United States
Envtonmental ftotecoon
Agency
Office of Water
Regiiabons and Standards
Criteria and Standards Division
Washington DC 2M60
EPA 440, 5-80018
October 1980
vvEPA
Ambient
Water Quality
Criteria for
Benzene
V
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AMBIENT WATER QUALITY CRITERIA FOR
BENZENE
Prepared By
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Regulations and Standards
Criteria and Standards Division
Washington, O.C.
Office of Research and Development
Environmental Criteria and Assessment Office
Cincinnati, Ohio
Carcinogen Assessment Group
Washington, O.C.
Environmental Research Laboratories
Corvalis, Oregon
Duluth, Minnesota
Gulf Breeze, Florida
Narragansett, Rhode Island
-------
DISCLAIMER
This report has been reviewed by the Environmental Criteria and
Assessment Office, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
AVAILABILITY NOTICE
This document is available to the public through the National
Technical Information Service, (NTIS), Springfield, Virginia 22161.
11
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FOREWORD
Section 304 (a)(l) of the Clean Water Act of 1977 (P.L. 95-217),
requires the Administrator of the Environmental Protection Agency to
publish criteria for water quality accurately reflecting the latest
scientific knowledge on the kind and extent of all identifiable effects
on health and welfare which may be expected from the presence of
pollutants in any body of water, including ground water. Proposed water
quality criteria for the 65 toxic pollutants listed under section 307
(a)(l) of the Clean Water Act were developed and a notice of their
availability was published for public comment on March 15, 1979 (44 FR
15926), July 25, 1979 (44 FR 43660), and October 1, 1979 (44 FR 56628).
This document is a revision of those proposed criteria based upon a
consideration of comments received from other Federal Agencies, State
agencies, special interest groups, and individual scientists. The
criteria contained in this document replace any previously published EPA
criteria for the 65 pollutants. This criterion document is also
published in satisifaction of paragraph 11 of the Settlement Agreement
in Natural Resources Defense Counci1. et. a 11.. ys. Tra i n, 8 ERC 2120
(D.D.C. 1976), modified, 12 ERC 1833 (D.D.C. 1979).
The term "water quality criteria" is used in two sections of the
Clean Water Act, section 304 (a)(l) and section 303 (c)(2). The term has
a different program impact in each section.- In section 304, the term
represents a non-regulatory, scientific assessment of ecological ef-
fects. The criteria presented in this publication are such scientific
assessments. Such water quality criteria associated with specific
stream uses when adopted as State water quality standards under section
303 become enforceable maximum acceptable levels of a pollutant in
ambient waters. The water quality criteria adopted in the State water
quality standards could have the same numerical limits as the criteria
developed under section 304. However, in many situations States may want
to adjust water quality criteria developed under section 304 to reflect
local environmental conditions and human exposure patterns before
incorporation into water quality standards. It is not until their
adoption as part of the State water quality standards that the criteria
become regulatory.
Guidelines to assist the States in the modification of criteria
presented in this document, in the development of water quality
standards, and in other water-related programs of this Agency, are being
developed by EPA.
STEVEN SCHATZOW
Deputy Assistant Administrator
Office of Water Regulations and Standards
111
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ACKNOWLEDGEMENTS
Aquatic Life Toxicology:
William A. Brungs, ERL-Narragansett John H. Gentile, ERL-Narragansett
U.S. Environmental Protection Agency U.S. Environmental Protection Agency
Mammalian Toxicology and Human Health Effects:
Normal Kowal, HERL-Cin Herbert Cornish
U.S. Environmental Protection Agency University of Michigan
Oebdas Mukerjee (doc. mgr.) ECAO-Cin Patrick Durkin
U.S. Environmental Protection Agency Syracuse Research Corp.
Jerry F. Stara (doc. mgr.) ECAO-C1n Penelope A. Fenner-Crisp, ODW
U.S. Environmental Protection Agency U.S. Environmental Protection Agency
Elliot Lomnitz, OCS Myron Mehlman
U.S. Environmental Protection Agency Mobil Oil Corp.
Si Duk Lee, ECAO-Cin Roy E. Albert, CAG*
U.S. Environmental Protection Agency U.S. Environmental Protection Agency
Benjamin Van Duuren
New York University Medical Center
Technical Support Services Staff: D.J. Reisman, M.A. Garlough, B.L. Zwayer,
P.A. Daunt, K.S. Edwards, T.A. Scandura, A.T. Pressley, C.A. Cooper,
M.M. Denessen.
Clerical Staff: C.A. Haynes, S.J. Faehr, L.A. Wade, D. Jones, B.J. Bordicks,
B.J. Quesnell., T. Highland, B. Gardiner.
*CAG Participating Members: Elizabeth L. Anderson, Larry Anderson, Ralph Arnicar,
Steven Bayard, David L. Bayliss, Chao W. Chen, John R. Fowle III, Bernard Haberman,
Charalingayya Hiremath, Chang S. Lap, Robert McGaughy, Jeffrey Rosenblatt,
Dharm V. Singh, and Todd W. Thorslund.
IV
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TABLE OF CONTENTS
Page
Criteria A-1
Introduction B-1
Aauatic Life Toxicology B-1
Introduction B-1
Effects B-1
Acute Toxicity B-1
Chronic Toxicity B-2
Plant Effects B-3
Residues B-3
Miscellaneous B-3
Summary B-4
Criteria B-4
References B-13
Mammalian Toxicology and Human Health Effects C-l
Exposure C-l
Ingestion C-l
Inhalation C-8
Dermal C-8
Pharmacokinetics C-9
Absorption C-9
Distribution C-9
Metabolism C-10
Excretion C-14
Effects C-l6
Acute, Subacute and Chronic Toxicity C-l6
Synergism and/or Antagonism C-35
Teratogenicity C-36
Mutagenicity C-44
Carcinogenicity C-48
Criterion Formulation C-61
Existing Guidelines and Standards C-61
Current Levels of Exposure C-61
Special Groups at Risk C-62
Basis and Derivation of Criterion C-62
References C-67
Appendix C-101
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CRITERIA DOCUMENT
BENZENE
CRITERIA
Aquatic Life
The available data for benzene indicate that acute toxicity to fresh-
water aquatic life occurs at concentrations as low as 5,300 pg/1 and would
occur at lower concentrations among species that are more sensitive than
those tested. No data are available concerning the chronic toxicity of ben-
zene to sensitive freshwater aquatic life.
The available data for benzene indicate that acute toxicity to saltwater
aquatic life occurs at concentrations as low as 5,100 wg/l and would occur
at lower concentrations among species that are more sensitive than those
tested. No definitive data are available concerning the chronic toxicity of
benzene to sensitive saltwater aquatic life, but adverse effects occur at
concentrations as low as 7QO yg/1 with a fish species exposed for 168 days.
Human Health
For the maximum protection of human health from the potential carcino-
genic effects due to exposure of benzene through ingestion of contaminated
water and contaminated aquatic organisms, the ambient water concentrations
should be zero based on the non-threshold assumption for this chemical.
However, zero level may not be attainable at the present time. Therefore,
the levels which may result in incremental increase of cancer risk over the
lifetime are estimated at 10~^, 10 , and 10 . The corresponding
recommended criteria are 6.6 ug/1, 0.66 ng/1, and 0.066 ug/l» respectively.
If the above estimates are made for consumption of aquatic organisms only,
excluding consumption of water, the levels are 400 ug/1, 40.0 wg/1, and 4.0
wg/1, respectively.
VI
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INTRODUCTION
Benzene is a volatile, colorless, liquid hydrocarbon produced principal-
ly from coal tar distillation and from petroleum by catalytic reforming of
light naphthas from which it is isolated by distillation or solvent extrac-
tion (Weast, 1972; Ayers and Muder, 1964; U.S. EPA, 1976). It is also pro-
duced in coal processing and coal coking operations. The broad utility
spectrum of benzene (commercially sometimes called "Benzol") includes its
use as: an intermediate for synthesis in the chemical and pharmaceutical in-
dustries including the manufacture of styrene, cyclohexane, detergents, and
pesticides, a thinner for lacquer, a degreasing and cleaning agent, a sol-
vent in the rubber industry, an antiknock fuel additive, a general solvent
in laboratories, a solvent for industrial extraction and rectification, and
in the preparation and use of inks in the graphic arts industries.
In the United States today, benzene is used extensively (over 4 million
metric tons annually) in the chemical industry and its use is expected to
increase when additional production facilities become available (Pick, 1976).
Benzene has the molecular formula CgHg and a molecular weight of
78.1 (Weast, 1972; Ayers and Muder, 1964). Pure benzene has a boiling point
of 80.1*C and a melting point of 5.5*C (Weast, 1972). Benzene has a density
less than that of water (0.87865 at 20*C) (Weast, 1972; Stecher, 1968).
The solubility and volatile nature of benzene indicate possible environ-
mental mobility. Benzene has been detected at various concentrations in
lakes, streams, and finished drinking water. Benzene has been detected in
finished drinking water (U.S. EPA, 1975), in water and sediments samples
from the lower Tennessee River in ppb concentrations (Goodley and Gordon,
1976) and in the atmosphere (Howard and Durkin, 1974).
A-l
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REFERENCES
Ayers, G.W. and R.E. Muder. 1964. Kirk-Othmer Envyclopedia of Chemical
Technology. 2nd ed. John Wiley and Sons, Inc., New York.
Pick, J.E. 1976. To 1985: U.S. benzene supply/demand. Hydrocarbon Pro-
cessing. 55: 127.
Goodley, P.C. and M. Gordon. 1976. Characterization of industrial organic
compounds in water. Trans. Kentucky Academy of Science. 37(1-2): 11.
Howard, P.H. and P.R. Ourkin. 1974. Sources of contamination, ambient
levels, and fate of benzene in the environment. EPA 560/5-75-005. U.S. En-
viron. Prot. Agency, (Office of Toxic Substances), Washington, D.C. p. 65.
Stecher, P. (ed.) 1968. The Merck Index. Merck and Co., Rahway, New
Jersey.
U.S. EPA. 1975. Preliminary assessment of suspected carcinogens in
drinking water. U.S. Environ. Prot. Agency, (Office of Toxic Substances),
Washington, Q,C, p, 33,
U.S. EPA. 1976. Health effects of benzene: a review. U.S. Environ. Prot.
Agency, Washington, D.C.
Weast, R.C. 1972. Handbook of Chemistry and Physics. The Chemical Rubber
Co., Cleveland, Ohio.
A-2
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Aquatic Life Toxicology*
INTRODUCTION
Most of the toxicity data concerning the effects of benzene on aauatic
life have been determined using static test conditions without measured con-
centrations. Conseauently, these data may underestimate the toxicity of
this volatile chemical. Nearly all of the adverse acute and chronic effects
occurred at cotcentrations above 5,000 ug/1. However, some data (Struh-
saker, 1977) 1n Table 5 indicate that uniaue acute effects may occur at ben-
zene concentrations as low as 700 ug/1.
EFFECTS
Acute Toxicity
Two freshwater invertebrate species, Daphnia magna and Daphnia pulex,
have been tested using static conditions (U.S. EPA, 1978; Canton and Adema,
1978). The 48-hour effect concentrations ranged from 203,000 to 620,000
ug/1 (Table 1). The species acute values for Daphnia magna and Daphnia p_ul_ejx
are 380,000 and 300,000 ug/1 which result indicates no appreciable differ-
ence in sensitivity.
Six freshwater fish species representing four families have been tested
with benzene, and the 96-hour LC5Q values ranged from 5,300 ug/1 for the
rainbow trout under flow-through test conditions with measured concentra-
tions to 386,000 ug/1 for the mosouito fish (Table 1). Because of the dif-
ference in test methods for the rainbow trout and the other five species, on
The reader is referred to the Guidelines for Deriving Water Quality Criteria
for the Protection of Aouatic Life and Its Uses in order to better
understand the following discussion and recommendation. The following
tables contain the appropriate data that were found in the literature, and
at the bottom of each table -are calculations for deriving various measures
of toxicity as described in the Guidelines.
8-1
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which tests were conducted under static conditions without measured
concentrations, one cannot conclude whether this difference is due to
different sensitivity or test methods. Two additional non-standard tests
with salmonid species yielded LC5Q and LC30 results of 12,000 and 15,100
ug/1 (Table 5).
Several saltwater invertebrate and one fish species have been studied
(Table 1). There was ouite a bit of variability among the invertebrate spe-
cies with a range of effect concentrations of 17,600 to 924,000 ug/1. The
striped bass was more sensitive with 96-hour IC™ values of 10,900 and
5,100 ug/1.
Potera (1975) conducted a variety of 24-hour exposures with the grass
shrimp, Palaemonetes puqio, using static procedures with measured concentra-
tions (Table 5). Temperature (10 and 20*C), salinity (15 and 25 ppt), and
life stage (larvae and adults) were the variables considered. The total
range of LC^ values for the six tests was 33,500 to 90,800 ug/1 which
small difference indicates that the variables did not have a very great ef-
fect. This difference in salinity was also evaluated for the copepod, Nv-
tocra spim'pes, and the 24-hour LCgQ values were 82,000 ug/1 at 15 ppt
salinity and 111,500 ug/1 at 25 ppt (Table 5).
In both freshwater and saltwater systems, the fish species appear to be
more sensitive than the invertebrate species.
Chronic Toxicity
A chronic test with Oaphnia magna was conducted (U.S. EPA, 1978) but the
results were incomplete. No adverse effects were observed at test concen-
trations as high as 98,000 ug/1 (Table 2). It is interesting to note that
the species acute value for this species is 380,000 ug/1 (Table 1) which in-
dicates only a relatively small difference between the acute and chronic ef-
fects of benzene on this species.
B-2
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No chronic toxicity data are available for any freshwater or saltwater
species.
A summary of species acute and chronic values is listed in Table 3.
Plant Effects
Kauss and Hutchinson (1975) determined that there was a 50 percent re-
duction in the cell numbers of Chlorella vulgaris after 48 hours at a con-
centration of 525,000 ug/1 (Table 4).
Three saltwater algal or diatom species have been tested (Dunstan et
al., 1975; Atkinson et al., 1977) and growth was inhibited at benzene con-
centrations of 20,000 to 100,000 ug/1 (Table 4).
Residues
No measured steady-state bioconcentration factor is available for ben-
zene.
Miscellaneous
The 96-hour LC^g for the fathead minnow using flow-through methods
with measured concentrations was 15,100 ug/1 (Table 5), which result is not
too different from the static test results for the 96-hour LC5Q values of
33,470 and 32,000 wg/l (Table 1).
Struhsaker (1977) exposed female Pacific herring to 700 ug/1 for 48
hours just prior to their spawning. Survival of embryos at hatching and
survival of larvae upon continued exposure through yolk absorption were re-
duced (Table 5). The results of this study need further verification before
such effects may be used to derive a criterion for saltwater organisms. On-
ly one test concentration was used to determine the effects of benzene on
embryo survival and survival of larvae; a no-effect concentration was not
determined. Also the adult fish were captured from San Francisco Bay waters
which, as stated by the authors, may affect the hatchability of Pacific her-
ring eggs due to the effects of accumulated pollutants in the adults' gonads.
B-3
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The data by Potera (1975) were discussed earlier.
Summary
The acute toxicity of benzene to freshwater species has been measured
with eight species and the species acute values range from 5,300 ug/1 to
386,000 vg/1. No data are available for benthic crustaceans, benthic in-
sects, or detritivores. However, the most important deficiency may be that
only with the rainbow trout were the results obtained from a flow-through
test and based on measured concentrations. Results based on unmeasured con-
centrations in static tests are likely to underestimate toxicity for com-
pounds like benzene that are relatively volatile.
A life cycle test was conducted with one freshwater species, Daphnia
magna, but no concentration up to 98,000 ug/1 caused an adverse effect. On
the other hand, concentrations which apparently did not adversely affect
Daphnia magna in a life cycle test did affect other species in acute tests.
For saltwater species, species acute values are available for one fish
•
species and five invertebrate species and range from 10,900 to 924,000
ug/1. These values suggest that saltwater species are about as sensitive as
freshwater species. The one acute value from a flow-through test in which
toxicant concentrations were measured was not the lowest value, as was the
case with the freshwater acute data. Saltwater plants seem to be about as
sensitive as saltwater animals. Other data indicate that herring may have
suffered stress and some mortality at 700 wg/1.
CRITERIA
The available data for benzene indicate that acute toxicity to
freshwater aquatic life occurs at concentrations as low as 5,300 ug/1 and
would occur at lower concentrations among species that are more sensitive
than those tested. No data are available concerning the chronic toxicity of
benzene to sensitive freshwater aquatic life.
B-4
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The available data for benzene indicate that acute toxicity to saltwater
aquatic life occurs at concentrations as low as 5,100 u9/l and would occur
at lower concentrations among species that are more sensitive than those
tested. No definitive data are available concerning the chronic toxicity of
benzene to sensitive saltwater aquatic life but adverse effects occur at
concentrations as low as 700 ug/1 with a fish species exposed for 168 days.
B-5
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Table 1. Acut« value* for benzon*
5p*cies
nvtituu*
LC50/EC50
i|ig/i>
Sp«cl«s MMO
Acute ValtM
(iiy/ii RvroreriCtt
FRESHWATER SPECIES
Cladoceran,
Daphnla matins
Cladoceran,
Daphnla magna
Cladoceran,
Daphnla magna
Cladoceran,
Daphnla magna
Cladoceran,
Daphnla magna
Cladoceran,
Daphnla magna
Cladoceran,
Daphnla macjna
Cladoceran,
Daphnla pulex
Cladoceran,
Daphnla pulex
Rainbow trout (juvenile).
Sal mo galrdnerl
Goldfish,
Car ass 1 us auratus
Fathead minnow,
Plmephales prone las
Fathead minnow.
s,
s,
s.
s.
s.
s,
s,
s,
s,
FT,
s,
s,
s.
U
u
u
u
0
u
u
u
u
M
U
U
u
203,000
400,000
620,000
412,000
412,000
356,000
356,000
345,000
265,000
5,300
34,420
33,470
32,000
U.S. EPA, 1978
Canton 4 Adema, 1978
Canton & Adema, 1978
Canton & Adema, 1978
Canton & Adema, 1978
Canton & Adema, 1978
380,000 Canton & Adema, 1978
Canton 4 Adama, 1978
300,000 Canton & Adema, 1978
5,300 OeGraeve, et al. 1980
34,000 Pickering & Henderson,
1966
Pickering & Henderson,
1966
33,000 Pickering & Henderson,
Plmephalos prone I as
1966
B-6
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Table t. (Continued)
Species
Guppy.
Poecilla ret leu lot a
Mosqultoflsh,
Ganbusla aff inls
eiuegill,
LapCMis macrochlrus
Pacific oyster,
Crassostrea glgas
Copepod,
Tlgrlopus callfornlcus
Bay shrl«p,
Craqo francl&coru»
Grass shrlnp,
PalaeMonetes puglo
Oungeness crab (larva).
Cancer naglster
Striped bass,
Morons saxatl Us
Striped bass,
Morone saxatl 1 is
Method*
— «^^HHMi^
s, u
s, u
s, u
s, u
S, M
S, M
S, U
S. U
FT, M
S, M
SpaclM Mww
LC50/EC50 Acute Valu*
(va/D (uo/l)
36.600
386,000
22,490
SALTWATER SPECIES
924,000
450,000
17,600
27,000
108,000
10,900
5,100
36,600
386,000
22,000
924,000
450,000
17,600
27,000
108,000
10,900
Refareoc*
Pickering & Henderson,
1966
Mallen, et al. 1957
Pickering & Henderson,
1966
LeGore, 1974
Korn, et al. 1976
Benvllte & Korn, 1977
Tate*, 1975
Caldwell, et al. 1977
Mayerhoff, 1975
Benvl 1 le & Korn, 1977
* S » static, FT = flow-through, U « unmeasured, M * measured
B-7
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Table 2. Chronic values for benzene (U.S. EPA. 1978)
ClM-onlc
LlMlts Value
Specie* Te»t« (up/1) (ng/1)
FRESHWATER SPECIES
Cladoceran, LC >98.000 >96,000
Daphnla nagna
• LC - lit* cycle or partial life cycle
B-8
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Table 3. Species Mean acute and acute-chronic ratios for benzene
tnk*
8
7
6
5
4
3
2
1
6
5
4
3
Species
Mosqultoflsh,
Gambusla of tin is
Cladoceran,
Daphnla magna
C 1 adoceran ,
Daphnla pulex
Guppy,
Poecl 1 la retlculata
Goldfish,
Carassius auratus
Fathead minnow,
Plmephales promalas
Bluegill,
Leponls macrochlrus
Rainbow trout.
Sal mo galrdnerl
Paclf Ic oyster,
Crassostrea algas
Copepod ,
Tlgrlopus callfornlcus
Dungeness crab.
Cancer ma^ister
Grass shrimp,
Species Mean
Acute Value
(M.q/D
FRESHWATER SPECIES
386,000
380,000
300,000
36,600
34,000
33,000
22,000
5,300
SALTWATER SPECIES
924,000
450,000
108,000
27,000
Acute-Chron 1 c
Ratio
-
Pa Iaemonetes puglo
B-9
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Table 3. (Continued)
Rank*
2
1
Specie*
Bay shrlop,
Crago franclscoru*
Striped bass,
Morona saxat Ills
Specie* Naan
Acut* Valu*
(tffl/l)
17,600
10.900
Acwt*-Chra«lc
Ratio
-
* Ranked from least sensitive to Most sensitive based on species Mean
acute value.
B-10
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Table 4. Plant values for benzene
Species
Alga.
