People are exposed to lead if they swallow or breathe lead-contaminated substances. Lead poisoning can be caused by a single large dose of lead, although it is usually the result of exposure to small amounts of lead over a long period of time.

Lead is slowly eliminated from the body in urine, bowel movements, and, to a very small extent, sweat. When the body is exposed to more lead than it can get rid of, it stores the extra lead in the blood, organs, bones, and teeth, and lead poisoning results. Lead can damage the kidneys, central nervous system (brain and spinal cord), and reproductive system. And it can cause high blood pressure. Lead is especially harmful to a child's developing brain.

Blood lead levels are measured in micrograms per deciliter (mcg/dL). There are different opinions among scientists and doctors on what is a safe level of lead in the blood. Lead has no known function in the body-its natural level in people before the industrial revolution in the 1800s and early 1900s was near zero.

Health effects of high blood lead levels in children

Children are more easily and significantly affected by high blood lead levels than adults. High levels of lead in the blood are caused by lead poisoning. There are five classes of lead poisoning, according to the United States Centers for Disease Control and Prevention (CDC). These levels range from class 1 (less than 10 mcg/dL) to class 5 (a medical emergency of at least 70 mcg/dL).

Children who were exposed to lead before birth may be underweight and have low intelligence, attention-span problems, and other signs of nervous system damage.

A recent study showed that declines in IQ can be seen in children with blood lead concentrations below 10 mcg/dL, the level of concern defined by the U.S. Centers for Disease Control and Prevention and the World Health Organization.⁷

Health effects of high blood lead levels in adults

High blood lead levels affect adults in several ways.⁹

• Blood lead levels above 14 mcg/dL may affect blood cell development.
• Blood lead levels above 39 mcg/dL can affect the function of:
  • The blood and the body's ability to form hemoglobin.
  • The nervous system, causing symptoms such as fatigue, irritability, memory loss, and slow reaction time.
  • The kidneys, causing chronic kidney disease and kidney failure.
  • The reproductive system, causing decreased sperm counts and increased numbers of abnormal sperm. Very high levels can cause miscarriage or stillbirth.
• High blood lead levels may also cause high blood pressure.

Unfortunately, people may not have noticeable symptoms until blood lead levels are high enough to cause serious damage to body systems.