Benzo(a)pyrene

50-32-8

Pale yellow plates or long needles. 
Monoclinic or orthorhombic 
crystals. 
Practically insoluble.

252.3

Adsorption on and movement via the sediment is probably a more
important transport process than volatilization. 
The half-life
for benzo(a)pyrene volatilization was 1500 hr, calculated for a
river 1 m deep, water velocity 0.5 m/second, and wind velocity
1m/second (Sax 1986).

Adsorption: in estuarine water; at 0.003 mg/l, 71 % adsorbed on
particles after 3 hours (Lee 1977).

A one-compartment model that simulated river conditions,
predicted that 83 % or the benzo(a)pyrene would be sorbed onto
suspended solids. 
The same model predicted 71 % sorption in
eutrophic and oligotrophic lakes and 93 % in eutrophic ponds.

The half-life of all fate processes combined including dilution
according to this model ranged from 0.48 hr in a stream to 7.4
hr in an eutrophic lake. 
The percentage of sorbed B(a)P in
various surface waters and wastewaters was 24 - 44 % at 22 °C.

The log of the mean partition coefficient between the suspended
particulates and the water was 4.48 (Sax 1986).

After 3 hours incubation in natural seawater, 75 % of 0.002
mg/l were taken up by suspended aggregates of dead
phytoplankton cells and bacteria (Lee et al. 1978).

Insoluble.

Benzo(a)pyrene is found in coal tar, cigarette smoke, and in    
the atmosphere as a product of incomplete combustion. 
It is 
found in the exhaust soot and tar from gasoline and diesel      
engines. 
It is also found in oil, water, and food. 
Used in      
cancer research.                                                

The most common photooxidation product of PAHs
in solution in an endo peroxide. 
Dealkylation, ring cleavage,
and other reactions ensue following photolysis or pyrolysis of
these peroxides. 
Frequently, only quinones are isolable.

Photodimers may result in some cases. 
Adsorbed PAHs are more
reactive than in solution (Sax 1986).

Ozone and UV irradiation degraded more than half of the pure
benzo(a)pyrene present in a simulated atmosphere after 0.50
hours. 
However, photooxidation in the atmosphere is not as
rapid as predicted from model laboratory studies. 
Detectable
levels of PAHs are usually found in urban atmospheres. -

Benzo(a)pyrene in simulated atmospheres containing 1 ppm
nitrogen dioxide and approximately 10 ppb nitric acid formed
nitro derivatives that were directly mutagenic in the Ames test
(Sax 1986).

Atmospheric photolysis half-life:
0.37hr - 1.1hr,
based upon measured photolysis rate constant for midday winter
sunlight at 35°N latitude in 20% aqueous acetonitrile and
acjusted for approximate summer sunlight intensity
(Howard 1991).

Photooxidation half-life in air:
0.428hr - 4.28hr,
scientific judgement based upon estimated rate constant for
reaction with hydroxyl radical in air (Howard 1991).

Airborne particulate PAHs can persist at relatively high
concentrations in aerosols transported for long distances. 
The
atmosperic persistence is longer than would be predicted from
laboratory photooxidation studies. 
On the other hand, The
National Academy of Sciences (1972) proposed that the chemical
half-life of PAH's in the atmosphere may be limited to hours or
days. 
For example, the half-life for benzo(a)pyrene with ozone
in the gas phase is 870 hours (Sax 1986).

The half-life for photolysis calculated for surface waters in
midsummer at 40 ° N latitude is 0.54hr. 
B(a)P photooxidation in
natural waters depends on water depth and varies seasonally due
to changes in solar radiation, temperature and dissolved
oxygen. 
Because or the lack of solar radiation and oxygen,
photooxidation in sediments is negligible (Sax 1986).

Aquatic photolysis half-life:
0.37hr - 1.1hr,
based upon mesured photolysis rate constant for midday
winter sunlight at 35°N latitude in 20% aqueous acetonitrile
and adjusted for approximate summer sunlight intensity
(Howard 1991).

Photooxidation half-life in water:
8.6d - 431d,
based upon measured rate constant for reaction with
alkylperoxyl radical in water (Howard 1991).

PAHs do not contain groups amenable to hydrolysis (Sax 1986).

