LEAD CONTAMINATION OF UK DUSTS AND SOILS AND IMPLICATIONS FOR CHILDHOOD EXPOSURE - AN OVERVIEW OF THE WORK OF THE ENVIRONMENTAL GEOCHEMISTRY RESEARCH GROUP, IMPERIAL-COLLEGE, LONDON, ENGLAND 1981-1992

Over the course of the last decade, research conducted by the Imperial College Environmental Geochemistry Research Group has focused on the nature and effects of lead in UK dusts and soils. An initial nationwid e reconnaissance survey demonstrated that approximately 10% of the pop ulation is exposed to lead levels in excess of 2,000 mug g-1 in house- hold dust. Subsequent exposure studies revealed that for 2 year old ch ildren in the UK urban environment, approximately 50% of lead intake w as from dust ingested as a result of hand-to-mouth activity. Follow-up computer controlled scanning electron microscopy (CCSEM) analysis of urban household dust and particulate material wiped from children's ha nds showed that important sources of dust lead include lead-based pain t, road dust and soils. CCSEM identification of specific soil lead tra cer particles (from minewaste contaminated soils) in dusts and on chil dren's hands further documented the important role of soil as a source of exposure. Speciation studies of soil lead of this origin indicated that the form of the lead, which is largely influenced by the soil en vironment, is the primary control on bioavailability. It appears that although lead of minewaste origin may be present at elevated levels in dusts and soils, it does not necessarily contribute to elevated blood lead levels when the lead is present in relatively insoluble form.