Chemotaxis-mediated degradation of PAHs and heterocyclic PAHs under low-temperature stress by Pseudomonas fluorescens S01: Insights into the mechanisms of biodegradation and cold adaptation

As wellknown persistent contaminants, polycyclic aromatic hydrocarbons (PAHs) and heterocyclic polyaromatic hydrocarbons (Heterocyclic PAHs)'s fates in cryogenic environments are remains uncertain. Herein, strain S01 was identified as Pseudomonas fluorescens, a novel bacterium tolerant to low temperature and capable of degrading PAHs and heterocyclic PAHs. Strain S01 exhibited growth at 5-40 ℃ and degradation rate of mixed PAHs and heterocyclic PAHs reached 52% under low-temperature. Through comprehensive metabolomic, genomic, and transcriptomic analyses, we reconstructed the biodegradation pathway for PAHs and heterocyclic PAHs in S01 while investigating its response to low temperature. Further experiments involving deletion and replacement of methyl-accepting chemotaxis protein (MCP) confirmed its crucial role in enabling strain S01's adaptation to dual stress of low temperature and pollutants. Additionally, our analysis revealed that MCP was upregulated under cold stress which enhanced strain S01's motility capabilities leading to increased biofilm formation. The establishment of biofilm promoted preservation of distinct cellular membrane stability, thereby enhancing energy metabolism. Consequently, this led to heightened efficiency in pollutant degradation and improved cold resistance capabilities. Our findings provide a comprehensive understanding of the environmental fate of both PAHs and heterocyclic PAHs under low-temperature conditions while also shedding light on cold adaptation mechanism employed by strain S01.

Functionalized Phenanthrene Imide-Based Polymers for n-Type Organic Thin-Film Transistors

High-performing n-type polymers are crucial for the advance of organic electronics field, however strong electron-deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide-functionalized polycyclic aromatic hydrocarbons (PAHs) with extended π-conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high-performance n-type polymers. Among the PAHs, phenanthrene (PhA) features a well-delocalized aromatic π-system with multiple modifiable active sites . However, the PhA-based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhAs, CPOI and CPCNI, by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA. Notably, the dicyanomethylene-modified CPCNI exhibits a well stabilized LUMO energy level (-3.84 eV), attributed to the synergetic inductive effect from imide and cyano groups. Subsequently, based on CPOI and CPCNI, two polymers PCPOI-Tz and PCPCNI-Tz were developed. Applied to organic thin-film transistors, owing to the strong electron-deficiency of CPCNI, polymer PCPCNI-Tz shows an improved electron mobility and largely decreased threshold voltage compared with PCPOI-Tz. This work affords two structurally novel electron-deficient building blocks and highlights the effectiveness of dual functionalization of PhAs with strong electron-withdrawing groups for devising n-type polymers.

Guest-Shuttling in a Nanosized Metallobox

An iridium-conjoined long and narrow metallorectangle was obtained by combining a quinoxalinophenanthrophenazine-connected Janus-di-imidazolylidene ligand and pyrazine. The size and shape of this assembly together with the fused polyaromatic nature of its panels provides it with properties that are uncommon for other metallosupramolecular assemblies. For example, this nanosized 'slit-like' metallobox is able show very large binding affinities with planar organic molecules in such a way, that the cavity is asymmetrically occupied by the guest molecule. This unsymmetrical conformation leads to the existence of a large amplitude motion of these guests, which slide between the two sides of the cavity of the host, thus constituting rare examples of molecular shuttles.

Precise Regulation of Multiple Resonance Distribution Regions of a B,N-Embedded Polycyclic Aromatic Hydrocarbon to Customize Its BT2020 Green Emission

Recently, boron (B)/nitrogen (N)-embedded polycyclic aromatic hydrocarbons (PAHs), characterized by multiple resonances (MR), have attracted significant attention owing to their remarkable features of efficient narrowband emissions with small full width at half maxima (FWHMs). However, developing ultra-narrowband pure-green emitters that comply with the Broadcast Service Television 2020 (BT2020) standard remains challenging. Precise regulation of the MR distribution regions allows simultaneously achieving the emission maximum, FWHM value, and spectral shape that satisfy the BT2020 standard. The proof-of-concept molecule TPABO-DICz exhibited ultrapure green emission with a dominant peak at 515 nm, an extremely small FWHM of 17 nm, and Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.76). The corresponding bottom-emitting organic light-emitting diode (OLED) exhibited a remarkably high CIEy value (0.74) and maximum external quantum efficiency (25.8 %). Notably, the top-emitting OLED achieved nearly BT2020 green color (CIE: 0.14, 0.79) and exhibited a state-of-the-art maximum current efficiency of 226.4 cd A-1 , thus fully confirming the effectiveness of the above strategy.

Designing Organic π-Conjugated Molecules for Crystalline Solid Solutions: Adamantane-Substituted Naphthalenes

We showcase herein organic crystalline solid solutions (CSSs) based on the simplest polycyclic aromatic hydrocarbon (PAH) scaffold, naphthalene, stabilized by dispersion forces induced by adamantane substitution. High thermal stability of the host and guest molecules synthesized by cross-coupling of dibromonaphthalene derivatives and 4-(1-adamantyl)phenyl boronic ester enabled formation of crystals by sublimation. We could generate binary monocrystalline solid solution systems proven by X-ray crystallography, the first system of designed CSSs stabilized exclusively via dispersion forces with structural evidence. These observations are additionally supported by lattice energy calculations and spectroscopic examinations. For the generation of CSSs, it is of utmost importance that the host and guest molecules have similar lattice energies and spatial compatibility. We anticipate that the thermostable organic CSS design demonstrated herein would be beneficial for functional materials and further investigation towards materials with unique properties.

Occupational exposures of firefighting and urinary tract cancer risk among men in the Norwegian Fire Departments Cohort

OBJECTIVES

Increased risks of bladder cancer and mesothelioma were the strongest evidence for the recent reclassification of firefighting as carcinogenic (Group 1) by the International Agency for Research on Cancer. Our study aim was to develop indicators for specific firefighting exposures and examine associations with urinary tract cancer (UTC), including bladder cancer.

