This seems like the go-to FUD or, more likely, the possible consequence people glom onto when it's reported/suggested.

Like you said though, jury is still out. I obviously don't expect it to turn out to be good for humanity but I just wonder if there's any documented side effect, to humanity or the ecosystem/biosphere.

I have to imagine you can also find an amount of glass of similar similar size all around. The only saving grace for glass is that it doesn't float.