Abstract
Environmentally persistent free radicals are long-lived pollutants that maintain stability in air, soil, and water. They contribute to the production of reactive oxygen species in environmental media, leading to oxidative stress in biological organisms. This stress can provoke inflammation and damage to biological macromolecules, potentially resulting in cardiopulmonary dysfunction. In this review, we discuss the formation and classification of EPFRs. Typically, EPFRs form through electron transfer from organic compounds to transition metals during thermal processes. In metal-free environments, however, organic compounds can undergo bond cleavage, generating EPFRs under thermal conditions and light exposure. EPFRs are generally categorized into three types: oxygen-centered, carbon-centered, and those containing heteroatoms centered on either oxygen or carbon. We also provide a detailed summary of the fundamental characteristics of EPFRs in different environments such as air, soil, and water. Given their role as electron donors, EPFRs have potential applications in degrading organic pollutants in the environment. The review comprehensively addresses the deleterious impacts of EPFRs on organism health, highlighting risks to metabolic functions and cardiopulmonary health. Furthermore, it underscores the potential involvement of EPFRs as electron donors in atmospheric chemical reactions. The pivotal role of EPFRs in environmental pollutant transformation warrants more studies in future research endeavors.
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Abbreviations
- EPFRs:
-
Environmentally persistent free radicals
- PM2.5 :
-
Particulate matter with aerodynamic diameter less than 2.5 µm
- ge :
-
The g-factor for electrons
References
Bährle C, Custodis V, Jeschke G, van Bokhoven JA, Vogel F (2014) In situ observation of radicals and molecular products during lignin pyrolysis. Chemsuschem 7:2022–2029. https://doi.org/10.1002/cssc.201400079
Balakrishna S, Lomnicki S, McAvey KM, Cole RB, Dellinger B, Cormier SA (2009) Environmentally persistent free radicals amplify ultrafine particle mediated cellular oxidative stress and cytotoxicity. Part Fibre Toxicol 6:11. https://doi.org/10.1186/1743-8977-6-11
Balakrishna S, Saravia J, Thevenot P, Ahlert T, Lominiki S, Dellinger B, Cormier SA (2011) Environmentally persistent free radicals induce airway hyperresponsiveness in neonatal rat lungs. Part Fibre Toxicol 8:11. https://doi.org/10.1186/1743-8977-8-11
Bi D, Huang F, Jiang M, He Z, Lin X (2022) Effect of pyrolysis conditions on environmentally persistent free radicals (EPFRs) in biochar from co-pyrolysis of urea and cellulose. Sci Total Environ 805:150339. https://doi.org/10.1016/j.scitotenv.2021.150339
Borrowman CK, Zhou SM, Burrow TE, Abbatt JPD (2016) Formation of environmentally persistent free radicals from the heterogeneous reaction of ozone and polycyclic aromatic compounds. Phys Chem Chem Phys 18:205–212. https://doi.org/10.1039/c5cp05606c
Burn BR, Varner KJ (2015) Environmentally persistent free radicals compromise left ventricular function during ischemia/reperfusion injury. Am J Physiol Heart Circ Physiol 308:H998–H1006. https://doi.org/10.1152/ajpheart.00891.2014
Chen Q, Sun H, Wang M, Wang Y, Zhang L, Han Y (2019a) Environmentally persistent free radical (EPFR) formation by visible-light illumination of the organic matter in atmospheric particles. Environ Sci Technol 53:10053–10061. https://doi.org/10.1021/acs.est.9b02327
Chen QC, Sun HY, Wang J, Shan M, Yang XD, Deng MS, Wang YQ, Zhang LX (2019b) Long-life type—the dominant fraction of EPFRs in combustion sources and ambient fine particles in Xi’an. Atmos Environ 219:117059. https://doi.org/10.1016/j.atmosenv.2019.117059
Chen QC, Sun HY, Song WH, Cao F, Tian CG, Zhang YL (2020) Size-resolved exposure risk of persistent free radicals (PFRs) in atmospheric aerosols and their potential sources. Atmos Chem Phys 20:14407–14417. https://doi.org/10.5194/acp-20-14407-2020