METHODS

We developed indicators for exposure from employment at a fire department or in firefighting jobs, to fire and smoke, and to diesel exhaust for men in the Norwegian Fire Departments Cohort (n=4250). Incident UTC cases were obtained from the Cancer Registry of Norway (1960-2021). Poisson regression was used to estimate incidence rate ratios (IRR) with cumulative exposures grouped into tertiles (reference: lowest exposed tertile) with 0-year, 10-year and 15-year lagging of exposures.

RESULTS

During 125 090 person-years of follow-up, there were 76 cases of UTC. IRRs were mostly non-significantly increased in the middle tertile and at or below 1 in the highest tertile for total duration of employment, number of fires attended and fire exposure score with and without lags. In the middle tertile for diesel exhaust exposure, UTC risk was elevated over twofold with 10-year (IRR 2.27, 95% CI 1.22 to 4.20) and 15- year (2.21, 1.18 to 4.16) lags, and near 1 in the highest tertile. Findings for bladder cancer were similar to those for UTC.

CONCLUSIONS

Dose-response associations between the exposure indicators and UTC were not observed. Future studies using the indicators with more cases are needed.

Design Strategies for Diradical Boron/Nitrogen Doped Carbon-Based Materials

New heterocyclic diradicaloids based on boron and nitrogen-doped polycyclic systems with open-shell ground-states are obtained via concomitant structural and quinoidal extensions, thus allowing to merge the best of both design strategies. A combination of experimental characterization and theoretical calculations have helped disclose their electronic structure, as well as rationalize their associated magnetic and photophysical properties, spanning the chemical space of available molecular templates for cutting-edge applications in organic electronics and spintronics.

Exposure to Hazardous Substances and Their Health Effects Among Residents Living Near Three Industrial Waste Incinerators in Korea

BACKGROUND

This study aimed to evaluate exposure to various hazardous substances emitted by incineration facilities and their likely effect on the health for residents of Bugi-myeon, Cheongju, Korea, which has three incineration facilities.

METHODS

Heavy metals, polycyclic aromatic hydrocarbons (PAHs), and dioxin concentrations in the air and soil of exposed and control areas were measured. Moreover, the exposure levels to harmful substances and its effects on health were investigated in 1,124 exposed and 232 control adults.

RESULTS

PAHs and dioxin concentrations in the air in the exposed area were significantly higher than in the control area. Urinary cadmium and PAHs metabolite concentrations were significantly higher in the exposed group than in the control group. The exposure group also had a higher prevalence of depression and self-reported allergic symptoms than the control group.

CONCLUSION

The possibility of residents in Bugi-myeon being exposed to hazardous substances at incineration facilities cannot be ruled out. To prevent them from further exposure to hazardous substances, it is necessary to prohibit the expansion of additional incineration facilities in this area and to implement continuous monitoring projects for residents.

Circumpentacene with Open-Shell Singlet Diradical Character

Circumacenes (CAs) are a distinctive type of benzenoid polycyclic aromatic hydrocarbons where an acene unit is completely enclosed by a layer of outer fused benzene rings. Despite their unique structures, the synthesis of CAs is challenging, and until recently, the largest CA molecule synthesized was circumanthracene. In this study, we report the successful synthesis of an extended circumpentacene derivative 1, which represents the largest CA molecule synthesized to date. Its structure was confirmed by X-ray crystallographic analysis and its electronic properties were systematically investigated by both experiments and theoretical calculations. It shows a unique open-shell diradical character due to the existence of extended zigzag edges, with a moderate diradical character index (y0 =39.7 %) and a small singlet-triplet energy gap (ΔES-T =-4.47 kcal/mol). It exhibits a dominant local aromatic character with π-electrons delocalized in the individual aromatic sextet rings. It has a small HOMO-LUMO energy gap and displays amphoteric redox behavior. The electronic structures of its dication and dianion can be considered as doubly charged structures in which two coronene units are fused with a central aromatic benzene ring. This study provides a new route toward stable multizigzag-edged graphene-like molecules with open-shell di/polyradical character.

Polycyclic Aromatic Hydrocarbon-based Soft Materials: Applications in Fluorescent Detection, Gelation, AIEE and Mechanochromism

The present review discusses selected compounds based on Polycyclic Aromatic Hydrocarbons (PAHs); mainly those containing naphthalene, anthracene, fluorene, pyrene, triphenylene and perylene rings. The focus has been placed to highlight both properties and applications of such PAH-containing compounds in gelation, aggregation-induced enhanced emission (AIEE) and mechanochromism as well as in fluorescence sensing of assorted analytes.

Changes in metabolic profiles of amphipods Allorchestes compressa after acute exposures to copper, pyrene, and their mixtures

Amphipods are ideal indicators for biomonitoring and ecotoxicological studies of environmental contaminants because they are extensively distributed in aquatic environments, are easy to collect and are important in nutrient cycling. Marine amphipods (Allorchestes compressa) were exposed to two concentrations of copper and pyrene, and their mixtures, for 24 and 48 h. Changes in polar metabolites were assessed using Gas Chromatography Mass Spectrometry (GC-MS)-based untargeted metabolomics. Generally, limited metabolite changes were observed for copper and pyrene single exposures (eight and two significant metabolites, respectively), while 28 metabolites had changed following exposures to mixtures. Furthermore, changes were mainly observed after 24 h but had seemingly returned to control levels after 48 h. Multiple types of metabolites were affected including amino acids, Tricarboxylic acid (TCA) cycle intermediates, sugars, fatty acids, and hormones. This study highlights the sensitivity of metabolomics in assessing the impacts of low concentrations of chemicals compared to traditional ecotoxicological endpoints.

Synthesis of a π-Extended Double [9]Helicene

Double helicenes are appealing chiral frameworks. Their π-extension is desirable to achieve (chir)optical response in the visible and near-infrared (NIR) region, but access to higher double [n]helicenes (n≥8) has remained challenging. Herein, we report an unprecedented π-extended double [9]helicene (D9H), unambiguously revealing its structure by single-crystal X-ray diffraction. D9H shows remarkable NIR emission from 750 to 1100 nm with a high photoluminescence quantum yield of 18 %. In addition, optically pure D9H exhibits panchromatic circular dichroism with a notable dissymmetry factor (g_CD ) of 0.019 at 590 nm, which is among the highest in the visible region for reported helicenes.

