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3-D Printing

Some 3-D-Printed Parts May Leach Toxic Chemicals

Toxicology: Plastic parts printed with stereolithography show toxicity in tests on zebrafish

by Deirdre Lockwood
November 13, 2015

Photos of 3-D-printed parts and zebrafish embryos.
Credit: Environ. Sci. Tech. Lett
Zebrafish embryos exposed to 3-D-printed parts made using stereolithography (STL, center) lacked pigment-containing cells and died within a week, whereas embryos exposed to parts printed with fused deposition modeling (FDM, left) developed similarly to controls. Treating stereolithography-made parts with ultraviolet light (STL with UV, right) reduced the toxic effects. The embryos are approximately 1 mm in diameter.

The three-dimensional printing craze has attracted hobbyists and researchers alike, making it easy to fabricate stuff from footwear to molecular models. As the technology becomes cheaper and more popular, however, researchers are investigating potential hazards of these products to people and the environment. A new study shows that parts made by a common 3-D printing method are toxic to zebrafish, a model organism often used to predict toxicological effects on humans (Environ. Sci. Tech. Lett. 2015, DOI: 10.1021/acs.estlett.5b00249).

Last year, Shirin Mesbah Oskui, a graduate student at the University of California, Riverside, 3-D printed a small part for a research project involving zebrafish. When she exposed zebrafish to the part, the fish didn’t develop normal coloring, and within a week, most of them died.

To investigate, she and colleagues, including her research adviser, William H. Grover, designed experiments to expose zebrafish embryos to half-dollar-sized disks 3-D printed with two common methods: stereolithography and fused deposition modeling.

Zebrafish exposed to disks printed with stereolithography lacked normal coloring, showed abnormal swelling, and died within a week, similarly to Oskui’s initial observations. In contrast, fish exposed to disks printed with fused deposition modeling mostly developed and survived similarly to controls.

Stereolithography-based printers use light to polymerize layers of a liquid resin usually containing acrylate and methacrylate monomers, a class of chemicals known to be toxic. The researchers hypothesize that monomers or short-chain polymers that are not fully polymerized could be leaching from the parts. Fused deposition modeling, on the other hand, builds parts from melted, fully polymerized material that then resolidifies.

In an effort to reduce the toxic effects of stereolithography-printed pieces by completing polymerization, the team exposed the printed parts to ultraviolet light for an hour, and found that this mostly obviated the toxic effects on the zebrafish. The findings are too preliminary to draw conclusions about human toxicity, Grover says, but they indicate that 3-D printing waste should be carefully managed to prevent harm to ecosystems.



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