Yields Of Polycyclic Aromatic Hydrocarbons Research Articles

Impact of meteorology and energy structure on solvent extractable organic compounds of PM 2.5 in Beijing, China

Twenty-eight PM 2.5 samples collected in Summer (July 2002) and Winter (November 2002) at two sites in Beijing, China were analyzed using GC/MS to investigate the impact of meteorology and coal burning on the solvent extractable organic compounds (SEOC). The characteristics and abundance of the n-alkanes, polycyclic aromatic hydrocarbons (PAHs), n-fatty acids and n-alkanols were determined. Source identification was made using organic species as molecular markers. Semi-volatile compounds of alkanes and PAHs had much higher concentrations in winter than summer because of the large difference in the temperature between the seasons. Plant wax emission was a major contributor to n-alkanes in summer, but fossil fuel residue was a major source (>80%) in winter. The seasonal differences in the distribution of pentacyclic triterpanes clearly shows the impact of coal burning for space heating in winter. The yield of PAHs in winter (148 ng m −3 at the urban site and 277 ng m −3 at the suburban site) was six to eight times higher than that in summer and was found to be mainly from coal burning. Higher pollutant concentrations were measured at the suburban site than the urban site in winter due to the rapid expansion of the city limit and the relocation of factories from urban to suburban areas over the last two decades.

The effects of pressure on the yields of polycyclic aromatic hydrocarbons produced during the supercritical pyrolysis of toluene

To understand better the reactions leading to polycyclic aromatic hydrocarbons (PAH)—and ultimately carbonaceous solids—within the context of supercritical fuel pyrolysis, we have pyrolyzed the model fuel toluene (critical temperature, 319 °C; critical pressure, 41 atm) in an isothermal silica-lined stainless steel coil reactor at 535 °C, 140 s, and pressures of 20–100 atm. Analysis of the reaction products by gas chromatography and high-pressure liquid chromatography reveals that the yields of benzene and 27 individual PAH increase exponentially with pressure. For 26 of these 28 products, the experimentally measured yield/pressure data conform well to a first-order global kinetics model—permitting determination of the preexponential factor A and the activation volume Δ V ≠, which appear in the pressure-dependent expression for the kinetic rate constant: k = A exp [(−Δ V ≠/ RT) p]. For most of the PAH, derived values of Δ V ≠ lie between −2.5 and −4 L/mol, signifying the doubling of PAH formation rates by pressure increases of only 18.4 or 11.5 atm, respectively. Some of the larger PAH, such as the 8-ring benzo[ a]coronene and the 9-ring naphtho[8,1,2- abc]coronene, exhibit negative activation volumes of even greater magnitude—a result of particular relevance to the formation of carbonaceous solids, as large PAH are thought to be precursors to these solids. The PAH yield data also reveal product yield ratios, within certain PAH isomer families, that are peculiar to the high-pressure supercritical pyrolysis environment—suggesting that mechanisms for PAH formation differ significantly from those in atmospheric-pressure gas-phase pyrolysis environments.

CHARACTERISTICS OF PAHS INTRINSIC DEGRADATION IN TWO COKE FACTORY SOILS

Polycyclic aromatic hydrocarbons (PAHs) are the most commonly found pollutants in former coke site grounds. These organic pollutants are particularly a concern because of their possible toxic, carcinogenic or mutagenic properties. Biodegradation is one possible pathway for PAHs elimination from soils. This study aims to evaluate intrinsic degradation potential of PAHs in soils taken from two former coke sites, differing by their contamination levels and by their physico-chemical characteristics (organic carbon and metal contents).PAHs biodegradation kinetics as observed in both soil types distinguishes between two steps: a first step showing a rapid but short PAHs abiotic degradation, followed by a second step which is characterized by a much slower PAHs decrease pattern, progressively smoothing along time. These patterns lead to a significant decrease in the bulk PAHs content of 35% and 46% respectively for site 1 and site 2 soils after 12 months. In this experiment, PAHs degradation seems to be altered neither by the conditions of the medium (availability of carbon, phosphorus, nitrogen, moisture, oxygen …), nor by any decrease in bacterial degrading activity, but rather by lack of PAHs' bioavailability and recalcitrance of some degradation products. If the occurrence of metals and organic carbon does not alter the bulk yield of PAHs' degradation, it does modify the degradation pattern, insofar as bacterial processes seem to need longer to set when metals and organic carbon are present in higher amounts.

