Child Exposure Facotrs in Taiwan -- Research on children for non-dietary exposure and mouthing frequ
Harmful substances in soil and dust may enter human body through the direct inhalation, digestion, and dermal contact and cause adverse health effects. For children, the extent of soil and dust ingestion is an important exposure factor. The objective of this study is to establish a soil exposure database for infants and toddlers living around the contaminated sites. We selected a contaminated site and a control site at northern, middle, southern and eastern parts of Taiwan respectively and collected the soil, dust and children’s feces to estimate the localized mouthing information and quantify soil/dust ingestion for infants and toddlers. The soil texture was classified as loamy sand to sandy loam in the contaminated and control sites of the northern, middle, southern and eastern parts of Taiwan. The concentrations of titanium, aluminum and silicon in the soils from contaminated and control sites soil were within 3.33- 15.5, 0.49- 47.4 and 0.07– 328 g/kg, and 2050- 2180 mg/kg, <13.2- 1490 mg/kg, and <17.8-105000 mg/kg, respectively. The concentrations of titanium, aluminum and silicon in the feces were within 137- 3770, <13.2- 510 and 14.0- 14800 mg/kg, respectively. For the 48 children in this study, the median total objects/surface mouthing frequency was 36.7 events/h. The median hand-to-mouth and object-to-mouth frequencies were 8.58 and 10.0 events/h. Additionally, the median total objects/surface mouthing duration was 2.50 min/h. The median hand-to-mouth and object-to-mouth duration was 0.29 and 0.35 min/h. The median hand-to-moth and object-to-mouth frequencies and duration were not significantly different in terms of gender, location, living around a contaminated site or a control site, income, and pacifier use. The object-to-mouth frequency and duration was only correlated to age, namely, the median object-to-mouth frequency and duration were smaller in the older children, which was significantly different. The median (mean) infant and toddler soil ingestion were estimated 878(960), 21.0(31.4) and 145(681) mg/day, based on the content of titanium, aluminum and silicon, respectively. When the contribution of these tracers from food was excluded, the median (mean) soil ingestion were estimated 957(1980) and 177(284) mg/day, based on the content of titanium and silicon, respectively. These analytical results also suggest that the soil ingestions for children living in the northern, middle, southern and eastern part s of Taiwan were not significantly different. According to the results in this phase I project, we suggest that titanium and silicon were suitable tracer elements for evaluating soil and dust ingestion of infants and toddlers. We also suggest that the dietary samples should be collected and counted to more accurately estimate the soil and dust ingestion in our phase II study.
Contaminated sites, Titanium, Silicon, Soil/dust ingestion