Environmentally Persistent Free Radicals Research Articles

What are the drivers of tetracycline photolysis induced by polystyrene microplastic?

Tetracycline (TC) and polystyrene microplastics (PS MPs), co-occurring in environments inevitably, have been frequently detected in a variety of environmental media. The two major types of emerging pollutants are attracting the global concern due to their potential threat to biota. PS can serve as carriers of TC in aquatic environments, thus dramatically altering environmental behavior of individual PS or TC. However, the photolysis of TC induced by PS remains unknown. In this study, kinetic experiments, quenching experiments, electron paramagnetic resonance analysis (EPR), Two-dimensional correlation Fourier transform infrared spectroscopy (2D-FTIR-COS) and products identification, were conducted to investigate effect and underlying mechanism of PS on photolysis of TC under sunlight irradiation. The corresponding results demonstrated that PS could induce photolysis of TC. The hydroxyl radicals (·OH), singlet oxygen (1O2) and superoxide anion (O2·-) enhanced degradation of TC. Quantitative quenching analysis revealed that both 1O2 and O2·- were main contributors, with contributions of 15.25 ± 2.21% and 11.69 ± 1.84%, respectively. Simultaneously, PS was aged during photolysis of TC, and the intension of O/C was enhanced from 2.07% to 17.92% with increasing aging time. Interestingly, we verified that highly aged PS significantly accelerated the photolysis due to generation of environmentally persistent free radicals (EPFRs), and the degradation pathway of TC induced by PS was firstly proposed. Subsequently, the transformation mainly included five reactions: hydrolysis, hydroxylation, deamination, demethylation and decarbonylation. This work provided a promising strategy for better understanding environmental fate of antibiotics and MPs.

Spatial distribution, pollution characterization, and risk assessment of environmentally persistent free radicals in urban road dust from central China

Environmentally persistent free radicals (EPFRs) have aroused widespread concern due to their potential adverse health effects. Research on EPFRs in road dust is still very limited. In this study, 86 road dust samples were collected using vacuum sampling in a rapidly developing city in central China. The pollution characterization and health risk of EPFRs in the urban road dust were then systematically analyzed. The results showed the average concentrations of EPFRs in urban road dust and fraction of particle with aerodynamic diameters lower than 10 μm (PM10) were 2.24 × 1017 to 3.72 × 1019 spins·g−1 and 6.02 × 1017 to 1.41 × 1020 spins g−1, respectively. The concentrations of EPFRs in dust from expressways, arterial roads, and secondary trunk roads were significantly higher than those found in the remaining road types. The g-factors of 2.0032–2.0039 indicated that the EPFRs have consisted of oxygen-centered and carbon-centered radicals or carbon-centered radicals with nearby oxygen or halogen atoms. Moreover, three decay patterns of EPFRs were observed: a fast decay followed by a slow decay, a single slow decay, and the slowest decay. In addition, a comparative evaluation was made for probabilistic risk assessments of exposure to the EPFRs in road dust and the PM10 fraction. Compared with road dust, the probability of the number of equivalent cigarettes to exceed the 100 and 200 cigarettes for inhaling EPFRs in the PM10 fraction increased by 27.0% and 25.0%, respectively. The simulation results showed the PM10 fraction were primarily deposited in the upper respiratory tract regions (57.1%) and pulmonary regions (28.8%). The findings of this study suggest a potential risk of EPFRs in inhalable particles and provide a new insight for further exploration of the EPFRs in fine particles of road dust.

Insight into biomass feedstock on formation of biochar-bound environmentally persistent free radicals under different pyrolysis temperatures.

