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ES/RP 532 Applied Environmental Toxicology Page 1 of 18

ESRP532 Lecture 18.doc Fall 2004

November 3, 2004

Lecture 18 Oil Products (Hydrocarbons, Polycyclic Aromatic Hydrocarbons)

I. OverviewA. Contamination by oil and its byproducts probably competes with pesticides for public

concerns about chemical contamination. You may recall the television stories for days onend after the Exxon Valdez spilled its cargo in the Gulf of Alaska (~1990). In this lecturewe will examine what oil is. A key point to bear in mind is that oil is a completely naturalproduct. Surprisingly, oil products as a whole are not very acutely toxic, but byproducts ofoil refining (for ex., the volatile organic components of gasoline) and combustion (for ex.,polyaromatic hydrocarbons (PAHs) have become contaminants we are constantly exposedto at higher doses than the dietary intake of pesticides. Many of these materials are provenmutagens and therefore are of concern (recall that hardly any pesticides are mutagens, butEPA classifies many as carcinogens). Ironically, these same materials “contaminate” as aresult of natural processes in addition to anthropogenic activity.

II. Chemical Composition of Oil (most of the information taken from McGill et al. 1981, SoilBiochemistry, vol. 5)A. Petroleum is a natural complex mixture pumped from deposits buried in very old geological

strata; it is composed of natural gases and oils;1. Gases include methane, ethane, and higher hydrocarbons;

a. Petroleum can contain large quantities of gas when it is pumped to the surface--upto 300 volumes of gas per volume of oil

b. Natural gas used for domestic and industrial power is composed of1. 73-95% methane;2. 3-24% ethane;3. Smaller amounts of higher hydrocarbons (i.e., longer carbon chains)

c. Prior to distribution of natural gas, hydrogen sulfide is removed and odorizingsubstances like ethylmercaptan, dimethylsulfide, or other foul smelling volatileorganics are added (~30 ppb by volume)

2. Oils--all oils differ depending on their geological sourcea. The generic components in oil include paraffins, aromatics, napthenics, and

asphaltenesb. Fractionation of crude oil (i.e., the distillate fractions or cuts)

1. natural gases2. refinery gas3. liquid petroleum gas (methane:butane, characterized by a boiling point

[b.p.]<15.5 °C)4. gasoline (b. p. ~15.5 - 149 °C)5. diesel fuels6. kerosenes7. gas oil8. distillate residue

c. Refining crude oil produces the following fractions (ordered by increasingmolecular weight)1. gasoline2. diesel fuels3. kerosenes4. engine oils5. lubricating oils6. petroleum waxes



7. petrolatum8. asphalts (bitumens)

a. Residue left containing carbon disulfide-soluble and nonvolatile componentsd. Chromatography resolves crude oils into the following fractions

1. AsphalteneI. An ill-defined mixture of high molecular weight, pentane-insoluble, colloidal compounds

including polycyclic aromatic (PAHs) and alicyclic molecules with some alkyl substituents,usually methyl groups

1. N, S, and O atoms can be present;2. MW (molecular weight) from 500 to a few thousand;3. Generic structure is polymeric

S

OH

Basic Structural Unit of Asphaltene

2. Saturate fractionII. Hydrocarbons (saturated and aromatic) usually make up at least 75% by weight of crude

oils1. Saturates are predominantly n-alkanes, branched alkanes, and mono-, bi-,

and polycyclic alkanes (naphthenes)(a) n-alkanes can make up to 25% of the total weight of the crude oil(b) Cyclics can comprise 30-60% of the total weight

CH3 (CH2)8 CH3

n-decane

CH3 (CH2)6 CH CH3

CH3

2-methylnonane phytane (2,3,10,14-tetramethylhexadecane)

cyclohexane 1,2-dimethylcyclopentane 1-methyl-2-ethylcyclopentane

3. Aromatic fraction (PAHs)III. Mono-, bi-, and polycyclic aromatics;

b. Includes mixed naphthenic and aromatic ring systems with up to 10 rings;c. Each ring system may have alkyl substituents, denoted below by a bond (i.e.,

the straight line) emanating from any ring.



benzene ortho-xylene 1,2,7-trimethylnaphthalene

2-methylindane benzenecyclohexane

phenanthrene pyrenenaphthalene

anthracene benzo[a]pyrene benzo[a]anthracene

chrysene triphenylene

4. N-S-O fraction (compounds containing nitrogen, oxygen, and/or sulfur)a. Contains polar compounds like naphthenic acids, mercaptans, thiophenes,

pyridines (these are also present in the asphaltene fraction);



b. Nitrogen contents of crude oils are generally below 0.2% and rarely exceed1% by weight;

c. Sulfur content of crude oil typically varies between 0.3% and 3%.

