effect of gasoline and lubricant on emissions and mutagenicity of particles and semivolatiles in...

Effect of Gasoline and Lubricant onEmissions and Mutagenicity ofParticles and Semivolatiles in ChainSaw ExhaustR O G E R M A G N U S S O N * A N DC A L L E N I L S S O NChemistry and Biomass, Department of Agricultural Researchfor Northern Sweden, Swedish University of AgriculturalSciences, P.O. Box 4097, SE-904 03 Umea, Sweden

K U R T A N D E R S S O N † A N DB A R B R O A N D E R S S O N ‡

Center for Musculoskeletal Research, National Institute forWorking Life, P.O. Box 7654, SE-907 13 Umea, Sweden, andEnvironmental Chemistry, Department of Chemistry,Umea University, SE-901 87 Umea, Sweden

U L F R A N N U G

Department of Genetic and Cellular Toxicology,Wallenberg Laboratory, Stockholm University,SE-106 91 Stockholm, Sweden

C O N N Y O S T M A N

Department of Analytical Chemistry, Stockholm University,SE-106 91 Stockholm, Sweden

The exhaust from a two-stroke chain saw engine wascharacterized using two different types of gasoline, aliphaticgasoline and conventional lead-free gasoline, in combinationwith four lubricants differing in mineral oil, polyolester,and polyisobutylene (PIB) content. This characterization wasfocused on emissions of polycyclic aromatic hydrocarbons(PAH) and mutagenicity testing using Ames Salmonellaassay. In addition, exhaust emissions of carbon monoxide(CO), nitrogen oxides (NOx), aldehydes, and hydrocarbons(HC) were measured. The two-stroke engine was tested ina test bench, and particulate, semivolatile, and gaseousexhaust components were sampled using a dilution tunnel.Much less PAH were emitted when using aliphaticgasoline due to a much lower gasoline content of PAHand aromatics than the conventional gasoline. Also abouthalf the NOx emissions, up to 50% higher formaldehydeand acetaldehyde emissions, and 10% higher total HCemissions were observed for the aliphatic gasoline. Theinfluence of lubricant on the studied exhaust emissions wasfound to be of minor importance. In terms of mutagenicity,significant effects were seen for six of the eight gasoline/lubricant combinations, and the highest effects were observedwithout a metabolizing system. Generally, the conventionalgasoline gave higher effects than did the aliphaticgasoline. A difference between lubricants was also seen,especially in combination with gasoline A; however, theinterpretation of mutagenic effects of the lubricants was notstraightforward. Overall, one synthetic ester-basedlubricant and one mineral oil-based lubricant gave thehighest mutagenicity.

IntroductionSmall hand-held utility machines such as chain saws, grasstrimmers, and hedge trimmers are often equipped with two-

stroke engines due to their high power to weight ratio.However, their high output of unburned fuel due toscavenging losses is in the range of 30% of the fuelconsumption. This leads to severe problems for the user,especially when the machines are used professionally.Complaints about irritation of the upper respiratory tractand eyes as well as fatigue and headache are commonproblems (1, 2).

In an earlier study, we primarily addressed the problemswith acute effects and recommended a new type of gasolinefor use in hand-held utility machines (3). This gasolineconsisted of only aliphatic saturated hydrocarbons (HC) ascompared to conventional Swedish gasoline, which contains30-50% aromatics and 2-15% olefins. On the basis of thatstudy, a Swedish standard was adopted for this gasoline in1995 (4).

The fuel for simple two-stroke engines such as thesecontains 1-2% of lubricant. The traditional mineral oil usedis now partly or totally replaced by various synthetic basestocks such as polyisobutylene and esters of various types,and for some applications, vegetable oils are used. Apartfrom the base stocks, additives are also used to improvetemperature stability, pressure stability, and chemical stabilityof the lubricating oil.

During ideal combustion in air, only carbon dioxide,nitrogen oxides, and water are formed. During actualcombustion, however, a large number of other compoundsare formed. One group of compounds formed is polycyclicaromatic hydrocarbons (PAH) that are formed mainly dueto incomplete combustion. Many PAH have been identifiedas carcinogenic to rodents and are classified by the Inter-national Agency for Research on Cancer (IARC) as probablyor possibly carcinogenic to human beings (5). Studies haveshown that PAH in experimentally diluted exhaust gas areboth particulate and gas-phase associated (6, 7). Othercompounds in the exhaust gas that are also human healthrisks or environmental pollutants are carbon monoxide(CO), nitrogen oxides (NOx), HC, and aldehydes. It is well-established that gasoline engine exhaust contains genotoxiccomponents; the IARC has classified gasoline engine exhaustas possibly carcinogenic to human beings (8). A study ofexposure to the exhaust from two-stroke outboard enginesshows that the exhaust can cause disruption of normalbiological functions of living fish (9).

In a review by McGinty and Dent (10) concerning four-stroke engines, it is shown that the gasoline compositioninfluences the emission of PAH and also the emission ofother exhaust components. For two-stroke engines, a gasolinecomposition dependency of PAH emissions (11, 12) and otherexhaust components (3, 13, 14) is also observed. The choiceand mixing ratio of lubricant might also influence the PAHexhaust emissions. This matter has been studied by bothCosmacini et al. (11) and Laimbock (12) but with differentresults. For simple two-stroke engines, the lubricant is addeddirectly to the gasoline, and scavenging losses can give about30-40% unburned oil in the exhaust gas (12). Furthermore,the lubricant as well as the gasoline may affect the mutage-nicity and carcinogenicity of the exhaust. Some types ofmineral oils, for example, are carcinogenic to human beings(15). However, for two-stroke engines the influence of gasolineand lubricant on PAH emissions and mutagenicity of the

* Corresponding author phone: +46(0)907869495; fax: +46(0)-907869404; e-mail: [email protected].

