Polycyclic Aromatic Hydrocarbons In Samples Research Articles

Determination of 16 PAHs and 22 PCBs in honey samples originated from different region of Lebanon and used as environmental biomonitors sentinel

In order to assess the air quality in some Lebanese regions, a biomonitoring study based on honey as biomonitor candidate was conducted. For this, 18 samples of honey collected from four regions in Lebanon, were analyzed for their contamination by 16 polycyclic aromatic hydrocarbons (PAHs) and 22 polychlorinated biphenyls (PCBs). Samples were first extracted using a multi-residue extraction method based on the quick, easy, cheap, effective, rugged, and safe extraction method (QuEChERS) followed by a concentration step using Solid-phase microextraction (SPME) procedures. The extraction was then followed by chromatographic analysis by gas chromatography-ion-trap tandem mass spectrometry (GC-MS/MS). After PAHs samples assessment, different ratios of founded PAHs were calculated in order to estimate the sources of the pollution by these compounds. The obtained results showed that the four analyzed regions were contaminated with PAHs originated from both pyro and petro genic sources while none of them was found to be contaminated by any of the 22 assessed PCBs. The results of this study show that honey can be used as potential biomonitor candidate allowing the assessment of the pollution statement of a given environment.

Improvement of dispersive liquid‐liquid microextraction robustness by performing consecutive extractions: Determination of polycyclic aromatic hydrocarbons in Brazilian sugar cane spirits by GC‐MS

AbstractThis paper describes the development of a multiple dispersive liquid‐liquid microextraction method for the determination of fifteen polycyclic aromatic hydrocarbons in samples of Brazilian sugar cane spirit (known as cachaça) with separation and detection by GC‐MS. The results obtained with the multiple extraction approach were compared to those obtained with the conventional dispersive liquid‐liquid microextraction method using the same sample. Sample dilution and solvent volume were optimized using the response surface methodology. The coefficient of determination (R2) for the multiple dispersive liquid‐liquid microextraction method varied from 0.9939 to 0.9999. The limits of detection ranged from 0.06 to 1.5 μg L−1 and precision from 12 and 22%. The recovery values obtained with the proposed method ranged from 84 to 116%. The sum of the polycyclic aromatic hydrocarbons concentrations in six samples ranged from 0.65 to 12.2 μg L−1. Multiple dispersive liquid‐liquid microextraction was shown to be efficient in relation to compensating the matrix effects due to variations in the sample composition and the extraction parameters showed greater robustness compared to the conventional dispersive liquid‐liquid microextraction method, since it simulates an exhaustive extraction.

Association between cancer risk and polycyclic aromatic hydrocarbons' exposure in the ambient air of Ahvaz, southwest of Iran.

Nowadays, a large number of health endpoints such as disease rates, treatment costs, and death, by air pollutants, have been a serious health problem for humans. One of the most hazardous air pollutants, which is highly dangerous for human health, is polycyclic aromatic hydrocarbons (PAHs). The existence of the emission of industries' pollutants and seasonal variations are the primary agents affecting PAHs' concentration. The purposes of this study were to calculate the cancer risk and measure PAHs' exposure in the ambient air of Ahvaz, southwest of Iran, during 2017. Three distinct areas ((S1) industrial, (S2) high traffic, and (S3) residential) of Ahvaz metropolitan were selected. Omni sampler equipped with polytetrafluoroethylene (PTFE) filters were used for active sampling of PAHs. To detect the level of PAHs, gas chromatography with mass spectrometry (GC/MS) was used. Incremental lifetime cancer risk (ILCR) and lifetime average daily dose (LADD) were used to estimate the health risk caused by PAHs. The results showed that the residential and industrial areas had the lowest and highest level of PAHs. Moreover, the average levels of PAHs in industrial, high traffic, and residential areas were 8.44 ± 3.37, 7.11 ± 2.64, and 5.52 ± 1.63ngm-3, respectively. Furthermore, ILCR in autumn and winter was higher than EPA standard, 0.06307 and 0.04718, respectively. In addition, ILCR in different areas was significantly higher than standard. Research findings imply that the levels of exposure to PAHs can increase ILCR and risk of health endpoint. The cancer risk attributed to PAHs should be further investigated from the perspective of the public health in metropolitans.

Method for the simultaneous determination of monoaromatic and polycyclic aromatic hydrocarbons in industrial effluents using dispersive liquid-liquid microextraction with gas chromatography-mass spectrometry.

