@article {288, title = {Fast autoxidation of unsaturated lipid films on indoor surfaces.}, journal = {Nat Commun}, volume = {16}, year = {2025}, month = {2025 Feb 12}, pages = {1557}, abstract = {

Organic films containing unsaturated lipids are widespread, yet their oxidation pathways with associated impacts on contaminant lifetimes and human exposure remain poorly explored under indoor environmental conditions. This study demonstrates that UVA radiation and radical exposure drive rapid autoxidation of thin films of methyl linolenate (ML) and canola oil (which contains polyunsaturated triglycerides), primarily producing organic hydroperoxides. For ML films this fast chemistry occurs at the same rate under entirely dark, genuine indoor conditions as it does when the films are exposed to significantly higher OH radicals in a flow reactor. Both OH and organic radicals are detected within the oxidized films, propagating fast autoxidation in dark indoor environments with minimal sensitivity to the radical initiation rate. When mixed into the films, bisphenol A is hydroxylated, illustrating potential transformation pathways for toxic organic contaminants. This study uncovers insights into lipid autoxidation processes under environmental conditions and underscores their potential health impacts.

}, keywords = {Benzhydryl Compounds, Bisphenol A Compounds, Fatty Acids, Monounsaturated, Humans, Hydrogen Peroxide, Linoleic Acids, Oxidation-Reduction, Phenols, Rapeseed Oil, Surface Properties, Ultraviolet Rays}, issn = {2041-1723}, doi = {10.1038/s41467-025-56802-0}, author = {Wang, Xinke and Fahy, William D and Xie, Linna and Peng, Hui and Abbatt, Jonathan P D} } @article {286, title = {Haloacetonitriles Induce Structure-Related Cellular Toxicity Through Distinct Proteome Thiol Reaction Mechanisms.}, journal = {ACS Environ Au}, volume = {5}, year = {2025}, month = {2025 Jan 15}, pages = {101-113}, abstract = {

Haloacetonitriles (HANs) are a class of toxic drinking water disinfection byproducts (DBPs). However, the toxicity mechanisms of HANs remain unclear. We herein investigated the structure-related in vitro toxicity of 6 representative HANs by utilizing complementary bioanalytical approaches. Dibromoacetonitrile (DBAN) displayed strong cytotoxicity and Nrf2 oxidative stress responses, followed by monohalogenated HANs (monoHANs) while other polyhalogenated HANs (polyHANs) exhibited little toxicity. Activity based protein profiling (ABPP) revealed that toxic HANs adduct to human proteome thiols, supporting thiol reactivity as the primary toxicity mechanism for HANs. By using glutathione (GSH) as a thiol surrogate, monoHANs reacted with GSH via S2 while polyHANs reacted through ultrafast addition reactions. In contrast, DBAN generated an unexpected fully debrominated product and glutathione disulfide (GSSG). The unique reaction of DBAN with GSH was found to be mediated by radicals which was supported by electron paramagnetic resonance (EPR) spectroscopy and by radical trapping reagent reaction quenching. Shotgun proteomics further revealed that monoHANs and DBAN adducted to proteome thiols in live cells forming dehalogenated adducts. Multiple antioxidant proteins, SOD1, CSTB, and GAPDH, were adducted by toxic HANs at specific cysteine residues. This study highlights the structurally selective toxicity of HANs in human cells, which are attributed to their distinct reactions with proteome thiols.

}, issn = {2694-2518}, doi = {10.1021/acsenvironau.4c00068}, author = {Yeung, Kirsten and Xie, Linna and Nair, Pranav and Peng, Hui} } @article {293, title = {A Rapid Testing Kit for 6PPD Screening in Rubber Products.}, journal = {Anal Chem}, year = {2025}, month = {2025 Apr 26}, abstract = {

