alt Hacker NewsThat's largely a myth.
This review [1] cites the absolute highest amount of emitted styrene in the studies they are reviewing to be 113 μg/min. Using [2] for simplicity with styrene's molar mass (104.15 g/mol), we get to a printer creating at most 0.024 ppm of styrene per minute per m3 of unchanged air. For comparison, the "work exposure limit (WEL) for styrene is currently 100 parts per million (ppm) averaged over an 8-hour day" [4].
In other words, as long as you have some air exchange in the room, you'd be orders of magnitude away from the safe work exposure limit on styrene.
It also makes sense, considering that it's a microscopic amount of molten plastic, whereas injection moulding factories work with vats of the stuff.
[1]: https://www.sciencedirect.com/science/article/pii/S135223102...
[2]: https://teesing.com/en/tools/ppm-mg3-converter
There are active studies on chopped CF inhalation/contact hazards, and the SEM images in the above post prove how it occurs.
A lot of plastics contain wide assortments of additives to obtain mechanical properties. Outdoor ventilation is absolutely preferable to filtration or smell reduction filters that does practically nothing about carcinogens.
PLA is comparatively low emission, but a slow cooking PTFE tube in many hot-ends is not something people should be around. ymmv =3