SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 11096825
CASRN 11096-82-5
SynonymsPCB-1260
Aroclor 1260
Analytical Methods EPA Method 505
EPA Method 508
EPA Method 608
EPA Method 617
EPA Method 625
EPA Method 8081
EPA Method 8082
EPA Method 8270
Molecular FormulaUVCB

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

Use Formerly used in electrical transformers, hydraulic fluids, plasticizer in synthetic resins and dedusting agents. Although the production and sale was discontinued in late 1977, it is still present in many of the transformers and capacitors now in use.
Consumption Patterns NOT USED COMMERCIALLY IN USA
Apparent Color Light yellow, soft, sticky resin
Odor Practically odorless
Molecular Weight Average mol wt: 372.
Density 1.58 at 25 deg C
Sensitivity Data Irritating to skin, and eyes.
Environmental Impact Current evidence suggests that the major source of Aroclor 1260 release to the environment is an environmental cycling process of Aroclor 1260 previously introduced into the environment; this cycling process involved volatilization from ground surfaces (water, soil) into the atmosphere with subsequent removal from the atmosphere via wet/dry deposition and revolatilization. PCBs such as Aroclor 1260, are also currently released to the environment from landfills containing PCB waste materials and products, incineration of municipal refuse and sewage sludge, and improper (or illegal) disposal of PCB materials, such as waste transformer fluid, to open areas. Aroclor 1260 is a mixture of different congeners of chlorobiphenyl and the relative importance of the environmental fate mechanisms generally depends on the degree of chlorination. In general, the persistence of the PCB congeners increase with an increase in the degree of chlorination. Screening studies have shown that Aroclor 1260 is resistant to biodegradation. Although biodegradation of Aroclor 1260 may occur very slowly in the environment, no other degradation mechanisms have been shown to be important in natural water and soil systems; therefore, biodegradation may be the ultimate degradation process in water and soil. The PCB composition of the biodegraded Aroclor is different from the original Aroclor. If released to soil, the PCB congeners present in Aroclor 1260 will become tightly adsorbed to the soil particles. In the presence of organic solvents, PCBs may have a tendency to leach through soil. Although the volatilization rate of Aroclor 1260 may be low from soil surfaces, the total loss by volatilization over time may be significant because of the persistence and stability of Aroclor 1260. Enrichment of the low Cl PCBs occurs in the vapor phase relative to the original Aroclor; the residue will be enriched in the PCBs containing high Cl content. If released to water, adsorption to sediment and suspended matter will be an important fate process. Although adsorption can immobilize Aroclor 1260 for relatively long periods of time, eventual resolution into the water column has been shown to occur. The PCB composition in water will be enriched in the lower chlorinated PCBs because of their greater water solubility, and the least water soluble PCBs (highest Cl content) will remain adsorbed. In the absence of adsorption, Aroclor 1260 volatilizes relatively rapidly from water. However, strong PCB adsorption to sediment significantly competes with volatilization which may have a half-life in excess of 60 years in typical bodies of water. Aroclor 1260 has been shown to bioconcentrate significantly in aquatic organisms. If released to the atmosphere, the PCB congeners in Aroclor 1260 will exist primarily in the vapor-phase with enrichment of the most volatile PCBs although a relatively small percentage will partition to the particulate phase. The dominant atmospheric transformation process for these congeners is probably the vapor-phase reaction with hydroxyl radicals which have estimated half-lives ranging from 4.75 months to 1.31 years. Physical removal of Aroclor 1260 from the atmosphere, which is very important environmentally due to the chemical stability of Aroclor 1260, is accomplished by wet and dry deposition. The major Aroclor 1260 exposure routes to humans are through food and drinking water, and by inhalation of contaminated air. Dermal exposure is important for workers involved with handling PCB-containing electrical equipment, spills or waste-site materials and for swimmers in polluted water. Exposure through consumption of contaminated fish may be especially important.
Environmental Fate TERRESTRIAL FATE: PCBs, such as Aroclor 1260, are mixtures of different congeners of chlorobiphenyl and the relative importance of the environmental fate mechanisms generally depends on the degree of chlorination . In general, the persistence of PCB congeners increases with an increase in the degree of chlorination. Screening tests have shown that Aroclor 1260 is resistant to biodegradation. Although biodegradation of Aroclor 1260 may occur very slowly on an environmental basis, no other degradation mechanisms have been shown to be important in soil systems; therefore, biodegradation may be the ultimate degradation process in soil. Experimentally determined Koc values have shown that Aroclor 1260 will be tightly adsorbed in soil with adsorption generally increasing as the degree of chlorination