THE ENVIRONMENTAL FATE
OF SELECTED POLYNUCLEAR
AROMATIC HYDROCARBONS
. FEBRUARY 1976
FINAL REPORT
TASK TWO
OFFICE OF TOXIC SUBSTANCES
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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THE ENVIRONMENTAL FATE OF
SELECTED POLYNUCLEAR AROMATIC HYDROCARBONS
by
S. B. Radding, T. Mill, C. W. Gould, D. H. Liu,
H. L. Johnson, D. C. Bomberger, and C. V. Fojo
Contract No. 68-01-2681
Project Officer
Carter Schuth
Prepared for
Environmental Protection Agency
Washington, D. C. 20460
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This report has been reviewed by the Office of Toxic Substances,
EPA, and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation for
use.
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ABSTRACT
A review of the recent literature on polynuclear (polycyclic)
aromatic hydrocarbons (PAH) has been carried out by SRI for general
information on PAH and specific details about six selected PAH. The
sources, transport, chemical and physical transformations, structure-
reactivity relationships, and biological (non-carcinogenic) properties
have been reviewed with recommendations for further research.
This review covers the literature through June 1975 with a few
later references.
111
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CONTENTS
ABSTRACT ill
LIST OF TABLES vi
I INTRODUCTION 1
II SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
Summary and Conclusions 4
Recommendations 16
III LITERATURE SEARCH 18
Sources and Subject Area 18
Results 18
IV REVIEW AND EVALUATION OF LITERATURE 19
Formation and Degradation of PAH Under Environmental
Conditions 19
Physical Properties and Transport 19
Spectra 22
Formation of PAH 24
Chemical Degradation of PAH 26
Rates of and Mechanisms of Degradation in Water . . 27
Reactions with Chlorine and Ozone 38
Degradation of PAH in Air 39
Toxicity, Bioaccumulation, and Biodegradation 44
Toxicity 44
Algae 44
Higher Plants 46
Bacteria 47
Invertebrates 48
Fish and Amphibians 49
Birds 52
Mammals 52
Bioaccumulation and Biodegradation 54
Bacteria 55
Higher Plants 58
Aquatic Organisms 59
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Biodegradation Products 60
Birds and Mammals 61
Biosynthesis ..... 62
Biological Activity 63
Biological Effects 64
Adsorption, Distribution, and Binding 65
Physio-Chemical Correlates of Activity 66
Metabolism and Biological Mechanisms 66
Structure-Activity Relationships 68
Environmental Sources 70
Air 70
Water 71
Soils 76
Natural Sources 79
Plants 80
Foods 80
Fossil Fuels and By-Products 83
Anthropogenic Emissions and Effluents 87
Stationary 87
BIBLIOGRAPHY 95
VI
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TABLES
V
1 Names and Synonums for Six PAH 2
2 Environmental Data for Selected PAH 5
3 Relative Rates and Half-Lives for Degradation
of PAH by Environmental Oxidizers 11
4 Partition Coefficients of Polycyclic Hydrocarbons
in a Hexane-Monoethanolammonium Deoxycholate System
and the Approximate Carcinogenic Activities 13
5 Physical Properties of Six PAH 14
6 Vapor Pressure and Vapor Concentration of Selected
PAH at 25°C 20
7 Spectral Properties of Six PAH 23
8 Concentrations of PAH in Air, Water, Soil . 25
9 Absolute Rate Constants and Half-Lives for Reaction
of RO2- Radical with PAH at 60°C . 29
10 Relative and Absolute Reactivity of PAH
Toward Singlet Oxygen 32
11 Photooxygenation of Benzo(a)pyrene (BaP)
and Benz(a)anthracene (BaA) in Water at 25°C 34
12 Temperature Dependence for Photooxygenation
of Benzpyrene on CaCOg . 36
13 Rate Constants for Reaction of PAH with Ozone
in Water at 25°C . 40
14 Half-Lives for Reactions of PAH with Ozone
in the Gas Phase 42
15 Acute Toxicity of Phenanthraquinone
to Bluegreen Algae 45
16 Variations in PAH Concentrations with Seasons 72
17 Variations of PAH Concentrations with Traffic 73
18 PAH Concentrations in Terms of Total Organic
Atmospheric Particulates 74
vii
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19 Carcinogenic PAH Concentrations in Water Sources 75
20 PAH Concentrations in Water 77
21 Concentrations of PAH in Soils 78
22 PAH Concentrations in Cereals and Tubers 81
23 PAH Concentrations in Vegetables and Fruits 82
24 PAH Concentrations in Cooked, Smoked,
and Processed Foods 84
25 PAH Concentrations in Beverages 85
26 Fossil Fuel and its Derivatives 86
27 Heat Generation in a Coal-Fired Installation 88
28 Concentrations of PAH for Various
Industrial Processes 90
29 BaP Emissions from Incinerators and Open Burning 91
30 Comparison of PAH Levels in Incineration
and Open Burning 93
31 PAH in Exhaust Gas from Diesel
and Gasoline Engines 94
viii
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I INTRODUCTION
The Office of Toxic Substances (OTS) , U.S. Environmental Protection
Agency (EPA) under Contract No. 68-01-2681 requested that a literature
search and evaluation of the results be undertaken for the following six
polynuclear aromatic hydrocarbons (PAH): anthracene, benz(a)anthracene,
benzo(a)pyrene, chrysene, 3-methylcholanthrene, and phenanthrene.
These six PAH are exemplary of the range of physical, chemical, and
biological properties encountered among the several hundred known PAH.
Since many, if not most, laboratory studies have involved two or more
PAH, and naturally occurring PAH are usually complex mixtures containing
up to several thousand compounds, as a practical matter we have organized
this review by properties and reactivity rather than by individual com-
pounds. Within each category, however, we have, whenever possible,
emphasized specific structural features and structure-reactivity rela-
tionships. In many cases, comparisons among PAH involve compounds other
than the six selected for this review and, where useful for our purposes,
we have included them in our tabulations and discussion.
Since chemical nomenclature has undergone many (and often extreme)
revisions in the last few years, Table 1 lists the common names of the
PAH being studied, synonyms, and names used in current (1975) chemical
literature.
Much of the information on the toxicity, accumulation, and degra-
dation of polycyclic (polynuclear) aromatic hydrocarbons in the biolo-
gical systems has been discussed and summarized in a comprehensive report
published by the National Academy of Sciences (1972). This report
attempts to provide supplementary information on the environmental fate
-------
Table 1
NAMES AND SYNONYMS FOR SIX PAH
Common Name
Benzo(a)pyrene
Benzo(a)anthracene
Methylcholanthrene
- CH
Synonyms
3 ,4-Benzpyrene
BP
BaP
3 ,4-Benzopyrene
1,2-Benzanthracene
Benzanthrene
Benzo(b)phenanthrene
2 ,3-Benzophenanthrene
Tetraphene
1,2-Benz(a)anthracene
Cholanthrene, 3-methyl-
20-MC
MC
3-MC
20-Methylcholanthrene
3-Methylcholanthrene
1975 C. A. Nomenclature & No.
Benzo[a]pyrene
50-32-8
Benzo[a]anthracene
56-55-3
Benz[j]aceanthrylene,
1,2-Dihydro-3-methyl-
56-49-5
Chrysene
1,2-Benzphenanthrene
Chrysene
218-01-9
Anthracene
Paranaphthalene
Anthracene
120-12-7
Phenanthrene
None
Phenanth rene
85-01-8
-------
and ecological effects of selected PAH. Carcinogenicity of the compounds
has been specifically deleted. The reader is advised to see IARC Mono-
graph, Volume 3.
For this study, OTS hopes to find answers to questions such as:
(1) Do tricyclic, tetracyclic, and pentacyclic aromatics
react in the same way in the biosphere, and what is
the principal mode of degradation?
(2) How does the degree of alkylation of the ring compound
influence the mode of degradation?
(3) What are the degradation products, and are the fate and
effects of these compounds known?
(4) How far up the food chain does bioaccumulation occur?
(5) How widespread is the metabolism of these compounds?
Are they metabolized only by specialized organisms?
Are only the non-alkylated compounds metabolized?
(6) Are the physical properties (solubility, volatility, etc.)
such that they favor the conditions leading to degradation
of these compounds?
The principal contributors to this report by area are:
Literature Search
Physical and Chemical Transformations
Toxicology and Biosynthesis
Structure-Reactivity Relation
Sources
S. B. Radding
T. Mill
C. W. Gould
D. H. Liu
H . L, Johnson
D, G. Bomberger
C. V. Fojo
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II SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
Summary and Conclusions
Table 2 summarizes our findings. Many simple, naturally occurring
organic compounds can be readily pyrolyzed to complex mixtures of PAH
at temperatures above 300 , with maximum yields at 700-900 C. Newer
analytical techniques indicate that PAH found in the environment can be
extremely complex mixtures containing up to several thousand components,
including many alkylated PAH. Although PAH from natural combustion
sources may differ significantly in structure from PAH from anthropogenic
sources, as has been claimed, the evidence for this distinction appears
to be equivocal; much more extensive data would seem to be required to
decide the issue.
PAH are widely distributed in the environment. They are found in
living animal and plant tissue, sediments, soils, air, and surface waters.
Most PAH probably arise as pyrolysis products formed during combustion or
heating of fossil fuels and of most natural products. The compounds may
be natural products of animal and vegetable metabolisms, and are probably
released from exposed fossil fuel deposits by erosion. PAH are essentially
not soluble in water and have low vapor pressures, so that the major
environmental transport mode is as particulate in air or water. However,
comparison of PAH levels in plant and animal tissue suggests that concen-
tration effects are not large despite large partition coefficients
reflecting high solubility in fatty tissues. Presently used methods of
analysis for estimating airborne concentrations of PAH may seriously
underestimate the concentrations of some relatively volatile PAH such as
pyrene, anthracene and benzo(a)anthracene.
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Table 2
ENVIRONMENTAL DATA FOR SELECTED PAH
Physical Properties
Vapor Pressure
Vaporization Rate
Adsorption
Solubility
UV Spectra
Partition Coefficient
Chemical Reactivity
R02 Radical
Singlet 02
0 and Cl
HO Radical
Peracids
NO. and SO.
x 2
Sources
Natural Fires
Coal Combustion
Incineration
Fuel Combustion
Industrial Processes
Seasonal
Forms
Anthracene
4
3
1
1
3
4
3
4
3
3
4
1
4
2
2
2
2
2
1
1
3
Benz(a)-
anthracene
4
3
1
1
2
4
3
3
1
3
3
1
' 1
1
2
3
3
3
1
3
3
Benzo(a)—
pyrene
4
3
1
1
2
4
3
3
3
3
3
1
1
2
2
3
3
3
3
3
3
Chrysene
4
1
1
1
1
4
3
2
1
1
2
1
1
0
2
2
2
3
1
3
1
3-Methyl-
cholanthrene
3
1
1
1
1
4
3
1
1
1
1
0
0
0
2
2
2
2
1
1
1
Phenanthrene
4
3
1
1
3
4
3
4
3
2
3
1
4
1
2
2
2
2
1
1
3
Other PAH, Comments
All PAH have low vapor pressure and
strong absorptivity to minerals and
carbon; low solubility in water; all
strongly absorb light in solar
region and dissolve in fatty sol-
vents. Some data on 30 PAH.
Most PAH react rapidly with 02 by
self sensitized process to form
quinones and other products.
Ozone (or HO) will also oxidize
PAH quickly. Alkylation acceler-
ates these reactions but little
specific data. Data on oxidation
of 13 PAH. Quantitative estimates
of half-lives for all PAH give
5 ± 5 hrs in environment.
Both natural and anthropogenic
combustion sources are major pro-
ducers of many PAH. No firm basis
exists for distinguishing the source
based on structure of PAH. B(a)P
most often used as a measure of
occurrence of other PAH.
Report
Page Reference
12
II
20
17
17,19
21
!!>!!
3,24
2S-.27
22-30,31,^2,^3
34,41
36-38,40,41
39
42
41,42
22
86,87
90,92
93
88,89
70,71
17,19,86
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Anthracene
Table 2
(Continued)
ENVIRONMENTAL DATA FOR SELECTED PAH
Benz(a)- Benzo(a)- 3-Methyl-
anthracene pyrene Chrysene cholanthrene Phenanthrene Other PAH, Comments
Report
Page Reference
Anthracene
Bioac cumulation
Bacteria
Algae
Higher Plants
Invertebrates
Fish
Amphibians
Reptiles
Birds
Mammals
Biodegradation/Metabolism
Bacteria
Algae
Higher Plants
Invertebrates
Fish
Amphibians
Reptiles
Birds
Mammals
2
0
2
0
0
0
0
0
0
3
0
0
0
0
0
0
0
-
Benz(a)-
anthracene
2
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-
Benzo(a)-
pyrene Chrys
4
2
4
4
2
0
0
3
3
0
0
0
0
0
0
0
0
-
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-
9,10-dimethyl-1,2-benzanthracene,
1,2,5,6-dibenzanthracene, 1,2-benz-
anthracene, 1,2-benzopyrene, pyrene,
1,12-benzperylene, perylene. See
list on p. 55. (2)a
Perylene. (2)a
See list on p. 57. (2)a
Perylene. (2)a
1,2,3-dibenzanthracene, 1,2-benz-
pyrene. (3)a
11,54,55
57
56
57,58
li
59
60,61
Report contains general discussion
without specifying compounds.
60
-------
00
Table 2
(Continued)
ENVIRONMENTAL DATA FOR SELECTED PAH
Occurrence/Variation
Air
Water
Soil
Season
Geography
Plants/Food
Animals/Food.
Fuels
Toxicity
Bacteria
Algae
Anthracene
1
2
1
1
2
2
2
2
2
0
Benz(a)-
anthracene
3
3
3
3
3
4
3
3
2
3
Benzo(a)-
pyrene
3
3
3
3
3
4
3
3
3
3
Chrysene
3
3
3
3
3
4
3
3
2
0
3-Methyl-
cholanthrene
1
2
1
1
2
2
2
2
2
0
Phenanthrene
1
2
1
1
2
2
2
2
2
0
Other PAH, Comments
All PAH are found in all biomes and
regions with some seasonal and geo-
graphical variation owing to varia-
tion in space heating and industrial
distribution. Fossil fuel processing
is single most important anthropogenic
See p. 45-46 for list of other PAH cpds
Phenanthraquinone, f luoranthene,
Report
Page Reference
22,70,72
23,74-76
23,77
70-71
70 7?
/ \J , / £.
78,80-84
83
85
45,46
43,44
Higher Plants
Invertebrates
Fish
Amphibians
Reptiles
Birds
Mammals
3
0
0
0
3
0
0
0
0
3
3
4
0
3
4
3
0
0
0
0
3
3
0
2
3
3
0
0
0
0
1,12-benzoperylene, 3,4-benzofluoran-
thene, indeno(l,2,3,cd)pyrene,
1,2,5,6-dibenzanthracene; (4)a
Acridine, fluoranthene, 9-methylanthra- 44
cene, 9,10-dihydroanthracene, 2-methyl-
anthracene, 1,12-benzoperylene, 3,4-benzo-
fluoranthene, indeno(1.2)3,cd)pyrene,
1,2,5,6-dibenzanthracene; (2)a
DimethyIbenzanthracene, 2,7-diamino- 46,47
fluorene, N-fluoren-2-yl-acetamide; (2)a
Phenanthroquinone, with a rating of 3. 47,48
Dibenz(ah)anthracene, 1,2,5,6-dibenz- 48,49
anthracene; (3)a
9,10-dimethyl-l,2-benzanthracene,
1,2-benzopyrene. Primarily bio-
chemical effects. (3)a
50
50,5.1,52
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Anthracene
d
Biosynthesis
Bacteria
Algae
Higher Plants
Invertebrates
Fish
Amphibians
Reptiles
Birds
Mammals
Behavior in
Biological Systems
Adsorption/Distribution
Binding
Physico-Chemical Activity
Metabolic Activity
Structure- Activity
—
0
. 2
0
0
0
0
0
0
2
1
2
• 2
2
Benz(a)-
anthracene
—
0
2
0
0
0
0
0
0
2
3
2
4
4
Table 2
(Continued)
ENVIRONMENTAL DATA FOR SELECTED PAH
Benzo(a)- 3-Methyl- Report
pyrene Chrysene cholanthrene Phenanthrene Other PAH, Comments Page Reference
—
0
3
0
0
0
0
0
0
3
4
2
4 .
