Once in the body, lead is distributed by the bloodstream to red blood cells, soft tissue, and bone. Lead is eliminated very slowly from the body by the kidneys and gastrointestinal tract; very tiny amounts of lead are lost through perspiration.
Lead serves no useful purpose in the body. It is a poison that binds with the enzymes and other chemicals that aid biological reactions throughout the body – particularly in the blood-forming system; the brain and nerves; and the kidney – interfering with the formation and breakdown of many body chemicals. Significant lead exposure may result in lead-induced anemia. Once lead enters the body, it may adversely affect many of the organ systems. Lead is stored in bone for decades, causing long-term internal exposure. Exposure prevention is essential because damage from lead poisoning may be permanent and, in some cases, fatal.
Where lead is stored in the body
· Blood – 5-10%. Half-life ~ 1 month
· Kidney – 5-10%. Half-life ~ 1 month
· Bone – 80-90%. Half-life ~ 25 years
Biological Evaluation
Exposure to lead is measured either by the concentration of lead in the material (air, water, food, dust, soil, or paint) to which people are exposed in the environment or by the concentration of lead in whole blood, usually expressed in micrograms of lead per deciliter of blood (µg/dL).
Although there are some other clinical procedures to test for lead in the body, the blood lead level is the best initial measurement for evaluating lead exposure. It indicates the amount of lead circulating in the bloodstream, often a measure of recent exposure to lead. However, as previously noted, lead absorbed in the bone in the past can be mobilized during pregnancy, wasting illness (such as cancer or AIDS), injury, or osteoporosis. Therefore, blood lead level is not always an indication of recent exposure.
Comentarios