NCH3

CH3

3,8-dimethylquinoline

N

3-methyl-5-ethylpyridine

SHCH3

CH3CH3

2,3,5-trimethylthiocyclopentane 4,6-dimethyldibenzothiophene

SCH3 CH3

CH3

OH

ortho-cresol

COOH

palmitic acid (a fatty acid)5. Co-constituents: there are metallic constituents in oil in concentrations within

the 0.1 to 100 ppm rangea. Brine (for ex., NaCl) is present at concentrations up to 45,000 ppm

B. Biochemical (i.e., cellular) lipids (hydrocarbons, waxes, fats) have many constituents incommon with lipids in oils, but in crude oils the constituent hydrocarbons are not referred toas lipids1. Thus, hydrocarbons occurring naturally in soil are presumed to be lipids of microbial

originB. In addition to natural hydrocarbons occurring in soil, polycyclic aromatic hydrocarbons

(PAHs) are natural compounds formed during incomplete oxidation (i.e., combustion).1. For example, cigarette smoke, forest fires, etc.2. Research by Blumer and Youngblood (1975, Science 188:53) showed that natural fires

produced various PAHs that were atmospherically transported and deposited over longdistances

3. The difference between PAHs originating by fire and those in crude oil can be observedby examining the alkyl substitution patterns and abundance of each homolog as shownin the following graph, where the y-axis represents the relative abundance of the varioushomologs, represented on the x-axis as an increasing number of alkyl groups



substituted on a basic PAH ring system (three basic ring systems studied includedbenzanthracene, chrysene, and triphenylene).

III. Sources & Emission RatesA. Natural abundance

1. A review by Edwards (1983, J. Environmental Quality 12:427) suggested that theconcentration of endogenous PAHs in soil would be about 1-10 ppm;a. For endogenous benzo(a)pyrene (BaP) alone, which is one of the most studied

PAHs (another one is naphthalene), concentrations were < 10 ppb;b. However, in rural areas, concentrations around 1 ppm have been found, and the

distances from major highways and cities suggested that the sources were not airpollution

c. In polluted soils (i.e., urban soil, soils near factories), the concentrations could be ashigh as 650 ppm

C. Although PAHs and other hydrocarbons are natural “contaminants”, their environmentallevels are considered low by comparison to the inputs from anthropogenic sources (Tablefrom Edwards 1983)

Sources U.S.--BaPkg x 104 (% of Total)

Global--BaPkg x 104 (% of Total)

Polycyclic Organic Matterkg x 104 (% of Total)

Heating & power 0.43 (36.8) 2.36 (51.6) 208.65 (4.8)Industrial processes 0.18 (15.4) 0.95 (20.8)Enclosed incineration 0.03 (2.6) 0.09 (2.0) 390.09 (9.0)Coal refuse burning 0.31 (26.5) 0.62 (13.6)Forest/Agric. fires 0.13 (11.1) 0.38 (8.3) 3,256.78 (75.1)Other refuse burning 0.07 (6.0) 0.13 (2.8) 480.81 (11.1)Trucks & buses 0.01 (0.8) 0.03 (0.7)Automobiles 0.01 (0.8) 0.01 (0.2) TOTAL 1.17 4.57 4,336.33



1. Note: For heating & power, 91% of production is from coal & 8% from wood2. For industrial processes, 99% is from coke production3. Global POM emissions for fires are attributed as 60% agric. burning and 40% forest

fires.D. Further support for the importance of anthropogenic sources of PAHs as large contributors

to current PAH contamination comes from studies of atmospheric loading of PAHs to LakeMichigan as recorded in the sediments (Simck, M. F. et al., 1996, Environ. Sci. & Technol.30(10):3039-3046).1. Using sediment core sampling from the floor of Lake Michigan coupled with an

analysis of PAH concentrations and loading rates, one can piece together the yearlyaccumulation of these combustion products;a. The deeper the core, the older the sediment; thus, one can see how contamination

changed over time by measuring the concentrations in various core depths;2. Simck et al. (1996) observed that the accumulation of PAHs in the sediments increased

dramatically around 1900 and reached a plateau around 1930-1975, with a slightdecrease in recent years;