Decomposition of benzene in the RF plasma environment: Part II. Formation of polycyclic aromatic hydrocarbons

This study investigated the characteristics of polycyclic aromatic hydrocarbons (PAHs) formed during the decomposition of benzene (C 6H 6) in radio-frequency (RF) plasma environments. The identification and quantification were accomplished by using a GC/MS for PAHs and an on-line Fourier transform infrared (FT-IR) spectrometer for the reactants and gaseous products. The analytical results show that PAHs were formed in both C 6H 6/Ar and C 6H 6/H 2/Ar systems. In terms of individual PAHs, naphthalene (C 10H 8) was the predominant species found among the 21 PAHs under all operational conditions, phenanthrene and chrysene are the next. High-ring PAHs did not form easily in the C 6H 6/Ar and C 6H 6/H 2/Ar system, especially at high input power and high C 6H 6 feed concentration ( C C 6 H 6 ) for the former system. Yields of PAHs with different ring numbers decreased with increasing ring number. At low input power, increasing C C 6 H 6 would promote yields of PAHs, while adding hydrogen as the auxiliary gas suppressed PAHs formation. Higher input power or addition of oxygen not only effectively suppresses PAHs formation but also completely destroys C 6H 6. Owing to the absence of the principal intermediate species, phenol (C 6H 5OH), from the gas products of C 6H 6/O 2/Ar system, H-abstraction–C 2H 2-addition (HACA) pathway is proposed as the primary mechanism for PAHs formation in the present study. Gas phase distribution of total-PAHs accounts for 20–95.3% at 2% of C C 6 H 6 among C 6H 6/Ar, C 6H 6/H 2/Ar and C 6H 6/O 2/Ar systems. This study suggests that gas-phase PAHs should not be ignored, particularly in C 6H 6/Ar systems under high input power and high C C 6 H 6 , or in C 6H 6/O 2/Ar systems.

Does glucose enhance the formation of nitrogen containing polycyclic aromatic compounds and polycyclic aromatic hydrocarbons in the pyrolysis of proline?

The gas-phase pyrolysis of proline, glucose, 1-[(2′-carboxy)pyrrolidinyl]-1-deoxy- d-fructose (the proline Amadori compound), and a 1:1 mixture by weight of proline and glucose was investigated at high temperatures (600–840 °C) and short residence time (i.e. 1.0 s) in an inert atmosphere to determine if glucose or Maillard reaction products enhance the formation of nitrogen containing polycyclic aromatic compounds (N-PACs) and polycyclic aromatic hydrocarbons (PAHs) in the pyrolysis of proline. To study the gas-phase formation of N-PACs and PAHs, the substrates were sublimed into the pyrolysis furnace at 460 °C. Thermogravimetric analysis showed that glucose, the proline/glucose mixture, and the proline Amadori compound undergo solid-state decomposition reactions before subliming. Thus, the substrates were pyrolyzed in two stages: at 460 °C during the sublimation and at 600–840 °C. At 800 °C with a residence time of 1.0 s, proline produced low yields of N-PACs, such as quinoline, isoquinoline, indole, acridine, and carbazole, and PAHs, such as phenanthrene, pyrene, benz[ a]anthracene, benzofluoranthene isomers, and benzo[ a]pyrene. Increasing the temperature and residence time increased the yield of these products. Under similar pyrolysis conditions, the proline Amadori compound produced 2–8 fold more N-PACs and PAHs than proline. A 1:1 mixture of proline and glucose produced a similar slate of pyrolysis products as the proline Amadori compound, but it is unclear whether the proline Amadori compound was an intermediate in the reaction. In general, the proline Amadori compound produced a higher yield of N-PACs and PAHs than the proline/glucose mixture, but glucose clearly enhances the low temperature gas-phase formation of N-PACs and PAHs from the pyrolysis of proline. For example, a 1:1 mixture of proline and glucose was found to produce low yields of quinoline, isoquinoline, and indole at 600 °C while proline alone does not produce these compounds until 800 °C. Thus, glucose provides a low temperature pathway for the decomposition of proline, which leads to formation of N-PACs and PAHs.