We present a new method for simultaneous determination of 22 monoaromatic and polycyclic aromatic hydrocarbons in postoxidative effluents from the production of petroleum bitumen using dispersive liquid-liquid microextraction coupled to gas chromatography and mass spectrometry. The eight extraction parameters including the type and volume of extraction and disperser solvent, pH, salting out effect, extraction, and centrifugation time were optimized. The low detection limit ranging from 0.36 to 28μg/L, limit of quantitation (1.1-84μg/L), good reproducibility, and wide linear ranges, as well as the recoveries ranging from 71.74 to 114.67% revealed that the new method allows the determination of aromatic hydrocarbons at low concentration levels in industrial effluents having a very complex composition. The developed method was applied to the determination of content of mono- and polycyclic aromatic hydrocarbons in samples of raw postoxidative effluents in which 15 compounds were identified at concentrations ranging from 1.21 to 1017.0μg/L as well as in effluents after chemical treatment.

Application of semipermeable membrane devices for long-term monitoring of polycyclic aromatic hydrocarbons at various stages of drinking water treatment

The primary goal of the presented study was the investigation of occurrence and concentration of sixteen selected polycyclic aromatic hydrocarbons in samples from various stages of water treatment and verification of the applicability of semi-permeable membrane devices in the monitoring of drinking water. Another objective was to verify if weather seasons affect the concentration and complexity of PAHs. For these purposes, semipermeable membrane devices were installed in a surface water treatment plant located in Lower Silesia (Poland). Samples were collected monthly over a period of one year. To determine the effect of water treatment on PAH concentrations, four sampling sites were selected: raw water input, a stream of water in the pipe just before ozonation, treated water output and water after passing through the distribution system. After each month of sampling, SPMDs were exchanged for fresh ones and prepared for instrumental analysis. Concentrations of polycyclic aromatic hydrocarbons were determined by high-performance liquid chromatography (HPLC). The presented study indicates that semipermeable membrane devices can be an effective tool for the analysis of drinking water, in which organic micropollutants occur at very low concentrations.

Metal-organic framework based in-syringe solid-phase extraction for the on-site sampling of polycyclic aromatic hydrocarbons from environmental water samples.

In-syringe solid-phase extraction is a promising sample pretreatment method for the on-site sampling of water samples because of its outstanding advantages of portability, simple operation, short extraction time, and low cost. In this work, a novel in-syringe solid-phase extraction device using metal-organic frameworks as the adsorbent was fabricated for the on-site sampling of polycyclic aromatic hydrocarbons from environmental waters. Trace polycyclic aromatic hydrocarbons were effectively extracted through the self-made device followed by gas chromatography with mass spectrometry analysis. Owing to the excellent adsorption performance of metal-organic frameworks, the analytes could be completely adsorbed during one adsorption cycle, thus effectively shortening the extraction time. Moreover, the adsorbed analytes could remain stable on the device for at least 7 days, revealing the potential of the self-made device for on-site sampling of degradable compounds in remote regions. The limit of detection ranged from 0.20 to 1.9ng/L under the optimum conditions. Satisfactory recoveries varying from 84.4 to 104.5% and relative standard deviations below 9.7% were obtained in real samples analysis. The results of this study promote the application of metal-organic frameworks in sample preparation and demonstrate the great potential of in-syringe solid-phase extraction for the on-site sampling of trace contaminants in environmental waters.

Volatilization and oxidative artifacts of PM bound PAHs collected at low volume sampling (1): Laboratory and field evaluation

Laboratory and field studies were carried out to assess the effects of oxidative degradation and volatilization on PM10 bound polycyclic aromatic hydrocarbons (PAHs), collected at low volume condition according to the EU sampling reference method EN12341:2014 (flow rate 2.3 m3 h−1), on 47 mm quartz filters. For the laboratory experiments, pairs of twin samples were collected in field and, after treatments favoring decomposition or/and volatilization of PAHs on one sample, the PAH amount was compared with that of the corresponding untreated sample. Ozone exposure caused a general PAHs decay with more marked effects on benzo [a]pyrene, perylene and benz [a]anthracene; these compounds showed, similarly to benzo [ghi]perylene, correlations between ozone dose and losses. Treatments with zero air exhibited losses due to volatilization even for 5-ring PAHs up to benzo [a]pyrene, whereas a linear dependence was observed between filter PAH load and losses for benzo [a]anthracene, chrysene and benzofluoranthenes. Concentrations on samples collected simultaneously over 48, 24, 12 and 6 h were compared. Results confirmed a lack of temporal auto-consistency in the PAHs sampling methodology here adopted. In particular higher atmospheric PAH concentrations were ascertained on samples constituted by cumulative filters exposed over shorter sampling times. When 24–h and 2 × 12-h samples were compared, comparable losses were evaluated in the hot and cold seasons. This finding shows that, although in summer meteorology conditions favor sampling artifacts, the effectiveness of these phenomena continue in the winter, probably due to the larger amount of PAH available on the sampling filter (total PAHs ∼ 10 vs 0.5 ng m−3).

