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1 ESRP 532 Applied Environmental Toxicology Lecture 19 Volatile Organic Compounds (VOCs) [email protected] http://feql.wsu.edu/teaching Sources Fuels BETX (benzene, ethylbenzene, toluene, xylene) Precursors for synthesis of polymers Some volatile organohalogens Solvents/Degreasers TCE, Perc Water treatment processes Trihalomethanes Oxygenate additives for fuels (MTBE) Natural sources Methyl bromide Pathways of Contamination Major pathways of contamination Motor vehicle emissions Off gassing from contaminated water Wastewater effluents Runoff from streets Biosynthesis and emission from oceans Benzene ethylbenzene toluene BETX o-xylene m-xylene p-xylene Cl Cl Cl trichloroethylene Cl Cl Cl Cl tetrachloroethylene Solvents/Degreasers C Cl Cl Cl Cl carbon tetrachloride O acrolein Cl vinyl chloride styrene Monomers H 2 C O formaldehyde
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Page 1: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

1

ESRP 532Applied Environmental Toxicology

Lecture 19Volatile Organic Compounds

(VOCs)

[email protected]://feql.wsu.edu/teaching

Sources

Fuels BETX (benzene, ethylbenzene, toluene, xylene)

Precursors for synthesis of polymers Some volatile organohalogens

Solvents/Degreasers TCE, Perc

Water treatment processes Trihalomethanes

Oxygenate additives for fuels (MTBE) Natural sources

Methyl bromide

Pathways of Contamination

Major pathways of contamination Motor vehicle emissions Off gassing from contaminated water Wastewater effluents Runoff from streets Biosynthesis and emission from oceans

Benzene ethylbenzene toluene

BETX

o-xylene m-xylene p-xylene

Cl

Cl

Cl

trichloroethylene Cl

Cl

Cl

Cl

tetrachloroethylene

Solvents/Degreasers

C

Cl

Cl Cl

Cl

carbon tetrachloride

O

acrolein

Cl

vinyl chloride

styrene

Monomers

H2C O

formaldehyde

Page 2: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

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H3C Br

methyl bromide

H3C Cl

methylchloride

Biogenic VOCs

(Also used as a soil fumigant on strawberries)

Compound WS(mg/L)

log Kow log Koc V.P.(mm Hg)

KH

(atm.m3/mol)benzene 1800 1.6 - 2.1 1.7 -2.0 76 - 118 5.5x10-3

ethylbenzene 161 3.15 2.2 9.53 8.4x10-3

toluene 490-515 2.7 - 2.8 2.1 22-40 6.7x10-3

xylene 152-200 3.0 - 3.2 2.1 -3.2 10 5-7 x 10-3

hexachlorobenzene 0.0062 5.31 4-5 1.9x10-5 1.3x10-3

styrene 310 2.95 2.4-2.7 6.6 2.8x10-3

cresols 23-30 1.95 1.3-1.7 0.13-0.31 8.7-16 x10-7

dibutyl phthalate 11.2 4.72 2.2-3.8 1.4x10-5 4.6x10-7

Physicochemical Properties

Compound WS(mg/L)

log Kow log Koc V.P.(mm Hg)

KH

(atm.m3/mol)methyl bromide 17,500 1.2 2.1 1633 6.2x10-3

methyl chloride 6,480 0.9 4310 2.4x10-2

chloroform 8,000-9,300 1.9 - 2.0 1.6 160-245 3- 7.2 x10-3

carbontetrachloride

800-1,160 2.8 2.4-2.6 113 2.4- 3x10-2

formaldehyde 550,000 0.4 3883 3.3x10-7

trichloroethylene 1,100-1,470 2.3 - 3.3 1.8-2.1 58 -94 9-11x10-3

tetrachloroethylene 150 2.6 -2.9 2.3 -2.6 20 1.5x10-2

vinyl chloride 2763 1.4 <1 2660 1.1x10-2

acrolein 208,000 -0.1 1.4 265 4.4x10-6

Physicochemical PropertiesFate of VOCs in Water

Distribution & fate of VOCs in NarragansettBay, RI (Wakeham et al. 1983)

General Observations1. VOCs measured in water columns along a

N-S transect in the Bay;2. Several hundred different VOCs detected;3. Volatilization a major removal process

(column residence times of 150-300 h);4. Sorption and sedimentation minor.

