Gaseous PAHs Research Articles

Risk assessment of inhalation exposure to polycyclic aromatic hydrocarbons in Taiwanese workers at night markets

To examine the inhalation exposure of cooks at night markets in Taiwan to PAHs and to estimate the corresponding potential human health risks posed by the inhalation of carcinogenic PAHs. Eight-hour personal air samples collecting particle-bound PAHs and XAD-2 retaining PAHs in the gas phase were taken by personal PM(2.5) cyclones with cooks carrying the sampler on the shoulder while cooking at selected food stalls at four night markets in Taipei, and the concentrations of 16 priority PAHs in both particulates and air were measured with GC/MS. The total identified PAHs in both gas and PM(2.5) phases exposed by cooks during cook hours ranged from 233,995 to 44,166 ng m(-3). Total exposed PAHs in cooks, as well as the percentage of PAHs in PM(2.5), were the highest at the barbecue stall F3. The fractions of gaseous PAHs (97%) in the four food stalls were consistently higher than the fractions of particulate PAHs (3%). The diagnostic ratios of PAHs fell within the range of those found in other studies related to cooking. At all typical food stalls in night markets except for F2, the excess lifetime cancer risk (ELCR) of cooks are beyond the acceptable target risk range of 10(-6) to 10(-4) for occupational workers set by USEPA. The PAHs measured in the night markets originated from combustion due to food cooking. The control of gaseous PAH emissions would be more important than the fractions of particulate PAH emissions. Occupational exposure to cooking emissions in Taiwanese workers at night markets is of health concern. Thus, effective protective measures are therefore suggested to minimize cooks' exposure to such emissions, such as wearing mask of activated carbon, evacuating the exhaust into water tank with bio-surfactant to improve PAH removal, installing effective mechanical exhaust vacuum or building high exhaust fume hood above cooking ovens.

Measurement of Gaseous PAHs with an Innovative Passive Sampler in Community Exposure Studies

Measurement of Gaseous PAHs with an Innovative Passive Sampler in Community Exposure Studies

On the reactive uptake of gaseous PAH molecules by micron-sized atmospheric water droplets

A falling droplet reactor was used to study the heterogeneous oxidation of gaseous PAH molecules adsorbed on a 92 μm diameter water droplet by ozone. The dynamic partition constant for the PAH between the droplet and air and the first-order surface rate constant was measured. The increase in uptake with ozone concentration was due to increased mass transfer via surface reaction of co-adsorbed ozone and PAH. The surface rate constant was rationalized through the Langmuir–Hinshelwood mechanism. The rate constant was smaller for phenanthrene than naphthalene. The main reaction products identified in the aqueous phase indicated the peroxidic route for surface reaction of ozone with PAH. The heterogeneous reaction rate of ozone with adsorbed phenanthrene at the air–water interface of a 92-μm droplet was estimated to be 9300 times larger than the homogeneous reaction of ozone with phenanthrene in the gas phase and it was 76 times larger than the homogeneous oxidation by hydroxyl radical in the gas phase. For naphthalene that is more volatile, however, the homogeneous reaction with hydroxyl was more important. Increased organic carbon added to the droplet increased both the partition constant for phenanthrene and surface reaction with ozone. The partition constant for a droplet formed from actual fog water was much larger than for pure distilled water.

Participants' exposure to PM2.5 and gaseous/particulate polycyclic aromatic hydrocarbons during the Ma-tsu Goddess parade

