Unprecedentedly High Dust Ingestion Estimates for the General Population in a Mining District of DR Congo

The mining of metals in low income countries is often associated with high exposure to dust that contributes to metal exposure. Here, dust ingestion estimates were made from fecal excretion of inert tracers with corrections for dietary contribution. The study took place in the cobalt mining area of Lubumbashi (DR Congo) and involved 120 nonoccupationally exposed participants in the dry season, with 51 of these being repeated in the rainy season. For each participant, duplicate meals (0-96 h), feces (24-120 h), and indoor/outdoor dust (<250 μm) were collected. The dust ingestion estimates (g day^-1) were derived from Nb, Ti, and V as best tracers and were 0.28 (geometric mean), 3.3 (mean), and 13 (P95); these values are almost a factor 10 above currently accepted estimates for the general population in high income countries. Mean dust ingestion in the dry season was twice that of the rainy season, and the P95s were significantly higher in children (3-15 years) than in male adults and toddlers; geophagy (>40 g day^-1) was suspected in three individuals. These data explain the previously reported extreme cobalt exposures in children and support the need to manage dust in the metal mining operations.