Chlorine is a nasty but necessary chemical used to disinfect municipal water supplies, and it's also used at home. Although it’s good for killing bacteria, it’s bad for your skin and your health. Over-the-counter chlorine filters for your shower and sink can only do so much before they themselves get overrun with bacteria and buildup. With long term exposure to low levels of chlorine, there is a potential risk of teeth erosion and lung disease.
For more information on chlorine, look at the Chlorine fact sheet