Trihalomethanes in Indian Drinking Water Treatment Systems: A Multifaceted Assessment of Health and Water Footprint

Disinfection byproducts (DBPs) are formed when chlorine reacts with organic matter in water. Among many, trihalomethanes (THMs) are prevalent DBPs, known as human carcinogens. This study assessed THMs in water from five drinking water treatment plants in Guwahati, India. THM concentrations ranged from 235.92 to 260.42 ppb, significantly exceeding the US Environmental Protection Agency’s recommended limit of 80 ppb. Trichloromethane (TCM) was the most prevalent THM contaminant, followed by bromodichloromethane (BDCM) and dibromochloromethane (DBCM). Lifetime cancer risk and the noncancer hazard index were assessed for chronic consumption of THMs via ingestion, skin absorption, and inhalation. People faced greater health risks via ingestion. According to the average lifetime cancer risk analysis, children are more at risk than adults. Sensitivity analysis revealed that the primary factors affecting cancer risk were the presence of TCM in water, body weight, and the ingestion rate of THMs. A 53.5 MLD treatment plant has a maximum gray water footprint of 27.45 MLD (51.31% of total capacity) to meet the BIS standard of 460 ppb, but diluting the treated water to 80 ppb THMs requires 157.83 MLD of fresh water, almost 3 times the treatment plant’s capacity.