† National Institute for Working Life, deceased.‡ Umeå University and National Institute for Working Life.

Environ. Sci. Technol. 2000, 34, 2918-2924

2918 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 34, NO. 14, 2000 10.1021/es9912022 CCC: $19.00 2000 American Chemical SocietyPublished on Web 06/16/2000

exhaust is an area that has been dealt with only to a limitedextent.

In an earlier publication (16), we studied mainly thereproducibility in mutagenicity and emissions of PAH, CO,NOx, HC, and aldehydes when sampling chain saw exhaustand made a comparison between two fuels. In this study, wehave extended the study to comprise eight fuels: conventionalgasoline and aliphatic gasoline combined with four differentlubricating oils chosen to cover the base stocks on the market.This was done in order to screen for differences in mutageniceffects between the various fuels and to find possiblecorrelation to PAH emissions.

Experimental SectionChain Saw. The chain saw used during all measurementswas a new Husqvarna 242 XP (Husqvarna AB, Husqvarna,Sweden) with a displacement of 41.6 cm3 and a maximumpower output of 2.4 kW at 9900 rpm. The saw was used inits original configuration with a few exceptions. The guidebar and chain were removed (since the saw was mounted ina test bench), and instead of using the original tank, the fuelwas led directly to the carburetor through a glass buret, wherethe fuel consumption was measured. A stainless steel funnelwas mounted at the silencer blow off in order to lead all theexhaust gas into a dilution tunnel.

Fuels. Eight different fuels were used, which consisted oftwo different types of gasoline combined with four differentlubricating oils. The two different types of gasoline used were95 octane aliphatic gasoline (gasoline A) and regular 95 octanelead-free gasoline (gasoline B). The composition of gasolineA was according to a Swedish Standard (4). The chemicaland physical properties of the two types of gasoline are givenin Table 1. The lubricants used in the tests where chosen torepresent different types of base stocks on the market. Oil1 and oil 2 were different types of ester-based synthetic oils,and oil 1 was claimed to be biodegradable. Oil 3 had a highcontent of polyisobutylene (PIB), and oil 4 was a traditionalmineral oil. The compositions of the lubricants are presentedin Table 2. The lubricants were mixed with the gasoline inan amount of 1.7 vol % (lubricant solvent excluded).

Exhaust Dilution and Experimental Procedure. Thechain saw was mounted on a stationary test bench, equippedwith an eddy current dynamometer, during the exhaustsampling and was run applying a constant load at 9000 rpm,giving a power output of 2.1 kW. Since the fuel/air mixing

ratio has a large effect on emissions (2), the carburetor settingwas adjusted so that a constant CO emission of 3.0% wasobtained. Before the exhaust sampling was started, the chainsaw was run on the test bench for about 1 h in order toachieve stable test conditions.

All exhaust sampling was made from diluted exhaust gas.In addition, CO was analyzed from raw exhaust gas. However,all emission data given in this paper show concentrationscalculated for raw exhaust gas. The dilution tunnel usedconsisted of a 4 m long stainless steel tube with an i.d. of 200mm and was connected to the saw through a flexible tube.A multi-hole probe for the measurement of the CO emissionin the raw exhaust gas was positioned at the dilution tunnelexhaust inlet. Three stainless steel probes inside the dilutiontunnel were used for isokinetic sampling of particles andsemivolatiles. Five more stainless steel probes were used forsampling of aldehydes, HC, CO, and NOx. The whole testingarrangement is described in detail in an earlier publication(16). For each fuel, one sampling run was performed whereparticles and semivolatiles were sampled in triplicate for 2h. During this 2-h period, emissions of CO and NOx andtemperatures were measured in intervals of 5 min, aldehydesand HC were sampled in duplicate three times, and the fuelconsumption was measured three times. Between eachsampling run, the dilution tunnel and sampling probes werecleaned with isooctane (Merck, p.a.) to eliminate depositsfrom previous emission tests. After being cleaned, the tunnelwas ventilated with air for at least 2 h.

Temperatures, Flow, and Dilution Ratio. Temperatureswere measured by thermocouples (chromel/alumel, type K,Pentronic AB, Gunnebo, Sweden) at four points: in thedilution air, at the cylinder of the engine, in the dilutiontunnel exhaust inlet, and in the diluted exhaust near theparticle sampling probes. The airflow through the dilutiontunnel was measured to 0.6 m3/min by a thermo-anemometer(GGA-65, Alnor Oy, Turku, Finland), and the raw exhaust gasflow was calculated to 0.2 m3/min giving a dilution ratio ofabout 4 (total flow divided by raw exhaust gas flow). Theexact dilution ratio for each sampling run was calculated bydividing the CO concentration in the raw exhaust gas by theCO concentration measured in the diluted exhaust gas.

Carbon Monoxide and Nitrogen Oxides. The emissionof CO was measured by an IR instrument (HC/CO testermodel 590, Beckman). The emission of NOx was measuredby a chemiluminescence instrument (nitrogen oxides ana-lyzer model 8440E, Monitor Labs, Englewood, CO). Waterwas separated from the exhaust before measurement bymeans of a Peltier gas cooler (ECP 1000, M & C ProductsAnalysentechnik GmbH, Ratingen, Germany).