Comparative Study on Polycyclic Aromatic Hydrocarbons, Light Hydrocarbons, Carbon Monoxide, and Particulate Emissions from the Combustion of Polyethylene, Polystyrene, and Poly(vinyl chloride)

A laboratory-scale study was performed to compare the emissions of pollutants from the batch combustion of polystyrene (PS), polyethylene (PE), and poly(vinyl chloride) (PVC) and to examine the conditions that minimize them. Fixed beds of polymer particles were burned in a two-stage, preheated muffle furnace, using air at atmospheric pressure. The temperature of the primary furnace was varied over a range of 500−1000 °C, to identify its influence on the emission of pollutants. The combustion effluent was mixed with additional preheated air, channeled to a secondary muffle furnace (afterburner), which was operated at 1000 °C. Emissions of CO, CO2, light hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and particulates were monitored either on-line or by sample collection, followed by gas chromatographic analysis. Emission magnitudes and trends were found to be dependent on the type of the polymer burned. The combustion of PS produced the largest yields of PAHs and, especially, soot; PE produced the n...

Seasonal variation of solvent extractable organic compounds in the aerosols in Qingdao, China

The solvent extractable organic compounds in 22 seasonal total suspended particulate samples collected in Qingdao, China during June 2001–May 2002 were analyzed using gas chromatograph/mass-selective detector. Included in these samples were three from Asian dust episodes. The characteristics and abundance of the n-alkanes, polycyclic aromatic hydrocarbons and fatty acids were determined. Distinct seasonal variations were detected in the Qingdao samples. The n-alkanes were found to contain substantial amounts of petroleum residues (56.0% in summer, 64.4% in fall, 77.6% in spring and 81.5% in winter). The winter polycyclic aromatic hydrocarbons (PAHs) were from combustion sources including coal burning for space-heating and the average PAH yield was 14.4 times higher than that in summer. The <C 20 homologues, mainly from kitchen emissions and microbial origins, dominated the fatty acid fraction and they constituted 72.8%, 81.9%, 86.9% and 92.6% of the winter, spring, fall and summer samples, respectively. The three Asian dust episode samples possessed characteristics typical of long-distance transport samples with Cmax at C 29 and C 31 and relatively high carbon preference index values (l.85–2.37) for the alkanes, and high plant wax content (38.7–45.5%) in the fatty acids even though the total yields were not substantially larger.

Pesticides, Polycyclic Aromatic Hydrocarbons, and Polychlorinated Biphenyls in Transport in Two Atlantic Coastal Plain Tributaries and Loadings to Chesapeake Bay

Concentrations of current-use pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine (OC) insecticides were determined above the reach of tide in the Chesterville Branch and Nanticoke River on the eastern shore of Chesapeake Bay during base-flow and storm-flow hydrologic regimes to evaluate mass transport to Chesapeake Bay. The two rivers monitored showed relatively high concentrations of atrazine, simazine, alachlor, and metolachlor in comparison to previously investigated western shore tributaries, and reflected the predominant agricultural land use in the eastern shore watersheds. The four current use pesticides showed the greatest seasonal contribution to annual loadings to tidal waters of Chesapeake Bay from the two rivers, and the relative order of annual loadings for the other contaminant classes was PAHs>PCBs>OC insecticides. Annual loadings normalized to the landscape areas of selected Chesapeake Bay watersheds showed correlations to identifiable source areas, with the highest pesticide yields (g/km2/yr) occurring in eastern shore agricultural landscapes, and the highest PAH yields derived from urban regions.

Low temperature mechanism for the formation of polycyclic aromatic hydrocarbons from the pyrolysis of cellulose

The formation of polycyclic aromatic hydrocarbons (PAHs) from the pyrolysis of cellulose over the temperature range of 300–650 °C has been investigated. Detectable amounts (microgram per gram) of 2–4 ring PAHs were observed at and above 400 °C. Benzo[a]pyrene and benz[a]anthracene were observed at and above 500 °C. Changing the gas phase residence time from 2 to 18 s and the sample size from 200 to 500 mg did not significantly affect the yields of PAHs formed over this low temperature range. The addition of oxygen to the carrier gas stream significantly reduced the yields of PAHs. The pathway to PAH formation in the 300–650 °C temperature range is believed to proceed via the carbonization process where the solid residue undergoes a chemical transformation and rearrangement to give a more condensed polycyclic aromatic structure. The evolution profiles of PAHs from the solid residue suggests that smaller 2–3 ring PAHs evolve first and pass through a maximum at a slightly lower temperature than the larger 4–5 ring PAHs. The yields of PAHs obtained from the pyrolysis of d-glucose and sucrose are comparable to those obtained from cellulose.