3
—
0
0
0
0
0
0
0
0
2
1
2
2
3
—
0
0
0
0
0
0
0
0
2
2
2
3
3
—
0
0
0
0
0
0
0
0
2
1
2
3
2
Specific PAH compounds not mentioned 62
in report. However, there is evidence
that bacteria can synthesize PAH
compounds .
Fluoranthene, 3,4-benzf luoranthene, 61
indino(l , 2,3, cd) pyrene, 1 , 2-benzperylene,
pyrene, coronene, perylene, benzo(e)-
pyrene. (2)a
63
64
Primarily general relationships. 65
Data on alkyl PAH. 66
Data are available on several 67-69
alkylated PAH including these six PAH.
Code: 0 = no information, no inference possible; 1 = inference possible; 2 = minimal information; 3 = reliable data; 4 = reliable and extensive data.
Report pages shown; where underlined indicates quantitative data.
No data found for plants or animals.
No data found for animals.
-------
Regardless of natural PAH background levels and production mechanisms,
it seems clear that industrial activity has increased the level present in
the environment. PAH production is associated with automobile traffic
(probably due to gasoline combustion, wearing of tires, and abrasion of
asphalt surfaces), petrochemical manufacture, and fossil fuel combustion.
PAH levels in urban situations are 10 to 100 times the levels found in
remote areas. PAH levels in urban water supplies often exceed the level
considered safe for human consumption.
Transport of PAH from water to air may be important in well-mixed
water systems through distillation. In water and soil PAH occur almost
completely as the absorbed state on minerals or organic particulate. In
the air some PAH may be found in the vapor phase although most must be
absorbed on particulate matter. In polluted rivers it is possible that
PAH may be solubilized by micelles made up of lipids, biopeptides and
alkaloids, but the relative importance of this mechanism in the total
transport of PAH is unknown.
Chemical degradation of PAH in the environment can take place through
a variety of oxidation reactions to give quinones as major primary products,
with lesser amounts of diols, peroxides, and ring cleavage products. Some
of these degradation products are more resistant to degradation than are
the parent PAH, but their carcinogenic activity is generally much less
than that of the parent PAH.
Some data are now available from which quantitative or semi-quanti-
tative estimates may be made of half-lives of selected PAH in specific
oxidation reactions. The major effect of structure on reactivity is
increased reactivity of alkyl PAH toward electrophilic agents such as
RO • radical, singlet oxygen, and ozone. Where data are available they
point to reactivity factors (differences) as large as one hundred for
alkyl PAH compared with the parent PAH. Chemical reactivity of PAH
toward electrophilic agents seems to increase also with increasing numbers
10
-------
.of rings, but too few data are available on which to base any firm conclu-
sions in this report.
Estimates of half-lives of selected PAH in reactions with RO • radical,
singlet oxygen,ozone, chlorine, and HO* radical, the major environmental
oxidizers, are summarized in Table 3. These data point to photooxygenation
by singlet oxygen as being the dominant chemical process for degradation in
water and probably also in air where reactions with HO* radical and ozone
are also rapid. In the presence of both ozone and light, half-lives of a
few minutes to a few hours may be expected for most PAH. In subsurface
soil, microbial degradation is the major pathway for degradation and under
anaerobic conditions no degradation of PAH occurs. In combustion processes
where most PAH are probably formed, some degradation can also occur by re-
actions with nitrogen oxides and sulfur dioxide near the combustion zone.
Only a few studies have been conducted to assess the biological
effects of polycyclic aromatic hydrocarbons other than those that relate
to carcinogenicity, mutagenicity, or teratogenicity. These studies,
however, indicate that these compounds can be acutely toxic to a variety
of organisms throughout the phylogenetic scale and can produce a variety
of sublethal effects. These effects, however, do not appear related in
terms of degree or type to the number of rings, number of ring substi-
tuents , or their position, or the arrangement of the rings within the
molecule.
Uptake of polycyclic aromatic hydrocarbons has been demonstrated in
many types of microorganisms, plants, invertebrates, and vertebrates.
In general, microorganisms, plants, and invertebrates tend to accumulate
PAH compounds to a greater degree than vertebrates. The degree of
accumulation appears to be related to the ability of the organism to
metabolize PAH compounds; however, the relationship is clouded by
evidence that some organisms may synthesize certain PAH compounds.
11
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Table 3
RELATIVE RATES AND HALF-LIVES FOR DEGRADATION OF PAH BY ENVIRONMENTAL OXIDIZERS
PAH
R0_
1-0
Anthracene
Dimethylanthracene
Diphenylanthracene
Phenanthrene
Pyrene
Perylene
Tetracene
Benzopyrene
Benzanthracene
Dimethylbenzanthracene
Dibenzanthracene
Dimethyldibenzanthracene
Rubrene
1, 38,000
-4 8
2-10 ,2-10
p_, (Water) 0 (Air)'
Oxygen o o
Cl.
HO-
1, 5
100, .05
8, 0.6
1.5, 0.68 1.5, 560
0.12, 2.4-10
1, 38,000
400, 96 XL <5
0.12, 2.4-105 1, 5
2, 10
>1, <5
2.5, 0.42 2.5, 340
>1, <5 >6.2, 0.17 >6.2,
-------
This often makes it difficult to determine whether the levels found in
organisms are of exogenous or endogenous origin.
Aquatic algae and invertebrates tend to concentrate PAH compounds.
In areas where measurable amounts of these compounds have been found in
the water, the concentration of the compounds in algae and invertebrates
has been found to exceed that of the water by at least 200 times. Con-
centrations in terrestrial plants usually parallel that in the soil;
however, plant levels are usually lower than soil levels.
No relationship appears to exist between the molecular structure or
the number of benzene rings of PAH compounds and their propensity for
accumulation. A similar lack of relationship is found for structures of
PAH and their partition coefficients (Tables 4 and 5). However, the data
in Table 4 have been interpreted to mean that those PAH with the highest
carcinogenicity also exhibit the highest solubility in aqueous soaps.
Biodegradation of polycyclic aromatic hydrocarbons has been demon-
strated in microorganisms, fish, birds, and mammals. The aryl hydrocarbon
hydroxylase enzyme system concerned in the metabolism of PAH compounds
seems to be the same in all organisms. Although metabolism of these com-
pounds by plants and invertebrate animals has not been demonstrated, it
is likely that metabolism does occur.
The rate of degradation of PAH compounds by microorganisms to
mammalian systems is relatively low. Bacteria found in soil or water
containing PAH compounds tend to metabolize these compounds at a much
faster rate than those that come from relatively noncontaminated areas.
Unlike chemical degradation, susceptibility of PAH compounds to
biodegradation does not appear related to structure or number of rings.
Non-adapted sewage sludge microorganisms readily attack phenanthrene,
but metabolize anthracene, another tricyclic compound, to a limited
extent. Of the tetracyclic compounds, 9,10-dimethylbenzanthracene is
much more susceptible to oxidation than 1,2-benzanthracene and 9,10-
dimethyl-1,2-benzanthracene.
13
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Table 4
PARTITION COEFFICIENTS OF POLYCYCLIC HYDROCARBONS
IN A HEXANE-MONOETHANOLAMMONIUM DEOXYCHOLATE SYSTEM
AND THE APPROXIMATE CARCINOGENIC ACTIVITIES8
Partition Approximate
Compound coefficient carcinogenic activity
20-Methylcholanthrene 5.8
Benzoperylene 5.7
1,2 ,4 ,5-Dibenzopyrene 6.8
1,2 ,5 ,6-Dibenzanthracene 6.9
3,4-Benzopyrene 7.9
2,3-Benzofluorene 8.4
10-Methyl-l,2-benzanthracene 8.7
1-Methylphenanthrene 10.1 —
1,2-Benzanthracene 10.1 +
10,11-Benzofluoranthene 10.2 +4
Chrysene 10.4 +?
l-Methyl-3,4-benzophenanthrene 10.9 +^
Pyrene 11.5 0
Fluoranthene 12,2 0
1-Methylpyrene 12.3 -
Anthanthrene 12.5 0
Retene 12.7 0
2-Methylanthracene 13.6 0
7-Methyl-3,4-benzophenanthrene 14.4 +
3'-Methyl-1,2-benzanthracene 14.5 0
3-Methylpyrene 14.6 —
Naphthacene 14.7 0
4-Methylpyrene 14.9 0
Phenanthrene 16.4 0
Anthracene 16.9 0
2-Methylfluorene 17.9 -
Fluorene 18.7 0
Naphthalene 24.4 0
Q
In part from R.R. Demisch and G.F. Wright, Can. J. Biochem. Physiol.
41, 1655(1963). "-" designates compounds not tested for carcinogenicity,
The partition coefficient represents the ratio of concentration in the
hexane phase over that in the deoxycholate phase, determined spectro-
photometrically.
Source: Chemical Induction of Cancer, Vol. IIA, J.C. Arcos and M.F.
Argus, Academic Press, N.Y. 1974.
14
-------
Table 5
PHYSICAL PROPERTIES OF SIX PAH
Mol.
PAH Formula
Mol.
Wt.
M.P.
°C
B.P.
°C/torr
Log
Partition
Coefficient1
Benzo(a)pyrene
C H 252.30 179 311/10
6.04
b b
Benzo(a)anthracene C _H 228.28 160 400/760
18 12
5.61
Methylcholanthrene C0,H-,G 268.34 179 NA
A J. J- O
5.83
Chrysene
C H 228.28 256 448/760
5.61
Anthracene
C H 178.23 216 340/760
14 10
4.45
Phenanthrene
C H 178.23 101 340/760
14 10
4.46
Partition Coefficient = [PAH] , /[PAH]
L Jl-OctanolX L JH O
IARC 1973
Hansch 1975
Fieser 1935
Handbook of Chemistry & Physics 1964
Leo 1971
15
-------
In mammals and birds, studies on degradation have been limited to
3,4-benzopyrene and 3-methylcholanthrene; hence, the relationship between
compound structure and metabolism in these animals cannot be evaluated.
Microorganisms are capable of completely assimilating PAH compounds
and appear to utilize them as a carbon source. Mammals, on the other
hand, oxidize these compounds to the epoxides or hydroxylate them and
eliminate these metabolites via the urine and feces. Some epoxides and
hydroxylated derivatives of PAH compounds are carcinogenic or mutagenic,
but less so than the parent compounds. Although the hydroxylated deriv-
atives have been isolated from bacteria, it is not known whether bacteria
form epoxides. The biological activity of metabolites other than the
epoxides and hydroxylated compounds is not well defined.
Our review of the literature on PAH compounds in terms of toxicity,
bioaccumulation, and biodegradation has revealed that relatively little
is known about these compounds—particularly in lower forms of life.
Few experimental investigations have been performed.
Among unsubstituted 3-5 ring PAH, physical properties, absorption,
distribution, binding to protein and nucleic acid and metabolic trans-
formations are relatively similar. Differences in diverse biological
effects relate frequently to differences in carcinogenicity. Table 4
gives some partition coefficients and carcinogenic activities for
selected PAH. All of the compounds are readily absorbed by biological
systems due to their high lipid solubility and aqueous solubilization
by lipids and macromolecules. High lipid solubility insures efficient
microsomal metabolism, which produces both reactive, cytotoxic inter-
mediates and inactive polar metabolites, which are rapidly eliminated.
High lipid solubility also determines efficient uptake and prolonged
storage in fat deposits, thus providing a reservoir for continuous
release and metabolism over a prolonged period. This results in pro-
longed, constant exposure to multiple PAH with enzyme induction and com-
petitive interactions, which may be protective or synergistic with regard
to chronic toxicity.
16
-------
Structure-activity relationships remain poorly defined but are
related primarily to geometry, positional electron density, and re-
activity, which determine metabolic transformations that result in
reactive intermediates that are either rapidly metabolized further and
eliminated or function as tissue alkylating and intercalating cytotoxins.
Some, but not all, alkyl derivatives of PAH are more potent carcinogens
and mutagens than the unsubstituted hydrocarbons. The preponderance of
studies center on benzanthracene, benzopyrene and, to a lesser extent,
methylcholanthrene.
Recommendations
Direct analyses for vapor concentrations of PAH and for the propor-
tion of PAH in the vapor phase and on particulates are needed. Measure-
ments of this kind should be carried out along combustion plumes as a
function of distance from the source, particle size distribution, and
plume temperature.
Distillation of PAH from water to air should be evaluated for several
PAH, as should transfer mechanisms to and from water and soil.
Most chemical studies have examined only a few PAH by themselves
under laboratory conditions; much more emphasis should be placed on
studies of the rates of degradation of selected mixtures of PAH under
environmentally useful conditions.
Structure-reactivity studies on PAH are needed, with particular
emphasis on effects of alkyl substituents and ring members on reactivity
under conditions where the useful kinetic data can be obtained. Cooxi-
dations of these PAH in mixtures should be part of such studies.
Although PAH compounds are taken up and accumulated by many organisms,
we do not know if consumer organisms, particularly the primary consumers,
take up these compounds directly from the environment or through the food
chain.
17
-------
Metabolism of PAH compounds has been established in microorganisms
and the higher vertebrates, but so far, not in invertebrates. Compara-
tive metabolism studies could be helpful in understanding the mechanism
of PAH biodegradation as well as the environmental fate of these compounds,
There appears to be little information on the acute toxicity of PAH
compounds to aquatic organisms. Although most of these compounds have
limited water solubility, it has been demonstrated that as little as 40
p,g/l of phenanthraquinone can be toxic to algae. Only a few compounds
have been tested for toxicity to fish, and none have been tested for
toxicity to aquatic invertebrates.
18
-------
Ill LITERATURE SEARCH
Sources and Subject Area
Chemical Abstracts was searched from 1965 through May 1975 for bio-
logical and chemical activity of the six compounds under study. Part of
this was by manual search and the last 4-5 years (1971-1975) was carried
out using the Systems Development Corporation (SDC) computerized files
of Chemical Abstracts. The U.S. Government Reports file was searched by
using DIALOG computerized source. Other sources, such as Biological
Abstracts, Current Contents, and Selected Water Resources Abstracts were
searched manually.
Searching was done (1) by the Chemical Abstract Service number for
each compound, (2) on synonyms for each compound, and (3) by such terms
as environmental fate, biodegradation, toxicity, polynuclear/polycyclic
aromatic hydrocarbons, and coal tars as well as by the correct chemical
name.
In addition to the abstracts searched, references in pertinent
articles were scanned for further information, and calls to a selected
number of scientists working in this area were made to elicit additional
data or references.
Results
The number of references culled in the first search was overwhelming,
In the computerized search alone, approximately 3000 citations were
retrieved. Manual searching of other sources added about 600-700 more
references. Of these, approximately 1000 were selected for further
study by the panel of experts. Full-text copies of articles that
appeared to be of interest were ordered. Approximately 300 articles
were ordered.
19
-------
IV REVIEW AND EVALUATION OF LITERATURE
Formation and Degradation of PAH Under Environmental Conditions
A comprehensive review of the occurrence and properties of many PAH
was prepared by the National Academy of Sciences (NAS) in 1972. Although
quite complete in many respects, that review examined only qualitatively
the chemical and physical properties of PAH as related to their environ-
mental fate and lifetime. This review attempts to provide a more quanti-
tative framework for environmental fate and lifetime based on our current
knowledge of the dominant chemical reactions in air and water responsible
for removal of PAH, specific rate constants for these reactions and the
probable concentrations of reactive intermediates. It is important to
note that there are very few published reports of lifetime experiments
under environmental conditions and the estimates reported here are cal-
culated from composite sources. As such these values for lifetime are
probably accurate to within an order of magnitude (sometimes better).
Nonetheless, competing processes are often so slow that in many cases these
values can be used to provide a reliable model of environmental degrada-
tion.
Physical Properties and Transport
The physical properties of many PAH, which largely determine their
rates and mode of transport between air, water, and soil, are fairly well
characterized except for specific absorption properties. Tables 5 and 6
summarize some of these important properties.