The Ma-tsu Goddess parade is a very special religious tradition in Taiwan attracting thousands of believers every year. This parade is an 8-day-and-7-night event and the entire walking distance is about 280 km. This study assesses participants' exposure to PM(2.5), and gaseous and particulate PAHs. The contribution of various exposure factors was also evaluated. Sampling was conducted during the entire parade period in 2001. Exposures of participants who were riding motorcycles or driving cars were assessed. Personal environmental monitors mounted with Teflon filters and polyurethane foams were used for particulate and gaseous sampling. PAHs were analyzed with GC-FID. Stepwise regression analysis was used to evaluate the contribution of various factors, including the number of temples visited each day, the duration of temple visits, the number of temple co-visitors, visitors riding motorcycles or driving cars, etc. During the Ma-tsu Goddess parade, the mean PM(2.5), particulate and gaseous PAH exposures were around 119 +/- 60.8, 0.36 +/- 0.23 and 0.86 +/- 0.48 microg/m(3), respectively. Participants' PM(2.5) and particulate PAH exposures were about two to three times the exposure during daily routines. The profiles of 16 PAH species in the particulate and gaseous phases for participants' and normal daily exposures were also different. Incense smoke and vehicle exhaust were two important sources. Worshippers would be exposed to 0.096 microg/m(3) more PM(2.5) for every incremental minute in temples. In addition, motorcyclists were exposed to 0.21 microg/m(3) higher particulate PAHs than the car drivers.

Evaluation of an annular denuder tubes for atmospheric PAH partitioning studies—1: evaluation of the trapping efficiency of gaseous PAHS

This paper is an evaluation of the gas phase collection efficiency of a commercially available annular denuder sampler used to collect gas and particle phase semivolatile organic compounds. Laboratory and field experiments were carried out to determine the gas phase collection efficiency using naphthalene as reference compound. Laboratory tests were performed to study the influence of environmental conditions (temperature, relative humidity and gas phase concentration) and sampling conditions (sampling flow rate, and sampling duration) on the collection efficiency. During laboratory experiments, the collection efficiency of the gas phase was measured using a dynamic gas generator. It was above 90% for a range of experimental conditions covering: temperature from 9°C to 39°C, relative humidity from 30% to 90%, sampling duration up to 14 h, flow rate of 1 and 2 m3 h−1 and quantity of gaseous naphthalene considerably higher than the one usually collected during atmospheric sampling.

The characterisation of polycyclic aromatic hydrocarbons emissions from burning of different firewood species in Australia

Four kinds of woods used for residential heating in Australia were selected and burned under two burning conditions in a domestic wood heater installed in a laboratory. The selected wood species included pine ( Pinus radiata), red gum ( Eucalyptus camaldulensis), sugar gum ( Eucalyptus cladocalyx) and yellow box ( Eucalyptus melliodora). The two different burning conditions represented fast burning and slow burning, with the air inlet of the combustion chamber respectively ‘full open’ and ‘half open’. By sampling and analysing particulate and gaseous emissions from the burning of each load of wood under defined experimental conditions, PAHs emissions and their profiles in the particulate and gaseous phases were obtained. 16 species out of the 18 selected PAHs were detected. Of these, seven species were detected in the gaseous phase and most were lower molecular weight compounds. Similarly, more than 10 species of PAHs were detected in the particulate phase and these were mostly heavier molecular weight compounds. Under both burning conditions, emission levels for total PAHs and total genotoxic PAHs were the highest for pine and lowest for sugar gum, with red gum being the second highest, followed by yellow box. Using the specific sampling method, gaseous PAHs accounted for above 90% mass fraction of total PAHs in comparison to particulate PAHs (10%). The majority of the genotoxic PAHs were present in the particulate phase. PAHs emission levels in slow burning conditions were generally higher than those in fast burning conditions.

Long-term sampling: Suitable monitoring strategy for determination of semi-volatile PAHs at outdoor and indoor sites

A new, molecular diffusion-based, sampling device (Analyst 2) has been used for the determination of semi-volatile PAHs in air. It has been developed from a previous model (Analyst), which is suitable for volatile hydrocarbons. The new model is capable of collecting enough gaseous PAHs for GC-MS analysis of enriched samples after 2 months exposure to both urban and suburban air. The adsorbent material adopted for enriching PAHs from air (Carbopack C) gives good recoveries of analytes from naphthalene to chrysene when a single solvent extraction is run at ambient temperature.

