Methods for a comprehensive targeted and suspect screen survey of exogenous chemicals in shed baby teeth

Background: Semi-volatile organic chemicals (SVOCs) have been studied in shed baby teeth as a potential tool to identify environmental triggers of autism. However, these targeted studies are limited by the availability of standards, leaving a vast number of chemicals unexplored for autism risk. Objective: We explored the use of two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) as a viable and accurate method for identifying and quantifying a wide range of low-level SVOCs in deciduous teeth. Methods: Tooth samples were derived from The Autism Tooth Fairy Study. Ground tooth samples (n = 44) were analyzed using GCxGC-TOFMS. Targeted and non-targeted analyses were performed. Targeted compounds were reviewed against reference spectra for identification, and non-targets were manually curated using the National Institute of Standards and Technology Library data, as available. Kovat's retention index was used for identifications without a reference standard. Results: From the 44 tooth samples analyzed, 11,971 total endogenous and exogenous features were cataloged, including unknowns without a suitable library match. Of the 203 compounds detected, 106 high-fidelity matched compounds were identified spanning 45 subclasses of toxicants. Eighty-nine of these compounds are known developmental toxicants or endocrine disruptors. The remaining compounds were toxicants with acute or chronic toxicity data but had no developmental or endocrine-disrupting activity data. Conclusion: This study demonstrates the utility of GCxGC-TOFMS for detecting a wide range of SVOCs in children's teeth, identifying a substantial number of developmental toxicants and other toxic chemicals. The detection of these compounds highlights critical gaps in our understanding of children's chemical exposures.