| Chemical Abstract Number (CAS #) |
11096825
|
|---|
| CASRN |
11096-82-5 |
|---|
| Synonyms | PCB-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 Formula | UVCB |
|---|
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 .
|
|---|
