Fifty years’ study of drinking water disinfection by-products: Identification, formation, occurrence, and state-of-the-art analytical methods

: Disinfection is one of the greatest public health achievements, effectively controlling the spread of waterborne diseases. However, the formation of disinfection by-products (DBPs) is an unintended consequence of disinfection, arising from reactions between disinfectants (such as chlorine, ozone, chlorine dioxide, UV, or chloramine) and natural organic matter, anthropogenic contaminants, bromide, and iodide. DBPs are of great concern because they are ubiquitous in drinking water and generally occur at higher concentrations and exhibit greater toxicity than most anthropogenic contaminants. Since the discovery of the first DBP (chloroform) in 1974, approximately 1,000 DBPs have been identified in drinking water through the collective efforts of scientists worldwide over the past 50 years. In this review, we summarize five decades of research on the identification, formation, occurrence, and state-of-the-art analytical methods of DBPs in drinking water. Specifically, we present a comprehensive list of DBPs identified under different disinfection conditions, discuss analytical techniques used for DBP identification and quantification, and summarize the occurrence and formation mechanisms of both regulated and emerging unregulated DBPs. In addition, we outline future research directions for DBP studies. This review aims to serve as a valuable reference particularly for new researchers entering the field of DBP research.