Quantitative estimates of soil ingestion in normal children between the ages of 2 and 7 years: population-based estimates using aluminum, silicon, and titanium as soil tracer elements.

This investigation was undertaken to provide quantitative estimates of soil ingestion in young children on a population basis, and to identify demographic and behavioral characteristics that influence the amount of soil ingested. A total of 104 children between the ages of 2 and 7 yr were selected randomly from the population of a three-city area in southeastern Washington State. Using aluminum, silicon, and titanium as tracer elements, a mass-balance approach was employed to assess daily soil ingestion. A duplicate of all food items consumed, all feces, and some urine excreted were collected on 4 consecutive d, along with soil and house dust samples from each child's home. Samples were analyzed by x-ray fluorescence spectrometry. After adjustment of the soil ingestion estimates to account for missing food, excreta samples, and nonfood items consumed, the average daily values based on the three tracer elements were: aluminum, 38.9 mg/d (median = 25.3 mg/d); silicon, 82.4 mg/d (median = 59.4 mg/d); and titanium, 245.5 mg/d (median = 81.3 mg/d). No consistent pattern emerged regarding a demographic or behavioral profile that was predictive of soil ingestion. This work demonstrates (a) the feasibility of conducting large-scale studies to determine soil intake levels in human populations, (b) provides estimates of soil ingestion in small children based on a random population sample, and (c) suggests several possibilities for additional research initiatives in this area.