ; Medicine ; Chemistry ; Public Health And Epidemiology ; Marine And Aquatic Sciences ; Ecology ; Critical Care And Emergency Medicine ; Science Policy ; Biochemistry ; Non-clinical Medicine
    E-ISSN: 1932-6203
    DOI: 10.1371/journal.pone.0020112
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  • 2
    Article
    Article
    Effects of nano-TiO 2 in combination with ambient UV-irradiation on a leaf shredding amphipod (2011)
    Details
    Language: English
    In: Chemosphere, 2011, Vol.85(10), pp.1563-1567
    Description: ► Effects of nTiO and ambient UV-irradiation affect representatives of detrital food webs. ► Accumulation of nTiO at the bottom of the test vessel seems to affect ecotoxicity. ► nTiO and ambient UV-irradiation increases ecotoxicity due to the formation of ROS. Production and use of engineered nanoparticles, such as titanium dioxide nanoparticles (nTiO ), is increasing worldwide, enhancing their probability to enter aquatic environments. However, direct effects of nTiO as well as ecotoxicological consequences due to the interactions of nTiO with environmental factors like ultraviolet (UV) irradiation on representatives of detrital food webs have not been assessed so far. Hence, the present study displayed for the first time adverse sublethal effects of nTiO at concentrations as low as 0.2 mg L on the leaf shredding amphipod both in presence and absence of ambient UV-irradiation following a 7-d exposure. In absence of UV-irradiation, however, the effects seemed to be driven by accumulation of nTiO at the bottom of the test vessels to which the gammarids were potentially exposed. The adverse sublethal and lethal effects on gammarids caused by the combined application of nTiO and ambient UV-irradiation are suggested to be driven by the formation of reactive oxygen species. In conclusion, both the accumulation of nTiO at the bottom of the test vessel and the UV induced formation of reactive oxygen species clearly affected its ecotoxicity, which is recommended for consideration in the environmental risk assessment of nanoparticles.
    Keywords: Nanoparticle ; Titanium Dioxide ; Ultraviolet Irradiation ; Gammarus Fossarum ; Accumulation ; Reactive Oxygen Species ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
    DOI: 10.1016/j.chemosphere.2011.07.060
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  • 3
    Article
    Article
    Nanoparticle toxicity in Daphnia magna reproduction studies: The importance of test design (2013)
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    Language: English
    In: Aquatic Toxicology, 15 January 2013, Vol.126, pp.163-168
    Description: ► nTiO concentrations one order of magnitude above the PEC caused adverse chronic effects. ► Particle size and product composition, i.e. crystalline structure, trigger differences in nTiO toxicity. ► nTiO accumulation at the bottom of the test vessel is an important effect pathway. ► Dissolved organic carbon influences fate and finally nTiO toxicity. The increasing use of titanium dioxide nanoparticles (nTiO ) inevitably results in their release into the environment, raising concerns about potential adverse effects in wildlife. By following standard test protocols, several studies investigated the ecotoxicity of nTiO among others to . These studies indicated a large variability – several orders of magnitude – in the response variables. However, other factors, like nanoparticle characteristics and test design, potentially triggering these differences, were largely ignored. Therefore, the present study assessed the chronic ecotoxicity of two nTiO products with varying crystalline structure (A-100; P25) to . A semi-static and a flow-through exposure scenario were compared, ensuring that both contained environmentally relevant concentrations of dissolved organic carbon. Utilizing the semi-static test design, a concentration as low as 0.06 mg/L A-100 (∼330 nm) significantly reduced the reproduction of daphnia indicating environmental risk. In contrast, no implication in the number of released offspring was observed during the flow-through experiment with A-100 (∼140 nm). Likewise, P25 (∼130 nm) did not adversely affect reproduction irrespective of the test design utilized. Given the present study's results, the particle size, the product composition, i.e. the crystalline structure, and the accumulation of nTiO at the bottom of the test vessel – the latter is relevant for a semi-static test design – may be suggested as factors potentially triggering differences in nTiO toxicity to . Hence, these factors should be considered to improve environmental risk assessment of nanoparticles.
