The relationships between heavy metals in garden soils and house dusts in an old lead mining area of North Wales, Great Britain

Lead in house dust may be an important source of this metal for children and it has been suggested that the mineral components of dust as well as lead and other trace elements are derived, in part, from garden soil. This proposed relationship between soil and dust trace metal composition was investigated in north Wales, in an area where lead mining has caused intensive and extensive heavy metal contamination of agricultural and garden soils, and in a control area. Paired garden and house dust samples were collected from the houses of random samples of 90 subjects and were analysed for Cd, Cu, Pb and Zn. Compared with soils from the control village the contaminated soils were enriched (ratios of geometric means) by factors of Cd = 6·7, Cu = 1·1, Pb = 14·1 and Zn = 3·8. The similar ratios for dust were Cd = 1·2, Cu = 1·1, Pb = 1·9 and Zn = 1·1. Correlation analysis suggested that soil contributes little Cd, Cu or Zn to dust but 27% of the variability in dust Pb could be explained by soil Pb and the gradient of the log-dust Pb/log-soil Pb regression was 0·3. Subsequent resampling in 11 houses demonstrated little change over two months in dust Cd, Cu or Zn concentrations. Pb levels did change and were poorly correlated in the two sample sets, which may be explained by differences in the amounts of contaminated soil carried into the house before the dust was sampled.