Interesting read and another reason to use PLA in casual environments. Also makes me wonder about other higher-temp materials.
http://phys.org/news/2013-07-3d-printers-shown-emit-potentially.html
If you read the article you should stop breathing as some of the particles emitted are the same as those used in fuels as lubricants.
So just because the study is on printers the dangers are all around us.
This article came up a month or so ago, the thing to note is:
“The emission rates were similar to those measured in previous studies of several other devices and indoor activities, including cooking on a gas or electric stove, burning scented candles, operating laser printers, or even burning a cigarette.”
The way I see it, the human body has evolved quite a good instinct when it comes to taste and smell. If it smells bad, it’s probably a good idea to open a window. This is pretty much a good rule for life for that matter 
“nanosized particles” is a scary name for “smell”.
Hey guys, I’m not posting this to be “alarmist” (I’m sure that the amount of pre-lead-free solder smoke I’ve huffed will do me in before this will) but my main point is that if were outside the lab doing demos at schools and such, it might be something to take into consideration…