Lead is a poison that affects virtually every system in the body. It is particularly harmful to young children. Very severe lead exposure in children (blood lead >= 70 µg/dL ) can cause coma, convulsions, and even death.  Lower levels can cause adverse effects on the central nervous system, kidney, and hematopoetic system. Blood lead levels as low as 10 µg/dL are associated with decreased intelligence and impaired neurobehavioral development. Other effects begin at these low blood lead levels, including decreased growth, decreased hearing acuity, and decreased ability to maintain a steady posture.

PRINCIPLES OF THE TEST:  The laboratory determines the concentration of lead in human blood samples by using graphite furnace atomic absorption spectrophotometry (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS) manufactured by Perkin-Elmer. 

In GFAAS the whole blood sample is combined with nitric acid and a wetting solution to a 1:10 dilution.  The sample is automatically pipetted onto a platform in  a graphite tube.  The sample is dried and charred with a high temperature program, then atomized at approximately 1650 °C in the graphite tube.  The absorption of excited lead atoms is measured at lead's characteristic wave length of 283.3 nm.  Metallic elements in the ground state will absorb light of the same wavelengths they emit when excited.  A hollow cathode lamp whose light source is made of lead is used as the source.  The sample is atomized by the high temperature in the furnace.  The lead atoms release absorbed light at their characteristic wavelength, 283.3 nm., in proportion to their concentration in the graphite tube.

In ICP-MS both whole blood and spotted capillary blood samples are analyzed.  The samples are treated with a diluent then automatically pumped to the instrument nebulizer.  This atomizes the solution into radio frequency plasma where ionization takes place.  A vacuum interface pulls the ions through a series of cones and a focusing lens.  At this point the positively charged ions enter the quadrupole where the ions are separated by their mass to charge ratio.  The ions transmitted through the quadrupole are detected by an electron multiplier, and processed by the data handling system.

Jeffrey Dupler, Section Manager
517-335-8244
duplerj@michigan.gov

Related Information:

Lead Hazard Remediation Program & Childhood Lead Poisoning Preventation