A Meta‐Analysis of Children's Hand‐to‐Mouth Frequency Data for Estimating Nondietary Ingestion Exposure

Because of their mouthing behaviors, children have a higher potential for exposure to available chemicals through the nondietary ingestion route; thus, frequency of hand‐to‐mouth activity is an important variable for exposure assessments. Such data are limited and difficult to collect. Few published studies report such information, and the studies that have been conducted used different data collection approaches (e.g., videography versus real‐time observation), data analysis and reporting methods, ages of children, locations, and even definitions of “mouthing.” For this article, hand‐to‐mouth frequency data were gathered from 9 available studies representing 429 subjects and more than 2,000 hours of behavior observation. A meta‐analysis was conducted to study differences in hand‐to‐mouth frequency based on study, age group, gender, and location (indoor vs. outdoor), to fit variability and uncertainty distributions that can be used in probabilistic exposure assessments, and to identify any data gaps. Results of this analysis indicate that age and location are important for hand‐tomouth frequency, but study and gender are not. As age increases, both indoor and outdoor hand‐to‐mouth frequencies decrease. Hand‐to‐mouth behavior is significantly greater indoors than outdoors. For both indoor and outdoor hand‐to‐mouth frequencies, interpersonal, and intra‐personal variability are ∼60% and ∼30%, respectively. The variance difference among different studies is much bigger than its mean, indicating that different studies with different methodologies have similar central values. Weibull distributions best fit the observed data for the different variables considered and are presented in this article by study, age group, and location. Average indoor hand‐to‐mouth behavior ranged from 6.7 to 28.0 contacts/hour, with the lowest value corresponding to the 6 to