Ozone and chlorinating agents oxidize polycyclic aromatic
hydrocarbons to quinones, diacids, and nuclear and side-chain
oxidation products. 
Chlorinating agents also produce
chlorine-substituted derivatives. - 
Oxidation of any PAH by
chlorine and ozone, when used for the disinfection of drinking
water, forms quinones. 
The half-life for the reaction of
chlorine with all PAHs is less than 0.5 hr (Sax 1986).

Oxidation by chromic acid or ozone gives
benzo(a)pyrene-1,6-quinone and benzo(a)pyrene-3,6-quinone.

Further oxidation gives benzanthrone dicarboxylic anhydride
(Sax 1986).

Oxidation of any PAH by chlorine and ozone, when used for the
disinfection of drinking water, forms quinones. 
Chlorinating
agents will also produce chlorine-substituted PAHs as well as
oxidation products. -  
The half-life of benzo(a)pyrene in the
presence of ozone is approximately 1 hour and in the presence
of 0.5 ppm chlorine, 10 minutes (Sax 1986).

Oxidation by RO2 radical is slow and not significant with a
half-life of 96 hr. 
The dissolved portion may undergo rapid
photolysis with a half-life of 1 - 2 hours (Sax 1986).

Microbial degradation to CO2 in seawater at 12 °C in the dark
after 48 hr incubation at 0.016 mg/l: 0 µg/l/day; after
addition of water extract of fuel oil 2, after 24 hr
incubation: 0.00001 mg/l/day - turnover time: 1400 days
(Verschueren 1983).

Biodegradation to CO2 in estuarine water:
conc.           incubation    degradation rate   turnover
mg/l    month   time (hr)    (mg/l/day) x 1000  time (days)
0.005   January    24                 0            -
0.005   June       24                 0            -
0.005   May        96               0.002        3500
(Lee 1977).

Degradation in seawater by oil oxidizing microorganisms (in
presence of 0.365 mg/l pyrene and 0.35 mg/l fluorene at 10 °C):
initial conc. 0.190 mg/l; after 12 days: 0.090 mg/l: 53 %
decrease (McKenzie & Hughes 1976).

Aerobic half-life:
57d - 1.45yr,
based upon aerobic soil die-away test data at 10-30°C
(Howard 1991).

Anaerobic half-life:
228d - 5.8yr,
scientific judgement based upon estimated
unacclimated aqueous aerobic biodegradation half-life
(Howard 1991).

Soil systems provide better conditions for biodegradation than
do aquatic systems. 
The rate and degree of degradation is
greatest when the soil and its microbial population has been
acclimated. 
Mycobacterium rubrom and M. flavum metabolized
approximately half or the compound within 4 days. 
Strains
ofbacteria from highly contaminated soil could metabolize 75 -
86 % or the B(a)P within 5 days, Bacteria from less
contaminated soil metabolized 48 - 59 % within the same time
period. 
It has been claimed that soil microorganims decompose
B(a)P when present at high concentrations (30 ppm), but that
B(a)P is not readily degraded when concentrations are lower
(Sax 1986).

Degradation is soil: 82 % after 8 days (soil + adapted
bacteria) (Lee & Takahashi 1977).

Biological degradation in sea water (10 °C): 53 % after 12 days 
(McKenzie & Hughes 1976).

PAHs deposited in sediments are less subject to photochemical
or biological oxidation, especially if the sediment is anoxic.

Sedimentary PAH is therefore quite persistent and may
accumulate to high concentrations (Sax 1986).

Average degradation by soil bacteria after 8 days culture:
                          amount of extracted   amount of B(A)P
                             B(a)P mg           destroyed (%)
_______________________________________________________________
soil not inoculated with
bacteria (control)              0.191               0
soil + N 5 bacterial strain     0.090              53
soil + N 13 bacterial strain    0.061              66
soil + N 13 bacterial strain*   0.033              82
_______________________________________________________________
*before the experiment this strain was cultured in a medium
containing B(a)P for 110 days (Poglazova et al. 1967).