3. Simck et al. corrected their data for movement of finer sediments from shallow areas todeeper, quiescent areas in the profile through episodic resuspension and settling (thisphenomenon is known as sediment focusing);a. They observed that surface sediments (i.e., at the top of the profile) were

accumulating at the rate of 50-70 ng total PAHs per cm2 per year;b. The inventory (i.e., the load all PAHs) was 5000-7000 ng cm2.

4. Because the pattern of individual PAH concentrations corresponded to PAHs inChicago air particulates and coke ovens (i.e., gigantic furnaces burning coal to producecoke and steel), they concluded that these sources were the major contributors toloadings in Lake Michigan rather than vehicular traffic, which burns gasoline;a. Note that coke is the residue left after coal is burned; it also has uses as fuel.

E. Because petroleum oils are largely used as fuel sources, it is informative to look atcontaminant emission rate as a function of units of energy delivered (from Smith, 1987,Biofuels, Air Pollution, and Health);1. Burning of “natural” fuels worldwide contributes greater loads of hydrocarbons than

industrial sources (see residential and cooking stoves in the table);

Comparison of Air Pollutant Emissions per Unit Delivered Energy (listed as kg of pollutant pertrillion joules delivered) (Smith 1987)Fuel (efficiency) Fuel Equivalent

to 106 megajoulesdelivered

Particulates[emissionfactors, in g/kg]

Sulfuroxides

Nitrogenoxides

Hydro-carbons(kg per106 joules)

Carbonmonoxide

IndustrialWood (70%) 89 MT 500 53 400 400 450Bituminous (80%) 43 MT 2,800 820 320 22 45Residual Oil 33,000 L 94 1,310 240 4 20Distillate Oil 31,400 L 8 1,120 83 4 19Natural Gas 28,200 cu. m 7 negligible 99 2 8

Residential <5 kW)Heating StovesWood (50%) 130 MT 2,700 30 100] 6,800 17,000Anthracite (65%) 49 MT 46 200 [4] 250 100 1,000Bituminous (65%) 53 MT 550 1,100] 270 530 5,300Distillate oil (85%) 32,900 L 11 1,170 71 4 20



Natural gas (85%) 30,000 cu. m 7 negligible 38 4 10Cooking StovesTropical wood (15%) 420 MT 3,800 250 300 [0.7] 3,200 [7.5] 34,000Cow dung (15%) 530 MT 10,000 3,200 ? ? 44,000Indian coal (20%) 220 MT 280 2,200 460 [2] 2,200 [10] 27,000Coconut Husk (15%) 480 MT 17,000 ? / ? 54,000Natural gas (80%) 32,000 cu. m 0.5 negligible 10 5 250

F. Historical Trends in PAH deposition1. Sanders et al. 1995 (Environ. Pollution 89:17-25) examined the concentrations of PAHs

and estimated the PAH fluxes in individual sections of peat cores obtained from a bogin rural north-west England. (see next graph)a. The bogs were sectioned into approximately 2 cm slices, and radiocarbon dating

used to estimate the year of each section.b. Initial increases in PAH loadings appeared to coincide with the beginning of the

Industrial Revolution, with fluxes peaking in the early 1930s. Introduction ofemission controls and the decline of heavy industry seems to have led to an 80%reduction in the net flux of PAHs to the bog over the last 40 years.

1. Yamashita et al. (2000, ES&T 34:3560-3567), examining limnological cores from theTokyo Bay, have shown similar historical trends in total PAH increase over time.



a. Yamashita et al. 2000 identified specific PAH congeners in the different sedimentlayers.

Key: FE=fluorene; PH=phenanthrene; FA=fluoranthene; PY=pyrene; BA=benz[a]anthracene;CY=chrysene; BbF=benzo[b]fluoranthene; BkF=benzo[k]fluoranthene; BaP=benzo[a]pyrene;IP=indeno[1,2,3-cd]pyrene, BghiP=benzo[ghi]-perylene.



