House-dust metal content and bioaccessibility: a review

Children ingest house settled dust by normal hand to mouth activity. Because house dust contains some metals associated with health hazards, this pathway of exposure is an issue in health risk assessment. The concentration of metals in house dust is thus a matter of concern, together with their bioaccessibility, that is, the fraction absorbed by humans. This review examines articles studying the metal content (excluding Pb) in the household dust in ordinary homes. Relatively few articles report the concentrations and bioaccessibility of metals in settled dust. Ag, As, Al, Au, Ba, Be, Bi, Br, Ca, Cd, Ce, Co, Cr, Cu, Fe, Hf, Hg, I, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Rb, Sb, Sc, Se, Sm, Sn, Sr, Te, Th, Ti, U, V and Zn have been studied. Al, Ca, Fe, K, Mg, Na and P are found in concentrations exceeding 1000 mu g.g(-1). Bioaccessibility is documented still more rarely and varies substantially between and within metals (Ag, 60-90%; As, 10-90%; Al, 10-80%; Cd, 50-90%; Co, 15-50%; Cr, 10-50%; Cu, 20-80%; Fe, 5-45%; Hg, 10%; Mn, 40-60%; Ni, 20-80%; Sn, 5-10%; U, 10-30%; Zn, 80-90%). It depends on chemical speciation, particle size and organic carbon, which play a role in metal partitioning among mineral and organic phases and thus in the digestion process. Digestion conditions: temperature, pH, duration and type of acid used are thus essential parameters that determine the metal concentrations measured in dust. House-dust concentrations of metals and metalloids vary throughout a home as well as between homes and across seasons and locations. House-dust metal content has also changed over time due to the decrease in industrial emissions in some regions and the evolution of automobile ones. Furthermore, soil metal concentration cannot predict indoor dust metal concentrations. It is thus difficult to predict metal content or its bioaccessibility. Local measurements are therefore essential for consideration of this background exposure.