Communities surrounding Mexico’s Endhó reservoir are facing severe environmental and public health challenges linked to decades of pollution from Mexico City’s sewage and industrial runoff. Originally engineered to prevent flooding in the capital, the reservoir has long been used as an irrigation source, benefiting local agriculture with nutrient-rich wastewater. However, this strategy has transformed the Endhó into a heavily contaminated site, described by residents as an environmental “dead zone.”
Depletion of oxygen in the water due to microbial activity has eradicated aquatic life, and in 2024, the reservoir experienced an explosive growth of invasive water hyacinth, expanding more than 27-fold within months, according to government figures. The dense aquatic vegetation has become a breeding ground for mosquitoes, forcing local residents to remain indoors at night to avoid swarms. Community members report frequent cancellations of social events and rely on extensive use of insect repellents and smoke from burning cardboard to cope with the plague.
“We are living on edge,” said Pablo Tinajero, a community leader in Santa María Daxthó, citing increased aggression from prolonged confinement indoors. At a nearby primary school, teachers struggle to maintain focus among students plagued by mosquitoes, with some facilities avoided due to the insect presence. Several residents express concern over the normalization of these conditions, warning that acceptance of such environmental hazards risks becoming a harmful standard.
Health concerns extend beyond insect infestations. Residents near the dam, such as Leticia Sánchez González of Santa Ana Ahuehuepan, report a rise in serious illnesses, including cancer. Sánchez González was diagnosed with breast cancer last year after experiencing persistent symptoms. She and others note that many in the area are falling ill, though comprehensive public health data remain scarce.
Available statistics indicate elevated cancer mortality rates in Tula de Allende municipality, where the dam is situated, consistently exceeding national averages since 2016. Neighboring Tepetitlán municipality has recorded kidney failure and urinary tract disease death rates significantly above countrywide levels. However, no definitive epidemiological studies have been made public for the immediate vicinity of the dam, and government health authorities have declined to fund further research, according to anonymous health researchers. This lack of data complicates efforts to establish a direct causal link between pollution exposure and rising illness rates.
Nevertheless, former epidemiological surveillance director Juan Francisco Martínez asserted that the correlation between environmental contamination and health outcomes is “unequivocal,” despite the absence of formal studies. Residents have dug wells to access cleaner drinking water but government investigations over nearly two decades reveal contamination of these sources with arsenic, mercury, lead, nitrates, fecal bacteria, and petrochemical byproducts. A 2024 official report confirmed the presence of chemical markers found both in the reservoir and local water supplies, indicating leaching of pollutants into the groundwater. Officials from the federal water authority, however, have dismissed some contamination findings as flawed and maintain that water quality remains adequate.
In response to mounting concerns, former President Andrés Manuel López Obrador issued a 2024 decree mandating environmental remediation at the dam, including removal of invasive weeds and mosquito control measures. Efforts so far have included fumigation across 27 communities and extraction of large volumes of water hyacinth, described by authorities as a landmark environmental justice initiative. Critics argue, though, that the plan is hampered by insufficient funding, opposition from farmers reliant on nutrient-rich runoff, and exclusion of public health measures.
Activists and residents stress that addressing environmental degradation alone is insufficient. “Once the environment is restored, our health will improve, they tell us,” said one local organizer. “It’s an insult to our pain. Cancer doesn’t wait. Illnesses don’t wait.”