III. Physicochemical Properties--Hydrocarbons & PAHsB. Example PAHs

1. naphthalenea. WS = 37 ppmb. log Kow = 3.3c. V. P. = 0.082 mm Hg @ 25 °Cd. KH = 4.83 x 10-4 atm m3/mol

2. anthracenea. WS = 34 ppbb. log Kow = 5.91

3. benzo[a]pyrenea. WS = 7.1 ppbb. log Kow = 5.91

B. Water Solubility of Selected Petroleum Hydrocarbon Fractions (from McGill et al. 1981)1. Note that in general the larger the compound (e.g., the longer chain alkanes) the lower

the water solubility.Compound Solubility (ppm) Compound Solubility (ppm)Paraffins (straight/branched)methane 24ethane 60propane 62 Cycloparaffins & Cycloolefinsn-butane 61 cyclopentane 156iso-butane 49 cyclohexane 55n-pentane 39 cyclooctane 8iso-pentane 48 cyclopentene 5352,2-dimethylpentane 33 cyclohexene 213n-hexane 10n-heptane 3 Aromaticsn-octane 0.7 benzene 1780n-decane 0.02 toluene 515n-dodecane 0.0009 ethylbenzene 208n-hexadecane 0.0005 m-xylene 196

o-xylene 175Olefins naphthalene 34.4ethene 131 biphenyl 7.58propene 200 iso-propylbenzene 501-butene 2221-hexene 501-octene 3

IV. Environmental ChemistryA. Volatilization

1. Naphthalene volatilizes very readily (as do short chain hydrocarbons);a. For ex., Park (Environmental Chemistry & Toxicology) reported that 30% of the

added naphthalene volatilized from a Kidman sandy loam soil after 48 hours.b. As the number of PAH rings increases, the tendency for volatilization goes down

but sorption (to soil or sediment) goes up significantly (i.e., water solubility goesdown)

2. Baker and Eisenreich (1990, Environ. Sci. Technol. 24:342) have measured theconcentrations of 13 PAHs in the atmosphere and surface waters of Lake Superior



a. The average concentration of the sum of 13 PAHs was 2.8 ± 1.7 ng/m3 (range 2.5 -6.3 ng/m3)1. Concentrations over Lake Michigan were reported as 6.8 ng/m3 and Isle Royale

as 2.7 ng/m3.b. Lake Superior and Isle Royal would be considered comparatively clean areas, so

Baker and Eisenreich concluded that the levels they found represent backgroundcontinental air.1. Their collection methods allowed a determination of PAHs in the gaseous phase

and those in the aerosol (particulate phase)a. They found that the higher the molecular weight of the specific PAH, the

more likely it was to be distributed disproportionately in the aerosol phase;(see Table below)

b. Thus, the lower weight PAHs were distributed largely in the gas phase; Thedistribution was correlated with the liquid vapor pressure; the lowest vaporpressure PAHs were disproportionately distributed in the aerosol phase

c. According to Baker & Eisenreich (1990) “High molecular weight PAHs exist inthe atmosphere almost exclusively associated with aerosols and enter surface watersthrough dry deposition and aerosol scavenging by precipitation. Once deposited,particle-bound PAHs may not rapidly equilibrate with the dissolved phase and aretherefore not likely to volatilize. Hindered release of high molecular weight PAHsfrom particles may result from slow desorption kinetics and diffusion from withinthe interior of the particles. Conversely, PAHs such as phenanthrene occurprimarily in the atmospheric gas and aqueous dissolved phases and are available foractive exchange across the air-water interface.”

Concentrations of selected PAHs in the atmosphere (aerosol/gaseous) and surface waters (dissolved) ofLake SuperiorPAH(KH, Pa.m3/mol)

Number ofAromatic Rings

Aerosol(pg/m3)

Gas Phase(pg/m3)

Dissolved(ng/mL)

phenanthrene (0.691) 3 12.2 2650.5 3.49pyrene (0.125) 4 12.4 332.4 0.28benz[a]anthracene (0.092) 4 13.8 110.9 0.16benz[a]pyrene (0.009) 5 3.8 1.2 0.39

