Environmentally Persistent Free Radicals Research Articles

Synergetic promoting/inhibiting mechanisms of copper/calcium compounds in the formation of persistent organic pollutants and environmentally persistent free radicals from anthracene

Copper compounds are considered the strongest promotors of unintentional persistent organic pollutants (POPs) formation, while calcium compounds are widely used to inhibit this process. Understanding the mechanisms underlying these processes is important for synergetic control of multiple POPs. Herein, the promoting ability of CuCl2 on the synergetic formation of POPs from anthracene and the underlying mechanisms were clarified. During thermochemical reaction with CuCl2, Cu2+ was first reduced to Cu+, and finally oxidized to CuO. Furthermore, CuCl2 promoted the formation of environmentally persistent free radicals (EPFRs) during thermochemical reaction. The formed EPFRs were identified as anthrone-type and anthraquinone-type radicals using electron paramagnetic resonance spectroscopy and gas chromatography/quadrupole time-of-flight mass spectrometry. Synergetic inhibition of POPs and EPFRs was achieved using CaO. The inhibiting mechanism of CaO was attributed to the absorption of chlorine originating from CuCl2 through the formation of CaClOH and the inhibition of free radical intermediates for POPs formation.

Size-resolved exposure risk and subsequent role of environmentally persistent free radicals (EPFRs) from atmospheric particles

Environmentally persistent free radicals (EPFRs) are pollutants in the environment that have recently received widespread attention, but information about their formation and size-resolved distribution in atmospheric particles is scarce. We report the exposure risk and the related effect on human health of EPFRs in size-resolved (<10 μm) atmospheric particles in Xiamen, China, using electron paramagnetic resonance (EPR) spectroscopy. We found that the concentration of EPFRs in atmospheric particles ranged from 1.60 × 1013 spins/m3 to 24.48 × 1013 spins/m3, and the EPFRs concentration were lower in PM2.1–10 than in PM < 2.1. The results also present that g factor range observed in the spectra was 2.0031–2.0038. These EPFRs are considered to correspond to the g-factors of C-centred radicals with adjacent O atoms. In addition, the concentration of EPFRs was positively correlated with the concentrations of Cu, Fe, Mn, Pb and V. We also discuss reactive oxygen species (ROS), mainly OH radicals, which were formed by redox cycle of the EPFRs. The EPFRs deposition observed in the respiratory system was equal to smoking 29 cigarettes (extrathoracic: 13; tracheobronchial: 8; pulmonary: 8) per person per day. This study presents information about the potential pathogenic risks of size-resolved atmospheric particles, and this information has certain guiding significance for reducing respiratory diseases.

Real-World Emission Characteristics of Environmentally Persistent Free Radicals in PM2.5 from Residential Solid Fuel Combustion.

Environmentally persistent free radicals (EPFRs) can induce reactive oxygen species, causing adverse health impacts, and residential fuel (biomass and coal) combustion is believed to be an important emission source for EPFRs; however, the residential emission characteristics of EPFRs are rarely studied in the real world. Here, we conducted a field campaign evaluating the presence and characteristics of EPFRs generated from residential biomass and coal burning in rural China. The emission factors (EFs) of EPFRs (with units of 1020 spins·kg-1) in PM2.5 from the combustion of crop residues (3.97 ± 0.47) were significantly higher than those from firewood (2.06 ± 0.19) and coal (2.13 ± 0.33) (p < 0.05). The EPFRs from residential solid fuel combustion were carbon-centered free radicals adjacent to oxygen atoms. The fuel type was a primary factor controlling EPFR discharge, explaining 68% of the variation in EPFR EFs. The emissions from biomass burning had higher EPFRs per particle than those from coal combustion. EPFRs had stronger relationships with carbonaceous components than with other incomplete combustion products. The EPFRs from biomass burning were mostly generated during the pyrolysis of fuels, while the EPFRs generated from coal combustion were mainly associated with refractory organic compounds. This study provides valuable information for evaluating the fates of EPFRs, promoting a better understanding of the health impacts of air pollution.