Chloral la vulgar Is
0 1 not lagel late,
Amphidlnlim carterae
Diatom,
Skeletonema costatum
01 atom,
Skeletonema costatum
Alga,
Crlcosphaera carterae
Result
Effect (MQ/I)
FRESHWATER SPECIES
48-hr EC50 525,000
50$ reduction
In eel 1 numbers
SALTWATER SPECIES
Growth >50,000
Inhibition
Growth 100,000
Inhibition
Growth 20,000
Inhibition
Growth 50,000
Inhibition
Reference
Kauss & Hutch Inson,
1975
Ounstan. et al. 1975
Dunstan, et al. 1975
Atkinson, et al. 1977
Dunstan, et al. 1975
B-ll
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Tat I* 5. OtftM- fete for bMUMM
Specie*
RWMlt
Brown trout,
Salmo trutta
Fathead minnow,
Plmephales prome-las
Copepod,
Nltocra splnlpes
Copepod,
Nltocra splnlpes
Grass shrimp (adult).
Pa 1 aemonetes pugio
Grass shrimp (adult),
Palaemonetes pugio
Grass shrimp (adult),
Palaemonetes fiuglo
Grass shrimp (adult),
Palaemonetes pugio
Grass shrimp (larva),
Palaemonetes pugio
Grass shrimp (larva),
Palaemonetes pugio
Pacific herring,
Clupea harengus pallasl
Pacific herring,
Clupea harengus pallasl
FRESHWATER SPECIES
1 hr or LC50
24 hrs
96 hrs LC30
SALTWATER SPECIES
24 hrs LC50
24 hrs LC50
24 hrs LC50
24 hrs LC50
24 hrs LC50
24 hrs LC50
24 hrs LC50
24 hrs LC50
144 hrs Stress observed
168 hrs Survival reduction
12,000
15,100
82,000
111,500
38,000
33,500
40,200
40,800
90,800
74,400
700
700
Woodlwlss & Fretwell,
1974
DeSraeve, et al. 1980
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Potera, 1975
Struhsaker, 1977
Struhsaker, 1977
Striped bass,
Morone saxatIlls
168 hrs Temporary weight 6,000
reduction
Korn, et al. J976
B-12
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REFERENCES
Atkinson, 1.P., et al. 1977. The analysis and control of volatile hydro-
carbon concentrations (e.g., benzene) during oil bioassay. Water Air Water
Pollut. 8: 235.
Benville, P.E., Jr. and S. Korn. 1977. The acute tbxicity of six monocy-
clic aromatic crude oil components to striped bass (Morone saxatilis) and
bay shrimp (Crago franciscorum). Calif. Fish Game. 63: 204.
Caldwell, R.S., et al. 1977. Effects of a seawater soluble fraction of
Cook Inlet crude oil and its major aromatic components on larval stages of
the dungeness crab, Cancer magister. In: D.A. Wolfe (ed.), Fate and
Effects of Petroleum Hydrocarbons in Marine Organisms and Ecosystems.
Pergammon Press, p. 210.
Canton, J.H. and D.M.M. Adema. 1978. Reproducibility of short-term and
reproduction toxicity experiments with Daphnia magna and comparison of the
sensitivity of Daohnia magna with Oaphnia pulex and Daphnia cucullata in
short-term experiments. Hydrobiol. 59: 135.
OeGraeve, G.M., et al. 1980. Effects of naphthalene and benzene on fathead
minnows and rainbow trout. Trans. Amer. Fish. Soc. (Submitted).
Ounstan, W.M., et al. 1975. Stimulation and inhibition of phytoplankton
growth by low molecular weight hydrocarbons. Mar. Biol. 31: 305.
8-13
-------
Kauss, P.B. and T.C. Hutchinson. 1975. The effects of water-soluble
petroleum components on the growth of Chi ore 11 a vulqaris Beijerinck.
Environ. Pollut. 9: 157.
Korn, S., et al. 1976. Effect of benzene on growth, fat content and calo-
rie content of striped bass (Morone saxatilis). Fish. Bull. 74: 694.
LeGore, R.S. 1974. The effect of Alaskan crude oil and selected hydrocar-
bon compounds on embryonic development of the Pacific oyster, Crassostrea
gigas. Ph.D. Dissertation. Univ. of Washington.
Meyerhoff. R.O. 1975. Acute toxicity of benzene, a component of crude oil.
to juvenile striped bass. Jour. Fish. Res. Board Can. 32: 1864.
Pickering, Q.H. and C. Henderson. 1966. Acute toxicity of some important
petrochemicals to fish. Jour. Water Pollut. Control Fed. 38: 1419.
Potera, F.T. 1975. The effects of benzene, toluene and ethylbenzene on
several important members of the estuarine ecosystem. Ph.D. Dissertation.
Lehigh Univ.
Struhsaker, J.W. 1977. Effects of benzene (a toxic component of petro-
leum) on spawning Pacific herring, Clupea harengus pall asi. Fish. Bull.
75: 43.
B-14
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Tatem, H.E. 1975. Toxicity and physiological effects of oil and petroleum
hydrocarbons on estuarine grass shrimp, Paleomonetes puqio. Ph.D. Disserta-
tion. Texas A.M. Univ.
U.S. EPA. 1978. In-depth studies on health and environmental impacts of
selected water pollutants. U.S. Environ. Prot. Agency, Contract No.
68-01-4646.
Wallen, I.E., et al. 1957. Toxicity to Gambusia affinis of certain pure
chemicals in turbid waters. Sewage Fndust. Wastes 29: 695.
Woodiwiss, F.S., and G. Fretwell. 1974. The toxicities of sewage efflu-
ents, industrial discharges and some chemical substances to brown trout Sal-
mo trutta in the Trent River Authority Area. Water Pollut. Control Fed.
73: 396.
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Mammalian Toxicology and Human Health Effects
EXPOSURE
Ingestion
Benzene is soluble in water (1,780 mg/1 at 25*C) but human exposure
through food and water is difficult to quantify because of a relative pau-
city of data. Four of ten water supplies surveyed by the EPA utilizing vol-
atile organic analysis (VOA) contained benzene at concentrations of 0.1 to
0.3 ug/1; the highest concentration ever reported in a finished water was 10
ug/1 (U.S. EPA, 1975; NAS, 1977).
Only limited data on benzene in water are available. A review of ben-
zene sampling data by Howard and Durkin (1974) found that the^ few freshwater
samples analyzed by that time showed only trace levels of benzene. For ex-
ample, a 1972 EPA study cited in the report identified 53 organic chemicals,
ranging from acetone to toluene, in the finished waters and organic waste
effluents in 11 plants (of 60 sampled) discharging into the Mississippi
River. Benzene was not detected in the effluents, but the trace detected in
the finished waters suggested another source than effluent discharge.
A recent sampling of five benzene production or consumption plants by
Battelle (1977) found benzene levels in water ranging from <1.0 to 179.0 ppb
(plant effluent). The concentrations at 13 upstream and downstream sample
locations in nearby receiving waters, however, ranged from <1.0 to 13.0 ppb,
with an average of 4.0 ppb.
A recent report by the National Cancer Institute (NCI, 1977) noted ben-
zene levels of 0.1 to 0.3 ppb in four U.S. city drinking water supplies.
One measurement from a groundwater well in Jacksonville, Florida showed
levels higher than 100 ppb. No indication is given in the report of the
sampling methods or the analytical procedures. Howard and Ourkin (1974)
tabulated environmental monitoring data for benzene in ambient air and water
(Table 1).
C-l
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TABLE 1
Environmental Monitoring Data for Benzene In Ambient Air and Water*
REFERENCE*
Gordon and
Goodley (1971)
U.S. EPA
(1972)
Frlloux (1971)
Novak, et al.
(1973)
Williams
(1965)
Smoyer, et al.
•(1971)
Neligan, et al.
(196$)
TYPE OF
SAMPLE
Water
and mud
Finished
water
Finished
water
"Polluted"
and "pure"
drinking
water
Ambient
air
Ambient
air
Ambient
air
GEOGRAPHICAL
LOCATION
Lower
Tennessee
River
Carroll ton
Plant,
New Orleans
U.S. PHS
Hospital
Carvllle, La.
Prague,
Czecho-
slovakia
Vancouver,
Canada
Vicinity of
solvent
reclamation
plant
Los Angeles
basin
SAMPLING
METHOD3
CCE liquid -
liquid
extract
CCE
CCE
Inert gas
stripping
Cold trap -
GC column
Grab sample
Cold trap -
firebrick
ANALYSIS
TECHNIQUE*
GC/MS
GC
GC
GC,
GC/MS
Rapid
heating
into GC
Direct
ingest ion
Into GC; MS,
IR
Rapid
heating
QUANTITIES
DETECTED
Not
reported
Not
attempted
"trace"
ppb-ppm
range
0.1 ppb
1-10 ppb
23 ppm
0.005-0.022
ppm (V/V)
-------
TABLE 1 (continued)
Environmental Monitoring Data for Benzene in Ambient Air and Water*
REFERENCE*
Altschuller
and Bellar
(1963)
Lonneman,
et al. (1968)
Grob and Grob
(1971)
Stephens
(1973)
Pilar and
Graydon (1973)
TYPE OF
SAMPLE
Ambient
air
Ambient
air
Ambient
air
Ambient
air
Ambient
air
GEOGRAPHICAL
LOCATION
Downtown Los
Angeles
Los Angeles
basin
Zurich,
Switzerland
Riverside,
California
Toronto,
Canada
SAMPLING
METHOD^
Grab sample
Cold trap -
glass
beads
Charcoal
trap -
carbon
disulfide
extract
Cold trap -
GC column
Cold trap -
GC column
ANALYSIS
TECHNIQUE*
direct
injection
into GC
rapid
heading
into GC
GC-MS
GC-FL
GC-FL
GC-FL
QUANTITIES
DETECTED
0.015-0.06
ppm (V/V)
aver. 0.015
ppm; highest
0.057 ppm
(V/V)
0.054 ppm
0.007-0.008
ppm
aver. 0.013
ppm; highest
0.098 ppm
aCCE - carbon chloroform extract, GC - gas chromatography, FL - flame ionization,
IR - infrared spectrometry, MS - mass spectrometry.
*Source: Howard and Durkin, 1974.
03
-------
One possible source of benzene in the aquatic environment is from cycl-
ings between the atmosphere and water (Mitre Corp., 1976). Benzene is fair-
ly volatile (high vapor pressure of 100 mm Hg at 26*C) and has a relatively
high solubility (1,780 mg/1 at 25*C). Consequently, it is reasonable to be-
lieve that benzene could be washed out of the atmosphere with rainfall and
then be evaporated back into the atmosphere, causing a continuous recycling
between the two media. Benzene is also expected to be photooxidized in air
and otherwise biodegraded in the environment.
The exposure to benzene through general dietary intake is not con-
sidered to be a problem for the general population. However, benzene has
been detected 1n various food categories: fruits, nuts, vegetables, dairy
products, meat, fish, poultry, eggs, and several beverages; an indication of
this has been tabulated by the National Cancer Institute (1977) as presented
in Table 2. MCI estimated that an Individual could ingest as much as 250
ug/day from these foods. The presence of benzene in several other foods has
been confirmed by a number of researchers using gas chromatography coupled
with mass spectroscopy (Table 3).
The distribution of benzene in the aquatic system is not well docu-
mented. Neely, et al. (1974) demonstrated a relationship between octanol/
water partition coefficients and bioaccumulation potential in fish. To pro-
tect human health, water quality criteria should apply to saltwater as well
as freshwater because the major portion of the aquatic life consumed in the
United States 1s obtained from saltwater.
A bioconcentration factor (BCF) relates the concentration of a chemical
in aquatic animals to the concentration 1n the water in which they live.
The steady-state BCFs for a lipid-soluble compound in the tissues of various
C-4
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TABLE 2
Estimated Benzene Levels In Food*
Benzene Level in Food
Food
Heat treated or canned beef 2
Jamaican rum 120
Irradiated beef 19
Eggs 500-1900
*Source: NCI, 1977
c-5
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TABLE 3
Foods Containing Benzene
FOOD
REFERENCES
Haddock fillet
Red beans
Blue cheese
Cheddar cheese
Cayenne pineapple
Roasted filberts
Potato tubers
Cooked chicken
Hothouse tomatoes
Strawberries
Black currants
Roasted peanuts
Soybean milk
Codfish
Angelini, et al. 1975
Buttery, et al. 1975
Day and Anderson, 1965
Day and Libbey, 1964
Flath and Forrey, 1970
Kinlin, et al. 1972
Meigh, et al. 1972
Nonaka, et al. 1967
Schormuller and Kockmann, 1969
Teranishi, et al. 1963
von Sydow and Karlsson, 1971
Waldradt, et al. 1971
Wilkins and Lin, 1970
Wong, et al. 1967
C-6
-------
aquatic animals seem to be proportional to the percent lipid in the tis-
sue. Thus the per capita ingestion of a lipid-soluble chemical can be esti-
mated from the per capita consumption of fish and shellfish, the weighted
average percent lipids of consumed fish and shellfish, and a steady-state
BCF for the chemical.
Data from a recent survey on fish and shellfish consumption in the
United States were analyzed by SRI International (U.S. EPA, 1980). These
data were used to estimate that the per capita consumption of freshwater and
estuarine fish and shellfish in the United States is 6.5 g/day (Stephan,
1980). In addition, these data were used with data on the fat content of
the edible portion of the same species to estimate that the weighted average
percent lipids for consumed freshwater and estuarine fish and shellfish is
3.0 percent.
No measured steady-state bioconcentration factor (BCF) is available for
benzene, but the equation "Log BCF » (0.85 Log P) - 0.70" can be used
(Veith, et al. 1979) to estimate the BCF for aquatic organisms that contain
about 7.6 percent lipids (Veith, 1980) from the octanol/water partition co-
efficient (P). Based on an average measured log P value of 2.14 (Hansch and
Leo, 1979; Dec, et al., Manuscript), the steady-state bioconcentration fac-
tor for benzene is estimated to be 13.2. An adjustment factor of 3.0/7.6 =
0.395 can be used to adjust the estimated BCF from the 7.6 percent lipids on
which the equation is based to the 3.0 percent lipids that is the weighted
average for consumed fish and shellfish. Thus, the weighted average biocon-
centration factor for benzene and the edible portion of all freshwater and
estuarine aquatic organisms consumed by Americans is calculated to be 13.2 x
0.395 - 5.21.
C-7
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Inhalation
The respiratory route is the major source of human exposure to benzene,
and much of this exposure is by way of gasoline vapors and automotive emis-
sions. American gasolines contain an average of 0.8 percent (by weight)
benzene, and European gasolines contain an average of 5 percent (Goldstein,
1977a). Benzene comprises approximately 2.15 percent (by weight) of the
total hydrocarbon emissions from a gasoline engine; this is approximately
equivalent to 4 percent benzene (by weight) in automotive exhaust (Howard
and Ourkin, 1974). This can be extrapolated to an annual benzene emission
from automotive exhaust of 940 million pounds in 1971, which is well over
one-half of the benzene released to the environment. The geographical dis-
tribution of this emission probably approximates population density distrib-
ution. Release of benzene into the environment from industrial and commer-
cial use probably does not exceed 30 percent of the total. Other sources
are relatively insignificant (Howard and Ourkin, 1974).
Concentrations of benzene in the air around gas stations have been
found to be 0.3 to 2.4 ppm [National Academy of Sciences (NAS), 1977].
Lonneman, et al. (1968) measured an average concentration of 0.015 ppm in
Los Angeles air, with a maximum of 0.057 ppm. The rural background level
for benzene has been reported as 0.017 ppb (Cleland and Kingsbury, 1977).
Recently, Young, et al. (1978) have brought attention to the fact that con-
sumers may be exposed unknowingly to benzene in the home in the form of
paint strippers, carburetor cleaners, denatured alcohol, rubber cement, and
art and craft supplies.
Dermal
Since liquid benzene is poorly absorbed through the intact skin [Na-
tional Institute for Occupational Safety and Health (NIOSH), 1974] and skin
contact is infrequent, the dermal route is only a minor source of human ex-
posure.
C-8
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PHARMACOKINETICS
Absorption
The most frequent route of human exposure to benzene is via inhala-
tion. Toxic effects in humans nave often been attributed to combined inha-
lation and dermal exposure. For example, rotogravure workers were described
as washing ink from their hands in open vats of benzene (Hunter, 1962). Al-
though Lazarew, et al. (1931) claimed that benzene could be absorbed by rab-
bits through the skin, neither Cesaro (1946), nor Conca and Maltagliati
(1955) could demonstrate significant percutaneous absorption in humans.
Nevertheless, small amounts of benzene absorbed by this route may not have
been detected.
Distribution
Benzene accumulated primarily in fatty tissues in the dog (Schrenk, et
al. 1941), the mouse (Andrews, et al. 1977) and the rat (Rickert, 1979).
Co-administration of toluene with benzene does not alter the accumulation of
benzene in the various organs of the mouse (Andrews, et al. 1977). The fat
and marrow contained the greatest concentrations of benzene; blood, liver,
and kidney also contained significant amounts of benzene; less benzene was
observed in the spleen, lung, and brain.
Benzene metabolites were highest in bone marrow and liver. It is note-
worthy that in both mice given ^H-benzene by subcutaneous injection (An-
drews, et al. 1977), and rats given benzene by inhalation, the concentra-
tions of benzene metabolites in the bone marrow exceeded those in blood.
These data taken with the reports of Andrews, et al. (1979) and Irons, et
al. (1980) describing the metabolism of benzene in bone marrow preparations,
have presented a strong argument to implicate the marrow as the site at
C-9
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which the toxic metabolite(s) of benzene is (are) formed. It is more like-
ly, however, that metabolites coming from the liver are trapped in the mar-
row because it has been demonstrated that partial hepatectomy prevents ben-
zene-induced bone marrow depression and reduces the accumulation of benzene
metabolites in marrow.
In the course of a series of studies on benzene metabolism i_n_ vivo it
was observed (Snyder, et al. 1978) that metabolites of benzene remained
covalently bound to residual protein of liver, brain, kidney, spleen, and
fat in mice. Further studies showed that the degree of binding was dose de-
pendent and increased in both liver and bone marrow upon repeated exposure.
Tunek, et al. (1978) reported that the covalently bound species in liver
microsomes was not likely to be benzene oxide but a metabolite of phenol.
Tunek, et al. (1979) have gone on to investigate specific microsomal pro-
teins to which benzene covalently binds. Lutz and Schlatter (1977) reported
on the covalent binding of benzene to ONA in liver nuclei. These authors
feel that covalent binding to DNA in liver offers a model for the study of
the mechanism of benzene toxicity and/or carcinogenesis in bone marrow.
This hypothesis may be supported by the report that in the partially hepa-
tectomized rat there was a decrease of not only soluble metabolites in the
bone marrow but also of covalent binding (Sammett, 1979).
Metabolism
It has been known since the latter part of the nineteenth century that
benzene is biologically converted to phenol (Schultzen and Naunyn, 1867) as
well as to catechol and hydroquinone (Nencki and Giocosa, 1880). The first
detailed studies of the metabolites of benzene formed l£ vivo were reported
by Porteous and Williams (1949a,b), and with the advent of 14C-benzene
these studies were improved upon by Parke and Williams (1953). Extensions
C-10
-------
of this work in recent years have largely concentrated on metabolism in var-
ious animal species, on the mechanism of benzene metabolism using jji vitro
techniques and on attempting to relate benzene metabolism to its toxicity
(Snyder and Kocsis, 1975; Snyder, et al. 1977).
In a landmark series of papers (Porteous and Williams, 1949a,b; Parke
and Williams, 1953), outlined the broader aspects of benzene metabolism in
rabbits by identifying most of the metabolites in urine as well as those in
expired air. He later demonstrated that about one percent could be recover-
ed in bile (Abou-el-Marakem, et al. 1967). The major hydroxylation product
was phenol which, along with some catechol and hydroauinone, is found for
the most part in urine conjugated with ethereal sulfate or glucuronic acid.
Unconjugated phenol has been found in mouse (Andrews, et al. 1977) and rat
(Cornish and Ryan, 1965) urine after benzene administration. Parke and Wil-
liams (1953) also reported on the occurrence of phenylmercapturic acid and
muconic acid. The latter, along with labeled carbon dioxide found in the
expired air, suggested that some opening of the ring occurred. Andrews, et
al. (1977) estimated that a 25 g mouse could metabolize, at most, approxi-
mately 1 mmole of benzene per day.
Benzene metabolism has been studied in liver homogenates (Snyder, et
al. 1967; Hirokawa and Nomiyama, 1962; Sakamoto, et al. 1957), cell super-
natant fractions containing microsomes (Snyder, et al. 1967; Kocsis, et al.
1968; Sakamoto, et al. 1957; Sato and Nakajima, 1979a,b) and microsomes
(Posner, et al. 1961; Snyder, et al. 1967; Gonasun, et al. 1973; Drew, et
al. 1974; Harper, et al. 1973; Tunek, et al. 1978). It is clear from these
studies that benzene is metabolized in liver microsomes of rat, rabbit, and
mouse. Gonasun, et al. (1973) demonstrated that the first step is mediated
by the mixed function oxidases. Jerina and co-workers (Jerina, et al. 1968;
C-ll
-------
Jerina and Daly, 1974) have outlined a pathway for benzene metabolism which
revolves about the formation of benzene oxide, an epoxide of benzene, as the
first product. This highly unstable intermediate rearranges non-enzymati-
cally to form phenol. This step accounts for the occurrence of phenol as
the major metabolite of benzene found in urine. Catechol formation is
thought to result from the hydration of benzene oxide by the enzyme epoxide
hydratase followed by oxidation to catechol. The intermediate dihydrodiol
was observed in rat urine by Sato, et al. (1963). The evidence for the
epoxide intermediate is that addition of the epoxide to liver preparations
yields the same metabolites as benzene (Jerina, et al. 1968) and the addi-
tion of excess hydratase enzyme increases the formation of catechol (Tunek,
et al. 1978). Thus, it appears that phenol and catechol are formed by two
distinctly different metabolic pathways.
The other dihydroxylated derivative, hydroquinone, is thought to result
from a second passage of phenoT through the mixed function oxidases. The
premercapturic acid, i.e., the glutathione conjugate, is formed by the addi-
tion of glutathione to the epoxide via the glutathione transferase enzyme
(Jerina, et al. 1968).
