I think that depends on how you define 'civilisation'. My inclination is that most people would say civilisation has ended if life is drastically different to how they perceive their life/world they live in. Think 'civilisation as we know it' rather than a dictionary definition.
However, I disagree that it's not an existentisl threat, if only on the basis of possible crop failiures on a massive scale (reduced crop yields are a global issue already). Don't underestimate the impact of food shortages on everything else, we in the west have become accustomed to easy access to food.
Don't worry, lead isn't that toxic. It takes a lot more exposure than the occasional handling to get heavy metal poisoning from it. But yes, odd to use lead as a weight (or put a weight in, perhaps it's a heat-sink?) it's fairly expensive. It could be a lead alloy which makes it more malleable, though a small peice of pure lead like that I'd expect to be easily bendable, but not compressable like clay.