Unconventional Pathway in the Gas-Phase Synthesis of 9H-Fluorene (C13 H10 ) via the Radical-Radical Reaction of Benzyl (C7 H7 ) with Phenyl (C6 H5 )

The simplest polycyclic aromatic hydrocarbon (PAH) carrying a five-membered ring-9H-fluorene (C₁₃ H₁₀ )-is produced isomer-specifically in the gas phase by reacting benzyl (C₇ H₇ ⋅) with phenyl (C₆ H₅ ⋅) radicals in a pyrolytic reactor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenylmethane and unexpected 1-(6-methylenecyclohexa-2,4-dienyl)benzene intermediates (C₁₃ H₁₂ ) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical-radical reactions are initiated through recombination at their radical centers. The structure of 9H-fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.

Exposure to Polycyclic Aromatic Hydrocarbons and adverse reproductive outcomes in women: current status and future perspectives

OBJECTIVES

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous, toxic environmental chemicals that can cause adverse reproductive health effects. The objectives of this mini-review are to highlight the adverse reproductive outcomes due to PAH exposure with the main focus on polycystic ovary syndrome (PCOS) and premature ovarian failure (POF) and to provide perspectives on future research needs.

CONTENT

We reviewed studies that have reported the adverse reproductive outcomes associated with PAHs exposures in women through a comprehensive search of bibliographic databases and gray literature sources. In addition, potentially modifiable sources of exposure to PAHs and associated reproductive outcomes were also investigated.

SUMMARY

A total of 232 papers were retrieved through a comprehensive search of bibliographic databases, out of which three studies met the eligibility criteria and were included in the review. Results showed that exposure to PAHs is associated with adverse reproductive outcomes defined as PCOS, POF, and reproductive hormone imbalance. Sources of PAH exposure associated with adverse reproductive outcomes include active and passive tobacco smoking, specific cooking methods, and pesticides.

OUTLOOK

Future studies are warranted to examine the mechanisms by which PAHs result in adverse reproductive endpoints in women. Further, environmental exposures that are potentially modifiable such as exposure to tobacco smoke, may contribute to PAH exposure, and these exposures should be targeted in future policies and interventions.

Doubling the Length of the Longest Pyrene-Pyrazinoquinoxaline Molecular Nanoribbons

Molecular nanoribbons are a class of atomically‐precise nanomaterials for a broad range of applications. An iterative approach that allows doubling the length of the longest pyrene‐pyrazinoquinoxaline molecular nanoribbons is described. The largest nanoribbon obtained through this approach—with a 60 linearly‐fused ring backbone (14.9 nm) and a 324‐atoms core (C₂₇₆N₄₈)—shows an extremely high molar absorptivity (values up to 1 198 074 M⁻¹ cm⁻¹) that also endows it with a high molar fluorescence brightness (8700 M⁻¹ cm⁻¹).

Traffic-related air pollution, biomarkers of metabolic dysfunction, oxidative stress, and CC16 in children

BACKGROUND

Previous research has revealed links between air pollution exposure and metabolic syndrome in adults; however, these associations are less explored in children.

OBJECTIVE

This study aims to investigate the association between traffic-related air pollutants (TRAP) and biomarkers of metabolic dysregulation, oxidative stress, and lung epithelial damage in children.

METHODS

We conducted cross-sectional analyses in a sample of predominantly Latinx, low-income children (n = 218) to examine associations between air pollutants (nitrogen dioxide (NO₂), nitrogen oxides (NO_x), elemental carbon, polycyclic aromatic hydrocarbons, carbon monoxide (CO), fine particulates (PM_2.5)) and biomarkers of metabolic function (high-density lipoprotein (HDL), hemoglobin A1c (HbA1c), oxidative stress (8-isoprostane), and lung epithelial damage (club cell protein 16 (CC16)).

RESULTS

HDL cholesterol showed an inverse association with NO₂ and NO_x, with the strongest relationship between HDL and 3-month exposure to NO₂ (-15.4 mg/dL per IQR increase in 3-month NO₂, 95% CI = -27.4, -3.4). 8-isoprostane showed a consistent pattern of increasing values with 1-day and 1-week exposure across all pollutants. Non-significant increases in % HbA1c were found during 1-month time frames and decreasing CC16 in 3-month exposure time frames.

CONCLUSION

Our results suggest that TRAP is significantly associated with decreased HDL cholesterol in longer-term time frames and elevated 8-isoprostane in shorter-term time frames. TRAP could have the potential to influence lifelong metabolic patterns, through metabolic effects in childhood.

Fusion of Multi-Resonance Fragment with Conventional Polycyclic Aromatic Hydrocarbon for Nearly BT.2020 Green Emission

Herein, we report a general strategy for achieving ultra-pure green emissions by suppressing the shoulder peaks in the emission spectra of conventional polycyclic aromatic hydrocarbons (PAHs). Through precise synthetic fusion of multi-resonance (MR) fragments with conventional PAH, extended π-conjugation lengths, increased molecular rigidity, and reduced vibrational frequency could be simultaneously realized. The proof-of-concept emitters exhibited ultra-pure green emissions with dominant peaks at ca. 521 nm, photoluminescence quantum yields that are greater than 99 %, a small full-width-at-half-maximum of 23 nm, and CIE coordinates of (0.16, 0.77). The bottom-emitting organic light-emitting diode (OLED) exhibited a record-high CIEy value of 0.74 and a high maximum external quantum efficiency of 30.5 %. The top-emitting OLED not only achieved a BT.2020 green color (CIE: 0.17, 0.78) for the first time but also showed superior performance among all green OLED devices, with a current efficiency of 220 cd A^- .

Azulene-Embedded [n]Helicenes (n=5, 6 and 7)

Azulene is a non-benzenoid aromatic building block with unique chemical structure and physicochemical properties. By using the "bottom-up" synthetic strategy, we synthesized three azulene-embedded [n]helicenes ([n]AzHs, n=5, 6 and 7), in which one terminal azulene subunit was fused with n-2 benzene rings. P- and M-enantiomers were observed in the packing diagrams of [5]-, and [6]AzHs. However, P- and M-[7]AzHs could be isolated by recrystallization of the racemic mixture. These [n]AzHs were endowed with new properties through the azulene moiety such as low-lying first electric state (S₁ ), small optical energy gap and anti-Kasha emission. [6]-, and [7]AzHs exhibit strong chiroptical responses with high absorption dissymmetry factor (g_abs ) maxima of about 0.02, which is among the highest |g_abs | values of helicenes in the visible range. These azulene-embedded [n]helicenes contribute to the non-benzenoid helicene library and allow the structure-property relationships to be better understood.

