Low lead levels are never a health issue.

High levels of lead in the body cause toxic effects on the nervous system and in the kidneys. They also interfere with the synthesis of heme in the body. Depending on how high the levels of lead are, the absorption of calcium, magnesium and zinc may become impaired. Lead also causes negative effects on memory and thinking processes, and how nerves work in the body. 

Children, babies and pregnant women are most at risk for developing health problems due to lead accumulation. In children, anemia, hearing problems, stunted growth, low IQ, hyperactivity, behavior problems and learning problems are frequently correlated with higher levels of lead in the body. 

Some specific causes of high urine lead levels might be associated with: 

• PICA, the compulsive eating of items such as high-lead paint chips (especially paint used in homes before 1978)
• The consumption of contaminated water, such as from lead pipes that leach the toxic element
• High levels of lead in breast milk, passed on to the infant
• Eating acidic foods on lead-glazed ceramic pottery, especially pottery from Mexico
• The use of contaminated Ayurvedic, Chinese or Indian herbs in any form
• Contaminated toys
• Consumption of chapulines (grasshoppers) from Mexico, as discovered by the California Department of Health Services in 2003.
• Regular ingestion of game meat whereby hunters used lead ammunition
• Hobbies such as hunting, target practice, stained glass creation, casting bronzes, refinishing furniture, jewelry making, electronics, and glass-blowing.
• Living near or working in a lead mine, smelter, or battery-recycling plant or with someone who works in the lead industry 
• Drinking beverages such as wine from leaded crystal glasses