How should we characterize emissions, transport, and the resulting exposure to SVOCs in the indoor environment?

A systematic and efficient strategy is needed to assess and manage the potential risks to human health that arise from the manufacture and use of thousands of chemicals.  For both volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), exposure is strongly influenced by the types of materials and products in which the VOC or SVOC occur, the concentration of the VOC or SVOC in the material or product, the way in which the material or product is used or applied indoors, and the ventilation rate within the room or building.  For VOCs, the rate of emissions from various materials and products are generally characterized in small chambers.  The results are scaled up to represent what happens in a larger room, and then used to estimate the expected gas-phase concentration and associated health effects.  For SVOCs, however, the characteristics of the room play a much larger role in controlling the process of emissions, transport, and exposure.  For example, partitioning of SVOCs to interior surfaces including walls, windows, furniture, clothing, dust and airborne particles, all substantially affect the emissions and transport processes, as well as the resulting exposure.  Given the inherent complexity of the situation, what is needed is a screening-level approach which is based on rapid estimates of exposure to a specific SVOC that is present within a specific material or product.  These rapid estimates of exposure are then combined with estimates of toxicity to create a screening-level estimate of the risk associated with the specific SVOC/product combination.  The SVOC/product combinations with relatively high risks can then be evaluated, focusing on more accurate measurements of the key parameters that govern emissions, transport, and the resulting exposure to SVOCs in the indoor environment.  Among available tools for evaluating these key parameters, there are significant gaps associated with the SVOCs.  To close these gaps, we have developed simple methods to measure some of the key parameters.  These parameters include the gas-phase concentration in equilibrium with the product surface, the partition coefficient between air and indoor surfaces, the vapor pressure of liquid SVOCs, and the partition coefficient between air and airborne particles.  Phthalates in polyvinyl chloride flooring were selected to test these measurement methods, with results that agree well with those measured in previous, more sophisticated tests.  As increasing numbers of these measurements are completed, the overall approach should substantially improve our ability to estimate the potential exposure to SVOCs in indoor environments and can help with the risk-based prioritization of a wide range of chemicals and products.