Modular Nitrogen-Doped Concave Polycyclic Aromatic Hydrocarbons for High-Performance Organic Light-Emitting Diodes with Tunable Emission Mechanisms

Although bowl‐shaped N‐pyrrolic polycyclic aromatic hydrocarbons (PAHs) can achieve excellent electron‐donating ability, their application for optoelectronics is hampered by typically low photoluminescence quantum yields (PLQYs). To address this issue, we report the synthesis and characterization of a series of curved and fully conjugated nitrogen‐doped PAHs. Through structural modifications to the electron‐accepting moiety, we are able to switch the mechanism of luminescence between thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP), and to tune the overall PLQY in the range from 9 % to 86 %. As a proof of concept, we constructed solid‐state organic light‐emitting diode (OLED) devices, which has not been explored to date in the context of concave N‐doped systems being TADF/RTP emitters. The best‐performing dye, possessing a peripheral trifluoromethyl group adjacent to the phenazine acceptor, exhibits yellow to orange emission with a maximum external quantum efficiency (EQE) of 12 %, which is the highest EQE in a curved D‐A embedded N‐PAH to date.

The relationship between polycyclic aromatic hydrocarbons exposure and serum klotho among adult population

Background

Klotho is an important factor involving aging process. Recently, polycyclic aromatic hydrocarbons (PAHs) exposure was reported to have adverse impact on DNA methylation associated with aging. The aim of the current study was to determine the relationship between serum klotho and PAHs exposure in an adult population.

Methods

A total of 2597 participants obtained from NHANES 2015–2016 were included in this cross-sectional study. Serum klotho levels were analyzed by enzyme-linked immunosorbent assay (ELISA). PAHs exposure was estimated by urinary sample using liquid chromatography-tandem mass spectrometry. The relationship between serum klotho and exposure to PAHS was analyzed by a multivariable linear regression model.

Results

2-napthol and 3-fluorene were significantly associated with decreased klotho. After fully adjusting pertinent variables, PAH exposure was significantly associated with decreased klotho, particularly in men.

Conclusion

In the present study we highlighted the significant association between PAHs exposure and serum klotho levels. The importance of environmental effect on aging process and age-related disorders should be paid more attention and clinical intervention is necessary.

Multicompartmental analysis of POPs and PAHs in Concepciόn Bay, central Chile: Part I - Levels and patterns after the 2010 tsunami

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) were determined in abiotic samples from Concepción Bay in Central Chile. Samples were soxhlet extracted and injected in gas chromatography-mass spectrometry (GCMS). Polybrominated diphenyl ethers (PBDEs) showed the highest levels in air (3-1100 pg m^-3), in water (2-64 pg L^-1), in sediment, and soil (1-78 ng g^-1 (dw)). PAHs were also high in the air (1-6 ng m^-3), in water (1-7 ng L^-1), in sediment (90-300 ng g^-1 (dw)), and in soil (15-2300 ng g^-1 (dw)). The polychlorinated biphenyls (PCBs) and chlorinated pesticides were generally low and did not show clear trends along the water column, with exception of PAHs. New data are presented in this work to assess the health status of a relevant coastal area in central Chile.

Anharmonic Infrared Spectra of Thermally Excited Pyrene (C16H10): A Combined View of DFT-Based GVPT2 with AnharmonicCaOs, and Approximate DFT Molecular dynamics with DemonNano

The study of the Aromatic Infrared Bands (AIBs) in astronomical environments has opened interesting spectroscopic questions on the effect of anharmonicity on the infrared (IR) spectrum of hot polycyclic aromatic hydrocarbons (PAHs) and related species in isolated conditions. The forthcoming James Webb Space Telescope will unveil unprecedented spatial and spectral details in the AIB spectrum; significant advancement is thus necessary now to model the infrared emission of PAHs, their presumed carriers, with enough detail to exploit the information content of the AIBs. This requires including anharmonicity in such models, and to do so systematically for all species included, requiring a difficult compromise between accuracy and efficiency. We performed a benchmark study to compare the performances of two methods in calculating anharmonic spectra, comparing them to available experimental data. One is a full quantum method, AnharmoniCaOs, relying on an ab initio potential, and the other relies on Molecular Dynamics simulations using a Density Functional based Tight Binding potential. The first one is found to be very accurate and detailed, but it becomes computationally very expensive for increasing temperature; the second is faster and can be used for arbitrarily high temperatures, but is less accurate. Still, its results can be used to model the evolution with temperature of isolated bands. We propose a new recipe to model anharmonic AIB emission using minimal assumptions on the general behaviour of band positions and widths with temperature, which can be defined by a small number of empirical parameters. Modelling accuracy will depend critically on these empirical parameters, allowing for an incremental improvement in model results, as better estimates become gradually available.

Advanced Gel Permeation Chromatography system with increased loading capacity: Polycyclic aromatic hydrocarbons detection in olive oil as a case of study

Gel permeation chromatography (GPC) is herein used as size exclusion clean-up technique for highly sensitive and straightforward detection of Polycyclic Aromatic Hydrocarbons (PAHs) in olive oil samples. An advanced chromatographic system has been developed to isolate a series of PAHs with cancerogenic potential, including PAH4 (benzo(a)pyrene BaP, benzo(a)anthracene BaA, benzo(b)fluoranthene BbF and chrysene Chry) reported in the European Regulation. The system avails of two glass chromatographic columns and a switching valve, that allow removal of interfering analytes in olive oil without resorting to any preliminary extraction process. A seven-fold increase of the loaded sample amount versus conventional chromatographic systems (1 g vs 0.150 g) has been pursued, as well as improved PAHs detection and quantification limits (LOD-LOQ for PAH4: 0.21-0.70 ng/g for BaA, 0.26-0.86 ng/g for Chry, 0.23-0.76 ng/g for BbF, 0.32-1.06 ng/g for BaP), in accordance with the continuous need of more and more reducing these limits in food analysis by the European Regulation. The protocol developed represents a highly innovative and efficient analytical method for organic pollutants in complex biological matrices as olive oil, that can have huge impact on technology for PAHs detection in food samples, being suitable for both industrial and small-scale laboratories.

