Impact of chlorine?

The toxicity of chlorination byproducts has been known for many years (it isn't really even that surprising -- after all, the whole purpose of disinfection is to kill organisms). Google "disinfection byproducts" or "DBPs" to get more than you need, or check Wikipedia under "chlorination." Web pages of organizations such as EPA or AWWA (American Water Works Association) will probably give you more technical info if you are interested. Dissolved chlorine will react with organic compounds to produce most of the DBPs, including trihalomethanes (THMs) such as chloroform. Treatment of sewage will produce the most DBPs since wastewater contains a much higher organic content; the issue is then the effect of these compounds on the receiving water body. The poster who talked about exposure during showers is correct: most people will have maximum exposure during showering with chlorinated water. The higher temperature will drive volatiles like chloroform into the air, where we breathe them in. But swimmers have that extra source of exposure to chlorination DBPs. Certainly disinfection (even with byproducts) is much preferable than the alternative: increased pathogens in drinking water, swimming pools, and rivers/lakes. The key is to find something that is both effective, affordable and reasonably safe. Alternative processes include ozone and uv treatment. I believe ozonation is pretty common in Europe for drinking water treatment. These processes also produce DBPs but they are generally believed to be less harmful than those produced by chlorination. I am fortunate to swim at a facility that uses uv for one pool and ozone for the other. The reason they switched was the air quality produced by chlorination was just terrible -- poor ventilation, I guess -- and the kids were suffering pretty badly, especially those with asthma. Switching to uv/ozone cleared the problem right up. And the decrease is air quality is very apparent when they add large volumes of (chlorinated) city water to the pool.

The toxicity of chlorination byproducts has been known for many years (it isn't really even that surprising -- after all, the whole purpose of disinfection is to kill organisms). Google "disinfection byproducts" or "DBPs" to get more than you need, or check Wikipedia under "chlorination." Web pages of organizations such as EPA or AWWA (American Water Works Association) will probably give you more technical info if you are interested. Dissolved chlorine will react with organic compounds to produce most of the DBPs, including trihalomethanes (THMs) such as chloroform. Treatment of sewage will produce the most DBPs since wastewater contains a much higher organic content; the issue is then the effect of these compounds on the receiving water body. The poster who talked about exposure during showers is correct: most people will have maximum exposure during showering with chlorinated water. The higher temperature will drive volatiles like chloroform into the air, where we breathe them in. But swimmers have that extra source of exposure to chlorination DBPs. Certainly disinfection (even with byproducts) is much preferable than the alternative: increased pathogens in drinking water, swimming pools, and rivers/lakes. The key is to find something that is both effective, affordable and reasonably safe. Alternative processes include ozone and uv treatment. I believe ozonation is pretty common in Europe for drinking water treatment. These processes also produce DBPs but they are generally believed to be less harmful than those produced by chlorination. I am fortunate to swim at a facility that uses uv for one pool and ozone for the other. The reason they switched was the air quality produced by chlorination was just terrible -- poor ventilation, I guess -- and the kids were suffering pretty badly, especially those with asthma. Switching to uv/ozone cleared the problem right up. And the decrease is air quality is very apparent when they add large volumes of (chlorinated) city water to the pool.