Species sensitivity and dependence on exposure conditions impacting the phototoxicity of TiO₂ nanoparticles to benthic organisms.
Toxicity of titanium dioxide nanoparticles (nano-TiO2 ) to aquatic organisms can be greatly increased after exposure to ultraviolet (UV) radiation. This phenomenon has received some attention for water column species; however, investigations of nano-TiO2 phototoxicity for benthic organisms are still limited. In the present study, bioassays of 3 representative benthic organisms (Hyalella azteca, Lumbriculus variegatus, and Chironomus dilutus) were conducted to evaluate nano-TiO2 phototoxicity. When exposed to 20 mg/L of nano-TiO2 and various light intensities (0-30 W/m(2)), H. azteca was the most sensitive, with a median lethal dose of 40.7 (95% confidence interval, 36.3-44.7) Wh/m(2), and hence is a potential model organism in future toxicological guidelines for photoactive nanomaterials to freshwater benthos. Without the presence of nano-TiO2 , no mortality was observed in L. variegatus and C. dilutus exposed to UV intensity ranging from 0 W/m(2) to 41 W/m(2). However, a sharp drop of H. azteca survival was observed when UV intensity was higher than 9.4 W/m(2), demonstrating the importance of UV-only effects on the ultimate phototoxicity of nanomaterials. Furthermore, both bioavailability and surface attachment of nano-TiO2 onto organisms were affected by the exposure scenario, supported by the exposure scenario-dependent phototoxicity seen in H. azteca and C. dilutus. Overall, the present study demonstrates the importance of species sensitivity and exposure scenarios in future test guidelines of nano-phototoxicity.
National Health and Environmental Effects Research Laboratory, Office of Research and Development, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA.
Shibin
S
Li
Lindsay K
LK
Wallis
Stephen A
SA
Diamond
Hongbo
H
Ma
Dale J
DJ
Hoff
D033304:Amphipoda / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D002683:Chironomidae / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D005618:Fresh Water / Q000032:analysis; D007928:Lethal Dose 50; D053758:Nanoparticles / Q000032:analysis / Q000633:toxicity*; D009835:Oligochaeta / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D014025:Titanium / Q000032:analysis / Q000633:toxicity*; D014466:Ultraviolet Rays
C009495:titanium dioxide; D014025:Titanium
Benthic organisms; Exposure scenario; Nano-TiO2; Phototoxicity; Species sensitivity