I think that there's no good single answer to your question really, either in terms of responsibility or requirement for testing. It's a process, and it involves a back and forth between the industry, the government, and the public. Obviously, if we test every single thing for every possible negative effect, it will take too long and cost too much. Equally obviously, we should focus on likely culprits based on past experience and chemical knowledge.
Some things will slip through though. They always do. Chemical compounds that are completely safe in one state could be toxic in another. Things that are safe in one concentration may cause harm in another. Things that are fine when separate may be combined in new ways which are dangerous. Most of the time we have an idea of the potential risks of making new things, but sometimes we just don't.
When you look at the history of toxic effects from industrial activities, you occasionally see examples of negligence (and they tend to make a huge impact), but most of the time it's just plain not knowing that something will be harmful. Asbestos is a great example of this. Seemingly harmless material, but breathe it for 30+ years and it'll build up in the pores of the lungs, clogging them and causing severe medical problems. Ooops!
We test for harmful effects, but the honest fact is that the tests we use are based on past cases of known methods of causing harm. Until we have a non-biologically interacting substance that is just the right size to lodge in the lungs, degrading their performance over time (cause they don't biodegrade!), we aren't likely to think to look for it or test for it. That sucks, but we live in an imperfect world.
And that's without getting into specific individual sensitivities. We see people with sensitivities to all sorts of things which for 99.99% of the population are perfectly safe. It's absurd to think that some new thing wont also trigger a random sensitivity in someone as well. But that's nearly impossible to test for it even if you try. A better way to think about it is that someone *will* have a reaction to any and every material you are using, producing, releasing into the air, etc. The question is how common is the reaction and how harmful is it when it happens?
One person getting sick out of a whole community? Could be something unrelated. Could be a reaction to something at the plant. Obviously, if you can show that something at the plant is causing it, then the company is responsible for the harm. As someone else said, lack of intent doesn't remove responsibility for the result. However, proving a connection can be difficult in that case. We normally prove such things by correlating results. This somewhat requires repeating the same or similar response in someone else, or in some other way being able to reproduce whatever the effect is and show it's caused by something from the plant. Tricky, but possible.
As to nano-stuff? I say neato!
King Nobby wrote:
More words please