Insight into urban PM2.5 chemical composition and environmentally persistent free radicals attributed human lung epithelial cytotoxicity

Fine particulate matter (PM2.5) is detrimental to the human respiratory system. However, the toxicity of PM2.5 and its associated potentially harmful species, notably novel pollutants like environmentally persistent free radicals (EPFRs), remains unclear. Therefore, one-year site monitoring and ambient air PM2.5 sampling in the Nanjing urban area was designed to investigate the relationships between chemical compositions (carbon fractions, metallic elements, and water-soluble ions) and EPFRs, and change in cytotoxicity with varying PM2.5 components. Oxidative stress (reactive oxygen species, ROS), inflammatory injury (IL-6 and TNF-α), and membrane injury (LDH) of human lung epithelial cells (A549) induced by PM2.5 were analyzed using in vitro cytotoxicity test. Both the composition and toxicity of PM2.5 from different seasons were compared. The average daily exposure of urban PM2.5 associated EPFRs load in Nanjing were 2.29 × 1011 spin m−3. Their exposure concentration and cytotoxic damage ability were stronger in the cold season than warm. The particle compositions of metals and carbon fractions were significantly positively correlated with EPFRs. The airborne EPFRs, organic carbon (OC), and heavy metal Cu, As, and Pb may pose principal cell damage ability, which is worthy of further study interlinking aerosol pollution and health risks.

Generation of Environmentally Persistent Free Radicals on Metal-Organic Frameworks.

Environmentally persistent free radicals (EPFRs) have been recognized as one of the important emerging contaminants with biological toxicity, environmental persistence, and global mobility. Previous studies have identified the catalytic role of surface metal oxides in EPFRs formation and illustrated the metal-dependence of EPFRs by studying on various metal oxide nanoparticles and single crystals. However, there is still lack of an understanding on the formation of EPFRs from the point of view of metal sites. Various factors (e.g., crystalline phases and surface species) of metal oxides are regarded to contribute to the generation of EPFRs, which present profound difficulties for scientists to tease apart the impact of metal type. Herein, a laboratory investigation, in terms of the acidity and oxidation strength of metal cations, was conducted by selecting metal-variable isostructural metal-organic frameworks as material platforms. Specifically, we evaluated EPFRs generation on MIL-100(M) (M = Al, Cr, Fe) from chlorine-substituted phenol vapor and catechol under thermal conditions. It is found that high Lewis acidity of metal sites is crucial for capturing the above two phenolic precursors, activating the O-H bond and promoting EPFRs formation. Radical species with half-life as long as 70 days were generated on MIL-100 rich in 5-fold coordinated Al3+ sites. The unpaired electron spin density donation was further confirmed by using 27Al solid-state nuclear magnetic resonance spectroscopy. Despite their higher oxidation power than Al3+, the exposed Cr3+ and Fe3+ sites show undetectable catalytic activity for the formation of EPFRs, because of their insufficient Lewis acidity. Our results suggest that the surface species rather than Lewis acid sites may be a major contributor to the formation of EPFRs on metal oxides like Fe2O3.

Generation of environmental persistent free radicals (EPFRs) enhances ecotoxicological effects of the disposable face mask waste with the COVID-19 pandemic

A large amount of disposable plastic face masks (DPFs) is produced and used during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, which results in an inevitable consequence of the dramatic increase of DPFs waste. However, the impact of DPFs exposure to the environment on their toxicity is rarely considered. In this study, a range of 76–276 items/L microplastics (MPs) was detected in the DPFs leachates, and fibrous (> 80.3%) and polypropylene (PP, > 89.2%) MPs were dominant. Co, Cu, Ni, Sr, Ti and Zn, were commonly detected in all leachates of the tested DPFs. Organics, such as acetophenone, 2,4-Di-tert-butylphenol, benzothiazole, bisphenol-A and phthalide, were found in the DPFs leachate, which were including organic solvents and plasticizer. Besides, we first found an emerging environmental risk substance, namely environmentally persistent free radicals (EPFRs), was generated in the DPFs leachates. The characteristic g-factors of the EPFRs was in a range of 2.003–2.004, identified as mixture of carbon- and oxygen-centered radicals. By means of in vitro toxicity assay, the DPFs leachate were confirmed to cause cytotoxicity and oxidative stress. Significantly, it is found that the formed EPFRs could contribute more toxic effects. Furthermore, when compared to N95 respirators, the tested surgical masks tend to release more MPs, leach more metals and organics, and generate more EPFRs. Surgical masks were thus showed higher risk than N95 respirators after exposure to water. This work highlights the importance of understanding the chemical complexity and possible toxicity of DPFs for their risk assessment.

