Cedar grows in wet ground well. One thing that it has to adapt to this environment and fight the bacteria that would rot it out while still young is that it has it's own aromatic oils and some toxic compounds. cedars that grow in jungle areas of the world have more of these than those that grow in colder, drier places. These are the toxins that keep cedar fence posts from rotting and that make a closet smell nice while repelling moths.
If you didn't have a reaction to the dust while actually doing the sanding, you have little to worry about. Most woodworkers who create cedar dust learn eventually that it is good to wear a dust mask.
I have quit using Port Orford cedaar very much because it has irritated the sinuses of my crew members and it landed me in the hospital with a lung irritation that gave me symptoms like a heart attack, great pain with every atempt to breathe in.
Random info but many of the aromatic compounds found in vegetation are created as poison to defend the trees against insects etc. Peat forests in the tropics are famous for not being decomposed by insects and detrivores because the water is so full of the oils etc that almost everything in there dies. I think the cedar is similar to this and in small concentrations is probably not terrible for humans but is worse with more exposure especially with dust. Using a good quality mask is definitely the best