Effect of pyrolysis conditions on the formation of polycyclic aromatic hydrocarbons (PAHs) from polyphenolic compounds

Effect of pyrolysis conditions, such as temperature and substrate composition, i.e. inorganics, on the formation of polycyclic aromatic hydrocarbons (PAHs) from polyphenolic compounds, chlorogenic acid (CA) and lignin, was studied under inert atmosphere. Two routes for the PAH formation were investigated: primary volatile tar and the solid residue, i.e. char. The reactor consisted of a quartz tube with two zones. Zone 1 was used to first pyrolyze the substrate at 250–400 °C to produce a low temperature tar (LTT) and then to pyrolyze the char at 625 °C to produce a high temperature tar (HTT), The LTT and HTT were then passed through zone 2 maintained at temperatures between 700 and 920 °C. Yields of most PAHs increased with temperature, except in a few cases where the yields of two- and three-ring PAHs exhibited a maximum at 870 °C. The maximum may be due to the growth of these PAHs into heavier PAHs. The partial removal of sodium and potassium from lignin decreased the formation of char and PAHs, co-pyrolysis of CA and lignin also altered the PAH distribution. Preliminary analysis of the data from CA gave high activation energies for the PAH formation, with activation energy generally increasing with the PAH size.

Influence of steroid structure on the pyrolytic formation of polycyclic aromatic hydrocarbons

It is well known that polycyclic aromatic hydrocarbons (PAHs) are formed from the pyrolysis of biomass, but the precursors and pathways that lead to PAHs are not well characterized. In this investigation, the flash vacuum pyrolysis (FVP) and the atmospheric pressure flow pyrolysis of a series of structurally different plant steroids, including stigmasterol, stigmasteryl acetate, β-sitosterol, stigmasta-3,5-diene, cholesterol, cholesteryl acetate, dihydrocholesterol, and ergosterol was investigated at 700 °C to determine the impact of steroid structure on the formation of three, four, and five ring PAHs. FVP of the steroids revealed that PAHs, such as phenanthrene, anthracene, pyrene, chrysene, benz[a]anthracene and their monomethylated derivatives, were formed by a series of unimolecular reactions, and the PAH yields were dependent upon the steroid structure. PAH yields were most sensitive to the number of double bonds in the steroid B-ring. Ergosterol (two double bonds) produced 13-fold more PAHs than dihydrocholesterol (no double bonds) in FVP experiments and 4-fold more PAHs in the flow pyrolysis experiments. Increasing the temperature from 700 to 800 °C in the FVP experiments only slightly increased the PAH yields for dihydrocholesterol relative to cholesterol, but the yield of small aromatic hydrocarbons, such as benzene and toluene, increased approximately 2-fold. Small increases in PAH yields (10–40%) were found in the FVP experiments if a double bond was placed in the steroid A-ring by 1,2-elimination of an ester (as for cholesteryl acetate), but this trend was not observed in the flow pyrolysis experiments. Insight into the structural origins of the PAHs was gained by FVP of [4- 13C]cholesterol, in which the 13C content of the products were determined by mass spectrometry. The PAH yields from the flow pyrolysis of steroids esterified with saturated and unsaturated long chain fatty acids, i.e. cholesteryl stearate, cholesteryl oleate, and cholesteryl linolenate, were 20–40% lower (per gram of steroid) than the free steroid. The yield of three to five ring PAHs did not correlate with the number of double bonds in the ester chain, but the yield of benzene increased as the number of double bonds in the ester chain increased. In general, this investigation has shown that structural differences in steroids can significantly alter the PAH yields formed from the vacuum pyrolysis or atmospheric pressure pyrolysis of steroids.