Source characterization and exposure modeling of gas-phase polycyclic aromatic hydrocarbon (PAH) concentrations in Southern California

Airborne exposures to polycyclic aromatic hydrocarbons (PAHs) are associated with adverse health outcomes. Because personal air measurements of PAHs are labor intensive and costly, spatial PAH exposure models are useful for epidemiological studies. However, few studies provide adequate spatial coverage to reflect intra-urban variability of ambient PAHs. In this study, we collected 39–40 weekly gas-phase PAH samples in southern California twice in summer and twice in winter, 2009, in order to characterize PAH source contributions and develop spatial models that can estimate gas-phase PAH concentrations at a high resolution. A spatial mixed regression model was constructed, including such variables as roadway, traffic, land-use, vegetation index, commercial cooking facilities, meteorology, and population density. Cross validation of the model resulted in an R2 of 0.66 for summer and 0.77 for winter. Results showed higher total PAH concentrations in winter. Pyrogenic sources, such as fossil fuels and diesel exhaust, were the most dominant contributors to total PAHs.PAH sources varied by season, with a higher fossil fuel and wood burning contribution in winter. Spatial autocorrelation accounted for a substantial amount of the variance in total PAH concentrations for both winter (56%) and summer (19%). In summer, other key variables explaining the variance included meteorological factors (9%), population density (15%), and roadway length (21%). In winter, the variance was also explained by traffic density (16%). In this study, source characterization confirmed the dominance of traffic and other fossil fuel sources to total measured gas-phase PAH concentrations while a spatial exposure model identified key predictors of PAH concentrations. Gas-phase PAH source characterization and exposure estimation is of high utility to epidemiologist and policy makers interested in understanding the health impacts of gas-phase PAHs and strategies to reduce emissions.

RETRACTED: POSSIBILITY OF MONITORING OF PAHs DISTRIBUTION IN THE VERTICAL PROFILE AT THE BACKGROUND METEOROLOGICAL STATION KREŠÍN

<p><strong> This article has been retracted by Editorial Office, upon an approval of all authors. The Publisher apologized for any inconvenience this may cause. </strong></p><p>The contaminants present in the atmosphere have a substantial impact on public health. Among contaminants, the most important are polycyclic aromatic hydrocarbons (PAHs). This paper is focused on the possibility of continuous PAHs monitoring and the description of their vertical distribution using filters, which serve to purify the air before the determination of the greenhouse gases (CO<sub>2</sub>, CH<sub>4</sub>, N<sub>2</sub>O, CO, ozone) and Hg in air, continuously sampled at 8, 50 and 230m at the atmospheric station Krešín near Pacov and elaboration of a simple and economical method of extraction of these filters. The station serves as a point for monitoring the occurrence and remote transport of greenhouse gases and selected atmospheric pollutants and for the measurements of basic meteorological characteristics. In December, 17, 2014, a sampling of 16 priority PAHs started and lasted until December, 9, 2015. Samples were taken approximately once a month. The maximum concentration of ΣPAHs was 15.905 ng/m<sup>3</sup>, measured at the height of 8 meters in the period of 11. 2. 2015–11. 3. 2015, the concentration of benzo[a]pyrene exceeded the immission limit in the period by more than 50%. By the sampling, the hypothesis about decreasing concentration of PAHs with increasing height was confirmed, especially the decrease of heavier PAHs. The sampling has shown that it is highly desirable to use the meteorological tower for sampling of PAHs using PTFE filters either by including the active sampler itself, or by using pre-filters for tropospheric ozone and gaseous elemental mercury analysers.</p>

Cancer Risk Assessment of Airborne PAHs Based on in Vitro Mixture Potency Factors.

Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants associated with adverse human health effects including cancer. However, the risk of exposure to mixtures is difficult to estimate, and risk assessment by whole mixture potency evaluations has been suggested. To facilitate this, reliable in vitro based testing systems are necessary. Here, we investigated if activation of DNA damage signaling in vitro could be an endpoint for developing whole mixture potency factors (MPFs) for airborne PAHs. Activation of DNA damage signaling was assessed by phosphorylation of Chk1 and H2AX using Western blotting. To validate the in vitro approach, potency factors were determined for seven individual PAHs which were in very good agreement with established potency factors based on cancer data in vivo. Applying the method using Stockholm air PAH samples indicated MPFs with orders of magnitude higher carcinogenic potency than predicted by established in vivo-based potency factors. Applying the MPFs in cancer risk assessment suggested that 45.4 (6% of all) cancer cases per year in Stockholm are due to airborne PAHs. Applying established models resulted in <1 cancer case per year, which is far from expected levels. We conclude that our in vitro based approach for establishing MPFs could be a novel method to assess whole mixture samples of airborne PAHs to improve health risk assessment.

Contamination of runoff waters with polycyclic aromatic hydrocarbons in the city of Siedlce

Abstract The paper presents the results of the research on content of 16 polycyclic aromatic hydrocarbons in samples of runoff waters collected in Siedlce city. The samples were collected in March, July and October 2015. The highest mean total concentration of 16 PAHs amounting to 12.54 μmolּdm-3 was determined in water samples collected at Łukowska Street, whereas the lowest concentrations (1.90 μmolּdm-3) were found in samples collected at Warszawska Street. In some samples, small amounts of benzo(a)pyrene were present; the average content ranged from 0.02 μmol⋅dm-3 at Warszawska Street to 0.20 μmolּdm-3 at Garwolińska Street.

Calibration of the complex matrix effects on the sampling of polycyclic aromatic hydrocarbons in milk samples using solid phase microextraction

Solid phase microextraction (SPME), a simple, fast and promising sampling technique, has been widely used for complex sample analysis. However, complex matrices could modify the absorption property of coatings as well as the uptake kinetics of analytes, eventually biasing the quantification results. In the current study, we demonstrated the feasibility of a developed calibration method for the analysis of polycyclic aromatic hydrocarbons (PAHs) in complex milk samples. Effects of the complex matrices on the SPME sampling process and the sampling conditions were investigated. Results showed that short exposure time (pre-equilibrium SPME, PE-SPME) could increase the lifetime of coatings, and the complex matrices in milk samples could significantly influence the sampling kinetics of SPME. In addition, the optimized sampling time, temperature and dilution factor for PAHs were 10 min, 85 °C and 20, respectively. The obtained LODs and LOQs of all the PAHs were 0.1–0.8 ng/mL and 1.4–4.7 ng/mL, respectively. Furthermore, the accuracy of the proposed PE-SPME method for milk sampling was validated by the recoveries of the studied compounds in two concentration levels, which ranged from 75% to 110% for all the compounds. Finally, the proposed method was applied to the screening of PAHs in milk samples.

Spatial and Temporal Distribution of Polycyclic Aromatic Hydrocarbons and Elemental Carbon in Bakersfield, California.

Despite increasing evidence that airborne polycyclic aromatic hydrocarbon (PAH) exposures contribute to adverse health outcomes for sensitive populations, limited data are available on short-term intraurban spatial distributions for use in epidemiologic research. Exposure assessments for airborne PAHs are uncommon because air sampling for PAHs is a labor-, equipment-, and time-intensive task. To address this gap we measured wintertime PAH concentrations during 2010-2011 in Bakersfield, California, USA, a major city in the Southern San Joaquin Valley. Specifically, 58 96-hour integrated PAH samples were collected during 4 time periods at 14 locations from November 2010 to January 2011; duplicates were collected at two sites. We also collected elemental carbon (EC) at the same 14 sites and analyzed the two time periods with the highest ambient PAH pollution. We used linear regression models to quantify the relationship between potential spatial and temporal predictors of PAH concentrations. We found that wintertime PAH concentrations in Bakersfield, CA, are best predicted by meteorological variables and traffic proximity. Our model explains a moderate amount of the variability in the data (R2=0.58), likely reflecting the major sources of PAHs in Bakersfield. We also observed that PAH concentrations were more spatially variable than EC concentrations. Comparing our data to historical monitoring data at one location in Bakersfield showed that the relatively low PAH concentrations during the 2010-2011 winter in Bakersfield is part of a long-term trend in decreasing PAH concentrations.