Environmentally persistent free radicals (EPFRs) in biochars have the ability of catalytic formation of reactive oxygen species, which may pose potential oxidative stresses to eco-environment and human health. Therefore, comprehending the formation and characteristics of EPFRs in biochars is important for their further applications. In this study, the woody lignocellulosic biomass (wood chips, pine needle and barks), non-woody lignocellulosic biomass (rice husk, corn stover, and duckweed), and non-lignocellulosic biomass (anaerobically digested sludge) were selected as biomass feedstock to prepare biochars under different pyrolysis temperatures (200–700 °C). The impact of biomass feedstock on formation of biochar-bound EPFRs was systematically compared. Elemental compositions and atomic ratios of H/C and O/C varied greatly among different biomass feedstocks and the subsequently resulting biochars. EPFRs in biochars derived from the studied lignocellulosic biomass have similar levels of spin concentrations (1018–1019 spins per g) except for lower EPFRs in biochars under 200 and 700 °C; however, sludge-based biochars, a typical non-lignocellulosic-biomass-based biochar, have much lower EPFRs (1016 spins per g) than lignocellulosic-biomass-based biochars under all the studied pyrolysis temperatures. Values of g factors ranged from 2.0025 to 2.0042 and line width was in the range of 2.15–11.3 for EPFRs in the resulting biochars. Spin concentrations of biochar-bound EPFRs increased with the increasing pyrolysis temperatures from 200 to 500 °C, and then decreased rapidly from 500 to 700 °C and oxygen-centered radicals shifted to carbon-centered radicals with the increasing pyrolysis temperatures from 200 to 700 °C for all the studied biomass feedstock. 300–500 °C was the appropriate pyrolysis temperature range for higher levels of spin concentrations of biochar-bound EPFRs. Moreover, EPFRs' concentrations had significantly positive correlation with C contents and weak or none correlation with contents of transition metals. Overall, different types of biomass feedstock have significant impact on the formation of EPFRs in the resulting biochars.

Generation of environmentally persistent free radicals on faceted TiO2 in an ambient environment: roles of crystalline surface structures

The formation of environmentally persistent free radicals (EPFRs) is highly correlated with the structure of mineral crystal surfaces.

Pollution Characteristics of Environmental Persistent Free Radicals (Epfrs) and Their Contribution to Oxidation Potential in Road Dust in a Large City in Northwest China

Pollution Characteristics of Environmental Persistent Free Radicals (Epfrs) and Their Contribution to Oxidation Potential in Road Dust in a Large City in Northwest China

On the formation chemistry of brominated polycyclic aromatic hydrocarbons (BrPAHs)

Brominated polycyclic aromatic hydrocarbons (BrPAHs) have been consistently detected in various environmental matrices, and measured at alarming rates in stack emissions. However, formation mechanisms and bromination patterns of BrPAHs remain unclear. This contribution constructs detailed mechanistic pathways for the synthesis of selected BrPAHs (namely bromine-bearing naphthalene, acenaphthylene, anthracene, and phenanthrene). Mapped-out pathways follow the Bittner-Howard's route in the hydrogen abstraction acetylene addition (HACA) mechanism, in which a second C2HBr molecule is added to the first one. Constructed kinetic model portrays temperature-dependent profiles of major and minor species. Direct loss of an H atom from the acetylenic fragment appears to be more important at elevated temperatures, when compared with further addition of C2HBr cuts or ring-cyclization reactions. The occurrence of closed-shell Diels-Alder pathway should be inhibited owing to sizable enthalpic barriers. Fukui Indices for electrophilic substitutions (f−1) establish bromination’ s pattern of selected BrPAHs. The diradical character of BrPAHs coupled with electron-deficient C(Br) sites, render BrPAHs as potent precursors for the formation of environmentally persistent free radicals (EPFRs). Findings reported herein shall be useful in comprehending the formation chemistry of BrPAHs, a less-investigated category of toxicants in thermal systems.

Formation of environmentally persistent free radicals from photodegradation of triclosan by metal oxides/silica suspensions and particles

Metal oxides play an essential role in the photocatalysis of contaminants and substantially increase in the environment by the engineering production. However, whether emerging contaminants will be produced during photocatalysis of contaminants remains unclear. Here, triclosan (TCS) photodegradation in metal oxides/silica suspensions and particles, simulated as the states of metal oxides in water and soil environments, were studied. The photodegradation results confirmed that metal oxides exhibited a double-effect. They promoted TCS photodegradation by generating reactive oxidizing species (ROS) in metal oxides/silica suspensions and inhibited the photodegradation by competing with TCS for irradiation in metal oxides/silica particles. In this study, the critical discovery was the formation of emerging contaminants, environmentally persistent free radicals (EPFRs), and EPFRs yields were promoted by metal oxides (Al2O3, ZnO, TiO2). They were more stable in metal oxides than silica, and the half-lives ranged from 6.7 h to 90.9 d. Although CuO did not increase EPFRs yields compared to silica, the half-lives of EPFRs were also longer. In addition, this study found that EPFRs yields were dependent on the metal oxides concentrations. Our results provided a new insight into the negative environmental impacts of metal oxides and improved our understanding of the formation and fate of EPFRs by metal oxides in soil and aquatic environments.

