I heard the other day that using brass in your brewery set-up is a bad idea?! Well I have brass ball valves from the hardware store on all my kettles. I know that typical brass has lead in it but is this type of brass the same? Is it dangerous? If so, how?
This is one of those things that you're going to have to decide for yourself because there is no simple consensus.
Environmental lead is bad. There's no question about that. Increasingly, there's research to suggest that even low levels of lead are harmful (NIH Study). It's not just full-blown poisoning that you want to watch out for, but more subtle effects like hypertension and even gout.
Personally, I don't feel comfortable with any amount of lead, and realistically it's not hard or expensive to replace the leaded-brass with stainless in this situation. Is one ball valve going to be the thing that kills you? Probably not, but brewing involves swings in both temperature and pH, both of which serve to degrade alloys.
But, ultimately, it's a judgment call that everyone makes differently.
Brass is fine as long as you clean it properly. John Palmer details what that means in one of the appendices of How to Brew, which is available online here http://www.howtobrew.com/appendices/appendixB.html
The especially important part:
The brass will turn a buttery yellow color as it is cleaned. If the solution starts to turn green and the brass darkens, then the parts have been soaking too long and the copper in the brass is beginning to dissolve, exposing more lead. The solution has become contaminated and the part should be re-cleaned in a fresh solution.