So I'm writing this term paper about nanoparticles. These are teeny tiny particles of around a billionth of a metre long. In some ways they're really cool becuase they have wierd and wonderful properties that make them useful in industries like aerospace, computer, electrical, and of course, cosmetics. (If you use sunscreen that goes on clear, you have put nanoparticles onto your skin.)
If they get into the air, they are not-so-cool because they seem to be able to create more inflammation in your lungs than bigger air pollutants. In general they're kind of scary because they can translocate out of the lungs and into the bloodstream, thereby reaching every organ in the body. They have also been found capable of crossing the blood-brain barrier and the blood-testis barrier in mice. And to top it off, they seem to be able to get into cells as well.
So theoretically, they could do a lot of damage. Or be really useful in developing drugs that targeting diseases like Alzheimers.
Most nanotech industries aren't producing huge amounts of these things yet - they're still in the R&D/preproduction phase of things. But the future is coming... and these things are also not regulated yet. At all. Anywhere.
It all feels a bit sci-fi...