Aldehydes. Aldehydes were sampled from diluted exhaustgas using two parallel impingers containing a solution of2,4-dinitrophenylhydrazine in acetonitrile (Rathburn, HPLCgrade) at a flow of approximately 1.0 L/min for 20 min. Thealdehyde-2,4-dinitrophenylhydrazones formed were thenanalyzed by high-performance liquid chromatography (HPLC)using a Hewlett-Packard 1100 series HPLC system. A C18

column (ODS Hypersil 5 µm, 100 × 2.1 mm, Hewlett-Packard)was used eluted with a methanol:water gradient program.

TABLE 1. Chemical and Physical Properties of the Two Typesof Gasoline Used in the Study

property methodgasoline

Agasoline

B

octane no. (research) D2699 95 95.5octane no. (motor) D2700 91.5 85density (15 °C), g/mL ASTM-D4052 0.686 0.739vapor pressure, kPa A-D5191 56 91.5distillation

initial boiling point, °C ASTM-D86 40 3410% recovered, °C ASTM-D86 58 4550% recovered, °C ASTM-D86 101.5 9590% recovered, °C ASTM-D86 111 158final boiling point, °C ASTM-D86 125.5 196

aromatic content, % v/v SS 155120 0.1 34.3benzene, % v/v SIS 155136 0.1 2.05

olefin content, % v/v ASTM-1319 0.1 10.2sulfur content, mg/kg A-D5453 2.3 17energy content (LHV),

MJ/kgSS 155138 44.5 43.8

sum of 20 PAH,a mg/L 0.13 99a The same PAH compounds as analyzed in the exhaust emissions.

For analytical method, see the section Polycyclic Aromatic Hydrocarbons.

TABLE 2. Main Components of Lubricating Oils Used in theStudy

component (%) oil 1 oil 2 oil 3 oil 4

mineral oil - - ∼25 82polyolester 46 30 - -PIBa ∼24 40 ∼45 -additive package ∼5 4.4 ∼5 4.8solvent 25 25 ∼25 13a Polyisobutylene or polybutene.

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The sampling and analysis of aldehydes is described in detailelsewhere (16).

Hydrocarbons. HC were sampled from diluted exhaustgas using two parallel charcoal sampler tubes (no. 226-09,8 × 110 mm, 200 + 400 mg of sorbent, Scantec, Partille,Sweden) based on a NIOSH method (17). The exhaust waspumped through the sample tubes at a flow of approximately60 mL/min for 5 min. All sampling tubes were stored at -18°C and isolated from light until analysis. Desorption of thesampling tubes was done by 3 mL of carbon disulfide (Merck,p.a.), and HC were analyzed by gas chromatography-massspectrometry (GC-MS) using a Hewlett-Packard 6890 seriesGC system gas chromatograph and a Hewlett-Packard 5973mass selective detector mass spectrometer. A 30 m × 0.25mm i.d. column coated with a 0.25-µm film of 5% diphenyl-95% dimethylsiloxane (HP-5MS, Art. No. 19091S-433, Hewlett-Packard) was used. Helium was used as carrier gas at a flowof 0.9 mL/min. The oven temperature was maintained at 30°C for 3.5 min after injection and then programmed asfollowed: an increase by 20 °C/min to 50 °C and held therefor 6 min, an increase by 20 °C/min to 70 °C, followed by afurther increase by 40 °C/min to 140 °C and held there for5 min. The injection temperature was 180 °C. Quantificationof individual HC was performed with standard solutions ofisopentane (Merck, p.a.), isooctane (Merck, p.a.), and toluene(Merck, p.a.) in carbon disulfide. Quantification of total HCwas performed with standard solutions of the two types ofgasoline in carbondisulfide.

Sampling and Sample Preparation for PAH Determi-nation and Mutagenicity Testing. Particles and semivolatilecompounds were sampled according to a method describedearlier (16, 18) where the diluted exhaust gas is pumpedthrough samplers with a flow of approximately 2.9 L/min fora period of 2 h. Each sampler contained a glass fiber filter(25 mm binder-free A/E filter, Gelman Sciences, Ann Arbor,MI) and two cylindrical polyurethane foam plugs (PUF) (15× 15 mm, Specialplast, Gillinge, Sweden) arranged in series.Three parallel samplers were connected to three samplingprobes positioned inside the dilution tunnel. Each filter andeach PUF were separately Soxhlet extracted with dichlo-romethane (Merck, p.a.). Each extract was divided in twoparts, 20% for PAH analysis and 80% for mutagenicity testing;the solvent was changed to cyclohexane (Merck, p.a.) for thePAH extracts and to dimethyl sulfoxide (DMSO) (Merck, p.a.)for the extracts for mutagenicity testing. The sample prepa-ration procedure is described in detail elsewhere (16).

Polycyclic Aromatic Hydrocarbons. The PUF and filterextracts, respectively, were cleaned up and analyzed ac-cording to Ostman et al. (19) with some modifications, using

a fully automated system consisting of a liquid chromato-graph (LC) coupled on-line to a gas chromatograph (GC) bymeans of a loop-type interface. By using a back-flushtechnique in conjunction with a nitrophenyl propyl silicacolumn (Nucleosil NO2, 75 × 4 mm, dp ) 5 µm, Macherey-Nagel, Duren, Germany), PAH were isolated by LC. Aconcurrent solvent evaporation (CSE) injection techniquewas used for on-line transfer of the isolated PAH fractionto the GC, where a DB-5 column (28 m × 0.32 mm, df )0.25 µm, 5% phenyl poly(dimethylsiloxane) gum, J&WScientific) was used. The PAH compounds eluted from theGC column were detected by a flame ionization detector(FID). Twenty different PAH compounds were analyzed (seeTables 5 and 6).

