Open Science for Identifying “Known Unknown” Chemicals

High resolution mass spectrometry (HR-MS) has expanded assessment of chemical exposure in the environment well beyond screening for a limited subset of target ("known") chemicals."Suspect screening" has evolved into an efficient and popular way to screen for hundreds to thousands of chemicals of interest (the "known unknowns" or "suspects") in complex samples, based initially only on their molecular formula and the resulting calculated exact mass. 1 However, the exact mass is insufficient evidence for unequivocal identification. 2Challenges facing comprehensive suspect screening include increasing chemicals of interest (tens of thousands), as well as everdecreasing detection limits, leading to increased false positives. 1Addressing these challenges requires a foundation of cheminformatics tools and database resources freely available to the community to enable exchange of information between diverse communities and the pooling of resources toward a common good.Thus, open science is poised to play a pivotal role in the evolution of suspect screening.