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Mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is known as a potent factor in inducing DNA damage and increasing cancer risk. MX is a chlorination disinfection byproduct that comes from the reaction of humic acids and chlorine in drinking water. The purpose of this study was to evaluate the effects of significant factors (including pH, reaction time, chlorine and the concentration of organic materials (TOC)) and their interactions on the MX formation rate in chlorinated drinking water using Box-Behnken Design (BBD) and response surface method (RSM). For this purpose, the simulation of water chlorination disinfection process was carried out in a laboratory scale. A quadratic model was chosen to determine the mathematical relations between the response and the effective factors. All linear parameters, as well as second-degree components except chlorine, were statistically significant. Also, the interactions of contact time with TOC, free chlorine residual with TOC, and chlorine with pH were also statistically significant. Statistical results showed that the pH had a great effect on the potential of MX formation, and then the factors of TOC, chlorine and contact time were effective, respectively. The percentage of contribution (PC) of each component in the formation of MX. The highest significant percentage of contribution (48.36%) was allocated to the pH. Under the optimum conditions (contact time of 48.38 min, chlorine concentration of 0.79 mg/L, TOC concentration of 0.53 mg/L, and pH of 7.98), minimum value of MX was equal to 28.6. • Effective factors and their interactions on the Mutagen X formation was examined. • pH had a great effect on the potential of MX formation. • The percentage of contribution of each component in the formation of MX was determined. • Synchronized optimization was conducted to set two dependent variables in the range. [ABSTRACT FROM AUTHOR]

This paper considers exposure to the concentration of fluoride in drinking water resources of Showt city in West Azerbaijan Province in, Iran, and its related potential health risk assessment issues to the resident populations. For this purpose, 88 drinking water samples were analyzed in 2016 by using the spectrophotometric method. Non-carcinogenic health risks due to F exposure through consumption of drinking water were assessed using the US EPA method. In addition, the associated zoning maps of the obtained results were presented using a geographic information system (GIS). The results indicated that fluoride concentration in drinking water ranged from 0.0 to 5.5 mg L−1 of the study area. Based on this research, 36.36% of the samples had a fluoride level higher than the permissible level, 13.63% had less than the permissible limit, and 50% of the samples had a level within the optimum limit of 0.5–1.5 mg L−1. The Hazard Quotient index (HQ) for children, teenager and adults had health hazards (HQ > 1) in 54.55%, 31.82%, and 22.73% of samples, respectively. Groundwater resources having a risk of more than one were located in the villages of Khilajajam, Kolos, and Shorboulagh. So, in these study areas, there are potential risks of dental and skeletal fluorosis. • Fluorosis is a considerable health problem worldwide. • High concentrations fluoride above 3 mg l−1 may cause dental and skeletal fluorosis. • HQ indicated health risk assessment in relation to F- concentration for children and adults were significant. • The fluoride contamination must be reduced in this study area to decrease endemic fluorosis. [ABSTRACT FROM AUTHOR]