Cheng PF, Zhao XQ, El-Ramady H, Elsakhawy T, Waigi MG, Ling WT (2022) Formation of environmentally persistent free radicals from photodegradation of triclosan by metal oxides/silica suspensions and particles. Chemosphere 290:133322. https://doi.org/10.1016/j.chemosphere.2021.133322
Chuang GC, Xia HJ, Mahne SE, Varner KJ (2017) Environmentally persistent free radicals cause apoptosis in HL-1 cardiomyocytes. Cardiovasc Toxicol 17:140–149. https://doi.org/10.1007/s12012-016-9367-x
Church DF, Pryor WA (1985) Free-radical chemistry of cigarette-smoke and its toxicological implications. Environ Health Perspect 64:111–126. https://doi.org/10.2307/3430003
Cormier SA, Lomnicki S, Backes W, Dellinger B (2006) Origin and health impacts of emissions of toxic by-products and fine particles from combustion and thermal treatment of hazardous wastes and materials. Environ Health Perspect 114:810–817. https://doi.org/10.1289/ehp.8629
Cruz ALNd, Cook RL, Lomnicki SM, Dellinger B (2012) Effect of low temperature thermal treatment on soils contaminated with pentachlorophenol and environmentally persistent free radicals. Environ Sci Technol 46:5971–5978. https://doi.org/10.1021/es300362k
dela Cruz ALN, Gehling W, Lomnicki S, Cook R, Dellinger B (2011) Detection of environmentally persistent free radicals at a superfund wood treating site. Environ Sci Technol 45:6356–6365. https://doi.org/10.1021/es2012947
Dellinger B, Pryor WA, Cueto R, Squadrito GL, Hegde V, Deutsch WA (2001) Role of free radicals in the toxicity of airborne fine particulate matter. Chem Res Toxicol 14:1371–1377. https://doi.org/10.1021/tx010050x
Dellinger B, Lomnicki S, Khachatryan L, Maskos Z, Hall RW, Adounkpe J, McFerrin C, Truong H (2007) Formation and stabilization of persistent free radicals. Proc Combust Inst 31:521–528. https://doi.org/10.1016/j.proci.2006.07.172
Dugas TR, Lomnicki S, Cormier SA, Dellinger B, Reams M (2016) Addressing emerging risks: scientific and regulatory challenges associated with environmentally persistent free radicals. Int J Environ Res Public Health 13:573. https://doi.org/10.3390/ijerph13060573
Fang G, Gao J, Liu C, Dionysiou DD, Wang Y, Zhou D (2014) Key role of persistent free radicals in hydrogen peroxide activation by biochar: implications to organic contaminant degradation. Environ Sci Technol 48:1902–1910. https://doi.org/10.1021/es4048126
Fang G, Liu C, Gao J, Dionysiou DD, Zhou D (2015) Manipulation of persistent free radicals in biochar to activate persulfate for contaminant degradation. Environ Sci Technol 49:5645–5653. https://doi.org/10.1021/es5061512
Feld-Cook EE, Bovenkamp-Langlois L, Lomnicki SM (2017) Effect of particulate matter mineral composition on environmentally persistent free radical (EPFR) formation. Environ Sci Technol 51:10396–10402. https://doi.org/10.1021/acs.est.7b01521
Feng W, Zhang Y, Huang L, Li Y, Guo Q, Peng H, Shi L (2022) Spatial distribution, pollution characterization, and risk assessment of environmentally persistent free radicals in urban road dust from central China. Environ Pollut 298:118861. https://doi.org/10.1016/j.envpol.2022.118861
Gao P, Yao D, Qian Y, Zhong S, Zhang L, Xue G, Jia H (2018) Factors controlling the formation of persistent free radicals in hydrochar during hydrothermal conversion of rice straw. Environ Chem Lett 16:1463–1468. https://doi.org/10.1007/s10311-018-0757-0
Gehling W, Dellinger B (2013) Environmentally persistent free radicals and their lifetimes in PM2.5. Environ Sci Technol 47:8172–8178. https://doi.org/10.1021/es401767m
Gehling W, Khachatryan L, Dellinger B (2014) Hydroxyl radical generation from environmentally persistent free radicals (EPFRs) in PM2.5. Environ Sci Technol 48:4266–4272. https://doi.org/10.1021/es401770y
Guan X, Truong L, Lomnicki SM, Tanguay RL, Cormier SA (2021) Developmental hazard of environmentally persistent free radicals and protective effect of TEMPOL in zebrafish model. Toxics 9:12. https://doi.org/10.3390/toxics9010012
Guo XW, Zhang N, Hu X, Huang Y, Ding ZH, Chen YJ, Lian HZ (2020) Characteristics and potential inhalation exposure risks of PM2.5-bound environmental persistent free radicals in Nanjing, a mega-city in China. Atmos Environ 224:117355. https://doi.org/10.1016/j.atmosenv.2020.117355