All of the PAH are high melting/high boiling solids with very large
values for partition coefficients indicative of significant accumulation
and concentration in biological (lipid) material. These partition values
may be misleading, however, since very little if any PAH are actually
found dissolved in water. Recent observations of Andelman (1971) and
McGinnes (1974 a,b) suggest that PAH occur either as very finely dispersed
particles in water or adsorbed on a variety of particulates such as
-------
Table 6
VAPOR PRESSURE AND VAPOR CONCENTRATION OF SELECTED PAH AT 25 C
Benzo[a]pyrene
Benzo[a]anthracene
Benzo[e]pyrsne
Benzo[k]fluoranthrene
Benzo[ghi]perylene
Coronene
Anthracene
Phenanthrene
Pyrene
Vapor Concentration
vttpur fits
Torra
5
1
5
9
1
1
1
6
6
.49 x
.10 x
.54 x
.59 x
.01 x
.47 x
.95 x
.80 x
.85 x
10
10
10
10
10
10
10
10
10
ssuxw • • •-'- • • •
l.g/103 m3b
-9
_7
1333
-9
-11
13
-10
1.5
-12
-4 7
1.87 x 10
-4 7
6.51 x 10
-7
74 ,400
2
5
2
5
5
6
1
3
3
m<
.97
.84
.97
.15
.43
.66
.05
.65
.68
ales/
x 10
x 10
x 10
x 10
x 10
x 10
x 10
x 10
x 10
A
-14
-14
-14
-15
-16
-18
-8
-8
-11
All data from Pupp 1974 except for anthracene and phenanthrene,
Jordan (1954). The equations given in the references were determined
from data obtained at 100-300°C or higher; vapor pressures at 25°C
are extrapolations.
Calculated from data in Pupp 1974 except for anthracene and phenanthrene
which were calculated from equations in Jordan 1954 and the ideal gas law.
22
-------
minerals or carbonized materials. Solubilities in water of most PAH
with more than three rings appear to be too small to measure, that is,
less than 10 M.
Solubilization of PAH in water by micellar mechanisms involving
surface active species such as detergents, biopeptides, and alkaloids,
are suggested by Eisenbrand (1971) and Demisch (1963) as possible modes
of transport for PAH in natural waters. Available data do not provide
convincing evidence that these laboratory-observed solubilization
mechanisms are very important in natural waters where solubilizer con-
centrations are likely to be much lower than particulate concentrations.
The extremely large amounts of PAH, such as benzo(a)pyrene, found in
river bottoms suggest that adsorption on particulates and sediment clays
is a major process for removing these materials from water systems.
Recent data on vapor concentrations of PAH are of particular interest
in connection with transport and analysis of PAH in the air. Table 6
summarizes the data of Murray, Pottie, and Pupp (1974) and of Pupp et al
(1974). Vapor pressures for PAH at 25°C are extremely low, ranging from
-4 -12
6.8 • 10 torr for phenanthrene to 1.5 • 10 torr for coronene.
Nevertheless, the equilibrium vapor concentrations of some of the more
volatile PAH such as anthracene, phenanthrene, pyrene, and benzanthracene
are sufficiently high to lead to significant errors in analyses for air-
borne PAH where analyses are based only on collected particulates. The
data indicate that for benzopyrene, benzanthracene, and benzofluoranthrene
the equilibrium vapor concentrations can easily exceed the values reported
for these PAH in air, based on particulate sampling (Hoffmann, D. 1968).
However, in cases where PAH are quickly adsorbed by air-borne particulates
just beyond the combustion zone, then the actual concentrations in the
vapor state are likely to be much lower, thereby reducing the analytical
error.
23
-------
Recently Mackay and Wolkoff (1973) have developed a quantitative
treatment of the rate of transport of low-volatile organics from water
to air. Their results show that some high molecular weight organics
-5
such as Aroclor 1260 (mw 361; vapor pressure ~4 • 10 torr; solubility
-9
~7 • 10 M) have surprisingly low half-lives in water (28 min for Aroclor)
owing to exceptionally high activity coefficients. No calculations of
this kind have been applied to PAH; it is likely that adsorption of PAH
on surfaces will significantly reduce the activity coefficients,
which will slow the rate of codistillation. However, some measurements
of rates of distillation of PAH seem warranted.
Spectra
Spectral properties of six PAH summarized in Table 7 show that all
but one of these compounds absorb solar radiation strongly above the
solar cutoff (300 mm) , and in some cases well into the visible region.
This is one of the most important properties of PAH since it provides
the basis for efficient self-initiated photooxidation, a process discussed
in more detail below.
Dissimilarities in uv spectra have provided the basis for sensitive
analysis of PAH, particularly since log f is so large (Table 7). Fluor-
escence spectra of many PAH are also well characterized and provide the
basis for detection at concentrations of 0.01 - 0.001 the values useful
for adsorption spectra (NAS, 1972). However, it is clear that for a
natural system in which as many as several hundred PAH homologs, analogs,
and isomers may be found in a single sample, spectroscopic techniques
alone are not incisive enough to distinguish one PAH from another, and
additional separation and identification by GC/MS is now routinely used
along with fluorescence.
24
-------
Table 7
SPECTRAL PROPERTIES OF SIX PAH
\rnax log £ Solvent Ref.
nm
Benzo(a)pyrene 347 4.12 EtOH a, p. 839
364
384
344
351
360
308
323
338
355
375
309
314
323
330
337
345
2.88 EtOH
2.62
3.00
3.15
3.47 EtOH-
3 . 75 MeOH
3.86
3.87
2.40
2.48 EtOH-
2 . 54 MeOH
2.52
3.40
3.46
Benzo(a)anthracene 314
327 3.81 EtOH a, p. 751
341
359
376
386 3.86
Methylcholanthrene no absorption above 300 nm a, p. 892
Chrysene 344 2.88 EtOH b, p. 251
Anthracene
b, p. 291
Phenanthrene
b, p. 228
Refs: a. Organic Electronic Spectral Data, Vol. I. Interscience
Publishers, Inc., New York, 1960, Mortimer J. Kamlet, Ed.
b. Polycyclic Hydrocarbons, E. Clar. Academic Press, London,
1964.
25
-------
Formation of PAH
The ubiquity of PAH in the environment is well documented; Table 8
summarizes several studies on occurrence of PAH in the air, water, and
soil, and the review by Andelman and Suess (1970) provides a very
thorough review of PAH in water. Although anthropogenic combustion
sources are most commonly cited as the major source of PAH, natural
combustion sources (Blumer 1975) and microorganisms may also play
significant roles in their generation. Certainly conditions found in
forest fires are compatible with requirements found for conversions of
simple aromatics and hydroaromatics to PAH under laboratory conditions,
o
namely temperatures between 500 and 900 C and pyrolyzing rather than
oxidizing environments. Pyrolysis of lignins and terpenes during
forest fires is a likely source of PAH in relatively high yields (Dikun
1965, Levin 1965, Liverovskii 1972). Foodstuffs, including lipids and
cholesterol (Halaby 1971) and amino acids and carbohydrates (Masuda
o
1967) , are also probable sources of PAH when pyrolyzed at 300 - 700 C.
The chemical mechanisms by which PAH are formed by pyrolysis of
simpler organic structures are extremely complex. Badger's (1964a,b,c,
1966) extensive studies on pyrolysis of aliphatic, aromatic, and olefinic
compounds to PAH indicate that two- and three-ring structures arise from
cyclization of side chain radicals with aromatic rings, and that poly-
cyclic aromatics form by dimerization of di- and tricyclic aromatic or
hydroaromatic rings.
Blumer (1975) has recently suggested that PAH from natural combustion
sources, i.e., forest fires, are structurally distinct from PAH produced
from anthropogenic sources in having a high proportion of alkyl side
chains owing in part to the lower temperatures found in natural fires.
This is an interesting suggestion, which, if correct, could provide a
26
-------
Table 8
CONCENTRATIONS OF PAH IN AIR, WATER, SOIL
PAH
Benzo[a]pyrene
Benzo[a]anthracene
Methylcholanthrene
Chrysene
Anthracene
Phenanthrene
Benzo[e]pyrene
Benzo[k]fluoranthrene
Benzo[rghi]perylene
Coronene
Pyrene
Fluoranthene
Perylene
D. Hoffmann 1968
Borneff 1964
Giger 1974
a be
Air Surface Water Soil
jAg/10 m jj,g/l fig/kg
0.2 - 39 0.002 75-370d
0.1-22 0.014 41-330
e e e
0.038 40-240
8-170
33
1 - 26 59-310
1 - 20
2 - 46 66-280
0 - 20 5-20
1.3 - 35 0.110 100-960
0.128 110-790
26-94
Values as high as 15000 mg/kg reported in some sediments,
Andelman 1970
e
Occurrence mentioned in several references, but no quantitative
data were found. See M. Kertesz-Saringer 1972b (air); L. Zoccolillo
1972 (airborne particulates); and M.I. Stepanova 1972 (waste water).
27
-------
valuable means of distinguishing the natural burden of PAH (background)
in the environment from that imposed by man, both on a regional and
continental basis.
However, no published data are available that either corroborate
or refute Blumer's idea, and many of the older data (pre-1972) are based
on analytical techniques that fail to distinguish between alkylated and
non-alkylated PAH. Sawicki (1975) has expressed some reservations about
the results, based on the complexity of the analytical schemes employed
by Blumer.
Blumer's argument that natural combustion sources produce more
alkylated PAH because of lower temperatures where alkylated PAH are
possibly more stable may be misleading, since the rates of reaction of
PAH are governed by both temperature and time. Products from natural
combustion processes probably have longer residence times in the pre-
flame region than do products from utility boilers or automotive engines,
possibly enough longer to compensate kinetically for lower temperatures.
Since nothing is really known about how alkyl PAH are formed or their
rates of reaction in combustion systems (they may or may not oxidize
much more rapidly), the validity of Blumer's idea must be established
by extensive and careful analyses of PAH from a variety of natural and
anthropogenic sources.
Chemical Degradation of PAH
PAH are highly reactive compounds that undergo all the reactions
commonly found for simple aromatics as well as a number of reactions that
result from facile removal of one electron from the polycyclic system to
form a radical cation.
28
-------
Further reaction of the radical leads to oxidized products, including
endoperoxides, diols, quinones, and dimers. As expected, electron-
donating groups (alkyl, alkoxy) accelerate the rates of these reactions.
The NAS report (1972) provides a good review of the qualitative features
of these reactions, as does an earlier report by Tipson (1965), which
reviews oxidation reactions of PAH, particularly those using metal ion
oxidizers,
Rates of and Mechanisms of Degradation in Water
In some respects, reactions of PAH in natural waters are somewhat
simpler than in air owing to the presence of fewer kinds of oxidizing
species. In natural water the principal oxidizing species are (1) alkyl-
peroxy and hydroperoxy radicals (RO • , HO •), generated by photolytic
£ £
cleavage of trace carbonyl compounds or from enzymatic sources. [Radical
reactions involving oxygen are termed autoxidations.] (2) singlet oxygen
generated in a variety of reactions involving oxygen (ground-state) with
excited singlet and triplet species that are formed mostly (but not
exclusively) by light absorption by PAH. [Singlet oxygen ( 0 ) reactions
£t
are generally termed oxygenations or, where light is used, photooxygen-
ations.] Some quantitative rate data are available for estimating half-
lives of reactions of PAH with RO • radicals and singlet oxygen. Thus,
£i
the relative contributions of the two processes to degradation of PAH
may be compared.
Since most urban drinking water is treated with chlorine or ozone,
it is also of interest to try to estimate their effects on PAH lifetime
and compare them with autoxidation and photooxygenation.
Autoxidation—several qualitative studies of autoxidation of PAH
have been reported (NAS, 1972; Tipson, 1965). Although in most cases
detailed product analyses are not available, the substitution pattern
29
-------
for reaction of RO • radicals on the PAH ring should be much the same
£t
as for other electrophilic species including 0 , NO , and O . Mahoney
£4 & £t
(1964, 1965, 1975) has measured the rates of autoxidation of several
PAH under conditions where the rate constants for reaction of RO • and
<£
PAH can be evaluated.
Table 9 summarizes specific rate constants for reaction (1) and
o
half-lives for several PAH at 60 C. Half-life values for oxidation are
based on reaction (1) and the rate law
-d PAH/dt = k [RO -][PAH]
Thus, the half-lives depend only on values for k and [RO •]. We have
P -10
assumed that [RO •] has a steady-state value of 10 M, under average
jQ ~~
daily illumination in natural water systems.*
-10
t /days = 0.69/k 10
The surprising result is that anthracene is so much more reactive
than phenanthrene and so much less reactive than tetracene and that the
other tetra- and pentacyclics are so unreactive compared with tetracene.
Differences in rates of reaction of PAH with RO • are probably as large
£
as found for any group of organic compounds. For all PAH in Table 9,
except for tetracene, half-lives for radical oxidations are so long
o
even at 60 C that other, faster processes must intervene to remove them
from the environment. Experiments are needed to measure the value of
*This estimate is based on assumptions concerning average carbonyl
concentrations, quantum yields for radical formation and photon fluxes
in the absorption bands of interest.
30
-------
Table 9
ABSOLUTE RADICAL CONSTANTS AND HALF-LIVES
FOR REACTION OF RO • RADICAL WITH PAH AT 60°C
PAH
Anthracene
Phenanthrene
Tetracene
Benzo(a)pyrene
Perylene
Pyrene
k /I mol sec
P
50
a,b
<0.01
b
20,000
50
*l/2/day
1600
>8.10
4
9900
1600
Mahoney 1965
Mahoney 1964
Mahoney 1975
31
-------
k for other PAH and to estimate more reliably the range of concentrations
P
of RO • in natural water systems.
£*
Photooxygenation—The term photooxidation is commonly used to
describe all reactions with oxygen that require light, regardless of the
reactive species involved. The bulk of the evidence suggests that most
photooxidations of PAH involve reaction with singlet oxygen (photo-
oxygenation) ; however, generation of and reaction with peroxy radicals
is also possible via radical-cation intermediates (NAS, 1972).
Singlet oxygen can be generated by a variety of chemical and light-
sensitizer reactions. Gollnick and Schenck (1968) have reviewed early
work on the reactions of PAH with singlet oxygen, and the NAS report
summarizes the results. Products of photooxygenation vary with the
structure of the PAH; in cases where 9,10 positions are open (as in
anthracene), an endoperoxide is the primary product; but in some cases
it is unstable, and a quinone is the first isolable product. Benzo(a)-
pyrene photooxygenates to the same mixture of diones formed by oxidation
with one-electron oxidizers such as Cr(VI) (Antonello 1964). Although
singlet oxygen seems the likely oxidizer, the intermediate is probably
not an endoperoxide.
Of particular interest is (1) how the reactivities of different PAH
toward singlet oxygen are affected by structure and (2) how rapidly PAH
photodegrade under environmental conditions.
The detailed kinetic scheme for self-sensitized photooxygenation
of a PAH can be generalized following Stevens and Algar (1968)
1 *
M - M + hV (1)
1 * 3 *
M - M (2)
32
-------
V - M (3)
1 * 3 3 * 3
M + 0 -» M + O (4)
£t ft
1*3 3*1
M + 0 - M + 0 (5)
£t £
3 *
M - M (6)
3*3 1
M + O -» M + 0 (7)
2 2
3*3 3
M + O - M + O (8)
-------
Table 10
RELATIVE AND ABSOLUTE REACTIVITY OF PAH
TOWARD SINGLET OXYGEN
Rel. Reactivity
k/k
PAH
Anthracene
Q
Dimethylanthracene
Diphenylanthracene
Rub rene
Benzo (a) pyrene
Naphthacene
Dimethyldibenzanthracene
o
1
100
8
300
~1
>1
>1
Abs. Reactivity
-1 -1
k /I mol sec
2.10
2.108
1.710
6 • 10
10
>2 • 10
>2 ' 10
Ref.
Foote 1972
Corey 1964
Bowen 1954
Bowen 1954
Kuratsune 1962
Kuratsune 1962
Bowen 1954
Estimated roughly against anthracene.
b 5
From 0 values given in references and k = 10 sec.
34
-------
The actual rate of reaction (9) depends on the concentrations of
PAH and singlet oxygen, and the concentration of singlet oxygen will
depend on many factors including light flux, the quantum yields for
conversion of one excited species to another (including formation of
singlet oxygen in steps 5 and 7), and the rates of efficiencies of
competing deactivation processes such as steps 3, 6 and 7. Algar and
Stevens (1970) have examined several different mechanisms for inhibition
of photooxygenation in solutions of rubrene, dimethylanthracene, and \
dimethyldibenzanthracene,' In each case the role of oxygen in promoting
and/or inhibiting the quantum yield for photooxygenation is different.
Since the PAH occur in the environment as complex mixtures almost
always adsorbed on organic and mineral surfaces, the applicability of
these studies to environmental conditions is of limited value other than
to indicate some of the basic mechanistic features, the likely complica-
tions that may occur, and the danger of generalizing from one set of
experimental data. It is therefore of some interest to examine two
recent kinetic studies in which benzo(a)pyrene and benzo(a)anthracene
were photolyzed in water, either dispersed as microspheres or adsorbed
on mineral surfaces. Although neither study examined any mixtures of
PAH, these data are closer to an environmental situation.
