Chlorine is a necessary evil when it comes to having mains water piped into our homes but you may be surprised that the Chlorine in mains water (we will call it that) is different to what we would find in a swimming pool.
The substance injected into our mains water is a gas not a liquid, it is commonly referred to as chlorine by all even the water authorities but it is in fact hypochlorous acid (true chlorine), the chlorine in swimming pools is usually sodium or calcium hypochlorite.
When hypochlorite (swimming pool chlorine) solutions are placed into water the atoms hydrolyse from the molecules releasing hypochlorous acid (true chlorine), also released are compounds like trichloro-s-traizinetrione and sodium dichloro-s-triazinetrione and that is why they smell similar but most of the smell in both mains water and pools is a by-product which are commonly refered to as total trihalomethanes and trichloroethylenes which are created when the chlorine binds with organic compounds in the water, all trihalomethanes are carcinogenic and have been linked to bladder and rectal cancers, there are other by-products like styrene, toluene and xylene which damage the white and red blood cells.
Chlorine kills off harmful bacteria in mains water supplies but also when consumed will kill good bacteria in the digestive system, some people take acidophilus as a dietary supplement to try and build up the numbers of good bacteria, if chlorinated water is consumed the good can be undone.
The added chlorine levels in mains water supplies in Australia are in general between 0.5 and 1 part per million, in the U.S.A. where most of the water filters are developed are close to 2 parts per million so water filter systems in America are far more common than here in Australia due to their higher chlorination levels, chlorine and it's by-products is easily removed with carbon filtration.
Chlorine is necessary to provide safe drinking water (as far as bacteria and cysts are concerned) supplied to our homes but when it arrives at our homes we don't need it any more and this unpleasant product can be easily removed with filtration.
Chlorine is added to mains water supplies at around 1 part per million, a 30 ppm dose will cause vomiting, a 60 ppm dose will result in instant lung damage and at 1000 ppm a few breaths will be fatal. When inhaled at doses above 30 ppm the chlorine reacts with the moisture (water) in the cells of the lungs and creates hydrochloric acid and hypochlorous acid resulting in tissue burning.
It is interesting that the authorities state that low doses of very dangerous chemicals can be harmless to the human body, they state that chemicals like pesticides and herbicides at XXX concentration are harmless and heavy metals like mercury are Ok as long as they don't exceed XXX level but it is like a bee sting, unless you are allergic, one is harmless but have too many and it will be fatal, can our bodies continue to be bombarded with all these chemicals and compounds.
Chlorine was used as a chemical weapon in the first world war by Germany at the Battle of Ypres in April, 1915 and was called Bertholite, later came the Mustard Gas which wasn't chlorine, other countries also later used chemical weapons as well. The chlorine reacted with moisture (mucosa) in the lungs to create hydrochloric acid, resulting in many deaths, chlorine gas is heavier than air so it would travel on the wind and descend into the trenches where the soldiers were, the soldiers were issued with gas masks and the active ingredient in them was activated carbon which is what is the main filtering media in water filters.