Age-related changes to environmental exposure: variation in the frequency that young children place hands and objects in their mouths

Children are exposed to environmental contaminants through direct ingestion of water, food, soil, and feces, and through indirect ingestion due to mouthing hands and objects. We quantified ingestion among 30 rural Bangladeshi children <4 years old, recording every item touched or mouthed during 6-h video observations that occurred annually for 3 years. We calculated the frequency and duration of mouthing and the prevalence of mouth contacts with soil and feces. We compared the mouthing frequency distributions to those from US children to evaluate the appropriateness of applying the US data to the Bangladeshi context. Median hand mouthing frequency was 97–160？times/h and object mouthing 23–50？times/h among the five age groups assessed. For more than half of the children, >75% of all hand mouthing was associated with eating. The frequency of hand mouthing not related to eating was similar to the frequency of all hand-mouthing among children in the US. Object-mouthing frequency was higher among Bangladeshi children compared to US children. There was low intra-child correlation of mouthing frequencies over our longitudinal visits. Our results suggest that children’s hand- and object-mouthing vary by geography and culture and that future exposure assessments can be cross-sectional if the goal is to estimate population-level distributions of mouthing frequencies. Of all observations, a child consumed soil in 23% and feces in 1%