The metabolism of benzene j£ vitro can be altered by the use of enzyme
inducing agents administered to the animals prior to sacrifice or by the ad-
dition of inhibitors to the incubation mixtures. Benzene (Snyder, et al.
1967), phenobarbital (Snyder, et al. 1967; Drew, et al. 1974), 3-methylchol-
anthrene (Drew, et al. 1974), and dimethyl sulfoxide (Kocsis, et al. 1968),
are all microsomal stimulants for the metabolism of benzene. On the other
hand, benzene metabolism can be inhibited by carbon monoxide, aniline,
metyrapone, SKF 525A, aminopyrine, cytochrome c (Gonasun, et al. 1973),
aminotriazole (Hirokawa and Nomiyama, 1962), and toluene (Andrews, et al.
C-12
-------
1977). Gut (1978) has argued that alterations of benzene metabolism i£
vitro by enzyme induction may not be reflective of the overall rate of ben-
zene metabolism in whole animals because the in vitro systems do not ac-
curately mimic the pharmacokinetics observed in vivo.
The strongest evidence supporting the concept that benzene must be
metabolized to produce bone marrow depression is based on the facts that
benzene toxicity is prevented by coadministration of toluene, which inhibits
benzene metabolism (Andrews, et al. 1977), and that partial hepatectomy pro-
tects animals against benzene toxicity while decreasing benzene metabolism
(Sammett, 1979). These studies also suggest that despite the fact that ben-
zene is metabolized to some extent in bone marrow (Andrews, et al. 1979;
Irons, et al. 1980), the liver must be intact for benzene toxicity to oc-
cur. Previous reports of protection against toxicity in phenobarbital
treated animals (Ikeda and Ohtsujl, 1971; Drew, et al. 1974) reflect the
fact that phenobarbital probably increased the detoxification rate in
liver. On the other hand, Inhibition of metabolism by toluene and also by
amlnotriazole (Hirokawa and Momiyama, 1962) protected animals by decreasing
the rate of formation of toxic metabolites. Thus, it appears that a metabo-
lite formed in liver is transported into the marrow where it is converted to
a compound which cannot be removed from the marrow and accordingly accumu-
lates (Andrews, et al. 1977; Riexert, et al. 1979) leading to a metabolic
impairment expressed as bone marrow depression. Similar mechanisms may play
a role in benzene-induced leukemogenesis.
determination of benzene metabolism In humans was first evaluated as a
measure of exposure, rant, et al. (1935) suggested that since benzene meta-
bolites in the urine could be detected as ethereal sulfates it would be pos=
sible to estimate benzene exposure by measuring the ratio of urinary inor-
ganic to organic sulfate. Normally the inorganic sulfate is present at
C-13
-------
about four times the organic levels. Exposure to benzene tends to increase
the organic sulfate and lower the inorganic. Data from studies by Hammond
and Herman (1960) suggest that of total sulfates, urinary inorganic sulfate
levels of 80-95 percent were normal, 70-80 percent indicated some exposure
to benzene, 60-70 percent suggested a dangerous level of benzene exposure,
and 0-60 percent indicated that there had been benzene exposure sufficiently
high to create an extremely hazardous situation.
In humans the sulfate is the major conjugate of phenol until levels of
approximately 400 mg/1 are reached (Sherwood, 1972). Beyond that level
glucuronides are found. Teisinger, et al. (1952) exposed humans to benzene
at 100 ppm for 5 hours and found that their urine contained primarily phenol
with small amounts of catechol and hydroquinone. It would appear from the
available evidence, that benzene metabolism in humans is similar to that in
animals.
The metabolism of benzene has been reviewed recently by Rusch, et al.
(1977).
Excretion
Following exposure to benzene, humans, like animals, eliminate un-
changed benzene in the expired air (Sherwood and Carter, 1970; Hunter, 1968;
Nomiyama and Nomiyama, 1974a,b; Sato, 1972; Srbova, et al. 1950). The elim-
ination of unchanged benzene was quantified in a series of studies by Nomi-
yama and Nomiyama (1974a,b) who exposed men and women to benzene at levels
of 52-62 ppm for four hours and determined its respiratory disposition. A
mean value of 46.9 percent of the benzene was taken up in these subjects,
30.2 percent was retained and the remaining 16.8 percent was excreted as un-
changed benzene in the expired air. Pharmacokinetic plots of respiratory
elimination were interpreted to indicate that there were three phases to the
C-14
-------
excretion that could be described by three rate constants. There were no
significant differences between men and women in these studies. Hunter
(1968) exposed humans to benzene at 100 ppm and detected benzene in expired
air 24 hours later and suggested that it was possible to back-extrapolate to
the concentration of benzene in the inspired air.
Benzene toxicity in humans is usually caused by inhalation of ambient
air containing benzene vapor. Following cessation of exposure the body bur-
den of benzene is reduced either by exhaling benzene in the expired air or
by metabolism. The exhalation of unchanged benzene has been studied in dogs
(Schrenk, et al. 1941), rabbits (Parke and Williams, 1953), mice (Andrews,
et al. 1977) and rats (Rickert, et al. 1979). Schrenk, et al. (1941) ex-
posed dogs to 800 ppm benzene by inhalation and determined that the time
necessary to rid the body of benzene was related to the duration of exposure
because of the tendency of benzene to accumulate in body fat. Parke and
Williams (1953) administered C-benzene orally and recovered approximate-
ly 43 percent of the administered dose as unmetabolized benzene in trapped
exhaled air. Andrews, et al. (1977) administered benzene to mice subcutan-
eously and recovered 72 percent of the dose in the air. Simultaneous treat-
ment with both benzene and toluene (Andrews, et al. 1977; Sato and Nakajima,
1979b) or benzene and piperonyl butoxide (Timbrel 1 and Mitchell, 1977) in-
creases the excretion of unchanged benzene in the breath. These compounds
appear to act by inhibition of benzene metabolism which thereby leaves more
benzene available for excretion through the lungs.
Rickert, et al. (1979) reported that the excretion of unchanged benzene
from the lungs of rats followed a biphasic pattern suggesting a two-compart-
ment model for distribution and a t^2 of 0.7 hr. This agreed with exper-
imental t . values for various tissues which ranged from 0.4 to 1.6 hr.
C-15
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EFFECTS
Acute, Subacute and Chronic Toxicity
In man, acute benzene poisoning is characterized by nausea, vomiting,
ataxia, and excitement, followed by depression and coma. Death is usually
the result of respiratory or cardiac failure (Holvey, 1972). Benzene expo-
sure causes acute toxic effects on the central nervous system. These have
been reviewed by Gerarde (1960) and Browning (1965). Single exposures to
benzene in the air at a concentration of 20,000 ppm have proved to be fatal
within S to 10 minutes. Effects included headache, nausea, staggering gait,
paralysis, convulsions, and eventual unconsciousness and death, usually fol-
lowing cardiovascular collapse. Giddiness and euphoria have also been re-
ported. Severe nonfatal cases have exhibited similar symptoms, but recov-
ered after a period of unconsciousness. Autopsy findings have indicated
respiratory tract inflammation, lung hemorrhages, kidney congestion, and
cerebral edema (Winek and Collom, 1971).
It has also been suggested that accidentally ingested benzene may have
resulted in ulceration of the gastrointestinal mucosa (Appuhn and Goldeck,
1957; Caprotti, et al. 1962).
The chronic effects of benzene have recently been thoroughly reviewed
by the National Academy of Sciences (1976) and the U.S. EPA (1977). These
reports have served as the main source of data for this section and the sec-
tions on mutagenicity and carcinogenicity.
Benzene is a proven hematotoxin. In man it is causally related to pan-
cytopenia and to acute myeloblastic leukemia. Pancytopenia refers to a de-
crease in all of the major circulating formed elements in the blood: erythr-
ocytes (red blood cells), leukocytes (white blood cells), and thrombocytes
(platelets). In mild cases of benzene hematotoxicity a decrease in only one
C-16
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of the circulating formed elements may be observed; e.g., anemia, leukopen-
ia, thrombocytopenia. The term aplastic anemia denotes a relatively severe
pancytopenia, usually associated with a marked diminution in bone marrow
cellularity.
Acute myeloblastic leukemia, also referred to as acute myelogenous leu-
kemia, is the type of acute leukemia most commonly observed in adults. In
addition to pancytopenia and acute myeloblastic leukemia, which can be
clearly causally related to benzene exposure in man, there are a number of
other hematological disorders for which the observed association with ben-
zene exposure is not of sufficient strength to prove causality. These dis-
orders include chronic myelogenous leukemia and various lymphoproliferative
disorders.
The following discussion will review the evidence linking benzene expo-
sure with hematotoxicity in man. The focus will be on those few studies for
which dose-response data are available. Other aspects to be covered include
discussion of the potential mechanism of toxicity and review of the litera-
ture concerning possible variability in individual susceptibility to ben-
zene. More extensive discussion of benzene hematotoxicity in man is pre-
sented in a number of recent reviews (U.S. EPA, 1978a,b; Goldstein and Las-
kin, 1977; Goldstein, 1977b; NAS, 1975, 1976; NIOSH, 1974; Snyder and Koc-
sis, 1975).
Evidence of a pancytopem'c effect of benzene was first noted in 1897 by
Santesson, who reported four cases of fatal aplastic anemia occurring in
workers fabricating bicycle tires. Since then numerous case reports and
surveys of occupationally exposed groups of workers have documented this as-
sociation, and many reviews of these cases have appeared (International
Labour Office, 1968; Bowditch and Elkins, 1939; Browning, 1965; Goldstein,
C-17
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1977b; Hamilton, 1931; NAS, 1975, 1976; Hunter, 1944; NIOSH, 1974; Selling
and Osgood, 1935; Snyder, et al. 1978; Snyder and Kocsis, 1975). The causal
relationship of benzene to pancytopenia in man is most clearly supported by
studies of groups of workers in whom the appearance of pancytopenia was tem-
porally related to the inception of benzene use and in which the outbreak of
hematological effects was ended by replacement of benzene with another sol-
vent.
Systematic studies of the pancytopenic effects of occupational exposure
to benzene were performed by Greenburg, et al. (1939), Goldwater (1941), and
Goldwater and Tewksbury (1941). These investigators evaluated workers in
the printing industry who had been exposed to benzene for 3 to 5 years after
the introduction of a new industrial process. Air sampling revealed benzene
concentrations ranging from 11 ppm to 1,060 ppm (median 132 ppm). The most
freauent hematological abnormalities found in the 332 exposed individuals,
as compared to 81 nonexposed controls, were anemia, macrocytosis, and throm-
bocytopenia. Of note is that an absolute lymphocytopenia was more common
than was neutropenia. Hematological abnormalities were observed in 65 work-
ers, 23 of whom were considered to be severely affected, six seriously
enough to require hospitalization. Recovery from hematological disorders
was demonstrated following replacement of benzene with other solvents (Gold-
water and Tewksbury, 1941).
Other relatively large scale early studies of occupationally-exposed
individuals include Wilson's (1942) study of 1,104 workers in an American
rubber factory during World War II. Mild hematotoxicity was noted in 83
workers. Severe pancytopenia was seen in 25 workers; of these, nine were
hospitalized and three died. Ambient benzene levels in the factory were re-
ported to have averaged at about 100 ppm with peaks of 500 ppm. Helmer
C-18
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(1977) reported evidence of hematological abnormalities in 60 of 184 workers
in a rubber raincoat factory. Levels of benzene in factory air were report-
ed to range from 137 to 218 ppm and were speculated to have been higher in
the period before the sampling was done. Re-evaluation of the workers 16
months after cessation of benzene use revealed that 46 had recovered, but
twelve still had significant effects, and two had died.
Pagnotto, et al. (1961) reported atmospheric benzene levels of up to
125 ppm, but with the majority of levels lower than 25 ppm, in a study of a
rubber coating facility. In one plant of this facility evidence of benzene
hematoxicity was present in five of 32 workers while in two other plants
none of the six and one of nine workers, respectively, were affected. How-
ever, the latter individual had hematological effects serious enough to re-
auire hospitalization. This is somewhat reminiscent of an earlier study by
Hutchings, et al. (1947) who studied an Australian Air Force workshop after
discovery of a fatal case of aplastic anemia. Hutchings, et al. (1947) mea-
sured peak benzene concentrations well above 100 ppm in most areas of the
workshop with occasional levels as high as 1,400 ppm; average benzene levels
were in the range of 10 to 35 ppm. Comparison of 87 benzene-exposed in-
dividuals with 500 workers exposed to other hydrocarbons and 300 unexposed
controls demonstrated that they shared only a slight tendency toward cyto-
penic effects. These observations of Pagnotto, et al. (1961) and Hutchings,
et al. (1947) suggest the possibility of individual susceptibility to the
pancytopenic effects of benzene.
Detailed descriptions of many cases of benzene-induced pancytopenia in
industrially-exposed individuals have been reported from Italy, particularly
by Vigliani, Saita, Forni, and their colleagues (Form' and Moreo, 1967,
1969; Forni and Vigliani, 1974; Forni, et al. 1971a,b; Saita, 1945; Saita
C-19
-------
and Oompe, 1947; Salta and Moreo, 1959, 1961, 1966; Salta and Sbertoli,
1962; Saita and V1gl1an1, 1962; Salta, ct al. 1964; V1gl1an1, 1975; Vigllani
and Forni, 1966, 1969, 1976; V1g11an1 and Salta, 1943, 1964). These studies
reported benzene concentrations ranging from 20 ppm to 150 ppm, with many
levels over 200 ppm in several factories.
In a series of papers, Aksoy and his colleagues collected a large
amount of data relating occurrence of aplastlc anemia to the use of benzene-
containing adhesives 1n the shoemaking Industry. This Incidence was shown
to have dramatically declined following replacement of the adhesive with a
benzene-free substance. Benzene levels 1n air to which the workers were ex-
posed were In the range of 150 to 650 ppm (Aksoy, 1977; Aksoy and Erdero,
1969, 1978; Aksoy, et al. 1966, 1971, 1972a,b, 1974a,b,c, 1975a,b, 1976a,b;
Erdogan and Aksoy, 1973).
Effects 1n occupationally-exposed groups at relatively low benzene
levels have been reported by Eastern European researchers. Ooskin (1971)
reported findings 1n 365 workers employed 1n a new chemical factory which
could be interpreted as Indicating that exposure from 10 ppm to 40 ppm ben-
zene for less than one year produces mild hematological effects. Mild
thrombocytopenla was the most common abnormality and mild anemia was also
seen. These were observed 1n about 40 percent of the workers, usually in
the first year of exposure. Ooskin (1971) also reported lymphocytosis, a
biphasic leukocyte response, and bone marrow hypercellularlty in the exposed
individuals. These effects have not been reported by other researchers.
The actual benzene levels and monitoring procedures used in this study were
not clearly defined. Smolik, et al. (1973) reported a decrease in mean ser-
um complement level in 34 benzene-exposed workers when compared to a control
group. Benzene levels to which the workers were exposed ranged from 3.4 ppm
C-20
-------
to 6.8 ppm and the duration of exposure was from 3 months to 18 years. A
related study reported findings of decreased serum immunoglobulin levels and
Increased levels of leukocyte agglutlnins in workers exposed to benzene and
alkyl benzenes (Lange, et al. 1973a,b). Altered immune function as a result
of benzene exposure has been reported in animals and in man (Revnova, 1962;
Roth, 1972) and is conceivably related to the known effects of benzene on
lymphocytes. A mechanism for the decrease in complement levels reported in
association with benzene exposure by Smolik, et al. (1973) has not been
elucidated. Khan and Muzyka (1970, 1973) noted an increase in red cell del-
taaminolevulinic acid in 16 of 27 workers exposed to benzene. Four of the
16 affected individuals were reported to have been exposed to only 1.6 ppm
benzene. The other 12 had reported earlier exposures from 6.4 to 15.6 ppm
and more recent exposures to 1.6 ppm benzene. Studies performed utilizing
rabbit reticulocytes provided some support for the authors' hypothesis that
benzene may alter porphyrin metabolism (Wildman, et al. 1976). This finding
has not been confirmed in man. Chang (1972) reported hematological abnor-
malities, particularly anemia and leukopenia, in 28 of 119 workers exposed
to benzene in Korea. The author performed a detailed extrapolation of his
findings resulting in derivation of an exponential function describing the
benzene concentration and duration of exposure required for hematotoxicity:
y - (82.5) (0.77°-2x) * 10.1
where y equals benzene concentration in ppm and x is work duration in
months. No hematological toxicity was observed in 18 subjects exposed to 10
to 20 ppm benzene. The work population and exposures were incompletely
characterized, leading to difficulty in interpreting the general relevance
of these findings. Hematologic effects in workers exposed to similar levels
C-21
-------
of benzene have been noted by Girard, et al. (1970a,b). Girard and col-
leagues (Girard, et al. 1966, 1967, 1968, 1970a,b,c, 1971a,b; Girard and
Revol, 1970), in a series of studies of human benzene hematotoxicity, noted
frequent decreases in leukocyte alkaline phosphatase activity among 319
workers exposed to 10-25 ppm benzene. The clinical significance of these
findings is unclear.
Interpretation of these studies has been difficult, particularly with
regard to dose-response relationships. A major problem has been the almost
universal presence of other solvents along with benzene in the occupational
environment. It has been widely suggested that benzene may not be unique
among common solvents in its ability to produce hematotoxicity. Reports in
the older literature, however, which reported hematopoietic effects of tol-
uene and xylene, almost certainly reflect solvent contamination with ben-
zene. The other aromatic solvents, although not directly hematotoxic, are
suspected to interact with benzene, perhaps by altering its metabolism and
thereby affecting its toxicity.
Another major problem with the interpretation of existing studies in-
volves the estimation of the dose to the individual, which may vary due to
differences in work habits. This is a particular problem when considering
low incidence phenomena such as benzene leukemogenesis. A further problem
in defining low level benzene effects is the wide range in the normal levels
of blood formed elements (e.g., normal white blood cell count 5,000 -
10,000/mnr; red blood cell count, 4.4 - 5.6 x 106/mm3; platelet count
150,000 - 350,000/mm3). Furthermore, the bone marrow has a considerable
reserve capacity. Accordingly, the earliest hematopoietic effects of ben-
zene may not be apparent when routine blood counts are obtained in an ex-
posed population. Slight changes in hematological measurements which may be
C-22
-------
detected upon routine examinations of exposed individuals also may, in fact,
be normal fluctuations. It is unknown whether minor shifts in hematological
parameters should be considered as clinically insignificant or, on the other
hand, could conceivably be the basis for neoplastic transformation or other
hematotoxic manifestations.
The manifestations of benzene hematotoxicity range from clinically in-
apparent cytopenia to lethal aplastic anemia. Symptoms in milder cases ap-
pear to reflect anemia and .include relatively nonspecific complaints such as
lassitude, easy fatigability, dizziness, headache, palpitation, and short-
ness of breath. The direct life-threatening consequences of severe pancyto-
penia are from leukopenia, which results in decreased ability to fight in-
fection, and from thrombocytopenia, which may precipitate significant bleed-
ing. There is evidence suggesting that such effects are due not only to the
absolute decrease in number, but also to qualitative abnormalities of circu-
lating formed elements. Various alterations in morphology and function of
granulocytes, lymphocytes, platelets, and red cells have been reported in
humans exposed to benzene (U.S. EPA, 1978b). Some of these effects occur as
relatively early manifestations of hematotoxicity and may be suitable for
use as screening tests in populations with a history of exposure to ben-
zene. Certain manifestations, e.g., macrocytosis, appear to be more fre-
quent in benzene-induced pancytopenia than in cases of aplastic anemia of
unknown etiology although there are no absolute data which prove or refute
this hypothesis.
In terms of prognosis, review of the case material in the literature
concerning benzene hematotoxicity suggests that the eventual outcome is sim-
ilar to that reported for idiopathic aplastic anemia (Goldstein, 1977c).
Mild cases tend to do well, with gradual recovery generally observed. On
C-23
-------
the other hand, severe aplastic anemia has a very high mortality rate even
with modern therapeutic approaches. Moderate to severe cases may result in
persistent pancytopenia. A particularly dreaded complication is the de-
velopment of acute myeloblastic leukemia. This has occurred many years
after cessation of benzene exposure (DeGowin, 1963; Erdogon and Aksoy, 1973;
Guasch, et al. 1959; Justin-Besancon, et al. 1959; Saita and Vigliani, 1962;
Sellyei and Kelemen, 1971).
There are three lines of evidence which support a causal relation be-
tween benzene exposure and acute myeloblastic leukemia in man. These in-
clude the basic biomedical data which produce a plausible conceptual frame-
work for benzene leukemogenesis; the many case reports, including those in
which individuals with almost certain benzene-induced pancytopenia have de-
veloped acute myeloblastic leukemia; and the epidemiological evidence ob-
tained by different approaches, in different occupational settings, and in
different countries, associating benzene with acute myeloblastic leukemia.
The correlation of benzene exposure with leukemogenesis has been com-
pared with the well-known association of acute myeloblastic leukemia follow-
ing idiopathic aplastic anemia resulting from other hematotoxins such as
chloromycetin (chloramphenicol) or phenylbutazone. There is little differ-
ence in the clinical course of aplastic anemia following benzene exposure
and exposure to other hematologically-active substances. The fact that ben-
zene-induced pancytopenia is associated with chromosomal abnormalities in
man is also in keeping with a causal relationship to neoplasia, although it
does not constitute absolute proof thereof. Historically, benzene-induced
leukemogenesis has not been demonstrated in laboratory animals. However,
recent studies suggest low incidence of acute and chronic myelogenous leu-
kemia in benzene-exposed animals of two rodent strains in which these
C-24
-------
diseases are not known to occur spontaneously (Goldstein, et al. 1980).
Maltoni and Scarnato (1979) have previously demonstrated an enhancement of
leukemia incidence in Sprague-Dawley rats when treated with benzene by
ingestion in olive oil at concentrations of 250 and 50 mg/kg body weight
once daily, 4-5 days weekly, for 52 weeks. In addition, these investigators
observed high incidence of various types of malignancies, namely Zymbal's
gland carcinomas, skin carcinomas, mammary carcinomas, angiosarcomas, hepa-
tomas and tumors of other organs (Tables 4 and 5).