Pollution characteristics and sources of environmentally persistent free radicals and oxidation potential in fine particulate matter related to city lockdown (CLD) in Xi'an, China

The impact of COVID-19 control on air quality have been prevalent for the past two years, however few studies have explored the toxicity of atmospheric particulate matter during the epidemic control. Therefore, this research highlights the characteristics and sources of oxidative potential (OP) and the new health risk substances environmentally persistent free radicals (EPFRs) in comparison to city lockdown (CLD) with early days of 2019–2020. Daily particulate matter (PM2.5) samples were collected from January 14 to February 3, 2020, with the same period during 2019 in Xi'an city. The results indicated that the average concentration of PM2.5 decreased by 48% during CLD. Concentrations of other air pollutants and components, such as PM10, NO2, SO2, WSIs, OC and EC were also decreased by 22%, 19%, 2%, 17%, 6%, and 4% respectively during the CLD, compared to the same period in 2019. Whereas only O3 increased by 30% during CLD. The concentrations of EPFRs in PM2.5 was considerably lower than in 2019, which decreased by 12% during CLD. However, the OP level was increased slightly during CLD. Moreover, both EPFRs/PM and DTTv/PM did not decrease or even increase significantly, manifesting that the toxicity of particulate matter has not been reduced by more gains during the CLD. Based on PMF analysis, during the epidemic period, the contribution of traffic emission is significantly reduced, while EPFRs and DTTv increased, which consist of significant O3 and secondary aerosols. This research leads to able future research on human health effect of EPFRs and oxidative potential and can be also used to formulate the majors to control EPFRs and OP emissions, suggest the need for further studies on the secondary processing of EPFRs and OP during the lockdown period in Xi'an. .The COVID-19 lockdown had a significant impact on both social and economic aspects. The city lockdown, however, had a positive impact on the environment and improved air quality, however, no significant health benefits were observed in Xi'an, China.

Enhanced adsorption and degradation of antibiotics by doping corncob biochar/PMS with heteroatoms at different preparation temperatures: Mechanism, pathway, and relative contribution of reactive oxygen species

Antibiotics in the water environment pose harm to animals, plants, and humans. In this study, biochar doped with sulfur (S), nitrogen (N), and NS was used to adsorb and activate peroxymonosulfate (PMS) to degrade the antibiotics chlortetracycline, ofloxacin, and sulfadiazine in an aqueous solution. The adsorption capacity of the biochar doped with single atoms increased significantly, and the maximum saturated adsorption capacities of undoped, N-doped, S-doped, and NS-doped biochar were 40.7, 85.5, 63.3, and 40.7 mg/g, respectively. The increase in specific surface area and the number of functional groups was the main cause for the increase in the adsorption capacity of heteroatom-doped biochar. The antibiotic degradation process involved the use of biochar to activate PMS and produce reactive oxygen species (ROS) for complete removal. The concentration of environmentally persistent free radicals (EPFRs) increased in response to heteroatom-doped biochar, and the type of EPFRs changed, which enhanced the ability of biochar to degrade antibiotics. At the 500 °C preparation temperature, the degradation rates of antibiotics by the undoped, N-doped, S-doped, and NS-doped biochar were 73.83%, 84.32%, 79.60%, and 74.10%, respectively, whereas the degradation rates at 900 °C were 82.38%, 93.78%, 91.11%, and 81.55%, respectively. The sulfate radical was produced during the activation process and made the largest relative ROS contribution to the increased adsorption capacity, followed by singlet oxygen, hydroxyl radical, and superoxide radical. Recycling experiments confirmed that the heteroatom-doped biochar was highly reusable and that the removal rates of N-doped biochar and S-doped biochar were high (81.94% and 78.06%, respectively).

Effect of controlled temperature and biomass addition on the formed environmental persistent free radicals (EPFRs) in sewage sludge-based biochar from pyrolysis treatment

