Year: 2014
Type: dissertation
Abstract: The increasing production and application of carbon nanotubes (CNT), might enhance the presence of this nanomaterial in the aquatic environment, and hence, the exposure of aquatic organisms. Triclocarban (TCC) is a high-production-volume chemical that is widely used as an antimicrobial compound and is known for its toxicity, endocrine disruption, bioaccumulation potential, and environmental persistence. CNT may interact with and further influence the fate and transport of other pollutants such as TCC. As TCC is used since 1957 in huge amounts, and MWCNT is supposed to reach the amount of a large scale production, both substances might involuntarily occur together in the environment. Firstly, three different cell lines (RTL-W1, T47Dluc, H295R) were exposed to multiwalled carbon nanotubes (MWCNT), the antimicrobial agent TCC as well as the mixture of both substances in a concentration range of 3.13 to 50 mg CNT/L and 31.25 to 500 µg TCC/L. The influence of MWCNT and TCC on various toxicological endpoints was specified: neither cytotoxicity, nor endocrine disruption could be observed after exposure of the three cell lines to MWCNT, but the nanomaterial caused intracellular generation of reactive oxygen species (ROS) in all cell types. A decrease of luciferase activity in the ER Calux assay at a TCC concentration of 125 µg/L and higher was observed. This effect was less pronounced when MWCNT were present in the medium. Taken together, these results demonstrate that MWCNT induce the production of ROS in RTL-W1, T47Dluc, and H295R cells, reveal no cytotoxicity and reduce the bioavailability and toxicity of the biocide triclocarban. Additionally, the population test with Daphnia magna was performed over a period of 93 days. The long-term exposure of multiwalled carbon nanotubes (MWCNT) was examined with a concentration of 1 mg CNT/L as of the beginning as well as of day 14, to ensure a stable population at the equilibrium. Additionally, a control population was treated with a 2-day pulse of TCC three times (d 14, d 54, d 68) following exposure to 25 µg TCC/L, 41 µg TCC/L, and 61 µg TCC/L, respectively. Furthermore, a continuously MWCNT treated population was exposed to the same pulses with TCC. The influence of MWCNT and TCC on population level was specified. The total abundance of treated populations did not differ from the control population. Whereas, significantly changes in all three size classes could be observed as a result of the long-term exposure to 1 mg CNT/L: increase of neonates, and decrease of juveniles and adults. Moreover, significantly smaller daphnids were determined when they was exposed to MWCNT from the beginning of the population experiment. The exposure with TCC leads to size-dependent mortality in Daphnia magna populations and a subsequently recovery. The mixture of MWCNT and TCC results in a lower toxicity of TCC up to 41 µg TCC/L. Furthermore, the effects of TCC on population level were compared by using an individual-based Daphnia magna population model (IDamP). The IDamP model with an integrated toxicity module was able to predict the effects of TCC on the population level (in equilibrium) under constant laboratory conditions. The use of a modeling approach offers a tool to extrapolate from effects derived from laboratory experiments to effects on the population level and can improve the ecological risk assessment of chemicals. Finally the uptake and toxicity of MWCNT in the extended fish embryo toxicity test (FET) using wild type and transgenic zebrafish was investigated. Additionally, the mixture toxicity of MWCNT and TCC was considered using wild type zebrafish. Uptake of the nanomaterial in wild type embryos was not observed. Hatching time and hatching success were not affected and no mortality or deformities occurred. These nanoparticles and/or aggregates mainly accumulated on the bottom of the test vessels and remained sedimented in the water phase. No induction of heat shock protein (Hsp) promoter by MWCNT in transgenic zebrafish as well as no toxicity and no adverse effects on development could be determined after exposure to up to 100 mg CNT/L. For TCC on the other hand, mortalities in wild type zebrafish up to 90% could be observed at the highest concentration of 111 µg TCC/L. This mortality was significantly reduced in appearance of 10 mg CNT/L. These results demonstrate that MWCNT are not toxic for zebrafish embryos up to 100 mg CNT/L and reduce the bioavailability and toxicity of the biocide TCC. The findings of this study document that CNT are not acute toxicants but lead to long-term effects in aquatic organisms. This clarify the necessity to investigate not only test endpoints such as the acute toxicity but also focusing systematically on chronic effects after the exposure to this nanoparticles.
Source: RWTH Publications (RWTH Aachen)
Authors: Anne Simon, Henner Hollert
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1007482524