Trihalomethanes (THMs) in drinking water are formed when:

• A Ozone reacts with ammonia
• B UV radiation breaks down nitrates
• C Fluoride interacts with calcium carbonate
• D Chlorine reacts with naturally occurring organic matter (humic and fulvic acids) ✓

Explanation

THMs (including chloroform, bromodichloromethane) are disinfection by-products formed when chlorine used for water treatment reacts with naturally occurring organic matter such as humic and fulvic acids derived from decaying plant material. They are classified as probable human carcinogens. WHO guideline for chloroform (the most common THM) in drinking water is 300 μg/L.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.