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Benzo[a]pyrene Basic information

Product Name:
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Benzo[a]pyrene Chemical Properties

Melting point:
Boiling point:
1.1549 (estimate)
vapor pressure 
2.4 at 25 °C (McVeety and Hites, 1988)
refractive index 
1.8530 (estimate)
Flash point:
storage temp. 
Soluble in benzene, toluene, and xylene; sparingly soluble in ethanol and methanol (Windholz et al., 1983)
>15 (Christensen et al., 1975)
Pale yellow/green/orange
Water Solubility 
Soluble in benzene, toluene, and xylene. Sparingly soluble in alcohol, methanol. Insoluble in water
Henry's Law Constant
7.35 at 25 °C (thermodynamic method-GC/UV spectrophotometry, Altschuh et al., 1999)(x 10-10 mmHg at 25 °C):
Stable. Incompatible with strong oxidizing agents.
CAS DataBase Reference
50-32-8(CAS DataBase Reference)
EPA Substance Registry System
Benzo[a]pyrene (50-32-8)

Safety Information

Hazard Codes 
Risk Statements 
Safety Statements 
WGK Germany 
HS Code 
LD50 for mice (intraperitoneal) 232 mg/kg (Salamone, 1981).


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Benzo[a]pyrene Usage And Synthesis


Benzo[a]pyrene belongs to the class of polycyclic aromatic hydrocarbons (PAHs). It is produced during incomplete combustion or pyrolysis of organic material and found in nature from the eruption of volcanoes and forest fires. Man-made benzo[a]pyrene is formed by burning plants, wood, coal, and operating cars, trucks and other vehicles. It is also present in some foods (e.g. smoked and barbecued meals), in a few pharmaceutical products, and in tobacco smoke. It is considered as potent mutagen and carcinogen. Benzo[a]pyrene containing extender oil is used for the rubber/plastic production to achieve the desired elasticity at a cheaper price. Benzo[a]pyrene containing coal tar pitch is used in many paints or coatings as corrosion protection coats, such as hydraulic equipment, pipework, steel pilings in ports, vessels, and sealcoat products. Benzo[a]pyrene can be used as wood-preservatives to prevent wood parasites and the wood from drying out.


  5. Barbara J. Mahler, Peter C. Van Metre, Judy L. Crane, Alison W. Watts,  Mateo Scoggins, and E. Spencer Williams, Coal-Tar-Based Pavement Sealcoat and PAHs: Implications for the Environment, Human Health, and Stormwater Management, Environ Sci Technol, 2012, vol. 46, 3039-3045

Chemical Properties

B(a)P, is yellowish needles, crystals or powder. Odorless. PAHs are compounds containing multiple benzene rings and are also called polynuclear aromatic hydrocarbons.

Physical properties

Odorless, yellow, orthorhombic or monoclinic crystals from ethanol. Solution in concentrated sulfuric acid is orange-red and fluoresces green under exposure to UV light (quoted, Keith and Walters, 1992).


Benzopyrene is a polyaromatic hydrocarbon (PAH) found in coal tar. Benzopyrene is a known carcinogen. The metbolism of Benzopyrene results in diol epoxides that react and bind to DNA forming adducts which in turns leads to mutations and eventually cancer.


ChEBI: An ortho- and peri-fused polycyclic arene consisting of five fused benzene rings.


A cyclic aromatic hydrocarbon with a structure consisting of five fused benzene rings. It occurs in coal tar and tobacco smoke and has strong carcinogenic properties.

General Description

A liquid. Presents a threat to the environment. Immediate steps should be taken to limits its spread to the environment. Easily penetrates the soil and contaminates groundwater or nearby waterways.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

BENZO[A]PYRENE undergoes photo-oxidation after irradiation in indoor sunlight or by fluorescent light in organic solvents. Incompatible with strong oxidizing agents including various electrophiles, peroxides, nitrogen oxides and sulfur oxides. Oxidized by ozone, chromic acid and chlorinating agents. Readily undergoes nitration and halogenation. Hydrogenation occurs with platinum oxide .


Highly toxic, confirmed carcinogen by inhalation.