Mutagenicity. The PUF and filter extracts were separatelytested for mutagenicity using Salmonella typhimurium strainsTA 98, TA 100, and TA98NR according to Maron and Ames(20) with a slight modification in which histidine and biotinwere added to the minimal medium instead of the top agar.A liver preparation (S9) from Aroclor-treated male Sprague-Dawley rats was used (TA98NR excluded) as a metabolizingsystem in an amount of 50 µL/plate. Each Soxhlet extractwas tested at three dose levels, which together with the solventcontrol (zero dose) gave four dose levels per extract,corresponding to 0, 2.2, 4.4, and 8.8 L of diluted exhaust,respectively. Each dose was analyzed in triplicate. Addition-ally, benzo[a]pyrene was used as a positive control. The dose-response curve for each extract was checked for linearity,and only the linear portion was used for further calculations,which means that for a few extracts the highest dose wasexcluded, still giving three doses for further calculations. Alldata points from the three extracts from the same samplingrun were then combined in a common dose-response curve.This was done for filters and PUFs, respectively. The responsewas calculated from this dose-response curve by linearregression, giving the slope in number of revertants per doseunit (liter of diluted exhaust gas) and its standard deviation.

Results and DiscussionTemperatures, fuel consumption, and gaseous emissions arepresented in Tables 3 and 4. Constant values were obtainedfor temperatures, dilution ratio, and CO during each samplingrun, showing that all fuels were tested under stable testingconditions. Low variation between tests shows that close tothe same test conditions were obtained for all fuels. A fuelconsumption of around 20 mL/min was observed when usinggasoline B as compared to around 21 mL/min for gasolineA, which merely reflects the difference in density and energycontent of the two types of gasoline (Table 1). Considering

TABLE 3. Temperatures, Fuel Consumption, and Concentration of Gaseous Emissions When Running the Chain Saw with 95Octane Aliphatic Gasoline (Gasoline A) Using Four Different Lubricating Oilsa

parameter unit oil 1 oil 2 oil 3 oil 4 nb

temp dilution air °C 19 (6) 19 (3) 18 (4) 18 (8) 23temp engine °C 257 (1) 281 (3) 262 (0) 257 (1) 23temp exhaust °C 282 (3) 288 (1) 291 (0) 276 (2) 23sampling temp °C 83 (3) 82 (1) 83 (1) 79 (1) 23fuel consumption mL/min 20.8 (0) 20.9 (2) 20.7 (1) 21.2 (2) 3dilution ratio 4.2 (6) 4.2 (8) 4.2 (4) 4.3 (6) 23CO % 3.1 (11) 3.0 (10) 3.1 (6) 3.1 (12) 23NOx ppm 180 (18) 230 (26) 210 (10) 240 (25) 23isopentane g/m3 3.9 (15) 3.6 (14) 4.1 (18) 3.8 (9) 6isooctane g/m3 5.7 (16) 4.9 (11) 5.4 (12) 5.5 (5) 6toluene g/m3 ndc - ndc - ndc - ndc - 6total HC g/m3 18 (16) 15 (11) 17 (12) 17 (5) 6formaldehyde mg/m3 270 (8) 400 (5) 260 (9) 320 (8) 6acetaldehyde mg/m3 67 (2) 69 (5) 52 (5) 63 (6) 6

a Concentrations are given for raw exhaust gas, and relative standard deviation is given in parentheses. b Number of measurements/samplesfor each run. c nd, not detected (<0.005 g/m3 toluene).

2920 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 34, NO. 14, 2000

the gaseous emissions, no specific trend for the differentlubricating oils could be found, but a difference was seenbetween the two types of gasoline. About half the NOx

emissions were observed for gasoline A as compared togasoline B, which may be a result of small differences incombustion temperature since aromatic HC have highercombustion temperatures than alkanes and NOx emissionsincrease with higher temperature. However, no overallsignificant difference in engine or exhaust temperature wasobserved. Hare and Carroll (14) and Nilsson (3) have alsoreported a similar reduction in NOx emissions when testingtwo-stroke engines with corresponding fuels. Lower NOx

emissions due to lower fuel aromatic content are alsoobserved in four-stroke engines (6, 21). A comparison in thesame way shows up to 50% higher formaldehyde andacetaldehyde emissions for gasoline A, which is supportedby earlier work on two-stroke (13, 14) and four-stroke engines(10, 22). About 10% higher emissions of total HC were alsoobserved for gasoline A. Lower NOx emissions indicate a lowercombustion temperature, which should give a higher HCemission. However, it should be kept in mind that for a two-

stroke engine, 90% of the HC emission can be due toscavenging losses (23) and should not be affected by thecombustion temperature. For two-stroke engines, Hare andWhite (13), and for four-stroke engines, Westerholm et al.(6), have shown a similar increase of HC emissions whendecreasing the aromatic content of the fuel, while Schuetzleet al. (21) show the opposite for four-stroke engines. Thetotal HC emission measured as mass of HC per mass of fuelconsumed gives a rough estimate of the scavenging lossesand was on average 22% for the eight fuels. The HC profileof the individual hydrocarbons measured clearly reflectedthe HC profile in the gasoline, which confirms the fact thatmost of the HC emission is due to scavenging losses.

