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BETX (benzene, ethylbenzene, toluene, xylene) ESRP 532 ... 3 Note: concentration gradient tended to

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  • 1

    ESRP 532 Applied Environmental Toxicology

    Lecture 19 Volatile Organic Compounds

    (VOCs)

    afelsot@tricity.wsu.eduhttp://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

    carbon tetrachloride

    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

  • 3

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

    (Wakeham et al. 1983)

    Mesocosm Experiment

    Compound Winter T1/2

    Summer T1/2

    T1/2, summer, (Sterile)

    T1/2, summer, (Natural)

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

    Wakeham et al. 1983

    Half-life of Selected VOCs Evidence for Biodegradation

    Atmospheric Lifetimes Ambient Concentration Measurements

    Compound # of

    Locations Sampled

    # of Samples Median or

    range (µg/m3)

    Lifetime in Air (days)

    benzene >140 >10,000 5.1 >5 ethylbenzene 93 8723 1.1

  • 4

    BTEX Compounds Are Biodegradable

    OH

    OH COOH COOH

    Benzene Catechol cis, cis-Muconic acid

    COOH COOHO

    beta-Ketoadipic Acid

    O2

    CHO COOH

    OH 2-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 ppm and above  Drowsiness, lightheadedness, headache, delirium,

    vertigo, naracosis leading to unconciousness

    Benzene Metabolism & Pharmacodynamics (Mammal)

     43% of administered dose expired unmetabolized;

     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 signaling mechanism typical of dioxins, PCBs, and PAHs

    O

    O

    C C HOOC

    H

    C C COOH

    H

    trans, trans-Muconic Acid

    OH OH

    OH

    OH OH

    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 leukemia associated with breathing 1 µg/m3 (~0.4 ppb) of benzene for 70 years

     For drinking water, estimated 1 X 10-6 lifetime risk for concentration of 0.66 ppb

    VOCs Exposure (In Vehicle, µg/m3)

    Urban Interstate Morning Evening Morning Evening

    Benzene 11.6 15.9 10.8 9.1 Toluene 19.0 75.8 38.5 30.7 Ethylbenzene 9.5 13.9 7.4 6.0 m/p-Xylene 33.3 46.0 25.7 20.6 o-Xylene 12.8 17.1 9.5 7.8 1,3,5-trimethylbenzene 5.0 7.1 3.7 3.5 1,2,4-trimethylbenzene 17.3 24.1 13.0 11.0

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

  • 5

    Benzene Ethylbenzene CO (ppm)

    Effect of ventilation conditions on air concentrations of VOCs emitted from motor vehicles

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

    µ g

    /m 3

    µ g

    /m 3

    Isopentane Toluene m/p-xylene

    Effect of ventilation conditions on air concentrations of VOCs emitted from motor vehicles

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

    1,3 butadiene benzene

    µ g

    /m 3

    Effect of “Place” on air concentrations of VOCs emitted from motor vehicles

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

    isopentane toluene m/p-xylene

    Effect of “Place” on air concentrations of VOCs emitted from motor vehicles

    µ g

    /m 3

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

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

    Concentration of VOC (µg/L)

    Shower Air

    Bathroom Air

    Household Air 1

    Household Air 2

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

  • 6

    NOAEL = 0.1 mg/kg/day

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

    Daily Dose (mg/kg bw) Body Weight 70 kg 22 kg 10 kg

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

    0.064 0.083 0.099

    0.1 0.129

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

    0.154 0.051

    0.24 0.08 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 chemical epidemiological 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-products in drinking water, etc. Environ. Hlth. Perspectives 110:679-687

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

    60

    70

    80

    90

    100

    C on

    ce nt

    ra tio

    n (µ

    g/ L)

    Time (hours) 0 1 2 3 4

    Effect of time on THM concentration in water 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 water can be smelled; associated with complaints of “acute” health effects, but not confirmed under controlled conditions.

    O C

    CH3 H3C

    H3C

    CH3

    methyl tertiary butyl ether

    Denver Co

    New England

    Dallas TX

    Reno NV

    Albany NY

    Las Vegas NV

    Atlanta Ga

    Albuquerque NM (23)

    (21)

    (29)

    (18)

    (22)

    (13)

    (22)

    (6)

    R ep

    or tin

    g Le

    ve l

    (0 .2

    µ g

    /L )

    E st

    im at

    ed R

    an ge

    fo r

    U S

    E P

    A H

    ea lth

    A dv

    is or

    y (2

    0- 20

    0 µ

    g/ L)

    (#) Number of samples With concentrations

    < reporting level

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

    MTBE Concentration (µg/L)

    Survey of MTBE Residues in U.S. Ground Water

    Squillace et al. 1996 ES&T 30:1721

  • 7

    Well Classification (fuel type @ gas station)

    Number of Wells

    >1 µg/L- 19 µg/L

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