Photoaged polystyrene microplastics serve as photosensitizers that enhance cimetidine photolysis in an aqueous environment

Microplastics (MPs) have received much attention in recent years because of their continuous photoaging process in aquatic environments. However, little research has been conducted on the photochemistry of aged microplastics and the associated effects on coexisting pharmaceuticals. This study investigated the photodegradation of cimetidine via aged polystyrene microplastics (PS-MPs) with different aging times (0–7 d) under simulated sunlight irradiation (700 W/m2). PS-MPs with 5 d of aging time resulted in much faster cimetidine degradation (>99%) after 2 h of irradiation than pristine PS-MPs (<8%). The enhanced photodegradation of cimetidine by aged PS-MPs was related to the increase in chromophoric oxygenated groups (CO, C–O) followed by redshifted absorbance through the photoaging process, which induced the formation of the environmentally persistent free radicals (EPFRs) OH, 1O2 and 3PS*. However, only 1O2 and 3PS* contributed to enhanced cimetidine photodegradation, with 1O2 playing a more important role in our case. This work also demonstrated that other compounds that are susceptible to indirect photolysis, such as codeine and morphine, are likewise significantly degraded under irradiation in the presence of aged PS-MPs. Although previous studies have reported how MPs can increase the persistence of contaminants, this study demonstrates that MPs can serve as photosensitizers and alter the fate of coexisting pharmaceuticals in aquatic environments.

Exposure to combustion derived particulate matter exacerbates influenza infection in neonatal mice by inhibiting IL22 production

BackgroundParticulate matter (PM) containing environmentally persistent free radicals (EPFRs) are formed during various combustion processes, including the thermal remediation of hazardous wastes. Exposure to PM adversely affects respiratory health in infants and is associated with increased morbidity and mortality due to acute lower respiratory tract infections. We previously reported that early-life exposure to PM damages the lung epithelium and suppresses immune responses to influenza virus (Flu) infection, thereby enhancing Flu severity. Interleukin 22 (IL22) is important in resolving lung injury following Flu infection. In the current study, we determined the effects of PM exposure on pulmonary IL22 responses using our neonatal mouse model of Flu infection.ResultsExposure to PM resulted in an immediate (0.5–1-day post-exposure; dpe) increase in IL22 expression in the lungs of C57BL/6 neonatal mice; however, this IL22 expression was not maintained and failed to increase with either continued exposure to PM or subsequent Flu infection of PM-exposed mice. This contrasts with increased IL22 expression in age-matched mice exposed to vehicle and Flu infected. Activation of the aryl hydrocarbon receptor (AhR), which mediates the induction and release of IL22 from immune cells, was also transiently increased with PM exposure. The microbiome plays a major role in maintaining epithelial integrity and immune responses by producing various metabolites that act as ligands for AhR. Exposure to PM induced lung microbiota dysbiosis and altered the levels of indole, a microbial metabolite. Treatment with recombinant IL22 or indole-3-carboxaldehyde (I3A) prevented PM associated lung injury. In addition, I3A treatment also protected against increased mortality in Flu-infected mice exposed to PMs.ConclusionsTogether, these data suggest that exposure to PMs results in failure to sustain IL22 levels and an inability to induce IL22 upon Flu infection. Insufficient levels of IL22 may be responsible for aberrant epithelial repair and immune responses, leading to increased Flu severity in areas of high PM.

In Vitro Assessment Reveals the Effects of Environmentally Persistent Free Radicals on the Toxicity of Photoaged Tire Wear Particles.