(Wakeham et al. 1983)

Note: relatively higher concentrations of TCE at Fields Point;outfalls for sewage treatment facilities; P is upstream

(Wakeham et al. 1983)

Page 3: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

3

Note: concentration gradient tended to be weak;Suggests multiple sources

(Wakeham et al. 1983)

Mesocosm Experiment

Compound WinterT1/2

SummerT1/2

T1/2,summer,(Sterile)

T1/2,summer,(Natural)

benzene 13 3.1 6.9toluene 13 1.5 7.9naphthalene 12 nd 11.3 0.8tetrachloroethylene 12 14 12.1 12.0dodecane 3.6 0.7 1.8 0.94

Wakeham et al. 1983

Half-life of Selected VOCsEvidence for Biodegradation

Atmospheric LifetimesAmbient Concentration Measurements

Compound# of

LocationsSampled

# of SamplesMedian or

range(µg/m3)

Lifetime in Air(days)

benzene >140 >10,000 5.1 >5ethylbenzene 93 8723 1.1 <1toluene 131 9373 8.6 1-5o-xylene 104 8542 2.2 <1m-xylene 98 8431 4.2 <1p-xylene 102 3597 4.3 <1 to 1-5hexachlorobenzene 21 6117 0.6 <1o-cresol 3 10 1.5 <1m-cresol 2 3 nd <1p-cresol 11 62 0.20 <1dibutylphthalate 3 >13 0.5-6.0

ng/m3<1

Kelly et al. 1994 (ES&T 28:378)

Atmospheric LifetimesAmbient Concentration Measurements

Compound# of

LocationsSampled

# of SamplesMedian(µg/m3)

Lifetime inAir

(days)methyl bromide 48 1081 nd >5methyl chloride 37 1434 1.3 >5chloroform 117 4368 0.2 >5carbon tetrachloride 131 5739 0.8 >5formaldehyde 58 1358 3.3 1-5trichloroethylene 124 4267 0.4 >5tetrachloroethylene 133 4893 1.7 >5vinyl chloride 66 1864 nd <1 to 1-5acrolein 2 12 nd <1

Kelly et al. 1994 (ES&T 28:378)

Volatilization Flux from Soil

Benzene Flux(mg/cm 2/min)

Temperature

Elapsed Time in Experiment

1/time

6

2

20

26

oC

Based on Shonnard & Bell 1993

Effect of Humidity onVolatilization Flux

Based on Shonnard & Bell 1993

Page 4: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

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BTEX Compounds Are Biodegradable

OH

OH COOHCOOH

Benzene Catechol cis, cis-Muconic acid

COOHCOOHO

beta-Ketoadipic Acid

O2

CHOCOOH

OH2-hydroxy-cis,cis-Muconic Semialdehyde

O2

acetaldehyde + pyruvic acid succinic acid + acetyl-CoA

Toxicology

Benzene Acute mylogenous leukemia Multiple myeloma

Tumors of bone marrow plasma cells

Aplastic anemia Affects formation of red and white blood cells/platelets

Nervous system affects at air levels of 100 ppmand above Drowsiness, lightheadedness, headache, delirium,

vertigo, naracosis leading to unconciousness

Benzene Metabolism &Pharmacodynamics (Mammal)

43% of administered dose expiredunmetabolized;

1.5% exhaled as CO2; 35% recovered as urinary metabolites;

23% phenol 4.8% hydroquinone 2.2% catechol 1-2% trans, trans-muconic acid

Mode of action may be through AhR signalingmechanism typical of dioxins, PCBs, andPAHs

