Comprehensive Emerging Chemical Discovery: Novel Polyfluorinated Compounds in Lake Michigan Trout

A versatile screening algorithm capable of efficiently searching liquid chromatographic/mass spectrometric data for unknown compounds has been developed using a combination of open source and generic computing software packages. The script was used to search for select novel polyfluorinated contaminants in Great Lakes fish. However, the framework is applicable whenever full-scan, high-resolution mass spectral and chromatographic data are collected. Target compound classes are defined and a matrix of candidates is generated that includes mass spectral profiles and likely fragmentation pathways. The initial calibration was performed using a standard solution of known linear perfluoroalkyl acids. Once validated, Lake Michigan trout data files were analyzed for polyfluoroalkyl acids using the algorithm referencing 3570 possible compounds including C₄–C₁₀ perfluoro- and polyfluoroalkyl, polyfluorochloroalkyl acids and sulfonates, and potential ether forms. The results suggest the presence of 30 polyfluorinated chemical formulas which have not been previously reported in the literature. The identified candidates included mono- to hexafluoroalkyl carboxylic acids, mono- and trifluoroalkyl carboxylic acid ethers, and novel polyfluoroalkyl sulfonates. Candidate species identified in lake trout were qualified using theoretical isotopic profile matching, characteristic fragmentation patterns based on known linear perfluoroalkyl acid (PFAA) fragmentation, and retention time reproducibility among replicate extractions and injections. In addition, the relative retention times of multiple species within a compound class were compared based on theoretical octanol–water partition coefficients

Suspect Screening and Nontargeted Analysis of Per- and Polyfluoroalkyl Substances in a Lake Ontario Food Web

Per- and polyfluoroalkyl substances (PFAS) are globally distributed in the natural environment, and their persistent and bioaccumulative potential illicit public concern. The production of certain PFAS has been halted or controlled by regulation due to their adverse effect on the health of humans and wildlife. However, new PFAS are continuously developed as alternatives to legacy PFAS. Additionally, many precursors are unknown, and their metabolites have not been assessed. To better understand the PFAS profiles in the Lake Ontario (LO) aquatic food web, a quadrupole time-of-flight mass spectrometer (QToF) coupled to ultrahigh-performance liquid chromatography (UPLC) was used to generate high-resolution mass spectra (HRMS) from sample extracts. The HRMS data files were analyzed using an isotopic profile deconvoluted chromatogram (IPDC) algorithm to isolate PFAS profiles in aquatic organisms. Fourteen legacy PFAAs (C5–C14) and 15 known precursors were detected in the LO food web. In addition, over 400 unknown PFAS features that appear to biomagnify in the LO food web were found. Profundal benthic organisms, deepwater sculpin(Myoxocephalus thompsonii), and Mysis were found to have more known precursors than other species in the food web, suggesting that there is a large reservoir of fluorinated substances in the benthic zone

Bioaccumulation and Spatiotemporal Trends of Polyhalogenated Carbazoles in Great Lakes Fish from 2004 to 2016

Polyhalogenated carbazoles (PHCZs) were recently discovered in Great Lakes sediment and other aquatic systems. However, knowledge about their bioaccumulation and potential risks to fish and wildlife remains very limited. The present study investigated PHCZs in Great Lakes lake trout (<i>Salvelinus namaycush</i>) and walleye (<i>Sander vitreus</i>; Lake Erie only) composites collected between 2004 and 2016. Median concentrations of ∑PHCZs by lake ranged from 54.7 to 154 ng/g lipid weight or lw (6.8–28.0 ng/g wet weight). Dominant congeners included 3,6-dichlorocarbazole, 1,3,6-tribromocarbazole, and 1,3,6,8-tetrachlorocarbazole. The highest ∑PHCZs concentrations were found in Lakes Michigan and Ontario fish, followed by Lake Huron, whereas Lakes Erie and Superior fish contained the lowest concentrations. Congener profiles of PHCZs also exhibited spatial variations. After age normalization to minimize fish age influence on bioaccumulation rates, fish ∑PHCZs’ concentrations declined significantly over time in all lakes except Lake Erie, with slopes ranging from −10.24% to −3.85% per year. The median toxic equivalent (TEQ) of PHCZs due to their dioxin-like activity was determined to range from 8.7 to 25.7 pg/g lw in Great Lakes fish. This study provides the first insight into the bioaccumulation and spatiotemporal trends of PHCZs in Great Lakes and suggests the need for further research on this group of chemicals