Tire wear particles (TWP) have been identified as one of the major sources of microplastics (MPs), and few studies have focused on their environmental behaviors and impacts. However, a thorough characteristic and toxicity assessment associated with environmentally persistent free radicals (EPFRs) on the photoaged TWP is missing. In this study, we investigated EPFRs in the process of TWP photoaging and evaluated their toxicity using in vitro bioassays. Our results showed that a total of around 1.0 × 1017 spins/g EPFRs (g-factors ranging 2.00308-2.00318) was formed on TWP with 60 days of light irradiation, which contained more than 29% of reactive EPFRs (r-EPFRs). Using macrophages as model cells for bioassays, TWP-associated EPFRs trigged endpoints, including the decrease of cell viability (27 to 45%) and the increase of oxidative stress response (46-93%) and inflammatory factor secretion. The enhancement of TWP toxicity with photoaging was confirmed to be attributed to the generated EPFRs combined with other TWP's chemical compositions (e.g., various metals and organics). Most importantly, the toxicity of photoaged TWP was closely correlated with the generated r-EPFRs, which induced reactive oxidant species (ROS) generation. This study provides direct evidence of toxicity on the photoaged TWP particles, revealing the potential contributions of EPFRs to the adverse effect on human health and highlighting the need for an improved understanding of the impacts of EPFRs on the risk assessment of TWP released into the environment.

Source apportionment of environmentally persistent free radicals (EPFRs) and heavy metals in size fractions of urban arterial road dust

The partitioning of pollutants in the size-fractions of road dust particles is extremely important to their migration and bioavailability in the air environment. Herein, the pollution characteristics and sources of heavy metals (As, Cd, Cu, Cr, Pb, Zn, Co, Mn, Ni) and environmentally persistent free radicals (EPFRs) are investigated in 64 samples of mixed particle-size road dust in four size fractions (>250 µm, 150–250 µm, 75–150 µm,<75 µm). The samples were collected from urban arterial roads of three cities in the core of Central Plains Urban Agglomeration. The results indicate that 67.70% of the road dust (by mass) consist of the<75 µm particles size fraction, and that the highest levels of EPFRs and heavy metals are concentrated in the<150 µm and< 75 µm size fractions. In addition, Cd exhibits extremely high average enrichment factors (EFs) of 51.84 in the 75–150 µm fraction and 64.80 in the<75 µm fraction. Further analysis reveals a remarkable correlation between EPFR concentration and the concentrations Zn and Cr in the road dust. An application of principal component analysis (PCA) and positive matrix factorization (PMF) to the regional investigation and the layout of functional zones demonstrates that Cr, Pb, Zn and EPFRs are mainly derived from traffic emissions, and account for 51.45–77.86% of the fine particle fraction (<150 µm). Meanwhile, industrial activities are identified as the primary source of Cd and Cu, accounting for 63.07–76.22% of the<150 µm particle size fraction. These findings suggest a potential risk of EPFRs and heavy metals in fine particulate matter, and provide a new insight into the potential sources and health risks of EPFRs in road dust. Therefore, further studies are needed in order to explore the EPFRs in fine particulate particles and to assess their effects upon human health.

Characteristics and sources of environmentally persistent free radicals in PM2.5 in Dalian, Northeast China: correlation with polycyclic aromatic hydrocarbons.

Environmentally persistent free radicals (EPFRs) are an emerging class of environmental hazardous contaminants that extensively, stably exist in airborne particulate matter and pose harmful effects on human health. However, there was little research about the sources of EPFRs in actual atmospheric conditions. This study reported the occurrence, characteristics, and sources of EPFRs and polycyclic aromatic hydrocarbons (PAHs) in PM2.5 collected in Dalian, China. The concentrations of PM2.5-bound EPFRs ranged from 1.13 × 1013 to 8.97 × 1015 spins/m3 (mean value: 1.14 × 1015 spins/m3). Carbon-centered radicals and carbon-centered radicals with adjacent oxygen atoms were detected. The concentration of ∑PAHs ranged from 1.09 to 76.24ng/m3, and PAHs with high molecular weight (HMW) were predominant species in PM2.5. Correlation of EPFRs with SO2, NO2, O3, and 12 kinds of PAHs indicated that both fuel (coal and biomass) combustion and photoreaction in atmosphere influenced the concentrations of EPFR. The positive matrix factorization (PMF) model results have shown that the primary sources contributed most of the EPFRs and those of secondary sources had a little proportion. Coal combustion (52.4%) was the primary contributor of EPFRs, followed by traffic emission (22.6%), industrial sources (9.6%), and secondary sources (9.2%) during the heating period, whereas industrial emission (39.2%) was the primary contributor, followed by coal combustion (38.1%), vehicular exhaust (23.5%), and secondary sources (9.6%) during the non-heating period. The finding of the present study provides an important evidence for further study on the formation mechanism of EPFRs in actual atmospheric to control the air pollution.

