title: Non-monotonic concentration-response relationship of TiO(2) nanoparticles in freshwater cladocerans under environmentally relevant UV-A light.
abstract: The effects of UV-A on the toxicity of TiO2 nano-particles (NPs) were evaluated using Moina macrocopa and Daphnia magna under environmentally relevant level of UV-A. The waterfleas were exposed to TiO2 NPs with different sizes of ~298nm, ~132nm, or ~72nm for up to 48h, with or without UV-A light. Whole body reactive oxygen species and transcription of antioxidant enzyme genes were measured, as well as the survival of the waterflea. In the presence of UV-A, the survival rates of M. macrocopa significantly decreased in concentration dependent way until ~1mg/L TiO2 NPs, but the survivals were reversed at greater concentrations. This peculiar non-monotonic trend of concentration-response relationship might be explained by changes of particle size under different light conditions. TiO2 NPs within a certain size range could be trapped in the filter apparatus and exert toxicity, and the NPs of greater size were subject to either precipitation or ingestion leading to no or little toxicity. Observed TiO2 toxicity was associated with oxidative stress in the filter apparatus. The results of this study showed that the size change due to UV-A irradiation should be considered in evaluation of ecological risks of TiO2 NP.
authors: Risk Assessment Division, National Institute of Environmental Research, Incheon 404-708, Republic of Korea; Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: koguma74@gmail.com.
authors: Jungkon
authors: J
authors: Kim
authors: Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: leesw515@gmail.com.
authors: Sangwoo
authors: S
authors: Lee
authors: Institute of Health and Environment, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: cjfalswwkd@hanmail.net.
authors: Chul-min
authors: CM
authors: Kim
authors: Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: zizibe711@gmail.com.
authors: Jihyun
authors: J
authors: Seo
authors: Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: elohim@snu.ac.kr.
authors: Yena
authors: Y
authors: Park
authors: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea.. Electronic address: radbong112@gmail.com.
authors: Dongwook
authors: D
authors: Kwon
authors: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea.. Electronic address: baghagy@gmail.com.
authors: Song-Hee
authors: SH
authors: Lee
authors: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea.. Electronic address: taeyoon@hanyang.ac.kr.
authors: Tae-Hyun
authors: TH
authors: Yoon
authors: Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea; Institute of Health and Environment, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: kyungho@snu.ac.kr.
authors: Kyungho
authors: K
authors: Choi
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects* / Q000528:radiation effects*; D005618:Fresh Water / Q000737:chemistry*; D053758:Nanoparticles / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D010316:Particle Size; D014025:Titanium / Q000633:toxicity*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium
keywords: Filter apparatus; Non-monotonicity; Oxidative stress; Reactive oxygen species