Lead

General information

Lead is a heavy soft bluish-gray metal (symbol Pb; atomic no. 82) that is widespread as different salts in minerals such as chromite (oxide), crocoisite (chromate), Jamesonite and zinkenite (sulfides), mimetite (arsenate and chloride), pyromorphite (phosphate and chloride), and vanadinite (vanadate and chloride).

Lead has no place in internal medical treatment, although lead acetate has retained a very small place as an astringent. Its toxic effects are known primarily from environmental and occupational exposure and occasionally from the use of alternative remedies or cosmetics. For example, lead sulfide in eye-drops originating in India has caused lead poisoning, and lead has been found in some supposed aphrodisiacs from India. Children with circulating lead concentrations in excess of 600 ng/ml have impaired intellectual performance and electrocardiographic changes, and at any age excessive intake can cause encephalopathy, neuropathies, anemia, anorexia, colic, and renal damage. Lead poisoning from occupational and environmental sources continues to be reported. The biological chemistry of lead has been reviewed [ ].

No significant effects have been attributed to lead as a contaminant in infant formulas or total parenteral nutrition. In an investigation of the protective effect of calcium supplements against lead absorption, 103 infants aged 3.5–6.0 months were randomly assigned to receive an infant formula (iron-fortified, containing 465 micrograms/ml of calcium and 317 micrograms/ml of phosphate) or the same formula with added calcium glycerophosphate (1800 micrograms/ml of calcium and 1390 micrograms/ml of phosphate) for 9 months [ ]. There was no significant difference between the groups in the mean ratio of urinary calcium to creatinine, serum calcium, or serum phosphorus, nor any change in iron status. At month 4, the median increase was 0.07 μmol/l in the control group and 0.04 μmol/l in the supplemented group. This significant effect was attenuated during the latter half of the trial, with overall increases in blood lead of 0.12 μmol/l in controls and 0.10 μmol/l in the supplemented group. Supplementation did not have a measurable effect on urinary calcium excretion, calcium homeostasis, or iron status. The significant effect on blood lead concentration was expected, although it was not sustained during the whole study, and so no prevention could be concluded.

Lead has also been reported to contaminate opium [ ], and in opium users who present with acute abdominal complaints, lead poisoning should be ruled out.