Technical Factsheet on: POLYCHLORINATED BIPHENYLS (PCBs)
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations
Drinking Water Standards
MCLG: zero mg/L
MCL: 0.0005 mg/L
HAL(child): none
Health Effects Summary
Acute: EPA has found PCBs to potentially cause the following
health effects from short-term exposures at levels above the MCL:
acne-like eruptions and pigmentation of the skin; hearing and
vision problems; spasms.
Chronic: PCBs have the potential to cause the following health
effects from long-term exposure at levels above the MCL: effects
similar to acute poisonings; irritation of nose, throat and
gastrointestinal tracts; changes in liver function.
Cancer: There is some evidence that PCBs may have the potential
to cause cancer from a lifetime exposure at levels above the MCL.
Usage Patterns
Production of PCBs has decreased drastically: from over 86
million lbs. in 1970 to 35 million lbs in 1977. EPA banned most
uses of PCBs in 1979. In 1975 it was estimated that industries
consumed PCBs as follows: Capacitors, 70%; Transformers, 30%
PCBs were formerly used in the USA as hydraulic fluids,
plasticizers, adhesives, fire retardants, way extenders,
dedusting agents, pesticide extenders, inks, lubricants, cutting
oils, in heat transfer systems, carbonless reproducing paper.
Release Patterns
Current evidence suggests that the major source of PCB release to
the environment is an environmental cycling process of PCBs
previously introduced into the environment; this cycling process
involves volatilization from ground surfaces (water, soil) into
the atmosphere with subsequent removal from the atmosphere via
wet/dry deposition and then revolatilization. PCBs 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.
From 1987 to 1993, according to EPA's Toxic Chemical Release
Inventory, PCB releases to land and water totalled over 74,000
lbs., of which about 99 percent was to land. The bulk of these
releases occurred in 1990 and were primarily from non-ferrous
wire drawing and insulating industries. The largest releases (10%
or more of the total) occurred in California.
Environmental Fate
PCBs 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 PCBs increases with an increase in the degree of
chlorination. Mono-, di- and trichlorinated biphenyls biodegrade
relatively rapidly, tetrachlorinated biphenyls biodegrade slowly,
and higher chlorinated biphenyls are resistant to biodegradation.
Although biodegradation of higher chlorinated congeners may occur
very slowly on an environmental basis, 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.
If released to soil, PCBs experience tight adsorption with
adsorption generally increasing with the degree of chlorination
of the PCB. PCBs will generally not leach significantly in
aqueous soil systems; the higher chlorinated congeners will have
a lower tendency to leach than the lower chlorinated congeners.
In the presence of organic solvents PCBs may leach quite rapidly
through soil. Vapor loss of PCBs from soil surfaces appears to be
an important fate mechanism with the rate of volatilization
decreasing with increasing chlorination. Although the
volatilization rate may be low, the total loss by volatilization
over time may be significant because of the persistence and
stability of PCBs. 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; PCB concentrations in sediment
and suspended matter have been shown to be greater than in the
associated water column. Although adsorption can immobilize PCBs
(especially the higher chlorinated congeners) for relatively long
periods of time, eventual resolution into the water column has
been shown to occur. The PCB composition in the 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, PCBs
volatilize relatively rapidly from water. However, strong PCB
adsorption to sediment significantly competes with
volatilization, with the higher chlorinated PCBs having longer
half-lives than the lower chlorinated PCBs. Although the
resulting volatilization rate may be low, the total loss by
volatilization over time may be significant because of the
persistence and stability of the PCBs.
If released to the atmosphere, PCBs will primarily exist in the
vapor-phase; the tendency to become associated with the
particulate-phase will increase as the degree of chlorination of
the PCB increases. The dominant atmospheric transformation
process is probably the vapor-phase reaction with hydroxyl
radicals which has estimated half-lives ranging from 12.9 days
for monochlorobiphenyl to 1.31 years for heptachlorobiphenyl.
Physical removal of PCBs from the atmosphere, which is very
important environmentally, is accomplished by wet and dry
deposition.
PCBs have been shown to bioconcentrate significantly in aquatic
organisms. Average log BCFs of 3.26 to 5.27, reported for various
congeners in aquatic organisms, show increasing accumulation
with the more highly chlorinated congeners. The major PCB
exposure routes to humans are through food and drinking water,
and by inhalation of contaminated air.
Chemical/ Physical Properties
CAS Number: 1336-36-3
Color/ Form/Odor: PCB is generic term for group of organic
chemicals which can be odorless or mildly aromatic solids or oily
liquids; available in mixtures containing several PCBs and other
organics as well.
M.P.: 340 to 375 C B.P.: N/A
Octanol/Water Partition (Kow): N/A
Vapor Pressure: N/A; moderately volatile from water and soil
Density/Spec. Grav.: 1.44 at 30 C
Solubility: N/A; insoluble in water
Soil sorption coefficient: Koc generally above 5000; low mobility
in soil, but may leach with mobile organic solvents.
Odor/Taste Thresholds: N/A
Bioconcentration Factor: Log BCF - 3.26 to 5.27 in aquatic
organisms; expected to bioconcentrate in aquatic organisms.
Henry's Law Coefficient: 3.3x10-4 to 5x10-5 atm-cu m/mole at 20
deg C
Trade Names/Synonyms: PCB, Chlorinated diphenyl, Clophen,
Kanechlor, Aroclor, Fenclor, Chlorextol, Dykanol, Inerteen,
Monter, Pyralene, Santotherm, sovol, Therminol, Noflamol
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 congener-specific limits
Analysis:
Reference Source |
Method Numbers |
EPA 600/4-88-039 |
505; 508; 508A |
Treatment- Best Available Technologies:
Granular Activated Charcoal
Toxic Release Inventory - Releases to Water and Land, 1987 to
1993 (in pounds):
|
Water |
Land |
TOTALS |
784 |
73,632 |
Top Five States |
CA |
0 |
58,178
|
NJ |
0 |
13,188
|
KY |
250 |
750
|
WA |
0 |
998
|
TN |
255 |
251
|
Major Industries |
Non-ferrous wire |
0 |
58,178
|
Steel pipe/tubing |
0 |
13,183
|
Pulp mills |
0 |
998
|
For Additional Information:
EPA can provide further regulatory and other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
Other sources of toxicological 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
List of Contaminants
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