McGinnes and Snoeyink (1974) carried out a study using benzopyrene
and benzanthracene dissolved in acetonerwater (20:80), dispersed in
water alone, and adsorbed on kaolin. Results summarized in Table 11
show that in acetone: water,the rates of oxidation of the two PAH are
nearly linear functions of light intensity and, at about a third to a
2
fourth the intensity of sunlight (1.0 - 1.3 mW/cm ), the rates of oxi-
dation of benzopyrene and benzanthracene are similar with first order
rate constants k = 0.29 and 0.44 hr , respectively. The rate law is
35
-------
Table 11
PHOTOOXYGENATION OF BENZO(A)PYRENE (BaP) AND
BENZ(A)ANTHRACENE (BaA) IN WATER AT 25°C a
PAH
BaP
BaP
BaA
BaA
Particulate
Form/Cone . "
Solution in
20% acetone:
water
1 rag/1
Microspheres
1.5 |j,m dia
1 mg/1 b
Solution in
20% acetone:
water 1 mg/1
Microspheres
1.5 Lim dia
Light Flux
mw/cm
0.13
0.48
1.15
0.61
1.37
0.13
0.48
1.37
0.61
1.31
k /hr
0.009
0.098
0.29
0.057
0.057
0.00
0.10
0.44
0.028
0.049
t hr
1/2
76
7.0
2.4
12
12 c
6.9
1.6
25
14
1 mg/1 b
a
McGinnes 1974
b
Refers to amount in total solution.
c
Reaction inhibited at 60% decomposition; second half-life was 3.5 days.
36
-------
of the form
- d(PAH)/dt = kl[PAH]
where I is light flux.
Significant differences in rates were found for the two PAH when
they were suspended in water as microspheres of ~1.5-ram diameter. Benzo-
pyrene disappears very rapidly until, when nearly 60% decomposes in about
8 hours, the process nearly stops and only 20% more decomposes in the next
2
4 days at the highest light flux, 1.34mW/cm . Benzanthracene, on the
other hand, shows a first order decomposition to nearly exhaustion of
2
benzanthracene with a life-life of ~14 hours at 1.37 mW/cm light flux
and nearly linear dependence on light intensity.
Not surprisingly, some data show that increased surface area increases
the rate of oxidation. When adsorbed on kaolin and suspended at different
loadings in water, both benzopyrene and benzanthracene decomposed at
similar rates, despite the fact that light scattering was 100-fold
greater in the high loading samples.
Andelman and Suess (1971) carried out similar studies on benzopyrene
dissolved in acetone and adsorbed on CaCO at several temperatures and
with variable oxygen concentrations. For the most part, their findings
agree with those of McGinnes and Snoeyink (1974) and elaborate on them.
2
One experiment using benzopyrene adsorbed on CaCO- at 0.31 mW/cm light
o
flux gave t . ~25 hours at 21 C.
The temperature dependence for this oxidation is summarized in
Table 12. The apparent activation energy for the process is 15 kcal/mole,
o o
corresponding to a ten-fold change in rate going from 0 to 25 C.
Andelman (1971) found a small effect of oxygen concentration on the
rate corresponding to [O ] ' . This effect could well be due to a
£t
balance between inhibition and activation processes discussed earlier.
The mechanistic significance was not elaborated.
37
-------
Table 12
TEMPERATURE DEPENDENCE FOR PHOTOOXYGENATION
OF BENZOPYRENE ON CaCO,, a'b
o
t, C
5
21
31
k /hr
1
0.0019
0.0087
0.022
t hr
1/2
360
79
31
a
Fieser 1935
5 g CaCOg with 1 p,g/g benzpyrene was illuminated
with a 1.3 raW/cm2 flux for 7 hours.
38
-------
Their data indicate that rates of photooxygenation of benzopyrene
will decrease dramatically in winter months even under clear skies or
when oxygen concentrations are very low, a conclusion that is consistent
with other observations (see section on Environmental Sources). The
reasons for the temperature and oxygen dependence need to be clarified
so as to be able to predict more accurately how environmental conditions
*
will affect rates for different PAH.
The autoinhibition found for benzopyrene microspheres but not for
its solution nor for benzanthracene in either form seems to be an
important observation in connection with environmental degradation of
PAH. The mechanism of inhibition in the microspheres may be simply
protective absorption of light by the product quinones, as suggested by
McGinnes (1974), or it could be a more complex inhibition scheme involv-
ing energy transfer or quenching peculiar to the solid state. Other PAH
may also exhibit this effect and more importantly, in mixtures of PAH
that are found in nature, inhibition by benzopyrene quinones could inhibit
the degradation of other PAH which would, by themselves, undergo more
rapid and complete degradation. Clearly more experimental work is needed
to answer some of these questions. The important conclusion that emerges
from these two studies is that under environmental conditions, benzo(a)-
pyrene and benz(a)anthracene undergo rapid photooxygenation when suspended
or adsorbed on mineral surfaces.
A more recent study (Katz and Lane, 1975) on photodegradation of thin
films of solid BaP under simulated smog conditions shows that high ozone
levels (2 ppm) markedly reduce the halflife to a few minutes in full sun.
McGinnes (1974) examined briefly the products from his experiments
and found the same quinones reported by others (NAS, 1972). In the case
of benzanthracene, its primary products (mostly quinones) began to de-
compose when about 90% of the parent PAH had disappeared. The results
suggest that the products are much less susceptible to photooxygenation
39
-------
than are the parent PAH, and that in many situations, these products will
remain for some time unless removed by some other alternative process.
Here again, additional work is required to evaluate, in a cooxidizing
system, the relative reactivities of different PAH and their products.
In addition to autoinhibition, another complication that must be
borne in mind when trying to interpret qualitative photochemical
environmental observations, with which the literature abounds, is that
other kinds of compounds also commonly found in water, soil or air can
affect the photooxygenation of PAH. For example, Gubergrits, Paalme,
and Kirso (1972) claim that phenols in water changed the kinetics and
mechanism of photodegradation of benzopyrene with the net effect, among
several competing reactions, of inhibiting photodegradation.
Some metal-ion complexes are well known (Guillory 1973) quenchers
for singlet oxygen; their presence as adventitious impurities along
i
with PAH could reduce significantly the rate of photooxygenation of
such mixtures. Although 3-methylcholanthrene does not absorb (Table 7)
above the solar cutoff (300 run) , it may be photooxidized where O is
£
produced by other PAH present in natural mixtures.
Reactions with Chlorine and Ozone
Chlorination or ozonization of urban drinking water is used to kill
pathogens , but the chlorine and ozone must also chemically interact with
organics such as PAH. One report by Trakhtman and Manita (1966) indicates
that one microgram of benzopyrene was reduced to 0.188 microgram in 30
—*\ fi
minutes and to 0.06 microgram in 2 hours using 7«10 M (0.5 mg/1) chlorine
in water. These data do not fit any simple kinetic scheme but correspond
to an initial ten-minute half-life, followed by a 30-minute half-life for
the next increment. The results are supported by some semi-quantitative
studies by Sforzolini et al (1973) who examined five PAH in water also
containing chlorine at 7«10 M. In 30 minutes all benzopyrene was con-
sumed; lesser amounts of other PAH, but in all cases over 50%, were
consumed in similar experiments.
40
-------
Ozone is commonly used for water treatment in Europe and is applied
in a batchwise manner at levels of 5 ppm. Products of reaction of ozone
with PAH in solution have been examined in detail, and the results are
summarized in the NAS report (1972).
The relative and absolute reactivities of PAH toward ozone do not
appear to have been determined in any systematic or quantitative way.
The best guess that can be made is based on the observation of Il'nitskii
t>
et al. (1968), who measured the amounts of PAH remaining after treatment
-5 o
of 0.67-10 g/1 of PAH with 0.4 g/1 of ozone for one minute at 25 C.
From these data we can calculate rough rate constants for reaction of
5 ppm ozone with PAH, which are summarized in Table 13.
Reactivity data in Table 13 confirm the qualitative observations that
PAH generally display similar reactivities toward ozone and that alkyl-
ation enhances this reactivity considerably. The data suggest that in
urban water supplies treated with ozone, lifetimes of PAH would be quite
short only if the ozone were not consumed more rapidly by other organics
and organisms or if the ozone did not evaporate.
s
A very recent report (Hoigne and Bader, 1975) suggests that the
active species in reactions of ozone with organic compounds in water is
H0« radical. Although extremely reactive this radical is produced from
ozone slowly at rates which correspond closely to those estimated from
Il'nitskii's data.
Degradation of PAH in Air
Each thousand cubic meters of urban air contains several micrograms
~^
of PAH adsorbed on particulate (Table 8) and as shown by Pupp et al.
(1974) for some PAH, equal or greater amounts also may be found in the
vapor phase (Table 6). No data are reported for chemical reaction of
PAH in the vapor phase, but a number of observations concerning the
decomposition ot PAH, particularly benzopyrene adsorbed on particulate
41
-------
Table 13
RATE CONSTANTS FOR REACTION OF PAH WITH OZONE IN WATER AT 25°C
T
k , 1 mol sec t , , rain
PAH 2' 1/2'
Pyrene 170 41
Benz(a)pyrene 110 63
Benz(a)anthracene 260 27
Dimethylbenzanthracene >680 <10
Dibenzanthracene 280 25
ail'nitskii 1968
r_ —,/\
Calculated from t = 0.69/k [0 ]; [O ] = 10 M.
1/2 2 o o —•
42
-------
in air, summarized in the NAS report (1972), point to rapid decomposition
with half-lives of hours owing to reactions with singlet oxygen, ozone,
or other constituents of urban smog. Particular emphasis is given in the
NAS report to the enhanced reactivity of PAH adsorbed on some surfaces
such as silica or alumina where radical cations form readily and react
to give oxygenated products, even in the absence of light. No data
exist from which to calculate reliably lifetimes of PAH on suspended
particulate, but some data exist from which lifetimes in the vapor state
may be estimated. It is likely that rates of equivalent reactions on
particulates will be slower.
The two principal oxidizing species in urban air are HO- radical,
formed through a cycle involving photolysis of NO , water, CO, and simple
organic compounds (Hecht 1974) , and ozone formed from the O atom and
oxygen. Recent measurements of HO«radical concentrations in urban air
-14
give values of 10 M (Niki 1975); ozone concentrations vary in clean
-9
air and are about 2»10 M, but may be ten times larger in polluted air
(Levy 1971).
Rate constants for reaction of PAH with HO«radical are not known;
if we assume that the reactivity of PAH is similar to that of ethylene
9.3 -1 -1
which is nearly diffusion controlled (Wilson 1971) , k = 10 1 mol sec
and for a pseudo-first order reaction
t = 0.69/k [-OH] = 0.69/10 ' • 10~
1/2 2
t , = 9.6 hr.
1/2
This average half-life value for PAH is based on the largest reasonable
rate constant for reaction with HO« radical; therefore, it is probable
that true half-lives are longer.
Reactions of PAH with ozone in the vapor phase have half-lives shown
in Table 14. These data are based on rates in water calculated from the
43
-------
Table 14
HALF-LIVES FOR REACTIONS OF PAH WITH OZONE IN THE GAS PHASE
a
k2
-1 -1 t hrs
PAH 1 raol sec 1/2
Pyrene 170 560
Benzo(a)pyrene 110 870
Benz(a)anthracene 260 368
*
Dibenzanthracene 280 342
Dimethylbenzanthracene >680 >141
a See Table 13
44
-------
data of Il'nitskii et al. (1968) given in Table 13, and a steady state
-9
concentration of ozone in the vapor phase of 2*10 M (Levy 1971).
These values for t are so large that reaction with ozone hardly
seems likely to be an important process for conversion of PAH. The same
conclusion applies to PAH adsorbed on particulate unless the PAH are
greatly activated by adsorption.
Reactions involving singlet oxygen with simple organic compounds in
the vapor phase are thought not to be important in smog chemistry owing
to its very low concentration and the variety of processes that rapidly
quench it (Dermerjian 1974).
However, the self-sensitized photooxygenation of some PAH involves
intimate contact between PAH and singlet oxygen, which greatly increases
the probability of further reaction before singlet oxygen is quenched
(Stevens 1968, Algar 1970). Thus, the data of McGinnes and Snoeyink (1974),
summarized in Table 11, are likely to be relevant to gas phase processes as
well, with half-lives of 2-14 hours under similar conditions of light flux.
The oxygen atom, produced in the air by photolysis of NO and ozone,
&
is thought to play a minor role in oxidation of organic compounds; its
ambient concentration is extremely low (Jaeger 1973, 1974), and it seems
safe to assume that it cannot have an important role to play in removing
PAH either from the vapor phase or from particulate.
Other reactants in urban atmospheres and in combustion plumes include
nitrogen oxides and sulfur dioxide. Although the NAS report (1972)
implies that NO might react with PAH via a facile electrophilic substi-
£
tution reaction, it is doubtful that such a reaction is fast enough to
be of any importance under atmospheric conditions where NO concentrations
X
-7
are near 10 M. At higher temperatures and with NO concentrations
~5 x
closer to 10 M, as found in combustion plumes, such reactions become
more probable. Sulfur dioxide has recently been implicated in reactions
with PAH on particulate from chimneys (Jaeger 1973, 1974). In the
45
-------
laboratory, benzopyrene and pyrene, adsorbed on alumina, react with
SO fairly rapidly under some conditions, possibly through a radical
2
cation intermediate, to produce sulfonic acids (Jaeger 1973).
Toxicity, Bioaccumulation, and Biodegradation
Much of the information on the toxicity, accumulation, and degrada-
tion of the polycyclic aromatic hydrocarbons (PAH) in biological systems
has been discussed and summarized in a comprehensive treatise published
by the National Academy of Sciences (NAS, 1972). This work reviews
pertinent reports published up to 1971 and should be consulted for
information regarding toxicity in terms of carcinogenicity, teratogenicity,
and mutagenicity, accumulation in plants and mammals, and degradation
(metabolism), particularly by mammalian systems, of PAH compounds.
The NAS report does not include information on the non-oncogenic,
-mutagenic or -teratogenic effects of PAH compounds in mammalian, non-
mammalian, or plant life, nor does it address such topics as the accu-
mulation of these compounds in wild life (animals, plants, and protists)
or the degradation of the compounds by organisms other than laboratory
mammals and isolated enzyme systems.
Toxicity
Little is known about the toxicity of PAH compounds aside from
information that many are carcinogenic in laboratory mammals and in
some cases, humans, and that some have been shown to be mutagens or
teratogens.
Algae
Table 15 summarizes acute toxicity data obtained by Fitzgerald
and coworkers (1952) for various species of algae exposed for 24 hours
to phenanthroquinone, which is a degradation product of phenanthrene.
46
-------
Table 15
ACUTE TOXICITY OF PHENANTHRAQUINONE TO BLUEGREEN ALGAE
Percent Survival
Algae Species
Microceptis aeroginosa
Microceptis incerta
Anabaena circinalis
Glocotrichia echinulata
Aphanizomenon flos aquae
Anaceptis marina
Coccochloris peniocystis
Gloecapsa membranina
Gloecapsa dimidiata
Gloecapsa alpicola
Plectonenia nostocorum
Nostoc muscorum
Nostoc commune
Calothrix parietina
*
Chlorella pyrenoidosa
Phenanthraquinone Concentration
(ng/D
0
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
40'
75
0
0
25
0
0
-
100
100
100
50
100
100
10
100
80
5
0
0
0
0
0
5
100
100
50
50
100
100
10
10
120
0
0
0
0
0
0
0
50
100
50
25
100
100
10
0
800
0
0
0
0
0
0
-
10
10
0
10
0
0
0
0
Green alga
Source: Fitzgerald, et al., 1952.
47
-------
The data indicate that with the exception of Anaceptis marina
and Coccochloris peniocystis the algae that tend to produce noxious
blooms (the first six) are more sensitive to phenanthraquinone than
algae that do not produce blooms (last nine).
At low concentrations (10-20 |Jig/l), fluoranthrene, 1,12-benzo-
perylene, 3,4-benzofluoranthene, indeno(l,2,3,cd)pyrene, 1,2-benzanthracene,
3,4-benzopyrene, and 1,2,5,6-dibenzanthracene are reported to promote the
growth of Chlorella vulgaris, Scenedesmus obliquus, and Ankistiodesmus
oranunii (Graef and Nowak, 1966). The growth promoting potency appeared
to correspond to carcinogenic potency. Benzo(a)pyrene was most effective;
fluoranthene and 1,12-benzoperylene were least effective.