An experimental set up of a PAH vapour generator and its use to test an annular denuder

The aim of this work is to develop and test a dynamic gas generator for semi-volatile organic compounds (SVOC). A single compound, naphthalene, is used as a surrogate PAH to test the system. The dynamic generation of PAH is based on the permeation technique [Analyst 106 (1981) 817; Am. Ind. Hyg. Assoc. J. 38 (1977) 712]. Monitoring the temperature and measuring the mass of PAH present in the permeation chamber every 48 h gives a direct measurement of the sublimation rate of the PAH. Knowing the flow rate, gives an accurate value of the concentration of PAH from the generator. It was found stable over a period of time under constant operating conditions. This concentration is diluted down to between 0.3 and 30 ppbv by a controlled flow of pure air. The diluting airflow is a mixture of dry and wet air, making it possible to control the relative humidity of the flow from the generator as well as its concentration in PAH. We used this generator to calibrate an annular denuder tube, based on the study by Gundel et al. [Atmos. Environ. 29 (1995) 1719]. Although this technique has been shown to be artefact-free for sampling gaseous PAH [Polycyclic Aromatic Compounds 9 (1996) 67; Atmos. Environ. 28 (1994) 3083], its trapping efficiency still depends on environmental parameters (temperature, relative humidity and sampling duration). Accordingly, we used our generator to calibrate a single annular denuder under controlled conditions (T°C, HR%, C PAH, sampling duration). The trapping efficiency of the denuder was calculated by two independent methods. Firstly, by comparing the amount trapped on a denuder with the measured mass sublimated in the generator. Secondly, by putting two denuders in series and comparing the mass collected on the first and the second tube. These two methods gave similar results, within the 10% relative uncertainties of both methods. The first results obtained show that, in environmental conditions, the efficiency ranges between 90 and 100%.

Urinary 1-hydroxypyrene as a biomarker of internal dose of polycyclic aromatic hydrocarbons in carbon black workers.

In this study, a total of 30 workers were selected, including eight wet pelletizing workers and 22 packaging workers. For all selected workers, urine samples were collected on the first day pre-shift, first day post-shift and fifth day post-shift, and their urinary 1-hydroxylpyrene levels (1-OHP) were determined (denoted as BM1pre, BM1post and BM5post, respectively). Personal respiratory exposures, including both inhalable particle-bound PAHs (Cinh) and gaseous PAHs (Cgas), together with dermal exposure to particle-bound PAHs (Cskin) were measured. Personal background information, including age, sex and smoking habit, was carefully registered. Pyrene exposure was statistically significantly correlated with exposure to PAHs and carcinogenic PAHs. Multiple linear regression analysis results showed that the BM1post values could not be explained by workers' exposures. For BM5post in packaging workers, both the regression model (R2 = 0.73) and the regression coefficients for Cgas, Cinh and Cskin were statistically significant (P < 0.05). For pelletizing workers, the R2 value was higher but was not statistically significant because of the smaller number of workers. The resultant regression coefficients for 'sex', 'smoking habit' and 'age' were statistically insignificant (P >> 0.05), which could be because these variables made relatively small contributions to BM5post. In conclusion, this study suggests BM5post could be a suitable indicator for PAH exposures of carbon black workers, on the condition that both respiratory (including gaseous PAHs and particle-bound PAHs) and dermal exposures have been assessed.

Environmental monitoring of semi-volatile polyciclic aromatic hydrocarbons by means of diffusive sampling devices and GC-MS analysis

A molecular diffusion-based sampling device (known asAnalyst 2) is presented for the determination of semi-volatile polyaromatic hydrocarbons (PAH's) in air. It has been developed from a previous model (i.e. Analyst), which was suitable for volatile hydrocarbons. The new model is capable of collect enough gaseous PAH's to allow GC-MS analysis of enriched samples after two-month exposition to either urban or suburban air. The adsorbing material adopted for enriching the PAH's, i.e. Carbopack C, allows good recoveries of analytes ranging from naphthalene to chrysene, when only a single solvent extraction is run at ambient temperature. Some field experiments generated gaseous PAH concentrations that were in agreement with those expected at urban and suburban sites.

