Chlorine was first discovered in the sixteenth century, and today is one of the most produced chemicals in the US, finding its way into a multitude of products. Chlorine is so deeply inter-twined into industry that finding alternatives would indeed change our daily lives. Chlorine is produced the electrolysis of salt water. Cl2 is isolated in its gaseous form, and used to create other chlorine compounds used for sanitizing, bleaching and production of plastics and related products. When chlorine is added to water, another dissociation occurs.
Hypochlorous acid is the active, killing form of chlorine.
This is what does the real sanitizing work. The chlorine molecule or ion kills microorganisms by slashing through the cell walls and destroying the inner enzymes, structures and processes. When this occurs, the cell has been deactivated, or oxidized. No doubt about it, chlorine certainly is a hazardous product, with some forms of it being more dangerous for the handler and the environment than other forms. Chlorine in a solution of water at levels found in swimming pools pose no danger for swimmers.