ORIGINAL RESEARCH
Investigating the Toxicity of Phenol-Loaded
and Phenol-Free TiO2 and ZnO Nanoparticles
Using Bioassay Experiments
Kazem Naddafi1, Masoud Yunesian1, Mahmood Alimohammadi1, Noushin Rastkari1, Mohammad Reza Zare1, Mina F. Banadarvish2
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1Department of Environmental Health Engineering, School of Public Health,
Tehran University of Medical Sciences, Tehran, Iran
2University of British, Columbia, Vancouver, Canada
Pol. J. Environ. Stud. 2014;23(6):2143-2148
KEYWORDS
ABSTRACT
This study investigates the potential toxicity of TiO2 and ZnO nano-particles (nano-TiO2 and nano-ZnO)
against Daphnia magna (D. magna) neonates before and after absorbing phenol. Although limited scientific
investigation is conducted on possible hazards of nano-particles (NPs), no research has been carried out either
on the toxicity of nano-ZnO and TiO2 in combination with other materials or on their ability to release the hazardous
substances adsorbed on their surface in cells.
Daphnia magna neonates exposed to different concentrations of phenol-free and phenol-loaded NPs and
resulting mortality rates were recorded after 12 to 96 h. The results of mortality rates were applied to SPSS
ver. 16.0 in order to calculate median lethal concentrations (LC50) of NPs.
The results of experiments showed that phenol-free TiO2 was “practically nontoxic” according to EPA
overview (48 h LC50: 2705 mg·L-1). But after exposure to phenol, its 48 h LC50 reached 414 mg·L-1, which
means a 6-time increment in toxicity. 48 h LC50 of phenol-loaded and phenol-free nano-ZnO was 2.14 and
2.18 mg·L-1, respectively.
This study showed, in contrast to nano-TiO2, that no significant difference is found between the toxicity
of nano-ZnO before and after exposure to phenol. Researchers considered the amount of toxin absorbability
of NPs to be one of the most important factors influencing the change in NP toxicity.