The Lerma River originates in the State of Mexico, flows into Lake Chapala, and then emerges as the Río Santiago.
Both rivers are among the most polluted in the world, contaminated by human and industrial waste to such an extent that treatment plants are overwhelmed, exposing local communities to toxic conditions and a nauseating stench.
Numerous efforts have been launched to clean up the Lerma-Santiago System, but few have had much success, prompting those living alongside the rivers to seek their own solutions.
Two grassroots approaches have stood the test of time. Both involve filtering the polluted river water—one using eggshells (cascarones) and the other using tezontle (volcanic clinkers, also known as scoria).
The eggshell movement began around 2019 when Lerma resident Elvia Evangelina Árias discovered that her neighbor, water researcher Verónica Martínez Miranda, had clean water coming from her tap. In contrast, Árias’ water was yellow and foul-smelling.
Both women got their water from wells partially contaminated by the Lerma River, but Martínez had protected her well with a homemade filter made from eggshells, lime and magnesium oxide.
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