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Gaines LGT, Sinclair G, Williams AJ. A proposed approach to defining per- and polyfluoroalkyl substances (PFAS) based on molecular structure and formula. INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT 2023; 19:1333-1347. [PMID: 36628931 PMCID: PMC10827356 DOI: 10.1002/ieam.4735] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/06/2022] [Accepted: 01/02/2023] [Indexed: 06/17/2023]
Abstract
Various groups and researchers, including the authors of this work, have proposed different definitions of what constitutes per- and polyfluoroalkyl substances (PFAS). The different definitions are all based on a structural definition. Although a structural definition is reasonable, such an approach is difficult to execute if the intent is to narrow or refine the definition. This approach can also lead to inexplicable demarcations of what are and what are not PFAS. Our objective was to create a narrow, simple PFAS definition that allows interested groups to communicate with a common understanding and will also serve as a starting point to focus on substances that are of real environmental concern. Our studies have demonstrated that numerous highly fluorinated complex structures exist that make a structure-based definition difficult. We suggest that a definition based on fractional fluorination expressed as the percentage of fluorine of a molecular formula using atom counting offers advantages. Using a combination of a structure-based definition and a definition based on the fractional percentage of the molecular formula that is fluorine can provide a more inclusive and succinct definition. Thus, we propose a new definition based on four substructures along with any structures where the molecular formula is 30% fluorine by atom count. Integr Environ Assess Manag 2023;19:1333-1347. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).
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Affiliation(s)
- Linda G. T. Gaines
- Office of Superfund Remediation and Technology Innovation, Office of Land and Emergency Management, US Environmental Protection Agency, DC, Washington, USA
| | - Gabriel Sinclair
- ORAU Student Services Contractor to Center for Computational Toxicology and Exposure, Office of Research and Development, US Environmental Protection Agency, NC, Research Triangle Park, USA
| | - Antony J. Williams
- Office of Research & Development, Center for Computational Toxicology & Exposure, US Environmental Protection Agency, NC, Research Triangle Park, USA
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2
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Adeniyi AA, Adeniyi JN, Olumayede EG. The theoretical study of the oxidation reaction of hydroxyl radical for the removal of volatile organic aliphatic and aromatic aldehydes from the atmosphere. Struct Chem 2023. [DOI: 10.1007/s11224-022-02120-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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3
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Chattopadhyay A, Bedjanian Y, Romanias MN, Eleftheriou AD, Melissas VS, Papadimitriou VC, Burkholder JB. OH Radical and Chlorine Atom Kinetics of Substituted Aromatic Compounds: 4-chlorobenzotrifluoride ( p-ClC 6H 4CF 3). J Phys Chem A 2022; 126:5407-5419. [PMID: 35943137 DOI: 10.1021/acs.jpca.2c04455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanisms for the OH radical and Cl atom gas-phase reaction kinetics of substituted aromatic compounds remain a topic of atmospheric and combustion chemistry research. 4-Chlorobenzotrifluoride (p-chlorobenzotrifluoride, p-ClC6H4CF3, PCBTF) is a commonly used substituted aromatic volatile organic compound (VOC) in solvent-based coatings. As such, PCBTF is classified as a volatile chemical product (VCP) whose release into the atmosphere potentially impacts air quality. In this study, rate coefficients, k1, for the OH + PCBTF reaction were measured over the temperature ranges 275-340 and 385-940 K using low-pressure discharge flow-tube reactors coupled with a mass spectrometer detector in the ICARE/CNRS (Orléans, France) laboratory. k1(298-353 K) was also measured using a relative rate method in the thermally regulated atmospheric simulation chamber (THALAMOS; Douai, France). k1(T) displayed a non-Arrhenius temperature