Squealing/whistling noise that gets higher-pitched the faster I'm moving
If the noise is related to road speed rather than pedaling force or cadence, it's coming from the wheels. 

I doubt that dust is the problem, bearings have dust seals and dust settling downward on the bike isn't going to get into any bearings.

Hold the bike off the ground, spin the wheels and see if you can recreate the sound. Check brake pad clearance. Disc brake pads rubbing on the disc can make a high pitched sound. You can also check the wheel bearings for play by pushing and pulling laterally on the rims.