Cm-History Method, a Novel Approach to Simultaneously Measure Source and Sink Parameters Important for Estimating Indoor Exposures to Phthalates

The concentration of a gas-phase semivolatile organic compound (SVOC) in equilibrium with its mass-fraction in the source material, y(0), and the coefficient for partitioning of an SVOC between clothing and air, K, are key parameters for estimating emission and subsequent dermal exposure to SVOCs. Most of the available methods for their determination depend on achieving steady-state in ventilated chambers. This can be time-consuming and of variable accuracy. Additionally, no existing method simultaneously determines y(0) and K in a single experiment. In this paper, we present a sealed-chamber method, using early-stage concentration measurements, to simultaneously determine y(0) and K. The measurement error for the method is analyzed, and the optimization of experimental parameters is explored. Using this method, y(0) for phthalates (DiBP, DnBP, and DEHP) emitted by two types of PVC flooring, coupled with K values for these phthalates partitioning between a cotton T-shirt and air, were measured at 25 and 32 degrees C (room and skin temperatures, respectively). The measured y(0) values agree well with results obtained by alternate methods. The changes of y(0) and K with temperature were used to approximate the changes in enthalpy, Delta H, associated with the relevant phase changes. We conclude with suggestions for further related research.