within the 48 Contiguous United States
Chlorine is a powerful oxidant added to drinking water by suppliers in order to protect the drinking water from disease-causing organisms, or pathogens. Chlorine protects people from water-borne diseases which is why public water systems are required to maintain a detectible disinfectant residual in the distribution system. In accordance with the Safe Drinking Water Act of 1974, the levels of disinfectant are monitored and if the levels rise above the MRDL (maximum residual disinfectant level) the water supplier must take steps to reduce the amount of disinfectant so that it is below that level. (Source)
While a certain level of disinfectant, such as chlorine, is necessary to control microbes in water it can also pose health risks. Chlorine in the water supply reacts with other naturally-occurring elements to form toxins called trihalomethanes (THMs), which have been linked to a wide range of health issues ranging from asthma and eczema to bladder cancer and heart disease. Some studies link moderate to heavy consumption of chlorinated tap water by pregnant women with higher miscarriage and birth defect rates. (Source) Essentially, if you are drinking chlorinated tap water, there is always a potential risk involved.
So how do you get the chlorine out of your drinking water? It starts with filtering your water right at the faucet using a carbon-based filter.
Activated carbon filters effectively remove many chemicals and gases, and in some cases can be effective in protecting against harmful microorganisms. In addition to improving water quality by removing chlorine, activated carbon can also remove disagreeable tastes and odors from tap water. A few carbon filter systems have been certified for the removal of lead, asbestos, VOCs, cysts, and coliform. The ability of an activated carbon filter to remove chlorine by-products depends on the type of carbon and amount used, the design of the filter and the rate of water flow, how long the filter has been in use, the types of impurities the filter has previously removed, and water conditions. There are two types of carbon filter systems, granular activated carbon and solid block carbon.
Unfortunately, carbon filters are not without limitations. Because granular activated carbon filters can provide a base for the growth of bacteria and chemical recontamination is possible, filters must be kept scrupulously clean and be replaced often. Solid block carbon filters avoid these problems but are more expensive.
Carbon filters are capable of removing many toxic contaminants including THMs from chlorine, but will not protect against all water impurities as they have no effect on harmful nitrates or on high sodium or fluoride levels. This is why it’s recommended to test your water prior to purchasing a water filtration system so you know exactly what impurities and contaminants you are dealing with. Chlorine may not be the most pertinent water issue that needs to be addressed.