dependence with a negative temperature dependence between 275 and 385 K given by k1(275-385 K) = (1.50 ± 0.15) × 10-14 exp((705 ± 30)/T) cm3 molecule-1 s-1, where k1(298 K) = (1.63 ± 0.03) × 10-13 cm3 molecule-1 s-1 and a positive temperature dependence at elevated temperatures given by k1(470-950 K) = (5.42 ± 0.40) × 10-12 exp(-(2507 ± 45) /T) cm3 molecule-1 s-1. The present k1(298 K) results are in reasonable agreement with two previous 296 K (760 Torr, syn. air) relative rate measurements. The rate coefficient for the Cl-atom + PCBTF reaction, k2, was also measured in THALAMOS using a relative rate technique that yielded k2(298 K) = (7.8 ± 2) × 10-16 cm3 molecule-1 s-1. As part of this work, the UV and infrared absorption spectra of PCBTF were measured (NOAA; Boulder, CO, USA). On the basis of the UV absorption spectrum, the atmospheric instantaneous UV photolysis lifetime of PCBTF (ground level, midlatitude, Summer) was estimated to be 3-4 days, assuming a unit photolysis quantum yield. The non-Arrhenius behavior of the OH + PCBTF reaction over the temperature range 275 to 950 K is interpreted using a mechanism for the formation of an OH-PCBTF adduct and its thermochemical stability. The results from this study are included in a discussion of the OH radical and Cl atom kinetics of halogen substituted aromatic compounds for which only limited temperature-dependent kinetic data are available.
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Affiliation(s)
- Aparajeo Chattopadhyay
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305-3327, United States.,Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States
| | - Yuri Bedjanian
- Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), CNRS 45071 Orléans Cedex 2, France
| | - Manolis N Romanias
- Center for Energy and Environment, Institut Mines-Télécom Nord Europe, Université Lille, F-59000 Lille, France
| | - Angeliki D Eleftheriou
- Laboratory of Photochemistry and Chemical Kinetics, Department of Chemistry, University of Crete, Vassilika Vouton, 70013, Heraklion, Crete, Greece
| | | | - Vassileios C Papadimitriou
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305-3327, United States.,Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States.,Laboratory of Photochemistry and Chemical Kinetics, Department of Chemistry, University of Crete, Vassilika Vouton, 70013, Heraklion, Crete, Greece
| | - James B Burkholder
- Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305-3327, United States
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Cui Q, Peng J, Xu C, Lan Z. Automatic Approach to Explore the Multireaction Mechanism for Medium-Sized Bimolecular Reactions via Collision Dynamics Simulations and Transition State Searches. J Chem Theory Comput 2022; 18:910-924. [DOI: 10.1021/acs.jctc.1c00795] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Qinghai Cui
- Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety and MOE Key Laboratory of Environmental Theoretical Chemistry, SCNU Environmental Research Institute, School of Environment, South China Normal University, Guangzhou 510006, P. R. China
| | - Jiawei Peng
- Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety and MOE Key Laboratory of Environmental Theoretical Chemistry, SCNU Environmental Research Institute, School of Environment, South China Normal University, Guangzhou 510006, P. R. China
| | - Chao Xu
- Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety and MOE Key Laboratory of Environmental Theoretical Chemistry, SCNU Environmental Research Institute, School of Environment, South China Normal University, Guangzhou 510006, P. R. China
- Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; School of Chemistry, South China Normal University, Guangzhou 510006, P. R. China
| | - Zhenggang Lan
- Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety and MOE Key Laboratory of Environmental Theoretical Chemistry, SCNU Environmental Research Institute, School of Environment, South China Normal University, Guangzhou 510006, P. R. China
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Wu X, Hou Q, Huang J, Chai J, Zhang F. Exploring the OH-initiated reactions of styrene in the atmosphere and the role of van der Waals complex. CHEMOSPHERE 2021; 282:131004. [PMID: 34082313 DOI: 10.1016/j.chemosphere.2021.131004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/19/2021] [Accepted: 05/23/2021] [Indexed: 06/12/2023]