Guo H, Wang Y, Yao K, Zheng H, Zhang X, Li R, Wang N, Fu H (2023) The overlooked formation of environmentally persistent free radicals on particulate matter collected from biomass burning under light irradiation. Environ Int 171:107668. https://doi.org/10.1016/j.envint.2022.107668
Harmon AC, Hebert VY, Cormier SA, Subramanian B, Reed JR, Backes WL, Dugas TR (2018) Particulate matter containing environmentally persistent free radicals induces AhR-dependent cytokine and reactive oxygen species production in human bronchial epithelial cells. PLoS ONE 13:e0205412. https://doi.org/10.1371/journal.pone.0205412
Harmon AC, Noel A, Subramanian B, Perveen Z, Jennings MH, Chen YF, Penn AL, Legendre K, Paulsen DB, Varner KJ, Dugas TR (2021) Inhalation of particulate matter containing free radicals leads to decreased vascular responsiveness associated with an altered pulmonary function. Am J Physiol Heart Circ Physiol 321:H667–H683. https://doi.org/10.1152/ajpheart.00725.2020
He FF, Lu JJ, Li ZY, Li M, Liu ZL, Tong YB (2022) Characteristics of environmentally persistent free radicals in PM2.5 and the influence of air pollutants in Shihezi, Northwestern China. Toxics 10:341. https://doi.org/10.3390/toxics10070341
Hong QF, Liu C, Wang ZB, Li RY, Liang XL, Wang YP, Zhang YT, Song ZL, Xiao ZH, Cui TY, Heng BB, Xu BB, Qi F, Ikhlaq A (2021) Electron transfer enhancing Fe(II)/Fe(III) cycle by sulfur and biochar in magnetic FeS@biochar to active peroxymonosulfate for 2,4-dichlorophenoxyacetic acid degradation. Chem Eng J (lausanne) 417:129238. https://doi.org/10.1016/j.cej.2021.129238
Hwang B, Fang T, Pham R, Wei JL, Gronstal S, Lopez B, Frederickson C, Galeazzo T, Wang XL, Jung H, Shiraiwa M (2021) Environmentally persistent free radicals, reactive oxygen species generation, and oxidative potential of highway PM2.5. ACS Earth Space Chem 5:1865–1875. https://doi.org/10.1021/acsearthspacechem.1c00135
Jaligama S, Saravia J, You DH, Yadav N, Lee GI, Shrestha B, Cormier SA (2017) Regulatory T cells and IL10 suppress pulmonary host defense during early-life exposure to radical containing combustion derived ultrafine particulate matter. Respir Res 18:15. https://doi.org/10.1186/s12931-016-0487-4
Jia HZ, Zhao S, Nulaji G, Tao KL, Wang F, Sharma VK, Wang CY (2017) Environmentally persistent free radicals in soils of past coking sites: distribution and stabilization. Environ Sci Technol 51:6000–6008. https://doi.org/10.1021/acs.est.7b00599
Jia HZ, Zhao S, Shi YF, Fan XY, Wang TC (2019) Formation of environmentally persistent free radicals during the transformation of anthracene in different soils: roles of soil characteristics and ambient conditions. J Hazard Mater 362:214–223. https://doi.org/10.1016/j.jhazmat.2018.08.056
Jia H, Li S, Wu L, Li S, Sharma VK, Yan B (2020a) Cytotoxic free radicals on air-borne soot particles generated by burning wood or low-maturity coals. Environ Sci Technol 54:5608–5618. https://doi.org/10.1021/acs.est.9b06395
Jia H, Liu J, Zhu K, Gao P, Lichtfouse E (2020b) High contribution of hydrocarbon transformation during the removal of polycyclic aromatic hydrocarbons from soils, humin and clay by thermal treatment at 100–200 °C. Environ Chem Lett 18(3):923–930. https://doi.org/10.1007/s10311-020-00972-4
Jia S-M, Wang D-Q, Liu L-Y, Zhang Z-F, Ma W-L (2022) Size-resolved environmentally persistent free radicals in cold region atmosphere: implications for inhalation exposure risk. J Hazard Mater 443:130263. https://doi.org/10.1016/j.jhazmat.2022.130263
Khachatryan L, Adounkpe J, Maskos Z, Dellinger B (2006) Formation of cyclopentadienyl radical from the gas-phase pyrolysis of hydroquinone, catechol, and phenol. Environ Sci Technol 40:5071–5076. https://doi.org/10.1021/es051878z
Khachatryan L, Vejerano E, Lomnicki S, Dellinger B (2011) Environmentally persistent free radicals (EPFRs). 1. Generation of reactive oxygen species in aqueous solutions. Environ Sci Technol 45:8559–8566. https://doi.org/10.1021/es201309c
Khachatryan L, Barekati-Goudarzi M, Asatryan R, Ozarowski A, Boldor D, Lomnicki SM, Cormier SA (2022) Metal-free biomass-derived environmentally persistent free radicals (Bio-EPFRs) from lignin pyrolysis. ACS Omega 7:30241–30249. https://doi.org/10.1021/acsomega.2c03381
