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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
2
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)
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
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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)
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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
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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
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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