ABSTRACT
This study was conducted to investigate the toxicity of Titanium Oxide [TiO2] and Zinc Oxide [ZnO] nanoparticles as two of most widely used nanoparticles. The result of this study can help to designing environmental standard and legislations for nanoparticles. Different concentrations of nano ZnO and TiO2 nanoparticles were added to nutrient Agar culture media. Then, definite numbers of Escherichia coli and Staphylococcus aureus bacteria were added to culture media and inhibition of these bacteria growth was measured in comparison to controls. Obtained data were analyzed to determine nanoparticles' EC50 and NOEC [No Observed Effect Concentration] using SPSS ver.16 and Probit standard test. 24-hours EC50 of nano ZnO using E. coli and S. aureus determined to be 5.47 mg/L and 2.38 mg/L respectively. In addition, 24-hours EC50 of nano TiO2 using E. coli and S. aureus determined to be 5366 mg/L and 3471 mg/L respectively. In the case of ZnO nanoparticles, no observed effect concentration determined to be 1.15 and 3.28 mg/L for E. coli and S. aureus respectively and in the case of TiO2 nanoparticles no observed effect level determined to be 1937 and 1184 mg/L for E. coli and S. aureus respectively. This study showed that acute toxicity of nano ZnO is by farmore than that of nano TiO2. Regarding the EPA acute toxicity criteria, nano ZnO is categorized as moderately toxic and nano TiO2 is categorized as practically non toxic. Hence, regarding the acute toxicity, in recommending exposure criteria and environmental disposal standards, compared to nano TiO2, nano ZnO requires more attention
ABSTRACT
Specific and unique characteristics of nanoparticles may entail specific and unique hazards. In addition, they may also exhibit toxicity under certain conditions. This study was conducted to investigate the toxicity of phenol-exposed and phenol-unexposed nano-TiO[2] and nano-Fe/TiO[2] particles. Stock solutions of the afore-mentioned nanoparticles were prepared at different concentrations and a sample of each was exposed to phenol. This was followed by exposing Daphnia Magna to the phenol- and non-phenol-exposed nanoparticles. LC[50], NOEC and the concentrations at which mortality rates were 100% were determined 12 to 96 hours after exposure, while for the determination of the mortality rate of Daphnia the Probit model in SPSS version16 software was used. The results revealed that [1]. The 48-hr LC[50] values for phenol-unexposed nano-TiO[2] and nano-Fe/TiO2 particles were 2705 and over 15000 mg/m[3], respectively. The corresponding values for the phenol-exposed samples were 414 and 1253. [2]. The 48-hr NOEC values for the phenol-exposed TiO[2] and FeTiO[2] were 41 and 789, respectively, the corresponding values for unexposed samples being 1253 and over 15000 mg/m[3]. [3]. In addition, the 48-hr 100% mortality rates for phenol-unexposed nano-TiO[2] and nano-Fe/TiO2 particles were, respectively, 1253 and over 15000 mg/m[3], while for the phenol-exposed samples the corresponding rates were 1090 and over 2108. With regard to 48-hr LC[50], the findings show that the toxicity of both nano-Fe: TiO[2] and TiO[2] increases as a result of exposure to phenol, the increase being 12-fold for the former and 6.5-fold for the latter. In general, however, based on LC[50], it can be said that the toxicity of Fe:TiO2 nanoparticles, which has better catalytic characteristics, is lower in comparison to TiO[2] nanoparticles. Thus, using Fe:TiO2 in preference to pure TiO[2] should be investigated further, as it will be less hazardous to the environment