Endocrine disruptors are chemicals that, at certain doses (high or low), may act on the endocrine or hormone system. They are often similar in structure to natural hormones, so they may mimic or block the actions of the body's hormones. These disruptions may contribute to adverse outcomes like cancer, birth defects, obesity, thyroid diseases, fertility, and other developmental disorders. Endocrine disruptors are found widely in contaminated water, air, food, and household products, like plastics. A wide variety of chemicals may have endocrine disrupting effects; some of these chemicals persist or remain in the body for years, whereas others may be non-persistent and cleared relatively quickly.