Lead

Lead (Pb) is a non-essential element. Toxic effects resulting from its extensive use in silver smelting, paint production, jewellery making, ceramic glazes, building construction and in drinking vessels and water supply systems have been known for centuries. The addition of alkyl lead to petrol increased its distribution, although this has now been discontinued in many developed countries. Through the introduction of stringent safety precautions in industry and a reduction in the amount of lead in paint, the number of cases of severe inorganic lead poisoning has been reduced to the point where it is now rare. Increasing anxiety has been expressed in recent years over the possible effects of prolonged sub-clinical lead exposure on neurobehavioural development. The introduction of unleaded petrol and replacement of lead water pipes with copper has further reduced lead exposure. Pica, the repetitive ingestion of non-food substances by young children, may present a hazard in older houses with lead-based paint. The traditional remedies and cosmetics of a number of ethnic groups may contain substantial amounts of lead. Blood lead assay is the measurement of choice for the assessment of exposure to inorganic lead as 95% of blood lead is bound to erythrocytes. For assessment of exposure to organic lead derivatives however, urinary lead estimation is preferred. For occupational health monitoring lead results are expressed in gµ/dL and guidance on the ‘Control of Lead at Work’ regulations can be obtained from the laboratory.