Since dust has no constant assay, we cannot describe its affect on your computer. Obviously metallic dusts pose more of a threat. Corrossive vapors from a pickling process will destroy a pc in hours! The biggest impact from common household dust is clogging up finely spaced radiator fins. This can appreciably reduce the airflow through the radiator causing the deltas to increase. Fine dusts that are abrasive will attack semi open peripherals with moving parts like floppies, zip disks, and compact disc drives. Fine abrasives are VERY destructive to tape devices as well. If your computer is around these kind of contaminants, you should consider relocation! Abrasive dusts are bad for YOU as well.