Health Hazard

The acute oral toxicity of benzo[a]pyrene islow. This may be due to the poor absorption of this compound by the gastrointestinal tract.The lethal dose in mice from intraperitonealadministration is reported as 500 mg/kg(NIOSH 1986).
Animal studies show sufficient evidence ofits carcinogenicity by all routes of exposureaffecting a variety of tissues, which includethe lungs, skin, liver, kidney, and blood.
Dasenbrock et al. (1996) have investigatedthe carcinogenic potency of carbon particles,diesel soot and benzo[a]pyrene in rats fromrepeated intracheal administration in a 16-week study. A total dose of 15 mg purebenzo[a]pyrene caused lung tumor in theexperimental animals at a rate similar tothat caused by diesel soot and carbon blackparticles.
Lodovici et al. (1998) measured the levelsof PAHs and benzo[a]pyrenediol epoxideDNA adduct in autoptic lung samples ofsmokers and non-smokers. Benzo[a]pyrenediol epoxide resulting from metabolic activation of benzo[a]pyrene binds to DNA to forman adduct, the levels of which can be used as abiomarker to evaluate the exposure of humansto benzo(a)pyrene.
Benz[a]pyrene exhibited teratogeniceffects in test species. It is a mutagen.It showed positive in a histidine rever-sion–Ames test, cell transform mouse embryotest, and in in vitro sister chromatid exchange(SCE)–human lymphocytes..

Fire Hazard

Literature sources indicate that BENZO[A]PYRENE is nonflammable.


benzo[a]pyrene (BP) is a reasonably potent contact carcinogen, and therefore has been subjected to extensive carcinogenic testing. A diet containing 25 ppm of benzo[a]pyrene (BP) fed to mice for 140 days produced leukemia and lung adenomas in addition to stomach tumors. Skin tumors developed in over 60% of the rats treated topically with approximately 10 mg of benzo[a]pyrene three times per week. The incidence of skin tumors dropped to about 20% when treatment was about 3 mg  3 per week. Above the 10 mg range, however, the incidence of skin tumors increased dramatically to nearly 100%. benzo[a]pyrene (BP) is also carcinogenic when administered orally. In one experiment, weekly doses of greater than 10 mg administered for 10 weeks induced stomach cancers, although no stomach cancers were produced at the dose of 10 mg or less. At 100 mg doses, nearly 79% of the animals had developed stomach tumors by the completion of the experiment. When 15 ppm of benzo[a]pyrene (BP) in feed was orally administered to mice, production of leukemia, lung adenomas, and stomach tumors were observed after 140 days.

Safety Profile

Confirmed carcinogen withexperimental carcinogenic, neoplastigenic, andtumorigenic data. A poison via subcutaneous,intraperitoneal, and intrarenal routes. Experimentalteratogenic and reproductive effects. Human mutation data reported. A skin irritant.

Potential Exposure

Benzopyrene (BP) is a PAH that has no commercial-scale production. B(a)P is produced in the United States by one chemical company and distributed by several specialty chemical companies in quantities from 100 mg to 5 g for research purposes. Although not manufactured in great quantity, B(a)P is a by-product of combustion. It is estimated that 1.8 million pounds per year are released from stationary sources, with 96% coming from: (1) coal refuse piles, outcrops, and abandoned coal mines; (2) residential external combustion of bituminous coal; (3) coke manufacture; and (4) residential external combustion of anthracite coal. Human exposure to B(a)P can occur from its presence as a by-product of chemical production. The number of persons exposed is not known. Persons working at airports in tarring operations; refuse incinerator operations; power plants, and coke manufacturers, may be exposed to higher B(a)P levels than the general population. Scientists involved in cancer research or in sampling toxic materials may also be occupationally exposed. The general population may be exposed to B(a)P from air pollution, cigarette smoke, and food sources. B(a) P has been detected in cigarette smoke at levels ranging from 0.2 to 12.2:g per 100 cigarettes. B(a)P has been detected at low levels in foods ranging from 0.1 to 50 ppb.


