Semivolatile organic compounds in homes: strategies for efficient and systematic exposure measurement based on empirical and theoretical factors

Abstract

Residential exposure can dominate total exposure for commercial chemicals of health concern; however, despite the importance of consumer exposures, methods for estimating household exposures remain limited. We collected house dust and indoor air samples in 49 California homes and analyzed for 76 semivolatile organic compounds (SVOCs)--phthalates, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and pesticides. Sixty chemicals were detected in either dust or air and here we report 58 SVOCs detected in dust for the first time. In dust, phthalates (bis(2-ethylhexyl) phthalate, benzyl butyl phthalate, di-n-butyl phthalate) and flame retardants (PBDE 99, PBDE 47) were detected at the highest concentrations relative to other chemicals at the 95th percentile, while phthalates were highest at the median. Because SVOCs are found in both gas and condensed phases and redistribute from their original source over time, partitioning models can clarify their fate indoors. We use empirical data to validate air-dust partitioning models and use these results, combined with experience in SVOC exposure assessment, to recommend residential exposure measurement strategies. We can predict dust concentrations reasonably well from measured air concentrations (R(2) = 0.80). Partitioning models and knowledge of chemical Koa elucidate exposure pathways and suggest priorities for chemical regulation. These findings also inform study design by allowing researchers to select sampling approaches optimized for their chemicals of interest and study goals. While surface wipes are commonly used in epidemiology studies because of ease of implementation, passive air sampling may be more standardized between homes and also relatively simple to deploy. Validation of passive air sampling methods for SVOCs is a priority.

Figure 1

Schematic illustration of SVOCs in air and dust indoors. Equations 1 (partitioning between gas-phase and total SVOCs in air) and 2 (partitioning between gas-phase air and dust) are described in the text.

Figure 2

Predicted dust concentrations (micrograms/gram) versus measured dust concentrations (micrograms/gram) for 17 SVOCs with at least 50% detection frequency in both indoor air and dust. Predictions made using measured air concentrations in the same homes. Dashed line represents 1:1 line or perfect prediction. Individual points shown (unshaded symbols); however, regression model fit to median concentrations (large shaded circles).

Figure 3

Predicted air concentration (nanograms/cubic meter) from measured dust and measured air concentration for chemicals with at least 50% detection frequency in dust. Predictions are presented next to measured concentrations to compare range of concentrations expected and observed. Predictions are only made using detected dust concentrations. Red line represents study-specific maximum method reporting limit (MRL) for each chemical (MRL calculated on mass basis; variations in MRL attributed to volume differences). Note log-scale.