Emission of PAH in the particulate phase and PAH amongthe semivolatile-associated components is shown in Tables5 and 6. For about 90% of the filter and PUF PAH measure-ments, the relative standard deviation of the three replicateswas between 0 and 40%. Overall, much less PAH were foundwhen using gasoline A. Considering total PAH emission, thehighest amount (around 3400 µg/m3) was found for oil 1 incombination with gasoline B and amounts around 2700 µg/

TABLE 4. Temperatures, Fuel Consumption, and Concentration of Gaseous Emissions When Running the Chain Saw with Regular95 Octane Lead-Free Gasoline (Gasoline B) Using Four Different Lubricating Oilsa

parameter unit oil 1 oil 2 oil 3 oil 4 nb

temp dilution air °C 19 (4) 19 (4) 18 (3) 19 (2) 23temp engine °C 287 (2) 283 (2) 249 (1) 277 (2) 23temp exhaust °C 281 (1) 288 (1) 283 (0) 287 (0) 23sampling temp °C 81 (1) 83 (1) 83 (1) 84 (1) 23fuel consumption mL/min 20.1 (1) 20.3 (1) 19.9 (1) 19.3 (0) 3dilution ratio 4.3 (9) 4.1 (7) 4.1 (3) 4.1 (4) 23CO % 3.0 (8) 3.1 (8) 3.0 (4) 3.1 (6) 23NOx ppm 430 (8) 380 (13) 370 (6) 520 (13) 23isopentane g/m3 1.7 (3) 1.6 (12) 1.8 (19) 1.6 (18) 6isooctane g/m3 ndc - ndc - ndc - ndc - 6toluene g/m3 1.7 (5) 1.5 (14) 1.7 (19) 1.6 (14) 6total HC g/m3 16 (6) 14 (14) 16 (19) 15 (14) 6formaldehyde mg/m3 280 (10) 260 (2) 230 (4) 240 (11) 6acetaldehyde mg/m3 53 (8) 46 (2) 41 (3) 41 (10) 6

a Concentrations are given for raw exhaust gas, and relative standard deviation is given in parentheses. b Number of measurements/samplesfor each run. c nd, not detected (<0.005 g/m3 isooctane).

TABLE 5. Emission of PAH (µg/m3) When Running the Chain Saw with 95 Octane Aliphatic Gasoline (Gasoline A) Using FourDifferent Lubricating Oilsa

oil 1 oil 2 oil 3 oil 4

PAH compound filter PUF filter PUF filter PUF filter PUF

phenanthrene 0.7 ndb 6.9 39 4.2 38 6.0 nd3-methylphenanthrene 0.4 nd 18 46 14 44 2.7 nd2-methylphenanthrene 0.4 nd 15 28 11 27 3.5 nd9+4-methylphenanthrenec 0.6 nd 6.0 12 5.3 15 4.0 nd1-methylphenanthrene 0.5 nd 7.7 17 7.1 17 3.5 nddimethyl-178:1d 0.5 nd 6.9 9.2 7.3 13 3.3 nddimethyl-178:2d 0.2 nd 7.4 9.5 7.9 11 1.0 nddimethyl-178:3d 0.3 nd 4.3 5.7 4.0 6.1 0.8 nddimethyl-178:4d 1.1 nd 12 17 14 21 4.6 nddimethyl-178:5d 0.6 nd 5.7 8.0 6.8 9.4 2.4 nddimethyl-178:6d 0.4 nd 3.9 5.1 4.1 5.6 1.8 nddimethyl-178:7d 0.7 nd 7.2 9.0 8.5 11 2.2 ndfluoranthene 0.8 nd 3.3 4.0 4.0 5.7 3.0 ndpyrene 1.0 nd 7.1 8.5 12 12 4.5 ndbenzo[a]fluorene nd nd 12 8.2 16 7.7 2.6 ndbenz[a]anthracene nd nd 5.6 0.5 7.1 0.5 0.7 ndchrysene/triphenylene nd nd 5.2 0.3 6.1 0.4 2.3 ndbenzofluoranthenes nd nd 1.2 nd 2.0 nd nd ndbenzo[e]pyrene nd nd 0.8 nd 1.1 nd 0.3 ndbenzo[a]pyrene nd nd 0.5 nd 0.7 nd 0.5 nd

sum of PAH 8.2 137 227 144 245 50a All numbers are given for raw exhaust gas and are means of three samples. b nd, not detected (<0.1 µg/m3). c May include 4,5-

methylenephenathrene. d 178 indicates an unidentified PAH compound with a molecular mass of 178 u.


m3 were observed for the other lubricants combined withgasoline B. However, the increase for oil 1 is due to 50-120%higher amounts of light PAH like phenanthrene and 2- and3-methylphenanthrene, while the heavier compounds thatare considered to be carcinogenic, such as benz[a]anthracene,benzo[a]pyrene, and benzofluoroanthenes (5), did notincrease. For gasoline A, however, the highest amounts (390and 360 µg/m3) were found for oils 3 and 2, respectively.Lower amounts (50 and 8 µg/m3) were observed for oils 4and 1, respectively. For these last two fuels, no PAH at allwere detected in the PUFs. An explanation to this might beslight partial absorption of semivolatile PAHs in the unburnedoil at the filter, which at these low PAH concentrationsimplicates a total absorption on the filters, preventing abreakthrough to the PUFs. For all other fuels, the greaterpart of the lighter molecular weight PAH was found in thePUFs while the larger molecular weight PAH were almostcompletely particle associated, which is in agreement withpreviously published results for four-stroke gasoline- (6, 24)and diesel-fueled engines (7).