Synthesis of glutathione as a central aspect of PAH toxicity in liver cells: A comparison between phenanthrene, Benzo[b]Fluoranthene and their mixtures

Polycyclic Aromatic Hydrocarbons (PAH) are a class of organic pollutants normally found as mixtures with effects often hard to predict, which poses a major challenge for risk assessment. In this study, we address the effects of Phenanthrene (Phe), benzo[b]fluoranthene (B[b]F) and their mixtures (2 Phe:1 B[b]F; 1 Phe: 1 B[b]F; 1 Phe: 2 B[b]F) over glutathione (GSH) synthesis and function in HepG2 cells. We analyzed the effects on cellular viability, ROS production, glutathione (GSH) levels, protein-S-glutathionylation (PSSG), the activity of glutathione peroxidase (GPx), glutathione-S-transferases (GST) and glutathione reductase (GR). Transcript (mRNA) levels of glutathione synthesis enzymes - glutathione cysteine ligase catalytical (GCLC) and modifying (GCLM) sub-units and glutathione synthetase (GS) - and Nrf2 translocation to the nucleus were analyzed. Phe showed a higher cytotoxicity (IC₅₀ = 130 µM after 24 h) than B[b]F related to a higher ROS production (up-to 50% for Phe). In agreement, GSH levels were significantly increased (up-to 3-fold) by B[b]F and were accompanied by an increase in the levels of PSSG, which is a mechanism that protect proteins from oxidative damage. The upregulation of GSH was the consequence of Nrf2 signaling activation and increased levels of GCLC, GCLM and GS mRNA observed after exposure to B[b]F, but not during exposure to Phe. Most interestingly, all mixtures showed higher cytotoxicity than individual compounds, but intriguingly it was the 1 Phe: 1B[b]F mixture showing the highest cytotoxicity and ROS production. GSH levels were not significantly upregulated not even in the mixture enriched in B[b]F. These results point to the role of GSH as a central modulator of PAH toxicity and demonstrate the idiosyncratic behavior of PAH mixtures even when considering only two compounds in varying ratios.

Environment-Wide Association Study of CKD

BACKGROUND AND OBJECTIVES

Exposure to environmental chemicals has been recognized as one of the possible contributors to CKD. We aimed to identify environmental chemicals that are associated with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We analyzed the data obtained from a total of 46,748 adults who participated in the National Health and Nutrition Examination Survey (1999-2016). Associations of chemicals measured in urine or blood (n=262) with albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g), reduced eGFR (<60 ml/min per 1.73 m²), and a composite of albuminuria or reduced eGFR were tested and validated using the environment-wide association study approach.

RESULTS

Among 262 environmental chemicals, seven (3%) chemicals showed significant associations with increased risk of albuminuria, reduced eGFR, or the composite outcome. These chemicals included metals and other chemicals that have not previously been associated with CKD. Serum and urine cotinines, blood 2,5-dimethylfuran (a volatile organic compound), and blood cadmium were associated with albuminuria. Blood lead and cadmium were associated with reduced eGFR. Blood cadmium and lead and three volatile compounds (blood 2,5-dimethylfuran, blood furan, and urinary phenylglyoxylic acid) were associated with the composite outcome. A total of 23 chemicals, including serum perfluorooctanoic acid, seven urinary metals, three urinary arsenics, urinary nitrate and thiocyanate, three urinary polycyclic aromatic hydrocarbons, and seven volatile organic compounds, were associated with lower risks of one or more manifestations of CKD.

CONCLUSIONS

A number of chemicals were identified as potential risk factors for CKD among the general population.

Pollution and Sun Exposure: A Deleterious Synergy. Mechanisms and Opportunities for Skin Protection

BACKGROUND

Pollutants are diverse chemical entities, including gases such as ozone and particulate matter PM. PM contains toxic chemicals such as polycyclic aromatic hydrocarbons (PAHs). Some PAHs can induce strong oxidative stress under UVA exposure. Pollution aggravates some skin diseases such as atopy or eczema, but epidemiological data also pointed to a correlation with early occurrence of (photo)-aging markers.

OBJECTIVE

This paper aims at reviewing current literature dealing with dermatological effects of pollution, either on in vitro models or using in vivo approaches (including humans). It particularly focuses on the probable deleterious synergy between pollutants and sunlight.

RESULTS

An exhaustive analysis of literature suggests that skin may be impacted by external stress through oxidation of some of its surface components. However, pollutants detected in plasma may also be provided to deep skin by the circulation of the blood. Oxidative stress, inflammation and metabolic impairments are among the most probable mechanisms of pollution- derived dermatological hazards. Moreover these stresses should be amplified by the deleterious synergy between pollution and sunlight. Some experiments from our lab identified few PAHs inducing a huge toxic stress, at nanomolar concentrations, when exposed to long UVA wavelengths. Prevention strategies should thus combine surface protection (long UVA sunscreens, antioxidants) and enhanced skin tissue resistance through stimulation of the natural antioxidation/detoxification pathway Nrf2.

CONCLUSION

In people exposed to highly polluted environments, pollutants and sunlight may synergistically damage skin, requiring a specific protection.

Distribution patterns of organic pollutants and microbial processes in marine sediments across a gradient of anthropogenic impact

Marine sediments are part of the hydrological cycle and the ultimate storage compartment of land-derived organic matter, including pollutants. Since relevant microbially-driven processes occurring at benthic level may affect the quality of the overall aquatic system, the necessity for incorporating information about microbial communities functioning for ecosystem modelling is arising. The aim of this field study was to explore the links occurring between sediment contamination patterns by three selected class of organic pollutants (Polycyclic Aromatic Hydrocarbons, PAHs, Nonylphenols, NPs, Bisphenol A, BPA) and major microbial properties (Prokaryotic Biomass, PB; total living biomass, C-ATP; Prokaryotic C Production rate, PCP; Community Respiration rate, CR) across a gradient of anthropogenic pollution. Sediments were sampled from 34 sites selected along 700 km of the western coastline of the Adriatic Sea. Organic contamination was moderate (PAHs <830 ng g^-1; NPs <350  ng g^-1; BPA <38  ng g^-1) and decreased southward. The amount of PAHs-associated carbon (C-PAHs) increased significantly with sediment organic carbon (OC), along with microbial functional rates. The negative relation between PCP/CR ratio and OC indicated the shift toward oxidative processes in response to organic pollution and potential toxicity, estimated as Toxic Equivalents (TEQs). Our outcomes showed that sediment organic contamination and benthic microbial processes can be intimately linked, with potential repercussions on CO₂ emission rates and C-cycling within the detritus-based trophic web.

