The Trace Elements Section of the Laboratory has had Supraregional Assay Service (SAS) designation since 1974, and is on the list of laboratories approved by the Health and Safety Executive for the occupational monitoring of lead and cadmium. Analysis is performed mainly by atomic absorption spectroscopy (flame and electrothermal) and by ICP-MS. Performance is monitored by extensive participation in a number of External Quality Assessment Schemes: NEQAS (blood lead and cadmium); TEQAS (eight analytes in blood, serum and urine): SAS (blood lead, serum aluminium, copper and zinc): Quebec (eight analytes in blood, serum and urine). In addition, each batch analysis is monitored by the inclusion of internal quality control materials.