(a) Dose-response relationships for mortality at 120 hours post fertilization (hpf) induced by intact and weathered QDs. Data for CdCl2 shown as a reference. (b) Morphological malformations at 120 hpf resulting from exposure to 20 μM Cd equivalents of as-synthesized QDs, weathered QDs or CdCl2. Morphological endpoints of toxicity included altered axial curvatures (aac), yolk sac malformations (ysm), pericardial edema (pe), tail malformations (tm), ocular edema (oe), opaque tissues and craniofacial malformations (cfm). In (a), calculated LC50 values (95% confidence intervals, CI95%) for PEG5000-QD, weathered PEG5000-QDs, and CdCl2 were 42 (CI95%: 24-75), 14 (CI95%: 9-21), and 409 (CI95%: 270-563) μM Cd equivalents, respectively.