Any time you solder, you should *always* be in a well ventilated area. Fans and open windows work but being outside is probably best. I did a quick search on the interwebs for you (it's been a while since I've done any soldering and I can't currently locate my supplies to check
) but I'm almost positive that this is what I use. It's technically for electronics but it's good enough for me. I'm not sure about the diameter though... You should probably check out your local electronics store.
It's 96% tin & 4% silver. I'm pretty sure they'd be required to say if there were any cadmium in it (however, I've never heard of that being in silver solder, ugh. How gross). There's one of those California cancer warnings and though I'm not 100%, I'm fairly confident that that's just to account for the fumes from the melting of resins which make its initial wire form more pliable. In other words, I think it's a catch-all, just-in-case kinda thing.
As for general toxicity, you should mainly be concerned during the actual soldering. That is unless you plan to eat your work. Or eat with/on your work. If you're still worried, you might consider sealing your piece with a coat of food grade resin.
If anyone knows better about this particular solder, please pipe up. The last thing I'd want to do is give incorrect and potentially dangerous advice/information since it's not only concerning me now, but others.
Like I said, it's what I use so I hope I helped..