Was reading some interesting studies on the halogens. If you brew with unfiltered or filtered tap water this could be of relevance to you (esp if your municipal water is treated with chlorine and flouride). Also pretty relavant to the ladies with breast issues and concerning prevention.
To limit the toxic effects of excess floruide, bromine, and chlorine(?) in the body sufficient iodine intake (along with sufficient salt is important to expel them via urine. Getting them out of your body faster so they do less damage.
This study was an enlightening read for me.
http://www.jpands.org/vol11no4/millerd.pdf
Happy drinking.