C. Mass Transport--Leaching1. While higher molecular weight (MW) PAHs are sorbed to a greater extent than the

lower MW compounds, transport through soil can be facilitated by association withnatural dissolved organic matter (DOM); (Johnson & Amy, 1995, Environ. Sci. &Technol. 29:807)a. DOM may also enhance desorption of PAHs from low organic carbon aquifer

sediments1. log Koc, anthracene = 5.242. log Koc, BaP = 5.95-6.20

b. In the Johnson & Amy (1995) experiment, soil columns were leached with watercontaining anthracene alone, or with anthracene plus humic acid (which served as thesurrogate for DOM); note in the graph that illustrates the break-through curves,sodium nitrate is a conservative (non-reactive) tracer;



D. Bioconcentration factors for PAHs by vegetation has been found to be less than 1.01. There is very little uptake by roots, perhaps as a result of comparatively high soil

sorption coefficients;2. Atmospheric deposition, however, can be responsible for significant levels of PAHs in

vegetation.

Recoveries (as % of 1 4C PAH) Applied to Sludge Treated Soil Cropped in a Greenhouse Microcosm

% Volatile% Recovered from AboveGround Vegetation

% Recoveredfrom Soil

Total %Recovered

PAH Ratemg/kg

CO2 Organic Rye Soybean Extract- able

Bound

Anthracene. 10 16 0.20 0.01 0.17 27 46 89BaP 10 2.2 0.00 0.00 0.01 61 22 85

E. Degradation of PAHs1. Degradation rate decreases as the number of rings increases;2. For ex., BaP with 5 rings is very resistant to degradation (and formation of bound

residues).a. Abiotic degradation of PAHs is significant only for ≤3-ring PAHs; it is

insignificant for >3-ring PAHs.3. Biotic degradation and mineralization to CO2 can be significant with the lower molecular

weight PAHs.4. Half-life tends to increase with higher molecular weight PAHs.

Partial Dissipation Pathway Characterization for Several PAHs on a Kidman sandy loam soil(Data adapted from K.S.Park. 1990. Fate of PAH Compounds in Two Soil Types: Influence of Volatilization,Abiotic Loss and Biological Activity. Environ. Toxicology and Chemistry, 9:187-195)PAH Initial Conc.

(mg/kg)First OrderHalf-life (T1/2) (days)

% abioticdissipation

MaximumCO2 evolved@ 60 days

naphthalene 101 2.1 12.0 -anthracene 210 134 8.7 60phenanthrene 902 16 17.4 55pyrene 686 260 4.4 55benz[a]anthracene 107 261 2.5 35benzo[a]pyrene 33 309 7.3 3



V. Environmental ToxicologyA. Because oils spill on land as well as water, and sludges containing PAHs are applied to

agricultural lands, there has been an interest in toxicity to plants1. In general, oils themselves have not been very toxic to plants grown in soils

purposefully treated with oils.2. However, in some crops there has been chlorotic symptoms, apparently due to a

nitrogen deficiency.a. It has been hypothesized that the high levels of oils after a spill induce microbial

activity that depletes the soil of its biologically available nitrogen (i.e., nitrate)B. Metabolic Pathways

1. Main biochemical degradation mechanism is oxidation by monooxygenase ordioxygenase enzymes (i.e., cytochrome microsomal oxidase system)a. A difference between mammalian and bacterial metabolism of PAHs

1. Bacteria will produce a dihydrodiol early in the metabolic pathway.2. Mammals will produce an arene oxide intermediate that is then metabolized further to a

compound that is capable of forming an adduct with DNA (i.e., it becomes verymutagenic)

Benzo[a]pyrene (BaP)

MammalianCyt. P450MonooxygenaseNADPHO2

OBaP-epoxide

BaP dihydrodiol

HO H

HHO

HO H

HHO

O

BaP-diol epoxide

DNA

Alkylated DNA

Mammal

Mammal

Bacterial

3. Bacterial oxidation of the smaller PAHs (e.g., naphthalene) proceeds through thedihydrodiol metabolite; this metabolite is further oxidized until the last ring is cleaved;carbon dioxide is released during this process.



