| An understanding of hand and mouthing contact behaviors is important to accurately estimating dermal and nondietary ingestion exposure to environmental contaminants. This dissertation aims to reduce data gaps in the understanding of children's contact behaviors by utilizing the large dataset of microactivity data that Stanford's Exposure Research Group has collected over the past decade. In this dataset, microactivities (i.e., detailed contact behaviors) were collected via videotaping. Two distinct datasets were analyzed. One dataset focused on children's contact behaviors in outdoor residential locations. The other contains longitudinal data collected for one child over a period of seven years. Data were analyzed to explore correlations between contact behaviors and factors such as age, location, gender, and macroactivity (i.e., general activities such as reading and walking). The fraction of total hand surface area involved in hand contacts was estimated using data from the outdoor study. Lastly, multiple algorithms were implemented to explore a novel method to simulate children's contact behaviors via block resampling of microactivities associated with distinct blocks of macroactivities.; Results showed that median mouthing contact frequencies ranged from <1 to 136 seconds while median hand-to-object contacts ranged from <1 to 5 seconds. Children ≤24 months old had longer hourly mouthing contact durations with the hand than children >24 months old. Both hand and mouthing contact frequencies were higher indoors than outdoors. Frequency and hourly contact duration of hand contacts with total objects increased with age. Girls had higher mouthing contact frequencies but shorter hourly mouthing contact durations with the hands than boys. Additionally, children's hand contacts with relevant objects were found to be highly correlated with the three macroactivities studied (i.e., "Playing with animal", "Playing on playset", and "Playing with vegetation"). Quantification of the fraction of total hand surface area involved in children's outdoor contacts showed that a fractional value of 0.31 captured 80-100% contact surface area involved in children's hand contacts. Lastly, evaluation of a novel method to simulate macroactivity and microactivity time series data using block resampling showed that block resampling can be a valid way to simulate extended children's contact activity time series. |