Mechanistic investigation into the formation of polycyclic aromatic hydrocarbons from the pyrolysis of plant steroids

There have been many studies on the pyrolysis of biomass model compounds but most have not been performed under the high heating rate, short residence time conditions currently used in the thermochemical conversion of biomass. In this investigation, the pyrolysis of plant steroids is investigated by flash vacuum pyrolysis (FVP) and flow pyrolysis at residence times of 0.1–2.0 s and temperatures of 550–800°C to determine if the native cyclic ring structure in the steroid leads to the formation of polycyclic aromatic hydrocarbons (PAHs) or whether PAHs are formed by pyrosynthesis. FVP of stigmasterol, stigmasterol acetate, β-sitosterol, and stigmasta-3,5-diene at 700°C showed that PAHs, such as acenaphthylene, phenanthrene, anthracene, pyrene, chyrsene, benz[ a]anthracene, and their monomethylated derivatives were formed in the absence of bimolecular reactions, and the yield of PAHs was dependent of the structure of the steroid. Similar products were found in the flow pyrolysis of stigmasterol, and the yields of PAHs were found to increase with increasing temperature and residence time. Thermochemical kinetic estimates were used to postulate pathways for the formation of the primary pyrolysis products.

An experimental investigation into the formation of polycyclic-aromatic hydrocarbons (PAH) from pyrolysis of biomass materials

The formation of polycyclic-aromatic hydrocarbons (PAH) from the pyrolysis of cellulose, pectin, and chlorogenic acid was studied. The primary product, mostly primary volatile tar, was exposed to a higher thermal severity, i.e. high temperatures and long residence times. The reactor setup consisted of a quartz tube with two zones, zone I and II, each heated and controlled separately. Zone I was used to first pyrolyze the substrate at 300°C to produce a low temperature tar (LTT) as well as to pyrolyze the product char at 600°C to produce a high temperature tar (HTT). The LTT and HTT were then subjected to a high thermal severity in the second zone (zone II) where the temperature was varied between 700 and 850°C. The residence time of the volatiles in zone II was varied between ca. 90 and 1400 ms (calculated at 800°C). The results showed that the yield of most PAHs increased with temperature, except in a few cases where the yield of two- and three-ring PAHs exhibited a maximum. PAHs yields also generally increased as the residence time was increased from 90 to 1400 ms at 800°C.

Polycyclic aromatic hydrocarbon and particulate emissions from two-stage combustion of polystyrene: the effect of the primary furnace temperature.

A study is presented on laboratory-scale combustion of polystyrene (PS) to identify staged-combustion conditions that minimize emissions. Batch combustion of shredded PS was conducted in fixed beds placed in a bench-scale electrically heated horizontal muffle furnace. In most cases, combustion of the samples occurred by forming gaseous diffusion flames in atmospheric pressure air. The combustion effluent was mixed with additional air, and it was channeled to a second muffle furnace (afterburner) placed in series. Further reactions took place in the secondary furnace at a residence time of 0.7 s. The gas temperature of the primary furnace was varied in the range of 500-1,000 degrees C, while that of the secondary furnace was kept fixed at 1,000 degrees C. Sampling for CO, CO2, O2, soot, and unburned hydrocarbon emissions (volatile and semivolatile, by GC-MS) was performed at the exits of the two furnaces. Results showed that the temperature of the primary furnace, where PS gasifies, is of paramount importance to the formation and subsequent emissions of organic species and soot. Atthe lowesttemperatures explored, mostly styrene oligomers were identified at the outlet of the primary furnace, but they did not survive the treatment in the secondary furnace. The formation and emission of polycyclic aromatic hydrocarbons (PAH) and soot were suppressed. As the temperature in the first furnace was raised, increasing amounts of a wide range of both unsubstituted and substituted PAH containing up to at least seven condensed aromatic rings were detected. A similar trend was observed for total particulate yields. The secondary furnace treatment reduced the yields of total PAH, but it had an ambiguous effect on individual species. While most low molecular mass PAH were reduced in the secondary furnace, concentrations of some larger PAH increased under certain conditions. Thus, care in the selection of operating conditions of both the primary furnace (gasifier/ burner) and the secondary furnace (afterburner) must be exercised to minimize the emission of hazardous pollutants. The emissions of soot were also reduced in the afterburner but not drastically. This indicates that soot is indeed resistant to oxidation; thus, it would be best to avoid its formation in the first place. An oxidative pyrolysis temperature of PS in the vicinity of 600 degrees C appears to accomplish exactly that. An additional afterburner treatment at a sufficiently high temperature (1,000 degrees C) may be a suitable setting for minimization of most pollutants. To obtain deeper understanding of chemical processes, the experimental results were qualitatively compared with preliminary predictions of a detailed kinetic model that describes formation and destruction pathways of chemical species including most PAH observed in the present work. The modeling was performed forthe secondary furnace assuming plug-flow conditions therein. The experimentally determined chemical composition at the outlet of the primary furnace was part of the input parameters of the model calculation.