Photoformation of environmentally persistent free radicals on particulate organic matter in aqueous solution: Role of anthracene and formation mechanism

Environmentally persistent free radicals (EPFRs) generated under irradiation have been widely detected in soil particles, atmospheric particles and microplastic particles, but the formation of EPFRs in water is not well understood. This study investigated the formation of EPFRs on particulate organic matter (POM) in water contaminated by anthracene (Ant) under irradiation. The photoformation and decay progress of EPFRs was represented with the help of electron paramagnetic resonance (EPR) technique on both actual POM and Fe(III)-montmorillonite simulated samples. EPR signals at the range of 1016 to 1017 spin/g were detected and the half-life time of EPFRs stored in water was at around 16.62 h and 60.80 h, much shorter than those in the air. The g factors were all larger than 2.0040, which indicated the generation of oxygen centered EPFRs. The primary intermediates were identified by gas chromatography-mass spectrometer (GC-MS) and a possible EPFR formation pathway during Ant degradation was proposed. The interaction between Ant and POM, and the hydroxylation and carbonylation of the intermediates made contributions to the generation of EPFRs. Meanwhile, the indirect photodegradation of bisphenol A (BPA) has been demonstrated by analyzing the reactive oxygen species (ROS) and photogenerated electrons in the solution with POM containing EPFRs. It is found that hydroxyl radicals (•OH) and singlet oxygen (1O2) were induced and might promote the photodegration. Overall, our present study provided useful information to understand the photoformation of EPFRs on POM and their fate in aqueous environments.

Air pollution in the operating room: A case study of characteristics of airborne particles, PAHs and environmentally persistent free radicals

Air quality in the microenvironment of operating rooms (ORs) has attracted much attention as surgical smoke may pose health risks. We investigated air pollution in the operating room with a laminar flow system by examining the number and size distribution of airborne particles, the chemical composition and morphology of single particles, and polycyclic aromatic hydrocarbons (PAHs). In addition, environmentally persistent free radicals (EPFRs) in ORs are reported for the first time. The results showed that there were high levels of fine particles, EPFRs, and PAHs in laminar flow operating rooms during surgical procedures. PM2.5 is the dominant particle in ORs (accounting for >90%), consisting mainly of calcareous and metal-related particles based on the morphology and chemical analysis of single particles. In addition, anesthetic gas-related particles were found in the fine particles, and their toxicology requires more attention. EPFRs in the ORs were mainly carbon-centered radicals that may be reactive to cells. The concentrations of EPFRs and PAHs in ORs were higher than in the outside environment and present a potential health risk to surgeons and anesthetists. Hence, effective filtration and evacuation of surgical smoke are necessary.

Characteristics and Potential Inhalation Exposure Risks of Environmentally Persistent Free Radicals in Atmospheric Particulate Matter and Solid Fuel Combustion Particles in High Lung Cancer Incidence Area, China

