Abstract: Abstract:A 46-day continuous semi-static waterborne exposure experiment, including a 28-day uptake phase and an 18-day elimination phase, was conducted to assess the accumulation and elimination of two kinds of crystal forms (anatase and rutile) of nano-TiO₂ in zebrafish (Danio rerio) exposed to nanoparticles suspension of 4.0 and 10.0 mg/L. The profiles of accumulation and elimination of nano-TiO₂ in D. rerio were investigated through measuring the body burden of nanoparticles in the fish tissues. In addition, the abilities of accumulation and elimination of two kinds of crystal forms were comparatively analyzed through the bioaccumulation factors (BAF), the elimination rate coefficient and elimination rate of total contents in the fish body. The results showed the accumulated amount of anatase in D. rerio was significantly larger than those of rutile, and the body burden of nano-TiO₂ in the 10.0 mg/L treatment groups for the two kinds of crystal forms were significantly higher than the 4.0 mg/L treatment groups. The BAF of anatase for the 4.0 and 10.0 mg/L treatment groups were 76.7 and 105.4 L/kg, respectively, which were slightly higher than the values for rutile (41.6 and 36.1 L/kg). Therefore, neither of the two crystal forms was considered as a bioaccumulative substance. In the elimination phase, accumulation of both forms of nano-TiO₂ in the fish body could be depurated efficiently with the higher elimination rate (88.0%-100.0%) after 18 d post-exposure. The declining profiles of nano-TiO₂ body burden were in line with the first-order exponential decay equation, with depuration rate coefficient between 0.26-1.01 d^-1.