MCLG: zero; MCL: 0.2 μg/L (U.S. EPA, 2000).
Identified in Kuwait and South Louisiana crude oils at concentrations of 2.8 and 0.75 ppm, respectively (Pancirov and Brown, 1975). Emitted to the environment from coke production, coal refuse and forest fires, motor vehicle exhaust, and heat and power (utility) generation (Suess, 1976). Benzo[a]pyrene is produced from combustion of tobacco and fuels. It is also a component of gasoline (133–143 μg/L), fresh motor oil (20 to 100 g/kg), used motor oil (83.2 to 242.4 mg/kg), asphalt (≤0.0027 wt %), coal tar pitch (≤1.25 wt %), cigarette smoke (25 μg/1,000 cigarettes), and gasoline exhaust (quoted, Verschueren, 1983). Detected in asphalt fumes at an average concentration of 14.72 ng/m3 (Wang et al., 2001). Benzo[a]pyrene was also detected in liquid paraffin at an average concentration of 25 μg/kg (Nakagawa et al., 1978).
Benzo[a]pyrene was reported in a variety of foodstuffs including raw and cooked meat (ND to 12 ppb), fish (0.3–6.9 ppb), vegetables oils (ND-4), fruits (ND to 6.2 ppb) (quoted, Verschueren, 1983).
The concentration of benzo[a]pyrene in coal tar and the maximum concentration reported in groundwater at a mid-Atlantic coal tar site were 3,600 and 0.0058 mg/L, respectively (Mackay and Gschwend, 2001). Based on laboratory analysis of 7 coal tar samples, benzo[a]pyrene concentrations ranged from 500 to 6,400 ppm (EPRI, 1990). In three high-temperature coal tars, benzo[a]pyrene concentrations ranged from 5,300 to 7,600 mg/kg (Lehmann et al., 1984). Benzo[a]pyrene was identified in a U.S. commercial creosote at an approximate concentration of 0.3% (Black, 1982). Nine commercially available creosote samples contained benzo[a]pyrene at concentrations ranging from 2 to 160 mg/kg (Kohler et al., 2000).
Identified in high-temperature coal tar pitches used in roofing operations at concentrations ranging from 4,290 to 13,200 mg/kg (Arrendale and Rogers, 1981; Malaiyandi et al., 1982). Lee et al. (1992a) equilibrated 8 coal tars with distilled water at 25 °C. The maximum concentration of benzo[a]pyrene observed in the aqueous phase was 1 μg/L.
Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The particle-phase emission rates of benzo[a]pyrene were 0.712 mg/kg of pine burned, 0.245 mg/kg of oak burned, and 0.301 mg/kg of eucalyptus burned.
Particle-phase tailpipe emission rates from gasoline-powered automobiles with and without catalytic converters were 0.021 and 41.0 μg/km, respectively (Schauer et al., 2002).
Under atmospheric conditions, a low rank coal (0.5–1 mm particle size) from Spain was burned in a fluidized bed reactor at seven different temperatures (50 °C increments) beginning at 650 °C. The combustion experiment was also conducted at different amounts of excess oxygen (5 to 40%) and different flow rates (700 to 1,100 L/h). At 20% excess oxygen and a flow rate of 860 L/h, the amount of benzo[a]pyrene emitted ranged from 39.4 ng/kg at 650 °C to 690.7 ng/kg at 850 °C. The greatest amount of PAHs emitted were observed at 750 °C (Mastral et al., 1999).

Environmental Fate

The main natural sources of Benzo[a]pyrene(BaP) are forest fires and erupting volcanoes. Anthropogenic sources include the combustion of fossil fuels, coke oven emis- sions, and vehicle exhausts. In surface waters, direct deposition from the atmosphere appears to be the major source of BaP. Benzo[a]pyrene is moderately persistent in the environment. It readily binds to soils and does not readily leach to groundwater, though it has been detected in some groundwater. If released to water, it sorbs very strongly to sediments and particulate matter. In most waters and sediments, it resists breakdown by microbes or reactive chemicals, but it may evaporate or be degraded by sunlight. In water supply systems, it tends to sorb to any particulate matter and be removed by filtration before reaching the tap. In tap water, its source is mainly from PAH-containing materials in water storage and distribution systems.

Purification Methods

A solution of 250mg of benzo[a]pyrene in 100mL of *benzene is diluted with an equal volume of hexane, then passed through a column of alumina, Ca(OH)2 and Celite (3:1:1). The adsorbed material is developed with a 2:3 *benzene/hexane mixture. (It showed as an intensely fluorescent zone.) The main zone is eluted with 3:1 acetone/EtOH, and is transferred into 1:1 *benzene-hexane by adding H2O. The solution is washed, dried with Na2SO4, evaporated and crystallised from *benzene by the addition of MeOH [Lijinsky & Zechmeister J Am Chem Soc 75 5495 1953]. Alternatively it can be chromatographed on activated alumina, eluted with a cyclohexane-*benzene mixture containing up to 8% *benzene, and the solvent evaporated under reduced pressure [Cahnmann Anal Chem 27 1235 1955], and crystallised from EtOH [Nithipatikom & McGown Anal Chem 58 3145 1986]. [Beilstein 5 III 2517, 5 IV 2687.] CARCINOGENIC.


Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides, nitrogen dioxide and ozone.

Waste Disposal

Incineration in admixture with a flammable solvent.



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