Environmentally persistent free radicals (EPFRs) were previously considered an unrecognized composition of air pollutants and might help explain the long-standing medical mystery of why non-smokers develop tobacco-related diseases such as lung cancer. However, there is no investigated on EPFRs in Xuanwei rural areas, especially in high prevalence of lung cancer areas. In this study, we selected six types of coal and three types of biomass in Xuanwei, then conducted simulated combustion, and six group of atmospheric particulate matters (APMs) to explore the content and particle size distribution pattern of EPFRs and a new health risk assessment method to evaluate the risk of EPFRs in PM for adults and children. Our results show that the contribution of EPFRs for biomass combustion, coal combustion and APMs were mainly distributed in the size range of &lt;1.1 μm, which accounted for 76.15 ± 4.14%, 74.85 ± 10.76%, and 75.23 ± 8.18% of PM3.3. The mean g factors and ΔHp-p indicated that the EPFRs were mainly oxygen-centered radicals in PM in Xuanwei. The results suggest that the health risk of EPFRs is significantly increased when the particle size distribution of EPFRs is taken into account, and coal combustion particulate matter (174.70 ± 37.86 cigarettes for an adult, 66.39 ± 14.39 cigarettes per person per year for a child) is more hazardous to humans than biomass combustion particulate matter (69.41 ± 4.83 cigarettes for an adult, 26.37 ± 1.84 cigarettes per person per year for), followed by APMs (102.88 ± 39.99 cigarettes for an adult, 39.10 ±15.20 cigarettes per person per year for) in PM3.3. Our results provides a new perspective and evidence for revealing the reason for the high incidence of lung cancer in Xuanwei, China.

Environmentally persistent free radicals in bismuth-based metal–organic layers derivatives: Photodegradation of pollutants and mechanism unravelling

Formation of environmentally persistent free radicals (EPFRs) on carbonaceous material has aroused increasing research attentions. In terms of metal organic frameworks (MOFs) derivatives, however, scarce studies have dedicated to the relevant aspects. Herein, EPFRs have been detected in Bi-metal organic layers (Bi-MOLs) derivatives. The corresponding g-factors and concentrations of EPFRs on Bi2O3@C by pyrolyzed at different temperatures were 2.0041–2.0046 and 7.04 × 1019-1.77 × 1020 spins/g, respectively. Interestingly, similar EPFRs signals were also monitored in HKUST-1 based and UiO-66 based derivatives. We observed that Bi2O3@C system with the highest EPFRs concentration exhibited superior degradation and mineralization efficiency for phenol and tetracycline. Its excellent photocatalytic performance was mainly attributed to the interaction between the internal EPFRs and photoinduced active species, which promoted more generation of reactive oxygen species (ROS) radicals. This hypothesis was supported by line correlations for EPFRs concentration vs. degradation kinetics in samples pyrolyzed at different temperatures (R2 = 0.946). Most significantly, mechanism investigation combined with DFT calculation indicated that the EPFRs not only promote the generation of 1O2 and •OH via molecular oxygen activation pathway but also provided a possibility of enhancing water oxidation by holes. These findings pave the way for MOFs derivative's implication and insight into the role of EPFRs in photocatalysis.

Reexamining the Formation of Environmentally Persistent Free Radicals from Aromatic Molecules on Metal Oxides

The subject is a debate on the formation mechanism of the environmentally persistent free radicals (EPFR), by interaction of aromatics with transition metal oxides. Literature reports contrasting opinions concerning the stabilization of the phenoxyradicals mainly as concerns the suggested reduction of interacting transition metal centers. The present paper, in accordance with the mechanisms assessed by a number of spectroscopic and computational results, excludes the necessity that the catalytic mechanism involves the reduction of the metal centers by interaction with the aromatics.Graphic

Formation of Environmentally Persistent Free Radicals (EPFRs) on the Phenol-Dosed α-Fe2O3(0001) Surface.

Environmentally persistent free radicals (EPFRs) are a class of toxic air pollutants that are found to form by the chemisorption of substituted aromatic molecules on the surface of metal oxides. In this study, we employ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) to perform a temperature-dependent study of phenol adsorption on α-Fe2O3(0001) to probe the radical formation mechanism by monitoring changes in the electronic structure of both the adsorbed phenol and metal oxide substrate. Upon dosing at room temperature, new phenol-derived electronic states have been clearly observed in the UPS spectrum at saturation coverage. However, upon dosing at high temperature (>200 °C), both photoemission techniques have shown distinctive features that strongly suggest electron transfer from adsorbed phenol to Fe2O3 surface atoms and consequent formation of a surface radical. Consistent with the experiment, DFT calculations show that phenoxyl adsorption on the iron oxide surface at RT leads to a minor charge transfer to the adsorbed molecule. The experimental findings at high temperatures agree well with the EPFRs' proposed formation mechanism and can guide future experimental and computational studies.

