Fecal lead (Pb) provides an indication of recent oral exposure to the element, and to a much lesser extent Pb that has been excreted from the body in bile. Absorbed Pb is excreted primarily in urine (76%) and bile (16%). Lead remains the most common clinically problematic toxic metal despite long past termination of its use in gasoline and paint. However, high levels of Pb have been found in soil under older bridges and overpasses due to sand blasting and refurbishing.
Most lead contamination occurs via oral ingestion of contaminated food or water, or by children mouthing or eating lead-containing objects such as imported children’s trinkets and toys. Municipal drinking water has become a significant source of Pb in certain parts of the country.
Lead has been reported to be present in chocolate (the darker the higher), cocoa powders, and some chocolate flavored whey protein concentrates. In addition to some glazed pottery and lead crystal glass (drinking glasses/carafes), Pb may be present in dinnerware. Other sources of lead include: old lead paint (dust/chips), bullets and fishing tackle, batteries, computers, industrial smelting and alloying, ceramics, and artist paints and pigments (including certain tattoo inks).
The extent of oral absorption of Pb depends upon stomach contents (empty stomach increases uptake), and upon essential element status and dietary intake. Deficiency of zinc, calcium or iron may increase lead uptake. Transdermal exposure is slight, except for high absorption of lead acetate that may be present in hair darkening dyes.
Lead (Pb) has pathological, neurotoxic, nephrotoxic and carcinogenic effects that may be manifested with even chronic low-level exposure. Pb may also affect the body’s ability to utilize the essential elements calcium, magnesium, and zinc. Sustained Pb exposures may have adverse effects on memory, cognitive function, nerve conduction, and metabolism of vitamin D. Infants and children are especially vulnerable to Pb-induced developmental disorders, and behavior problems are associated with lower levels of blood Pb
than previously acknowledged; lower of IQ, hearing loss, and poor growth.
The medical standard of care for assessment of lead exposure and toxicity is elevated blood lead. However blood lead may only reveal isolated exposures as the half-life of Pb in circulation is only about 1 month. Hair elemental analysis may provide information regarding Pb exposure over the past 2-4 months. Urine porphyrin analysis may reveal P-induced disruption of heme biosynthesis (physiological impact).
Lead
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