The carbon filters are excellent methods of removing many contaminants. The only problem with them is one of "user neglect" where a filter is used far beyond it's intended life. The contaminants, for the most part, are not destroyed -- they are adsorbed onto the surface of the carbon. When overused, you can end up with a high level of chemicals on the carbon, and bacteria find this to be a fine place to live and multiply. They feed on many of the organic chemicals that have accumulated. So, after the filter sits unused for a while (overnight), that first flush of water in the morning flushes a bunch of undesirable things into your waiting glass. The lessons are: 1) Let the water run through the filter for a few seconds before capturing the water, and 2) change the filter element frequently.
I get queasy when I see one of these filters on a water supply in an small office setting, for example. NOBODY is in charge of maintenance, and the filter is likely to remain for years without being serviced.