Kiruri LW, Dellinger B, Lomnicki S (2013) Tar balls from deep water horizon oil spill: environmentally persistent free radicals (EPFR) formation during crude weathering. Environ Sci Technol 47:4220–4226. https://doi.org/10.1021/es305157w
Kiruri LW, Khachatryan L, Dellinger B, Lomnicki S (2014) Effect of copper oxide concentration on the formation and persistency of environmentally persistent free radicals (EPFRs) in particulates. Environ Sci Technol 48:2212–2217. https://doi.org/10.1021/es404013g
Kumar A, Patel VS, Harding JN, You DH, Cormier SA (2021) Exposure to combustion derived particulate matter exacerbates influenza infection in neonatal mice by inhibiting IL22 production. Part Fibre Toxicol 18:43. https://doi.org/10.1186/s12989-021-00438-7
Lancaster G (1967) Electron paramagnetic resonance (a review). J Mater Sci 2:489–495. https://doi.org/10.1007/bf00562955
Lee GI, Saravia J, You DH, Shrestha B, Jaligama S, Hebert VY, Dugas TR, Cormier SA (2014) Exposure to combustion generated environmentally persistent free radicals enhances severity of influenza virus infection. Part Fibre Toxicol 11:57. https://doi.org/10.1186/s12989-014-0057-1
Li H, Zhao Z, Luo X-S, Fang G, Zhang D, Pang Y, Huang W, Mehmood T, Tang M (2022a) Insight into urban PM2.5 chemical composition and environmentally persistent free radicals attributed human lung epithelial cytotoxicity. Ecotoxicol Environ Saf 234:113356. https://doi.org/10.1016/j.ecoenv.2022.113356
Li XT, Zhao HX, Qu BC, Tian Y (2022b) Photoformation of environmentally persistent free radicals on particulate organic matter in aqueous solution: role of anthracene and formation mechanism. Chemosphere 291:132815. https://doi.org/10.1016/j.chemosphere.2021.132815
Li ZS, Zhao HX, Li XT, Bekele TG (2022c) Characteristics and sources of environmentally persistent free radicals in PM2.5 in Dalian, Northeast China: correlation with polycyclic aromatic hydrocarbons. Environ Sci Pollut Res 29:24612–24622. https://doi.org/10.1007/s11356-021-17688-9
Li H, Chen Q, Wang C, Wang R, Sha T, Yang X, Ainur D (2023) Pollution characteristics of environmental persistent free radicals (EPFRs) and their contribution to oxidation potential in road dust in a large city in northwest China. J Hazard Mater 442:130087. https://doi.org/10.1016/j.jhazmat.2022.130087
Liao S, Pan B, Li H, Zhang D, Xing B (2014) Detecting free radicals in biochars and determining their ability to inhibit the germination and growth of corn, wheat and rice seedlings. Environ Sci Technol 48:8581–8587. https://doi.org/10.1021/es404250a
Lieke T, Zhang XC, Steinberg CEW, Pan B (2018) Overlooked risks of biochars: persistent free radicals trigger neurotoxicity in caenorhabditis elegans. Environ Sci Technol 52:7981–7987. https://doi.org/10.1021/acs.est.8b01338
Lim J, Yu LE, Kostetski YY, Lim C, Ryu J, Kim J (2008) Effects of driving conditions on diesel exhaust particulates. J Air Waste Manag Assoc 58:1077–1085. https://doi.org/10.3155/1047-3289.58.8.1077
Liu J, Jia H, Zhu K, Zhao S, Lichtfouse E (2020) Formation of environmentally persistent free radicals and reactive oxygen species during the thermal treatment of soils contaminated by polycyclic aromatic hydrocarbons. Environ Chem Lett 18:1329–1336. https://doi.org/10.1007/s10311-020-00991-1
Liu J, Gao N, Wen X, Jia H, Lichtfouse E (2021a) Plant and algal toxicity of persistent free radicals and reactive oxygen species generated by heating anthracene-contaminated soils from 100 to 600 °C. Environ Chem Lett 19:2695–2703. https://doi.org/10.1007/s10311-021-01193-z
Liu JL, Dong GH, Jing J, Zhang SY, Huang Y, Ho K (2021b) Photocatalytic reactive oxygen species generation activity of TiO2 improved by the modification of persistent free radicals. Environ Sci Nano 8:3846–3854. https://doi.org/10.1039/d1en00832c
Liu XY, Yang LL, Liu GR, Zheng MH (2021c) Formation of environmentally persistent free radicals during thermochemical processes and their correlations with unintentional persistent organic pollutants. Environ Sci Technol 55:6529–6541. https://doi.org/10.1021/acs.est.0c08762