The obvious difference in total PAH emissions betweenthe two types of gasoline is what would be expected, sincethe total PAH content in the fuelsif taking the same PAHcompounds into considerationswas 0.13 and 99 mg/L forgasolines A and B, respectively. Gasoline B also has a muchhigher content of aromatics than gasoline A. An increase inPAH emissions both when increasing the aromatic HCcontent of the fuel and when increasing the PAH content ofthe fuel has been observed for two-stroke (11) and four-stroke (10) gasoline engines. Assuming that no decompositionor formation of PAH occurs in the combustion processes, atotal PAH emission of 13 and 9700 µg/m3 in raw exhaust gaswould have been seen for gasolines A and B, respectively.Hence, for gasoline B the ratio between output and input ofPAH (output PAH divided by input PAH) is about 0.3independent of oil. However, the same comparison forgasoline A gives a ratio of about 0.6 for oil 1, a ratio of 4 foroil 4, and a ratio of 30 for oils 2 and 3. This is in agreementwith earlier studies (10) showing that at low fuel PAH levelsthe majority of PAH emitted is produced by combustionprocesses, while at high fuel PAH levels much of the PAH isdestroyed by combustion. Since 22% of the fuel remains

unburned due to scavenging losses, it is concluded that forgasoline B the gasoline PAH content is a more dominantPAH emission factor than the content of aromatics. This isalso confirmed by very similar PAH profiles in the gasolineand in the exhaust gas for gasoline B. Hence, when usinggasoline B the high gasoline content of PAH and aromaticstotally dominates the emission of PAH and probably over-shadows the contribution from the lubricating oils. Whenusing gasoline A, the influence of the lubricating oils becomesgreater due to low gasoline content of both PAH andaromatics. This would explain why the pattern of total PAHemission for the four lubricating oils differs between gasolineA and gasoline B; however, the pattern of total PAH emissionwhen using gasoline A is difficult to interpret because oils1 and 4, which gave the lowest emission, are syntheticrespective mineral oils. These two lubricants are of a differentchemical nature and were believed to be the best respectiveworst alternative concerning exhaust emissions.

It can be concluded that the choice of gasoline type is byfar the most important factor for the PAH emission, whilethe lubricating oils have no significant influence on the PAHemission when combined with gasoline B. This conclusionis in agreement with a study by Laimbock (12). However,when using gasoline with a low PAH content, like gasolineA, the choice of lubricating oil becomes more important forthe PAH emission, but still it is not evident from this studythat one specific type of lubricating oil gives lower PAHemission than another.

When comparing the magnitude of the PAH emissionswith previous results by Cosmacini et al. (11) from a 4.8-kWtwo-stroke Vespa engine with a displacement of 150 cm3,similar PAH concentrations are reported. Gasoline B is inconformity with the use of conventional leaded gasoline withmineral oil in the Cosmacini study, if omitting phenanthrene,which was found in 2-4 times higher amounts in the presentstudy. Cosmacini reports a 25% decrease in PAH emissionswhen changing to synthetic oil, a decrease not seen in ourstudy. Gasoline A, combined with oils 2 and 3, is in agreementwith the use of isooctane as fuel in the Cosmacini study.However, PAH values for gasoline A combined with oils 1and 4 are far below the values in the Cosmacini study.

TABLE 6. Emission of PAH (µg/m3) When Running the Chain Saw with Regular 95 Octane Lead-Free Gasoline (Gasoline B) UsingFour Different Lubricating Oilsa


PAH compound filter PUF filter PUF filter PUF filter PUF

phenanthrene 143 598 96 327 47 287 51 3163-methylphenanthrene 237 510 181 325 74 273 134 3272-methylphenanthrene 181 360 114 235 101 248 81 2309+4-methylphenanthrenec 67 68 50 101 37 100 48 881-methylphenanthrene 86 195 69 157 68 188 102 163dimethyl-178:1d 80 61 64 59 45 65 48 64dimethyl-178:2d 90 36 73 59 59 69 60 68dimethyl-178:3d 51 41 36 34 37 59 42 38dimethyl-178:4d 86 17 91 58 119 123 133 123dimethyl-178:5d 56 22 48 38 43 58 47 51dimethyl-178:6d 38 19 36 28 48 64 51 47dimethyl-178:7d 78 28 66 46 61 64 65 57fluoranthene 41 38 29 23 24 26 23 22pyrene 41 15 39 21 52 37 60 36benzo[a]fluorene 29 4.6 37 26 94 26 93 17benz[a]anthracene 15 ndb 15 nd 23 nd 24 ndchrysene/triphenylene 42 nd 31 nd 15 nd 19 ndbenzofluoranthenes 15 nd 12 nd 15 nd 14 ndbenzo[e]pyrene 18 nd 13 nd 16 nd 14 ndbenzo[a]pyrene 8.5 nd 9.1 nd 15 nd 14 ndsum of PAH 1400 2010 1110 1540 992 1690 1120 1650a All numbers are given for raw exhaust gas and are means of three samples. b nd, not detected (<0.1 µg/m3). c May include 4,5-

methylenephenathrene. d 178 indicates an unidentified PAH compound with a molecular mass of 178 u.


