Chemical Fact Sheet

Chemical Abstract Number (CAS #) 50328
CASRN 50-32-8
Analytical Methods EPA Method 525.2
EPA Method 610
EPA Method 625
EPA Method 8100
EPA Method 8270
EPA Method 8310
Molecular FormulaC20H12

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use used extensively as a positive control in a variety of laboratory mutagenicity & carcinogenicity short-term tests. RESEARCH CHEMICAL NOT USED COMMERCIALLY IN USA
Odor Faint aromatic odor
Boiling Point Boiling point: > 360 deg C at 760 mm Hg
Melting Point 179-179.3 DEG C
Molecular Weight 252.30
Density 1.351
Environmental Impact Benzo(a)pyrene's (BaP) release to the environment is quite wide spread since it is an ubiquitous product of incomplete combustion. It is largely associated with particulate matter, soils, and sediments. Although environmental concentrations are highest near sources, its presence in places distant from primary sources indicates 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 also be removed by reaction with O3 (half-life 37 min) and NO2 (half-life 7 days), and an estimated half-life for reaction with photochemically produced hydroxyl radicals is 21.49 hr. If released to water, it will adsorb very strongly to sediments and particulate matter, bioconcentrate in aquatic organisms which can not metabolize it, but will not hydrolyze. It may be subject to significant biodegradation, and direct photolysis may be important near the surface of waters; adsorption, however, may significantly retard these two processes. Evaporation may be important with a half-life of 43 days predicted for evaporation from a river 1 m deep, flowing at 1 m/sec with a wind velocity of 3 m/sec; adsorption to sediments and particulates will limit evaporation. If released to soil it will be expected to adsorb very strongly to the soil and will not be expected to appreciably leach to the groundwater, although its presence in some samples of groundwater illustrates that it can be transported there. It will not be expected to hydrolyze or significantly evaporate from soils and surfaces. It may be subject to appreciable biodegradation in soils. Human exposure will be from inhalation of contaminated 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).
Environmental Fate TERRESTRIAL FATE: If benzo(a)pyrene is released to soil it will be expected to adsorb very strongly and will not be expected to leach to the groundwater; 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 and 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 important process in soils. AQUATIC FATE: If released to water, benzo(a)pyrene (BaP) will be expected to adsorb very strongly to sediments and particulate matter. It will not hydrolyze but will be expected to bioconcentrate in aquatic organisms that can not metabolize it. It has been shown to be susceptible to significant metabolism by microorganisms in some natural waters without use as carbon or energy source, but in most waters and in sediments it has been shown to be stable towards biodegradation. BaP will be expected to undergo significant photodegradation near the surface of waters. Evaporation may be significant with a predicted half-life of 43 days for volatilization from a river 1 m deep, flowing at 1 m/sec with a wind velocity of 3 m/sec. Adsorption to sediments and particulates may significantly retard biodegradation, photodegradation, and evaporation. ATMOSPHERIC FATE: Benzo(a)pyrene (BaP) released to the atmosphere will likely be associated with particulate matter and may be subject to moderately long transport, depending mainly on the particle size distribution and climactic conditions which will determine the rates of wet and dry deposition. Its presence in areas remote from primary sources demonstrates the potential for this long range transport as well as BaP's considerable stability in the air. A half-life of 1.4 years has been reported for removal of BaP from the gas phase by rainout and has a lifetime of 7.9 days for removal by aerosol particles . It may be subject to direct photodegradation but evidence suggests that this process is retarded by the material being in the adsorbed state. Half-life for reaction of a thin film of BaP with 0.19 ppm O3 is 37 min and for reaction of adsorbed BaP with NO2 is 7 days. The estimated half-life for reaction with photochemically produced hydroxyl radicals is 21.49 hr.
