The present study aims at evaluating the risk of Mutagen X (MX) (3-chloro-4-(dichloromethyl)-5-hydroxy-2 (5H)-furanone) and adverse health effects, associated with direct ingestion of chlorinated drinking water in west of Tehran, supplied by chlorinated drinking water from surface and underground water sources. For one year, MX concentrations in tap water samples has been measured for consumers in four different zones in western Tehran. It has been found that average MX concentration in the whole study area is 24.16 ng/L, with the highest concentration being in Zone 1 with a value of 38 ng/L. Also, the role of water sources, seasonal changes, and effective factors such as Total Organic Carbon (TOC) have been evaluated on MX formation. The highest of excess lifetime cancer risk (ELCR), estimated as 0.0037E-05, belongs to Zone 1, which uses surface water to supply drinking water, while the lowest can be seen in Zone 4, being 0.0021E-05. This latter zone utilizes underground water as the water source. In all zones, the highest risk of excessive cancer is related to winter, ranging from 0.0045E-5 in Zone 1 to 0.0023E-5 in Zone 4. The estimated number of cancer cases for Zones 1 to 4 have been 0.012, 0.016, 0.016, and 0.004, respectively, based on their population. The estimated average risk and the number of ELCR, caused by exposure to MX, through direct ingestion of drinking water have been 0.0030E-5 and 0.047, respectively, in the entire studied area for the duration of one year.

The current study determines the concentrations of trihalomethanes (THMs), and the cancer risk associated with them. The tap water sampling was done from the command area of nine water treatment plants (WTPs) of Delhi, India. THMs levels in the water samples from eighteen distribution points were investigated for one year. The cancer risk (CR) related to THMs by different exposure routes i.e., ingestion, dermal absorption, and inhalation, was assessed for males and females. The THM levels varied between 11.41 µg/L to 175.54 µg/L in the distribution system, having a mean level of 77.58 µg/L. The average concentrations of THMs exceeded the maximum permissible limit given by Indian Standards. The concentration of chloroform was maximum, followed by bromodichloromethane, dibromochloromethane, and bromoform. For males and females, the mean value of total CR was 5.09E-05 5.70E-05, respectively. As the THMs levels were high, the total CR value was also more than the negligible level of risk i.e., 1.0 x 10-6 through all exposure routes.