Manganese

Scottish Trace Element and Micronutrient Reference Laboratory

Scotland's specialised laboratory for trace elements and vitamins in health and disease

Lead (Pb)

Trace Elements

Vitamins

Specialised services

Information

Lead mining in Southern Scotland. The beam engine at the former lead mine in Wanlockhead, c. 1900. This now forms part of the Lead Mining Museum. Photograph by courtesy of the Wanlockhead Museum Trust.

Inorganic lead compounds have been known to be a toxic hazard for many hundreds of years. Control of lead exposure at work is covered by regulations which stipulate regular blood lead monitoring. Environmental exposure to lead has reduced considerably with the introduction of lead-free petrol, removal of lead from paint, reduction of lead in potable water supplies, removal of lead plumbing, and treatment of water to reduce plumbosolvency. Nevertheless, lead poisoning can still occur, usually as a result of occupational exposure. The intestinal absorption of lead in children is more efficient than adults and lead poisoning can result from ingestion of old paint flakes, which may contain high concentrations of lead.

Blood lead measurement provides a reliable guide to lead exposure; the industrial action limit, which is legally binding, is currently 2.90 µmol/L (60 µg/100 mL). Lead inhibits several enzymes in the haem cycle and so concentrations of several porphyrins increase especially when blood lead exceeds 2.0 µmol/L. At about this concentration other effects may result such as fatigue, depression, irritability, cognitive impairment, headaches and constipation. More severe poisoning may cause anaemia, renal tubular dysfunction and peripheral neuropathy.

The measurement of urinary lead is only recommended for monitoring of chelation therapy or for assessment of exposure to alkyl-leads.

Sample Requirements and Reference Values

Sample Type	Blood, urine, water
Container	Blood: EDTA or lithium heparin. Urine/water: Universal container
Precautions	Blood samples for occupational exposure should be taken at the end of a working shift.
Volume	Blood: 400µL (minimum) (3) Urine / water: 5 to 10 mL (1).
Reference ranges
- blood lead	< 0.5 µmol/L (10 µg/L) < 1.90 µmol/L (40 µg/L) can cause clinical effects (2) < 2.90 µmol/L (60 µg/L) (occupational exposure limit
- zinc protoporphyrin	< 30-80 µmol ZPP/mol Haem (3)
- urine lead	< 110 µg/g creatinine (occupational limit for exposure to organic lead)
- water	< 50 µg/L Current EEC limit for drinking water
Turnaround time	1 week
Method	Graphite furnace / atomic absorption spectrometry

*For assessment of lead in a water supply, two samples are required; a first draw sample in the morning and a further sample taken after running the water for 5 - 10 mins.
**Significant exposure in adults is present when values reach 2.0 µmol/L, and in children 1.35 µmol/L.
***One sample of blood is sufficient for blood lead and porphyrin analysis.