In the past century, the threats to children's health have shifted radically. Life-threatening infectious diseases--smallpox, polio, and cholera--have been largely conquered. But children are growing up in a world in which environmental toxins are ubiquitous. Measurable levels of hundreds of man-made chemicals are routinely found in the bodies of all Americans, including newborns. Infants are exposed to polychlorinated biphenyls, lead, and mercury in the womb and through breast milk. Baby bottles and toys have been found to contain phthalates, bisphenol A, and lead, all toxins that have been linked to reproductive and developmental disorders. As harmful elements detected in everyday household items increase, rates of chronic disease have also risen sharply--and these conditions are now the leading causes of childhood illness and death. Responsibility for developing strong environmental policies does not rest with government alone. Other organizations--including schools--also should have carefully developed policies to ensure that they provide clean and safe environments. Teachers and administrators can serve as advocates for children by identifying and addressing environmental hazards in schools. This article highlights common environmental problems in the school setting--lead, pesticides, mercury, arsenic, outdoor and indoor air pollution, mold, asbestos, radon, bisphenol A/phthalates, and polychlorinated biphenyls--and identifies steps teachers and administrators can take to prevent or minimize exposure to these problems. (Contains 31 endnotes.)