Inhalation of particulate matter containing free radicals leads to decreased vascular responsiveness associated with an altered pulmonary function.

Airborne particulate matter (PM) is associated with an increased risk for cardiovascular diseases. Although the goal of thermal remediation is to eliminate organic wastes through combustion, when incomplete combustion occurs, organics chemisorb to transition metals to generate PM-containing environmentally persistent free radicals (EPFRs). Similar EPFR species have been detected in PM found in diesel and gasoline exhaust, woodsmoke, and urban air. Prior in vivo studies demonstrated that EPFRs reduce cardiac function secondary to elevations in pulmonary arterial pressures. In vitro studies showed that EPFRs increase ROS and cytokines in pulmonary epithelial cells. We thus hypothesized that EPFR inhalation would promote lung inflammation and oxidative stress, leading to systemic inflammation, vascular endothelial injury, and a decline in vascular function. Mice were exposed to EPFRs for either 4 h or for 4 h/day for 10 days and lung and vascular function were assessed. After a 4-h exposure, plasma nitric oxide (NO) was reduced while endothelin-1 (ET-1) was increased, however lung function was not altered. After 10 day, plasma NO and ET-1 levels were again altered and lung tidal volume was reduced. These time course studies suggested the vasculature may be an early target of injury. To test this hypothesis, an intermediate time point of 3 days was selected. Though the mice exhibited no marked inflammation in either the lung or the blood, we did note significantly reduced endothelial function concurrent with a reduction in lung tidal volume and an elevation in annexin V protein levels in the lung. Although vascular dysfunction was not dependent upon inflammation, it may be associated with an injury at the air-blood interface. Gene expression analysis suggested roles for oxidative stress and aryl hydrocarbon receptor (Ahr) signaling. Studies probing the relationship between pulmonary oxidative stress and AhR signaling at the air-blood interface with vascular dysfunction seem warranted.NEW & NOTEWORTHY Particulate matter (PM) resulting from the combustion of organic matter is known to contribute to cardiopulmonary disease. Despite hypotheses that cardiovascular dysfunction occurring after PM exposures is secondary to lung or systemic inflammation, these studies investigating exposures to PM-containing environmentally persistent free radicals (EPFRs) demonstrate that cardiovascular dysfunction precedes pulmonary inflammation. The cardiopulmonary health consequences of EPFRs have yet to be thoroughly evaluated, especially in healthy, adult mice. Our data suggest the vasculature as a direct target of PM exposure, and our studies aimed to elucidate the mechanisms contributing to EPFR-induced vascular dysfunction.

Effect of pyrolysis conditions on environmentally persistent free radicals (EPFRs) in biochar from co-pyrolysis of urea and cellulose

Biochar derived from nitrogen-rich pyrolysis of biomass can be used as a soil conditioner, but it contains a large amount of environmental persistent free radicals (EPFRs). EPFRs are a newly identified environmentally harmful substance, and the detection and research on EPFRs in nitrogen-rich pyrolyzed char is lacking. Biochars prepared from cellulose-urea mixtures at different temperatures, residence times, and urea ratios were analyzed in this study. EPFRs in biochar prepared at 500 °C had the highest spin concentrations. Substituted aromatic compounds were the precursors to the EPFRs. The types of EPFRs in biochars shifted from oxygen-centered at 400 °C to carbon- and oxygen-centered in the 450–600 °C range due to a reduction in oxygen-containing functional groups. Residence time experiments showed that most EPFRs formed in the first 5 min of pyrolysis. C was the main element used for the formation of EPFRs, while N content was negatively correlated with the concentration of EPFRs. Pyrolysis temperature was the key factor determining the types of EPFRs produced, while proportion of urea only affected the concentrations of EPFRs and not type. The results of this study are of great significance for understanding the environmental behavior of common EPFRs in nitrogen-rich biochar.