Liu XM, Chai BS, Wang XY, Wu Z, Zou H, Liu YY, Zheng SJ, Qian GR, Ma ZL, Lu J (2022a) Environmentally persistent free radical promotes lung cancer progression by regulating the expression profile of miRNAs. Cancer Biother Radiopharm. https://doi.org/10.1089/cbr.2021.0378
Liu Z, Sun Y, Wang J, Li J, Jia H (2022b) In vitro assessment reveals the effects of environmentally persistent free radicals on the toxicity of photoaged tire wear particles. Environ Sci Technol 56:1664–1674. https://doi.org/10.1021/acs.est.1c05092
Liu S, Huang W, Yang J, Xiong Y, Huang Z, Wang J, Cai T, Dang Z, Yang C (2023) Formation of environmentally persistent free radicals on microplastics under UV irradiations. J Hazard Mater 453:131277. https://doi.org/10.1016/j.jhazmat.2023.131277
Lo Piccolo E, Becagli M, Lauria G, Cantini V, Ceccanti C, Cardelli R, Massai R, Remorini D, Guidi L, Landi M (2022) Biochar as a soil amendment in the tree establishment phase: what are the consequences for tree physiology, soil quality and carbon sequestration? Sci Total Environ 844:157175. https://doi.org/10.1016/j.scitotenv.2022.157175
Lomnicki S, Truong H, Vejerano E, Dellinger B (2008) Copper oxide-based model of persistent free radical formation on combustion-derived particulate matter. Environ Sci Technol 42:4982–4988. https://doi.org/10.1021/es071708h
Lord K, Moll D, Lindsey JK, Mahne S, Raman G, Dugas T, Cormier S, Troxlair D, Lomnicki S, Dellinger B, Varner K (2011) Environmentally persistent free radicals decrease cardiac function before and after ischemia/reperfusion injury in vivo. J Recept Signal Transduction 31:157–167. https://doi.org/10.3109/10799893.2011.555767
Lyons MJ, Gibson JF, Ingram DJE (1958) Free-radicals produced in cigarette smoke. Nature 181:1003–1004. https://doi.org/10.1038/1811003a0
Maskos Z, Dellinger B (2008a) Formation of the secondary radicals from the aging of tobacco smoke. Energy Fuels 22:382–388. https://doi.org/10.1021/ef700446v
Maskos Z, Dellinger B (2008b) Radicals from the oxidative pyrolysis of tobacco. Energy Fuels 22:1675–1679. https://doi.org/10.1021/ef7006694
Min LJ, Zhang P, Fan MY, Xu XJ, Wang CP, Tang JC, Sun HW (2021) Efficient degradation of p-nitrophenol by Fe@pomelo peel-derived biochar composites and its mechanism of simultaneous reduction and oxidation process. Chemosphere 267:129213. https://doi.org/10.1016/j.chemosphere.2020.129213
Pan B, Li H, Lang D, Xing BS (2019) Environmentally persistent free radicals: occurrence, formation mechanisms and implications. Environ Pollut 248:320–331. https://doi.org/10.1016/j.envpol.2019.02.032
Pan WX, Chang JM, He SM, Xue Q, Liu X, Fu JJ, Zhang AQ (2021) Major influence of hydroxyl and nitrate radicals on air pollution by environmentally persistent free radicals. Environ Chem Lett 19:4455–4461. https://doi.org/10.1007/s10311-021-01278-9
Pryor WA, Stone K, Zang L-Y, Bermúdez E (1998) Fractionation of aqueous cigarette tar extracts: fractions that contain the tar radical cause DNA damage. Chem Res Toxicol 11:441–448. https://doi.org/10.1021/tx970159y
Qin Y, Li G, Gao Y, Zhang L, Ok YS, An T (2018) Persistent free radicals in carbon-based materials on transformation of refractory organic contaminants (ROCs) in water: a critical review. Water Res 137:130–143. https://doi.org/10.1016/j.watres.2018.03.012
Qin LJ, Yang LL, Liu XY, Li C, Lin BC, Zheng MH, Liu GR (2021a) Formation of environmentally persistent free radicals from thermochemical reactions of catechol. Sci Total Environ 772:145313. https://doi.org/10.1016/j.scitotenv.2021.145313
Qin LJ, Yang LL, Yang JH, Weber R, Ranguelova K, Liu XY, Lin BC, Li C, Zheng MH, Liu GR (2021b) Photoinduced formation of persistent free radicals, hydrogen radicals, and hydroxyl radicals from catechol on atmospheric particulate matter. Iscience 24:102193. https://doi.org/10.1016/j.isci.2021.102193
Reed JR, Cawley GF, Ardoin TG, Dellinger B, Lomnicki SM, Hasan F, Kiruri LW, Backes WL (2014) Environmentally persistent free radicals inhibit cytochrome P450 activity in rat liver microsomes. Toxicol Appl Pharmacol 277:200–209. https://doi.org/10.1016/j.taap.2014.03.021
