Estimating soil ingestion: the use of tracer elements in estimating the amount of soil ingested by young children.

In this pilot study, we modified methods used in estimating the amount of soil ingested by ruminants to measure soil ingested by children. Using aluminum, silicon, and titanium as tracers, we estimated soil ingestion for 59 children aged 1-3 yr from East Helena, Montana. Estimated daily soil ingestion based on aluminum and silicon concentrations were 181 and 184 mg/day, respectively, whereas the estimate based on the titanium concentration was about 10 times higher, 1,834 mg/day. Although we do not consider these estimates accurate measures of soil ingestion, the method we used is a reasonable approach that, to our knowledge, has not been used before in humans. However, our estimates will be revised as refinement of this method and better understanding of the metabolism of aluminum, silicon, and titanium lead to more accurate data for analysis.