In the tradition of Silent Spring and The Sixth Extinction, an urgent, meticulously researched, and groundbreaking book about the ways in which chemicals in the modern environment are changing human sexuality and endangering fertility on a vast scale, from renowned scientist Shanna Swan. In 2017, Swan and her team of researchers completed a major study. They found that over the previous four decades, sperm levels among men in Western countries had plummeted by more than 50 percent. Sexual development is changing broadly, for both men and women, and the modern world is on pace to become an infertile one. Chemical exposures are affecting our fertility, sexual development, and functionality-even, perhaps, gender identity-and overall health. Not just an illuminating overview of a grave threat but a helpful guide to protecting ourselves against it, Count Down is an urgent wake-up call, an enjoyable read, and a vital tool for understanding our future. Book jacket.