Higher Plants
It appears that photooxidation products of some PAH compounds
are more toxic to leafy plants than the parent compound. Halbwachs and
Hlabwatsch (1968) found that acridine, anthracene, fluoranthene, 9-methyl-
anthracene, and 9,10-dihydroanthracene were toxic to higher plants only
when the fumigated plants were exposed to direct sunlight. Chrysene,
fluorene, phenanthrene, and carbozole were without this effect. 2-Methyl-
anthracene was phytotoxic with or without direct sunlight. Plants sprayed
with antioxidants were protected against the phytotoxic effects of those
PAH compounds that were toxic only in direct sunlight. This effect could
result from either preferential light absorption or from chemical inter-
ference with oxidation.
Although some PAH compounds have been shown to be toxic to
plants, Graef and Nowak (1966) found that application of 10-20 p,g/l
fluoranthene, 1,12-benzoperylene, 3,4-benzofluoranthene, indeno(l,2,3,
cd)pyrene, 1,2-benzanthracene, 3,4-benzpyrene, or 1,2,5,6-dibenzanthracene
to cultures of tobacco, rye, or radish promoted their growth, and as they
observed with algae (see above). The degree of effectiveness in promoting
plant growth appeared to correspond with increased carcinogenic potency.
48
-------
Bacteria
Although a variety of microorganisms can metabolize and thus
degrade various PAH compounds, PAH compounds may be toxic at high con-
centrations. Hass and Applegate (1975) reported that at concentrations
-7 -5
of 10 to 10 M, anthracene, phenanthrene, chrysene, 1,2,3,4-dibenz-
anthracene, and pentacene inhibited the growth of cultures of Escherichia
coli. On the other hand, 1,2-benzanthracene, 1,2,5,6-dibenzanthracene,
and 3,4-benzpyrene, stimulated bacterial growth at these concentrations;
and tetracene and pyrene had little or no effect. On the basis of this
information the authors concluded that utilization of PAH compounds for
growth by E. coli requires an angular acene molecule. PAH compounds
with linear acene structures tend to inhibit growth. Inspection of the
structural formulas of these compounds will show that this conclusion is
erroneous.
In a series of studies on the oxidation of organic chemical
carcinogens by activated sludge, Malaney and coworkers (1965, 1966, 1967)
found that many PAH compounds were toxic to sludge microorganisms (as
measured by O uptake), and that sludge microorganisms from different
£t
sewage treatment plants reacted differently to the compounds.
Although 500 mg/1 was the only concentration used, the tests
were conducted with 2500 and 5000 mg/1 suspended solids to determine the
effect of doubling the bacterial population on oxidation. Doubling the
bacterial population appeared to decrease the toxicity and to a certain
extent, increase oxidation.
Listed below are the compounds that were toxic when the suspended
solid concentration was 2500 mg/1.
1,2 ,5 ,6-dibenzanthracene
7-methyl-l,2-benzanthracene
49
-------
1,2,4,5-dibenzpyrene
3-methylcholanthrene
2-ni trofluorene
2-fluoreneamine
N-2-fluorenylacetamide
7,9-dimethylbenz(c)acridine
7,10-dimethylbenz(c)acridine
Dibenz(a,h)acridine
Dibenz(a ,j)acridine
Studies by Joyce and White (1971) showed that Staphylococcus
aureus developed an electron transport system whenever the growing cells
were aerated. This occurred simultaneously with increases in phospho-
lipids and carotenoids. Addition of 3,4-benzopyrene to the culture system
slowed the formation of the electron transport system, inhibited cyto-
chrome oxidase synthesis, and depressed the synthesis of phospholipids
and carotenoids. In earlier work, White (1970) found that the growth
-5
of S. aureus was inhibited by 10 M benzo(a)pyrene, benzo(e)pyrene, and
dibenz(a,j)acridine as well as by the 2-ringed aromatic hydrocarbons such
as ot-naphthylamine and p-naphthylamine.
Invertebrates
Exposure to 0.5% solutions of 3,4-benzopyrene, 3-methylcholan-
threne, or dimethylbenzanthracene for several weeks resulted in the for-
mation of hyperplasia and incipient tumors in the earthworm (Lumbriculus
terrestris) (Gersch 1954). Planaria treated with 3,4-benzopyrene or
3-methylcholanthrene developed lethal growths upon forced regeneration,
and offspring from the treated animals developed lethal papilliform
tumors (Foster 1969). Tumors have also been reported in snails treated
with 3,4-benzopyrene (Krieg 1970).
50
-------
According to Epstein and coworkers (1963), 3,4-benzopyrene is
lethal to the unicellular invertebrate Paramecium caudatum when its
administration is followed by exposure of the animal to sublethal levels
of ultraviolet light. This response is inhibited by the presence of anti-
oxidants. This suggests that some photooxidation product of benzopyrene
is the toxic factor and supports the previously described results on the
effects of photoirradiation on the phytotoxicity of certain PAH compounds.
In sponges, 500 mg of 3,4-benzopyrene per 100 ml of seawater
caused choanocyte damage and abnormal growth of the oscular tube (Korotkova
and Tokin, 1968). This effect was observed only in the highly colonial
sponges such as Leucosolenia complicata and L. variabilis, and not in the
simple spongelike Sycon raphanus. Injections of 3,4-benzopyrene are
reported to increase ciliary activity and metabolism in fresh water
mussels (Haranghy 1956).
In the housefly (Musca domestica) Cantwell and coworkers (1966)
reported that exposure to 2,7-diaminofluorene, N-fluoren-2-yl-acetamide,
7-fluorofluorene-2-acetamide, and N-fluoren-2-yl-N-hydroxyacetamide
inhibited growth, pupation, and adult emergence.
Fish and Amphibians
Little is known about the toxicity of PAH compounds in fish and
amphibians. Compounds for which there is some toxicological information
are anthracene, sodium anthraquinone-a-sulfonate, chrysene, phenanthrene,
and phenanthraquinone.
Screening studies were performed by Applegate, et al., (1957)
on a large number of different chemicals as part of a program to identify
a. toxicant specific for lamprey. The highest concentration employed was
5 mg/1, and the maximum exposure time was 24 hours. They reported that
anthracene and chrysene had no effect on the rainbow trout, bluegill sun-
fish, or larval lampreys. Phenanthrene was lethal to rainbow trout
51
-------
and bluegill sunfish at 5 mg/1 in 12 hours, but had no effect on lamprey
larvae. Other investigators (McKee and Wolfe 1963) report lethal con-
centrations of 1 to 5 mg/1 for phenanthrene. .In the mosquito fish, the
96-hour TL50 for phenanthrene is reported as 150 mg/1 (EPA 1970) .
Phenanthraquinone was nontoxic to the black crappie (Pomoxis
migromaculatus) , emerald shiner (Notropis atherenoides), blunt nose
minnow (Hyborhynchus notatus) , rock bass (Ambloplites rupestris) or
large mouth bass (Micropterus salmoides) when they were exposed for 48
' ~~ ~ ~~ " " ~ i
hours to solutions containing excess compound (Fitzgerald, et al., 1952).
Manfred (1970) reported that painting of 20-30 mg of benzo-
pyrene and 20 mg of methylcholanthrene on the skin of short-lived fish
(Rhodeus amarus and Gasterosteus aculeatus) for 2 to 7 months produced
epitheliosis. Injection of benzopyrene produced injection site necrosis,
but no neoplasms. No effect was observed in a similarly treated long-
lived fish (Cyprinus carpio) . When fed at a rate of 0.3 (j,g/mg body
weight for 110 days, 3,4-benzopyrene and 3-methylcholanthrene increased
the rate of respiration in the fish Platypoecilus maculatus and Xiphophorus
helleri by 15 to 30% over controls. This treatment caused Xiphophorus
helleri to grow about 25% slower than controls; however, in Platypoecilus
maculatus, both compounds enhanced the rate of growth 2.0 and 2.5-fold,
respectively.
The low lethal dose for 3,4-benzopyrene is reported to be 11 mg/kg
in the frog (NIOSH 1974) . This compound is also reported to induce tumors
in amphibians (Leone 1953; Seilern-Aspang, 1962, 1963; Balls 1964) and to
cause abnormal morphological development in tadpoles (Dontenwill 1953 ,
DeLustig 1971, Matos 1973).
On the other hand, Breedis (1950) did not observe tumor for-
mation in salamanders injected subcutaneously with 3,4-benzopyrene; and
Arffman and Christensen (1961) reported that administration of this
52
-------
compound as well as dibenz(a,h)anthracene and 3-methylcholanthrene to
a species of newt produced epithelial proliferation but no tumors. Of
the three, dibenzanthracene was the most potent.
Application of 1,2,5 ,6-dibenzanthracene or 3,4-benzopyrene to
the amputated tail of the newt, Triturus viridescens, failed to produce
tumors; however, the rate of tail regeneration was markedly reduced by
these compounds (Pizzarello 1966). Lecamp and Delsol (1947) reported
also that 3,4-benzopyrene did not induce tumors in regenerating limbs
of the accoucheur toad but inhibited the rate of regeneration and
appearance of the formed limb. Similar results were observed by Prada
(1946) in Triton vulgaris.
Matoltsky (1947) reported no tumor formation in the amphibians,
Rana esculenta and Triton cristatus injected with an 0.3% solution of
3,4-benzopyrene. However, he observed hemorrhaging in the kidney and
liver, parenchymal degeneration, fatty degeneration, and necrosis. In
the frog (R. esculenta) he observed pulmonary edema, cellular infiltra-
tion, and edematous swelling of the alveolar walls as well as edema of
the skin and abdomen. Bonte (1950) also failed to induce tumors in
frogs with 3,4-benzopyrene, implanted or painted on the skin; however,
the compound produced atrophy and regression of the mucous glands of
the skin and increased the permeability of the skin to water.
Dontenwill (1953) observed inhibition of cleavage and distur-
bances in the formation of blastomeres and neurolation in Triton and
Axototl eggs exposed to unspecified concentrations of 3,4-benzopyrene.
Colombo (1948), however, found that 3,4-benzopyrene concentrations of
1:2000 to 1:20,000 had no effect on the development of the ova, morula,
or gastrula of the frog, Rana esculenta. Ruhland (1954) observed that
1:1000 to 1:10,000 solutions of 3,4-benzopyrene reduced the motility of
the sperm of Rana fusca ; however, eggs fertilized by these sperm
developed normally.
53
-------
Birds
Intratracheal administration of 3-methylcholanthrene (dose not
specified) to ducks produces acute and chronic inflammation, and prolonged
administration of the compound produced a variety of pulmonary tumors
(Rigdon 1961). Administration of 3,4-benzopyrene also produces chronic
pulmonary inflammation, but no tumors (Rigdon 1965b). Benzopyrene does
not appear to be acutely toxic to ducks or chickens given a single oral
dose of 250 mg (Rigdon 1963a) .
Administration of up to 2.5 mg benzopyrene/g of food for 24 days
does not affect the growth or survival of chicks, nor does a diet of 0.1
mg/g of food have any effect on the sperm, ova, egg fertility, or chicks
from eggs obtained from treated hens (Rigdon 1963b).
Mammals
Although many PAH compounds have been tested for carcinogenicity,
there appears to be little information on the acute and subacute toxicity
of these compounds. Studies concerned with effects of PAH compounds on
enzyme systems and other biochemical factors have usually been aimed at
elucidating the mechanism of carcinogenic action. Some of these studies
were reviewed because the information relates to the effects of PAH
compounds on metabolic processes.
In an in vitro study on the effect of 5 PAH compounds on the
activity of selected enzymes, Gemant (1967) observed that the activity
of catalase, an enzyme that acts on hydrogen peroxide and thus regulates
the amount of this compound in tissues, was reduced by up to 50% by the
PAH compounds. In order of decreasing inhibition potency, the compounds
were 3-methylcholanthrene, 3,4-benzopyrene, 1,2-benzanthracene, 9,10-
dimethyl-l,2-benzanthracene, and anthracene, which suggests that the
54
-------
catalase-inhibiting potency of the PAH compounds is related to their
carcinogenic potency. None of these compounds had any effect on the
activity of peroxidase.
The activity of lipoxygenase, another oxidoreductase, was
only 447» of the control level in the presence of 3,4-benzopyrene, the
most potent inhibitor, and only 46 and 51% of the control value in
the presence of methylcholanthrene and dimethyIbenzanthracene. Of the
three carcinogens, dimethyIbenzanthracene inhibited that activity of
ribonuclease most and benzopyrene was least effective. None of the
carcinogens had any effect on the activity of trypsin.
In mice injected with 1.25 mg of 3,4-benzopyrene or 2.5 mg
of 3-methylcholanthrene (Draganov 1966) a significant increase occurred
in succinic dehydrogenase activity in lung tissue 60 days after injec-
tion but not at 30 days after the injections. He reported that enhanced
succinic dehydrogenase activity occurred at the same time that patholo-
gical changes in the lung tissue were observed. Zinnari (1964) observed
that same effect in liver tissue, but enhanced succinic dehydrogenase
(SH) activity occurred much more rapidly. In mice injected with a 2%
solution of 3,4-benzopyrene, the activity of succinic dehydrogenase
increased about 3-fold above the control level on the second day and
gradually decreased to near control levels by the 30th day. However,
the degree of morphological changes in the liver mitrochondria increased
with time, rather than with enhancement of succinic dehydrogenase
activity.
The effect of PAH compounds on the activity of cathepsin from
subcellular fractions of rat liver homogenates was investigated by Lomsadze
and coworkers (1969). They found that dimethyIbenzanthracene, 3-methyl-
cholanthrene, 1,2-benzopyrene, and anthracene lowered the activity of the
55
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enzyme at a concentration of 0.005M. Anthracene was least effective.
These investigators also found a reduction in cathepsin activity in the
rat liver 2 to 5 months after a single injection of 5 mg of dimethyl-
benzanthracene to rats.
DeLuca (1969) reported no changes in liver glutamic-oxalacetic
transaminase (GOT) or glucose-6-phosphate activity in rats injected with
0.1 mg 3,4-benzopyrene; however, at a dose of 0.5 mg, the activity of GOT
was enhanced.
Intravenous injection of 0.5 mg of anthracene, pyrene, perylene,
3,4-benzopyrene, or 1,2 ,5 ,6-dibenzanthracene caused an increase in liver
SH levels in mice within 15 minutes to 1.5 hours. Subsequently, the SH
levels dropped to below normal.
Rigdon (1965a) observed a decrease in weight of mice fed up to
1.0 mg 3,4-benzopyrene/g of food; however, he found that the decrease was
due to a decrease in food intake rather than to benzopyrene toxicity.
Reduced intake was due to the ability of the animals to detect the pre-
sence of the compound in partial rejection of the treated food. Mice
reared on treated food from the time of weaning readily ate the food and
gained as much weight as the control animals. Rigdon (1966) observed
that mice from mothers fed 3,4-benzopyrene during pregnancy and lactation
did not grow as rapidly as the controls beginning 10-12 days of age.
This effect was attributed to nutritional deficiencies rather than to a
direct effect of benzopyrene.
Bioaccumulation and Modegradation
A relatively large number of PAH compounds have been identified in
living matter. Data from field and laboratory studies indicate that
organisms throughout the phylogenetic scale can take up PAH compounds
from the environment, including food, and also metabolize these compounds.
56
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The metabolism of PAH compounds by mammals has been the object of
much research. Ample, evidence exists that these compounds are metabolized
by mammals and some evidence that the products of metabolism may be the
carcinogenic factor for some of the compounds. The metabolism of PAH
compounds by mammals is well reviewed in the NAS document (1972) as is
their accumulation by plants; hence, neither subject will be discussed to
any great extent in this report.
Bacteria
Although measurable quantities of PAH compounds have been found
in bacteria grown in PAH-contaminated media, and a number of studies have
shown that bacteria metabolize certain PAH compounds, it is not clear
whether the compounds studied are adsorbed or absorbed by the bacteria
or whether metabolism occurs intra- or extra-cellularly.
When adapted to soil containing 3,4-benzopyrene, Pseudomonas
aeruginosa and Escherischia coli took up about 90% of the compound from
the medium, metabolized 10 to 26%, showed enhanced growth, and contained
3 to 15 times more protein than normal (Lorbacher, et al., 1971). Studies
by Moore and Harrison (1965) showed that various enterobacteria such as
Salmonella typhimurium, Aerobacter aerogenes, and Escherischia coli as
well as various strains of Saccharomyces cerevisiae are capable of
accumulating 3,4-benzopyrene; however, they metabolized little of the
compound. Uptake in E. coli amounted to 10 to 2 x 10 p.g benzo-
pyrene per cell.
