Which chlorination byproduct is the primary concern in drinking water chlorinated with organic matter present, and what is its significance?
- A Hypochlorous acid — antimicrobial agent with no public health concern
- B Chloramines — respiratory sensitizers in occupational settings only
- C Trihalomethanes (THMs, especially chloroform) — carcinogenic byproducts when chlorine reacts with natural organic matter ✓
- D Chlorine dioxide — only relevant for surface water treatment
Correct answer: C. Trihalomethanes (THMs, especially chloroform) — carcinogenic byproducts when chlorine reacts with natural organic matter
Explanation
When free chlorine reacts with natural organic matter (humic and fulvic acids) in water, trihalomethanes (THMs) — primarily chloroform (CHCl₃), bromodichloromethane, dibromochloromethane, and bromoform — are formed. THMs are classified as potential carcinogens (IARC Group 2B for chloroform) and are regulated in drinking water (WHO guideline: 300 µg/L for chloroform). This is the classic trade-off between microbial disinfection benefit and chemical carcinogenicity risk in chlorinated water.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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