The precautionary principle is an inherently silly concept, which is often mentioned by environmentalists. It holds that you should not do anything that might be dangerous, until proven safe.
The principle is at its most dangerous when strictly applied. No child would ever learn to cross a road if this was applied. No doubt electricity, the large hadron collider, the Boeing 747, A2 milk and that new corkscrew I got the other day would all be banned. Few things can be proven safe on invention. After all, the new thing has only just come about, often using the pinnacle of technology in that area: almost by definition we don't have a higher pinnacle from which to view the first one and decide on its safety.
It is worth thinking about the actual outcome of the precautionary principle. Take us back 100 years and work forward through each new advance in technology. Which would have been banned on discovery? Quite a lot, I'll warrant, including things like the green revolution. The result would be a massive increase in human suffering, overall.
You can also see it in practice. For example, Europe has banned lead in solder, and it has been replaced with a number of dodgy compounds, the long term effects and properties of which are not well understood. The precautionary principle didn't apply in this case, or did it? Neither and both...the precautionary principle is an inherent contradiction since you don't know whether you are safer with what you have or safer to try something new.
This business of 'don't do it until it has been proved safe' will be the death of us all. It needs to be seriously challenged and discredited.