Sludge-based biochar derived from pyrolysis treatment is often utilized into soil agricultural fertilizer and soil amendment. While recent studies found that a new class of emerging environmental pollutant, environmental persistent free radicals (EPFRs) could be produced in combustion-based particles and airborne particulate matter. This study was aimed to determine if similar radicals were present in biochar derived from the pyrolyzed organic solid waste. The formation of EPFRs in sludge-based biochar during the pyrolysis treatment were in detailed characterized. EPFRs in biochar derived from sewage sludge pyrolysis at 200–600 ℃ and with various biomass addition were identified by using Electron paramagnetic resonance spectrometer. Three types of EPFRs were mainly spotted in the obtained biochar, including oxygen-centered, carbon-centered and F-centered radicals. Results revealed that the spin concentration of EPFRs decreased with temperature, and an increasing pyrolysis temperature could inhibit the formation of EPFRs. Lower pyrolysis temperature (＜400 ℃) favored the production of carbon-centered radicals, whereas higher temperature (＞400 ℃) mainly produced oxygen-centered radicals. Adding biomass also significantly affected the spin concentration and types of EPFRs. The spin concentration of EPFRs reached the highest value when adding 50% of biomass. The g-values of EPFRs in biochar were all less than 2.0030, indicating that carbon-centered and F-centered free radicals had occupied the dominance. In addition, the determination on the half-lives of EPFRs indicated that carbon-centered EPFRs were almost transformed to oxygen-centered EPFRs with storage time increased. The oxygen-centered free radicals became the dominant type of EPFRs after 100 days and even 200 days storage. The obtained findings imply the ecotoxicity of sludge-based biochar and give in-depth insight on the formation EPFRs, thus guiding the innocuous utilization of sludge.

Free radicals accelerate in situ ageing of microplastics during sludge composting

Composting is the last “barrier” for microplastics (MPs) in the entry of organic solid wastes into the environment. The transformation of MPs is thought to be mainly driven by microorganisms during composting, whereas the contribution of abiotic processes that involve free radicals is often overlooked. Herein, we provide initial evidence for the generation of free radicals during sludge composting, including environmental persistent free radicals and reactive oxygen species, which accelerate the oxidative degradation of MPs. The ·OH yield of composting fluctuated greatly from 23.03 to 277.18 μmol/kg during composting, which was closely related to the dynamic changes in Fe(II) (R2 = 0.926). Analyses of the composted MPs physicochemical properties indicated that MPs were aged gradually with molecular weights decrease from 18% to 27% and carbonyl index value increase from 0.23 to 0.52. Further investigation suggested that the microbially-mediated redox transformation of iron oxides could occur on the MPs surface accompanied by the production of abundant free radicals, thereby leading to the damage of MPs during composting. These results reveal the critical role of free radicals in MPs ageing under oxic/anoxic alternation conditions of composting and provide new insights into the bio-chemical mechanism of contaminant removal or transformation during sludge composting.

Effect of pyrolysis temperature on the activated permonosulfate degradation of antibiotics in nitrogen and sulfur-doping biochar: Key role of environmentally persistent free radicals

Because of the increasingly widespread contamination of antibiotics, the preparation of biochar by heteroatom doping to further improve the catalytic degradation efficiency of antibiotics has become a major focus of research. In this study, N-doped (NBC), S-doped (SBC), and NS-doped (NSBC) moso bamboo biochar were obtained at preparation temperatures of 300–700 °C. The concentration of environmentally persistent free radicals (EPFRs) in all biochars peaked when the preparation temperature was 500 °C: 2.45 × 1019 spins·g−1 (BC), 9.23 × 1019 spins·g−1 (NBC), 6.10 × 1019 spins·g−1 (SBC), and 4.36 × 1019 spins·g−1 (NSBC). After heteroatom doping, EPFR species were more abundant, and the distribution of three types of EPFRs (oxygen-centered (g > 2.0040), carbon-centered (g < 2.0030), and carbon-centered radicals with oxygen atom free radicals (2.0030 < g < 2.0040) varied with the preparation temperature. In the process of antibiotic degradation, both NBC and SBC increased the degradation rate of antibiotics, whereas NSBC reduced the degradation rate. Compared with the degradation rate of antibiotics of biochar (79.86%), the degradation rate of antibiotics by NBC, SBC, and NSBC via PMS activation was 92.23%, 88.86%, and 70.97% on average in 30 min, respectively. The greatest contributors to the catalytic degradation were SO4•-, followed by 1O2, •OH, and O2•-. EPFRs and 1O2 might be the main contributors to the free radical and non-free radical pathways. The enhancement of EPFRs following the N doping or S doping of biochar is the key factor underlying PMS activation. Therefore, changes in the structure of biochar can better activate PMS to produce reactive oxygen species-degrading antibiotics. The mineralization rate of antibiotics by BC, NBC, SBC, and NSBC was 42.12%, 47.06%, 44.99%, and 39.01%, respectively. This means that a small portion of the antibiotics was completely decomposed into CO2, H2O, and inorganic substances after degradation. Cyclic experiments showed that heteroatom-doped biochar had higher reusability, and the degradation rate decreased less than 15%.

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.