In a series of reports, Poglazova (1971) and Poglazova and co-
workers (1966, 1967a,b, 1971), observed uptake of 3,4-benzopyrene by up
to 20 strains of soil bacteria, including Mycobacteriuin flavuin, M. rub ruin,
M. lacticolum, M. smegmatis, Bacillus megaterium mutilate, and Bacterium
sphaericus. M. rubrum and M. flavum metabolized about 50% of the compound
in 4 days. 3,4-Benzopyrene is also taken up and metabolized by Endomyces
57
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magnusii and by Candida lepolytica (Petrikevich, et al., 1964), and is
accumulated from forest soil compost by Clostridium putrifaciens (Mallet
1965).
Shabad (1968) and coworkers (1971a,b) studied the rate of
3,4-benzopyrene destruction by various strains of soil bacteria isolated
from various areas and found that strains isolated from soil highly con-
taminated with benzopyrene were capable of metabolizing from 75 to 86% of
the compound in 5 days, while those from low benzopyrene areas could
metabolize only 48 to 59% in the same period of time.
Bacteria also metabolize anthracene and phenanthrene (Evans,
et al., 1965), 9,10-dimethyl-l,2-benzanthracene, 1,2,5,6-dibenzanthracene,
1,2-benzanthracene, 1,2-benzopyrene, pyrene, 1,12-benzperylene, and
perylene (Fedoseeva, et al., 1968). The last 7 compounds were metabolized
by Bacillus megaterium at the same rate, regardless of concentration or
solubility in the medium (Fedoseeva, et al., 1968). Soil microorganisms
also appear capable of metabolizing 3-methylcholanthrene (Lijinsky 1956).
Aquatic bacteria appear to be less efficient in metabolizing
PAH compounds than soil microorganisms. Bacteria in power plant and coke
oven wastewater contaminated with 3,4-benzopyrene metabolized less than
15% of the compound (Poglazova, et al., 1972). Malaney (1966) reported
that anthracene was only slightly oxidized by sewage sludge bacteria
acclimated to benzene.
Malaney and coworkers (1967, See also Lutin 1965) studied the
susceptibility of 17 PAH compounds to oxidation of activated sludge
microorganisms and found that most were resistant to oxidation. Phen-
anthrene, a tricyclic compound, was most susceptible to oxidation. For
this compound the oxygen uptake by the sludge amounted to 22 to 46% of
58
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the theoretical oxygen demand (TOD) calculated on the basis of complete
oxidation of the compound. In contrast, oxygen uptake for the two-ringed
compound, naphthalene, amounted to about 33 to 64% of TOD. Another tri-
cyclic compound, anthracene, was very resistant to oxidation (2 to 13% of
TOD). Of the remaining compounds, the quadracyclic compound, 9,10-
dimethylbenzanthracene was most susceptible to oxidation (19.6% of TOD);
however, the other benzanthracenes were resistant. The penta- and
hexacyclic compounds were essentially inert. The acridines were also
inert, and some were toxic. Some of the fluorenes were susceptible.
The compounds that were tested are listed below:
(1) 9,10-Dimethylanthracene
(2) 7-Methyl-1,2-benzanthracene
(3) 9 ,10-Dimethyl-l,2-benzanthracene
(4) 1,2-Benzanthracene
(5) 1,2,5,6-Dibenzanthracene
(6) 3,4-Benzopyrene
(7) 1,2,4,5-Dibenzopyrene
(8) 20-Methylcholanthrene
(9) 2-Nitrofluorene
(10) 2-Fluoreneamine
(11) N-2-fluorenylacetamide
(12) 7,9-Dimethylbenz(c)acridine
(13) 7,10-Dimethylbenz(c)acridine
(14) Dibenz(a,h)acridine
(15) Dibenz(a,j)acridine
(16) Anthracene
(17) Phenanthrene
It thus appears that susceptibility to microbial degradation
is not necessarily a function of the number of benzene rings in the
structure of the compound.
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Marine bacteria are capable of metabolizing phenanthrene,
anthracene, and fluorene (Dean-Raymond 1975).
Higher Plants
A variety of PAH compounds have been found in plants. These
include:
Anthracene 3,4-Benzopyrene
1,2-Benzanthracene Chrysene
1,2,5,6-Dibenzanthracene Coronene
10,11-Benzfluoranthene Fluoranthene
11,12-Benzfluoranthene Indeno(l,2,3,c,d)pyrene
1,2-Benzoperylene Perylene
1,12-Benzoperylene Phenanthrene
1,2-Benzopyrene Pyrene
Reports that we have reviewed indicate that PAH compounds may
enter plants through the leaves and roots; however, whether the roots or
the leaves constitute the major route of entry is not clear.
Shabad (1968) analyzed the leaves of a variety of plants sur-
rounding an oil refinery and discovered that the 3,4-benzopyrene content
of the leaves diminished with the distance away from the refinery. Broad,
prostrate leaves tended to contain larger amounts of the compound than
slender, upright leaves, and washing removed a significant amount of the
compound. He concluded that the source of 3,4-benzopyrene in the leaves
was atmospheric fallout.
Shabad and coworkers (1971a) also grew plants (nasturtiums and
asters) in a 3,4-benzopyrene-treated nutrient medium and found the com-
pound distributed throughout the plants, indicating root absorption.
Similar results were obtained by Doerr (1965) with peas, wheat, and
barley grown in 3,4-benzopyrene-treated soil and nutrient media.
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Little is known about the metabolism of PAH compounds by plants.
Shabad and Cohen (1972) stated that Durmishidze (1968) demonstrated that
vascular plants are capable of metabolizing hydrocarbons, including those
of cyclical structure.
Aquatic Organisms
Little information is available on the uptake or metabolism of
PAH compounds by aquatic organisms. 3,4-benzopyrene has been found in
marine algae, plankton, molluscs, and worms (Mallet 1967). It and perylene
have been measured in phyto- and zooplankton, higher algae forms, and
Crustacea (Niaussat and Auger, 1970a,b). Niaussat and Auger (1970a,b)
also reported that the biota in a lagoon contaminated with 3,4-benzopyrene
and perylene contained both compounds. The water contained 1.6 and 3.05
M-g/1 of benzopyrene and perylene, respectively. Plankton contained 0.73
f
and 0.27 fig/100 g (7.3 and 2.7 M-g/k§) > tne higher algae contained £26- 3^
lib
and -605 ^g/kg, and isopod Crustacea contained 536 and 865 p,g/kg, indi-
cating that accumulation and perhaps biomagnification occurs. Crustaceans
collected from the ocean outside the lagoon contained little or no benzo-
pyrene or perylene.
Plankton collected in the North Atlantic were analyzed for
fatty acid content and 3,4-benzopyrene by deLima-Zanghi (1968). Plankton
collected from coastal areas contained significant amounts of benzopyrene,
whereas those collected from the high seas were uncontaminated. No
correlation was found between lipid content or type (saturated or
unsaturated) and benzopyrene content.
Freshwater worms of the genus Tubifex exposed to 0.01, 0.1, and
100 |j,g 3,4-benzopyrene /liter for 6 to 11 days, accumulated up to 88.2
mg/kg of the compound. The amount accumulated increased with increasing
exposure concentrations. When placed in uncontaminated flowing water
for 40 days, the worms lost about 75% of the compound (Scaccini-Cicatelli
1966).
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That mammals can metabolize at least some PAH compounds is
well-known. There is evidence that chickens and ducks also can metabolize
3,4-benzopyrene (Rigdon 1963a).
Biodegradation Products
As mentioned previously, the metabolism of PAH compounds and
the identification of their metabolites is known primarily from bacterial
and mammalian systems. The metabolism of PAH compounds by plants, inver-
tebrates other than bacteria, and by the lower vertebrates is unknown.
In mammals the major metabolites of PAH compounds are hydroxyl-
ated derivatives, and carboxylic acid derivatives are also formed (Sims
1970) . A review of current knowledge on the metabolic products of PAH
compounds in mammals is given in the NAS document (NAS 1972). In general,
mammals and perhaps birds do not have the ability to degrade PAH compounds
completely. Some of the metabolites have been found to be active carcin-
ogens but less so than the parent compound (Boyland and Sims 1967) or
mutagens (Cookson, et al., 1971; Ames, et al., 1972). These metabolites
include the hydroxylated derivatives as well as the epoxides. As a rule
the parent compound as well as the metabolites is excreted via the urine
and to a certain extent, the feces (Evans, et al., 1965).
Bacteria have been shown to utilize PAH compounds as a carbon
source for growth, and evidence exists that they can metabolize PAH
compounds much more completely than do mammals. This evidence comes
from studies on only a few PAH compounds, particularly anthracene and
phenanthrene.
According to Evans and coworkers (1965), phenanthrene is meta-
bolized by soil pseudomonads to 1,2-dihydroxynaphthalene via several
steps involving intermediates such as trans-3-4-dihydro-3,4-dihydroxy-
phenanthrene (Colla, et al., 1959), 3,4-dihydroxyphenanthrene, and
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Marine fish absorb 3,4-benzopyrene through the gills, metabolize
the compound in the liver, store it and its metabolites in the gall-
bladder, and finally excrete both in the urine (Lee, et al., 1972).
It thus appears that at least some PAH compounds are accumulated
by a variety of aquatic organisms; however, so far the metabolism of these
compounds has been demonstrated only in bacteria and fish.
Birds and Mammals
We did not find any report on concentrations of PAH compounds
in other than experimental animals.
Gorelova and associates (1971) reported only a trace and, in
many cases, no detectable levels of 3,4-benzopyrene in the muscle, fat,
liver, or blood of rabbits, pigs, cows, chickens, or ducks, or in the
milk of the mammals or eggs of the birds that were given an unspecified
amount of the compound in the diet for up to one year. Cherepanova (1971)
fed the same kind of animals up to 10,000 |j,g of 3,4-benzopyrene per day
for an unspecified time and found benzopyrene levels of no more than
0.26 ng/kg in the muscle, fat, and liver. Eggs contained no more than
0.007 |o,g/egg, and milk contained no more than 0.01 |j,g/liter.
When applied to the skin of mice or rats, known carcinogenic
PAH compounds penetrate the skin more readily than non-carcinogenic ones,
and are eliminated more slowly from the body. Grimm and Oehlert (1966)
came to these conclusions in a study using radiolabeled 1,2,3-dibenz-
anthracene and 1,2-benzopyrene, both of which are non-carcinogens, and
3-methylcholanthrene and 3,4-benzopyrene, both of which are known carcin-
ogens. They found no difference in the distribution of either type of
compound in the animals: but observed that radioactivity in rat skin
declined at a faster rate than in mouse skin. Accumulation of other
PAH compounds does not appear to have been studied.
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l-hydroxy-2-naphthoic acid. 1,2-Dihydroxynaphthalene is then metabolized
to cis-o-hydroxybenzalpyruvate (Davies and Evans 1964).
Evans and coworkers (1965) also proposed that anthracene is
metabolized by soil pseudoraonads to 2,3-dihydroxynaphthalene via several
intermediates , including trans-1,2-dihydro-l,2-dihydroxyanthracene
(Colla , et al. , 1959), 1,2-dihydroxyanthracene, and 2-hydroxy-3-naphthoic
acid, which is eventually metabolized to salicylate (Colla, et al., 1959;
Rogoff and Wender 1957) . The oxygenase responsible for the cleavage of
all o-dihydroxyphenol derivatives appears to be catechol-2,3-oxygenase,
a constitutive enzyme of Pseudomonas sp. (Evans, et al., 1965).
l-Hydroxy-2-naphthoic acid was also identified as a microbial
metabolite of phenanthrene by Kaneko and coworkers (1968, 1969). They
also reported (1969) that Pseudomonas is capable of metabolizing salicylic
acid and catechol, which are considered products of phenanthrene and
anthracene metabolism.
Biosynthesis
Graef (1966) reported 3 to 5 times more fluoranthene, 3,4-benzfluor-
anthene, indeno(l,2,3 ,cd)pyrene, 1,2-benzperylene, and 3 ,4-benzopyrene
in beech, oak, and tobacco leaves that were turning yellow than in green
leaves collected at the same time, and hypothesized that these polycyclic
aromatic hydrocarbons are synthesized by the plants. To test this hypo-
thesis, he grew rye, wheat, and lentils from seeds in a system free of
3,4-benzopyrene and found as much as 3.8 (j,g of 3,4-benzopyrene per 100
grams of plant sample after the seeds had sprouted. From this study he
concluded that plants do indeed synthesize benzopyrene.
In a study by Hancock and coworkers (1970), plants along a railroad
and from a control area were analyzed for anthracene, fluoranthene, pyrene,
benz(a)anthracene, and benzo(a)pyrene. They found higher levels of these
compounds in plants from the control area and, like Graef and Diehl (1966)
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observed no seasonal change in benzopyrene-pyrene ratios in the leaves
although they expected that if pyrene were from an exogenous source, it
would undergo rapid photodegradation particularly during the summer,
and thus cause a change in ratio. From these observations, they concluded
that the PAH compounds found in the plants were synthesized.
Experiments by Borneff and associates (1968a,b) demonstrated that
the alga, Chiorella vulgaris was capable of synthesizing fluoranthene,
benz(a)anthracene, benz(b)fluoranthene, benzo(a)pyrene, benz(ghi)perylene,
benz(k)fluoranthene, and indeno(l ,2 ,3,cd)pyrene.
Although these studies strongly indicate that PAH compounds found
in plants can be of endogenous origin, Grimmer and Duevel (1970) did not
find any benzo(e)pyrene, benzo(a)pyrene, perylene, anthracene, benz(ghi)-
perylene, dibenz(a ,h)anthracene, or coronene in plants grown in green-
houses in which the air was supplied through special filters.
Biosynthesis of PAH compounds has been demonstrated in the bacteria
Clastridium cultured in the presence of lipid extracts from marine
plankton (Mallet, et al., 1967), in Bacillus badius cultured in the
presence of lycopene, naphthelenic acid, and vitamin.K (Niaussat, et
al. , 1970a) , and in Welchia sp. (Brisou 1969).
Synthesis of PAH compounds by multicellular animals has not been
demonstrated.
Biological Activity
The recent literature on the biological activity of PAH is rather
heavily weighted toward carcinogenic and cocarcinogenic aspects. In
accord with the limited objectives of this literature study, attention
was not directed to such references unless they were specifically
oriented toward structure-activity relationships or were obviously
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pertinent to that subject. In contrast, the recent literature on PAH
metabolism received much greater attention because of the current
evidence that metabolic transformation is intimately involved with
mechanisms of carcinogenicity and, therefore, with structure-activity
considerations and other aspects of toxicity. For similar reasons,
biochemical and immunological effects of PAH received special attention
as did studies of absorption, distribution, and binding and reports of
the biological effects of various transformation products of PAH.
Biological Effects
Many of the recent studies of the effects of PAH on sensitive
receptors other than man have been concerned with differentiating between
carcinogens and non-carcinogens. Examples include inhibition of RNA
virus replication (deMaeyer 1964, Hsu 1966), stimulation of rat liver
ribosomal protein and RNA synthesis (Hradec 1967) , immunosuppression in
the mouse (Stjernsward 1965, 1966) , induction of chromosomal breaks
(Rees 1970), enhancement of E. coll cell sensitivity to ultraviolet
irradiation damage (Mirsov 1973) , and growth promoting effects in plants
(Graef and Nowak, 1966).
Biochemical studies of carcinogenic PAH indicate that these can
inhibit a variety of plant, bacterial, and mammalian enzyme systems
(Gemant 1967, Konstantinova 1973, Vysochina 1974, Lillich 1972) and
repress tail regeneration in the newt (Pizzarello 1966, also p. 49 this
report). Plant damage following application to leaves, however, appears
to be due to products formed by photooxidation (Halbwachs 1968a ,b).
Interestingly, non-carcinogenic PAH may inhibit some effects of carcino-
genic PAH (Hsu 1966).
