Student Research: Amelia Greenhall
MS, , 2011
Assessment of Children's Non-Dietary Indoor Exposure to a Phthalate Found in Floor Tile
Semi-volatile organic chemicals (SVOCs) are ubiquitous and persistent in the indoor environment, and biomonitoring data shows widespread human exposure. Estimates of the magnitude and route of these exposures are needed to inform consumer product regulations. Children are of special concern, because of their unique behavioral patterns and lower body masses. Organic films have been found on sampled indoor surfaces and theoretically could be expected to occur on all indoor surfaces, providing reservoirs for SVOCs and potential exposure.
A fugacity based model was developed to evaluate the pathways that contribute to children's aggregate exposure indoors. The model combines an environmental fate and transport model with a physiologically based phamacokinetic model of a human, and includes ubiquitous organic surface films and a finite-difference membrane skin. The compartments are implemented as a series of differential equations solved in Matlab. In an initial implementation the model is applied to a scenario in which di-ethylhexyl phthalate (DEHP) is released from kitchen floor tile. A typical kitchen floor might contain 20 kg of DEHP, and given a release rate on the order of grams per year, effectively an infinite source. Ultimately, predicted exposures are compared to estimates based on biomonitioring of metabolites in urine and measured air and dust concentrations. Initial calculations suggest that organic films provide a large reservoir for exposure.