Aggregate exposure assessment, evaluating combined exposures from multiple routes and media, is crucial in children's health risk assessment. Children's unique behaviors and physiology alter exposure rates compared to adults, increasing their susceptibility to certain chemicals during development. The Food Quality Protection Act (FQPA) and amendments to the Toxic Substances Control Act mandate consideration of aggregate exposures in risk assessments. Various organizations have developed methods, but implementation is limited by data availability. ExpoKids aims to visualize the contributions of multiple oral media to aggregate exposures across lifestages, a previously limited area of development. The tool complements the Exposure Factors Interactive Resource for Scenarios Tool (ExpoFIRST) and visually communicates aggregate exposure information using available data. The paper outlines ExpoKids' development, its application to illustrate the contribution of ten oral media to seven lifestage-specific aggregate exposure estimates (ADD and LADD), and evaluates its effectiveness through three case examples.

The introduction mentions several acts and regulations that highlight the importance of aggregate exposure assessment, particularly for children's health. It references the FQPA, Toxic Substances Control Act amendments, and similar approaches in other federal organizations and internationally. The paper also notes that while comprehensive approaches exist, implementation is hindered by data limitations, highlighting the need for tools like ExpoKids.

ExpoKids Version 1.0 was developed in R (Version 3.4.0) to work with ExpoFIRST (Version 2.0), utilizing the EPA's Exposure Factors Handbook (EFH). ExpoFIRST, using EFH, estimates ADDs from intake of ten media (soil, dust, water, breast milk, dairy, meat, fish, vegetables, fruit, grains). ADDs were calculated using the formula: ADD = C × IR × EF × ED / (AT × BW), where C is concentration, IR is intake rate, EF is exposure frequency, ED is exposure duration, AT is averaging time, and BW is body weight. Age-specific central tendency estimates from the EFH were used. Chemical concentrations (C) were from the literature. ExpoFIRST ADD estimates were exported to ExpoKids to create aggregate exposure graphs. ExpoKids recategorizes EFH age groups into seven lifestages (Young Infant, Infant, Young Child, Child, Young Youth, Youth, Adult) for easier comparison. LADDs were calculated by time-weighting each ADD value. Three case examples (DEHP, manganese, endosulfan) were used to evaluate ExpoKids. Data was selected based on evidence of developmental toxicity, critical exposure windows, and available concentration data. PubMed searches and other databases were used to find relevant data, with specific inclusion criteria applied to ensure data quality and representativeness.

ExpoKids generates five graph types: ADD by lifestage, LADD by lifestage, percent ADD by lifestage, ADD for individual exposure pathways, and LADD for individual exposure pathways. The three case studies demonstrated the tool's ability to answer common exposure assessment questions: (1) determining relative media contributions across lifestages to lifetime aggregate exposure; (2) identifying lifestage differences in exposure for essential nutrients with developmental toxicity risks at high levels; and (3) assessing the impact of environmental regulations on aggregate exposure across lifestages. The results from these case studies visually illustrate how different media contribute to exposure at various life stages, highlighting periods of higher vulnerability and potential risk. The graphs allow for comparison across lifestages, media and for the calculation of lifetime exposure.

ExpoKids effectively visualizes aggregate exposure across lifestages and media, addressing the limitations of relying solely on numerical data. The case examples demonstrate its utility in diverse children's health risk assessment scenarios. The tool's ability to integrate with ExpoFIRST and its user-friendly graphical output enhances communication of complex exposure data to various stakeholders. The visualization allows for easier identification of critical exposure windows and the relative contribution of different exposure pathways.

ExpoKids is a valuable tool for visualizing aggregate chemical exposure in children across different lifestages and exposure pathways. Its user-friendly interface and integration with ExpoFIRST make it accessible and effective for assessing children’s health risks. Future development could include expanding the tool to incorporate other exposure routes (dermal, inhalation) and exploring additional data sources to improve the accuracy and comprehensiveness of exposure estimates. Further research using ExpoKids could focus on specific vulnerable populations or investigate emerging contaminants.

The study focuses on oral exposure only, neglecting dermal and inhalation routes. Data availability limits the comprehensiveness of the analysis, and reliance on existing databases might introduce biases. The assumptions made in the calculations, such as using general population parameters, may not represent the full range of individual variability. Furthermore, the concentrations used were based on averages, potentially underrepresenting or overrepresenting exposure for certain sub-populations. Future improvements could incorporate more detailed data on specific chemical concentrations and individual-level exposure factors.