Reed JR, dela Cruz ALN, Lomnicki SM, Backes WL (2015a) Environmentally persistent free radical-containing particulate matter competitively inhibits metabolism by cytochrome P450 1A2. Toxicol Appl Pharmacol 289:223–230. https://doi.org/10.1016/j.taap.2015.09.021
Reed JR, dela Cruz ALN, Lomnicki SM, Backes WL (2015b) Inhibition of cytochrome P450 2B4 by environmentally persistent free radical-containing particulate matter. Biochem Pharmacol 95:126–132. https://doi.org/10.1016/j.bcp.2015.03.012
Sakr NI, Kizilkaya O, Carlson SF, Chan SM, Oumnov RA, Catano J, Kurtz RL, Hall RW, Poliakoff ED, Sprunger PT (2021) Formation of environmentally persistent free radicals (EPFRs) on the phenol-dosed alpha-Fe2O3 (0001) surface. J Phys Chem C 125:21882–21890. https://doi.org/10.1021/acs.jpcc.1c04298
Saravia J, Lee GI, Lomnicki S, Dellinger B, Cormier SA (2013) Particulate matter containing environmentally persistent free radicals and adverse infant respiratory health effects: a review. J Biochem Mol Toxicol 27:56–68. https://doi.org/10.1002/jbt.21465
Sarmiento DJ, Majestic BJ (2023) Formation of environmentally persistent free radicals from the irradiation of polycyclic aromatic hydrocarbons. J Phys Chem A 127:5390–5401. https://doi.org/10.1021/acs.jpca.3c01405
Squadrito GL, Cueto R, Dellinger B, Pryor WA (2001) Quinoid redox cycling as a mechanism for sustained free radical generation by inhaled airborne particulate matter. Free Radical Biol Med 31:1132–1138. https://doi.org/10.1016/s0891-5849(01)00703-1
Stone K, Bermudez E, Zang LY, Carter KM, Queenan KE, Pryor WA (1995) The ESR properties, DNA nicking, and DNA association of aged solutions of catechol versus aqueous extracts of tar from cigarette-smoke. Arch Biochem Biophys 319:196–203. https://doi.org/10.1006/abbi.1995.1282
Tang Z, Zhao S, Qian YJ, Jia HZ, Gao P, Kang YM, Lichtfouse E (2021) Formation of persistent free radicals in sludge biochar by hydrothermal carbonization. Environ Chem Lett 19:2705–2712. https://doi.org/10.1007/s10311-021-01198-8
Truong H, Loranicki S, Dellinger B (2008) Mechanisms of molecular product and persistent radical formation from the pyrolysis of hydroquinone. Chemosphere 71:107–113. https://doi.org/10.1016/j.chemosphere.2007.10.007
Valavanidis A, Fiotakis K, Bakeas E, Vlahogianni T (2005) Electron paramagnetic resonance study of the generation of reactive oxygen species catalysed by transition metals and quinoid redox cycling by inhalable ambient particulate matter. Redox Rep 10:37–51. https://doi.org/10.1179/135100005x21606
Valavanidis A, Iopoulos N, Gotsis G, Fiotakis K (2008) Persistent free radicals, heavy metals and PAHs generated in particulate soot emissions and residue ash from controlled combustion of common types of plastic. J Hazard Mater 156:277–284. https://doi.org/10.1016/j.jhazmat.2007.12.019
Vejerano E, Lomnicki S, Dellinger B (2011) Formation and stabilization of combustion-generated environmentally persistent free radicals on an Fe(III)2O3/silica surface. Environ Sci Technol 45:589–594. https://doi.org/10.1021/es102841s
Vejerano E, Lomnicki S, Dellinger B (2012a) Lifetime of combustion-generated environmentally persistent free radicals on Zn(II)O and other transition metal oxides. J Environ Monit 14:2803–2806. https://doi.org/10.1039/c2em30545c
Vejerano E, Lomnicki SM, Dellinger B (2012b) Formation and stabilization of combustion-generated, environmentally persistent radicals on Ni(II)O supported on a silica surface. Environ Sci Technol 46:9406–9411. https://doi.org/10.1021/es301136d
Vejerano EP, Rao GY, Khachatryan L, Cormier SA, Lomnicki S (2018) Environmentally persistent free radicals: insights on a new class of pollutants. Environ Sci Technol 52:2468–2481. https://doi.org/10.1021/acs.est.7b04439
Wang PL, Thevenot P, Saravia J, Ahlert T, Cormier SA (2011) Radical-containing particles activate dendritic cells and enhance Th17 inflammation in a mouse model of asthma. Am J Respir Cell Mol Biol 45:977–983. https://doi.org/10.1165/rcmb.2011-0001OC
