Learn how biologist Rachel Carson was driven to write Silent Spring, a book that questioned the safety of pesticide use in the United States, in this video segment adapted from AMERICAN EXPERIENCE: Rachel Carson's Silent Spring. The most famous pesticide at the time was DDT, a chemical that had saved millions of lives in World War II from insect-borne disease and was thought to be safe. But Carson found evidence that DDT was poisoning birds and represented a real threat to humans as well. She thought the chemical industry was pushing their overuse for its economic gain, at the expense of health and the environment.