United States
Environmental Protection
Agency
Office of Water
4601
EPA811-F-95-003e-T
October 1995
National Primary Drinking
Water Regulations
Benzo(a)pyrene
CHEMICAL/ PHYSICAL PROPERTIES
CAS NUMBER: 50-32-8
COLOR/ FORM/ODOR:
Pale yellow needlelike crystals, FAINTLY
AROMATIC
M.P.: 179-179.3° C B.P.: >360°C
VAPOR PRESSURE: >1 mm Hg at 20° C
. DENSITY/SPEC. GRAV.: 1.35at15°C
OCTANOL/WATER PARTmoN (Kow):
Log Kow = 6.04
SOLUBILITY: 0.0038 mg/L of water at 25°
• C; very low solubility in water
SOIL SORPTION COEFFICIENT:
Log Koc =6.6 to 6.8; very low mobility
in soil
ODOR/TASTE THRESHOLDS: N/A
BlOCONCENTRATION FACTOR:
BCFs range from <1 to 2675 in fish;
expected to bioconcentrate in aquatic
organisms which are unable to metabo-
lize it.
HENRY'S LAW COEFFICIENT: .
N/A; volatilization not significant
TRADE NAMES/SYNONYMS:
3,4-Benz(a)pyrene; BaP; BP
DRINKING WATER STANDARDS
MCLG: zero mg/L
MCL: . 0.0002 mg/L -
HAL(child): none
HEALTH EFFECTS SUMMARY
Acute: EPA has found polycyclic aromatic hydrocar-
bons (PAHs) similar to benzo(a)pyrene to potentially
cause the following health effects from acute exposures
at levels above the MCL: red blood cell damage, leading
to anemia; suppressed immune system.
Drinking water levels which are considered "safe" for
short-term exposures have not been established at this
time.
Chronic: Benzo(a)pyrene has the potential to cause
the following health effects from long-term exposures at
levels above the MCL: developmental and reproductive
effects.
Cancer; There is some evidence that benzo(a)pyrene
has the potential to cause cancer from a lifetime expo-
sure at levels above the MCL.
USAGE PATTERNS
Benzo(a)pyrene is one of a group of compounds called
polycyclic aromatic hydrocarbons (PAHs), or polynuclear
somatic hydrocarbons (PNAs). They are not produced
or used commercially but are ubiquitous in that they are
formed as a result of incomplete combustion of organic
materials.
RELEASE PATTERNS
PAHs are found in exhaust from motor vehicles and
other gasoline and diesel engines, emission from coal-,
oil-, and wood-burning stoves and furnaces, cigarette
smoke; general soot and smoke of industrial, municipal,
and domestic origin, and cooked foods, especially char-
coal-broiled; in incinerators, coke ovens, and asphalt
processing and use.
There are two major sources of PAHs in drinking water:
1) contamination of raw water supplies from natural and
man-made sources, and 2) leachate from coal tar and
asphalt linings in water storage tanks and distribution
lines. PAHs in raw water will tend to adsorb to any
particulate matter and be removed by filtration before
reaching the tap.
PAHs in tap water will mainly be due to the presence
of PAH-containing materials in water storage and distri-
bution systems. Though few data are available for esti-
mating the potential for PAH release to water from these
materials, there are reports that levels can reach 0.01 mg/
L with optimum leaching conditions.
ENVIRONMENTAL FATE
Released benzo(a)pyrene is largely associated with
particulate matter, soils, and sediments. Although envi-
ronmental concentrations are highest near sources, its
presence in places distant from primary sources indi-
cates that it is reasonably stable in the atmosphere and
capable of long distance transport. When released to air
it may be subject to direct photolysis, although adsorption
to particulates apparently can retard this process. It may
October 1995
Technical Versioni
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also be removed by reaction with ozone (half-life 37 min)
and NO2 (half-life 7 days), and an estimated half-life for
reaction with photochemically produced hydroxyl radi-
cals is 21.49 hr.
If released to water, it will be expected to adsorb very
strongly to sediments and particulate matter. It will not
hydrolyze. It has been shown to be susceptible to signifi-
cant metabolism by microorganisms in some natural
waters without use as carbon or energy source, but in
most waters and in sediments it is stable towards biodeg-
radation. BaP will be expected to undergo significant
photodegradation near the surface of waters. Evapora-
tion may be significant with a predicted half-life of 43
days. However, adsorption to sediments and participates
may significantly retard biodegradation, photodegrada-
tion, and evaporation.
If released to soil it will be expected to adsorb very
strongly and will not be expected to leach to the ground-
water. However, its presence in some groundwater
samples indicates that it can be transported there by
some mechanism. It will not hydrolyze, and evaporation
from soils arid surfaces is not expected to be significant.
Biodegradation tests in soils have resulted in a wide
range of reported half-lives: 2 days to 1.9 yr. Based on
these values and the apparent lack of a significant
competing fate process, biodegradation may be an im-
portant process in soils.
Benzo(a)pyrene is expected to bioconcentrate in
aquatic organisms that can not metabolize it. Reported
BCFs include: Oysters, 3000; Rainbow trout, 920; Blue-
gills, 2,657; zooplankton, 1000 to 13,000. The presence
of humic acid in solution has been shown to decrease
bioconcentration. Those organisms which lack a meta-
bolic detoxification enzyme system, tend to accumulate
polycyclic aromatic hydrocarbons. For example, BCFs
have been found to be very low (<1) for mudsuckers,
sculpins and sand dabs.
Human exposure will be from inhalation of contami-
nated air and consumption of contaminated food and
water. Especially high exposure will occur through the
smoking of cigarettes and the ingestion of certain foods
(eg smoked and charcoal broiled meats and fish).
OTHER REGULATORY INFORMATION
MONITORING:
FOR GROUND/SURFACE WATER SOURCES:
INITIAL FREQUENCY- 4 quarterly samples every 3 years
REPEAT FREQUENCY- If no detections during initial round:
2 quarterly per year if serving >3300 persons;
1 sample per 3 years for smaller systems
TRIGGERS - Return to Initial Freq. if detect at > 0.00002 mg/L
/
ANALYSIS:
REFERENCE SOURCE METHOD NUMBERS
EPA 600/4-88-039 525.1; 550; 550.1
TREATMENT:
BEST AVAILABLE TECHNOLOGIES
Granular Activated Charcoal
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FOR ADDITIONAL INFORMATION:
* EPA can provide further regulatory and other general information:
• EPA Safe Drinking Water Hotline - 800/426-4791
4 Other sources of lexicological and environmental fate data include:
• Toxic Substance Control Act Information Line - 202/554-1404
• Toxics Release Inventory, National Library of Medicine - 301/496-6531
• Agency for Toxic Substances and Disease Registry - 404/639-6000
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