SIZE DISTRIBUTIONS OF POLYCYCLIC AROMATIC HYDROCARBONS—GAS/PARTICLE PARTITIONING TO URBAN AEROSOLS

PAH size distributions were measured at Mumbai (formerly Bombay), India, to examine PAH partitioning to multimodal urban aerosols. Bimodal size distributions were obtained with a predominance of non-volatile PAH species in the fine mode and semi-volatile PAH species in the coarse mode. We develop size-resolved PAH gas/particle partition coefficients, based on adsorption and absorption theory, and analyse measurements in terms of estimated PAH size distributions in typical urban airsheds dominated by primary and secondary aerosol constituents. Adsorption explains PAH presence in the nuclei and accumulation modes where the aerosol surface area predominates (primary emissions), while absorption explains their predominance in the accumulation mode where absorbing organic matter is available (secondary aerosol constituents in a smoggy airshed). Volatilisation of semi-volatile PAH from nuclei mode aerosols, at enhanced rates (Kelvin effect), and their absorptive partitioning to accumulation mode aerosols, enhanced in a smoggy airshed, would explain previous measurements of semi-volatile PAH predominance in the accumulation mode in Los Angeles. The absence of a predominant PAH accumulation mode in Mumbai measurements is likely from the absence of significant photochemistry and aerosol organic matter. Equilibrium adsorption and absorption are unable to explain coarse particle PAH predominance which would occur by dry deposition scavenging of gaseous and nuclei-mode PAH by soil particles which undergo cyclic re-suspension and deposition in an urban airshed. Coarse particle morphology and adsorption affinity of PAH to mineral particles must be examined to better understand PAH predominance in coarse mode aerosols.

Diffusive Exchange of Gaseous Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls Across the Air−Water Interface of the Chesapeake Bay

Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of the year to estimate net diffusive air−water gas exchange rates. Gaseous PAHs are absorbed into the bay's surface waters during the spring, and lighter compounds revolatilize in the late summer and early fall due to seasonal changes in surface water temperature and atmospheric PAH levels. On an annual basis, the atmosphere is a net source of volatile PAHs to the Chesapeake Bay, and gas absorption may be the largest external source of fluorene and phenanthrene, providing up to three times the combined loadings from wet and dry aerosol deposition and from tributaries. Largest PAH absorptive fluxes occurred in the northern Chesapeake when prevailing winds carried PAH-enriched air from the Baltimore-Washington urban area over the bay. In contrast to PAHs, PCBs volatilize from the Chesapeake Bay throughout the year, with the largest fluxes occurring in September and the smallest fluxes in June. However, higher chlorinated (6−8) homologues are absorbed by bay waters during most of the year. Highest PCB volatilization rates were observed in the northern Chesapeake Bay and near the James River in the southern bay, indicating volatilization offsets PCB loading from the bay's tributaries. Volatilization is the dominant removal process for PCBs from the Chesapeake Bay, removing an estimated 400 kg/year. This value is larger than current external PCB loadings, suggesting that release of PCBs from historically contaminated sediments supports volatilization from the bay.

Particle/Gas Concentrations and Distributions of PAHs in the Atmosphere of Southern Chesapeake Bay

Atmospheric PAH concentrations were measured at four sites characterized as rural (Haven Beach), semi-urban (York River), urban (Hampton), and industrialized (Elizabeth River) areas as part of a study to quantify gaseous exchange fluxes across the air−water interface of southern Chesapeake Bay. Aerosol particle-associated PAH concentrations were similar at all sites; however, PAH gas-phase concentra tions in the urban areas were as much as a factor of 50 greater than those at the rural site. Mean total PAH concentrations (∑ 14 PAHs) ranged from 5.31 ng/m3 at the rural site to 71.6 ng/m3 at the urban site. Daily total PAH concentrations ranged from 1.23 to 180 ng/m3. Exponential increases in gaseous PAH concentrations with temperature were observed at the non-rural sites, suggesting volatilization from contaminated surfaces (soils, vegetation, roads) during warmer weather; whereas PAH gas concentrations at the rural Haven Beach site exhibited little seasonal variability. Aerosol particle-associated PAH lev...

