Are there toxic concerns with using a heatgun/torch on plastic/acrylic?
Yes, if you overheat it, most thermo-plastics will give off dangerous gases when heated above a certain temperature. For bending, you need somewhere between 100C - 170C (212&deg;F - 338&deg;F). Cast acrylic needs higher temperatures than extruded (due to the higher molecular weight), and thicker sheet need slightly higher temperature than thinner.

But do not go above 170C (338&deg;F) for extruded acrylic or 190C (374&deg;F) for casted. Just start off low and heat it slowly until the material will bend as you need it. It's only the bubbling and scorching caused by excessive heating that gives off the nasty fumes when burnt. 

From my post on Lifehacks &mdash; Working with acrilyc/plexiglass, electric strip heaters are generally recommended (depending on what you are trying to do), but any electric indirect infrared source can be improvised for occasional use. BBQ starters, heat guns, hair dryers, and even light bulbs have been used, but toaster ovens are a bit more problematic. 

Overall, low and slow is the key. You have to have a controllable heating source, so be careful.