Not only is it an irritant to throat and nose, but the dust is incredibly powder-like and invasive. However once the work has been finished, either with paint it seems that MDF dust ceases to pose a risk.

Does painting MDF make it safe?

Yes you should prime with MDF primer before painting, this is because ordinary primer will react with the glue chemicals used in the making of MDF and does give off gas. Once primed, 2 coats, MDF is perfectly safe, you can eat off of it for life, in fact it safe in its bare state, with ventilation.

Does painted MDF off gas?

Your freshly painted 'new home smell' is the mark of off-gassing chemicals; and now homes are less drafty these chemical nasties hang around even longer. MDF deserves a special mention as the devil's own work, containing urea formaldehyde that continually 'off-gasses', together with highly hazardous fibrous dust.