The world literature contains well over 100 case reports of acute mye-
loblastic leukemia in benzene-exposed individuals. There are reasonable
grounds to expect that many cases may go unreported, as the association may
be obscured by the often long delay between benzene exposure and manifesta-
tion of acute leukemia, or by ignorance of such exposure on the part of
patient or physician. However, these case reports taken together do provide
evidence of benzene casuality in three ways. The first is the worldwide
distribution of the observations which have been reported in many different
occupational settings and which have a single common denominator, benzene
exposure. More impressive is the relative frequency in which individuals
demonstrated to have benzene-induced pancytopenia have been followed clinic-
ally through a transitional preleukemic phase and then into acute myelo-
blastic leukemia. In these cases the relationship between the resulting
leukemia and the initial benzene exposure can generally be clearly demon-
strated. Also of note is the relative frequency of erythroleukemia, also
known as Di Guglielmo's syndrome, among the case reports. This is a rela-
tively uncommon variant of acute myeloblastic leukemia characterized by
large numbers of circulating neoplastic red blood cell precursors. The
apparent greater frequency of erythroleukemia in benzene-exposed individuals
suggests a relatively specific effect of benzene on erythroid precursors
which may differ from its effect on myeloid cells.
C-25
-------
TABLE 4
Distribution of the Different Types of Tumors*
ttam*
a*.
l
it
in
t.,-
tittion
•f/U
£*«
Win
(It
(CMtr*l I
II MM
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y
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.
*.
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it.l
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.
-
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t
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%
(M
-
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.
-
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(•)
-
74.0
71.0
-
.
-
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i Ul
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-
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t
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it
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17
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,
1
(ii) Alive miauls «/icr 20 weeds, wi>en the liru tumour (• mammary fibroadenonu) w»« objervcd.
(b) Tl>c percenianet are referred to the corrected number.
(c) Average lime front the ilafl of ihe experiiiKni 10 (lie dctcclkm (if the pcriodk control or at autopsy).
(J) Average age at the onset of the Aril mammary tuniour per animal delected at the pcriodk control or
(c) I with MrcomaiOtis component.
JO Subcutaneous anfioiarcoma,
autopsy.
*Source: Maltoni and Scarnato, 1979.
^Exposure by ingestion (stomach tube) to benzene in olive oil at 250 and 50 mg/kg body weight, once daily,
4-5 days weekly, for 52 weeks. Results after 144 weeks (end of experiment).
C-26
-------
GRW5—5FT
NO.
TABLE S
Distribution of the Different Types of Miscellaneous Tumors*3
ANIMALS BEARING OTHER TUMOURS
MaTlgnanT
Benign
II
III
M
Total
No. Distribution of histotypes
No. Distribution of histotypes
4 dermatof ibromas
2 subcutaneous lipomas
M 10 2 mammary f ibromas
1 pheochromocytoma
I 1 lymph node fibroangioma
9 mammary flbroadenomas
1 kidneys adenoma 1
F 13 1 pheochromocytoma
1 polypoid adenoma of the colon
1 polypus of the uterus
1 intrabdominal adenocarcinoma
1 oligodendroglioma
2
1 adenocarcinoma of the uterus
1 fibrosarcoma of the uters
3 1 meningioma
12
16
b mammary TiDromas
M 8 1 mammary fibroadenoma
2 Leydig cells tumours
1 meningioma
21 mammary fibroadenomas
1 pheochromocytoma
F 25 1 polypus of the uterus
1 papilloma of the uterus
1 peritoneal lipoma
1 carcinoma of the ureter
1 adenocarcinoma of the uterus
27
I aermatotibromas
1 pheochromocytoma
1 bladder papilloma
1 retroperitoneal lipoma
i ongodendrog iioma
16 mammary fibroadenomas
1 adrenal gland cortical adenoma
1 pheochromocytoma
22 1 ileo-caecum fibroma
1 polypus of the uterus
1 bladder papilloma
1 neurilemoma
2 adenocarcinomas of the uterus
24
*Source: Maltoni and Scarnato, 1979.
aExposure hy ingestion (stomach tube) to benzene in olive oil at 250 and 50 mg/kg body weight,
once daily, 4-5 days weekly, for 52 weeks. Results after 144 weeks (end of experiment).
C-27
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The epidemic*logic evidence supporting the relationship of benzene expo-
sure to leukemia has been obtained using a number of different approaches.
In some studies the starting point has been the observation by hematologists
or by occupational physicians of individuals with leukemia. A case control
approach in which occupational histories are obtained from individuals with
various hematological disorders, as well as from normal subjects, has been
used by French investigators who noted a significant association of past
benzene exposure in patients with acute myeloblastic leukemia (Girard and
Revol, 1970; Girard, et al. 1968). A recent study by Mitelman, et al.
(1979) suggested that it may be possible to define a subgroup of leukemics
with benzene-induced myeloblastic leukemia. Mitelman, et al. (1979) found
chromosomal abnormalities in leukemic bone marrow cells in each of 13 in-
dividuals with an occupational history of solvent exposure, in each of three
individuals who had been exposed to insecticides, and in three of seven ex-
posed to petroleum products. In comparison, only eight of 33 leukemics with
no history of such occupational exposure had chromosomal abnormalities.
These findings suggest a specific mode of action in benzene leukemogenesis.
Another epidemiologic approach has been taken by Italian and Turkish invest-
igators who have evaluated large numbers of individuals with benzene asso-
ciated hematotoxicity. Starting with well-defined cases, the investigators
have estimated the total population exposed to benzene and then calculated
the excess risk based upon the incidence of leukemia in the general popula-
tion. Vigliani and Saita (1964) estimated a 20-fold increase in risk for
acute leukemia in benzene-exposed workers in Pavia and Milan. Aksoy, et al.
(1974b) reported a greater than 2-fold increase in risk for shoe workers in
Istanbul, but, as discussed elsewhere (U.S. EPA, 1978b) this is probably an
underestimate.
C-28
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The episode in Turkey is particularly, illustrative of the hematotoxic
hazard of benzene. Beginning about 1960, shoemakers in Istanbul started us-
ing adhesives prepared with benzene (9 to 88 percent) which were cheaper
than their customary adhesives. Aplastic anemia was first noted in this
population in 1961 and acute myeloblastic leukemia in 1967. A series of re-
ports by Aksoy and his colleagues have thoroughly described these findings
(Aksoy, 1977; Aksoy and Erdem, 1969, 1978; Aksoy, et al. 1966, 1971,
1972a,b, 1974a,b,c, 1975a,bi 1976a,b). Of particular note is the obvious
temporal relation to the onset of benzene use and the decline in new cases
since replacement of the benzene-containing adhesive in 1969. In a recent
review of 44 pancytopenia patients, Aksoy and Erdem (1978) noted that six
had developed leukemia. Previously they had observed 26 shoemakers with
acute leukemia during the period from 1967 to 1973. Also of interest is
that the peak incidence of acute leukemia appeared to follow that of aplast-
ic anemia by a few years. This is in keeping with the delayed onset of
acute leukemia frequently noted in case reports.
Another standard epidemiologic approach is the retrospective study,
which involves selection of a well-characterized population at risk and es-
tablishment of mortality patterns for that group. A number of major studies
of this type have been performed in the rubber industry and among other
workers exposed to solvents. Increased incidences of cancers of the lympha-
tic and hematopoietic systems were noted in male rubber workers when com-
pared to all manufacturing industry workers who died in 1959 (U.S. Dept. of
HEW, 1961). A higher incidence in deaths from these causes, particularly
from lymphocytic leukemia, was also observed in a series of studies evaluat-
ing the ten year mortality experience of male workers at four tire manufac-
turing plants (Andjelkovic, et al. 1976, 1977; McMichael, et al. 1974, 1975,
1976a,b). Some tendency toward an increase in hematopoietic neoplasms was
C-29
-------
noted by Monson and Nakano (1976a,b) in their studies of mortality in rubber
industry workers. However, no apparent increase in hematopoietic neoplasms
was noted by Mancuso and his colleagues in studies on occupational cancer
which focused on the rubber industry (Mancuso, et al. 1968; Mancuso and
Brennan, 1970). Infante, et al. (1977a,b) have recently reported a study of
the mortality of workers exposed to benzene in the rubber industry. Among
140 deaths observed in a cohort of 718 white males, seven leukemia deaths
were observed as opposed to fewer than 2 expected. Infante, et al.
(1977a,b) contended that benzene levels to which the affected individuals
were exposed did not exceed the Threshold Limit Value (TLV). This has been
questioned in view of testimony before the Occupational Safety and Health
Administration (OSHA) that levels exceeded 220 ppm in certain plant areas
(Harris, 1977).
Another recent mortality study by Ott, et al. (1978) found a higher
incidence of acute myeloblastic leukemia than expected among 594 chemical
workers with a history of benzene exposure. Of note is the observation by
U.S. EPA (1978a) that dose extrapolations derived from the findings of Ott,
et al. (1978) are not incompatible with those derived from Infante, et al.
(1977a,b) when inherent uncertainties in dose extrapolation are taken into
consideration.
Other epidemiological information which may be pertinent to benzene
leukemogenesis include the observation of higher than expected mortality
rates due to tumors of the lymphatic and hematopoietic systems among members
of the American Chemical Society (Li, 1969). Similarly, the highest leu-
kemia rates among British males divided into 27 occupational groups were
found in the group described as "professional, technical workers, artists"
C-30
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(Adelstein, 1972). This would include many types of workers exposed to ben-
zene as well as to radiation. A possible interaction between benzene expo-
sure and radiation was observed in a retrospective case control study of
Japanese atom bomb survivors in which those who developed leukemia had sign-
ificantly greater benzene and x-ray exposures than those who did not develop
leukemia (Ishimaru, et al. 1971). A study of cancer mortality among em-
ployees of the U.S. Government Printing Office reported an increased propor-
tionate mortality ratio for leukemia among binding workers who may have been
exposed to benzene (Greene, et al. 1979).
Other epidemiologic studies which have not found an association between
benzene exposure and hematologic neoplasms include a large-scale investiga-
tion of petroleum workers in which there was not an increased incidence of
acute leukemia (Thorpe, 1974). Furthermore, no statistically significant
increase in leukemia mortality has been observed in coke plant workers who
are exposed to benzene (Redmond, et al. 1972, 1976).
A more detailed critique of these studies is provided in the previous
EPA review of benzene exposure (U.S. EPA, 1978b). Inherent in epidemiologic
investigations is the Inability of any one study to prove causality. How-
ever, taken as a group, these studies of defined work populations leave
little doubt that benzene is leukemogenic in man.
In addition to pancytopenia and acute myeloblastic leukemia and its
variants, benzene has been implicated as causally related to a number of
other hematologic disorders. These include myeloproliferative disorders
such as chronic myelocytic leukemia, myeloid metaplasia, and essential
thrombocythemia, and lymphoproliferative disorders such as acute and chronic
lymphocytic leukemia, lymphocytic lymphomas, and a paraneoplastic condition
known as paroxysmal nocturnal hemoglobinuria. Case reports of benzene-
C-31
-------
exposed individuals who developed these disorders have been compiled by
Goldstein (1977b), and the strength of the association has been discussed by
the U.S. EPA (1978a). The causal relation between benzene and any one of
these diagnostic categories remains unproven. There is, however, reasonably
good evidence that a relationship does exist for chronic myelocytic leukem-
ia, myeloid metaplasia, chronic lymphocytic leukemia, and paroxysmal noc-
turnal hemoglobinuria and benzene exposure. Epidemiologic evidence of the
association of benzene exposure with lymphoma has been recently described by
Vianna and Pol an (1979) who reported an excess of deaths due to lymphoma in
males who had worked in various occupations where there was exposure to ben-
zene and/or coal tar fractions. The data are confounded by the preponder-
ance of farmworkers in the study cohort; the extent of exposure of this oc-
cupational subgroup is not known.
Individual host factors may account for variation in the degree of sus-
ceptibility to benzene. These include obesity, possibly because of the in-
creased solubility of benzene in fat; age, with younger individuals perhaps
at greater risk; sex, with females suggested to have greater risk; and high
ambient temperatures (Doskin, 1971; Greenberg, et al. 1939; Ito, 1962; Mai-
lory, et al. 1939). However, the evidence for any of these risk factors is
less than compelling. There is also some evidence of a familial tendency to
benzene hematotoxicity, suggesting genetic predisposition, but this is also
unproven (Aksoy, et al. 1974a; Erf and Rhoads, 1939). Similarly, observa-
tions suggesting that individuals with increased bone marrow turnover times
are more at risk for benzene hematotoxicity, while plausible, require exper-
imental confirmation (Aksoy, et al. 1975a; Gaultier, et al. 1970; Saita and
Moreo, 1959). Individual differences in rates of benzene metabolism would
C-32
-------
also be expected to affect toxicity. In addition to genetic factors, the
ingestion of food, alcohol, or drugs, or the inhalation of other solvents,
might alter benzene metabolism.
The possibility of individual variation in response should be consid-
ered as a possible explanation for the range of effects manifested as ben-
zene hematotoxicity. Pancytopenia has been, however, practically ruled out
as an idiosyncratic response to benzene. Based on animal studies, and on
evaluations of occupationally exposed groups in which most individuals ap-
pear to have been effected, it seems clear that the pancytopenic effect of
benzene exhibits classic dose-response characteristics. An idiosyncratic
reaction is perhaps more likely to be an explanation for benzene leukemo-
genesis in view of the lower incidence of leukemia when compared to pancyto-
penia and related disorders when large occupational groups are studied. For
instance, in a restudy of 125 of a group of 147 workers evaluated nine years
previously and of whom 107 had abnormal blood counts, only one was reported
to have developed acute leukemia (Goldstein, 1977b; NIOSH 1974). However,
Aksoy and Erdem (1978) recently reported that 6 of 44 significantly pancyto-
penic individuals that they followed developed acute leukemia. Fourteen of
the forty-four had died from aplastic anemia. This suggests that the pro-
pensity to develop acute leukemia as a result of benzene exposure may not be
rare. Based on present information, it is not unreasonable to assume that
everyone is at risk for benzene leukemogenesis.
In its production of hematotoxicity, benzene is relatively unique among
solvents. Most related compounds have negligible effects, if any, on the
bone marrow. Little is known concerning the mechanism by which benzene ex-
posure leads to hematotoxicity. The evidence suggests that it is a metabo-
lite of benzene which is toxic to hematopoietic precursors. The identity of
C-33
-------
this metabolite 1s unknown as is its physiochemical mode of action. Of
particular interest would be information as to whether the metabolite(s) is
(are) responsible only for destruction of precursor cells leading to pancy-
topenia or is fare) also capable of producing somatic mutation leading to
leukemia.
Chronic effects of benzene on the immunological system nave been re-
ported. Lange, et al. (1973a) found decreased levels of IgG and IgA and in-
creased levels of IgM in workers exposed to a combination of benzene, tol-
uene, and xylene. Lange, et al. (1973a) reported that the following air
concentrations of benzene had been measured in the work atmosphere:
0.11-0.158 mg/1 benzene, 0.203-0.27 mg/1 toluene, and 0.224-0.326 mg/1 xy-
lene for samples taken early in the study, and 0.0122-0.022 mg/1 benzene,
0.08-0.23 mg/1 toluene, and 0.12-0.63 mg/1 xylene for samples taken at a
later date. Some of these workers were found to have autoleukocyte agglu-
tlnins, suggesting the occurrence of an allergic blood dycrasia in some peo-
ple exposed to benzene and its homo logs (Lange, et al. 1973b). Smolik, et
al. (1973) have found significantly lower serum complement levels in workers
exposed to benzene, toluene, and xylene.
Although the causal relationship between benzene exposure and human
disorders is clear, the literature does not allow any conclusions to be
drawn on the dose-response relationship between benzene and these disorders
in humans. Some dose-response data on the effects of benzene on animals,
however, exist. Wolf, et al. (1956) reported that the no-effect level for
blood changes in rats, guinea pigs, and rabbits was below 88 ppm in the air
when the animals were exposed for 7 hr/day for up to 269 days. At this
level slight leukopenia was observed in rats; leukopenia was also seen in
rats given 132 daily oral doses of 10 mg/kg for 187 days. Jenkins, et al.
C-34
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(1970) found no effects on the blood composition of rats, guinea pigs, and
dogs exposed continuously to 17.65 ppm benzene for up to 127 days. Slight
leukopenia has been reported to occur in rats exposed to 44 ppm benzene for
5 hrs/day, 4 days/week for 5 to 7 weeks (Oeichmann, et al. 1963). Oeich-
mann, et al. (1963) exposed Sprague-Oawley rats to 15 to 831 ppm benzene
vapor for 20 hours/week for 6 to 31 weeks. Rats exposed to a mean concen-
tration of 65 ppm for 26 out of 39 days showed a decrease in white blood
cell count after 2 weeks in males and after 4 weeks in female rats. Animals
exposed to 47 ppm and 31 ppm exhibited abnormalities of the spleen and
lungs. Rats exposed to 831 ppm for 32 of 46 days showed a decrease in white
blood cell count that remained constant throughout the period of exposure.
Sprague-Oawley rats of different ages received oral doses of undiluted
benzene to determine the oral LD5Q (Kimura, et al. 1970). Acute LD50
reported are: immature rats, 3.4 g/kg; young adult rats, 3.8 g/kg; old adult
rats, 5.6 g/kg. A concentration of 0.87 g/kg body weight proved fatal to
newborn rats.
Dobashi (1974) measured the cell renewal rate as well as the rate of
DNA synthesis in cultured human leukocytes and HeLa cells exposed to ben-
zene. Both cell types exhibited 50 percent inhibition of growth at 171.6
mg/1. The rate of DNA synthesis in leukocytes was inhibited by 50 percent
at 171.6 mg/1, while in HeLa cells this effect occurred at 85.8 mg/1 benzene.
Synergism and/or Antagonism
The interaction of benzene with other solvents such as xylene and tol-
uene alters the rate of metabolism of benzene, thereby affecting benzene
toxicity. Animal investigations have indicated that benzene, toluene, and
perhaps other aromatic solvents, are oxidized by many of the same hepatic
enzyme systems (Ikeda, et al. 1972).
C-35
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Most reports on the human health effects of benzene have originated in
workers exposed to high concentrations of benzene in conjunction with other
solvents, e.g., toluene and xylene. Thus, it has been suggested that ben-
zene might act synergistically with other compounds to enhance hematotox-
icity. This synergism might possible explain the failure to induce leukemia
in animals with benzene (MAS, 1976).
Andrews, et al. (1977) suggested that benzene-induced bone marrow tox-
icity might be inhibited by co-administration of toluene due to inhibition
of hydroxylation of benzene. Inhibition of benzene metabolism by toluene may
result in increased toxic effects which may be due to benzene itself. The
toxic effects of benzene on the bone marrow are suspected to result from
action of metabolites of benzene,
Teratogenicity
The interest in the potential teratogenic effect of benzene is based
on the current recognition that some organic solvents are known to produce
congenital malformations in experimental animals. Furthermore, the reported
pancytopenia seen in workers exposed to toxic levels of benzene has raised
the possibility that benzene could adversely affect the cells of a develop-
ing embryo.
The first report of benzene-induced teratogenicity was by Watanabe and
Yoshida (1970) who administered a very high dose of benzene subcutaneously
(3 ml/kg body weight) to pregnant mice on day 13 of gestation. The fetuses
that were delivered by caesarian section on day 19 showed anomalies such as
cleft palate, agnathia (no lower jaw), and micrognathia (reduced lower
jaw). Other externally visible defects did not appear. The authors also
reported that no skeletal defects appeared in the vertebrae, ribs, or ex-
tremities. However, the anomalies produced have been shown to be commonly
encountered in normal or nonexposed mice.
C-36
-------
The noninhalation route of administering benzene has been used in two
other studies. Recently, Nawrot and Staples (1979) reported that adminis-
tration of benzene by gavage (0.3, 0.5, and 1.0 ml/kg) to CD-I strain mice
during days 6-15 of gestation resulted in significant maternal lethality and
in embryonic resorption. However, these authors also stated that no signif-
icant benzene-related change in incidence of malformation was seen in ani-
mals given 1 mg/kg benzene during days 6-15 or during days 12-15 of gesta-
tion. There were no congenital malformations in offspring of male mice that
were administered benzene intraperitoneally and subsequently mated to nonex-
posed females (Lyon, 1975).
The inhalation studies summarized in Table 6 show no congenital malfor-
mations in offspring of benzene-treated dams. Results varied from decreased
fetal weight to reduced number of fetuses per litter, to no effects at all.
Differences in animal strain, purity of compound, and duration of inhalation
could possibly account for some differences in results.
Four additional inhalation studies are summarized in Table 7. These
studies were designed to identify the effects of inhaled benzene vapor on
fetal growth and development. Thus, the exposure was limited to the period
of organogenesis, i.e., days 6 to 16 of gestation for rats and mice, and
days 6 to 18 of gestation for rabbits. Inhalation chambers, generally of
one cubic meter size, were employed, and animals were exposed to levels of
benzene ranging from 10 to 2,200 ppm for 6 to 7 hours per day.
In most inhalation studies summarized in Tables 6 and 7, the exposure
to benzene vapor affected the pregnant animal. Decreased gain in maternal
body weight with concommitant retardation of fetal growth can be related to
reduced food consumption during the treatment period, thus contributing to
the physiologic and metabolic stress of high doses of benzene. Unfortunate-
ly, simultaneous analyses of benzene levels in maternal blood during the
C-37
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TABLE 6
Benzene Teratology and Related Studies
STUDY SPECIES
Watanabe Mouse
d Yoshida
(1970)
EXPOSURE
LEVEL
3 ml /kg
ROUTE AND
DURATION OF
EXPOSURE
Subcutaneous
11-15 days
DECREASED
MATERNAL
WEIGHT
GAIN
None
DECREASED
FETAL COMMENTS
WEIGHT ON
GAIN OBSERVATIONS
Cleft palate,
agnathia,
micrognathia
Lyon
(1975)
Nawrot a
Staples
(1979)
Rat
Mouse
Gofmekler Rat
(1968)
Puskina,
•et al.