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Absorption, Distribution, and Binding
Absorption studies, involving primarily benzo(a)pyrene, have
demonstrated uptake by microorganisms (Mallet 1965, Moore 1965),
transplacental passage in mice (Shendrikova 1974) and inhibitory
effects of soot and aerosol treatments on intratracheal absorption,
removal, and elimination, with a resultant enhancement of carcino-
genicity locally (Dontenwill 1968). Other absorption sites studied
include mouse and rat skin (Grimm 1966, Sezaki 1963) and the rapid
passage of PAH into lymph following intestinal absorption (Rees 1971,
Mandelstam 1969). The absorption of various PAH is probably very
similar although some differences between carcinogenic and non-carcin-
ogenic compounds have been claimed (Grimm 1966). Furthermore, the
uptake, distribution, metabolism, and binding to protein of one PAH
such as benzo(a)pyrene can be altered by the presence of a second PAH
such as phenanthrene or 3-methylcholanthrene (Flesher 1973, Anghileri
1967).
Binding of PAH to DNA appears to involve both intercalation
(Kodama 1966, Craig 1970) and covalent bonding, which is dependent on
metabolic activation (Kaufman 1973, Blackburn 1971); while binding of
benzo(a)pyrene is enhanced by vitamin A deficiency. This can be
counteracted by an inhibitor of the aryl hydrocarbon hydroxylase system,
which reduces the ability of cells to metabolize PAH (Genta 1974).
Alkyl substitution (7,12-dimethyl) appears to enhance DNA binding of
benzo(a)anthracene (Yuspa 1970). While binding is also enhanced by
ultraviolet irradiation of PAH, the significance of this method of
activation to studies of relative carcinogen!city as a function of DNA
binding is not clear (Blackburn 1971, Pascal 1971). Presumably, reactive
intermediates of carcinogenic PAH are important in covalent bonding
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since the final photooxidation products of benzo(a)pyrene seem not to be
tumorigenic (Gubergrits 1974) ; photoirradiation s'tudies demonstrate
covalent bonding by 3,4-penzopyrene to DNA with no such bonding by non-
carcinogenic 1,2-benzopyrene (Maevskii 1973).
Pertinent to carcinogenic activity and chronic toxicity is the
- A^ fact that body fat absorbs large amounts of these hydrophobic compounds
y and they exhibit prolonged retention in fat, adrenals, and ovaries
(Daniel 1967).
Physio-Chemical Correlates of Activity
Investigators have attempted to define physico-chemical (i.e., non-
biological) phenomena which correlate theoretical chemical properties
with carcinogenic or cytotoxic activities of PAH. These include posi-
tional reactivity toward ozonation (Moriconi 1968), free radical photo-
generation or production in tissues (Okazaki 1971, Inomata 1972, Nagata
1966, Kotrikadze 1974, Rondia 1967), intermolecular electron transfer
(Kavetskii 1966) , one-electron oxidation to radical-cation intermediates
and reaction of these with nucleotide bases (Wilk 1966, 1972), electro-
chemiluminescence (Kozlov 1967a, 1970; Mikhailovskii 1967), interactions
with lipid monomolecular films (surface tension data) (Felmeister 1972),
and semiconductor properties (Drost 1966).
Metabolism and Biological Mechanisms
A great deal of evidence exists linking biotransformation of PAH
to their carcinogenic and cytotoxic properties. It is well known that
the microsomal enzyme systems concerned can be induced or stimulated
by a variety of drugs, insecticides, etc.; PAH are especially effective
inducers, which substantially increase microsomal protein synthesis and
alter rates of metabolism of endogenous substrates and PAH.
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Considering the extremely low aqueous solubilities of PAH, biological
transport probably depends on solubilization by albumin and other organic
plasma and cellular constituents with a resulting facilitation of meta-
bolism (Alvares 1970). Recent studies have demonstrated similar PAH
metabolism by mouse fetal and placental tissues (Guibbert 1972) , guinea
pig alveolar and peritoneal macrophages (Tomingas 1971), Syrian golden
hamster (Dontenwill 1968b) , mouse embryonic fibroblasts (Belitskii 1970) ,
and cultured human lymphocytes (Booth 1974) as well as by mice and rat-
liver microsomes. In addition, there is ample evidence of metabolism
by plants, microorganisms, and fish (pp. 53, 56, 57 this report).
PAH such as phenanthrene, benzo(a)pyrene, benzo(a)anthracene, and
methylated analogs are metabolized by microsomal oxygenases to K-region
epoxides followed by conversion by epoxide hydrase to dihydrodiols
(Holder 1974, Sims 1971, Grover 1971a , Sims 1973a, Boyland 1965a) , which
are then conjugated with glutathione (Sims 1973a). Alkyl hydroxylation
also occurs with methyl-PAH (Sims 1970, Gentil 1971).
Several recent studies indicate the importance of metabolic activa-
tion as a prerequisite for cytotoxicity, reaction with nucleophiles ,
macromolecular binding, and carcinogenicity (Gurtoo 1974, Diamond 1970,
Huberman 1971, 1972, Borgen 1973, Sims 1973, Cavalieri 1974, Duncan 1970,
Ahn 1974, Gelboin 1969, Aleksandrov 1974, Flesher 1970). In the case of
methyl-PAH, increased carcinogenic activity may result from metabolic
formation of hydroxymethyl derivatives (Boyland 1965b). Similar conclu-
sions result from studies of microsomal enzyme pretreatment induction
by benzo(a)anthracene and other PAH (Gelboin 1972). Several studies,
however, also indicate that either pretreatment or cotreatment with
various PAH can also decrease carcinogenic and cytotoxic effects of
PAH by stimulation of metabolism (Conney 1966, Argus 1971, Levin 1967)
or competitive inhibition of metabolism (Kunte 1969, Tomingas 1970a,
1970b); organophosphate insecticides also inhibit PAH metabolism (Weber 1974)
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It appears that metabolic formation of epoxy and hydroxy intermediates
is important in the cytotoxic and carcinogenic activities of these compounds,
while rapid further degradation of these intermediates is biologically
protective. The much greater covalent binding of 7,8-dihydroxy-7,8-
dihydroxy-7,8-dihydrobenzo(a)pyrene (Borgen 1973) is indicative of this,
as is the fact the benzc(a)anthracene-5,6-epoxide is much more active in
malignant transformation of embryonic cells than is the parent hydrocarbon
or its phenols or dihydrodiols (Huberman 1972).
Various aspects of PAH metabolism, including formation and metabolism
of epoxide intermediates, are discussed in very recent reviews (Conney
1974, Wiebel 1974, Grover 1974).
Structure-Activity Relationships
During much of the past two decades the Pullman electronic theory
of carcinogenic activity has dominated considerations of structure-
activity relationships among PAH. This concept of reactive, electron-
dense K-region double bonds and relatively inactive L-regions is still
being considered in association with currently more popular ideas of
metabolic activation as well as in its original terms. The theory
remains useful in predicting carcinogenic activity in some series of
unsubstituted PAH when competitive metabolism at the L-region is con-
sidered in conjunction with K-region reactivity (Scribner 1969). Since
both carcinogenic and non-carcinogenic PAH can possess similar K-regions,
it is evident that the simple idea that only the presence of this region
is required for carcinogenicity is invalid (Cavalieri 1971). Theoretical
calculations suggest that the fundamental theory retains some validity
(Meyer 1969, Hoffmann, F. 1969), but fail to define any simple relation-
ships between carcinogenic activity and K or L region reactivity indices
(Sung 1972). Similarly, the relationships between carcinogenicity and
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K and L region additivity with ozone are not clearly defined (Moriconi
1959, 1961, 1968). These difficulties are not surprising in terms of
postulates that substitutions at different positions represent competing
processes of activation for carcinogenesis and detoxification (Scribner
1973) .
The potency of PAH as inducers of microsomal aryl hydrocarbon
hydroxylase can be quantitatively described in terms of hydrophobic
interactions, chemical reactivity, and the ability to participate in
charge-transfer interactions; the critical step in both induction and
carcinogenesis is considered to be the formation of a reactive K-region
(Franke 1973). Additional considerations, however, are relative rates
of metabolism and competing metabolism at K-regions and other loci
(Sims 1970). K-region epoxides of PAH appear to be more active in cell
transformation (Huberman 1972) and more reactive toward nucleic acid
and protein fractions (Grover 1971b) than corresponding hydrocarbons,
K-region dihydrodiols, and phenols. Appreciable differences exist in
the rates at which these epoxides rearrange in neutral solution and are
metabolized further (Swaisland 1973). Thus, in vivo indications of
relatively low carcinogenic activity following administration of such
epoxides (Boyland 1967) may not be indicative of the importance of
these as active metabolites formed in vivo from the parent hydrocarbons.
The importance of the epoxides is further emphasized by the fact that
those derived from potent carcinogens are mutagenic in bacteria even
though the parent hydrocarbons are not (Ames 1972, Cookson 1971).
Among PAH derived from petroleum cracking, carcinogenic potency is
maximal in 4-5 ring compounds, largely benz(a)anthracene and its alkyl
derivatives (Tye 1966a). Monomethyl derivatives of benz(a)anthracene
are carcinogens of varying potency (Stevenson 1965, Roe 1972). These
include the 6-, 7-, 8-, and 12-methyl derivatives, and various dimethyl
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derivatives are also carcinogenic; positions 6,7,8 and 12 in benz(a)-
anthracene are considered to form a "triangle of strong carcinogenicity"
(Huggins 1967, Sugiyama 1973). The carcinogenicity of 4,5,10-trimethyl-
benz(a)anthracene is especially high (Dunning 1968).
No simple correlation was found with regard to ethyl group position
and carcinogenicity in substituted benz(a)anthracenes; 6,8- and 8,12-
diethyl were potent carcinogens while 7,8- and 7,9-diethyl were inactive
(Pataki 1972). Carcinogenic activity in benz(a)anthracenes appears to
depend on at least one relatively flat surface and a geometric resemblance
to nucleic acid base pairs (Pataki 1969).
Methyl substitution in appropriate positions appears to generally
enhance PAH carcinogenicity. In chrysene the result is increased
initiator potency in some cases, but 5-methylchrysene is a complete
carcinogen (Hoffmann, D. 1974). In substituted benz(a)pyrenes mutagen-
Icity decreases in the order 3,6-dimethyl > 3-methyl, 6-hydroxymethyl
> benz(a)pyrene > 1,6-dimethyl (Fahmy 1973); carcinogenicity is in the
order 6-methyl > benz(a)pyrene > 6-carboxaldehyde > 6-hydroxymethyl and
appears to depend on either electron donor or acceptor properties
(Dewhurst 1972).
Structure-activity correlations are claimed with respect to carcin-
ogenicity and photodynamic action in Paramecium (Epstein 1964) and energy
differences between lowest excited singlet and lowest triplet levels from
spectroscopic data (Steele 1967).
Environmental Sources
Air
Polynuclear aromatic hydrocarbons are transported in the atmosphere
adsorbed on particulates and bacteria. Their concentrations are roughly
proportional to the amount of benzo(a)pyrene (BaP) and depend on the
72
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temperature, the amount of sunlight, the traffic, and the geography of
location. Urban concentrations tend to be around 10-100 times greater
than nonurban. Olsen (1969) has found that the arithmetic mean for a
3
nonurban location is 0.4 (jg/1000 m and for an urban location is
3 3
3 pig/1000 m . The figure of 0.4 |jg/1000 m can be assumed to be a low
and safe level of benzo(a)pyrene in air. Winter concentrations tend to
be greater than summer concentrations (IARC 1973). Table 16 lists the
winter and summer concentrations for several cities in Europe and the
United States. Location is specified when possible. The higher concen-
tration in winter is probably due to lower rates of photooxidation in
winter (Andelman 1970) and, especially, increased use of fossil fuel for
winter heating.
PAH concentration is also influenced by the amount of automotive
exhaust. The contribution due to traffic is not large, ranging from
5-42% (Sawicki 1967), Concentrations in Sydney, Cincinnati, and Detroit
ranged as shown in Table 17 depending on the traffic. The BaP concen-
trations agree with another review's average BaP concentration of
3
6 |j,g/1000 m for 100 U.S. cities (Sawicki 1967). Another source quoted
the concentrations of the three compounds for six U.S. cities in terms
of grams of organic atmospheric particulates (IARC 1973). Refer to
Table 18 for these figures.
Water
Polynuclear aromatic hydrocarbons find their way to waterways
adsorbed onto aerosols or bacteria (Andelman 1970). Although their
solubility in pure water is essentially zero, they may exist in water
in association with organic matter or colloids (micelles) as formed by
synthetic detergents. An extensive review (Andelman 1970) on water
listed the carcinogenic PAH concentrations in four types of water
resources. These are listed in Table 19. Note that groundwater, in
general, is least contaminated by PAH. This low level results from
73
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Table 16
VARIATIONS IN PAH CONCENTRATIONS WITH SEASONS
3 *•$
(ug/1000 m ) (ug/1000 m )
Benzo(a)pyrene
Chrysene
Benz(a)anthracene
Winter
0.6-104
26 (14 U.S.
cities)
20-361
94 (Siena)
361 (Bochun)
Summer
0.03-4
1.9 (14 U.S.
cities)
2.5-3.6
1.6 (Siena)
136 (Pittsburgh)
Ref.
(lARC 1973)
(Olsen 1969)
(lARC 1973)
(lARC 1973)
74
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Table 17
VARIATIONS OF PAH CONCENTRATION WITH TRAFFIC
/ 3
IUg/1000 m
Benzo(a)pyrene 2.5-6.5
Chrysene 1.8-13.3
Benz(a)anthracene 0.6-13.7
Source: IARC 1973
75
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Table 18
PAH CONCENTRATIONS IN TERMS
OF TOTAL ORGANIC ATMOSPHERIC PARTICULATES
Org. Atmos.
(ug/gm) Particulates
Benzo(a)pyrene 110-670
Chrysene 150-490
Benz(a)anthracene 43-280
Ref: IARC 1973
76
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Table 19
CARCINOGENIC PAH CONCENTRATIONS IN WATER SOURCES
Source (|Jg/l)
Groundwater 0.001-0.1
Treated river and lake water 0.01-0.025
Surface water 0.025-0.100
Surface water, strongly contaminated >0.100
Ref: Andelman 1970
77
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filtration by soil profiles. As a point of reference, 0.017 Mg/1 of max-
imum permissible concentration of carcinogenic PAH has been suggested for
human consumption (Andelman 1970). The World Health Organization has
recommended a maximum of 0.2 |j,g/l PAH calculated as the sum of six easily
identified compounds (Andelman 1970). The limit of 0.0075 pg/1 for the
BaP component of this total was recommended with total carcinogenic PAH
limits of 0.03 pg/1.
Another review has broken down the concentration of three PAH in
water (IARC 1973). These results are presented in Table 20. Note that
drinking water concentrations, when added together, amount to much greater
concentrations than those listed in Table 19. Considering that BaP is
generally said to constitute between 1% and 20% of the total carcinogenic
PAH, the figures in Table 20 are several magnitudes greater than the
recommended allowable drinking water concentrations.
Contaminated waters can have seriously large PAH concentrations.
Andelman (1970) has also quoted BaA concentrations of 0.025-10 n,g/l and
BaP concentrations of 0.001-1.84 |ig/l in industrial and bitumen contaminated
effluents. Water from households, trades, roads, and industrial sources
had up to 31.4 |j,g/l BaA and 34.5 |j,g/l BaP.
Soils
Carcinogenic PAH settle on soil and are absorbed there by micro-
organisms or plants or decomposed by some bacteria. Some of the PAH
found in soil and sediments may be synthesized by plants or organisms
present in the soil.
Soil data are difficult to compare since information has been
compiled by different researchers in different locations using different
experimental techniques. In spite of this difficulty, some concentrations
are listed here in Table 21 by compound and by type of contamination.
78
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Table 20
PAH CONCENTRATIONS IN WATER
Ug/1 Drinking Water ug/1 Surface Water
Benzo(a)pyrene 0.0001-0.023 0.0006-0.114
Chrysene - 0.0118-0.038
Benz(a)anthracene 0.001-0.023 0.0043-0.185
Ref: IARC 1973
79
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Table 21
CONCENTRATIONS OF PAH IN SOILS
Benzo(a)pyrene
Chrysene Benz(a)anthracene
Forest
Up to 1,300
5-20
Non-Industrial
0-127
Towns and
Vicinities
0-939
Soil near
Traffic
Up to 2,000
1,500
Near Oil
Refinery
200,000
Near Airfield
785
Polluted by
Coal Tar Pitch
650,000
600,000
2,500,000
Ref: IARC 1973
80
-------
Note that soil directly contaminated by fossil fuel sources such as oil
and coal-tar pitch tends to have concentrations several magnitudes
greater than the other soils. Note also that a forest sample contained
up to 1300 y,g/kg, whichis almost as much as the levels found near traffic.