OH

OHH

HOH

OH

OHC

OH

COOH OH

OHRing Cleavage + CO2

Naphthalene dihydroxy, dihydronaphthalene dihydroxynaphthalene

hydroxybenzalpyruvic acid

salicylic acid

catechol

COOHO

C. Acute Toxicity of Some Petroleum Hydrocarbon Products1. Rat oral studies; administration of dose via gavage Beck et al. (1984, in Applied

Toxicology of Petroleum Hydrocarbons, vol. VI)

Product Tested Highest Dose, g/kg % Mortality Estimated LD5 0, g/kgUnleaded gasoline 18 90 13.6Jet Fuel A 20 0 >20Diesel Fuel 16.6 90 7.5#2 Home Heating Oil 21 70 - 90 12.0 - 17.5Paraffinic Oil 5 0 >5Naphthenic Oil 5 0 >5Motor Oil 22 0 >22#6 Heavy Fuel Oil 22 0 >22

D. Primary Dermal Irritation Studies (Beck et al. 1984)1. Rabbits backs were shaved2. 0.5 mL of test substance placed on gauze patches possessing an occlusive plastic wrap

and then placed on one of four locations on rabbit’s back;a. Two sites were shallowly abraded prior to placing the test material

3. After 24 hours, remove gauze, wipe skin, and observe for signs of erythema (reddening)and edema (swelling) for up to 72 hours

4. Results:a. Home Heating Oil scored as moderately irritating and Diesel Fuel scored as

extremely irritating;b. All other products were scored as slightly to minimally irritating

E. Mutagenicity & Tumorigenicity1. BaP is mutagenic in the Ames Salmonella assay

a. Eight PAHs are considered as possible or probable carcinogens (these are alsogenotoxins)



1. benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene,benzo[a]pyrene, indeno[1,2,3,c-d]pyrene, dibenzo[a,h]anthracene, andbenzo[g,h,i]perylene

2. Note that these tend to be high molecular weight PAHs2. Tumorigenicity has been measured by placing BaP directly on the skin of male and

female micea. Observations indicate a positive response that is graded with respect to dose (see

Table below)

Skin Tumorigenicity of Benzo(a)pyrene in Male and Female Mice (Holland & Frome (1984, in AppliedToxicology of Petroleum Hydrocarbons, vol. VI)BaP Dose(mg/week)

Number Exposed Number withTumor

Average Weeksto Tumor

Time to First &Last Tumor

0.015 95 92 44.7 30 - 580.0075 100 95 66.9 45 - 850.00375 95 42 90.7 53 - 1060.001875 100 4 97.4 87 - 1070 (acetone) 300 0 - -

F. Endocrine Disruption1. PAHs seem to have no estrogenic activity when tested in vitro in a transgenic yeast

estrogen receptor reporter assay (YES test) (Tran et al. 1996; “The anti-estrogenicactivity of selected polynuclear aromatic hydrocarbons in yeast expressing humanestrogen receptor. Biochemical & Biophysical Research Communications 229:102-108)

2. However, 4 PAHs (dibenzo anthracene, 6-hydroxy-chrysene, 2,3-benzofluorene, andbenzo(a)pyrene inhibited the activity of estradiol in the YES from yeast strain ER(wt).In the YES strain ER179C, the inhibitory activity was substantially reduced.

G. Immunotoxicity1. The PAHs most studied for potential immunotoxicological effects include BaP and 3-

methylcholanthrene, and dimethylbenz[a]anthracene (DMBA); the two formercompounds are natural combustion products and the latter is a synthetic derivativestudied as a prototypical PAH; all three compounds have been found to be highlyimmunotoxic; interestingly, BeP (and the 3 ringed anthracene as well) are notimmunotoxic.

CH3

CH3

DMBA (dimethylbenz[a]anthracene)

CH3

3 MC (3-methylcholanthrene)

BaP (benzo[a]pyrene) BeP (benzo[e]pyrene



2. Generally, PAHs are cytotoxic at high doses, producing lymphoid organ atrophy, whileat lower doses immunotoxicity occurs without cytotoxicity;

3. An in vivo total dose exposures in the range of 50-100 mg/kg for BaP and DMBA arenecessary to achieve significant immuno-suppression or cytotoxicity following oral orsubcutaneous exposures of rodents. A 5-10 µM concentration is typically required toimpair in vitro immune responses of rodent lymphoid cells. (from Davila, D. R. et al.,1997, Toxicity of polycyclic aromatic hydrocarbons to the human immune system:models and mechanisms, Toxicol. & Ecotoxicol. News/Reviews 4(1):9)a. Compare the in-vivo dose to the actual human exposures in table below (smoker vs.