(1968)
Vozovaya
(1975)
Rat
Rat
0.5 ml/kg Intraperlotneal
0.3-1.0
ml/kg
210 mg/m3
(65 ppm)
670 mg/m3
(208 ppm)
1783 mg/m3
(559 ppm)
Gavage
Inhalation
Z4 Hr./oay
10-15 days
prior to
mating
Inhalation
throughout
pregnancy
Inhalation
4 mo. prior.
plus throughout
pregnancy
Yes -
not sig.
No effect on
Offspring.
[Exposure of
males in Dominant
Lethal Study]
Embryonic
Resorption
Deer, litter
size
Deer, litter
size
No malformations
for two
generations
C-38
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TABLE 6 (continued)
Benzene Teratology and Related Studies
STUDY SPECIES
Vozovaya Rat
(1976)
EXPOSURE
LEVEL
370 mg/m3
(116 ppm)
ROUTE AND
DURATION OF
EXPOSURE
Inhalation
4 mo. prior,
DECREASED
MATERNAL
WE IGHT
GAIN
DECREASED
FETAL
WEIGHT
GAIN
Yes
COMMENTS
ON
OBSERVATIONS
No malformations
Hudak & Rat
Ungvary Mouse
(1978)
1,000 mg/m3
(310 ppm)
plus throughout
pregnancy
Inhalation
Yes
No malformations
24 Hr./Day
1 to 14 days
of pregnancy
C-39
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TABLE 7
Sunuary of Benzene Inhalation Terotology
INHALATION DECREASED DECREASED
EXPOSURE MATERNAL FETAL
STUDY SPfCIES
Hazel ton, Rat
1975 (as
cited in
Murray, et
al. 1979)
Green, Rat
et al.1977
STRAIN
Sprague-
Dawley
Sprague-
Dawley
STUDY
(PP»)
0
10
50
500
100
300
BODY BODY
DURATION WEIGHT WEIGHT
day 6 to
day 16
of * «
gestation * *
day 6 to
day 16
DECREASED
CROWN COMMENTS
RUMP OR
DISTANCE OBSERVATIONS
-
_ _
* inalfonnations(l)
missing sternebra*
missing sternebra*
2,200
of
gestation
Murray,
et al.
1979
House
Rabbit
CF-1
•Statistically significant (p<0.05)
(l)exencephaly, angulated ribs, out-of-sequence ossification of forefeet
(most tn females)
nissing sternebra*
(most in females)
500
;aland 500
day 6 to - *
day 18
of
gestation
day 6 to
day 18 of
gestation
missing sternebra*;
delayed skull ossi-
fication*; unfused
occipital*
extra ribs*; lumbar
spur(s)*
c-»o
-------
period of exposure are not available to provide data on the amount of circu-
lating benzene or its metabolites accessible for possi-ble absorption across
the placenta! barrier.
Variations in number of sternebrae and ribs reported in several studies
are not generally considered malformations in the absence of other anomalies
(Kimmel and Wilson, 1973). An extensive report by Kimmel and Wilson (1973)
of skeletal deviations in rats, concluded that skeletal variants of this
type alone are not useful indicators of teratogenic potential. Palmer
(1968) reported that extra ribs are also a common occurrence in New Zealand
white rabbits. Incomplete ossification of the occipitals in the skull oc-
curs in 10 to 11 percent of control fetuses of Sprague-Dawley strain
(Charles River derived rats) according to Banerjee and Durloo (1973). De-
layed ossification of sternebrae is indicative of growth retardation which
may be attributed to nutritional imbalance.
The fetal malformations reported in the rat inhalation studies are sum-
marized in Table 7. Three types of malformation were reported at an expo-
sure level of 500 ppm in the Hazelton Study (Murray, et al. 1979). They in-
clude one exencephalic pup in 151 examined, one pup with angulated ribs in
107 pups examined, and two pups from two different litters with nonsequent-
ial ossification of the forefeet in 107 pups examined. Exencephaly may be
induced by food deprivation for as little as 24 hours (Runner and Miller,
1956). Miller (1962) reported that 24 hours of fasting in mice altered
vertebrate and rib formation. Thus, these malformations may have resulted
from maternal nutritional stress, or in view of the low incidence, may have
occurred entirely by chance. These findings were not reported in any other
study and, despite exposure of 184 fetuses to 2,200 ppm benzene by Green, et
al. (1978), no effects on the fetuses were observed.
C-41
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In the Hazelton Study (Murray, et al. 1979), the negative control group
contained only 12 pregnant females, fewer than in any of the treatment
groups (16, 15, and 14 pregnant rats at 10, 50, and 500 ppm, respectively).
The FDA guidelines published in 1966 specify that a minimum of 20 pregnant
animals per group are necessary to provide statistically significant re-
sults. Since each group began with 20 females and insemination occurred
prior to benzene exposure, such a low fertility index suggests the possibil-
ity of environmental or physical stress unrelated to the chemical. In addi-
tion, when fewer pups are available for evaluation in the control group than
in any treatment group, the likelihood of a spontaneous malformation arising
in the treatment group without a similar occurrence in the controls is in-
creased and such malformation cannot absolutely be considered a teratogenic
event.
Rat inhalation studies were performed by Green, et al. (1978) at expo-
sure levels of 100, 300, or 2,200 ppm and in the Hazelton Study (Murray, et
al. 1979) at 10, 50, or 500 ppm. There were no significant changes in inci-
dence of resorptions at exposure levels as high as 2,200 ppm or 500 ppm, re-
spectively (Table 8).
Although chronic exposure to benzene may constitute a fetotoxic or
teratogenic hazard, the inhalation studies discussed are too inconclusive to
either confirm or refute the hypothesis. Coincidentally, a recent review of
the embryonic and teratogenic effects of benzene concluded with the follow-
ing statement: "Since reports of effects of benzene on teratogenesis are
few, and the concentrations of benzene used are very high, the role of ben-
zene in teratogenesis cannot be predicted with confidence at this time"
(U.S. EPA, 1978b).
In summary, from available data, it is unlikely that benzene adminis-
tered by inhalation during the principal period of organogenesis constitutes
a teratogenic hazard. However, results are not conclusive and do not apply
C-42
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TABLE 8
Effect of Benzene inhaled by Pregnant Rats on the Physical Parameters of the Litter
GREEN, et al.
BENZENE CONCENTRATION
(PPM)
Number of Litters
Implantation
Sites/Litter
Live Fetuses/
Litter
Percent Resorptions/
Implantation
Sites*
Percent Litters with
Resorptions*
I itters Totally
Hesorbed
Kesorptions/
Litter with
Resorptions**
CONTROL
16
11. fi
10.4
11
(22/188)
50
(8/16)
0
?.B
(22/8)
BENZENE
100
18
11.8
11.8
5
(12/255)
44
(8/18)
0
1.5
(12/8)
CONTROL
15
11.9
11.1)
7
(14/179)
46
(7/15)
0
2.0
(U/7)
1978
BENZENE
300
16
13.4
12.2
9
(20/125)
62
(10/16)
0
2.0
(20/10)
HURRAY, et a). 1979 (HAZELTON STUDY)
CONTROL
14
12.6
12.1
5
(8/151)
42
(6/14)
0
1.3
(8/6)
BENZENE
2,200
15
13.0
12.3
4
(8/195)
33
(5/15)
0
1.6
(8/5)
CONTROL
11
10.8
9.7
10.1
(12/119)
45
(5/11)
1
2.4
(12/5)
BENZENE
10
15
13.1
12.5
4.1
(8/197)
33
(5/15)
0
1.6
(8/5)
BENZENE
50
15
8.7
8.5
3.1
(4/131)
20
(3/15)
0
1.3
(4/3)
BENZENE
500
14
11.8
10.8
8.5
(14/165)
57
(8/14)
0
l.B
(14/B)
*(H|/N;>) represents the number actually observed over the total number passible.
**(Ni/N2) represents total nuuber of resorptions per litter in which resorptions occurred.
C-43
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to other stages of the reproductive cycle. The effects of benzene on male
and female fertility, preimplanation development, parturition, and lactation
need to be evaluated.
Hutagenicity
The cytologic and cytogenetic effects of benzene have been thoroughly
reviewed by Wolman (1977), and in the 1978 EPA Review of benzene health ef-
fects. Benzene has not shown mutagenic activity in the Salmonella/microsome
i_n vitro assay (Lyon, 1975; Shahin, 1977; Simmon, et al. 1977). It has
shown such activity, however, in animals and man. Chromosomal abnormalities
in bone marrow cells have been reported as a consequence of experimental
benzene exposure in a number of species, including rats (Lyapkalo, 1973;
Dobrokhotov, 1972; Philip and Jensen, 1970; Snyder, et al. 1978), rabbits
(Kissling and Speck, 1972), mice (Snyder, et al. 1978), and amphibians
(Rondanelli, et al. 1961, 1964). In rabbits injected subcutaneously with
0.2 mg/kg/day benzene, the frequency of bone marrow mitoses with chromosomal
aberrations increased from 5.9 percent to 57.8 percent after an average of
18 weeks (Kissling and Speck, 1972). Dobrokhotov (1972) exposed rats to 0.2
g/kg/day benzene and 0.8 g/kg/day toluene individually and together, and
found similar rates of chromosomal aberrations in the two chemicals given
separately, and an additive effect when given together. Chromatid deletions
in metaphase chromosomes of bone marrow cells have been found in rats given
single doses of subcutaneous benzene at 2 ml/kg (Philip and Jensen, 1970),
and rats given subcutaneous benzene at 1 g/kg/day for 12 days (Lyapkalo,
1973). Lyon (1975) dosed rats with 0.5 ml/kg benzene intraperitoneally, and
found no induced dominant lethality but increased chromatid and chromosomal
abberrations. Lyon (1975) also found increased micronuclei counts 6 hours
after final dosing of rats at 0.05 and 0.25 ml/kg intraperitoneally on each
C-44
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of two successive days. Cytogenetic abnormalities have also been observed
In human lymphocytes cultured 1n vitro 1n the presence of benzene. Koizumi,
et al. (1974) observed gaps and breaks 1n chromosomes of human leukocytes
Incubated for 72 hours at 37*C 1n tissue culture medium containing 30 per-
cent calf serum to which benzene in a concentration of 2.2 x 1CT3M, 1.1 x
1(T3M, 2.2 x 10"^, 1.1 x 10"^, or 2.2 x 10~5M was added. Haber-
landt and Mente (1971) also reported chromosomal aberrations in human
leukocyte cultures treated with benzene.
Benzene 1s clearly a mltotic poison, producing a decrease in DNA syn-
thesis in animal bone marrow cells jm vitro and in cultured human cells
(Boje, et al. 1970; Dobashi, 1974; K1ssl1ng and Speck, 1972; Koizumi, et al.
1974; Matsushita, 1966; Speck, et al. 1966). There is also ample evidence
of cytogenetic abnormalities in benzene-exposed individuals particularly
those with clinically evident hematotoxicity (Buday, et al. 1971; Cobo, et
al. 1970; Erdogan and Aksoy, 1973; Fornl and Moreo, 1967; Forni, et al.
1971a; Harberlandt and Mente, 1971; Hartwich, et al. 1969; Marchal, 1952;
Pollini and Colombi, 1964; Pollini, et al. 1964). Such abnormalities may
persist for many years despite cessation of benzene exposure (Forni, et al.
1971b). A more important, and still controversial, consideration has been
whether or not occupational exposure to benzene levels not producing overt
hematological effects are capable of causing chromosomal abnormalities.
In patients with benzene-induced aplastic anemia, lymphocyte chromosome
damage, i.e., abnormal karyotype and deletion of chromosomal material, has
been found (Pollini and Colombi, 1964). Pollini, et al. (1964) later found
a 70 percent incidence of heteroploid chromosomal patterns in the blood lym-
phocytes and bone marrow parenchyma cells of each of four subjects with ben-
zene-induced blood dyscrasia. Chromosomal alterations associated with ben-
C-45
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zene-induced blood dycrasias have also been reported b-y others (Forni and
Moreo, 1967, 1969; Hartwich, et al. 1969; Khan and Khan, 1973; Sellyei and
Kelemen, 1971; Tough and Court-Brown, 1965).
In a more recent study, Funes-Oavioto, et al. (1977) have reported a
significantly increased frequency of chromatid and isochromatid breaks in
the cultured lymphocytes of workers in chemical laboratories and in the
printing industry. A total of 73 individuals from seven different occupa-
tional groups of 15 or fewer members each were evaluated. Exposure to ben-
zene was suspected or documented in each group. In some cases there had
been sufficiently high exposure to result in hematological effects. The
authors discounted the likelihood of x-irradiation significantly contribut-
ing to the results. As with many of the other studies in occupational
groups, there was a relatively low correlation between length of exposure
and frequency of chromosome breaks. The authors also noted an increased
frequency of sister chromatid exchange in the lymphocytes of 12 laboratory
technicians but not in 4 rotoprinting workers as compared to control
groups. Of particular note in this study is the finding of a significantly
higher level of chromosome aberrations in the children of 14 mothers who had
been exposed to solvents during pregnancy while working as laboratory tech-
nicians; chromosomal aberrations were found in 7 children of non-exposed
mothers (9.8 percent abnormal cells vs. 2.4 percent abnormal cells,
p <.01). In other studies which evaluated relatively healthy workers,
chromosome changes were detected in workers who were exposed to less than 10
ppm benzene (Berlin, et al. 1977; Kilian and Daniel, 1978; Picciano, 1978).
Vigliani and Forni (1969) found a significant increase of peripheral
blood lymphocyte chromosomal aberrations in workers exposed to benzene, but
not in those exposed to toluene and xylene. Some of these aberrations per-
sisted for several years after recovery from benzene hemopathy. The authors
C-46
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hypothesized that leukemia may develop in cases where a potentially leukemic
clone of cells with selective advantage is produced as a response to benzene
exposure. Forni, et al. (1971a) examined chromosomal aberrations in 34
workers in a rotogravure plant and 34 matched controls, and found a signifi-
cantly higher number of both stable and unstable aberrations in the 10 ben-
zene-exposed workers but a normal number in the 24 toluene-exposed workers.
Forni, et al. (1971b) found significantly increased stable and unstable
chromosomal aberrations in 25 subjects who had recovered from benzene hemo-
pathy. Most of these persisted for several years after cessation of expo-
sure and recovery. A correlation between benzene exposure and chromosomal
aberrations has been reported by Tough, et al. (1970) and Hartwich and
Schwanitz (1972), in the latter case after "low levels" of benzene exposure.
A recent report (Kilian and Daniel, 1978) on 52 workers exposed to ben-
zene for 1 month to 26 years (mean of 56.6 months) found chromosomal aberra-
tions (chromosome breaks, dicentric chromosomes, translocations, and ex-
change figures) 1n peripheral lymphocytes at two to three times the rates
found 1n controls. In this study the 8-hour average time-weighted benzene
exposure was 2 to 3 ppm, the average concentration determined by 15-minute
sampling was 25 ppm, and the peak concentration was 50 ppm.
Taken together these studies clearly indicate a causal relation between
benzene exposure and persistent chromosomal abnormalities. The implications
of such observations to benzene-induced leukemia are reasonably convincing
in view of the analogous findings in radiation leukemogenesis as well as a
large body of evidence supporting the role of somatic mutation in carcino-
genesis. More evidence is needed before the slight, but statistically sig-
nificant, increases in cytogenetic abnormalities observed in occupationally
exposed workers can be related to leukemogenesis and ascribed with certainty
C-47
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to relatively low levels of benzene. At present, there is no correlation
between the degree or length of exposure, the clinical symptoms, and the ex-
tent of persistence of chromosomal aberrations (U.S. EPA, 1977).
Carcinogenicity
Liqnac (1932) reported the occurrence of leukemia in 8 of 33 albino
mice subcutaneously injected with 0.001 ml benzene in 0.1 ml olive oil week-
ly for 17 to 21 weeks. These results remain in question, however, since no
controls were used (Int. Agency Res. Cancer, 1974). Kirschbaum and Strong
(1942) found leukemia in 6/20 mice (30 percent) subcutaneously injected with
0.001 ml benzene in sesame oil weekly, compared with 29/212 (14 percent) in
controls, the difference being not statistically significant. Amiel (1960)
gave weekly subcutaneous injections of 0.001 ml benzene in 0.1 ml olive oil
for life to AKR, OBA2, CeH, and C57BL6 mice, in groups of 30 males. No can-
cer was found in any mice of the OBA2, C3H, and C57BL6 strains. Eight of 30
treated AKR mice developed leukemia, as did 30/35 untreated AKR mice.
Hiraki, et al. (1963) injected five female and five male mice with 0.1 ml of
a 1 percent solution (0.087 mg) of benzene in olive oil each week. Two mice
died in 8 weeks; the remaining eight mice were treated for 10 weeks. Of
these, two males and three females developed subcutaneous sarcomas. Three
of these tumors were transplantable into syngenetic mice. No controls were
reported. Ward, et al. (1975) subcutaneously injected weanling male C57BL
6N mice twice weekly for 44 weeks and once weekly for the last 10 weeks,
gradually increasing the dose from 450 mg/kg to 1.8 g/kg benzene. The mice
were killed 104 weeks after the first injection, and no evidence of
carcinogenic activity was found in either the benzene-treated or negative
control mice. Butylnitrosourea induced leukemia, lymphomas, and/or
intestinal neoplasms in almost all the positive controls.
C-48
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In a preliminary report, Maltoni and Scarnato (1979) found Zymbatl's
gland carcinomas in 8 of 32 female Sprague-Oawley rats which received 250
mg/kg benzene in olive oil by gavage once daily 4 to 5 days per week for 52
weeks, and in 2 of 30 female Sprague-Dawley rats which received 50 mg/kg.
No such tumors were found in olive oil controls. Maltoni and Scarnato
(1979) also reported increased incidence of mammary carcinomas in female
rats and of leukemias in both male and female rats that were similarly
treated (Table 4).
Numerous studies on the effects of skin application of benzene to mice
(many where benzene was the solvent control) have yielded negative results
(Baldwin, et al. 1961; Burdette and Strong, 1941; Coombs and Croft, 1966;
Kirschbaum and Strong, 1942; Laerum, 1973). Inhalation (Jenkins, et al.
1970; Wolf, et al. 1956) and oral (Wolf, et al. 1956) dosing likewise have
yielded negative carcinogenic results. In a recent inhalation study, Snyder
et al. (1980) observed on increased incidence of thymic lymphoma in C578L
mice by exposing to 300 ppm of benzene (Table 9). It should be noted that
C57BL strain carries a virus which can result in high incidence of lymphoma
following exposure to radiation, carcinogens, or immunosuppressive agent
(Koplan, 1967; Igel, et al. 1969; Imamura, et al. 1973). In the same Insert
experiment using AKR mice, a strain which also carries a virus that can
spontaneously induce lymphoma (Kahn and Novak, 1973), Snyder, et al. (1980)
could not find any change in the induction of lymphoma in this strain by
benzene. Nelson (1977) has found leukemia in 2/40 CD-I mice given lifetime
exposures to 300 ppm benzene; one had chronic myelogenous leukemia and one
had an acute, possibly myeloblastic leukemia. A third mouse died of myeloid
metaplasia. Nelson also found chronic granulocytic leukemia in 1/40
Sprague-Oawley rats given lifetime exposures to 100 ppm benzene.
C-49
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TABLE 9
Histological Evaluation of C57BL Mice Exposed to
300 ppm Benzene and of Air Sham*
, _ Incidence
Neoplasm Type Test C
ontrol
1. Hematopoietic neoplasms 8/40 2/40
2. Bone marrow hyperplasia without 13/32 0/38
evidence of hematopoietic neoplasm
3. Spleen hyperplasia without 16/32 2/38
hematopoietic neoplasm
*Source: Snyder, et al. 1980.
C-50
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Thus far, animal experiences do not support conclusively the view that
benzene is leukemogenic. Ward, et al. (1975) suggested that benzene-induced
leukemia in man may be a fairly rare event occurring only in highly sensi-
tive individuals, because of genetic constitution, or because of synergistic
action with other environmental agents. Another point suggested to explain
the difference between man and animal models was a difference in metabolism
of benzene (NAS, 1976).
Despite essentially negative animal data, the evidence that benzene is
a leukemogen for man is convincing and has recently been reviewed by NAS
(1976), NIOSH (1977), and U.S. EPA (1977).
Over 250 cases of leukemia in benzene exposed individuals have been re-
ported in the literature since the original description by Delore and Borgo-
mano in 1928, essentially all of them in an occupational setting (Benzene in
the Work Environment, 1974). These case reports, however, do not establish
benzene as a leukemogen because of the possiblity of chance association,
lack of information on the size of the population at risk, and chance of un-
derreporting of benzene-associated leukemia due to acceptance of the rela-
tionship (thus inhibiting publication) or due to the lag period between ex-
posure and onset of leukemia. These case reports do, however, suggest such
leukemogenic properties. Conspicuous in these reports is the frequent
description of persons suffering from benzene-associated pancytopenia in
whom evolution to acute leukemia was observed. Idiopathic aplastic anemia
is an uncommon disorder, reported far less frequently than acute myelo-
geneous leukemia. The relatively frequent documentation of benzene assoc-
iated pancytopenia progressing to acute leukemia, similar to that observed
in other causes of aplastic anemia, further supports the possibility that
exposure to benzene increases the risk of developing acute leukemia (U.S.
EPA, 1977).
