Chlorine & Disinfection Byproducts
Disinfectant / Byproduct · measured in mg/L
Chlorine is added intentionally to municipal water to kill pathogens, but it can react with organic matter to form disinfection byproducts (DBPs) such as trihalomethanes.
Common sources
Municipal water treatment; DBP formation increases with higher organic content in source water and longer contact time in the distribution system.
Health risks
High residual chlorine can cause eye, nose, and stomach irritation. Long-term exposure to elevated disinfection byproducts has been associated in epidemiological studies with a modestly increased risk of bladder cancer and possible reproductive effects.
Sources & further reading
- EPA — Disinfection Byproducts
- Villanueva CM et al. (2004), 'Disinfection byproducts and bladder cancer: a pooled analysis', Epidemiology, 15(3):357-367
How ClearDive rates severity
Readings are bucketed for map color-coding using thresholds referenced from EPA regulatory limits where available. This is a simplified public-awareness scale, not a substitute for certified lab analysis.
How to test for it
DPD colorimetric test strips or a handheld chlorine meter give an immediate field reading of free/total chlorine.