If you've ever worked on a vehicle with drum brakes, you would see the foolishness in your statement. Brake dust goes everywhere, whether it be drums or disc brakes. Older drum brakes were even more hazardous because the brake linings were built with asbestos, at least until the 1990s for US-made brake products. Aftermarket and foreign-made brake pads apparently still have asbestos in them.
I'm not too worried about this. It's an engineering problem and now that is been raised, we can find solutions.
Drum brakes that I've worked on often have a lot of dust in the drum. Which is a good thing because all of that dust is not in the air. But of course they are not anywhere close to being sealed.
