ckwu writes: As 3-D printers become cheaper and more popular, researchers are starting to investigate the potential health and environmental impacts of the technology. A new study shows that parts made by a common 3-D printing method, stereolithography, are toxic to zebrafish, a model organism often used to predict toxicological effects on humans. The researchers hypothesize that acrylate and methacrylate monomers in the resin that don't get fully polymerized could be leaching from the parts. On the other hand, 3-D-printed parts made with another technique, fused deposition modeling, didn't appear to be toxic to zebrafish. The findings are too preliminary to draw conclusions about human toxicity, but they suggest that 3-D printing waste should be carefully managed to prevent harm to ecosystems.