Species sensitivity and dependence on exposure conditions impacting the phototoxicity of TiO2nanoparticles to benthic organisms

Toxicityoftitaniumdioxidenanoparticles(nano-TiO2)toaquaticorganismscanbegreatlyincreasedafterexposuretoultraviolet (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, Lumbriculusvariegatus,andChironomusdilutus)wereconductedtoevaluatenano-TiO2phototoxicity.Whenexposedto20mg/Lofnano- TiO2andvariouslightintensities(0-30W/m 2 ),H.aztecawasthemostsensitive,withamedianlethaldoseof40.7(95%confidenceinterval, 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 0W/m 2 to 41W/m 2 . However, a sharp drop of H. azteca survival was observed when UV intensity was higher than 9.4W/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. Environ Toxicol Chem 2014;33:1563-1569. # 2014 SETAC