I just got an email from a "Citizen Advocate" wanting to know why he was hearing so many different stories about nanotechnology. My answer seems worth reproducing here. I wrote:
There are probably two reasons why you're getting conflicting information. One is that every nano center wants to be The Best. So they'll advertise themselves that way. The other reason is that there are a lot of kinds of nanotechnologies. So one place may be best for chips, another for biotech, another for optics, another for materials, and so on.
Each of the many kinds of nanotech brings its own set of problems. For many of the varieties, the problems are basically industrial. Every material has some level of toxicity (even water--I just read that endurance athletes sometimes drink enough water to kill themselves). So any manufacturing process needs attention. Sometimes there's no problem, and sometimes there is a need for caution and/or oversight--and this is just as true for non-nano manufacturing, and for the same reason. For most purposes, nanoparticles are basically new kinds of chemicals. This means they deserve attention but not panic. In many cases, a nano-related research or manufacturing center will be just as safe as any other. It's appropriate for a citizen advocate to ask questions, but 1) know what questions to ask to figure out if the nano is a special risk and 2) if it's not a special risk, don't make it a campaign issue.
Some stories about nanotech talk about advanced nanorobots and nanofactories. This is a very different kind of nanotech from what's being done today. (Note that "nanomanufacturing" is basically today's nanotech. And some near-term nanotech people talk about "nanorobots" but they mean much simpler devices--basically, complicated chemicals or MEMS--extensions of today's technologies.) The advanced stuff is not a concern yet--a building being built today will categorically not be making nanofactories. And in any case, it's not the nanofactories that are dangerous, but how they could be used. A crate of nanofactories spilling on the ground will be harmless, unless someone steals one and plugs it in and builds something dangerous.
I said that the advanced stuff is not being built yet. This may change in a decade or so. CRN's main purpose is to get people thinking and preparing for that. If you're interested, there's lots of material on our site. A good though lengthy introduction to the issues is our Essential Studies, especially part 5. But if you're trying to decide whether to protest a "nano-foundry" being built today, our publications are mostly irrelevant. For that, learn about nanoparticles. I can give you a broad overview, but it's not my field. There's a group, CBEN at Rice University, that's studying health impacts of nanoparticles; they should be able to point you at useful information.