Lead is easy to find in the environment since it is a by-product or component of many industrial processes. Although its use in paint ceased in 1978, it is still used in industrial materials such as some solders, as a reagent in metal smelting, radiation-shielded containers, and car batteries. Fishing weights, brass, and ammunition also contain lead. In 1973, the federal government began phasing out the use of lead in gasoline. By 1996 it was banned as a fuel additive. However, lead from car exhaust can still be found mixed with soil near roads.
There is no known beneficial role for lead in the body. Thus, there is no 'healthy' or desired concentration of lead in the body. But because lead is so ubiquitous in the environment, it is impossible to prevent or remove it entirely from food. The FDA has an interim reference limit (IRL) for lead. This IRL is a measure of exposure to a contaminant from food that the FDA uses to determine if the amount of exposure could lead to adverse health effects. The IRL for lead was determined using the Centers for Disease Control and Prevention (CDC) reference range for blood lead (<3.5 μg/dL whole blood). The IRL has a 10x safety factor, reflecting ten times less than the amount of lead intake from food that would be required to reach the CDC’s blood reference level. The IRLs for lead are 2.2 µg/day for children and 8.8 µg/day for women of childbearing age.
Absorption and Transport:
About 1-10% of dietary lead is absorbed, though children may have higher rates of absorption. The majority of consumed lead is excreted in the stool. About 94% of lead that is absorbed is taken up in bone. Organic forms of lead tend to accumulate in lipid-dense areas like the brain. Absorbed lead is eventually excreted in the urine.