Evolution of macromolecular dust: Far-ultraviolet spectral dust extinction and gas absorption of stellar light as measured with the Hopkins Ultraviolet Telescope

From far-ultraviolet (FUV) spectra of B stars taken with the Hopkins Ultraviolet Telescope (HUT) and Voyager space observations, we determine the far-ultraviolet extinction by Galactic dust and hydrogen absorption in the local spiral-arm clouds towards HD 25443 (B0.5 III), HD 37903 (B1.5 V), and HD 200775 (B3 Ve). We find that the (n (H)) = 1.3 cu cm and number fraction (f = 0.31) of H atoms in molecular hydrogen relative to the total hydrogen indicates a mostly diffuse medium toward HD 25443. We also determine f = 0.56 for the gas in the photodissociation region (PDR) in front of HD 37903 and f approximately equals 0.36 for the HD 200775 PDR. The inferred ratios of N(H2)/I(CO) = 2.4 to 2.8 x 10(exp 20)/K(km/s)/sq cm for cool gas in dark clouds agree with previous canonical estimates of N(H2)/I(CO) = 2 to 3 x 10(exp 20)/K(km/s)/sq cm and support the use of the ratio for determining masses of molecular clouds. We find that the shape and strength of the HD 25443 FUV extinction is the same as a diffuse-medium mean extinction (R(sub nu) = 2.95) extrapolated from mid-UV wavelengths (normal). The HD 37903 FUV extinction through a bright H2 photodissociation region is higher than a mean FUV extinction(R(sub nu) = 4.11), as is the HD 200775 extinction. Another star from the literature rho Oph, probes the dense medium and exhibits an FUV extinction of normal mean strength (R(sub nu) = 4.55) but steeper shape. The normal FUV -extinction of HD 25443 implies that the small FUV-extinction dust in the diffuse medium forms in p art from larger grains as the grains shatter under shocks. The normal strength of the rho Oph FUV-extinction indicates that the minute dust condenses onto or coagulates into larger grains in the dense medium. The high extinction deviation of the HD 37903 PDR (and HD 200775 PDR) shows that FUV radiation from hot stars with T(sub eff) approximately equals 20,000 to 23,000 K in PDRs can evaporate some of the FUV-extinction dust from grain surfaces. In contrast, previously measured extinctions in Galactic H(+) (H II) regions shows that FUV radiation at T(sub eff) greater than 25,000 K can destroy some of the dust in H(+) regions. Thus, some of the FUV-extinction dust is highly volatile. We find that the dust carrier of the variable FUV-extinction is correlated (r = 0.99) with the mid-IR (12 micrometers) radiation from hydrocarbon dust. The volatile FUV-extinction component could thus be due to minute hydrocarbon dust particles or macromolecules, probably PAHs, which are known to condense onto larger grains in the dense medium. Larger grains compsed of PAHs clustered into a solid could thus produce the steep FUV extinction of the rho Oph dense medium. After exposure to FUV photons wihtin approximately 1 pc of HD 37903, PAHs with about 30 carbon atoms would evaporate off the larger grains, increasing gaseous PAH abundance by approximately 14%. Also, after receiving shocks in the diffuse medium toward HD 25443, the larger hydrocarbon grains would shatter into PAH molecules. In summary, as the Galactic medium cycles betwee n the diffuse and dense medium, hydrocarbon dust cycles into and out of larger grains under the influence of shocks, radiation, and condensation.