C-51
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Oelore and Borgomano (1928) first described the association between
benzene exposure and leukemia in a worker exposed to benzene for 5 years,
who developed acute lymphoblastic leukemia. In 1939 two cases of leukemia
among patients who had chronic benzene exposure in the industries around
Boston were described (Bowditch and Elkins, 1939; Hunter, 1939; Mallory, et
al. 1939). One patient had been exposed to benzene for 10 years, 4 years
heavily (200 ppm) and the succeeding 6 years lightly, but had displayed
hematologic evidence of benzene intoxication from the beginning of his em-
ployment. In the last 3 months of his life, the typical pattern of an acute
myeloblastic leukemia developed. The characteristic findings of leukemia
were found at autopsy which included diffused myeloid infiltration of the
liver, spleen, and bone marrow. The other case was a 12-year-old boy, a
painter's son, who used his father's paint shop to repaint toys, using a
paint remover known to contain benzene. He developed aplastic anemia but
sternal puncture and sternal biopsy revealed a typical leukemia replacement
of the marrow with undifferentiated cells of the lymphoblastic series. De-
Gowin (1963) reported a case involving a painter who had been exposed to
benzene for 13 years. He developed a hypocellular bone marrow and pancyto-
penia, followed by a relatively normal bone marrow with variable leukopenia,
anemia, and thrombocytopenia. Then after 15 years a distinctly leukemic
marrow and pancytopenia were found. Tareeff, et al. (1963) described six
acute and 10 chronic leukemia cases in workers in the U.S.S.R. occupational-
ly exposed to benzene for 4 to 27 years. In three of the acute cases a
latent period of 2 to 5 years from cessation of exposure was noted.
Although case reports have suggested that benzene causes leukemia, con-
vincing evidence has come from epidemiological studies. Many of these have
come from Aksoy and his colleagues in Turkey (Aksoy, 1977; Aksoy, et al.
1972b, 1976a,b, 1977a,b). They described individual case reports of workers
C-52
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with aplastic anemia progressing through a preleukemia phase to acute myelo-
blastic leukemia or erythroleukemia; an accumulation of cases resulting in a
statistically significant higher incidence of acute leukemia among shoe
workers; and an outbreak of leukemia in this population that appears tempor-
ally related to the onset of benzene use and that has subsided following re-
placement of benzene as a solvent for adhesives.
Aksoy, et al. (1974b) observed 26 cases, during the period 1967-73, of
acute leukemia among 18,500 shoe workers exposed to maximums of 210 to 650
ppm benzene for 1 to 15 (mean 9.7) years. Fourteen cases were acute myelo-
blastic leukemia, four preleukemia, three acute erythroleukemia, three acute
lymphoblastic leukemia, one acute promyelocytic leukemia, and one acute
monocytic leukemia. From these data they derived a leukemia incidence of 13
per 100,000, which is statistically significantly higher than the risk of 6
per 100,000 assumed for the general population. The latter figure is de-
rived from leukemia incidence in more developed countries than Turkey and
thus may be high. Aksoy (1977) recently estimated the incidence of leukemia
in the general population of Turkey as 2.5 to 3.0 per 100,000. Moreover, if
the relative incidence were computed solely for acute myeloblastic leukemia
and its variants, a magnification of the risk in benzene-exposed shoe work-
ers would be observed. Secondly, in their series the average age at the
diagnosis was 34.2 years. This is a relatively low-risk age period for leu-
kemia, with a reported death rate about half of the overall incidence
(Cooke, 1954). Recalculation of their data with an age factor would presum-
ably increase the statistical significance of the findings (U.S. EPA,
1977). Thirdly, Aksoy (1977) believes that shoe workers with acute leukemia
were probably admitted to other Istanbul hospitals without his knowledge.
C-53
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Aksoy, et al. (1976b) reported that, of 34 patients, six exposed to 150
to 210 ppm benzene vapor for up to 28 years (mean exposure: 11 years) were
diagnosed as having Hodgkin's disease. Twenty other patients also exposed
to benzene were later diagnosed as leukemics. Based on case studies, the
authors stated that benzene, because of its toxicity to both the hemato-
poietic and reticuloendothelial system, is etiologically related to the on-
set of Hodgkin's disease. Alternatively, the authors proposed that benzene
may act with other unknown factors contributing to the onset of this pro-
liferative disorder.
Aksoy (1977) presented his observations of acute leukemia in shoe work-
ers for the period 1967-76. These annual incidence data appear below:
1967
1968
1969
1970
1971
1
1
3
4
6
1972
1973
1974
1975
1976
5
7
4
3
0
The peak incidence (19.7 per 100,000) of leukemia in shoe workers occurred
between 1971 and 1973. This follows by a few years the appearance of a not-
able incidence of aplastic anemia in this occupational group. The decline
in cases since 1973 is temporally related to a decrease in use of benzene as
an adhesive solvent, which began gradually in 1969. Aksoy also reports that
pancytopenia was present in 27.5 percent of the cases before the onset of
acute leukemia, which occurred 6 months to 6 years later. The hematological
findings often indicated a period of recovery before the onset of leukemia,
a phenomenon also noted by other investigators. Aksoy states that, during
this period, over 100 cases of aplastic anemia were observed that were
either idiopathic or associated with an agent other than benzene, and in
C-54
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none of these cases did acute leukemia develop. He also states the opinion
that no blood dyscrasia is required before the other onset of leukemia and
provides an example of a 23-year-old shoe worker who was hematologically
normal when studied 4 years before the onset of acute erythroleukemia.
Vigliani and Saita (1964) estimated the number of workers exposed to
benzene in northern Italy, and, based on the incidence of acute leukemia in
the general population of Milan, calculated a 20-fold higher risk of acute
leukemia in these workers. More recently Vigliani and Form' (1976) summar-
ized their experience from 1942 to 1975. During this period they observed
66 cases of significant benzene hematotoxicity in Milan, mostly in shoe
workers; 11 of these were acute myelogenous leukemia. In Pavia during the
period 1959-74 they observed 135 shoe workers with benzene hematotoxicity,
13 with acute myelogenous leukemia. Benzene concentrations were usually 200
to 500 ppm. They also observed two cases of myelogenous leukemia in the
rotogravure industry where ambient benzene exposures were calculated to be
200 to 400 ppm, with peaks up to 1,500 ppm.
Ishimaru, et al. (1971) performed a retrospective study of survivors of
the two atomic bombings of Japan, evaluating the effects of occupation on
the incidence of leukemia. Two occupations were considered to involve expo-
sure to benzene, and these occupations taken together were associated with
an increased risk for leukemia (30 cases, 14 controls, relative risk * 2.3
p<0.01). Twenty-four leukemia cases were too far from the atomic bomb ex-
plosion for radiation to have influenced the increased risk. The increased
risk, however, could be associated with exposures other than to benzene, as
in none of the 10 occupations considered would benzene be the only chemical
encountered. The risk was significantly higher in those with 5 or more
years of potential exposure but not in those who had been employed in such
C-55
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occupations for less than 5 years. The relative risks were similar in
Hiroshima and Nagasaki and were higher for acute leukemia (2.9) than for
chronic leukemia (1.8).
Girard and Revo! (1970) evaluated the frequency of a positive history
of benzene exposure in 401 patients hospitalized with serious hematological
disorders, compared with 124 patients hospitalized for other reasons. A
statistically significant increase in history of benzene exposure was found
in patients with aplastic anemia (10/48, 21 percent), acute leukemia
(17/140, 12 percent), and chronic lymphocytic leukemia (9/51, 15 percent)
compared with the control patients (5/124, 4 percent).
The Occupational Health Studies Group of the University of North Caro-
lina has studied the health status of rubber-industry workers, a group ex-
posed to various solvents including benzene (Andjelkovic, et al. 1976, 1977;
McMichael, et al. 1974, 1975, 1976a,b; Tyroler, 1977). They have evaluated
the 10-year mortality experience of a large cohort of male workers (5,106
deaths) at four tire manufacturing plants. The subjects were in the work
force or were retired in 1964. The mortality due to all cancers (1,014) was
normal or slightly elevated, depending on the data base used for compar-
ison. Deaths due to cancer of the lymphatic and hematopoietic system (total
of 109) were 31 percent higher than expected and were increased in cohorts
of each of the four companies. In the category of lymphosarcoma and
Hodgkin's disease, the standard mortality ratio (SMR) was 129 and an in-
crease in the expected number of deaths was observed in two of the four com-
pany cohorts. Similarly, for deaths due to all forms of leukemia the SMR
was 130 and the increase was observed in three of the four cohorts. When
this latter category was further subdivided, the overall SMR for lymphatic
C-56
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leukemia was found to be 158 and the expected death rate was elevated in two
of the four company cohorts. Of particular note is that the SMR for deaths
attributed to lymphatic leukemia was 291 in the age group 40 to 64.
Several approaches were followed in further study of the increased in-
cidence of lymphatic leukemia. Contrasting the work history of 17 patients
with lymphatic leukemia with those of three matched controls for each case
revealed that solvent exposure increased the overall risk by a factor of
3.25. Further classifying the groups according to high, low, and medium
solvent exposure yielded a 5.5 factor for the high-exposure group. In those
patients first subjected to high exposure between 1940 and 1960, the factor
for the relative risk of lymphatic leukemia was 9.0. The relationship of
solvent exposure to lymphatic leukemia was statistically significant at
p<0.025. The study also showed an increase in the mean difference in years
of work history between lymphatic leukemia and the case controls. This was
inversely proportional to the extent of solvent exposure. A limitation is
the lack of historical data concerning the benzene exposure or the concen-
trations of other solvents, e.g., xylene, toluene, and trichloroethylene.
These studies do, however, strongly support the possibility that long-term
exposure to benzene in the U.S. rubber industry leads to an increased risk
of lymphatic leukemia (U.S. EPA, 1977).
Monson and Nakano (1976a,b) evaluated a cohort of 13,571 white male
rubber workers and found an SMR of 128 for leukemia.
Thorpe (1974) surveyed 38,000 workers from eight European affiliates of
a major petroleum company to determine if there were differences in leukemia
incidence rates between workers in occupations in which there was possible
benzene exposure (such as refinery workers) and those in occupations where
there was no exposures (office workers). Leukemia incidence rates were de-
termined over a ten-year period from 1962 to 1971. As there were no benzene
C-57
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sampling data, actual exposures were unknown, and the workers were grouped
on the basis of "potential exposure" to benzene, determined by the nature of
their work. The data obtained revealed no statistically significant differ-
ences in leukemia incidence rates between exposed workers and standard age-
adjusted populations. Thorpe (1974) reported increased, but not statistic-
ally significant, incidence rates in benzene-exposed workers when compared
with the nonexposed workers in the study. The case-finding techniques used
by Thorpe (1974) and the reliability of the number of reported leukemia
cases were criticized by Brown (1975).
The most convincing epidemiological study implicating benzene as a leu-
kemogen is the recent one by Infante, et al, (1977a) from the National In-
stitute for Occupational Safety and Health. They followed for vital status,
up to mid-1975, 748 white males exposed to benzene in the manufacture of a
rubber product from 1940 through 1949. A statistically significant
(p<0.002) excess of leukemia was found in comparison with two control popu-
lations, the general American population, and another industry not using
benzene. There was a fivefold excessive risk of all leukemias and a tenfold
excessive risk of myelocytic and monocytic (probably myelomonocytic) leu-
kemias combined. The single case of chronic myelocytic leukemia had a lag
period of 2 years from initial benzene exposure, but the six cases of acute
myelocytic and monocytic leukemia had lag periods of 10 to 21 years. The
true leukemia risk to benzene-exposed workers was thought to be much higher
because the follow-up of the study population was only 75 percent complete,
and the remaining 25 percent were all regarded, in the calculations, as be-
ing alive at the end of the study period. The environment of the workers
was not contaminated with any solvents other than benzene, and benzene con-
centrations in the air were generally below the recommended limit in effect
C-58
-------
during the period of the study, i.e., 100 ppm (1941), 50 ppm (1947), 35 ppm
(1948), 25 ppm (1957), and 10 ppm (1969). In general, this epidemiological
study provides excellent confirmatory evidence of the causal relationship of
benzene exposure to acute myelocytic leukemia (U.S. EPA, 1977).
Ott, et al. (1978) recently studied the mortality experience of 594
workers exposed to benzene in the chemical industry. The workers were stra-
tified by benzene exposure levels, and hematological findings were carefully
examined. The cause-specific mortality rates for the 102 deceased individ-
uals agreed well with those observed in a study of over 8,000 other employe-
es in the same area. No association with benzene exposure was detected;
however, two deaths due to acute myelogeneous leukemia, and one with myelo-
blastic leukemia listed as a significant associated condition, occurred.
The time-weighted average benzene exposure of these three individuals was
below 10 ppm. The expected number of myelogenous leukemia cases in this
study population is 0.8, and the observed number of three is only of margin-
al statistical significance. These inconclusive findings may be due to the
small number of deaths evaluated in the study (U.S. EPA, 1977).
With reference to the quantitative relationship of benzene exposure
level to the development of acute leukemia, the available literature is in-
adequate for the generation of dose-response curves (U.S. EPA, 1977). In
contrast with pancytopenia, where a large percentage of benzene-exposed in-
dividuals have developed benzene hematotoxicity and thus the available moni-
toring information might be used to estimate the average benzene exposure,
leukemia occurs in a very small percentage of the benzene-exposed, and those
developing leukemia may have been exposed to higher concentrations than in-
dicated by area-wide monitoring systems. This exposure might occur because
of the specific job involved or faulty work habits, e.g., failure to wear a
C-59
-------
respirator. In those studies of acute leukemia where benzene exposur^
levels have been reported, the concentrations have generally been above 100
ppm (Aksoy, et al. 1972, 1974a,b, 1976a,b; Vigliani and Forni, 1976; Vig-
liani and Saita, 1964; Kinoshita, et al. 1965; Sellyei and Kelemen, 1971).
The often-reported longer period of benzene exposure required for the de-
velopment of acute leukemia than for pancytopenia might well be a spurious
consequence of the frequent lag period between the initiation of benzene ex-
posure and the development of acute leukemia.
Also reported in association with benzene exposure have been lymphosar-
coma (Bousser, et al. 1948; Caprotti, et al. 1962), Hodgkin's disease (Ak-
soy, et al. 1974c; Mallory, et al. 1939), reticulum cell sarcoma (Paterni
and Sarnari, 1965), and multiple myeloma (Tareeff, et al. 1963; Torres, et
al. 1970), but none of these case reports suggests other than a chance rela-
tion to benzene exposure (U.S. EPA, 1977).
C-60
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CRITERION FORMULATION
Existing Guidelines and Standards
Existing air standards for occupational exposure to benzene include 10
ppm (32 mg/m3) and an emergency temporary level of 1 ppm by the U.S. Occu-
pational Safety and Health Administration (NIOSH, 1974, 1977), 25 ppm (80
mg/m3) by the American Conference of Governmental Industrial Hygienists
(AC6IH, 1979), 16 ppm promulgated by Czechoslovakia in 1969, and 6 ppm (20
mg/m3) promulgated by the Soviet Union in 1967. OSHA also prohibits re-
peated or prolonged skin exposure to liquid benzene. No standard for ben-
zene in water exists, but Cleland and Klngsburg (1977), using several as-
sumptions and ACGIH air standards, have suggested values of 1,071 and 414
ug/1 for ingested water, and 107 ug/l for ingested water based on the poten-
tial carcinogenicity of benzene.
Current Levels of Exposure
As discussed previously under "Exposure," the major source of human ex-
posure to benzene ,is through the respiratory route. The annual average ex-
posure of an individual to ambient benzene from all air sources is 1.03 ppb
(Mara and Lee, 1977).
The U.S. EPA (Mitre Corp., 1978) has attempted to put into perspective
the known and unknowns about total benzene exposure for its National Drink-
Ing Water Program. Based upon the assumptions utilized, air was the predom-
inant source of benzene absorbed by the general population. This source
contributed more than 80 percent of the total daily benzene uptake for an
adult male living in an urban environment. Assumed benzene content in
drinking water Included levels of 0.1, 0.2, 1.0, and 10 ug/l, food was 250
jig/1, and ambient air was 50 ug/m3. The total daily intake at the 10
C-61
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benzene level for drinking ^water was 1.128 rag/day of which 1.4 percent came
from the water, 17.7 percent came from food, and 80.9 percent came from
ambient air exposure.
As shown by Mara and Lee (1977) certain occupational groups have poten-
tial exposure to benzene over and above the ambient levels. The representa-
tive industry activities include chemical manufacturing, coking operations,
gasoline service stations, petroleum refineries, and solvent operations.
Special Groups at Risk
There is some suggestion that there may be genetic predisposition to
benzene toxicity; this subject is reviewed by Goldstein (1977b). Although
there are many more cases of benzene-induced hematotoxicity in males than in
females because of occupational exposure, there is evidence to suggest that
exposed females have a greater chance of developing severe disease (Mailory,
et al. 1939; Ito, 1962). Age does not seem to affect hematotoxicity (Aksoy,
et al. 1971).
Basis and Derivation of Criterion
The MAS (1977), in its review of drinking water and health, concluded
that existing animal and human data did not allow the establishment of
limits for benzene in drinking water. This was because the animal results
were not statistically significant and were based on nonoral administration
of benzene. In addition, the occupational studies on human exposure did not
contain adequate information on degree of exposure or size of the population
at risk, and did not rule out exposure to other chemicals besides benzene.
However, most significant findings of Maltoni and Scarnato (1979) and those
of Goldstein, et al. (1980) provided strong evidence for leukemogenic activ-
ities of benzene in Sprague-Oawley rats. Furthermore, prevalence of other
types of tumors were observed (Tables 4 and 5).
C-62
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Since the publication of the NAS report, the above-described epidemio-
logical studies by Aksoy (1977), Infante, et al. (1977), and Ott, et al.
(1978) have appeared. These studies include information on degree of ben-
zene exposure and size of the population at risk, and rule out exposure to
solvents other than benzene. The U.S. EPA Carcinogen Assessment Group
(1978a) has made use of these three occupational studies to calculate a leu-
kemia dose-response curve. The slope of this curve is 0.024074, in units of
lifetime risk of leukemia per ppm exposure to benzene in air. Since 1 ppm
is 3.25 mg/m , and assuming a respiratory rate of about 20 m /day and a
respiratory absorption coefficient Of 0.50, the benzene intake per individ-
ual at 1 ppm is:
(3.25 mg/m3) (20m3/day) (.5) = 32.5 mg/day
To calculate the benzene intake resulting in a lifetime risk of leukemia of
10 , one solves the following eauation for x,
x - 32,5 mg/day
10"5 0.024074
resulting in 0.0135 mg/day.
The U.S. EPA (Mitre Corp., 1978) total exposure analysis indicates that
the total body exposure may be as high as 1.1 mg/day of benzene. This was
derived using estimates which have varying degrees of support in terms of
hard data. The specific use of the total exposure estimates for calculation
of water criterion does not seem warranted at this particular time because
of a general lack of knowledge about the accuracy of the estimates. It can
be said, however, that from a general weight of evidence perspective, it ap-
pears that air exposure may contribute the majority of total exposure. The
total exposure consideration should be factored into the criterion develop-
ment at a later d-ate when additional data is available.
C-63
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Under the Consent Decree in NRDC v. Train, criteria are to state "rec-
ommended maximum permissible concentrations (including where appropriate,
zero) consistent with the protection of aquatic organisms, human health, and
recreational activities." Benzene is suspected of being a human carcino-
gen. Because there is no recognized safe concentration for a human carcino-
gen, the recommended concentration of benzene in water for maximum protec-
tion of human health is zero.
Because attaining a zero concentration level may be infeasible in some
cases and in order to assist the Agency and states in the possible future
development of water quality regulations, the concentrations of benzene cor-
responding to several incremental lifetime cancer risk levels have been
estimated. A cancer risk level provides an estimate of the additional inci-
dence of cancer that may be expected in an exposed population. A risk of
10 for example, indicates a probability of one additional case of cancer
for every 100,000 people exposed, a risk of 10~6 indicates one additional
case of cancer for every million people exposed, and so forth.
In the Federal Register notice of availability of draft ambient water
quality criteria, EPA stated that it is considering setting criteria at an
interim target risk level of 10" , 10 , and 10 as shown in the
table below.
Exposure Assumptions Risk Levels and Corresponding Criteria (1)
(per day)ug/1
0 1CT7 1CT6 Ipf5
2 liters of drinking water 0 0.066 0.66 6.6
and consumption of 6.5
qrams fish and shellfish. (2)
Consumption of fish and 0 4.0 40.0 400
shellfish only.
C-64
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(1) Calculated by applying a relative risk model for epidemiologic studies,
as described in the Human Health Methodology Appendices to the October
1980 Federal Register notice which announced the availability of this
document, to the human epidemiology data presented in Appendix I.
Since the extrapolation model is linear at low doses, the additional
lifetime risk is directly proportional to the water concentration.
Therefore, water concentrations corresponding to other risk levels can
be derived by multiplying or dividing one of the risk levels and cor-
responding water concentrations shown in the table by factors such as
10, 100, 1,000 and so forth.
(2) Two percent of the benzene exposure results from the consumption of
aauatic organisms which exhibit an average biocorcentration potential
of 5.21-fold. The remaining 98 percent of benzene exposure results
from drinking water.
Concentration levels were derived assuming a lifetime exposure to var-
ious amounts of benzene, (1) occurring from the consumption of both drinking
water and aauatic life grown in waters containing the corresponding benzene
concentrations, and (2) occurring solely from consumption of aquatic life
grown in the waters containing the corresponding benzene concentrations.
For comparison purposes the following risk estimate levels, as derived
from experimental data in Sprague-Dawley rats (Zymbal gland carcinomas in
females at the high dose) (Maltoni and Scarnato, 1979) and based on a modi-
fied "one-hit" extrapolation model as described in Federal Register (44 FR
15926), show remarkable similarities with the risk levels estimated from
human epidemiological data as shown above (Aksoy, 1977; Infante, et al.
1977; Ott, et al. 1978).
C-65
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Exposure Assumptions Risk Levels and Corresponding Criterion
(per day)yg/1
0 KT7 J-0'6 10~5
2 liters of drinking water 0 0.12 1.2 12
and consumption of 6.5 g
fish and shellfish.
Although total exposure information for benzene is discussed and an
estimate of the contributions from other sources of exposure can be made,
this data will not be factored into ambient water quality criteria formula-
tion until additional analysis can be made. The criteria presented, there-
fore, assume an incremental risk from ambient water exposure only.
