Composite: Bernardo De Niz/Quinto Elemento Lab Raquel Villarreal lives in a bright-yellow house in Mexico’s Monterrey metropolitan area with her family and nine cats. Here, the emergency medicine doctor has raised three daughters, one of whom died at the age of 14. Just steps away is an industrial plant that operates 24 hours a day, emitting pollution that neighbors say blankets the neighborhood and which Villarreal says is hard to remove from her car. In 2023, a prominent toxicology researcher at the Universidad Nacional Autónoma de México (UNAM), Martín Soto Jiménez, came to her gate and asked to test the