Substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs) are over 70 000 "complex" chemical mixtures produced and used at significant levels worldwide. Due to their unknown or variable composition, applying chemical assessments originally developed for individual compounds to UVCBs is challenging, which impedes sound management of these substances. Across the analytical sciences, toxicology, cheminformatics, and regulatory practice, new approaches addressing specific aspects of UVCB assessment are being developed, albeit in a fragmented manner. This review attempts to convey the "big picture" of the state of the art in dealing with UVCBs by holistically examining UVCB characterization and chemical identity representation, as well as hazard, exposure, and risk assessment. Overall, information gaps on chemical identities underpin the fundamental challenges concerning UVCBs, and better reporting and substance characterization efforts are needed to support subsequent chemical assessments. To this end, an information level scheme for improved UVCB data collection and management within databases is proposed. The development of UVCB testing shows early progress, in line with three main methods: whole substance, known constituents, and fraction profiling. For toxicity assessment, one option is a whole-mixture testing approach. If the identities of (many) constituents are known, grouping, read across, and mixture toxicity modeling represent complementary approaches to overcome data gaps in toxicity assessment. This review highlights continued needs for concerted efforts from all stakeholders to ensure proper assessment and sound management of UVCBs.
Pharmaceuticals and
their transformation products (TPs) are continuously
released into the aquatic environment via anthropogenic activity.
To expand knowledge on the presence of pharmaceuticals and their known
TPs in Luxembourgish rivers, 92 samples collected during routine monitoring
events between 2019 and 2020 were investigated using nontarget analysis.
Water samples were concentrated using solid-phase extraction and then
analyzed using liquid chromatography coupled to a high-resolution
mass spectrometer. Suspect screening was performed using several open
source computational tools and resources including Shinyscreen (), MetFrag (), PubChemLite (), and MassBank (). A total of 94 pharmaceuticals, 88 confirmed at a level 1 confidence
(86 of which could be quantified, two compounds too low to be quantified)
and six identified at level 2a, were found to be present in Luxembourg
rivers. Pharmaceutical TPs (12) were also found at a level 2a confidence.
The pharmaceuticals were present at median concentrations up to 214
ng/L, with caffeine having a median concentration of 1424 ng/L. Antihypertensive
drugs (15), psychoactive drugs (15), and antimicrobials (eight) were
the most detected groups of pharmaceuticals. A spatiotemporal analysis
of the data revealed areas with higher concentrations of the pharmaceuticals,
as well as differences in pharmaceutical concentrations between 2019
and 2020. The results of this work will help guide activities for
improving water management in the country and set baseline data for
continuous monitoring and screening efforts, as well as for further
open data and software developments.
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