O

O

C CHOOC

H

C CCOOH

H

trans, trans-Muconic Acid

OH OH

OH

OHOH

O

O

Phenol Hydroquinone

Glucuronide + Sulfate Conjugates

+

Catechol

p-Benzoquinone

Benzene

Oxepin

Benzene oxide

S N Acetyl Cysteine

Toxic Metabolites

Other Pathways Detoxifications

Benzene Risk Characterization

Estimated 8 X 10-6 risk for leukemiaassociated with breathing 1 µg/m3 (~0.4ppb) of benzene for 70 years

For drinking water, estimated 1 X 10-6

lifetime risk for concentration of 0.66ppb

VOCs Exposure(In Vehicle, µg/m3)

Urban InterstateMorning Evening Morning Evening

Benzene 11.6 15.9 10.8 9.1Toluene 19.0 75.8 38.5 30.7Ethylbenzene 9.5 13.9 7.4 6.0m/p-Xylene 33.3 46.0 25.7 20.6o-Xylene 12.8 17.1 9.5 7.81,3,5-trimethylbenzene 5.0 7.1 3.7 3.51,2,4-trimethylbenzene 17.3 24.1 13.0 11.0

Chan et al. 1991 (ES&T 25:964)

Page 5: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

5

Benzene Ethylbenzene CO (ppm)

Effect of ventilationconditions on airconcentrations of VOCsemitted from motor vehicles

Chan et al. 1991 (ES&T 25:964)

µg

/m3

µg

/m3

Isopentane Toluene m/p-xylene

Effect of ventilationconditions on airconcentrations of VOCsemitted from motor vehicles

Chan et al. 1991 (ES&T 25:964)

1,3 butadiene benzene

µg

/m3

Effect of “Place” on airconcentrations of VOCs emittedfrom motor vehicles

Chan et al. 1991 (ES&T 25:964)

isopentane toluene m/p-xylene

Effect of “Place” on airconcentrations of VOCs emittedfrom motor vehicles

µg

/m3

Chan et al. 1991 (ES&T 25:964)

Average Air Concentrations (µg/L air) from usingtap water with 1 mg/L of VOC.

Concentration of VOC(µg/L)

ShowerAir

BathroomAir

HouseholdAir 1

HouseholdAir 2

Carbon tetrachloride 18 3.6 0.12 0.024Chloroform 20 3.8 0.12 0.026DBCP 93 1.8 0.80 0.020EDB 19 3.8 0.12 0.025PCE (Perc)(=tetrachloroethylene)

17 3.4 0.11 0.023

TCE(trichloroethylene)

18 3.5 0.11 0.024

McKone 1987 (ES&T 21:1194)

TCE Occurrence in Water Supplies (Ground Water Systems)Serving Large (>10,000 persons) & Small (<10,000 persons)

The National Academy of Sciences estimated a onein a million life-time cancer risk from drinking waterof 4.5 ppb (EPA’s estimate was 2.8 ppb).

EPA Survey, 1984 Data

Type ofSystem

Type ofSamples

No. ofSamples

OccurrencesNumber

Occurrences%

Median(ppb)

Maximum(ppb)

Large Random 186 21 11.4 1.0 78Small Random 280 9 3.2 0.88 40Large Nonrandom 158 38 24.1 1.5 130Small Nonrandom 321 23 7.2 1.2 29

Page 6: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

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NOAEL = 0.1 mg/kg/day

Estimated Exposure (mg/kg/day)if TCE in Water = 3 ppm

Daily Dose (mg/kg bw) Body Weight70 kg 22 kg 10 kg

Drinking (oral) 0.086 0.204 0.3Showering Dermal Dermal + Inhalation Inhalation

0.0640.0830.099

0.10.129

Bathing (3 mg/L) Dermal (15 min) Dermal (5 min)

0.1540.051

0.240.08 0.08

Fan 1988 (Rev. Environ. Contam. Toxicol.)

