Invited Commentary Invited Commentary: Disinfection By-Products and Pregnancy Loss—Lessons

Chlorine was first used to purify water in the United States almost 100 years ago (1). Since that time, the tech-nique has been improved upon and its use expanded so that most water systems today are disinfected (1). In 1995, ap-proximately 64 percent of community water systems (sys-tems that provide water to the same people year-round) specifically added chlorine as a disinfectant, and the remain-ing systems commonly added chloramine, according to an Environmental Protection Agency survey (1). Disinfection protects against waterborne pathogens, but chlorine reacts with organic matter in the water to form both halogenated and nonhalogenated disinfection by-products (DBPs), in-cluding trihalomethanes (THMs) (2). The Environmental Protection Agency set standards for total THM levels in community water systems after the Safe Drinking Wate