Millions of US residents may be drinking water containing the potentially harmful compoundYiu Yu Hoi/Getty ImagesA common disinfectant in drinking water breaks down into a chemical compound that we know almost nothing about, including whether it has any potential toxic health effects to those who drink it.Chlorine has been used to sanitise drinking water for more than a century. However, some drinking water systems in the US, UK and Australia now useanother closely related chemical disinfectant called chloramine. Thats because chlorine byproducts were linked to bladder and colon cancer, low birth rates and miscarriage, says