One morning in 2012, Phyllis Omido was pushed into a police van, taken to the local jail, and beaten. Omido, then 34, had organized a peaceful demonstration against her former employer, a lead-acid-battery recycling plant in the town of Owino Uhuru outside Mombasa, Kenya, when she was arrested along with 16 others.

The protests came three years after Omido, a University of Nairobi graduate, started to associate Owino Uhuru’s high lead levels—and its people’s devastating medical conditions—with Metal Refinery EPZ, where she worked as a community-relations manager. Since then, Omido, who quit her job at the factory in 2009, had been fruitlessly trying to convince government officials, including in the capital city of Nairobi, that the refinery’s smelter, which extracted lead from old car batteries, was releasing toxic fumes and lead-filled dust particles into the air.