A study done in Russia found 837» of soil samples to contain less
than 3 ug/kg of BaP. Podzolic soils had 0.7-0.8, soddy carbonate soils
11-13, Moscow city soils 269-347, and nearby Moscow freeway soils 16-67
|j,g/kg (Shabad 1971b) . These values are quite a bit lower than those
listed in Table 21.
Natural Sources
The sources of PAH that occur naturally in the environment were
classified into three categories: plants, food (fresh and processed),
and fossil fuels. In general, the benzo(a)pyrene content of dry organic
substances is 10-20 p,g/kg (Andelman 1970) . BaP constitutes 1-20% of the
total carcinogenic PAH. The environment surrounding these naturally
occurring sources is sediments and soils that also contain PAH. As
examples, consider ancient sediments of limestone and boghead, which
contain 20, 40 p,g/kg, respectively, of BaP. The origin of the PAH in
these sediments is thought to be due to natural forces and plant and
bacteria synthesis, and not due to any pollution (Mallet 1969). Consider
also marine sediments, which contain BaP in the range of 1-5,000 (j,g/kg,
depending on type and depth. These may indicate that certain marine
organisms can concentrate and fix PAH (Andelman 1970, p. 487). The
microorganisms in soils containing a high concentration of BaP—30,000
p,g/kg—will tend to decompose 50-70% of the material. A lower concen-
tration of BaP will not tend to be readily degraded in soils (Khesina
1969).
81
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Plants
Plant seedlings were found to contain 10-20 |ig/kg BaP of dried
material after 8-10 days of growth in a PAH-free environment. Andelman
(1970) also gave a general figure of 10-20 ug/kg BaP in active plant
tissue. The amounts of BaA, BaP, and anthracene were estimated to be
5-110 |j,g/kg of dry plant material for each of 3 PAH (Hancock 1970) . A
German researcher found the BaP concentration of dried leaves to be
8-40 |j,g/kg (Graef 1966a) . Various bacteria also concentrated BaP
through synthesis in amounts of 2-10 |j,g/kg of dried material (Andelman
1970) . Marine plants such as algae contained carcinogenic PAH in the
range of 10-50 |j,g/kg. The BaP concentrations in tobacco leaves were
determined to be 103 |j,g/kg and, after processing, 113 |j,g/kg (D'Arrigo
1972) . Even higher concentrations for unsmoked tobacco of 54-270 |j,g/kg
were found (Andelman 1970).
Foods
A lot of concern has surrounded the concentration of carcino-
genic PAH in the food chain. The voluminous literature reflects efforts
to determine the concentrations of these compounds in all fresh food
groups and certain types of cooked and processed food. Most information
was found for the compounds BaA, BaP, and chrysene. Most of the values
reported were determined by different researchers and are, therefore,
difficult to compare. Consider, firstly, the cereals and tubers food
group in Table 22. The concentrations of the three PAH are pretty much
the same. Note that the peelings in potatoes tend to have higher con-
centrations of PAH. Wheat and oat husks also have a great deal of BaP
since the BaP concentrations of wheat and oats were found to decrease
60% and 40%, respectively, by simply removing the husks (Rohrlich 1971).
Vegetable and fruit concentrations of PAH are in agreement with the
general plant concentrations discussed under "Plants." Table 23 lists
82
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Table 22
PAH CONCENTRATIONS IN CEREALS AND TUBERS
Benz(a)anthracene
Cereals j^g/kg Potatoes Ug/kg
In general
0.4-6.8
Ref.
IARC 1973
Chrysene
Benzo(a)pyrene
In general
0.8-14.5
In general Peelings 0.36
0.25-0.84
Tubers 0.09
IARC 1973
Shabad 1972
Barley, wheat, rye
0.2-4.1
Grimmer 1968
83
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Table 23
PAH CONCENTRATIONS IN VEGETABLES AND FRUITS
(/Llg/kg)
Cabbage
Benz(a) -
anthracene
Chrysene
/ \ b
Benzo(a)- 24.5
pyrene
Other
Kale Spinach Lettuce Tomatoes Fruits Salad
a a a a
43.6- 16.1 0.3 4.6-
230 15.4
a a a a
58.5- 28.0 0.5 5.7-
395 26.5
c c c c a
12.6, 7.4 2.8- 0.22 2-8
24.5 12.8
a a
12.6- 7.4
48.1
0.2
2.8-
5.3
IARC 1973
Grimmer 1965
"Grimmer 1968
84
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the BaP, BaA, and chrysene concentrations for selected vegetables and
fruits. Note that leafy vegetables have quite a bit of PAH with kale
having the highest concentration of each of the three PAH. Dairy pro-
ducts such as milk and butter were found to contain essentially no BaP
(Grimmer 1968). Table 24 lists PAH concentrations in cooked and smoked
meat and fish. Note that smoking the meat or fish increases the carcin-
ogenic PAH content. This is probably due to pyrolytic synthesis of PAH
during the smoking process (Wierzchowski 1972) .
PAH concentrations in beverages such as teas, coffee, and
whisky are listed in Table 25. It was found that fresh food concen-
trations were generally in agreement with plant concentrations as quoted
under "Plants." Cooking, baking, and processing of food tends to increase
PAH levels, as was seen for smoked meat and fish and oils and fats (see
Table 24). Note the high concentrations of the individual PAH in coco-
nut oil and fat.
Fossil Fuels and By-Products
Fossil fuels such as coal (IARC 1973) seem to have low BaP
concentrations. Their by-products tend to have concentrations several
magnitudes greater depending on the rate and temperature of processing.
It is well known that pyrolysis of organics leads to the formation of
PAH (IARC 1973; see also "Formation of PAH"). It follows, therefore,
that products formed under high temperatures such as coal tar, coal tar
pitch, petroleum asphalt, and creosote have unusually high concentrations
of PAH. Table 26 gives a list of these concentrations of BaA, BaP, and
chrysene.
A petroleum distillation product, such as hexane, was found to
contain 280 and 23 p,g/kg of BaA and BaP, respectively. Shale oil BaP
was found to be amazingly low, 0.1 |j,g/kg, probably because shale oil
processing causes the PAH to stay with the spent shale. PAH concentra-
tions may also depend on processing--the TOSCO process is claimed to
85
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Table 24
PAH CONCENTRATIONS IN
COOKED, SMOKED, AND PROCESSED FOODS
(fig/kg)
Benzc(a)-
pyrene
Refined Oils
or Fats
0.9-15a
Fresh Fish
Frozen or Salted
< o.ib
Broiled meat
or Fish
a
meat and
sausages
0.17-0.63
Smoked Meat/
Smoked Fish Sausages
1.0-78.0
0.02-107
Chrysene
margarine
0.2-6.8a
coconut oil
43. 7a
coconut fat
a
62
0.5-129
BBQ meat
2.6-11.2
a
fish
0.9
f
8.7-27.2
a
ham
0.5-2.6
fish 4.3a
meat and
sausages
0.5-2.6
a
BBQ meat
0.6-25.4
37
0.1-0.8
traces-2.1
0.3-173
Benz(a)-
anthracene
0.5-13.5
meat and
sausages
0.2-1.1
ham - up
a
to 12
coconut oil
98"
coconut fat
125a
charcoal
a
broiled
1.4-31
0.02-189
IARC 1973
b
Gorelova 1974
"Wierzchowski 1972
Andelman 1970
"Grimmer 1968
Shirotori 1972
86
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Table 25
PAH CONCENTRATIONS IN BEVERAGES
Benzo(a)pyrene
Roasted Coffee
0.3-0.5
0.1-4b
a
Teas
3.7-3.9a
3.9-21.3b
Green teas
0.5-16
Whisky
0.04
Chrysene
0.6-19.1
4.6-6.3
0.04-0.06
Benz(a)a nth ra cene
0.5-14.2
0.04-0.08
Grimmer 1968
IARC 1973
87
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Table 26
FOSSIL FUEL AND ITS DERIVATIVES
(|ag/g)
Benzo(a) -
pyrene
Chrysene
Benz(a) -
anthracene
Coal Coal tar
300-1000 30 ,000
Up to
2,860
Up to
6,980
Coal tar Petroleum
pitch asphalt
12,500 0.1-27
Up to Up to
10,000 0.4-34
Up to Up to
12,500 35
Creosote
oil
0.00014
0.0002
Up to
1,340
Up to
2,940
Ref: IARC 1973
88
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make more PAH than other alternatives. In comparison with coal tar,
BaP concentration for wood tar was found to be only 0.34 p,g/kg (Andelman
1971). Note the much larger concentration of BaP as compared with BaA
in coal tar. Although carcinogenic concentrations in fossil fuels are
not excessive, their derived products after processing under high
temperatures accumulate dangerous amounts of PAH.
Anthropogenic Emissions and Effluents
PAH are formed under high-temperature pyrolysis of organic matter
("Formation of PAH"). The amount of BaP formed, for example, depends on
how reducing the combustion atmosphere is. With increasing air-to-fuel
ratios, BaP decreases in concentration (Lavrov 1972). PAH formation
also seems to be associated with higher plants which contain more complex
phenolic compounds such as lignin, but other types of organics can also
produce PAH ("Formation of PAH1') . Greater PAH formation rates are
associated with coal combustion than with other fossil fuels. As
evidence for this, the city of Budapest from 1965 to 1970 showed a
decrease in BaP concentrations due to change from coal to oil (Kertesz-
Saringer, 1972a). BaP in air is adsorbed on soot particles and is pre-
ferentially adsorbed on the smallest particles (Masek 1973). PAH are
not soluble in water but exist also adsorbed on solid surfaces (McGinnes
1974),
Stationary
Power Plants—Table 27 gives a summary of the numbers found in
the literature for heat generation, BaP is in considerably greater con-
centration than BaA in a coal-fired installation and emissions from a gas
power plant tend to be much lower. It was not specified, for the stack
gas emission reported, whether the power plant was oil, coal, or gas
fi red.
89
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Table 27
HEAT GENERATION IN A COAL-FIRED INSTALLATION
PAH
Benz(a)anthracene
Coal
19-3,9008
Btu
Gas
Stack Gas
Benzo(a)pyrene
19-400,000
p.g/106 Btu
20-200
|_lg/106 Btu
3 3
0.32 mg/10 m
a
IARC 1973
Sawicki 1967
90
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Industry—As expected, emissions and effluents from various
industries are quite large, especially if they burn by-products of
fossil fuels as fuels. Table 28 gives a summary of concentrations of
three PAH from various industrial processes. While emissions from gas
works are in a range comparable with those from coal power plants, note
the excessive emissions from coal-tar pitch combustion. Note also that
these emissions are more than 20-30 times those from coking plant ovens.
Other industries are also major sources of PAH. Foundries
3 3
were found to emit 1-3 mg BaP/10 m from the casting operations, depend-
ing on the temperature (Zdrazil 1965). An aluminum plant was found to
emit 10 kg of BaP a day or 0.1 |j,g/sq. mile/day on the ground in the
plant area (Olsen 1969). A fiberboard works pitch boiling plant was
found to emit 1.2; on the premises, 0.2; at 100 meters, 0.1; and at
3 3
500 meters from the plant, 0.05 mg/10 m (Bolotova 1967). A carborundum
works crushing plant emission had 0.08, coke furnaces emission 0.06, and
3 3
at 500 meters away from furnace 0.01 mg/10 m of BaP. A vinyl phono-
graph records plant emitted 5.2 and a rubber products plant, depending
3 3
on distance from source, 0.05-0.02 mg/10 m BaP (Bolotova 1967).
In summary, high-temperature processes as found in gas works,
coking and especially coal-tar pitch installations are heavy emitters
of carcinogenic PAH. Other industrial processes using organic substances
such as (poly) vinyl chloride and rubber can be expected to emit PAH to
a lesser degree.
Incinerators—Emissions of BaP from various incinerators and
open burning are summarized in Table 29, Municipal refuse incineration
emits less BaP than outdoor burning. This is probably due to the more
complete combustion in an incinerator.
91
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Table 28
CONCENTRATIONS OF PAH FOR VARIOUS
INDUSTRIAL PROCESSES ((jg/m3)
Gas Works
Coal-Tar Pitch
Coking Plant
Benz(a)anthracene
0.8-14 (air
c
from plant)
0.7 (air)
1,300 (ind.
effluents)8
Benzo(a)pyrene
0.18-7.3
(air from
plant)8
0.4 (air)
2,700 (indus-
trial effluents)
159 (in ovens)
1.9 (@400 m)b
6,000 (kettle <<
310°C, 20 cm
from surface)8
1.2-40C
1.3-92d
0.1-1.6e
Chrysene
1,600 (indus-
trial effluents)8
a
IARC 1973
Masek 1971
Masek 1967
Masek 1965
Adamiak-Ziemba 1972
92
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Table 29
BaP EMISSIONS FROM INCINERATORS AND OPEN BURNING
3 3
Type mg/10 m
Garbage 1,400
Auto parts 170
Vegetable matter 14
Municipal refuse 2.6
Open burning (grass, leaves) 4.2
Ref: IARC 1973
93
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Another comparison of the emissions in incinerators and of
open burning for BaA and BaP was made (IARC 1973). Note that the con-
centrations are listed with respect to weight of particulate matter
rather than volume in Table 30. This table confirms the differences
between open burning and municipal refuse incineration.
Since PAH compounds are produced when hydrocarbons are pyrolyzed
("Formation of PAH"), internal combustion engines associated with auto-
mobiles, trucks, airplanes, and railroads should be a source of these
compounds. Jet airplanes should also contribute PAH compounds to the
environment. The amount and type produced should be a function of fuel,
engine type, and engine duty. Under heavy loads or fuel-rich conditions
where combustion is not complete, PAH generation rates will be higher
than for light loads or fuel-lean conditions. The PAH compounds produced
will probably be adsorbed on the particulates produced by combustion.
Table 31 shows some PAH levels associated with diesel and
gasoline internal combustion engines. The measurements were made by
different investigators using a different reporting basis so that it is
not possible to draw inferences about the effect of fuel and engine type
from these data.
94
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Table 30
COMPARISON OF PAH LEVELS IN
INCINERATION AND OPEN BURNING a
PAH Municipal Commercial Open
(mg/kg of particulate matter)
Benz(a)anthracene 0.09-0.26 5-210 25-560
Benzo(a)pyrene 0.02-3.3 58-180 11-1100
8IARC 1973
95
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Table 31
PAH IN EXHAUST GAS FROM
DIESEL AND GASOLINE ENGINES*
a
Diesel
Benz(a)anthracene
2.3-15 |ag/m"
exhaust gas
Gasoline
61.7 mg/kg
exhaust gas
(4.2 (_ig/minute)
Benzo(a)pyrene
*-.
0.6-7.4 p.g/nT
exhaust gas
a
31.5 mg/kg
exhaust gas
(2.2-9.6 g.g/minute)
Chrysene
3.6-17 |jg/m
exhaust gas
3 a,b
175 mg/kg
exhaust gas
(12 jjg/minute)
a
IARC 1973
Yakovlev 1975
96
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 560/5-75-009
4. TITLE AND SUBTITLE
The Environmental Fate of Selected Polynuclear
Aromatic Hydrocarbons
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
February 1976
7. AUTHORis) s_ B< Radding) T. Mill, C. W. Gould, D. H. Liu
H. L. Johnson, D. C. Bomberger, and C. V. Fojo
8. PERFORMING ORGANIZATION REPORT NO,
Task Two
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Stanford Research Institute
333 Ravenswood Avenue
Menlo Park, CA 94025
10. PROGRAM ELEMENT NO.
2LA328
11. CONTRACT/GRANT NO.
68-01-2681
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Toxic Substances
Environmental Protection Agency
Washington, D. C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A review of the recent literature on polynuclear (polycyclic) aromatic
hydrocarbons (PAH) has been carried out for general information on PAH and
specific details about six selected PAH. The sources, transport, chemical and
physical transformations, structure-reactivity relationships, and biological
(non-carcinogenic) properties have been reviewed with recommendations for
further research.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
8. JISTRIBUTION STATEMENT
Document is available to the public
through the National Technical Information
Service, Springfield, Virginia 22151 rs
t.lDENTIFiERS/OPEN ENDED TFRMS
Polynuclear aromatic
hydrocarbons, environ-
mental fate, environmental
persistence, ecological
effects, environmental
half-lives
19. SECURITY CLASS (This Report)
unclassified
20. EtECURiTY CLASS (This page)
unclassified
c COSAT
6T, 6F, 6A,
7C, 13B
21. NO. OF
22. PRiCE
EPA Form 2220-1 (9-73)
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