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.
Lead poisoning may occur in various ethnic populations following ingestion of traditional remedies or application of eye cosmetics. This is the commonest form of lead poisoning in children. Investigation of lead isotopes may be useful in investigating suspected cases. 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. Zinc protoporphyrin can be measured as an alternative marker although this analyte also falls in patients with iron deficiency anaemia. 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 Ranges for Lead
|Sample Type||Blood, urine, water|
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.|
Blood: 300 µL
Blood Lead: < 0.25 µmol/L (5 µg/100mL)
> 2.0 µmol/L (40 µg/100mL) (can cause clinical effects)
> 2.90 µmol/L (60 µg/100mL) (occupational exposure limit)
ZPP: < 30 to 80 nmol/mol haem
Urine lead: < 110 µg/g creatinine (occupational exposure limit)
Water: < 50 µg/L Current EEC limit for drinking water
1 week (please telephone 0141 211 4494 if immediate turnaround required)
|Method||Graphite furnace / atomic absorption spectrometry|
- For assessment of lead in water, 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.
* This is the absolute minimum volume; these volumes are insufficient to carry out a repeat analysis in the event of an analytical problem.