Abstract
Reacting with OH provides a major sink for styrene in the atmosphere, with three possible pathways including OH-addition, H-abstraction and addition-dissociation reactions. However, the total rate coefficients of styrene + OH were measured as 1.2-6.2 × 10-11 cm3 molecule-1 s-1 under atmospheric conditions, varying by a maximum factor of 5. On the other hand, only one theoretical work reported this rate coefficient as 19.1 × 10-11 cm3 molecule-1 s-1, which exhibits up to 16 times that measured in laboratory studies. In the present study, the reaction kinetics of styrene + OH was extensively studied with high-level quantum chemical methods combined with RRKM/master equation simulations. In particular, we carried out theoretical treatments for the formation of pre-reaction Van der Waals complexes of styrene + OH, and examined their influence on the reaction kinetics. The total rate coefficient for styrene + OH is calculated to be 1.7 × 10-11 cm3 molecule-1 s-1 at 300 K, 1 atm. The main products are addβ (88.2%), add5 (6.9%), addα (1.9%) and add3 (1.7%). Using our computed rate coefficient and the global atmospheric hydroxyl radical concentration (2 × 106 radicals per cm3), the lifetime of styrene in the atmosphere is estimated at 8.0 h. The degradation of styrene might be negligible for the formation of ozone in the atmosphere based upon the photochemical ozone creation potentials calculation. The computed product yields indicate that addβ via subsequent reactions could significantly produce formaldehyde and benzaldehyde that were observed in previous experimental studies on styrene oxidation, and contribute to the formation of secondary organic aerosols.
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Affiliation(s)
- Xiaoqing Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China; National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, PR China
| | - Qifeng Hou
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China
| | - Jiabin Huang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China
| | - Jiajue Chai
- Institute at Brown for Environment and Society, And Department of Earth, Environmental and Planetary Sciences, Brown University, 182 Hope St., Providence, RI, 02912, USA
| | - Feng Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, PR China.
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Xing L, Meng Q, Zhang L. A thorough theoretical mechanistic study of OH-initiated oxidative degradation mechanism for large polycyclic aromatic hydrocarbons. COMPUT THEOR CHEM 2020. [DOI: 10.1016/j.comptc.2020.112730] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ma F, Ding Z, Elm J, Xie HB, Yu Q, Liu C, Li C, Fu Z, Zhang L, Chen J. Atmospheric Oxidation of Piperazine Initiated by ·Cl: Unexpected High Nitrosamine Yield. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:9801-9809. [PMID: 30063348 DOI: 10.1021/acs.est.8b02510] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Chlorine radicals (·Cl) initiated amine oxidation plays an important role for the formation of carcinogenic nitrosamine in the atmosphere. Piperazine (PZ) is considered as a potential atmospheric pollutant since it is an alternative solvent to monoethanolamine (MEA), a benchmark solvent in a leading CO2 capture technology. Here, we employed quantum chemical methods and kinetics modeling to investigate ·Cl-initiated atmospheric oxidation of PZ, particularly concerning the potential of PZ to form nitrosamine compared to MEA. Results showed that the ·Cl-initiated PZ reaction exclusively leads to N-center radicals (PZ-N) that mainly react with NO to produce nitrosamine in their further reaction with O2/NO. Together with the PZ + ·OH reaction, the PZ-N yield from PZ oxidation is still lower than that of the corresponding MEA reactions. However, the nitrosamine yield of PZ is higher than the reported value for MEA when [NO] is <5 ppb, a concentration commonly encountered in a polluted urban atmosphere. The unexpected high nitrosamine yield from PZ compared to MEA results from a more favorable reaction of N-center radicals with NO compared to O2. These findings show that the yield of N-center radicals cannot directly be used as a metric for the yield of the corresponding carcinogenic nitrosamine.
