Wear a mask at any rate. ANY dust is not good for you, so proper precautions are made. I'd worry about lead paint as well, but the small amount of exposure to the contaminates by drilling holes shouldn't pose a health risk with a mask. Heck, you're wearing one right now for the deadliest virus on earth, so it should work for dust particles.

 

Either spray it with water, use a wet/dry vac (stick an extra 2.5" hose on the exhaust of the vac and exhaust it outside), or rent a rotary hammer with the dust extraction feature.

I wouldn't worry too much, my Dad has been in the concrete and masonry trade for 58 years so far, and he's probably work a mask a few hours in that time. He also worked 10 years doing refractory work which often had them using asbestos insulation. No lung issues at 76 years old. I'm certainly not trying to downplay the seriousness of silicosis or asbestosis, but you're not going to die from drilling a few small holes...........

 

Appreciate the techniques offered. I think a respiration cartridge 3M mask and spraying water will do the job then. Probably overkill to be honest. Drilled about 18 holes prior with minimal protection in this wall. I’m not concerned even though some dust was on me ( I’m also not downplaying it). Just don’t want to make the same mistakes with the unknown if I don’t have to. Thanks again.