C-66
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REFERENCES
Abou-el-Marakem, M.M., et al. 1967. Biliary excretion of foreign com-
pounds: benzene and its derivatives in the rat. Biochem. Jour. 105: 1269.
Albert, R. 1978. Carcinogen Assessment Group's final report on the popula-
tion risk to ambient benzene exposures. Sept. 12.
American Conference of Government Industrial Hygienists - Threshold Limit
Values for Chemical Substances and Physical Agents in the Workroom Environ-
ment with Intended Changes for 1979.
Adelstein, A.M. 1972. Occupational mortality: cancer. Ann. Occup. Hyg.
15: 53.
Aksoy, M. 1977. Testimony before Occup. Safety Health Admin. U.S. Oep.
Labor. July, 1977.
Aksoy, M. and S. Erdem. 1969. Some problems of hemoglobin patterns in dif-
ferent thalassemic syndromes showing the heterogeneity of betathalassemic
genes. Ann. of N.Y. Acad. Sci. 165: 13.
Aksoy, M. and S. Erdem. 1978. Follow-up study on the mortality and the de-
velopment of leukemia in 44 pancytopenic patients with chronic exposure to
benzene. Blood. 52: 285.
-------
Aksoy, M., et al. 1966. Osmotic gragility studies in three patients with
aplastic anemia due to chronic benzene poisoning. Blut. 13: 85.
Aksoy, M., et al. 1971. Haematological effects of chronic benzene poison-
ing in 217 workers. Br. Jour. Ind. Med. 28: 296.
Aksoy, M., et al. 1972a. Details of blood changes in 32 patients with pan-
cytopenia associated with long-term exposure to benzene. Brit. Jour. In-
dustr. Med. 29: 56.
Aksoy, M., et al. 1972b. Acute leukemia due to chronic exposure to ben-
zene. Am. Jour. Med. 52: 160.
Aksoy, M., et al. 1974a. Acute leukemia in two generations following
chronic exposure to benzene. Hum. Hered. 24: 70.
Aksoy, M., et al. 1974b. Leukemia in shoe workers exposed chronically to
benzene. Blood. 44: 837.
Aksoy, M,, et al. 1974c. Chronic exposure to benzene as a possible contri-
butory etiological factor in Hodgkin's disease. Blut. 38: 293.
Aksoy, M., et al. 1975a. The Reaction of Normal and Thalassaemic Individ-
uals to Benzene Poisoning: The Diagnostic Significance of Such Studies. In:
Abnormal Haemoglobins and Thalassaemia. Diagnostic Aspects. Academic
Press, Inc., New York.
C-68
-------
Aksoy, M., et al. 1975b. Two rare complications of chronic benzene poison-
ing: Myeloid metaplasia and paroxysmal nocturnal hemoglobinuria. Report of
two cases. Blut. 30: 255.
Aksoy, M., et al. 1976a. Combination of genetic factors and chronic expo-
sure to benzene in the aetiology of leukemia. Hum. Hered. 26: 149.
Aksoy, M., et al. 1976b. Types of leukemia in chronic benzene poisoning.
A study in thirty-four patients. Acta Haematologica. 55: 65.
Amiel, J.L. 1960. Essai negatif d1induction de leucemies chez les souris
par le benzene. Rev. Franc. Etud. Clin. Biol. 5: 198.
Andjelkovic, D., et al. 1976. Mortality experience of a cohort of rubber
workers, 1964-1973. Jour. Occup. Med. 18: 387.
Andjelkovic, D., et al. 1977. Mortality of rubber workers with reference
to work experience. Jour. Occup. Med. 19: 397.
Andrews, L.S., et al. 1977. Effects of toluene on the metabolism, disposi-
tion and hemopoietic toxicity of ^H-benzene. Biochem. Jour. Pharm.
26: 293.
Andrews, L.S., et al. 1979. ^H-8enzene metabolism in rabbit bone mar-
row. Life Sci. 25: 567.
C-69
-------
Angelini, P., et al. 1975. Effect of irradiation on volatile constituents
of stored haddock flesh. Jour. Food Sci. 40: 179.
Appuhn, E. and H. Goldeck. ?"i7. Fruhund spatschaden der blutbildung durch
benzol and seine homologen. Arch. Gewerbepath und Gewerbehygiene. 15: 399.
Baldwin, R.W., et al. 1961. Studies on the carcinogenicity of tricycloqui-
nazoline. A.R. Br. Emp. Cancer Campaign. 39: 414.
Banerjee, B.N. and R.S. Ourloo. 1973. Incidence of teratological anomalies
in control Charles River S-0 strain rats. Toxicology. 1: 151.
Battelle Research Institute. 1977. Sampling in vicinity of benzene produc-
tion and consumption facilities. Preliminary Rep. to Off. Tox. Subst., U.S.
Environ. Prot. Agency. Columbus, Ohio.
Benzene in the Work Environment. 1974. Consideration bearing on the ques-
tion of safe concentrations of benzene in the work environment (MAK-Wert).
Commun. Working Group "Establishment of Mak-Werte" of the Senate Comm. for
the Exam. Hazard. Ind. Mater. Prepared in cooperation with Dr. Gertrud But-
tner. Boppard, Germany, Harold Boldt Verlag.
Berlin, M., et al. 1977. Biologskt Index for Och Kromosomforandringar Nid
Benzene-exposition. Institutinerna for Hygien, Genetic Och Statistik 0
Lunds Universitet, Report 771018.
C-70
-------
Boigetti, B. and M. VassaHo. 1965. Sul rischio di benzolismo nelle faleg-
namerie per 1'uso di collanti sintetici. Lavoro e Medicina. 19: 33.
Boje, H., et al. 1970. Untersuchungen zur leukipoese im Knochenmark der
ratte nach chronischer benzol-inhalation. Blut. 21: 250.
Bousser, j., et al. 1948. Un cas d'hemopathil benzolique tres retardee a
type de lymphosarcome. Arch. Med. Prof. 9: 130.
Bowditch, M. and H.B. Elkins. 1939. Chronic exposure to benzene (benzol).
I. The industrial aspects. Jour. Ind. Hyg. Toxicol. 21: 321.
Brown, S.M. 1975. Letters to the editor: Leukemia and potential benzene
exposure. Jour. Occup. Med. 17: 5.
Browning, £. 1965. Benzene. In: Toxicity and Metabolism of Industrial
Solvents. Elsevier Publishing Co., Amsterdam.
Buday, M., et al. 1971. Benzolmergezes okozta panmyelopathiabol fejlodott
acut myelosis. Orv. Hetil. 112: 2415.
Burdette, W.J. and L.C. Strong. 1941. Comparison of methyl salicylate and
benzene as solvents for methylcholanthrene. Cancer Res. 1: 939.
Buttery, R.G., et al. 1975. Characterization of some volatile constituents
of dry red beans. Jour. Agr. Food Chem. 23: 516.
C-71
-------
Caprotti, M., et al. 1962. Ulcers in the mucous membrane of the colon in
benzene poisoning: Clinical and radiological study. Lavoro Umano. 14: 445.
Cesaro, A.N. 1946. Is percutaneous absorption of benzene possible? Med.
Lavoro. 4: 151.
Chang, I.W. 1972. Study on the threshold limit value of benzene and early
diagnosis of benzene poisoning. Oour. Cath. Med. Coll. 23: 429.
Cleland, J.G. and G.L. Kingsburg. 1977. Multimedia environmental goals for
environmental assessment. EPA 600/7-77-136. U.S. Environ. Prot. Agency,
Washington, D.C.
Cobo, A., et al. 1970. Cytogenetic findings in acquired aplastic anemia.
Acta Haemat. 44: 26.
Conca, G.L. and A. Maltagliati. 1955. Study of the percutaneous absorption
of benzene. Med. Lavoro. 47: 194.
Coombs, M.M. and C.J. Croft. 1966. Carcinogenic derivatives of cyclo-
penta(a)phenanthrene. Nature (London). 210: 1281.
Cornish, H.H. and R.R. Ryan. 1965. Metabolism of benzene in non-fasted,
fasted, and aryl-hydroxylase inhibited rats. Toxicol. Appl. Pharmacol.
7: 767.
C-72
-------
Day, E.A. and D.F. Anderson. 1965. Gas chromatographic and mass spectral
identification of natural components of the aroma fraction of blue cheese.
Jour. Agr. Food Chem. 13: 2.
Day, E.A. and L.M. Libbey. 1964. Cheddar cheese flavor: gas chromato-
graphic and mass spectral analyses of the neutral components of the aroma
fraction. Jour. Food Sci. 29: 583.
Dec, G., et al. 1980. Water solubility and octanol/water partition coef-
ficients of organics: Limitations of the solubility-partition coefficient
correlation. (Manuscript).
DeGowin, R.L. 1963. Benzene exposure and aplastic anemia followed by leu-
kemia 15 years later. Jour. Am. Med. Assoc. 185: 748.
Oeichmann, W.B., et al. 1963. The hemopoietic tissue toxicity of benzene
vapors. Toxicol. Appl. Pharmacol. 5: 201.
Delore, P. and C. Borgomano. 1928. Leucemie aigue an cours de 1'intoxica-
tion benzenique. Sue Torigine toxique de certaines leucemies aigues et
leurs relations avec les anemies graves. Jour. Med. Lyon. 9: 227.
Dobashi, Y. 1974. Effects of benzene and its metabolites on the mitosis of
cultures of human cells. Sangyo Igaku. 16: 453.
Dobrokhotov, V.B. 1972. The mutagenic influence of benzene and toluene
under experimental conditions. Gig. Sanit. 37: 36.
C-73
-------
Doskin, T.A. 1971. Effect of age on the reaction to a combination of hy-
drocarbons. Hygiene and Sanitation. 36: 379.
Drew, R.T., et al. 1974. The Influence of Certain Drugs on the Metabolism
and Toxicity of Benzene. lr±: 0. Braiin (ed.), Symposium on Toxicology of
Benzene and Alky! Benzenes, Industrial Health Foundation, Pittsburgh, p. 17.
Erdogan, G. and M. Aksoy. 1973. Cytogenetic studies in thirteen patients
with pancytopenia and leukemia associated with long-term exposure to ben-
zene. New Istanbul Contrib. Clin. Sci. 10: 230.
Erf, L.A. and C.P. Rhoads. 1939. The hematological effects of benzene
(benzol) poisoning. Jour. Industr. Hyg. Toxicol. 20: 421.
Flath, R.A. and R.R. Forrey. 1970. Volatile components of smooth cayenne
pineapple. Jour. Agric. Food Chem. 18: 306.
Forni, A. and L. Moreo. 1967. Cytogenetic studies in a case of benzene
leukemia. Eur. Jour. Cancer 3: 251.
Form', A. and L. Moreo. 1969. Chromosome studies in a case of benzenein-
duced erythroleukemia. Eur. Jour. Cancer. 5: 459.
Forni, A. and E.G. Vigliani. 1974. Chemical leukemogenesis in man. Ser.
Haemat. 7: 210.
C-74
-------
Forni, A., et al. 1971a. Chromosome studies in workers exposed to benzene
or toluene or both. Arch. Environ. Health. 22: 373.
Forni, A., et al. 1971b. Chromosome changes and their evolution in subject
with past exposure to benzene. Arch. Environ. Health. 23: 385.
Funes-Cravioto, F., et al. 1977. Chromosome aberrations and sisterchro-
matid exchange in workers in chemical laboratories and a rotoprinting fac-
tory, and in children of women laboratory workers. Lancet, p. 322.
Gaultier, M., et al. 1970. Genetic variations in the hemoglobin caused by
the professional environment. Arch. Mai. Prof. 29: 197.
Gerarde, H.U. 1960. Toxicology and Biochemistry of Aromatic Hydrocarbons.
Elsevier Publishing Co., New York.
Girard, R. and L. Revol. 1970. La frequence d'une exposition benzenenique
au cours hemopathies graves. Nouv Revue Fr. Hemat. 10: 477.
Girard, R., et al.. 1966. Lymphose et intoxication benzolique profession-
nelle chronique. Arch. Mai. Prof. 27: 781.
Girard, R., et al. 1967. Etude de la sensibilite aux toxiques industriels
des porteurs de trait tnalessemique (32 sujets soumis a surveillance hemato-
logigue prolongee). Jour. Med. Lyon. 48: 1113.
C-75
-------
Glrard, R., et al. 1968. Les expositions benzeniques meconnues. Leur
recherche systematique au cours des hemopathies graves. Enquete chez 200
hemopathiques hospitalises. Arch. Mai. Prof. 29: 723.
Girard, R., et al. 1970a. Leukocyte alkaline phosphatase and benzene expo-
sure. Med. Lab. 61: 502.
Girard, R., et al. 1970b. Etude de la phosphatase alcaline leucocytaire et
du caryotype des ouvriers exposes au benzene. Arch. Mai. Prof. 31: 31.
Girard, R., et al. 1970c. Hydrocarbures benzeniques et hemopathies
graves. Arch. Mai. Prof. 31: 625.
Girard, R., et al. 1971a. Comments on indemnification for benzene-induced
leukemia and aplasia. Arch. Mai. Prof. 32: 581.
Girard, R., et al. 1971b. Malignant hemopathies and benzene poisoning.
Med. Lav. 62: 71.
Gofmekler, V.A. 1968. Effect in embryonic development of benzene and for-
maldehyde. Hyg. Sanit. 33:-327.
Goldstein, 8.0. 1977a. Introduction (Benzene toxicity: critical review).
Jour. Toxicol. Environ. Health Suppl. 2: 1.
Goldstein, 8.0. 1977b. Hematotoxicity in humans. Jour. Toxicol. Environ.
Health Suppl. 2: 69.
C-76
-------
Goldstein, 8.0. 1977c. Hematotoxicity in Man. ln_: Sidney Laskin and Ber-
nard Goldstein (eds.), Benzene Toxicity, a Critical Evaluation. (In press).
Goldstein, B.D. and S. Laskin (eds.) 1977. Benzene toxicity, a critical
evaluation. Toxicol. Environ. Health Supplement.. 2: 1.
Goldstein, B.D., et al. 1980. Unpublished results.
Goldwater, L.J. 1941. Disturbances in the blood following exposure to ben-
zene (benzol). Jour. Lab. CHn. Med. 26: 957.
Goldwater, L.J. and M.P. Tewksbury. 1941. Recovery following exposure to
benzene (benzol). Jour. Indust. Hyg, 23: 217.
Gonasun, L.M., et al. 1973. Benzene metabolism in mouse liver mlcrosomes.
Toxicol. Appl. Pharmacol. 26: 398.
Green, J.O., et al. 1978. Inhaled benzene fetotoxiclty 1n rats. Toxicol.
Appl. Pharmacol. 46: 9.
Greenburg, L., et al. 1939. Benzene poisoning 1n rotogravure printing.
Jour. Industr. Hyg. Toxicol. 21: 395.
Greene, M.H., et al. 1979. Cancer mortality among printing plant workers.
Environ. Res. 20: 66.
C-77
-------
Guasch, J., et al. 1959. Anemia benzolica complicada con leucemia aguda a
los seis anos de evolucion. Sangre. 4: 129.
Gut, I. 1978. Some Factors Affecting Xenobiotic Metabolism jm vitro, ^n:
J.R. Fouts and I. Gut (eds.) Industrial and Environmental Xenobiotics. Jji
vitro versus j£ vivo Biotransformation and Toxicity. Excerpta Medica,
Amsterdam, p. 74.
Haberlandt, W. and B. Mente. 1971. Deviation in number and structure of
chromosomes in industrial workers to benzene. Zbl. Arbeitsmed. 21: 338.
Hamilton, A. 1931. General review. Benzene (benzol) poisoning. Arch.
Path. 11: 434.
Hammond, J.W. and E.R. Herman. 1960. Industrial hygiene features of a
petrochemical benzene plant design and operation. Am. Ind. Hyg. Assoc.
Jour. 21: 173.
Hansch, C. and A.J. Leo. 1979. Substituent Constants for Correlation Anal-
ysis in Chemistry and Biology. Wiley-Interscience, New York.
Harper, C., et al. 1973. Species differences in benzene hydroxylation to
phenol by pulmonary and hepatic microsomes. Am. Soc. Pharmacol. Exp. Ther.
3: 381.
Harris, R.L. 1977. Testimony before Occupational Safety and Health
Administration. U.S. Dept. of Labor, Washington, O.C. August 8, 1977.
C-78
-------
Hartwich, G. and G. Schwanitz. 1972. Chromosomenuntersuchungen nach chron-
Ischer Benzol-Exposition. Dtsch. Med. Wschr. 97: 45.
Hartwich, G., et al. 1969. Chromosome anomalies in a case of benzene leu-
kemia. Ger. Med. Monthly. 14: 449.
Helmer, «.J. 1944. Accumulated cases of chronic benzene poisoning in the
rubber industry. Acta Medica Scand. 118: 354.
Hernberg, S., et al. 1966. Prognostic aspects of benzene poisoning. Brit.
Jour. Industr. Med. 23: 204.
Hiraki, K., et al. 1963. Development of subcutaneous sarcomas in Swiss
mice given repeated injections of benzene in olive oil. Gann. 54: 427.
Hirokawa, T. and K. Nomiyama. 1962.. Studies on the poisoning by benzene
and its homoloques. Oxidation rate of benzene in the rat liver homogenate.
Med. Jour. Shinsu Univ. 7: 29.
Holvey, D.N. (ed.) 1972. The Merck Manual of Diagnosis and Therapy. Merck
and Co., Rahway, New Jersey.
Howard, P.H. and P.R. Durkin. 1974. Sources of contamination, ambient
levels, and fate of benzene in the environment. EPA 560/5-75-005. U.S.
Environ. Prot. Agency, Washington, D.C.
C-79
-------
Hudak, A. and G. Ungvarx. 1975. Embryotoxic effects of benzene, toluens
and xylene. Toxicology, 11: 55,
Hunter, C.6. 1966. Aromatic solvents. Ann. Occup. Hyg. 9: 191.
Hunter, C.G. 1968. Solvents with reference to studies on the pharmacodyna-
mics of benzene. Proc. R. Soc. Med. 61: 913.
Hunter, D. 1944. Industrial toxicology. Quarterly Jour. Med. 185-250.
Hunter, 0. 1962. The Aromatic Carbon Compounds. |£: The Diseases of Occu-
pations. Little, Brown 3 Co., Boston.
Hutchings, M., et al. 1947. Investigation of benzol and toluol poisoning
in Royal Australian Air Force workshops. Med. Jour. Australia. 2: 681.
Igel, H.J. et al. 1969. Mouse leukemia virus activation by chemical car-
cinogens. Science. 166: 1624.
Ikeda, M. and H. Ohtsuji. 1971. Phenobarbital-induced protection against
toxicity of toluene and benzene in the rat. Toxicol. Appl. Pharmacol.
20: 30.
Ikeda, M., et al. 1972. In vivo suppression of benzene and styrene oxida-
tion by co-administered toluene in rats and effects of phenobarbital. Xeno-
biotica. 2: 101.
C-80
-------
Imamura, N., et al. 1973. Synergistic action of N-nitrosobutyl-urea and
aqathioprine in induction of leukemia in C57BL mice. Gann. 64: 493.
Infante, P.P., et al. 1977a. Leukemia in benzene workers. Lancet. 2: 76.
Infante, P.P., et al. 1977b. Benzene and leukemia. Lancet. 2: 867.
International Agency for Research on Cancer. 1974. IARC monographs on the
evaluation of carcinogenic risk of chemicals to man. Vol. 7: Some antithy-
roid and related substances, nitrofurans and industrial chemicals. Lyon,
France.
International Labour Office. 1968. Benzene: Uses, toxic effects, substi-
tutes. Occup. Safety Health Ser., Geneva.
Irons, R.D., et al. 1980. Benzene is metabolized and covalently found in
bone marrow in situ. Chem. Biol. Interact. (In press).
Ishimaru, T., et al. 1971. Occupational factors in the epidemiology of
leukemia in Hiroshima and Nagasaki. Am. Jour. Epidemiol. 93: 157.
Ito, T. 1962. Study on the sex difference in benzene posioning. Report
1. On the obstacles in benzene workers. Showa Igakkai Zasshi. 22: 268.
Jenkins, L.J., et al. 1970. Long-term inhalation screening studies of
benzene, toluene, o-xylene and cumene on experimental animals. Toxicol.
Appl. Pharmacol. 16: 818.
C-81
-------
Jerina, 0. and J.W. Daly. 1974. Arene oxides: A new aspect of drug meta-
bolism. Science. 185: 573.
Jerina, D., et al. 1968. Role of the arene-oxide-oxepin system in the
metabolism of aromatic substrates. Ijn vitro conversion of benzene oxide to
a premerccapturic acid and a dihydrodiol. Arch. Biochem. Biophys. 128: 176.
Justin-8esancon, I., et al. 1959. Leucoise aigue survenue 27 ans apres ex-
position aux vapeurs benzoliques. La Semaine des Hopitaux. 35: 186.
Kahn, R.R. and Novak, 0. 1973. Variability in AKR mouse leukemia mortal-
ity. Jour. Natl. Cancer Inst. 51: 683.
Kaplan, H.S. 1967. On the natural history of murine leukemias. Cancer
Res. 27: 1325.
Khan, H. and M.H. Khan. 1973. Cytogenetic studies following chronic expo-
sure to benzene. Arch. Toxikol. 31: 39.
Khan, H.A. and V.I. Muzyka. 1970. The effect of benzene on the d-amino-
levulinic acid and prophyrin content in the cerebral cortex and in the
blood. Industrial Hygiene and Profession Associated Disorders. 3: 59.
Khan, H.A. and V.I. Muzyka. 1973. The chronic effect of benzene on porphy-
rin metabolism. Work Environ. Health. 10: 140.
C-82
-------
Kilian, O.J. and R.C. Daniel. 1978. A cytogenetic study of workers exposed
to benzene in the Texas Division of Dow Chemical, U.S.A. Feb. 27, 1978, Dow
Chemical, Freeport, Texas.
