Each day, people everywhere are exposed to chemicals - in their food, in the water they drink, and in the air they breathe. Some exposures are the result of accidents, disasters, or intentional attempts to cause harm. The environmental toxicology and epidemiology staff of the Health Studies Branch of CDC’s National Center for Environmental Health (NCEH) specializes in studying, investigating and assessing the extent of and risk for human exposure to environmental chemicals and toxins, and determining the risk of adverse health effects from these exposures.