The results from the mutagenicity test are presented inTable 7. The reproducibility in mutagenicity for this samplingsetup has been discussed in an earlier publication (16). Asexpected rather poor reproducibility of the three replicateswas seen for effects being just on the borderline of thedetection limit of this method i.e., gasoline A combined withoils 2 and 3. However, much better reproducibility was seenwhere high effects were obtained. Significant mutageniceffects for TA98 and TA100 both with and without ametabolizing system were seen for all fuels, except for gasolineA combined with oils 2 and 3. As observed before for two-stroke engines (16) and for four-stroke gasoline-fueled (6,25) and diesel-fueled (7) engines, the highest effects areobtained in absence of a metabolizing system. For gasolineB, higher effects were observed for the particulate phase thanfor the semivolatile components, but for gasoline A theopposite was observed where the effects were significant.Earlier gasoline engine studies show higher mutagenicity forthe semivolatile components (6, 25). Taking all strains andboth filters and PUFs into consideration, the following fourgasoline/oil combinations showed high mutagenicity: A/oil1, A/oil 4, B/oil 1, and B/oil 2, of which B/oil 1 gave thehighest effects. Two other combinations, B/oil 3 and B/oil4, gave lower but significant mutagenic effects, while noeffects were seen for gasoline A combined with oils 2 or 3.For all lubricating oils except oil 4, higher mutagenic effectswere observed when combined with gasoline B than withgasoline A.

To give some sort of relative health risk assessment, whichwas the aim of this biological characterization, it can beconcluded that on the whole a lower risk is associated withgasoline A than gasoline B, which is in agreement with thePAH result. Furthermore, oil 3 seems to be the most preferablelubricant in contrast to oils 1 and 4, which are the leastpreferable. A high mutagenicity for oil 4, which is a traditionalmineral oil, was in agreement with our presumptions,although that was not as clear in combination with gasolineB. The even higher effects for oil 1, which is a syntheticlubricant that was thought to be a good alternative regardingexhaust emissions, was more spectacular though. However,since the mutagenicity data were difficult to interpret, furthertests using additional test systems are needed to confirmthese results.

Significant correlation for any of the strains could not befound between mutagenicity and amounts of total PAH foundin filters and PUFs for the eight fuels. However, what isremarkable is that when only taking gasoline A into con-sideration a significant negative correlation for all strainswas found, since for gasoline A oils 1 and 4 gave exceptionallylow emission of PAH and oils 2 and 3 gave higher values,

while the mutagenic effects showed the opposite. For bothtypes of gasoline, concerning the distribution between theparticulate phase and the semivolatile components, highestPAH amounts were observed where lowest mutagenicity wasseen and vice versa. However, the total sum of PAH may bea poor indicator to use since the dominant PAH in the exhaustgas are not considered to be carcinogenic. Therefore, aconcept proposed by Nielsen et al. (25) was applied, in whichthe PAH concentrations are multiplied by their carcinogenicpotencies relative to benzo[a]pyrene. This concept partiallygives an explanation to the distribution of mutagenic effectsbetween the filter extracts and the PUF extracts. However,even when using the sum of these weighted PAH concentra-tions the correlation to mutagenicity data was poor (r 2 ) 0.3both for TA98+S9 and TA100+S9). One explanation for thispoor correlation is that the major contribution to themutagenicity comes from other compounds than PAH, e. g.,more polar components, as has been seen earlier with four-stroke gasoline exhaust samples (26, 27).

AcknowledgmentsThe authors thank the staff at The Swedish Machinery TestingInstitute (SMP) for technical support, Bengt Lundquist forvaluable discussions on statistical matters, and Roger Wester-holm for doing some analysis at the last minute. The supportfrom Husqvarna AB and Preem Petroleum AB is also gratefullyacknowledged. This research was financially supported byCentre for Environmental Research in Umeå (CMF) and TheSwedish Council for Work Life Research (RALF).

Literature Cited(1) Hagberg, M.; Lindahl, R.; Nilsson, C.-A.; Norstrom, Å. Eur. J.

Respir. Dis. 1985, 66, 240-247.(2) Nilsson, C.-A.; Lindahl, R.; Norstrom, Å. Am. Ind. Hyg. Assoc. J.

1987, 48, 99-105.(3) Nilsson, C.-A. Chainsaw exhaust and fuels; Investigation report

1988:29; National Institute of Occupational Health: Umeå,Sweden, 1988 (in Swedish).

(4) SS 15 54 61. Motor fuels-special gasoline for powered implements;Swedish Standards Institution: Stockholm, Sweden, 1995.

(5) IARC. Monographs on the Evaluation of Carcinogenic Risks toHumans, Vol. 32; International Agency for Research on Cancer:Lyon, France, 1983.

(6) Westerholm, R. N.; Alsberg, T. E.; Frommelin, Å. B.; Strandell,M. E.; Rannug, U.; Winquist, L.; Grigoriadis, V.; Egeback, K.-E.Environ. Sci. Technol. 1988, 22, 925-930.

(7) Westerholm, R. N.; Almen, J.; Li, H.; Rannug, J. U.; Egeback,K.-E.; Gragg, K. Environ. Sci. Technol. 1991, 25, 332-338.

(8) IARC. Monographs on the Evaluation of Carcinogenic Risks toHumans, Vol. 46; International Agency for Research on Cancer:Lyon, France, 1989.