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Affiliation(s)
- Fangfang Ma
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Zhezheng Ding
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Jonas Elm
- Department of Chemistry and Climate , Aarhus University , Aarhus 8000 , Denmark
| | - Hong-Bin Xie
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Qi Yu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Cong Liu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Chao Li
- State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment , Northeast Normal University , Changchun 130117 , China
| | - Zhiqiang Fu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Lili Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
| | - Jingwen Chen
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology , Dalian University of Technology , Dalian 116024 , China
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Card ML, Gomez-Alvarez V, Lee WH, Lynch DG, Orentas NS, Lee MT, Wong EM, Boethling RS. History of EPI Suite™ and future perspectives on chemical property estimation in US Toxic Substances Control Act new chemical risk assessments. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:203-212. [PMID: 28275775 DOI: 10.1039/c7em00064b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Chemical property estimation is a key component in many industrial, academic, and regulatory activities, including in the risk assessment associated with the approximately 1000 new chemical pre-manufacture notices the United States Environmental Protection Agency (US EPA) receives annually. The US EPA evaluates fate, exposure and toxicity under the 1976 Toxic Substances Control Act (amended by the 2016 Frank R. Lautenberg Chemical Safety for the 21st Century Act), which does not require test data with new chemical applications. Though the submission of data is not required, the US EPA has, over the past 40 years, occasionally received chemical-specific data with pre-manufacture notices. The US EPA has been actively using this and publicly available data to develop and refine predictive computerized models, most of which are housed in EPI Suite™, to estimate chemical properties used in the risk assessment of new chemicals. The US EPA develops and uses models based on (quantitative) structure-activity relationships ([Q]SARs) to estimate critical parameters. As in any evolving field, (Q)SARs have experienced successes, suffered failures, and responded to emerging trends. Correlations of a chemical structure with its properties or biological activity were first demonstrated in the late 19th century and today have been encapsulated in a myriad of quantitative and qualitative SARs. The development and proliferation of the personal computer in the late 20th century gave rise to a quickly increasing number of property estimation models, and continually improved computing power and connectivity among researchers via the internet are enabling the development of increasingly complex models.
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Affiliation(s)
- Marcella L Card
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
| | - Vicente Gomez-Alvarez
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
| | - Wen-Hsiung Lee
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
| | - David G Lynch
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
| | - Nerija S Orentas
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
| | - Mari Titcombe Lee
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
| | - Edmund M Wong
- United States Environmental Protection Agency Office of Pollution Prevention and Toxics, Washington, DC 20004, USA.
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Tratnyek PG, Bylaska EJ, Weber EJ. In silico environmental chemical science: properties and processes from statistical and computational modelling. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:188-202. [PMID: 28262894 DOI: 10.1039/c7em00053g] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Quantitative structure-activity relationships (QSARs) have long been used in the environmental sciences. More recently, molecular modeling and chemoinformatic methods have become widespread. These methods have the potential to expand and accelerate advances in environmental chemistry because they complement observational and experimental data with "in silico" results and analysis. The opportunities and challenges that arise at the intersection between statistical and theoretical in silico methods are most apparent in the context of properties that determine the environmental fate and effects of chemical contaminants (degradation rate constants, partition coefficients, toxicities, etc.). The main example of this is the calibration of QSARs using descriptor variable data calculated from molecular modeling, which can make QSARs more useful for predicting property data that are unavailable, but also can make them more powerful tools for diagnosis of fate determining pathways and mechanisms. Emerging opportunities for "in silico environmental chemical science" are to move beyond the calculation of specific chemical properties using statistical models and toward more fully in silico models, prediction of transformation pathways and products, incorporation of environmental factors into model predictions, integration of databases and predictive models into more comprehensive and efficient tools for exposure assessment, and extending the applicability of all the above from chemicals to biologicals and materials.
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Affiliation(s)
- Paul G Tratnyek
- Institute of Environmental Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
| | - Eric J Bylaska
- William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA
| | - Eric J Weber
- National Exposure Assessment Laboratory, U.S. Environmental Protection Agency, 960 College Station Road, Athens, GA 30605, USA
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