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MODELING APPROACHES FOR ESTIMATING THE DOSIMETRY OF INHALED TOXICANTS IN CHILDREN
Citation:
GINSBERG, G. L., B. ASGHARIAN, J. S. KIMBELL, J. S. ULTMAN, AND A. M. JARABEK. MODELING APPROACHES FOR ESTIMATING THE DOSIMETRY OF INHALED TOXICANTS IN CHILDREN. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. Taylor & Francis, Inc., Philadelphia, PA, 71(3):166-95, (2008).
Impact/Purpose:
This is a summary article of a session at a workshop sponsored by the Office of Children’s Health in Washington DC in June 2006. The objective of the workshop was to evaluate different approaches (e.g., at EPA and California EPA) and the state-of-the-science (e.g., different models of gas uptake and particle distribution) with respect to whether they are adequately addressing issues that may make children more at risk from such inhaled agents. The purpose of this session was to compare simulation exercises with different existing models and provide background on default algorithms of US EPA (1994) methods.
Description:
Risk assessment of inhaled toxicants has typically focused upon adults, with modeling used to extrapolate dosimetry and risks from laboratory animals to humans. However, behavioral factors such as time spent playing outdoors can lead to more exposure to inhaled toxicants in children. Depending on the inhaled agent and the age and size of the child, children may receive a greater internal dose than adults because of greater ventilation rate per body weight or lung surface area, or metabolic differences may result in different tissue burdens. Thus, modeling techniques need to be adapted to children in order to estimate inhaled dose and risk in this potentially susceptible life stage. This paper summarizes a series of inhalation dosimetry presentations from the U.S. EPA’s Workshop on Inhalation Risk Assessment in Children held on June 8-9, 2006 in Washington, DC. These presentations demonstrate how existing default models for particles and gases can be adapted for children, and how more advanced modeling of toxicant deposition and interaction in respiratory airways can take into account children’s anatomy and physiology. These modeling efforts identify child-adult dosimetry differences in respiratory tract regions that may have implications for children’s vulnerability to inhaled toxicants. A decision framework is discussed that considers these different approaches and modeling structures including assessment of parameter values, supporting data, reliability, and selection of dose metrics.