The potential health impact on young children in Flint, Michigan is serious. Two years ago, lead in the city’s water supply reached toxic levels and the drinking water was declared unsafe. At high levels, exposure to lead can affect almost every system in the human body. For young children, especially, it can contribute to learning and behavior problems, slow growth and physical development, and lead to hearing and speech problems. Lead exposure also has been associated with Attention-deficit/hyperactivity disorder (ADHD). A Duke University study found that exposure to lead can have a negative impact on children’s lives for decades.