TABLE 7. Mutagenicity on Salmonella typhimurium Strains TA98 and TA100 of Filter Extracts and PUF Extracts in the Presence(+S9) and in the Absence (-S9) of a Metabolizing Systema


filter PUF filter PUF filter PUF filter PUF

Gasoline ATA98-S9 34*** (4.8) 140*** (8.0) 0.3 (0.4) -0.1 (0.6) 0.2 (0.4) -0.1 (0.8) 40*** (4.5) 120*** (13)TA98+S9 9.1*** (1.9) 14*** (2.3) 0.2 (0.4) 0.5 (0.6) 4.8** (1.5) 0.5 (0.6) 16*** (2.7) 26*** (2.9)TA100-S9 29*** (3.5) 60*** (10) -0.4 (0.7) -0.1 (0.9) 2.6* (1.1) 1.0 (0.6) 41*** (3.0) 120*** (17)TA100+S9 6.5*** (1.0) 15*** (1.8) 0.4 (0.6) 1.1 (0.8) 2.0 (1.0) 0.5 (0.7) 17*** (2.4) 27*** (3.1)

Gasoline BTA98-S9 120*** (7.6) 93*** (7.0) 88*** (18) 67*** (5.0) 19*** (3.5) 2.8 (1.6) 27*** (2.6) 5.7* (2.3)TA98+S9 51*** (2.8) 27*** (3.5) 42*** (8.2) 24*** (2.3) 17*** (1.8) 0.5 (0.7) 19*** (1.5) 2.3* (0.8)TA100-S9 110*** (6.5) 91*** (6.2) 67*** (15) 73*** (4.7) 8.9*** (1.9) 0.7 (0.7) 22*** (2.5) 2.9* (1.3)TA100+S9 48*** (4.6) 26*** (1.8) 29*** (6.5) 25*** (2.4) 9.0** (2.7) 0.9 (0.6) 32*** (3.6) 4.5*** (0.9)

a Numbers show revertants per liter of diluted exhaust and are regression coefficients from a combined regression analysis of data from threeseparately extracted samples. Standard deviation is given in parentheses. *, significant at the 95% level (Student’s t-test). **, significant at the99% level (Student’s t-test). ***, significant at the 99.9% level (Student’s t-test).


(9) Balk, L.; Ericson, G.; Lindesjoo, E.; Petterson, I.; Tjarnlund, U.;Åkerman, G. Effects of exhaust from two-stroke outboard engineson fish; TemaNord Report 1994:528; ISBN 92 9120 439 0; NordicCouncil of Ministers: Copenhagen, Denmark, 1994.

(10) McGinty, R. P.; Dent, N. P. Environ. Technol. 1995, 16, 603-623.(11) Cosmacini, E.; Cottica, D.; Pozzoli, L.; Leoni, R. J. Synth. Lub.

1987, 3, 251-261.(12) Laimbock, F. J. SAE Tech. Pap. 1991, No. 910675, SP-847.(13) Hare, C. T.; White, J. J. SAE Tech. Pap. 1991, No. 911222.(14) Hare, C. T.; Carroll, J. N. SAE Tech. Pap. 1993, No. 931540.(15) IARC. Monographs on the Evaluation of Carcinogenic Risks to

Humans, Vol. 33; International Agency for Research on Cancer:Lyon, France, 1984.

(16) Magnusson, R.; Nilsson, C.; Andersson, K.; Andersson, B.; Gieling,R.; Wiberg, K.; Ostman, C.; Rannug, U. Environ. Technol. 2000,21, 819-829.

(17) Method 1500. NIOSH Manual of Analytical Methods; NationalInstitute for Occupational Safety and Health: Cincinnati, OH,1984.

(18) Ostman, C.; Carlsson, H.; Bemgård, A.; Colmsjo, A. PolycyclicAromat. Compd. Suppl. 1993, 3, 485-492.

(19) Ostman, C.; Bemgård, A.; Colmsjo, A. J. High Resolut. Chro-matogr. 1992, 14, 437-443.

(20) Maron, D. M.; Ames, B. N. Mutat. Res. 1983, 113, 173-215.(21) Schuetzle, D.; Siegl, W. O.; Jensen, T. E.; Dearth, M. A.; Kaiser,

E. W.; Gorse, R.; Kreucher, W.; Kulik, E. Environ. Health Perspect.Suppl. 1994, 102 (4), 3-12.

(22) Wagner, T.; Wyszynski, M. L. Proc. Inst. Mech. Eng. 1996, 210,109-122.

(23) Ostermark, U.; Petersson, G. Chemosphere 1993, 27, 1719-1728.(24) Pedersen, P. S.; Ingwersen, J.; Nielsen, T.; Larsen, E. Environ.

Sci. Technol. 1980, 14, 71-79.(25) Nielsen, T.; Jørgensen, H. E.; Larsen, J. C.; Poulsen, M. Sci. Total

Environ. 1996, 189/190, 41-49.(26) Rannug, U.; Sundvall, A. Environ. Int. 1985, 11, 303-309.(27) Alsberg, T.; Stenberg, U.; Westerholm, R.; Strandell, M.; Rannug,

U.; Sundvall, A.; Romert, L.; Bernson, V.; Petterson, B.; Toftgård,R.; Franzen, B.; Jansson, M.; Gustafsson, J.-Å.; Egeback, K.-E.;Tejle, G. Environ. Sci. Technol. 1985, 19, 43-50.

Received for review October 20, 1999. Revised manuscriptreceived April 3, 2000. Accepted April 20, 2000.

ES9912022


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