Health risk index evaluation of elements determined in wastewater of Xochimilco and Tlahuac channels

Xochimilco and Tláhuac, located in the southeast of Mexico City, are popular tourist areas known for their unique “Chinampería” system—a traditional agricultural method involving raised beds surrounded by canal water, where a variety of crops are grown. A major environmental challenge in these areas is the release of approximately 1200 wastewater and greywater discharges into the lake, which threatens the ecological balance. This study aims to identify and evaluate contamination from potentially toxic elements in the canals of Xochimilco and Tláhuac. Nine samples were collected from the canal waters, sediments, and water lilies, analyzing high concentrations of elements like arsenic, iron, manganese, zinc, nickel, and lead. Sites S1, S2, S5, and S9 were identified as having particularly high contamination levels of arsenic, cadmium, zinc and copper. Health hazard indices revealed that children are especially vulnerable to arsenic, nickel, and iron than adults (HI ≥ 2.66, 102.02, and 1.03, respectively). Oral ingestion proved to be the primary route of exposure for arsenic, iron, manganese and cadmium (HQ ≥ 13.11), while dermal contact presented significant exposure risks (HQ ≥ 12.37). To protect local health and reduce exposure, it is recommended that urgent mitigation measures be implemented to lower these contamination and risk indices.