Degradation of benz(a)pyrene:
*------------------------------------------------------------*
ENVIRONMENT  INIT.CONC   REDOX-       TEMP   DEGRADATION  REF.
                mg/l     COND.        °C     %/day
*-------------------------------------------------------------*
sediment        1.25     aerobic      30       6.3/37      a
sediment        1.25     anaerobic    30       0.09/37     a
sediment        7        aerobic       -       0/1         b
sediment       17        aerobic      20       0.84/7      c
sand            7.6      aerobic      20       1.4/7       c
sand            9.5      aerobic      20       1.2/7       c
soil            1        aerobic       -      13/25        d
soil            5        aerobic       -       6/25        d
soil           10        aerobic       -       3/25        d
soil (adapted)  1        aerobic       -      23/25        d
soil (adapted) 2.5       aerobic       -      20/25        d
soil (adapted) 5         aerobic       -      30/25        d
soil (adapted)10         aerobic       -      10/25        d
soil           9.5       aerobic       -      33/90        e
soil         545         aerobic       -      71/90        e
soil (adapted)28.5       aerobic       -      52/90        e
soil           0.06      aerobic      28      66/8         f
soil           0.09      aerobic      28      53/8         f
soil (adapted) 0.09      aerobic      28      82/8         f
*-------------------------------------------------------------*
a) Delaune et al. 1981          d) Löw 1983
b) Herbes 1981                  e) Khesina et al. 1969
c) Gardner et al. 1979          f) Poglazowa et al. 1967
(Anon 1987b).

Above-ground parts of plants contain more B(a)P than
underground parts. 
The concentration is directly proportional
to exposure time during the growing season and surface area of
the plant (Sax 1986).

There are large differences among aquatic species in their
ability to absorb and assimilate PAH from food. 
Polychaete
worms have a very limited ability; fish show limited and
variable absorption from the gut; and crustaceans readily
assimilate PAH. 
Assimilated PAHs are metabolized and excreted
rapidly. 
For biomagnification to occur, a substance must be
relatively resistant to metabolism or exretion (Sax 1986).

Callinectes sapidus, half-life < 2 days (Lee 1976).

Half-life in Mytilus: 16 days (Knutzen & Skei 1988).

B(a)P is metabolized to approximately 20 primarily and
secundarily oxidized metabolites and many conjugates. 
Many
metabolites induces mutagenicity, cell alterations and/or binds
to cellular macromolecules (IARC 1984).

Bioconcentration factor (mollusca):
190, 2 days, Crassostrea virginica
3000, 8 days, Crassostrea virginica
(Lee et al. 1978).
861, Macoma inquinata, 7d 
8.7, Rangia cuneata, 24hr
(Sax 1986).

Bioconcentration factor (crustaceans):
242, 2d, Callinectes sapidus (Lee 1976).

Bioconcentration factor (other):
28200, aquatic organisms containing 7.6 % lipids, estimated (Sax 1986).

Besides producing malignant tumors in laboratory animals,
benzo(a)pyrene damages the lymphoid system, induces
tracheobronchial epithelial proliferation and cell hyperplasia
without necrosis or inflammation, and suppresses the immune
system. 
Dosed rodents show tissue destruction in the pancreas
and liver, and abnormal sperm (Sax 1986).

PAHs can presumably be absorbed from ingestion, inhalation and
skin contact (Sax 1986).

Skin and eye irritation data: skn, mus, 0.014 mg, mild (Sax
1986).

Carcinogenicity: positive (McCann et al. 1975).

Strongly carcinogenic. 
B(a)P is a complete carcinogen,providing
both initiating and promoting stimuli. 
Benzo(a)pyrene produced
tumors in all of the animal species for which data were
reported in 1973. 
Different administration included oral, skin,
and intratracheal routes. 
Its carcinogenic effect is both local
and systemic. 
It produced local sarcomas in subhuman primates
after repeated subcutaneous injections and lung carconomas
after intratracheal instillation. 
In addition,
it initiated skin carcinogenesis in mice and proved
carcinogenic after single doses and prenatal exposure. 
B(a)P
has also induced tumors in salivary glands, pancreas,
subcutaneous tissues, mammary grands, uterus, vagina, kidney,
brain, and thymus (Sax 1986).

Mutagenicity in the Salmonella test: positive;
121 revertant colonies/nmol
2398 revertant colonies at 0.005 mg/plate
(McCann et al. 1975).

Mutagenicity: induced significant mutation to 8-azaguanine
resistance in Salmonella typhimurium at concentrations as low
as 0.004 mM (Krishnan et al. 1979).

Mutagenic to mice and bacteria. 
Cell cultures of many species
including man show inhibition of DNA synthesis after treatment
with B(a)P. 
Certain metabolites of B(a)P, especially the diol
epoxides, are much more mutagenic in Salmonella typhimurium
TA98 and chinese hamster V79 cells than B(a)P itself. 
B(A)P was
found to be positive in the sister chromatid exchange test,
weakly active in the chromosome aberration test, and negative
in the micronucleus test (Sax 1986).