-(1,3-dimethylbutyl)--phenyl--phenylenediamine (6PPD) has received increasing attention due to its ubiquitous environmental occurrence and extreme aquatic toxicity of its oxidation product 6PPD-quinone. Given 6PPD{\textquoteright}s application as an antioxidant in a wide array of rubber products, cost-effective detection of 6PPD is important for product and waste management. We herein developed a rapid testing kit for the detection (\<10 min) of 6PPD in rubber products with low costs (\<$1/sample), which was inspired by the observation of a red-colored product after 6PPD exposure to oxidants. The selectivity of this reaction was evaluated by 14 structurally diverse phenols and anilines. Interestingly, the protonated -1,3-dimethyl butyl--phenyl quinone diimine (6QDI+H), rather than its neutral or radical counterparts, appeared to be the red-colored product with λ = 490 nm. We further developed a "green" and user-friendly 6PPD rapid testing kit, which was further applied to a wide array of 50 rubber products. 6PPD was detected in 22 out of 50 samples, with a strong agreement ( = 0.896) observed between the results of the rapid testing kit and LC-MS. In summary, this study introduces a 6PPD rapid testing kit for users without requiring expertise in chemistry.

}, issn = {1520-6882}, doi = {10.1021/acs.analchem.5c00079}, author = {Li, Zhuoyuan and Xie, Linna and Nair, Pranav and Yeung, Kirsten and Meek, Oliver and Tao, Juan and Hiki, Kyoshiro and Hao, Chunyan and Peng, Hui} } @article {289, title = {Structure and Toxicity Characterization of Alkyl Hydroxylated Metabolites of 6PPD-Q.}, journal = {Environ Sci Technol}, year = {2025}, month = {2025 Apr 08}, abstract = {

Distinct from other nontoxic phenyl--phenylenediamine (PPD) quinones, -(1,3-dimethylbutyl)-{\textquoteright}-phenyl--phenylenediamine-quinone (6PPD-Q) was recently discovered to be regioselectively metabolized to alkyl hydroxylated metabolites (alkyl-OH-6PPD-Q) in rainbow trout. It remains unknown whether the unique alkyl-OH-6PPD-Q contributes to the toxicity of 6PPD-Q. To test this, we herein synthesized chemical standards of alkyl-OH-6PPD-Q isomers and investigated their metabolic formation mechanism and toxicity. The predominant alkyl-OH-6PPD-Q was confirmed to be hydroxylated on the C tertiary carbon (C-OH-6PPD-Q). The formation of C-OH-6PPD-Q was only observed in microsomal but not in cytosolic fractions of rainbow trout () liver S9. A general cytochrome P450 (CYP450) inhibitor fluoxetine inhibited the formation of hydroxylated metabolites of 6PPD-Q, supporting that CYP450 catalyzed the hydroxylation. This well-explained the compound- and regio-selective formation of C-OH-6PPD-Q, due to the weak C-H bond on the C tertiary carbon. Surprisingly, while cytotoxicity was observed for 6PPD-Q and C-OH-6PPD-Q in a coho salmon () embryo (CSE-119) cell line, no toxicity was observed for C-OH-6PPD-Q. To further confirm this under physiologically relevant conditions, we fractionated 6PPD-Q metabolites formed in the liver microsome of rainbow trout. Cytotoxicity was observed for the fraction of 6PPD-Q, but not the fraction of C-OH-6PPD-Q. In summary, this study highlighted the C tertiary carbon as the key moiety for both metabolism and toxicity of 6PPD-Q and confirmed that alkyl hydroxylation is a detoxification pathway for 6PPD-Q.

}, issn = {1520-5851}, doi = {10.1021/acs.est.4c11823}, author = {Nair, Pranav and Barrett, Holly and Tanoto, Kaylin and Xie, Linna and Sun, Jianxian and Yang, Diwen and Yao, Han and Song, Datong and Peng, Hui} } @article {290, title = {Synthesis and Toxicity Evaluation of -Phenylenediamine-Quinones.}, journal = {Environ Sci Technol}, year = {2025}, month = {2025 Apr 08}, abstract = {

