title: Chronic toxicity of double-walled carbon nanotubes to three marine organisms: influence of different dispersion methods.
abstract: OBJECTIVE
  Double-walled carbon nanotubes (DWNTs) are found in a variety of consumer products, but there are no ecotoxicity data of DWNTs into marine organisms.
  
  
  METHODS
  Chronic toxicity of DWNTs was investigated with the diatom Thalassiosira pseudonana, copepod Tigriopus japonicus and medaka Oryzias melastigma. DWNTs were dispersed using sonication (so-DWNTs) and stirring (st-DWNTs) for comparison.
  
  
  RESULTS
  The median aggregation size (0.89 microm(2)) of so-DWNTs was smaller than that of st-DWNTs (21.8 microm(2)). Exposure to DWNTs led to growth inhibition of T. pseudonana with EC(50)s of 1.86 and 22.7 mg/l for so- and st-DWNTs, respectively. Population growth of T. japonicus was reduced to 0.1 mg/l for so-DWNTs and 10 mg/l for st-DWNTs. Growth inhibition in O. melastigma was observed at 10 mg/l for so-DWNTs but not for st-DWNTs.
  
  
  CONCLUSIONS
  Given that so-DWNTs are consistently significantly more toxic than st-DWNTs, dispersion method and size of aggregations should be considered in DWNT toxicity testing.
authors.affiliation: The Swire Institute of Marine Science, School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong, PR China. kevin.kwok@duke.edu
authors.forename: Kevin W H
authors.initials: KW
authors.lastname: Kwok
authors.forename: Kenneth M Y
authors.initials: KM
authors.lastname: Leung
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Flahaut
authors.forename: Jinping
authors.initials: J
authors.lastname: Cheng
authors.forename: Shuk Han
authors.initials: SH
authors.lastname: Cheng
mesh_terms: D000818:Animals; D008386:Marine Biology; D037742:Nanotubes, Carbon
chemical_list: D037742:Nanotubes, Carbon