    Keywords: Inorganic Nanoparticles ; Reproduction ; Growth ; Flow-through ; Crustacea ; Chemistry ; Ecology
    ISSN: 0166-445X
    E-ISSN: 1879-1514
    DOI: 10.1016/j.aquatox.2012.10.015
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  • 4
    Article
    Article
    Does the presence of titanium dioxide nanoparticles reduce copper toxicity? A factorial approach with the benthic amphipod Gammarus fossarum (2015)
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    Language: English
    In: Aquatic Toxicology, August 2015, Vol.165, pp.154-159
    Description: In aquatic ecosystems, titanium dioxide nanoparticles (nano-TiO ) may adsorb co-occurring chemical stressors, such as copper (Cu). This interaction has the potential to reduce the concentration of dissolved Cu due to surface binding to the nanoparticles. The subsequent sedimentation of nano-TiO agglomerates may increase the exposure of benthic species towards the associated Cu. This scenario was assessed by employing the amphipod as model species and taking advantage of a 2 × 2-factorial design investigating absence and presence of 2 mg nano-TiO /L and 40 μg Cu/L ( = 45; = 24 d) in darkness, respectively. Nano-TiO alone did not affect mortality and leaf consumption, whereas Cu alone caused high mortality (〉70%), reduced leaf consumption (25%) and feces production (30%) relative to the control. In presence of nano-TiO , Cu-induced toxicity was largely eliminated. However, independent of Cu, nano-TiO decreased the gammarids’ assimilation and weight. Hence, nano-TiO may be applicable as Cu-remediation agent, while its potential long-term effects need further attention.
    Keywords: Heavy Metal ; Benthic Invertebrates ; Energy Processing ; Remediation ; Combined Toxicity ; Chemistry ; Ecology
    ISSN: 0166-445X
    E-ISSN: 1879-1514
    DOI: 10.1016/j.aquatox.2015.05.011
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  • 5
    Article
    Article
    Exposure pathway dependent effects of titanium dioxide and silver nanoparticles on the benthic amphipod Gammarus fossarum (2019)
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    Language: English
    In: Aquatic Toxicology, July 2019, Vol.212, pp.47-53
    Description: The increasing production of engineered inorganic nanoparticles (EINPs) elevates their release into aquatic ecosystems raising concerns about associated environmental risks. Numerous investigations indicate sediments as the final sink, facilitating the exposure of benthic species to EINPs. Although reports of sub-lethal EINP effects on benthic species are increasing, the importance of exposure pathways (either waterborne or dietary) is poorly understood. This study investigates the influence of two EINPs, namely titanium dioxide (nTiO ) and silver (nAg), on the benthic model organism specifically addressing the relative relevance of these pathways. For each type of EINP an individual 30-day long bioassay was conducted, applying a two-factorial test design. The factors include the presence or absence of the EINPs (nTiO : ∼80 nm, 4 mg/L or nAg: ∼30 nm, 0.125 mg/L;  = 30) in the water phase (waterborne), combined with a preceding 6-day long aging of their diet (black alder leaves) also in presence or absence of the EINPs (dietary). Response variables were mortality, food consumption, feces production and energy assimilation. Additionally, the physiological fitness was examined using lipid content and dry weight of the organisms as measures. Results revealed a significantly reduced energy assimilation (up to ∼30%) in induced by waterborne exposure towards nTiO . In contrast, the dietary exposure towards nAg significantly increased the organisms’ energy assimilation (up to ∼50%). Hence, exposure pathway dependent effects of EINPs cannot be generalized and remain particle specific resting upon their intrinsic properties affecting their potential to interact with the surrounding environment. As a result of the different properties of the EINPs used in this study, we clearly demonstrated variations in type and direction of observed effects in . The results of the present study are thus supporting current approaches for nano-specific grouping that might enable an enhanced accuracy in predicting EINP effects facilitating their environmental risk assessment.
    Keywords: Nanomaterial ; Titanium Dioxide ; Silver ; Exposure Pathway ; Chronic Toxicity ; Chemistry ; Ecology
    ISSN: 0166-445X
    E-ISSN: 1879-1514
    DOI: 10.1016/j.aquatox.2019.04.016
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