Vaporous and particulate‐bound polycyclic aromatic hydrocarbons in Chinese incense smoke

In this study, we determined polycyclic aromatic hydrocarbons (PAHs) in incense smoke by high performance liquid Chromatograph equipped with a fluorescence detector. The total yield of PAHs was 94.07 ug to 111.65 μg per gram incense burned and varied with four kinds of incenses. All vaporous PAHs were those with molecular weight (MW) less than 202.26, the MW of pyrene. Naphthalene composed 95–98% of the total vaporous PAHs. Although a greater amount of the particulate‐bound PAHs (83–92%) is also attributed to those with MW less than 202.26, the small amount of particulate‐bound PAHs with MW greater than 202.6 was also observed.

Effects of various binary and ternary supercritical phases on the extraction of polycyclic aromatic hydrocarbons from contaminated soils

Polycyclic aromatic hydrocarbons (PAHs) were extracted from two real environmental soil samples using supercritical fluid extraction (SFE) with organic modifiers. The modifiers ( n-pentane, acetone, toluene, dichloromethane, methanol) as well as modifier mixtures (methanol containing acetone, toluene, acetic acid; acetone containing toluene, ethanolamine; n-pentane containing acetic acid) were used in two different concentrations. In general, extraction efficiency increased with reduced polarity of the modifier used and at higher concentrations of co-solvent. Extraction of PAHs from the minor polluted soil with a high content of humic acids was enhanced greatly by the use of modifiers in comparison with pure CO 2 and Soxhlet extraction utilising dichloromethane or n-pentane. The highest PAH yields were received with CO 2 containing 10 or 2 mol% pentane followed by CO 2 with 10 mol% toluene. In contrast, for the soil highly contaminated with mineral oil products but with a low content of humic substances, the extraction efficiency was only increased a little by the addition of modifiers in comparison with pure CO 2 and decreased in comparison with Soxhlet extraction. The results lead to the conclusion that the use of modifiers during SFE is well appropriated to break strong matrix–analyte interactions, like humic acids–PAH interactions in the low contaminated soil. But for soils highly contaminated with aliphatic hydrocarbons, SFE is less suitable, because of the viscosity and solubility of the hydrocarbons for PAHs.

Combined modifier/in situ derivatization effects on supercritical fluid extraction of polycyclic aromatic hydrocarbons from soil

Supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs) from a real environmental soil sample containing a high content of humic acids was enhanced by using modifier and in situ derivatization. The addition of 10 mol% methanol increased the ability of the supercritical CO 2 (recovery set to 100%) to displace PAHs from matrix active sites up to an average value of 145%. In situ derivatization was performed under dynamic SFE conditions using boron trifluoride (BF 3) in methanol as modifier. Comparing the results of the SFE extraction with methanol and with BF 3 in methanol showed that the addition of BF 3 increased the PAH recoveries further. Increasing BF 3 concentration gave higher extraction yields of PAHs. A second SFE of the same sample with CO 2–methanol improved the average extraction yield for only 2%, whereas a second SFE of a CO 2–methanol extracted sample with CO 2–methanol–BF 3 increased the average yield for 18%. Especially the recoveries of the penta- and hexacyclic PAHs were increased by the addition of BF 3. The results indicate that the strong Lewis acid BF 3 cleave humic substances of the matrix releasing aromatic acids in the extract which were detected by HPLC–diode array detection. As a result of this PAHs associated to the matrix were also released in the extract.

Comparison of the yield of polycyclic aromatic hydrocarbons in smoke from Japanese tobacco.

The smoke condensates of Japanese cigarette, cigar and pipe tobacco were quantitatively analysed for polycyclic aromatic hydrocarbons. The amount of benzo[a]pyrene was 4.8, 2.7 and 11.6μg/100g, respectively. These results alone are insufficient to explain the epidemiological correlation between tobacco smoking and lung cancer.