If the brass has any lead in it, it's not a good idea to have it come in contact with the juice. Brass is an alloy of copper & zinc, with other metals added depending on intended use, including lead. Lead can be toxic, even in relatively small quantities...you DO NOT want to inhale it. The symptoms of lead poisoning include hair-loss & loosening of teeth, and even madness. That being said- I shot muzzle-loading muskets and melted & cast my own pure lead bullets for years...other than loosing my hair, I didn't seem to suffer too many other maladies (though my wife would say I do suffer from some forms of insanity)
The only brass considered lead-free is Naval Brass (a very high-quality brass used in some high-end attys & drip-tips), and I highly doubt that the brass washers at the hardware store are of that quality.
Just get some stainless steel washers of the same size & use them instead.... you can usually find small/thin stainless washers at most hobby shops - especially those that specialize in Radio Control.
Believe me, brass was my last choice. Nylon was my first and SS my 2nd. It's all I could find. I'll take it out on my next rebuild.