Partitioning model of PAHs between gaseous and particulate phases with consideration of reactivity of PAHs in an urban atmosphere

Abstract The reactivity of PAH substances in urban atmosphere and its influence on the partitioning models between gaseous and particulate phases for semi‐volatile PAHs were investigated in this study. A new sampling experiment for gaseous and particulate PAHs during day, night and whole day (24 hours) time periods was conducted at a monitoring station in downtown Taipei in 1991. The reactivity of PAH substances was determined by the characteristic ratio, reactive PAH / non‐reactive PAH and the order of reactivity are as follows, Benzo(a)anthracene > Phenathrene + Anthracene > Acenaphthene > Chrysene > Pyrene > Naphthalene > Fluoranthene > Fluorene. On the other hand, the partitioning models for day, night, and whole day for semi‐volatile PAHs, Fluoranthene, Pyrene, Chrysene, and Benzo(a)anthracene, were evaluated. It is indicated that higher coefficients of determination (r2) of the regression analysis between the partitioning term and inverse of temperature were obtained for day or night models compared...

Contribution of PAHs to the Interstellar Extinction Curve

Absorption spectra of some gaseous PAHs, either pure species or natural mixtures, have been obtained in the VUV-visible region and compared to the interstellar extinction curve.The assumption that free PAHs are ubiquitous in the ISM cannot be rejected by incompatibility between the interstellar extinction curve and the absorption spectra of such molecules. PAHs absorb in the FUV rise and may give an important contribution to the bump at 2200 Å. We have derived that about 15% of the cosmic carbon is involved in these molecules.

Analysis of gaseous and particle-associated PAH and nitroarenes in ambient air

Analysis of gaseous and particle-associated PAH and nitroarenes in ambient air

PAH-losses from glass fiber filters under the conditions of different air volume sampling: results of field evaluations in occupational atmospheres

The estimation of the occupational medical and toxicological risks to workers exposed to PAH depends on sampling these compounds, some of which are carcinogenic, with as little loss as possible in the air of the working environment. A sampling system for the collection of air samples for PAH in field investigations consisting of a glass fiber filter followed by a suction pump has been tested for its efficiency at various suction rates using n=19 specially selected reference substances. The variability of the suction rate obtainable with the pump employed is to be regarded as being of particular significance. A total of 60 determinations made in areas devoted to the manufacture of artificial coal and at road paving operations revealed greatly reduced and pumping rate-dependent recoveries, i.e. correspondingly high losses. With an air throughput of 22 500 l/h an average of 47.8% of the total of 19 PAH was recovered on the glass fiber filter; when a suction pump with a throughput of 2840 l/h was employed 28% of the PAH was not collected and the losses amounted to 15% at a pumping rate of 120 l/h. The losses of 5 PAH compounds chosen for their carcinogenicity were of the same order of magnitude with ca. 51%, 22% and 11%. The influence of the number of rings in the PAH, i. e., its increasing boiling point, plays a decisive role in its recovery rate. Thus, when sampling at a throughput of 120 l/h, the recovery rates of various members of the 4, 5, 6 and 7-ring PAH systems were on average 77.1%, 88.4%, 95.6% and 99.1%, respectively. Glass fiber filters are not suitable for use as the sole collection phase for PAH air sampling, particularly when pumps having a high throughput are employed. A combination of filters as the collection phase for particulate PAH followed by adsorbent tubes of Tenax or XAD-2 for gaseous PAH must be regarded as necessary for the collection of representative samples for determination of the total concentration of polycyclic aromatics.

A review of sampling methods for polyaromatic hydrocarbons in air.

The recent literature describing sampling methods and development of sampling techniques for airborne PAH is reviewed. Aspects of sampling such as particle sizing and the types of collection media for particle bound and gaseous PAH are discussed. Findings on formation of artifacts during sampling for PAH as a result of reactions with copollutants existing in air are summarized. Effects of sampling conditions such as flow rate, temperature, humidity and sampling duration are reviewed. Developments reported for both passive sampling for PAH and for direct measurement techniques, such as second derivative ultraviolet absorption spectrometry and synchronous luminescence, are also noted.