Disinfection-By-Products, or DBPs, are contaminants (some of them cancer-causing) that are left behind by the very chemical (chlorine) that utility authorities use to disinfect and make their water potable.
About 15 years ago, scientific testing identified chlorine as a potential health hazard, but it is not chlorine per se that is dangerous.
Scientists discovered that chlorine reacted with organic materials in water, such as decaying leaves, to produce hundreds of chemical by-products, several of which have been proven to be carcinogenic. Other by-products may cause adverse effects on the liver, nervous system and reproductive systems.
Trihalomethanes, or THMs, make up the bulk of DPBs. Studies done in the US have associated trihalomethanes with increased risk of bladder and rectal cancer.
According to a study done by the American Water Works Association, more than 230 million people (approximately 90% of the US population) received disinfected drinking water containing hundreds of DBPs. Given the large number of people who consume chlorinated drinking water, the number of cases of cancer potentially attributable to this exposure is substantial.
Since a large percentage of the DBPs are developed after leaving the water treatment plant, our only viable course of action is to filter our drinking water at the point-of-use.