non-smoker).H. Human Response (Epidemiology)

An epidemiological study conducted with asphalt workers and workers from otherindustries using oil products (paving companies, roofing manufacturers, interstate truckoperators) were negative with respect to adverse health problems; the average exposureperiod was 15.1 yrs (Baylor et al., 1968, Arch. Environ. Health 17:210)

VI. Exposures of Humans to PAHsA. Menzie et al., 1992, Environ. Sci. & Technology 26:1278

Comparison (Smoker vs. Nonsmoker) of Potential Doses of Carcinogenic PAHsMedian values Maximum values

Source of PAHs Intake (µg/day) Percent of Total Intake (µg/day) Percent of TotalNonsmokersFood 3 96.2 12 79Air 0.05 1.6 2.70 18Water 0.006 0.2 1.09 0.124 1Soil 0.06 100.00 0.4 2Total 3.12 15.22 100

SmokersMainstream smoke 2 - 5 (1 pack/day) 6 - 15 3 (packs/day)All other sources 3 15Total 5 - 8 21 - 30

B. Exposure of Children1. Vyskocil et al. 2000 (Environ. Toxicol. & Pharmacol. 8:111-118) studied exposure of

children in kindergarten from a “polluted” area (high traffic density) and non-pollutedarea (“green zone”) in Canada.a. Measured 12 PAHs in soil, air, and dietb. Also measured 1-hydroxypyrene in urine as a biomarker of exposure

1. Chose the metabolite of pyrene because pyrene is one of the most abundantPAHs.

c. Total PAH levels & Pyrene levels in air (Vyskocil et al. 2000):Total PAHs (ng/m3) (Range) Pyrene (ng/m3) (Range)LocationOutdoor Indoor Outdoor Indoor

Kindergarten(polluted area)

14.8-36.1 2.6-3.6 1.6-5.1 0.3-0.5

Kindergarten(non-pollutedarea)

1.6-2.2 1.0-2.8 0.3-0.4 0.2-0.5

Montreal-highwayDecarie (1989-91)

62.7



Decarie (1989-91)London (1991) 166

b. PAH levels in soil: (for absorbed dose, assumed children ingest 80 mg soil/dayLocation Total PAHs (ng/g) Pyrene (ng/g) Absorbed Dose (ng/d)

Kindergarten (polluted area) 132 10.4 0.104Kindergarten (unpolluted area) 65 6.1 0.061

c. PAH intake (Absorbed mean daily dose)1. Only the air inhalation (ng/day) value for the pooled day 1-3 samples of children

in the kindergarten polluted area was statistically significantly different from thekindergarten children in the non-polluted area (p<0.001)

Location Day ofSampling

Food Consumption Air Inhalation TotalDose

n ng/day Geometricmean (range)

% ng/day % (ng/day)

Kindergarten(polluted area)

1 11 170 (132-412) 93 12.5 (8.1-17.9) 7 183

2 11 204 (151-767) 96 7.7 (6.0-8.7) 4 2123 11 126 (82-239) 95 6.1 (5.1-6.9) 5 1321-3 33 167 (82-767) 95 8.4 (5.1-17.9) 5 175

Kindergarten(non-polluted)

1 13 188 (115-518) 97 5.1 (5.0-5.2) 3 193

2 12 170 (74-471) 97 5.0 (4.8-5.2) 3 1753 12 200 (138-435) 97 6.1 (5.9-6.2) 3 2061-3 37 186 (74-518) 97 5.4 (4.8-6.2) 3 191

Parameters assumed for calculations of absorbed dose:Ingestion bioavailability of pyrene: 12.5%Inhalation bioavailability of pyrene: 84.2%Pulmonary ventilations per minute: Sleeping, 10.1; Indoor activity, 12.3; Outdoor activity, 13.6Time outdoors was recorded

d. Urinary Excretion of 1-hydroxy pyrene (1-OHP) biomarker; N=number ofsamples)

Location Day ofSampling

1-OHP Morning) 1-OHP (evening)

N µmol/mol creatinine N µmol/mol creatinineKindergarten(polluted)

1 11 0.21 (0.07-0.099) 10 0.22 (0.1-0.77)

2 11 0.17 (0.05-0.77) 9 0.16 (0.03-0.54)3 10 0.21 (0.002-0.070) 10 0.19 (0.03-0.70)1-3 32 0.20 (0.002-0.77) 29 0.19 (0.03-0.77)