Investigation of sources of atmospheric polycyclic aromatic hydrocarbons at Mount Lushan in southern China

AbstractGaseous and particulate samples of polycyclic aromatic hydrocarbons (PAHs) were collected at the summit of Mount Lushan (29.58°N, 115.98°E, 1165 m asl) in southern China from August to September of 2011 and March to May of 2012 except special meteorological conditions such as rainy or very foggy days. The concentration of PAHs in total (gaseous and particulate PAHs) ranged from 15.79 to 160.53 ng m−3 (mean 41.67 ng m−3). Observed logarithmic values of particulate mass fraction (log θ) and partitioning coefficient (log Kp) were all higher than values calculated by the three gas‐particle partitioning models, presenting higher fraction of particulate PAHs, indicating continual contribution of gaseous PAHs to particulate PAHs concentrations during long‐range transport of air masses. Identified potential source regions using potential source contribution function analysis suggested significant contributions of emissions from coking, thermal power, and steel plants. The sources of PAHs levels at Mount Lushan that were identified using positive matrix factorization included diesel vehicles (43%), coal‐fired boiler combustion (33%), coke oven source (17%), and incineration source (7%).

Distribution characteristics and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in the Liao River drainage basin, northeast China.

The Liao River drainage basin, which is one of China's seven major rivers basins, is located in northeast China. This region is characterized by important industrial bases including steel factories and oil and chemical plants, all of which have the potential to contribute pollutants to the drainage basin. In this study, 16 polycyclic aromatic hydrocarbons (PAHs) in water and suspended particulate matter (SPM) in the major rivers of the Liao River drainage basin were identified and quantified by gas chromatography mass spectrometry (GC/MS). The total PAH concentrations ranged from 0.4 to 76.5μg/g (dry weight) in SPM and 32.6 to 108ng/L in surface water, respectively. Low-ring PAHs (including two- and three-ring PAHs) were dominant in all PAH samples, and the level of low-ring PAHs in surface water was higher than that in SPM. The proportion of two-ring PAHs was the highest, accounting for an average of 68.2% of the total PAHs in surface water, while the level of three-ring PAHs was the highest in SPM, with an average of 66.3%. When compared with other river systems, the concentrations of PAHs in the Liao River drainage basin were lower. Identification of the emission sources based on diagnostic ratios suggested petroleum and fossil fuel combustion were important contribution to PAHs in the study area.

Tracking human footprints in Antarctica through passive sampling of polycyclic aromatic hydrocarbons in inland lakes

Freely dissolved polycyclic aromatic hydrocarbons (PAHs) were monitored in seven inland lakes of Antarctica by a polyethylene (PE)-based passive sampling technique, with the objective of tracking human footprints. The measured concentrations of PAHs were in the range of 14–360 ng L−1 with the highest values concentrated around the Russian Progress II Station, indicating the significance of human activities to the loading of PAHs in Antarctica. The concentrations of PAHs in the inland lakes were in the upper part of the PAHs levels in aquatic environments from remote and background regions across the globe. The composition profiles of PAHs indicated that PAHs in the inland lakes were derived mainly from local oil spills, which was corroborated by a large number of fuel spillage reports from ship and plane crash incidents in Antarctica during recent years. Clearly, local human activities, rather than long-range transport, are the dominant sources of PAH contamination to the inland lakes. Finally, the present study demonstrates the efficacy of PE-based passive samplers for investigating PAHs in the aquatic environment of Antarctica under complex field conditions.

Simultaneous Sampling of Vapor and Particle-Phase Carcinogenic Polycyclic Aromatic Hydrocarbons on Functionalized Glass Fiber Filters

The sampling of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere is often performed on filters, which retain only aerosol particles, disregarding the vapor fraction; after the filter, an adsorbent (e.g., polyurethane foam, PUF, or styrene/divinylbenzene, XAD) is sometimes used for sampling vapors not retained from the filter. However, the use of an adsorbent may lead to many disadvantages: contaminations, analysis time and costs, and size problems when developing automated or personal samplers. In this work, a functionalized glass fiber filter for the simultaneous sampling of aerosol particles and vapor fraction is presented for the sampling of PAHs in air. A low sampling efficiency was observed for 3 ring PAHs, but all carcinogenic PAHs (according to IARC) were totally retained on functionalized filters. On the other hand, a comparison with normal filter sampling was performed, and results obtained confirm that ＞ 10% of benzo(a)pyrene can be lost from normal filters. Together with size reduction, another advantage of the functionalized filter is an enhancement in the extraction and purification recovery.