Drinking Water Impact DRINKING WATER: 15 USA cities, 87% pos, 0.1-2.1 parts per trillion, avg 0.55 parts per trillion . USA, 0.20- parts per trillion ; USA: 6 cities, finished and distribution water, <1 parts per trillion; 11 cities, 0.2-1.6 parts per trillion; 8 cities, <1-1 parts per trillion . Treated surface waters used as drinking waters: River Rhine, 0.5 parts per trillion, Lake Constance, 1.7, English River, 9 parts per trillion . West Germany, 1968, 6 samples, 100% pos, 0.5-4.0 parts per trillion . Th Netherland, avg 2 parts per trillion, max 15 parts per trillion . UK, 1974-75 7 distributed treated surface water systems, Trace-<3 parts per trillion; 8 groundwater distribution systems, 1974-77, trace-<10 ppt, max during repair work on parts of 1 system, 101 parts per trillion . Norway, 4 samples, <0.05-0.29 parts per trillion(6). GROUNDWATER: Elkhart, IN, 4 parts per trillion, Fairborn, OH, 0.3 parts per trillion, Champaign, IL, not detected, unspecified sites in West Germany, 0.4 parts per trillion . . West Germany, 1968, 10 samples, 0.4-3.8 parts per trillion . The Netherlands, 232 groundwaer pumping stations, max concn 1 ppb . Germany, 1963-64, 3 sites, 0.1-23.4 parts per trillion . SURFACE WATER: US STORET Database, 914 water stations, 2.0% pos, median <10 ppb . Germany, four rivers, 100% pos, 0.6-80 parts per trillion, avg 23 parts per trillion ; USSR, 2 rivers, 17 and 10 parts per trillion ; Thames River, UK, 3 stations, 0.13-0.35 ug/l, avg 0.21 ug/l . Germany, 1963-64, 4 rivers, 6 sites, 0.6-114.0 parts per trillion; USSR, 5 sites < 0.1-13,000 parts per trillion (max Moscow Reservoirs); UK: Severn River, 5 sites, 1.5-13.5 parts per trillion, Thames River, 2 sites, 130-210 parts per trillion; River Trent and tributaries, 11 sites, in solution, 0.1-1.8 parts per trillion, in suspended solids, 0.8-504.0 parts per trillion (max River Trent at Keadby)(3. UK, 1973-76, 9 rivers, 25 sites, 51 samples, 3.8-531 parts per trillion . RAINWATER: 2.2-7.3 ppt . The Netherland, 3 rainfall events, Dec 10, 1982: 3 samples taken 5, 12, and 23 min after onset of rain: 390, 9, 6 parts per trillion; same date, 4 samples taken 8, 18, 27, and 38 min after onset of second rain event: 75, 25, 18, 0 (not detecteed) parts per trillion; Sept, 1983, 8 samples taken 12-25 min after onset of rain: 10-37 parts per trillion . EFFL: US STORET Database, 1253 water stations, 2.3% pos, median <10 ppb . Sludge from 12 UK sewage treatment plants, 16-400 ppb (dry wt), 0.35-11.43 ppm (dry wt) . Bekkelaget Sewage Treatment Plant, Oslo, Norway, <3-5 parts per trillion . Those industries with mean raw or treated wastewater concn exceeding 100 ppb includes (max raw wastewater concn, ppb): coal mining (140), iron and steel manufacturing (14,000), nonferrous metals manufacturing (570), timber products processing (2,700) . Estimates of total emissions >100 metric tons/yr: coal-fired residential furnaces, coke production, forest fires, burning coal refuse banks; estimates >10 metric tons/yr: coal-fired industrial boilers, residential fireplaces, iron and steel sintering, commercial incinerators, open burning of auto components and leaves, trucks and automobiles, and tire wear . Identified, not quantified in emissions from biomass gasifier(6). Estimated emissions from mobile sources, 1979, 43 metric tons; estimated total annual emission, 1975, 346-1,676 (intermediate 588) metric tons, 1985, 67-885 (intermediate 358) metric tons(7). Industrial effluent wastewaters: shale oil, 312 ppb, gasworks, 20-290 ppb, coke by-products, 12-16 ppb, oil refineries, 0.05-3.6 ppb; domestic effluent, 0.038-0.074, final effluent of sewage work, 0.03 ppb(8). National Urban Runoff Program, 15 cities, 13% pos, 86 samples, 4% pos, 1-10 ppb(9).

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