Kindergarten(non-polluted)

1 10 0.11 (0.03-0.22) 10 0.12 (0.03-0.77)

2 12 0.17 (0.06-0.41) 10 0.14 (0.04-0.25)3 13 0.10 (9.91-0.24) 11 0.14 (0.09-0.26)1-3 35 0.12 (0.01-0.41) 31 0.13 (0.03-0.26)



e. The absorbed dose estimated for soil only constituted 0.032% and 0.059% of thetotal absorbed dose in “unpolluted” and “polluted” areas, respectively.1. Similarly, inhalation exposure was <10% of food consumption exposure in each

location.2. Thus, Vyskocil et al. (2000) concluded that dietary intake of PAHs was the most

important route of exposure, and intakes did not differ significantly betweenkindergarten children in the “polluted” and “non-polluted” areas.

VI. Ecotoxicological AspectsA. Acute Toxicity/NOECs—selected organisms and PAHs (Data from van Brummelen et al.,

The Handbook of Environmental Chemistry, vol. 3, Part J, PAHs and Related Compounds,pp. 203-263). Freshwater Organisms

PAH Taxonomic Group Tox. Parameter Concentration (µg/L)Naphthalene Chlorophyta EC50—growth 33,000

Mollusca LC50 5,000Insecta LC50 1,000-13,000Crustacea LC50 2200-8800Pisces (Pimephalis) NOEC—hatchability

NOEC—mortalityNOEC growth

4501800450

Amphibia LC50 2100

Benzo(a)pyrene Chlorophyta EC50—growth

NOEC—growth

5.7(geometric mean fromdifferent tests)

10Crustacea LC50 5Pisces (Brachydanio) NOEC 6.3

B. Studies by the National Marine Fisheries Service have shown that tumors in several speciesof fish can be correlated with the occurrence of PAHs in sediments;1. Extraction of sediments and application to fish (i.e., subsequent exposure of fish to the

extracts) has induced liver tumors2. Thus there are long term consequences of incomplete combustion products on aquatic

organisms;a. Something to ponder: Have the potential chronic adverse effects (as opposed to the

acute adverse effects) of persistent organochlorine hydrocarbon pesticides beenover-rated while other contaminants have been underrated?

C. Of course, oil spills can be quite hazardous to birds because of the physical action of simplycoating the feathers;1. While oils are generally biodegradable, whether in the soil or in the ocean, over time, the

question to be asked is are the individual constituents toxic;2. This issue has been addressed for weathered crude oil;

a. Weathered crude oil from the Exxon Valdez oil spill has been tested for possibleadverse effects, but high doses were required to cause any adverse effects;

b. On the other hand, earlier studies have shown that small amounts of petroleumhydrocarbons applied to mallard eggs cause embryotoxic and teratogenic effects(e.g., Hoffman, D. J., 1979, Embryotoxic and teratogenic effects of petroleumhydrocarbons in mallards, J. Toxicol. & Environ. Health 5:835-844).1. In this particular study, a mixture of the hydrocarbons that were represented in a

typical crude oil were applied directly to the eggs; this material would notnecessarily represent a weathered oil.



2. Mallard eggs were exposed to 10 µL of a mixture of aliphatic hydrocarbons ormixtures of the aliphatic hydrocarbons with aromatic hydrocarbons (whichincluded some PAHs) dissolved in them. Mallard eggs were essentiallyunaffected by the aliphatic hydrocarbons alone. However, mortality wassubstantially increased by the aromatic hydrocarbons mixture.

c. On the other hand, intermediates formed during degradation could be toxic toinvertebrates; for example,1. A weathered Prudho Bay crude oil taken from the Alaskan North Slope was

studied under optimized biodegradation conditions (i.e., known active microbialcultures were added to the weathered oil; biodegradation was allowed to proceed,and the mixture of metabolites were isolated and then bioassayed) (Chapman, P.J. et al., 1995, Fossil fuel biodegradation: laboratory studies, Environ. HealthPerspectives, 103 (Suppl. 5):79-83.

2. Toxicity tests with the “neutral fraction” of biodegraded weathered crude oilwas shown to be toxic to shrimp;a. A three-fold dilution of the mixture, however, eliminated the toxicity.

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