ERDENET, ORKHON PROVINCE, MONGOLIA — Oyuka dresses for domestic battle. Mask. Gloves. Hair shrouded under a black hood. A disposable white gown reminiscent of a surgeon. It’s 2 p.m. on a Tuesday; her husband is at work and their two young children are at school. She shoves the oven, freezer and washing machine away from the kitchen walls and grabs a lime-green spray can from behind the bathtub, where it’s out of the children’s reach. “Magic Cleaner,” the bottle says in Chinese. A pesticide.

Oyuka — who asked to be referred to only by her nickname, out of fear of being criticized by her neighbors — lives on the eighth floor of a 10-story building in Erdenet, Mongolia’s second-largest city, where towering apartments cram together like subway riders. Lots of people means lots of trash, which means lots and lots of bugs. Cockroaches. Bedbugs. Centipedes. And what Mongolians call black bugs, speck-like insects that Oyuka fears will bite her children and make them sick.

Over the past year, Oyuka started noticing them in corners, under furniture, on windowsills. She increased how often she sprayed Magic Cleaner, from occasionally to every three months — even though the smell makes her stomach lurch. “Because I don’t know any other good poison, I use this poison often,” she says.