Are grey streaks in nasal discharge dust particles? at times when i blow my nose i notice grey streaks in the mucus.

Grey mucous: In order to respond to this would need to have a specimen and examine it both macro and microscopically. See an ENT doctor. Good luck, and best wishes.

Alien Grey Snot: Good question. Unless you huff paint or snort ground mushroom caps it is probably just dust or something like that. Do you live or work in a dusty environment? Allergies? Pets (Greyhound..haha...)?Smoker?Very rarely if you have an infection it could be grey but I bet it's more dust mixed-in with the infection, and you'd know if you had a serious infection (you know, stuffy, runny, congested, etc