Lead poisoning causes changes in the chemistry of the nervous system. These changes in turn affect the nerves and the communication between cells. This can result in detectable differences in the way the brain functions. Thinking, learning, memory, and the ability to focus attention can be adversely affected. The speed at which the muscles respond can be slowed. Hearing can be mildly impaired, as can the ability to listen and to speak. The sense of balance, as well as motor and hand—eye coordination, can be disturbed.
Numerous studies throughout the world have shown that children who have suffered from lead poisoning have lower IQs on standardized tests as a result, relative to children with acceptable levels of lead. 1 But IQ testing does not always predict how well a child will do in school when there are known or suspected changes in the brain (because of lead or any other condition).