What are these "nano-particles" from auto and diesel exhaust, and when breathed in is the damage permanent?

Question

I keep reading about "nano-particles" (very, very small particles) thatn when inhaled travel straight up the nose and lodge themselves in the brain. I have several questions about this.

First off, all articles that I can find all specifically say "travel up the nose" with regards to giving the nano-particles a route to the brain, therefore am I right to assume that it is because these particles travel up the olfactory pathways? If that's true, then wouldn't breathing through your mouth effectively negate this from happening? Sure, it's all going into your lungs, but better the lungs than the brain, right?

What exactly do the nano-particles do inside the body, as well? Once inside, do they ever dissipate, or do they simply bioaccumulate, causing irreversible damage and permanently embedding themselves inside of your lungs and brain?

Lastly, what kind of proximity to an exhaust pipe must you have to actually inhale any of these particulates? Are traffic conditions adequate?

Answer 1

The nanoparticles are just called DEP, or Diesel Exhaust Particulates. When inhaled, it can cause asthma and emphysema, and also heart problems. There is no proximity level that you must be in. Studies have shown that if you are in a crowded city, these particulates are all in the air. The studies show that traffic conditions, especially during idling are adequate.