Science Inventory

The Untapped World of Tap Water Contamination … so many more chemicals than we thought

Citation:

Newton, S., J. Sloop, AND G. Solomon. The Untapped World of Tap Water Contamination … so many more chemicals than we thought. Interagency Water Research Planning Workshop, Virtual, NC, May 14, 2024. https://doi.org/10.23645/epacomptox.26026279

Impact/Purpose:

N/A

Description:

The Tap Water Analysis Project was a multi-year study that used targeted and non-targeted analysis (NTA) methods to survey chemical contaminants in drinking water from five regions across the state of California. For the NTA portion of the project, activated carbon point-of-use (POU) drinking water filters were installed on faucets in 46 homes from these five regions. POU filters have been previously shown to accumulate a wide variety of organic contaminates in up to 200 gallons of water, providing ample contaminant mass, which can be advantageous for NTA. Both gas and liquid chromatography with high resolution mass spectrometry were used for the NTA to maximize the chemical space coverage. A prioritization equation was formulated to help select candidate compounds for confirmation that combined measured data, such as chromatographic abundance and sample detection frequency, with candidate compound metadata, such as predicted or experimental hazard and toxicity data. Principal component analysis was used to identify the most unique samples in terms of contaminant composition and variability. Furthermore, a random forest model was constructed to classify samples by region. Features with the highest Gini indices were more closely examined and considered for confirmation, as these features played an important role in distinguishing between sampling regions. In total, 38 compounds were confirmed using reference chemicals, some of which were also detected using targeted methods from the same locations (performed by other partners in the TAP project). Among the compounds confirmed were perfluoroalkyl substances (PFAS), pesticides, disinfection byproducts, and chemicals used in consumer products. Novel compound elucidation was explored and yielded the discovery of a novel PFAS which exhibited a similar occurrence pattern to confirmed PFAS. These findings indicate many more compounds exist in drinking water than are typically monitored for and demonstrate the utility of combining POU sampling with NTA.