-(1,3-Dimethylbutyl)--phenyl--phenylenediamine-quinone (6PPD-Q), the tire rubber-derived transformation product of 6PPD, was recently discovered to cause the acute mortality of coho salmon (). Aiming to identify potential replacement antiozonants for 6PPD that do not produce toxic quinones, seven PPD-quinones with distinct side chains were synthesized to investigate their structure-related toxicities using rainbow trout (). While 6PPD-Q exerted high toxicity (96 h LC = 0.35 μg/L), toxicity was not observed for six other PPD-quinones despite their similar structures. The fish tissue concentrations of 6PPD-Q after sublethal exposure (0.29 μg/L) were comparable to the other PPD-quinones, which indicated that bioaccumulation levels were not the reason for the selective toxicity of 6PPD-Q. Hydroxylated PPD-quinones were detected as the predominant metabolites in fish tissue. Interestingly, a single major aromatic hydroxylation metabolite was detected for the alternate PPD-quinones, but two abundant OH-6PPD-Q isomers were detected for 6PPD-Q. MS spectra confirmed that hydroxylation occurred on the alkyl side chain for one isomer. The structurally selective toxicity of 6PPD-Q was also observed in a coho salmon (CSE-119) cell line, which further supports its intrinsic toxicity. This study reported the selective toxicity of 6PPD-Q and pinpointed the possibility for other PPDs to be applied as potential substitutes of 6PPD.

}, issn = {1520-5851}, doi = {10.1021/acs.est.4c12220}, author = {Nair, Pranav and Sun, Jianxian and Xie, Linna and Kennedy, Lisa and Kozakiewicz, Derek and Kleywegt, Sonya M and Hao, Chunyan and Byun, Hannah and Barrett, Holly and Baker, Joshua and Monaghan, Joseph and Krogh, Erik T and Song, Datong and Peng, Hui} } @article {277, title = {Compound Class-Specific Temporal Trends (2021{\textendash}2023) of Tire Wear Compounds in Suspended Solids from Toronto Wastewater Treatment Plants}, journal = {ACS ES\&T Water}, year = {2024}, month = {11/2024}, author = {Xie, Linna and Yuan, Lai and Sun, Jianxian and Yang, Miqing and Khan, Ismail and Lopez, Joselyn and Gong, Yufeng and Nair, Pranav and Hao, Chunyan and Helm, Paul and Barrett, Holly and Edwards, Elizabeth and Peng, Hui} } @article {276, title = {Structurally Selective Ozonolysis of -Phenylenediamines and Toxicity in Coho Salmon and Rainbow Trout.}, journal = {Environ Sci Technol}, year = {2024}, month = {2024 Nov 23}, abstract = {

The tire-rubber-derived ozonation product of -(1,3-dimethylbutyl)-{\textquoteright}-phenyl--phenylenediamine (6PPD), -(1,3-dimethylbutyl)-{\textquoteright}-phenyl--phenylenediamine-quinone (6PPD-Q), was recently discovered to cause acute mortality in coho salmon (). -Phenylenediamines (PPDs) with variable side chains distinct from 6PPD have been identified as potential replacement antioxidants, but their toxicities remain unclear under environmentally relevant ozone conditions. We herein tested the multiphase gas-surface ozone reactivity of four select PPDs [6PPD, -isopropyl-{\textquoteright}-phenyl--phenylenediamine (IPPD), ,{\textquoteright}-diphenyl--phenylenediamine (DPPD), and -phenyl-{\textquoteright}-cyclohexyl--phenylenediamine (CPPD)] and evaluated the toxicity of their reaction mixtures in coho salmon, rainbow trout (), and fathead minnow (). 6PPD and IPPD were found to rapidly react with ozone, while no significant multiphase ozone reactivity was observed for DPPD or CPPD. The viability of coho salmon CSE-119 cells was strongly affected by the ozonolysis products of 6PPD but not by those of the other three PPDs. Acute mortality was only observed in juvenile rainbow trout that were exposed to oxidized 6PPD, suggesting a common mechanism of toxic action in the two salmonid fish species. This study reports the structurally selective ozone reactivity of PPDs and the unique toxicity of 6PPD ozonolysis mixtures, which demonstrates that other PPDs are potential alternative antioxidants.

}, issn = {1520-5851}, doi = {10.1021/acs.est.4c04817}, author = {Xie, Linna and Yu, Jie and Nair, Pranav and Sun, Jianxian and Barrett, Holly and Meek, Oliver and Qian, Xing and Yang, Diwen and Kennedy, Lisa and Kozakiewicz, Derek and Hao, Chunyan and Hansen, John D and Greer, Justin B and Abbatt, Jonathan P D and Peng, Hui} }