CH

Cl

Cl

Cl

chloroform

CH

Cl

Cl

Br

bromodichloromethane

CH

Cl

Br

Br

dibromochloromethane

CH

Br

Br

Br

bromoform

Trihalomethanes (THMs)

Disinfection By-Products in Drinking Water

Risk of Spontaneous Abortion

Trihalomethanes(Disinfection By-Products--DBPs)

See lecture handout for epidemiological discussion Note that the studies suffer from lack of direct

exposure measurement, as with most chemicalepidemiological studies That is why biomarkers can be very useful

Recent biomarkers used for DBPs Froese et al., 2002, Trichloroacetic acid as a

biomarker of exposure to disinfection by-productsin drinking water, etc. Environ. Hlth. Perspectives110:679-687

Trichloroacetic acid Body half-life of about 2.3 - 3.7 days

60

70

80

90

100

Con

cent

ratio

n (µ

g/L)

Time (hours)0 1 2 3 4

Effect of time on THM concentration inwater in wide mouth glasses @ 25º C

Batterman et al. 2000

MTBE

•Water solubility: 23 - 55 g/L

•Log Kow: 0.9-1.2

•VP: 249 mm Hg

•KH: 5.9 x 10-4 atm-m3/mole

As little as 15 ppb in watercan be smelled; associatedwith complaints of “acute”health effects, but notconfirmed under controlledconditions.

OC

CH3

H3C

H3C

CH3

methyl tertiary butyl ether

DenverCo

NewEngland

DallasTX

RenoNV

AlbanyNY

Las VegasNV

AtlantaGa

AlbuquerqueNM (23)

(21)

(29)

(18)

(22)

(13)

(22)

(6)

Rep

ortin

g Le

vel

(0.2

µg

/L)

Est

imat

ed R

ange

for

US

EP

AH

ealth

Adv

isor

y (2

0-20

0 µ

g/L)

(#) Number of samplesWith concentrations

< reporting level

0.1 1 10 100 1,000 10,000 100,000

MTBE Concentration (µg/L)

Survey of MTBE Residuesin U.S. Ground Water

Squillace et al. 1996ES&T 30:1721

Page 7: BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... · 3 Note: concentration gradient tended to be weak; Suggests multiple sources (Wakeham et al. 1983) Mesocosm Experiment

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WellClassification(fuel type @ gasstation)

Numberof Wells

>1 µg/L-19 µg/L

≥20 µg/L-49 µg/L

≥50µg/L

Combined (wellsrepresenting allgas stations)

74 14(19%)

5 (7%) 2 (3%)

Conventionalgasoline

40 6 (15%) 1 (3%) 1 (3%)

ReformulatedGas/Oxyfuel(MTBE) *

34 8 (24%) 4 (12% 1 (3%)

Control wells (upgradient of gasstations

21 1 (5%) 0 0

Prevalence of MTBE in Wells as Influenced by Proximity toGas Station Using Reformulated Fuel or Conventional Fuel

Lince et al. 2001 (ES&T 35:1050)

Ecotoxicological Consequences ofMTBE in Surface Water??

Surface waters in California had MTBE as a result ofexhaust and discharges of watercraft using MTBEoxygenated fuel

Incomplete combustion also emitted a lot of PAHs One of the most common PAHs found in surface water

with motorized boats is fluoranthene In the presence of sunlight, PAHs become very toxic to

aquatic organisms Is there any toxicological interaction between MTBE and a

PAH??

fluoranthene

Uptake and Depuration of Fluoranthene in thePresence or Absence of MTBE

Cho et al. 2003 (ES&T 37:1306)

Fluoranthene [20 µg/L]MTBE [40 µg/L]

Effect of Fluoranthene on Survivability of Fathead Minnowin the Presence of Absence of MTBE

Flu = fluoranthene

Cho et al. 2003

µg/L


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