Transient Multimedia Model for Investigating the Influence of Indoor Human Activities on Exposure to SVOCs
Recent empirical evidence suggests that human occupants indoors influence the dynamics of SVOCs and associated human exposures. To better understand these dynamics, a transient multimedia human exposure model (ABICAM) was developed, which parameterizes mass-balance equations as functions of time-dependent human activities. As a case study, ABICAM simulated exposures of an archetypal toddler and adult over 24 hours to diethyl phthalate (DEP), butyl benzyl phthalate (BBzP), and diethylhexyl phthalate (DEHP) that span a wide range of gas-particle partitioning tendencies. Under baseline (no activities beyond respiration), the toddler’s time-average internal dose [( Dose(t)) ̅] values were three to four times higher than the adult’s (DEP and DEHP, respectively), based on differences in physical human attributes. When time-dependent activities were considered, exposure differences were accentuated by up to a factor of three for BBzP. Activities with the greatest influence on ( Dose(t)) ̅ were showering (-71% for BBzP), cooking (+27% for DEHP), and sleeping (-26% for DEHP). Overall, the results supported the hypotheses that 1) transient indoor activities can give rise to intraindividual variability in estimated internal exposure to SVOCs that are rapidly metabolized, and 2) interindividual variability in such exposure can result from differences in activity patterns and physical human attributes, according to physical-chemical properties.