[The ecologization of the Papanicolaou stain in the diagnosis of cervical cancer]

BACKGROUND

Cervical cancer is the fourth most common cancer worldwide among women.

OBJECTIVE

To evaluate the implementation and efficiency of the Ecological Papanicolaou staining (Eco-Pap) in exfoliative cytology for the diagnosis of cervical cancer.

METHODS

A prospective, experimental, cross-sectional research was performed at the Hospital Nacional Docente Madre-Niño “San Bartolomé” during 2015. Three strategies for controlling toxic reagents were used: the use of progressive Harris haematoxylin, polychromatic cytoplasmic solution and direct mounting. Cellular details were analyzed by using the Quality Index Staining, the Bethesda system and the Quality Program for External Evaluation of Cytology.

RESULTS

We evaluated 72 901 cervical smears stained with Eco-Pap. The validation of Eco-Pap against the standard Papanicolaou staining had very good agreement (kappa = 0.89), showing a sensitivity and specificity of 88.3 and 98.7%, respectively (p < 0.05). The Eco-Pap had a high diagnostic yield and reduced environmental pollution caused by xylene (72 liters), hydrochloric acid and ammonia (each one with six liters), as well as mercury oxide.

CONCLUSIONS

The Eco-Pap is a new, efficient and innovative method which eliminates the use of toxic-carcinogenic reagents, generating ecological performance in the diagnosis of cervical cancer

Aerosol contributions at an urban background site in Eastern Mediterranean - Potential source regions of PAHs in PM10 mass

In this paper, two backward air mass trajectory-based models (Potential Source Contribution Function [PSCF] and Concentration Weighted Trajectory [CWT]) were combined, aiming to identify sources and factors defining the load of PM in the city of Limassol (Cyprus). The study also focused on the determination of atmospheric pathways enriching the aerosol phase of four carcinogenic Polycyclic Aromatic Hydrocarbons (PAHs): Benzo(a)pyrene (BaP), Benzo(a)anthracene (BaA), Benzo(b)fluoranthene (BbF) and Benzo(k)fluoranthene (BkF), in PM₁₀ mass. The analysis was performed on a 0.5°·0.5° resolution grid for the two-year period 2011-2012. During cold seasons, regional airflows triggered the accumulation of locally produced PM_2.5, while the impact of dust plumes originated from deserts in NE Africa, Syria and the Middle East, was apparent on PM_2.5 and principally on PM_COARSE levels. On the contrary, within warm seasons, weaker dust PM_COARSE contributions were detected in Limassol from areas in Egypt and Libya. Raised particulate-phase PAH concentrations in Limassol were clearly related to air parcels reaching Cyprus via continental areas. The use of outdated technologies for heating and transportation in Turkey and Syria, and fire events in central Turkey, are possible sources of exogenous PAHs throughout cold and warm period respectively. The influence of clean marine air masses dropped the levels of PAH compounds in all seasons.

Identification of new tetrahydroxylated metabolites of Polycyclic Aromatic Hydrocarbons in hair as biomarkers of exposure and signature of DNA adduct levels

The present study addresses the hypothesis that the concentration of tetrahydroxylated Polycylic Aromatic Hydrocarbons (tetra-OH-PAHs) in hair might be a useful biomarker of human exposure to PAHs, providing quantitative assessment of the internal dose, as well as information on the associated toxicity in relation to individual's specific metabolism. By means of animal models, this work aimed at identifying new tetra-OH-PAHs which can be released from the hydrolysis of DNA-adducts and can also be directly detected in biological matrices usually used in the field of biomonitoring such as hair and urine. Results obtained from a targeted gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) approach, demonstrated the presence of 8 tetrahydroxylated metabolites in DNA and 23 in hairs of rats exposed to mixtures of PAHs, which had never been analyzed before. Ten tetra-OH-PAHs were clearly characterized by using their analytical standards, corresponding to 4 parent PAHs (phenanthrene, chrysene, benz[a]anthracene and benzo[a]pyrene) whereas 13 tetra-OH-PAHs from 3 other parents (anthracene, fluoranthene and benz[k]fluoranthene) were detected but not yet characterized. No tetrahydroxylated metabolite has been clearly identified for naphthalene, fluorene, benzo[b]fluoranthene, benzo[g,h,i]perylene, or dibenzo[a,h]anthracene, which can all potentially form adducts. The relevance of tetra-OH-PAH analysis in hair as biomarkers of PAH exposure was evaluated in a dose-response study conducted on 64 rats (Long Evans females/n = 8 per groups) under repeated exposure (3 times per week) to a mixture of 16 PAHs at low doses (0.01-0.8 mg/kg) for 90 days. Most of the tetra-OH-PAHs targeted in the method were detected in the hairs of the rats, regardless of the dose of exposure. Significant linear relationships (R² ranging from 0.558 to 0.964, p < 0.001) were observed between the administered dose and the tetra-OH-PAH concentrations in the hairs for 20 out of the 23 metabolites. By widening the range of PAH metabolites used as biomarkers of exposure so as to include the analysis of PAH tetrahydroxylated forms (especially those exhibiting more than 5 aromatic rings), the present methodology will enable multi-exposure assessments which are more accurately representative of actual situations of exposure to PAHs.

