Monitoring programs for drinking water rely on targeted methods that cover a limited number of compounds. In an effort to advance suspect screening analysis (SSA) methodologies and more fully characterize the drinking water exposome, point-of-use water filtration devices (BritaTM filters) were employed to collect time-integrated (1-2 months) drinking water samples in a pilot study of nine central North Carolina homes. Filters were Soxhlet extracted and analyzed by HPLC-TOFMS. Formulas obtained using high-resolution mass spectral data were searched against the US EPA’s Comptox Chemistry Dashboard, a recently developed web application and data hub for almost 750,000 chemical substances. Candidate compounds were ranked by number of data sources to assign the most likely compound for each formula. Toxicity data from EPA’s Tox21/ToxCast program and exposure estimates from US EPA’s ExpoCast program, also available via the dashboard, were then used in conjunction with compound detection frequency and abundance across all samples to calculate a “ToxPi” ranking for each candidate compound to prioritize those of greatest interest. Out of 14,922 molecular features in the samples, 430 were assigned molecular formulas with a match score &gt; 90, which mapped to 10,621 candidate compounds. Of these, 91 compounds were found as having the highest number of data sources, as well as the highest ToxPi ranking for their molecular formula, and were thus grouped as the highest priority compounds. Standards were available on-hand for sixteen priority compounds and were confirmed as being correctly identified, giving us confidence in the correct identification of the other 75. Product-use categories from EPA’s CPCat database, again available via the CompTox dashboard, revealed that the majority of priority compounds are associated with industrial processes indicating that drinking water in central North Carolina may be impacted by local industries. Most of the priority compounds are not listed in the Safe Drinking Water Act and would not have been discovered without the use of SSA. This pilot scale application appears to be a viable monitoring technique that could be employed in future exposure studies to better understand the contribution from drinking water.

Screening of a large number of trace organic compounds in drinking water using point-of-use filters and suspect screening analysis

254th National Meeting (2017)

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