The lead blood test measures the amount of lead in the blood. Lead is a naturally occurring metal that has no known useful role in the body. It can enter the body through contaminated air, water, food, dust, or certain products such as old paint, and it can build up over time. This test reflects recent or ongoing exposure to lead. This test is used to check for exposure to lead and to help monitor people who may be at risk, such as children living in older homes or workers exposed to lead on the job. It is also used to track lead levels over time in people who have had elevated results or who are undergoing treatment for lead exposure.