Lead poisoning effects do not usually present until the level of lead in the body reaches critical levels. Lead, a naturally occurring metal, can have serious and sometimes fatal effects on humans. Lead is toxic to the human body. Although lead is dangerous for the entire body, damage done to the nervous system is the most prominent. Lead poisoning effects include decreased bone and muscle growth, poor muscle coordination, kidney damage, development delays, as well as hearing/speech problems. Children are more susceptible to these lead poisoning effects because their bodies are still growing. In cases of extreme lead poisoning a person may also lose consciousness of have seizures.