We will likely be flooded with posts about this:
Not a great, but a decent initial study I think.
But before the media hype impairs your judgment:
The main results of the article:
(removed references, those are in the full article)
“For comparison, our estimate of the total UFP emission rate for a single PLA-based 3D printer (1.9-2.0×1010 #/min) was similar to that reported during cooking with an electric frying pan (1.1-2.7×1010 #/min). The same 3D printer utilizing a higher temperature ABS feedstock had an emission rate estimate (1.8-2.0×1011 #/min) similar to that reported during grilling food on gas or electric stoves at low power (1.2-2.9×1011 #/min), but approximately an order of magnitude lower than gas or electric stoves operating at high power (1.2-3.4×1012 #/min). Regardless, the desktop 3D printers measured herein can all be classified as “high emitters” with UFP emission rates greater than 1010 particles per min”
“One important limitation to this study is that we have no information about the chemical constituents of the UFPs emitted from either type of 3D printer, although condensation of synthetic organic vapors from the thermoplastic feedstocks are likely a large contributor. In addition to large differences in emission rates observed between PLA- and ABS-based 3D printers, there may also be differences in toxicity because of differences in chemical composition. As mentioned, thermaldecomposition products from ABS have been shown to have toxic effects; however, PLA is known for its biocompatibility and PLA nanoparticles are widely used in drug delivery .”
So please try to read the full article yourself and draw your own conclusions
Anyway, I never figured ABS fumes to be very safe, especially in cases of ABS gunk burning up on the nozzle.
PLA is of course a lot “safer” but I doubt it’s healthy when PLA gunk burns up at the nozzle.
And small amounts of plastic can create large amounts of fume/particles.
That said, I always advocate using printers in well ventilated rooms and/or use a filtered/ventilated enclosure for the printer itself.