Dust caused by hinges is common with residential duty hinges and is caused by the pieces of metal rubbing against each other. From what I hear a little lubrication with lithium grease can help though I don't think it will eliminate the problem. Wd40 doesn't really work either though it will help the door open smoothly. Probably the best solution is to get ball bearing hinges, but it does cost bit. Some hinges tend to leave more dust than others usually the cheap brass hinges are the worst. If you need replacements try door hinges here.  width=