Does the chlorine in swimming pools promote breast cancer?

Well, it prevents cholera! :-) We have improved our ability to reduce the amount of free radicals and other byproducts of chlorine right now. But again, there's no question that when you chlorinate water, you do create byproducts that have been shown to increase certain types of cancer. But if we did not treat our swimming pools, we would have outbreaks of infectious diseases. So the challenge is to treat our pools with limited residual chlorine byproducts and there are ways to do that now. These are widely available, and people should ask their municipal water suppliers to tell them they are using the best and latest technologies.