Wang P, Pan B, Li H, Huang Y, Dong XD, Ai F, Liu LY, Wu M, Xing BS (2018) The overlooked occurrence of environmentally persistent free radicals in an area with low-rank coal burning, Xuanwei, China. Environ Sci Technol 52:1054–1061. https://doi.org/10.1021/acs.est.7b05453
Wang GY, Yu JL, Su Y, Shi GF (2019) Distribution and regeneration of hydroxyl free radicals in gaseous and particulate phases of pollutants in near-ground ambient air. Sci Total Environ 683:221–230. https://doi.org/10.1016/j.scitotenv.2019.05.300
Wang L, Liang DL, Liu JR, Du L, Vejerano E, Zhang XH (2022a) Unexpected catalytic influence of atmospheric pollutants on the formation of environmentally persistent free radicals. Chemosphere 303:134854. https://doi.org/10.1016/j.chemosphere.2022.134854
Wang W, Liu ZH, Li YX, Wang WX, Zhang QZ, Wang Q (2022b) Heterogeneous formation of EPFRs from aromatic adsorbates on the carbonaceous particulate matter. Appl Surf Sci 602:154316. https://doi.org/10.1016/j.apsusc.2022.154316
Wang W, Zhang RY, Liu ZH, Wang WX, Zhang QZ, Wang Q (2022c) Periodic DFT calculation for the formation of EPFRs from phenol on gamma-Al2O3 (110): site-dependent mechanism and the role of ambient water. J Environ Chem Eng 10:108386. https://doi.org/10.1016/j.jece.2022.108386
Wang Y, Gu XF, Huang Y, Ding ZH, Chen YJ, Hu X (2022d) Insight into biomass feedstock on formation of biochar-bound environmentally persistent free radicals under different pyrolysis temperatures. RSC Adv 12:19318–19326. https://doi.org/10.1039/d2ra03052g
Wang ZW, Xu PA, Wang H, Almatrafi E, Zhou CY, He YZ, Yang HL, Chen S, Tang WW, Zeng ZT, Zeng GM (2022e) Environmentally persistent free radicals in bismuth-based metal-organic layers derivatives: photodegradation of pollutants and mechanism unravelling. Chem Eng J (lausanne) 430:133026. https://doi.org/10.1016/j.cej.2021.133026
Wu JZ, Liu Y, Zhang J, Zhou JZ, Liu ZX, Zhang X, Qian GR (2020) A density functional theory calculation for revealing environmentally persistent free radicals generated on PbO particulate. Chemosphere 255:126910. https://doi.org/10.1016/j.chemosphere.2020.126910
Wu MX, Zhao ZY, Zhang P, Wan MD, Lei JL, Pan B, Xing BS (2021) Environmental persistent free radicals in diesel engine exhaust particles at different altitudes and engine speeds. Sci Total Environ 796:148963. https://doi.org/10.1016/j.scitotenv.2021.148963
Xu Y, Lu X, Su G, Chen X, Meng J, Li Q, Wang C, Shi B (2023) Scientific and regulatory challenges of environmentally persistent free radicals: from formation theory to risk prevention strategies. J Hazard Mater 456:131674. https://doi.org/10.1016/j.jhazmat.2023.131674
Yang J, Pan B, Li H, Liao SH, Zhang D, Wu M, Xing BS (2016) Degradation of p-nitrophenol on biochars: role of persistent free radicals. Environ Sci Technol 50:694–700. https://doi.org/10.1021/acs.est.5b04042
Yang LL, Liu GR, Zheng MH, Jin R, Zhao YY, Wu XL, Xu Y (2017a) Pivotal roles of metal oxides in the formation of environmentally persistent free radicals. Environ Sci Technol 51:12329–12336. https://doi.org/10.1021/acs.est.7b03583
Yang LL, Liu GR, Zheng MH, Jin R, Zhu QQ, Zhao YY, Wu XL, Xu Y (2017b) Highly elevated levels and particle-size distributions of environmentally persistent free radicals in haze-associated atmosphere. Environ Sci Technol 51:7936–7944. https://doi.org/10.1021/acs.est.7b01929
Yi J-F, Lin Z-Z, Li X, Zhou Y-Q, Guo Y (2023) A short review on environmental distribution and toxicity of the environmentally persistent free radicals. Chemosphere 340:139922. https://doi.org/10.1016/j.chemosphere.2023.139922
Yu XW, Liu HY, Kang F, Zhu BQ, Wu XD, Han MM, Hu CG, Huang X, Wang LQ, Chu YQ, Li J, Xie ZQ (2021) Air pollution in the operating room: a case study of characteristics of airborne particles, PAHs and environmentally persistent free radicals. Atmos Pollut Res 12:101257. https://doi.org/10.1016/j.apr.2021.101257
Yuan ZH, Huang QJ, Wang ZQ, Wang H, Luo JM, Zhu NW, Cao XD, Lou ZY (2022) Medium-low temperature conditions induce the formation of environmentally persistent free radicals in microplastics with conjugated aromatic-ring structures during sewage sludge pyrolysis. Environ Sci Technol 56:16209–16220. https://doi.org/10.1021/acs.est.2c04453