Polybrominated Diphenyl Ethers (PBDEs): Turning the Corner in Great Lakes Trout 1980–2009

Lake trout and walleye composites were collected between 2004 and 2009 as part of the Great Lakes Fish Monitoring and Surveillance Program (GLFMSP) and analyzed for polybrominated diphenyl ethers (PBDEs). Yearly mean total PBDE concentrations (sum of congeners BDE-47, BDE-99, BDE-100, BDE-153, BDE-154) ranged from 44–192, 28–113, 50–107, 37–111, and 11–22 ng/g wet wt. for Lakes Michigan, Huron, Ontario, and Superior lake trout, and Lake Erie walleye, respectively. A 1980–2009 temporal record of PBDE concentrations in the Great Lakes’ top predator fish (lake trout and walleye) was assembled by integrating previous GLFMSP data (1980–2003) with current results (2004–2009). Temporal profiles show obvious breakpoints between periods of PBDE accumulation and decline in trout for Lakes Huron, Michigan and Ontario with a significant (<i>p</i> < 0.0001 and <i>r</i> = 0.55, 0.72, and 0.51, respectively) decrease in concentration after 2000–2001. A similar transition was observed in Lake Superior for the nearshore site accompanied by a less significant decreasing trend (<i>p</i> = 0.016, <i>r</i> = 0.33), suggesting concentrations are declining very slowly or have leveled off. In contrast, Lake Erie walleye concentrations began leveling off in the late 1990s and no statistically significant trend (increasing or decreasing) has been observed in recent years. A decrease in the BDE-47/BDE-153 ratio was also recently observed, suggesting a transition to more highly brominated PBDEs is occurring in Great Lakes trout. This study provides region-wide evidence that PBDE concentrations are generally declining in Great Lakes trout, although there are clear exceptions to this trend. Results from this study reflect the positive impact of the 2004 PentaBDE ban on macro-scale aquatic freshwater ecosystems

Age-Corrected Trends and Toxic Equivalence of PCDD/F and CP-PCBs in Lake Trout and Walleye from the Great Lakes: 2004–2014

Our research reports polychlorinated dibenzo-<i>p</i>-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CP-PCBs) concentrations and age-corrected trends for lake trout and walleye in the Great Lakes over the 2004–2014 period. We determined that age–contaminant corrections are required to accurately report contaminant trends due to significant lake trout age structure changes. The age-trend model (ATM) described here uses a lake-specific age–contaminant regression to mitigate the effect of a fluctuating lake trout age structure to directly improve the log–linear regression model. ATM results indicate that half-life (<i>t</i>_1/2) and percent decreases for PCDD/Fs, CP-PCBs, and toxic equivalence (TEQ) (average −56 to 70%) were fairly uniform and consistent across the Great Lakes over the 2004–2014 period. The vast majority of TEQ associated with all Great Lakes lake trout and walleye samples is due to the nonortho CP-PCBs (average = 79%) as compared with PCDD/Fs (average = 21%). On average, CP-PCB_126 individually accounted for over 95% of the total CP-PCB TEQ. A retrospective analysis (1977–2014) of 2378-TCDF and 2378-TCDD raw concentrations in Lake Ontario lake trout revealed decreases of 94% and 96%, respectively. Tissue residue guidelines for wildlife protection based on lake trout and walleye total TEQ were uniformly exceeded in all the Great Lakes