I have had a swim spa for 8 years now. It's enclosed in a room specifically built for the spa. I am a swim instructor, I keep it heated and I use it year round. I have used Bromine in it since day 1. A week ago, a friend sent me an article about bromine and the hazards it has on your thyroid and the cancers that it causes. I had thyroid issues a few years ago, had part of my thyroid removed. My doctor never suggested that could be a problem, he knew what I did for a living, I spend 4-5 hours a day in my pool! I'm curious if anyone else has experienced thyroid problems. Just Google it. I'd really like to switch to another product, I'm using Chlorine now in the pool but I'd prefer something more natural, does anyone have any suggestions.