Baseline evaluation of sediment contamination in the shallow coastal areas of Saudi Arabian Red Sea

Despite the growing recognition of the importance of water and sediment quality there is still limited information on contamination levels in many regions globally including the Red Sea. This study provides a comprehensive assessment of three classes of contaminants (Polycyclic Aromatic Hydrocarbons - PAH; metals; plastics) in coastal sediments along the Saudi Arabian Red Sea mainly collected using grabs. Background concentrations are provided for metals in the region. Concentrations of metals and PAH were generally low in comparison to international guidelines. A clear relationship between the concentration of metals and anthropogenic sources was not always apparent and dust and vegetation may be relevant players in the region. Microplastic items (mainly polyethylene) were abundant (reaching up to 1gm^-2 and 160piecesm^-2) and in general associated with areas of high human activity. This study provides critical information for future monitoring and the development of national policies within the Red Sea region.

Polycyclic Aromatic Hydrocarbons (PAHs) produced in the combustion of fatty acid alkyl esters from different feedstocks: Quantification, statistical analysis and mechanisms of formation

Polycyclic Aromatic Hydrocarbons (PAHs) are pollutants of concern due to their carcinogenic and mutagenic activity. Their emissions are mainly related with the combustion or pyrolysis of the organic matter, such as in fossil fuels combustion. It is important to characterize PAHs in the combustions of biofuels due to their increasing importance in the actual energetic setting. There is a lot of research focused in PAHs emission due to the combustion in diesel engines; but only few of them have analyzed the effect of raw material and type of alcohol used in the transesterification process. Different raw materials (i.e. animal fat, palm, rapeseed, linseed, peanut, coconut, and soybean oils) have been used for obtaining FAME and FAEE. A method for measuring PAHs generated during combustion in a bomb calorimeter has been developed. Combustion was made at different oxygen pressures and the samples were taken from the bomb after each combustion. Samples were extracted and the PAHs amounts formed during combustion were analyzed by GC-MS. This research shows the statistical relationships among the 16 PAHs of concern, biodiesel composition and oxygen pressure during combustion.

Benzo(a)pyrene in Europe: Ambient air concentrations, population exposure and health effects

This study estimated current benzo(a)pyrene (BaP) concentration levels, population exposure and potential health impacts of exposure to ambient air BaP in Europe. These estimates were done by combining the best available information from observations and chemical transport models through the use of spatial interpolation methods. Results show large exceedances of the European target value for BaP in 2012 over large areas, particularly in central-eastern Europe. Results also show large uncertainties in the concentration estimates in regions with a few or no measurement stations. The estimation of the population exposure to BaP concentrations and its health impacts was limited to 60% of the European population, covering only the modelled areas which met the data quality requirement for modelling of BaP concentrations set by the European directive 2004/107/EC. The population exposure estimate shows that 20% of the European population is exposed to BaP background ambient concentrations above the EU target value and only 7% live in areas with concentrations under the estimated acceptable risk level of 0.12 ng m(-3). This exposure leads to an estimated 370 lung cancer incidences per year, for the 60% of the European population included in the estimation. Emissions of BaP have increased in the last decade with the increase in emissions from household combustion of biomass. At the same time, climate mitigation policies are promoting the use of biomass burning for domestic heating. The current study shows that there is a need for more BaP measurements in areas of low measurement density, particularly where high concentrations are expected, e.g. in Romania, Bulgaria, and other Balkan states. Furthermore, this study shows that the health risk posed by PAH exposure calls for better coordination between air quality and climate mitigation policies in Europe.

The Influence of the Aromatic Character in the Gas Chromatography Elution Order: The Case of Polycyclic Aromatic Hydrocarbons

A link between the aromatic character of polycyclic aromatic hydrocarbons and gas chromatography elution order in columns with a polysiloxane backbone in the stationary phase is reported for the first time. The aromatic character was calculated using a method that combines the π-Sextet Rule and the Pauling Ring Bond Orders to allow the establishment of the location and migration of aromatic sextets in PAH structures. One GC column with a polysiloxane - like backbone (Rxi-PAH) and three GC columns with a polysiloxane backbone (DB-5, SE-52, and LC-50), were used for the analysis. According to the results of this study, within an isomer group, PAHs that contain a lower number of rings affected by the aromatic sextets tend to elute earlier than PAHs that contain a higher number of rings affected by the aromatic sextets. The PAHs that follow the calculated elution order are 88 % in the Rxi-PAH column, 88 % in the DB-5 column, 93 % in the SE-52 column, and 85% in the LC-50 column. It is expected that future analyses with other aromatic compounds in GC columns with a polysiloxane backbone in the stationary phase will follow a GC elution order that agrees with the aromatic character of the molecules.

Experimental design approach to the optimization of PAHs bioremediation from artificially contaminated soil: application of variables screening development

BACKGROUND

The effectiveness of bioremediation systems for PAH-contaminated soil may be constrained by physicochemical properties of contaminants and environmental factors. Information on what is the most effective factor in bioremediation process is essential in the decision of what stimulations can be taken to assist the biodegradation efficacy.

METHODS

In this study, four factors of surfactant (Tween 80), humic acid (HA), salinity and nutrients in a 2(4) full factorial design were screened in bioremediation of phenanthrene contaminated soil by using a consortium of bacteria.

RESULTS

Between the employed levels of the factors only salinity had not significant effect. Optimal concentrations of surfactant, HA and nutrient were obtained by a response surface design. For phenanthrene biodegradation, a central composite face centred design (CCFD) showed that nutrient, surfactant and HA concentrations had highly significant, significant and insignificant effects, respectively. The best conditions with 87.1% phenanthrene biodegradation were 150 mg HA/Kg soil, 12.68 μg/L surfactant, and nutrients as K2HPO4, 0.8; KH2PO4, 0.2 and KNO3, 1 g/L. A high similarity was between the model prediction and experimental results.

CONCLUSIONS

This study showed that nutrient with 81.27% efficiency could be considered as the most effective factor for practical implications of bioremediation process for PAHs contaminated soil cleanup strategies.

