Human-made chemicals with the unexpected ability to interfere with our body's endocrine system have become prominent contaminants in daily life. Because the hormones produced by our endocrine system create complex signaling networks that control our growth, maturation, fertility, immunity, behavior, and sleep, these endocrine disrupting chemicals, or EDCs, can exert powerful biological effects. Declines in human fertility evidenced by falling sperm counts and increases in the incidence of infertility raise concern that daily exposure to EDC contaminants already is impacting human fertility. By design, all species are responsive to their environment. In humans, this responsiveness means that changes in our environment can affect the production of eggs and sperm, the growth and development of the fetus, and adult susceptibility to disease. Thus, in a 21st century world characterized by environmental crises, EDCs represent a planetary health problem with the potential to affect future generations. (#37912)