In 2015 the United Nations called for an end to open defecation by 2030. It’s not impossible to make great strides: Vietnam, for example, has all but eliminated the practice over the past few decades. Achieving the global milestone, number six on the UN’s list of Sustainable Development Goals, would radically improve public health: Diseases caused by poor sanitation and unsafe water kill more children, some 1.4 million per year, than measles, malaria, and AIDS combined. It also would help alleviate poverty and hunger and improve education. Sick kids miss school, and so do menstruating girls whose schools lack a clean and safe toilet.