Bioaccumulation and oxidative damage in juvenile scallop Chlamys farreri exposed to benzo[a]pyrene, benzo[b]fluoranthene and chrysene

The study is aimed at investigating the bioaccumulation and oxidative damage of juvenile scallops (Chlamys farreri) exposed to three selected PAHs: benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF) and chrysene (CHR). For this purpose, a study was performed on juvenile scallops exposed to BaP (0.01, 0.2 and 4μg/L), BbF (0.02, 0.2 and 2μg/L) and CHR (0.2, 0.8 and 3.2μg/L) for 21 days. Accumulations of these three PAHs in soft parts of scallops, except the 0.01μg/L BaP group and the 0.02μg/L BbF group, showed obvious time and dose dependence, and CHR accumulation was higher when compared to BaP and BbF. Oxidative damage indicators, including lipid peroxidation (LPO), protein carbonyl (PC) and DNA strand breaks, were also measured in soft parts to assess effects of the selected PAHs. The results showed that the LPO levels, PC contents and DNA damage were induced significantly (P<0.05 or P<0.01), except in the low level groups of BaP and BbF, and different trends were detected with time of exposure. According to the correlation analysis results, PC content in soft parts showed a good correlation with the target contaminant and seemed to be proposed as a potential early indicator of BaP, BbF and CHR. In addition the sequence of toxicity is BaP>BbF>CHR, judging by the level of induction of oxidative damage at 0.2μg/L levels. The results of this research are expected to contribute to the establishment of a good biochemical index of exposure to PAHs in laboratory experiments, which can be further useful in field studies.

Toxicity evaluation and source apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) at three stations in Istanbul, Turkey

This paper focuses on the toxicity evaluation and source apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) in three monitoring stations in Istanbul, Turkey. A total of 326 airborne samples were collected and analyzed for 16 PAHs and Total Suspended Particles (TSP) for the period of September 2006-December 2007. The total average PAH concentrations were 100.7±61.3, 84.6±46.7 and 25.1±13.3 ng m(-3) and the TSP concentrations were 101.2±53.2, 152.3±99.1, 49.8±18.6 μg m(-3) for URB1, URB2 and RUR stations, respectively. Benzo(a)Pyren (BaP) toxic equivalency factors to PAH concentration values were calculated indicating that the health risk of BaP and DiBenz(a,h)Anthracene (markers of traffic emissions) have the highest contribution compared to all of the other species measured at the sampling sites. In order to determine PAH sources, two different source apportionment techniques were applied to the measurements; diagnostic ratios (DR) and Positive Matrix Factorization (PMF). The results of the two applications were compatible indicating the vehicle emissions - especially diesel engines - as the major source for urban stations.

Air Polycyclic Aromatic Hydrocarbons (PAHs) associated with PM2.5 in a North Cantabric coast urban environment

Health studies and more specifically epidemiological studies require an extended analysis of the physical and chemical characteristics of the environment in which are held. The aim of this study is to evaluate the concentration of six Polycyclic Aromatic Hydrocarbons (PAHs) in PM2.5 fraction of air in a peri-urban environment in the province of Gipuzkoa (Basque Country, Spain) where residential areas are surrounded by industrial activity. The six studied PAH are as follows: Fluoranthene, Benzo(b)fluoranthene, Benzo(k)fluoranthene, (Benzo(a)pyrene, Indene(123-cd)pyrene and Benzo(ghi)perylene. Our six-year study shows a decrease in PAH concentrations between 2006 and 2011, especially since 2008 due to the fall in industrial activity and related traffic. Overall, 801 data were obtained. Total PAH concentration ranged between 0.3 and 8.29ngm(-3) and Benzo(a)pyrene (BaP) from 0.05 to 0.88ngm(-3). The mean value for BaP in PM2.5 was 0.15ngm(-3) and the target value established by European legislation in PM10 was only exceeded in occasional days. Contribution percentages of each PAH in the monitoring sites were very similar, indicating common sources. The results of this study suggest that emission from industry play an important role although we also have to consider the contribution of traffic. PAH seasonal variations are similar as those reported in many previous studies. BaP and PAH concentration values in our region of study were in the range of other Spanish cities.

Pro-inflammatory effects and oxidative stress in lung macrophages and epithelial cells induced by ambient particulate matter

The objective of this study was to compare the toxicological effects of different source-related ambient PM10 samples in regard to their chemical composition. In this context we investigated airborne PM from different sites in Aachen, Germany. For the toxicological investigation human alveolar epithelial cells (A549) and murine macrophages (RAW264.7) were exposed from 0 to 96 h to increasing PM concentrations (0-100 μg/ml) followed by analyses of cell viability, pro-inflammatory and oxidative stress responses. The chemical analysis of these particles indicated the presence of 21 elements, water-soluble ions and PAHs. The toxicological investigations of the PM10 samples demonstrated a concentration- and time-dependent decrease in cell viability and an increase in pro-inflammatory and oxidative stress markers.

Structural basis of substrate conversion in a new aromatic peroxygenase: cytochrome P450 functionality with benefits

Aromatic peroxygenases (APOs) represent a unique oxidoreductase sub-subclass of heme proteins with peroxygenase and peroxidase activity and were thus recently assigned a distinct EC classification (EC 1.11.2.1). They catalyze, inter alia, oxyfunctionalization reactions of aromatic and aliphatic hydrocarbons with remarkable regio- and stereoselectivities. When compared with cytochrome P450, APOs appear to be the choice enzymes for oxyfunctionalizations in organic synthesis due to their independence from a cellular environment and their greater chemical versatility. Here, the first two crystal structures of a heavily glycosylated fungal aromatic peroxygenase (AaeAPO) are described. They reveal different pH-dependent ligand binding modes. We model the fitting of various substrates in AaeAPO, illustrating the way the enzyme oxygenates polycyclic aromatic hydrocarbons. Spatial restrictions by a phenylalanine pentad in the active-site environment govern substrate specificity in AaeAPO.

The effect of the argon carrier gas in the multiphoton dissociation-ionization of tetracene

The multiphoton dissociation-ionization of tetracene at 355 nm using 6.5 nanosecond laser pulses, with and without argon as a carrier gas (CG), has been studied and compared. Ion fragments were analyzed in a time-of-flight mass spectrometer and separated according to their mass-to-charge ratio (m/z). The results show that the dynamic of photodissociation at approximately 10(10) W cm(-2) intensities is strongly influenced by the CG. The suppression of fragmentation channels primarily those relating to the formation of the CH(m) (+) (m = 2, 4), C(2)H(4) (+) and C(5)H(4) (+2) ions. CH(5) (+) and CH(6) (+) were observed which have not been reported before in photodissociation tetracene experiments.