Project topics and materials
Get Complete Project Material File(s) Now! »
Toxicity threshold of triclosan
Ecotoxicity data are indispensable for the elucidation of biocide occurrences in the environment. Acute and chronic effects can be considered as common measures of toxicity. Threshold values for acute toxicity of TCS in fish have been determined to range from 260,000 to 602,000 ng L-1 (Ishibashi et al., 2004; Orvos et al., 2002) whereas chronic effect thresholds were in the range of 71,300 – 290,000 ng L-1 (Orvos et al., 2002; Tatarazako et al., 2004). Acute toxicity threshold values in crustaceans were determined to range from 390,000 ng L-1-125,000,000 and chronic toxicity was observed at levels as low as 6,000 – 440,000 ng L-1 (Memmert, 2006; Orvos et al., 2002). Toxic concentrations of TCS to algae were also in the parts-per-billion range, with values of 200 – 2,800 ng L-1 (Samsøe-Petersen et al., 2003; Yang et al., 2008). Inhibitory effects on microorganisms were shown to begin at levels ranging from 25,000 – 80,000,000 ng L-1 for TCS (Farré et al., 2008; Stasinakis et al., 2007; Stickler et al., 2008).
In one study, a chronic predicted no-effect concentration (PNEC) of 1,550 ng L-1 was determined for TCS by the species sensitivity distribution (SSD) approach which was based on toxicity data for 14 aquatic species. This study then suggested that TCS concentrations could be between 850 ng L-1 without in-stream removal and 250 ng L-1 with in-stream removal in U.S. surface waters (Capdevielle et al., 2008). Moreover, as the concentration of TCS increases, there is a possibility of adaption of bacterial strains by developing resistance (Stickler et al., 2008).
Researchers in Spain conducted another environmental risk assessment for 26 PPCPs (de García et al., 2014). They employed Microtox acute ecotoxicity tests and activated sludge respirometry assays. The quantitative structure-activity relationship (QSAR) program was also utilized to predict the estimated ecotoxicological effects. Based on the results of ecotoxicity tests, TCS was found to be very toxic to different species. Furthermore, evaluation of persistence, bioaccumulation and ecotoxicity (PBT) revealed that TCS is persistent and toxic but not bioaccumulative (de García et al., 2011).
Triclosan has been shown to exert deleterious effects towards different somatic and reproductory mammalian cells at extracellular concentrations of <1,000,000–5,000,000 ng L-1. It also had adverse effects on cells that are non-renewable (pancreatic β-cells). TCS is a mitochondrial toxic chemical which may cause unexpected long-term toxic effects depending on its tissue distribution and elimination (Ajao et al., 2015).
Therefore it is evident that aquatic species such as algae, invertebrates and certain types of fish are much more sensitive to TCS than mammals. Specifically, algae is highly sensitive indicator organism that may be impacted by TCS occurrences in surface waters at levels of 200 – 2,800 ng L-1, where the worldwide concentration has been found to range from 1.4 – 40,000 ng L-1 (Dhillon et al., 2015; SCCS, 2010). Reported toxicity of TCS to aquatic organisms is summarized in Table 3. Acute and chronic toxicity data relating to TCS are also provided in Table 4 and Table 5.
Legal limit of triclosan
Triclosan is an anti-microbial and preservative agent added to personal care products (soap, lotions, toothpaste, detergent and skin care creams) at a typical concentration in the range of 0.1 – 0.3% (w/w) which is regulated by the European Community Cosmetic Directive or the US Food and Drug Agency (U.S. FDA) in Europe and the USA, respectively (Rodricks et al., 2010; Sabaliunas et al., 2003). The content of TCS in household products should not exceed 0.3% (w/w) (Allmyr et al., 2006).
The Minnesota Department of Health (MDH) developed a guidance value of 50 ppb for triclosan in drinking water. A person drinking water at or below this level, would have little or no risk of any health effects from triclosan (« Toxicological Summary: Triclosan, » 2010). The Canadian Federal Water Quality Guideline for the protection of aquatic life from adverse effects of triclosan is 380 ng L-1 (Canadian Environmental Protection Act, 2017).
Chapter 1 Background and Motivation
1.1 Problem statement and motivation
1.2 Aims and objectives of the thesis
1.2.1 General aim of the thesi
1.2.2 Objectives .
1.4 References
Chapter 2 Introduction
2.1 Background
2.2 Quantum dots (QDs)
2.3 Core/shell nanoparticles.
2.4 Toxicity consideration
2.5 Synthesis of QD
2.5.1 Organometallic synthesis of QDs
2.5.1.1 Water-solubilisation of QDs
2.5.2 Wet chemistry
2.6. Comparison of aqueous and organometallic synthetic approaches
2.7 Characterization techniques
2.7.1 Ultraviolet-visible absorption spectroscopy (UV/Vis)
2.7.2 Fluorescence spectroscopy
2.7.3 Powder X-ray diffraction (XRD)
2.7.4 Fourier-transform infrared spectroscopy analysis (FT-IR)
2.7.5 High resolution transmission electron microscopy analysis (HRTEM)
2.7.6 High resolution scanning electron microscopy analysis (HRSEM)
2.7.8 Energy-dispersive X-ray spectroscopy analysis (EDS)
2.7.9 Thermogravimetric analysis (TGA)
2.8 QDs utilized in this work
2.9 Application of CdSe/ZnS QDs in fluorescence sensing
2.10 Fluorescence quantum yield
2.11 Principle of optical sensing using QDs
2.12 Molecularly imprinted polymers (MIPs)
2.13 Mechanisms involved in MIP preparation
2.14 Polymers utilized in this work
2.14.1 Functional monomers .
2.14.2 Cross linkers
2.14.3 Template
2.15 Principle of optical sensing using MIP-capped QDs (MIP@QDs)
2.16 Toxicity of triclosan
2.17 Toxicity of acetaminophen
2.18 References .
Chapter 3 Literature Review
3.1 Paper 1
3.2 Paper 2
Chapter 4 Experimental Methods, Results and Discussion
4.1 Paper 3
4.1.1 Paper 3 – Supplementary information .
4.2 Paper 4
4.2.1 Paper 4 – Supplementary information
4.3 Paper 5
4.3.1 Paper 5 – Supplementary information
Chapter 5 Overal Conclusions and Future Work
5.1 Overal conclusions
5.2 Future work
5.3 Reference
Appendices
