Iodination is much like chlorination in its effect and method of application. Like chlorine, it has the additional benefit of remaining in water for a considerable length of time. This enables it to destroy cysts such as giardia, a common organism which cases diarrhea, on which chlorine has no effect. Iodination is not used in public water supplies in Colorado. It is used less commonly than chlorine. The effect of the residue on the taste and odor of drinking water is an issue for some consumers.