Well, it's an interesting question.
And you're right; we could use a metallurgist to really sink our teeth into this.
But let me take a stab or two at it.
If there was very much lead in this alloy, wouldn't that make for a very soft, crummy steel? (but this stuff doesnt' seem to be all that hard and high-quality, either)
And would there be so much of it "flaking" or wearing off to be a worry?
I really don't know the answers to those questions. But I'll bet someone will come along who does.