of the individual congeners increase. Aroclor 1260 should not leach significantly in most aqueous soil systems although the most wate soluble PCBs will be leached preferentially. In the presence of organic solvents, which may be possible at waste sites, PCBs may have a tendency to leach through soil. Although the volatilization rate of Aroclor 1260 may be low from soil surfaces due to the tight adsorption, the total loss by volatilization over time may be significant because of the persistence and stability of Aroclor 1260 . AQUATIC FATE: PCBs, such as Aroclor 1260, are mixtures of different congeners of chlorobiphenyl and the relative importance of the environmental fate mechanism generally depends on the degree of chlorination . In general, the persistence of PCBs increases with an increase in the degree of chlorination. Screening tests have shown that Aroclor 1260 is resistant to biodegradation. It has also been shown that the higher chlorinated congeners in PCBs are susceptible to reductive dechlorination by anaerobic microogranisms found in aquatic sediments . Although biodegradation of higher chlorinated congeners may occur very slowly in the environment, no other degradation mechanisms have been shown to be important in environmental aquatic systems; therefore, biodegradation may be the ultimate degradation process in natural water. In water, adsorption to sediments and organic matter is a major fate process for Aroclor 1260(1,3). The most soluble PCBs will be enriched in water relative to the sediment, and the leached sediment will be enriched in the higher chlorinated PCBs (lowest solubilities in water). The lower chlorinated congeners of Aroclor 1260 will sorb less strongly than the higher chlorinated congeners. Although adsorption can immobilize PCBs for relatively long periods of time in the aquatic environment, resolution into the water column has been shown to occur on an environmental level suggesting that the substantial quantities of PCBs contained in aquatic sediments can act as an environmental sink for environmental redistribution of PCBs(4,5). Volatilization of dissolved Aroclor 1260 is an important aquatic process. A study conducted on Lake Michigan has indicated that volatilization may be the major removal mechanism of total PCBs from lakes . The PCBs with the highest vapor pressure (low Cl) will be enriched in the air. Strong PCB absorption to sediment significantly decreases the rate of volatilization; the volatilization half-life of Aroclor 1260 from typical bodies of water has been estimated to be in excess of 60 years when the effects of adsorption are considered. Although the volatilization rate may be low, the total loss by volatilization over time may be significant because of the persistence and stability of the PCBs. Aquatic hydrolysis and oxidation are not important processes with respect to Aroclor 1260. Aroclor 1260 has been shown to bioconcentrate significantly in aquatic organisms. ATMOSPHERIC FATE: The vapor pressures of the PCB congeners present in Aroclor 1260 indicate that they will exist primarily in the vapor phase in the ambient atmosphere with enrichment of PCBs with enrichment of PCBs with the highest vapor pressures (low Cl) although a relatively small percentage can be expected to partition to atmospheric particulates(1,2). Physical removal of PCBs in the atmosphere is accomplished by wet and dry deposition processes ; dry deposition will be important only for the PCB congeners associated in the particulate-phase. The detection of Aroclor 1260 in various rainwaters is an indication of the importance of wet deposition. The vapor-phase reaction of Aroclor 1260 with hydroxyl radicals, which are photochemically formed by sunlight, may be the dominant degradation process in the atmosphere. The estimated half-life for this reaction with the dominate PCB congeners present in Aroclor 1260 has been estimated to range from 4.75 months to 1.31 years with the half-life increasing as the degree of chlorination increases. The relatively long degradation half-lives in air indicate that physical removal is more important than chemical transformation.
Drinking Water Impact SURFACE WATER: An assessment of the USEPA STORET Database found Aroclor 1260 detected in 4.0% of 1186 observation stations . Aroclor 1260 has been postively detected in Lakes Ontario, Erie, Huron, Michigan and Superior . RAIN/SNOW: Aroclor 1260 levels of 8-26 ng/L were detected in rain water collected from urban and rural areas near Lake Michigan during 1975-7 . Aroclor 1260 levels of 11-24 ng/L were detected in snow collected from urban and rural areas near Lake Michigan during 1975-7 . Aroclor 1260 was qualitatively identified in rainfall and storm water runoff of the Fresno Metropolitan Flood Control District in CA . Levels 8 to 26 ng/L (1975-78) found in rural & urban Lake Michigan . In raw tap water in the Waterford, NY treatment plant, which also has the Hudson River as its source, mean PCB levels in 1976 were 0.12 ug/l (range: 0.05-0.24). Polychlorinated Biphenyls/ EFFL: An assessment of the USEPA STORET Database found Aroclor 1260 detected in 2.0% of 714 observation stations . The average Aroclor 1260 concn emitted from gas vents at a hazardous waste landfill in NC was found to be about 3.0 ug/cu m .

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