Most of my leather work is with oil tanned, which is no problem, a little w/ veg tanned, and some chrome tanned hides (ranging from thin 1oz to thicker 6oz leathers).
Have found that some pig skin suede (nearly all thin hides such as pigskin and lambskins, are chrome tanned) caused a weird metallic taste if I stood over the unit for any time to check the progress… and that was many, many hours ago on my unit, and no ill effects to the machine since. (Though this could be in part due to the dye, too).
But nothing like that when etching many thin cowhides or lambskins.
Nothing to report on my self (yet) apart from the weird taste/feeling in the mouth at the time, and not sure what my lungs took in, but likely worse than other things I’ve inhaled in various factories and crafting projects… But if you plan to do a lot of work with it, might be good to have a good respirator for your comfort available to wear while the machine is running and fully exhausted…