Exposure assessment of nitrate and phenol derivatives in Tehran's water distribution system 

The presence of organic and inorganic contaminants in drinking water is a global concern. Nitrate and phenol derivatives are examples of pollutants that could be of anthropogenic origin. They are associated with numerous health risks, underscoring the importance of monitoring their occurrence in drinking water. This study aimed to measure nitrate and phenol derivatives, including 2,4-dichlorophenol (2,4-DCP), pentachlorophenol (PCP), 2,4,5-trichlorophenol (2,4,5-TCP), 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), and phenol, in Tehran's water distribution system (WDS). Twenty-two districts of the city were compared based on the Hazard Quotient (HQ) and the Excess Lifetime Cancer Risk (ELCR) estimated for the detected pollutants. A positive correlation was observed between the pollutants' concentration in Tehran's WDS and precipitation. The mean of nitrate and PCP in Tehran's WDS were 35.58 ± 8.71 mg L⁻¹ and 76.14 ± 16.93 ng L⁻¹ lower than the guideline values of 50 mg L⁻¹ and 1,000 ng L⁻¹, respectively. Nevertheless, some districts exhibited nitrate concentration exceeding the permissible limit by a factor of 1.2–2.3. Consequently, the nitrate intake in some districts constituted approximately 50% of the reference dose. While PCP as a phenol derivative with more health concerns was identified in Tehran's WDS, the likelihood of its health effects was determined to be negligible.