The evaluation of different sorbents and solvent mixtures in PAH sample preparation for GC/GC-MS analysis

GC/GC-MS-analysis of polycyclic aromatic hydrocarbons (PAHs) in complex samples requires a previous treatment of the samples. In order to establish the effects of sorbents/solvents on the overall accuracy of the method, dispersive solid phase extraction as a method for the sample preparation in PAHs determination is employed using three different solvent mixtures and sorbents (PSA, C18 and PS-DVB). Recovery values are dependent on compound and sorbents. The highest mean recovery was recorded for cyclohexane/acetone-C18 combination (58.45%) which is satisfactory, with the values above 70% for naphthalene (76.05%), fluoranthene (80.22%), pyrene (111.99%) and benzo[g,h,i]perylene (71.77%). Similar recoveries were obtained for cyclohexane/acetone-PS-DVB (55.50%) and cyclohexane/acetone- PSA (55.30%). Cyclohexane/acetone gave the highest recovery values for all three sorbents, so this solvent mixture could be used in PAH extraction from various matrices. Though the obtained recovery values for the investigated sorbent/solvent combinations were not impressive, they might be a good basis for future researches since, as far as we know, PS-DVB was not used in dSPE sample preparation for GC/GC-MS analysis of PAHs.

A simple methodological validation of the gas/particle fractionation of polycyclic aromatic hydrocarbons in ambient air.

The analysis of polycyclic aromatic hydrocarbons (PAH) in ambient air requires the tedious experimental steps of both sampling and pretreatment (e.g., extraction or clean-up). To replace pre-existing conventional methods, a simple, rapid, and novel technique was developed to measure gas-particle fractionation of PAH in ambient air based on ‘sorbent tube-thermal desorption-gas chromatograph-mass spectrometer (ST-TD-GC-MS)’. The separate collection and analysis of ambient PAHs were achieved independently by two serially connected STs. The basic quality assurance confirmed good linearity, precision, and high sensitivity to eliminate the need for complicated pretreatment procedures with the detection limit (16 PAHs: 13.1 ± 7.04 pg). The analysis of real ambient PAH samples showed a clear fractionation between gas (two-three ringed PAHs) and particulate phases (five-six ringed PAHs). In contrast, for intermediate (four ringed) PAHs (fluoranthene, pyrene, benz[a]anthracene, and chrysene), a highly systematic/gradual fractionation was established. It thus suggests a promising role of ST-TD-GC-MS as measurement system in acquiring a reliable database of airborne PAH.

First results of the ORGANIC experiment on EXPOSE-R on the ISS

AbstractThe ORGANIC experiment on EXPOSE-R spent 682 days outside the International Space Station, providing continuous exposure to the cosmic-, solar- and trapped-particle radiation background for fourteen samples: 11 polycyclic aromatic hydrocarbons (PAHs) and three fullerenes. The thin films of the ORGANIC experiment received, during space exposure, an irradiation dose of the order of 14 000 MJ m−2 over 2900 h of unshadowed solar illumination. Extensive analyses were performed on the returned samples and the results compared to ground control measurements. Analytical studies of the returned samples included spectral measurements from the vacuum ultraviolet to the infrared range and time-of-flight secondary ion mass spectrometry. Limited spectral changes were observed in most cases pointing to the stability of PAHs and fullerenes under space exposure conditions. Furthermore, the results of these experiments confirm the known trend in the stability of PAH species according to molecular structure: compact PAHs are more stable than non-compact PAHs, which are themselves more stable than PAHs containing heteroatoms, the last category being the most prone to degradation in the space environment. We estimate a depletion rate of the order of 85 ± 5% over the 17 equivalent weeks of continuous unshadowed solar exposure in the most extreme case tetracene (smallest, non-compact PAH sample). The insignificant spectral changes (below 10%) measured for solid films of large or compact PAHs and fullerenes indicate a high stability under the range of space exposure conditions investigated on EXPOSE-R.