All solder fumes can cause occupational asthma
and other health problems (leaded and lead-free)
if used for long periods at a time. The best
solder wire contains something called Rosin that
helps the solder flow when hot. This causes
asthma if you are over exposed and is irreversible. [0]
A few years ago I had the pleasure of meeting the creator of the Choo Choo Barn in Strasberg, Pennsylvania [1]. He'd ended up with severe lung cancer do to all the soldering fume inhalation over the years.
[0] "Are solder fumes bad for me?" - https://electronics.stackexchange.com/questions/1904/are-sol...
The rosin in solder is nothing more pine resin; it's identical to the resin used by violinists. In fact, it is easy and cheap to make your own "liquid rosin" for soldering (usually SMT drag soldering); you can make enough for a lifetime of use for what you would pay for a single MG Chemicals pen.
Good to breath in? Nope. But hardly something that'll kill you, except in cases of chronic exposure (that is, if you breath it constantly every day for weeks on end - most hobbyists won't ever end up doing such).
Now - acid core solder (not something you use on electronics, mind you - but generally for metalwork) is not something you want to breath in period. Whereas rosin core, while smelly, might just make you cough a bit (unless you are more sensitive than others), acid core will make you choke almost - and it burns your throat. Not only that, it can make your eyes sting (so - regardless of what solder you are using, eye protection goggles are definitely something to wear). Adequate ventilation for acid-core solder is a must; without such, you might actually find it worthwhile to wear a mask of some sort to prevent excess fume exposure.
Hey, side question if anyone knows; would P100 filters on a dusk mask help?
Importantly, fumes do not contain lead. Lead oxide fumes only start occuring above 450°C, well above normal soldering temperatures (320-370°C).
The P100 filter catches airborne particles larger than 0.3 microns. Solder fumes are partly particles down to 0.1 microns, but also gases produced from vaporization of rosin; e.g. toluene, formaldehyde, styrene. Those are molecules a lot smaller than 0.3 microns. So the answer is no, just a P100 filter does not solve everything.
If you need to use a mask, I would suggest a 3M 7500 half-mask with the organic vapor/acid gas/P100 combo filter. I use one for glue work etc. and it's got a very tight seal and is pretty comfy (relatively speaking). Will cost you about $40-$50. Does require a relatively clean shave and proper fitting (sniff test) to be effective.
Or you could get a benchtop soldering fume extractor with an activated carbon and HEPA filter, which is a lot more comfortable. Also more expensive though.
Cheapest solution is doing like a friend of mine, using his shop vacuum with HEPA filter.
Actually, the most bare-bones cheapest solution would be to solder outside with a slight breeze. Only works in certain climates and times of year, tho...
You learn something new every day, thanks!
(You sure can at home, so let me clarify: can't to that at school, or at kids labs, like the place I was working in)