Kimmel, C.A. and J.G. Wilson. 1973. Skeletal deviations in rats: Malforma-
tions or variations? Teratology. 8: 309.
Kimura, E.T., et al. 1970. Acute toxicity and limits of solvent residue
for 16 organic solvents. Toxicol. Appl. Pharmacol. 19: 699.
Kinlin, T.E., et al. 1972. Volatile components of roasted filberts. Jour.
Agr. Food Chem. 20: 1021.
Kinoshita, Y., et al. 1965. A case of myelogenous leukemia. Jour. Japan
Haematol. Soc. 1965: 85.
Kirschbaum, A. and L.C. Strong. 1942. Influence of carcinogens on the age
incidence of leukemia in the high leukemia F strain of mice. Cancer Res.
2: 841.
Kissling, M. and B. Speck. 1972. Chromosomal aberrations in experimental
benzene intoxication. Helv. Med. Acta. 36: 59.
Kocsis, J.J., et al. 1968. Dimethyl sulfoxide: Interactions with aromatic
hydrocarbons. Science. 160: 427.
C-83
-------
Koizumi, A., et al. 1974. Cytokinetic and cytogenetic changes In cultured
human leucocytes and HeLa cells Induced by benzene. Ind. Health (Jap.)
12: 23.
Laerum, O.D. 1973. Reticulum cell neoplasms in normal and benzene-treated
hairless mice. Acta. Path. Microbiol. Scand. Sect. A. 81: 57.
Lange, A., et al. 1973a. Serum immunoglobulin levels in workers exposed to
benzene, toluene and xylene. Int. Arch. Arbeitsmed. 31: 37.
Lange, A., et al. 1973b. Leukocyte agglutinins in workers exposed to ben-
zene, toluene, and xylene. Int. Arch. Arbeitsmed. 31: 45.
Lazarew, N.W., et al. 1931. Cutaneous permeability for petroleum ether and
benzene. Arch. F. Hyg. 106: 112.
Li, P.P., et al. 1969. Cancer mortality among chemists. Jour. Natl. Can-
cer Inst. 43: 1159.
Lignac, G.O.E. 1932. Die Benzolleukamie bei Menschen und weissen Mausen,
III. Krankheitsforsch. 9: 426.
Lonneman, W.A., et al. 1968. Aromatic hydrocarbons in the atmosphere of
the Los Angeles basin. Environ. Sci. Technol. 2: 1017.
Lutz, U.K. and C.H. Schlatter. 1977. Mechanism of the carcinogenic action
of benzene: irreversible binding to rat liver DMA. Chem. Biol. Interact.
18: 241.
C-84
-------
Lyapkalo, A.A. 1973. Genetic activity of benzene and toluene. Gig Tr.
Prof. Zabol. 17: 24.
Lyon, J.P. 1975. Mutagem'city studies with benzene. Ph.D. dissertation.
University of California.
Mai lory, T.B., et al. 1939. Chronic exposure to benzene (benzol). III.
The pathological results. Jour. Ind. Hyg. Toxicol. 21: 355t
Maltoni, C. and C. Scarnato. 1979. First experimental demonstration of the
carcinogenic effects of benzene: long-term bioassays on Sprague-Oawley rats
by oral administration. Med. Lav. 70: 352.
Mancuso, T.F. and J.J. Brennan. 1970. Epidenriological considerations of
cancer of the gallbladder, bile ducts, and salivary glands in the rubber in-
dustry. Jour. Occup. Med. 12: 333.
Mancuso, T.F., et al. 1968. An epidemiological approach to the rubber in-
dustry. Jour. Occup. Med. 10: 213.
Marchal, G. 1952. A propos de la communication de R. Andre et B. Dreyfus:
maladle de 01 Guglielmo. Sangre. 23: 682.
Matsushita, T. 1966. Experimental studies on the disturbance of hemato-
poietic organs due to benzene intoxication. Nagova Jour. Med. Sci. 28: 204.
C-85
-------
McMichael, A.J., et al. 1974. An epidemiclogical study of mortality within
a cohort of rubber workers. Oour. Occup. Med. 15: 458.
McMichael, A.J., et al. 1975. Solvent exposure and leukemia among rubber
workers: An epidemiological study. Jour. Occup. Med. 17: 234.
McMichael, A.J., et al. 1976a. Cancer mortality among rubber workers: An
epidemiological study. Ann. N.Y. Acad. Sci. 271: 125.
McMichael, A.J., et al. 1976b. Mortality among rubber workers: relation-
ship to specific jobs. Jour. Occup. Med. 18: 178.
Meigh, O.F., et al. 1972. Growth-inhibitory volatile aromatic compounds
produced by Solanum tuberosum tubers. Phytochemistry. 12: 987.
Miller, J.R. 1962. A strain difference in response to the teratogenic ef-
fect material fasting in the house mouse. Can. Jour. Genetic Cytol. 4: 69.
Mitelman, F., et al. 1979. Relation among occupational exposure to potent-
ial mutagenic/carcinogenic agents, clinical findings, and bone marrow chrom-
osomes in acute nonlymphocytic leukemia. Blood. 52: 1229.
Mitre Corp. 1976. Air pollution assessment of benzene. Contract No. EPA
68-02-1495. U.S. Environ. Prot. Agency, Washington, O.C.
Mitre Corp. 1978. Environmental sources of benzene exposure: source con-
tribution factors. Contract No. EPA 68-01-4635. U.S. Environ. Prot.
Agency, Washington, O.C.
C-S6
-------
Monson, R.R. and K.K. Nakano. 1976a. Mortality among rubber workers. I.
White male union employees in Akron, Ohio. Am. Jour. Epidemiol. 103: 284.
Monson, R.R. and K.K. Nakano. 1976b. Mortality among rubber workers. II.
Other employees. Am. Jour. Epidemiol. 103: 297.
Murray, F.J., et al. 1979. Embryotoxicity of inhaled benzene in mice and
rabbits. Am. Industrial Hygiene Assoc. Jour. 40: 993.
National Academy of Sciences. 1975. Review of the health effects of ben-
zene. Natl. Acad. Sci., Washington, D.C.
National Academy of Sciences. 1976. Health effects of benzene: a review.
Washington, D.C.
National Academy of Sciences. 1977. Drinking water and health. Washing-
ton, D.C.
National Cancer Institute. 1977. On occurrence, metabolism, and toxicity
including reported carcinogem'city of benzene. Summary rep. Washington,
D.C.
National Institute of Occupational Safety and Health. 1974. Criteria for a
recommended standard... Occupational exposure to benzene. U.S. DHEW, Wash-
ington, D.C.
C-87
-------
National Institute of Occupational Safety and Health. 1977. Revised recom-
mendation for an occupational exposure standard for benzene. U.S. DHEVI,
Washington, D.C.
Nawrot, P.S. and R.E. Staples. 1979. Teratology. 19: 41.
Neely, W.B., et al. 1974. Partition coefficient to measure bioconcentra-
tion potential of organic chemicals in fish. Environ. Sci. Technol.
8: 1113.
Nelson, N. 1977. Unpublished research. Letter to U.S. Environ. Prot.
Agency, March 13, 1977.
Nencki, M. and P. Giacosa. 1880. Uber die oxydation die aromatischen
Kohlenwasserstaffe in Turkoyser. 2. Physiol. Chem. 4: 325.
Nomiyama, K. and H. Nomiyama. 1974a. Respiratory retention, uptake and
excretion of organic solvents in man. Int. Arch. Arbertsmed. 32: 75.
Nomiyama, K. and H. Nomiyama. 1974b. Respiratory elimination of organic
solvents in man. Int. Arch. Arbeitsmed. 32: 85.
Nonaka, M., et al. 1967. Gas chromatographic and mass spectral analyses of
cooked chicken meat volatiles. Jour. Agr. Food Chem. 15: 713.
Ott, M.G., et al. 1978. Mortality among individuals occupationally exposed
to benzene. Arch. Environ. Health. 33: 3.
C-88
-------
Pagnotto, L.D., et aU 1961. Industrial benzene exposure from petroleum
naphtha. I. Rubber coating industry. Am. Ind. Hyg. Assoc. Jour. 22: 417.
Palmer, A.K. 1968. Spontaneous malformation on the New Zealand White Rab-
bit: the background to safety evaluation test. Lab. Anim. 2: 195.
Parke, O.V. and R.T. Williams. 1953. Oetoxication. XLIX. Metabolism of
benzene containing (C*4) benzene. Biochem. Jour. 54: 231.
Paterni, L. and V. Sarnari. 1965. Involutional myelopathy due to benzene
poisoning, with the appearance of a mediastinal reticulosarcoma at an ad-
vanced stage. Securitas. 50: 55.
Philip, P. and M.K. Jensen. 1970. Benzene-induced chromosome abnormalities
in rat bone marrow cells. Acta. Pathol. Microbiol. Scand. Sect. A. 78: 489.
Picciano, D. 1978. Communication submitted to Environmental Health Subcom-
mittee, U.S. EPA, May 25.
Pollini, G. and R. Colombi. 1964. Lymphocyte chromosome damage in benzene
blood dyscrasia. Med. Lav. 55: 641.
PoTHni, G., et al. 1964. Relationship between chromosomal alternations
and severity of benzol blood dyscrasia. Med. Lav. 55: 735.
C-39
-------
Porteous, J.W. and R.T. Williams. 1949a. Studies in detoxication. The
metabolism of benzene. The determination of phenol urine with 2:6-dichloro-
quino-nechloroimide. The excretion of phenol glucuronic acid and ethereal
sulphate by rabbits receiving benzene and phenol. Observations on the de-
termination of catechol, quinol, and muconic acid in urine. Biochem. Jour.
44: 46.
Porteous, J.W. and R.T. Williams. 1949b. Studies in detoxication. The
metabolism of benzene. The isolation of phenol, catechol, and quinol and
hydroxy quinol from the ethereal sulphate fraction of the urine of rabbits
receiving benzene orally. Biochem. Jour. 44: 56.
Posner, H.W., et al. 1961. Enzymatic hydroxylation of aromatic compounds.
Further studies of the properties of the microsomal hydroxylating system.
Arch. Biochem. Biophys. 94: 269.
Pushkina, N.W., et al. 1968. Changes in content of ascorbic acid and
nucleic acids produced by benzene and formaldehyde. Bull. Exp. Biol. Med.
66: 868.
Redmond, C.K., et al. 1972. Long-term mortality study of steelworkers.
VI. Mortality from malignant neoplasms among coke oven workers. Jour.
Occup. Med. 14: 621.
Redmond, C.K., et al. 1976. Cancer experience among coke by-product work-
ers. Ann. N.Y. Acad. Sci. 271: 102.
C-90
-------
Revnova, N.V. 1962. Concerning auto-inmunity shifts in chronic occupation-
al benzol poisoning. Gig. Tr. Prof. Zabol. 7: 38.
Rickert, D.E., et al. 1979. Benzene disposition in the rat after exposure
by inhalation. Toxicol. Appl. Pharmacol. 49: 417.
Rondanelli, E.G., et al. 1961. Effects du benzene sur la mitose erythro-
blastique. Investigations a la microcinematographic en confcraste de phase.
Acta Haemat. 26: 281.
Rondanelli, E.G., et al. 1964. Benzene-induced anomalies in mitotic cycle
of living erythroblasts. Sangre. 9: 342.
Roth, L., et al. 1972. Cytologic and immunochemical features of benzenein-
duced reticuloses. Timisoara Med. 17: 29.
Runner, M.M. and J.R. Miller. 1956. Congenital deformity in mouse as a
consequence of fasting. Analytical Res. 124: 437.
Rusch, G.M., et al. 1977. Benzene metabolism. Jour. Toxicol. Environ.
Health Suppl. 2: 23.
Saita, G. 1945. Mielosi aplastica e successiva mielosi leucemica leucopen-
ica, provacate da benzolo. Med. Lavoro. 36: 143.
Saita, G. and M. Oompe. 1947. Sul rischil benzolico nei principal! stabil-
imenti rotocalcograifci di Milano. Med. Lavoro. 38: 269.
C-91
-------
SaHa, 6. and L. Horeo. 1959. Ta las semi a ed emopatie professional!. Nota
Talassemla e benzolismo cronlco. Med. Lavoro. 50: 25.
Saita, G. and L. Moreo. 1961. Haemolytic attack following inhalation of a
single massive dose of benzol. Med. Lavoro. 52: 713.
Saita, 6. and L. Moreo. 1966. A case of chronic benzene poisoning with a
Pelger-Huet type leucocyte anomaly. Med. Lavoro. 57: 331.
Saita, 6. and S. Sbertoli. 1962. L'agglutinogramma nell'intossi-azioue
cronlca da benzolo. Med. Lavoro. 45: 250.
Saita, G. and E.G. Vigliani. 1962. The action of benzene in inducing leu-
kemia. Med. Lavoro. 53: 581.
Saita, 6., et al. 1964. Thromboelastographic investigations in benzene
haemopathy. Med. Lavoro. 55: 655.
Sakamoto, A., et al. 1957. Ring oxidation of benzene. Phenol formation.
Osaka Oaigaku Zasshi. 9: 345.
Sammett, 0., et al. 1979. Partial hepatectomy reduces both metabolism and
toxidty of benzene. Jour. Toxicol. Environ. Health. 5: 785.
Sato, A. 1972. Elimination of inhaled benzene and toluene in man. Jap.
Jour. Industr. Health. 14: 224.
C-92
-------
Sato, A. and T. Nakajima. 1979a. A vial-equilibrium method to evaluate the
drug-metabolizing activity for volatile hydrocarbons. Toxicol. Appl.
Pharmacol. 47: 41.
Sato, A. and T. Nakajima. 1979b. Dose-
-------
Snyder, R., et al. 1977. Bone marrow depressant and leukemogenic actions
of benzene. Life Sci. 21: 1709.
Snyder, R., et al. 1978. Binding of labeled benzene metabolites to mouse
liver and bone marrow. Res. Comm. Chem. Pathol. Pharmacol. 20: 191.
Speck, 8,, et al. 1966. Experimented untersuchungen uber der workungs
mechanismus des benzols auf das knochenmark. Schweizerische Medizinische
Wochenschrift. 38: 1274.
Srbova, J., et al. 1950. Absorption and elimination of inhaled benzene in
man. Arch. Ind. Hyg. 2: 1.
Stephan, C.e. 1980. Memorandum to J. Stara. U.S. EPA. Jul> 3.
Tareeff, E.M., et al. 1963. Benzene leukemias. Acta Un. Int. Contra
Cancru. 19: 751.
Teisinger, J., et al. 1952. The metabolism of benzene in man. Procovni
Lekarstvi. 4: 175.
Teranishi, R., et al. 1963. Volatiles from strawberries. I. Mass spectral
identification of the more volatile components. Jour. Food Sci. 28: 478
Thorpe, J.J. 1974. Epidemiclogical survey of leukemia in persons poten-
tially exposed to benzene. Jour. Occup. Med. 16: 375.
C-95
-------
Timbrell, J.A. and J.R. Mitchell. 1977. Toxi city-related changes in ben-
zene metabolism m>. Xenobiotica. 7: 415.
Torres, A., et al. 1970. Coexistencia de antecadentex benzolicos cronicos
plasmocitoma mutliple. Presencion de dos cases. Sangre. 15: 275.
Tough, I.M. and W.M. Court-Brown. 1965. Chromosome aberrations and expo-
sure to ambient benzene. Lancet. 1: 684.
Tough, I.M., et al. 1970. Chromosome studies on workers exposed to atmos-
pheric benzene. The possible influence of age. Eur. Jour. Cancer. 6: 49.
Tunek, A., et al. 1978. Microsomal metabolism of benzene to species irre-
versibly binding to microsomal protein and effects of modification of this
metabolism. Mol . Pharmacol . 14: 920.
Tunek, A., et al. 1979. Microsomal target proteins of metabolically acti-
vated aromatic hydrocarbons. Chem. Biol. Interactions. 27: 133.
Tyroler, H.A. 1977. Testimony before Occup. Safety Health Admin. U.S.
Dep. Labor, August 8, 1977.
U.S. Department of Health, Education, and Welfare. 1961. Mortality in 1950
by occupation and industry. Vital Statistics - Special Reports. 53: 1.
U.S. EPA. 1975. Preliminary assessment of suspected carcinogens in drink-
ing water. U.S. Environ. Prot. Agency, Washington, O.C.
C-96
-------
U.S. EPA. 1977. Benzene health effects assessment. U.S. Environ. Prot.
Agency, Washington, O.C.
U.S. EPA. 1978a. Estimation of population cancer risk from ambient benzene
exposure. Carcinogen Assessment Group, U.S. Environ. Prot. Agency,
Washington, O.C.
U.S. EPA. 1978b. Assessment of health effects of benzene germane to low-
level exposure. U.S. Environ. Prot. Agency, Washington, D.C.
U.S. EPA. 1980. Seafood consumption Data Analysis Stanford Research
Institute International, Menlo Park, Calif. Final Report, Task 11, Contract
No. 68-01-3887.
Veith, 6.D. 1980. Memorandum to C. Stephan. U.S. EPA. April 14.
Veith, G.D., et al. 1979. Measuring and estimating the bioconcentration
factor of chemicals in fish. Jour. Fish. res. Board Can. 36: 1040.
Vianna, N.O. and A. Polan. 1979. Lymphomas and occupational benzene expo-
sure. Lancet. 1: 1394.
Vigliani, E.C. 1975. Leukemia associated with benzene poisoning. Present-
ed at: Conference on Occupational Carcinogenesis, Abstract 38, March 24-27,
1975.
C-97
-------
Vigllani, E.G. and A.*Forni. 1966. Leucemogenesi professionale. Minerva
Med. 57: 3952.
Vigliani, E.G. and A. Forni. 1969. Benzene, chromosome changes, and leu-
kemia. Jour. Occup. Med. 11: 148.
Vigliani, E.G. and A. Forni. 1976. Benzene and leukemia. Environ. Res.
11: 122.
Vigliani, E.G. and G. Saita. 1943. Leucemia emocitoblastica da benzolo.
Med. Lavoro. 34: 182.
Vigliani, E.C, and G. Saita. 1964. Benzene and leukemia. New England
Jour. Med. 172: 872.
Von Sydow, E. and G. Karlsson. 1971. The aroma of black currants. IV.
The influence of heat measured by instrumental methods. Lebensm. Wiss.
Techn. 4: 54.
Vozovaya, M.A. 1975. Action of low concentrations of benzene, dichloro-
ethane, and their combination on the generative function of animals and the
development of progeny. G. Tr. Prox. Label. 7: 20.
Vozovaya, M.A. 1976. The effect of small concentrations of benzene and
dichloroethane separately and combined on the reproductive function of
animals. G. Sanit. 6: 100.
C-98
-------
Waldradt, J.P., et al. 1971. Volatile components of roasted peanuts.
Jour. Agr. Food Chem. 19: 972.
Ward, J.M., et al. 1975. Long-term effect of benzene in C57BL 6N mice.
Arch. Environ. Health. 30: 22.
Watanabe, G.I. and S. Yoshida. 1970. The tevatogenic effects of benzene in
pregnant mice. Act. Med. Biol. 19: 285.
Wildman, J.M., et al. 1976. Benzene and lead inhibition of rabbit reticu-
locyte heme and protein synthesis: Evidence for additive toxicity of these
two components of commercial gasoline. Res. Comm. Chem. Path. Pharm.
13: 473.
Milkens, W.F. and P.M. Lin. 1970. Gas chromatographic and mass spectral
analyses of soybean milk volatiles. Jour. Agric. Food Chem. 18: 333.
Wilson, R.H. 1942. Benzene poisoning in industry. Jour. Lab. Clin. Med.
27: 1517.
Winek, C.L. and W.D. Collom. 1971. Benzene and toluene fatalities. Jour.
Occup. Med. 13: 259.
Wolf, M.A., et al. 1956. Toxicologica] studies of certain alkylated ben-
zenes and benzene. Arch. Ind. Health. 14: 387.
C-99
-------
Wolman, S.R. 1977. Cytologlc and cytogenetlc effects of benzene. Toxicol.
Environ. Health Supplement. 2: 63.
Wong, N.P., et al. 1967. Decomposition and filth in foods. Investigation
of volatile components in cod fish by gas chroma tog raphy and mass spectro-
scopy. Jour. Assoc. Off. Anal. Chem. 50: 8.
Yant, M.A., et al. 1936. Urine sulfate determination as a measure of ben-
zene exposure. Jour. Ind. Hyg. Toxicol. 18: 69.
Young, R.J., et al. 1978. Benzene in consumer products. Science.
199: 248.
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Appendix
Derivation of Criterion for Benzene
Three epidemiology studies of workers exposed to benzene vapors on
their jobs, performed by Infante, Ott, and Aksoy, were reviewed by the CAG
for the Office of Air Quality Planning and Standards (Albert, 1978). Their
result was that the potency for humans breathing benzene continuously is B »
0.02407. This means that the lifetime risk of getting leukemia, R, equals
0.024074 time? the lifetime average continuous exposure, X, measured as ppm
of benzene by volume in air, or R = B X. Therefore the air concentration,
X, resulting in a risk of 10~5 is X = R/B = 10~5/.024074 = 4.1539 x
10"4 ppm.
Since the air concentration corresponding to 1 ppm of benzene is 3.25
mg/m and assuming a respiratory rate of 20 m /day and a respiratory
absorption coefficient of 0.50, the daily intake that would result in a risk
of 10~5 is:
4.154 x 10"4 ppm x 3.25 x 103 wg/m3 per ppm x
20 mj/day x 0,5 = 13.5 ug/day
If it is assumed that the fraction of benzene absorbed is the same
between inhalation and ingestion of water and fish, a daily benzene intake
of 13.5 ug through drinking water and fish alone would also cause a leukemia
risk of 10 . The water concentration given this intake is:
C = (13.5 Pg/day)/(2 + 5.21 x 0.0065)
= 6.64 wg/1
= 6.6 yg/1
•U.S. oovfEwarr PHIKTIHO OFKCE: 1980-0-720-016/4370
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