Mutagen data:
mmo, sat, 0.333 mg/plate;
mrc, esc, 0.070/well;
dnr, ocs, 0.100 ml/plate;
dnd, omi, 11 ng/l;
dnd, sal, tes, 0.005, 1 H-C;
msc, ofs, fbr, 5 mg/l;
dnd, hmn, oth, 1500 nmol/l;
dnd, hmn, lng, 0.001 mmol/l
(Sax 1986).

Polychlorinated PAHs are probably highly toxic to aquatic
organisms and persistent in the environment as are
polychlorinated biphenyls and polychlorinated naphthalenes.

Chlorination for purification of wastewaters or drinking waters
containing high concentrations of PAHs may be inadvisable.

Activated sludge treatment is unable to oxidize PAHs within
normal retention times. 
Since large PAHs are insoluble in
water, either they do not support bacterial growth or growth
may be extremely slow. 
The problem has been somewhat overcome
by use of other carbon sources to stimulate (or induce)
bacteria. 
Apparently, long-term exposure of microbes is
necessary before a bacterial population is capable of degrading
PAHs (Sax 1986).

Ctenopharyngodon idella; Cyprinus carpio; Tinca tinca: 10
mg/kg, 2 days, cytogenetic effect (changes in the RNA and DNA
of the cell) (Al-Sabti 1986).

Lepomis macrochirus; 0.005 mg/g, 3 days, biochemical effect
(change in physiochemical process including glycogen
uptake,cholesterol levels and lipid analysis)
(Shugart et al. 1987).

Salmo gairdneri; 0.63 mmol, 6 days, biochemical effect(change
in physiochemical process including glycogen uptake,
cholesterol levels and lipid analysis).

(Miyauchi & Uematsu 1987).

Ictalurus nebulosus; 4 d, 0.005 - 0.025 mg/g, cytogenetic
effect (Metcalfe 1988).

Lepomis macrochirus, 10 d, 0.001 - 0.020 mg/g, enzyme effect
(Jimenez & Burtis 1988).

Poeciliopsis monacha, 1 d, 0.8 - 1.0 mg/l, enzyme effect;
Poeciliopsis sp, 1 d, 3.75 mg/l, lethal effect
(Goddard et al. 1987).

Lethal threshold concentration (LT50):
Daphnia magna; 0.0015 mg/l, 0.19 days (Newsted & Giesy 1987).

Pimephales promelas; 0.0056 mg/l, 1.67 days (Oris et al. 1987).

Acute toxicity to fish:
High molecular PAH (B(a)P, chrysene) have generally low acute
toxicity, probably due to their low solubility (Neff 1979).

Chronic toxicity:
Chronic toxicity (carcinogenicity, mutagenicity,
teratogenicity) is a concequence of high activated, soluble
metabolites of B(a)P via covalent bindning to cellular
macromoleculs (Heidelberger 1976).

The growth of algae is stimulized by low concentrations of
B(a)P (0.01 - 0.1 mg/l) (Graf & Nowak 1966, Boney & Corner 1962)

Manufacturing source: coal tar processing; petroleum refining;
shale refining; coal and coke processing kerosene processing;
heat and power generation sources. 
Natural sources: quantities
synthesized by various bacteria:
of B(a)P produced per kg of
species                              dry bacterial biomass
Mycobacterium smegmatis                   0.060
Proteus vulgaris                          0.056
Escherichia coli (strain 1)               0.050
Escherichia coli (strain 2)               0.046
Pseudomonas fluorescens                   0.030
Serratia marcescens                       0.020
Synthesized by algae Chlorella vulgaris.

Man caused sources (air and water): combustion of tobacco,
combustion of fuels; present in run off containing greases,
oils, etc.; potential roadbed and asphalt leachate.

(Verschueren 1983)

> 10 % of to atmosphere emitted B(a)P goes to water environment
(Neff 1979).

Microbial degradation to 9-hydroxybenzo(a)pyrene and acids
(Gibson 1976b).

Degradation products with special interest:
benzo(a)pyrenequinones; 9,10-epoxy-7,8-dihydrozybenzo(a)pyrene;
B(a)P-dihydrodioles; B(a)P-diolepoxides; B(a)P-oxides
(USEPA 1980).