Zhang YZ, Yin MC, Sun XD, Zhao J (2020) Implication for adsorption and degradation of dyes by humic acid: light driven of environmentally persistent free radicals to activate reactive oxygen species. Biores Technol 307:123183. https://doi.org/10.1016/j.biortech.2020.123183
Zhang YZ, Xu MQ, Liang SX, Feng ZY, Zhao J (2021a) Mechanism of persulfate activation by biochar for the catalytic degradation of antibiotics: synergistic effects of environmentally persistent free radicals and the defective structure of biochar. Sci Total Environ 794:148707. https://doi.org/10.1016/j.scitotenv.2021.148707
Zhang YZ, Xu MQ, Liu XK, Wang M, Zhao J, Li SY, Yin MC (2021b) Regulation of biochar mediated catalytic degradation of quinolone antibiotics: important role of environmentally persistent free radicals. Biores Technol 326:124780. https://doi.org/10.1016/j.biortech.2021.124780
Zhao S, Zhang C, Ni Z, Zhu K, Liu J, Dai Y, Jia H (2020) Optimized extraction of environmentally persistent free radicals from clays contaminated by polycyclic aromatic hydrocarbons. Environ Chem Lett 18:949–955. https://doi.org/10.1007/s10311-020-00982-2
Zhao ZY, Wu MX, Zhou DD, Chen Q, Li H, Lang D, Pan B, Xing BS (2021) CuO and TiO2 particles generated more stable and stronger EPFRs in dark than under UV-irradiation. Sci Total Environ 775:145555. https://doi.org/10.1016/j.scitotenv.2021.145555
Zhao J, Shen G, Shi L, Li H, Lang D, Zhang L, Pan B, Tao S (2022) Real-world emission characteristics of environmentally persistent free radicals in PM2.5 from residential solid fuel combustion. Environ Sci Technol 56:3997–4004. https://doi.org/10.1021/acs.est.1c08449
Zhao J, Shi L, Shi J, Li H, Lang D, Wei Z, Li S, Pan B (2023) Distribution of environmentally persistent free radicals in size-segregated PMs emitted from residential biomass fuel combustion. J Hazard Mater 449:130956. https://doi.org/10.1016/j.jhazmat.2023.130956
Zhu K, Jia H, Zhao S, Xia T, Guo X, Wang T, Zhu L (2019a) Formation of environmentally persistent free radicals on microplastics under light irradiation. Environ Sci Technol 53:8177–8186. https://doi.org/10.1021/acs.est.9b01474
Zhu Y, Wei J, Liu Y, Liu X, Li J, Zhang J (2019b) Assessing the effect on the generation of environmentally persistent free radicals in hydrothermal carbonization of sewage sludge. Sci Rep 9:17092. https://doi.org/10.1038/s41598-019-53781-3
Zhu K, Jia H, Sun Y, Dai Y, Zhang C, Guo X, Wang T, Zhu L (2020) Long-term phototransformation of microplastics under simulated sunlight irradiation in aquatic environments: roles of reactive oxygen species. Water Res 173:115564. https://doi.org/10.1016/j.watres.2020.115564
Zhu L, Liu JB, Zhou JY, Wu XT, Yang KJ, Ni Z, Liu Z, Jia HZ (2022) The overlooked toxicity of environmentally persistent free radicals (EPFRs) induced by anthracene transformation to earthworms (Eisenia fetida). Sci Total Environ 853:158571. https://doi.org/10.1016/j.scitotenv.2022.158571
Funding
This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, China (Grant Nos. XDA23010300 and XDA23010000), National Key Research and Development Program of China, (Grant No. 2016YFA0203000), Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant Nos. 2022415 and 2023429), National Natural Science Foundation of China (Grant Nos. 51878644 and 41573138), the Youth Cross Team Scientific Research Project of the Chinese Academy of Sciences (JCTD-2022-17).
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XW: contributed to conceptualization, investigation, writing—original draft. HL: helped in investigation, writing—original draft. YX, LC, and YH: performed project administration, funding acquisition, and writing—review and editing. LC, and KH were involved in writing—review and editing.
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Wang, X., Liu, H., Xue, Y. et al. Formation of environmentally persistent free radicals and their risks for human health: a review. Environ Chem Lett 22, 1327–1343 (2024). https://doi.org/10.1007/s10311-024-01701-x
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DOI: https://doi.org/10.1007/s10311-024-01701-x