A review of the current environmental status and human health implications of one of the most polluted rivers of Mexico: The Atoyac River, Puebla

For more than 4 decades, the Atoyac River in central Mexico has been subjected to anthropogenic stresses driven by the urban and industrial wastewater discharges, as well as leachates coming from intensive peri-urban agricultural practices. This review provides an overview of the levels of organic, inorganic and microbiological contaminants found during the past 10 years in waters and bed sediments of the Atoyac system, and the implication of this pollution over the human health. Overall, the Atoyac waters present high loads of nutrients, BOD₅, COD, TDS and trace elements (Al, Fe, Zn, Pb, Cr, Cu). The bacteriological pollution is extremely high; with total coliform values of up to 10¹² MPN/100 mL. Anthropogenic organics such as PAHs, PCBs and organophosphate and organochlorine pesticides have been also found in river waters. Although pharmaceuticals have not been surveyed in a broad range, considerable concentrations of Triclosan, Naproxen and Diclofenac have been detected in river waters. Regarding sediments, anoxic conditions promote the precipitation/enrichment of sulfides and associated trace elements (As, Fe, Mo, Pb, Zn, Cu, Cr). Microplastics in sediments included films (25.9%), fragments (22.2%), fibers (14.8%) and pellets (11.1%). Fibers from the textile industry were found to accumulate in the aquatic biota of the Valsequillo reservoir. Quality indexes demonstrated that waters and sediments in the Puebla City are the most contaminated. The water of this zone reached the classification of strongly contaminated, whereas the sediments showed the most accumulation/enrichment of major and trace elements of the riverine zones. The main pathologies found in humans were gastrointestinal diseases, whereas children living in vulnerable zones showed elevated levels of cancer biomarkers. Studies have indicated a high risk of suffering cancerous diseases in children that consume contaminated groundwater and high risks for developing non-cancerous diseases in adults working with river-irrigated soils and children consuming milk with high content of river-derived Arsenic.