Food Safety and Environmental Stewardship Program

BACKGROUND: Silicone personal samplers are increasingly being used to measure chemical exposures, but many of these studies do not attempt to calculate environmental concentrations.

OBJECTIVE: Using measurements of silicone wristband uptake of organic chemicals from atmospheric exposure, create log K and k predictive models based on empirical data to help develop air equivalency calculations for both volatile and semi-volatile organic compounds.

METHODS: An atmospheric vapor generator and a custom exposure chamber were used to measure the uptake of organic chemicals into silicone wristbands under simulated indoor conditions. Log K models were evaluated using repeated k-fold cross-validation. Air equivalency was compared between best-performing models.

RESULTS: Log K and log k estimates calculated from uptake data were used to build predictive models from boiling point (BP) and other parameters (all models: R = 0.70-0.94). The log K models were combined with published data and refined to create comprehensive and effective predictive models (R: 0.95-0.97). Final estimates of air equivalency using novel BP models correlated well over an example dataset (Spearman r = 0.984) across 5-orders of magnitude (<0.05 to >5000 ng/L).

SIGNIFICANCE: Data from silicone samplers can be translated into air equivalent concentrations that better characterize environmental concentrations associated with personal exposures and allow direct comparisons to regulatory levels.