Swimming pools nationwide are required to have chlorine levels that are no less than 1.0 ppm (parts per million) in order to control potentially harmful bacteria levels in the water. But water treatment facilities are also adding at least that amount of chlorine, often more, to your household water, especially this time of year for the same reasons. You already know what high amounts chlorine from pool water can do to your hair, scalp and skin. Now you understand why you experience the most damage to those areas during the summer months when you are not only exposed to chlorine on a regular basis in your shower, but also in the pool. Following is a ranking of the cities with the highest levels of chlorine present in the shower water based on Water Quality Reports from the respective cities measuring chlorine levels.