Environmental Engineering Reference
In-Depth Information
• Oil used in motors and hydraulic systems
• Older electrical devices containing capacitors
• Fluorescent light ballasts
• Cable insulation
• Thermal insulation material including fiberglass, felt, foam, and cork
• Adhesives and tape
• Oil-based paint
• Caulking
• Plastics
• Carbonless copy paper
• Floor finish
PCBs are mixtures of chlorinated organic compounds called congeners (ATSDR 2001b). A
congener
is a related compound or compounds in a specific chemical family. There are a
large number of congeners, with about 209 found in PCB mixtures (USEPA 2009d). PCBs
were produced synthetically through electrophilic chlorination of a biphenyl molecule
with chlorine gas. In the United States, PCBs are commonly known under the trade name
aroclors.
Aroclors
are mixtures of PCBs distinguished by a four digit numbering system.
The first two digits refer to the number of carbon atoms in a PCB molecule, and the second
two digits indicate the percentage of chlorine by mass in the mixture (USEPA 2009d). For
example, PCB aroclor 1254 means the mixture contains 12 carbon atoms and is 54% chlo-
rine by weight (ATSDR 2001c).
As the degree of chlorination increases, the melting point increases and the vapor pres-
sure and solubility decrease. The general chemical formula for PCBs is the following:
C
12
H
10-x
Cl
x
where x = 1-10.
Common PCB aroclors are listed in Table 7.7 (Phillips 1986; USEPA 2009c).
Figure 7.8 shows the basic structure of a PCB molecule.
TABLE 7.7
Common PCB Aroclors
Average Number
of Chlorine Atoms
per Molecule
CAS Registry
Number
Average
Molecular Weight
PCB Aroclor
Percent Chlorine
Aroclor 1016
12674-11-2
15.5-16.5
1.05
160
Aroclor 1221
11104-28-2
20.5-21.5
1.15
192
Aroclor 1232
11141-16-5
31.5-32.5
2.04
221
Aroclor 1242
53469-21-9
42
3.10
261
Aroclor 1248
12672-29-6
48
3.90
288
Aroclor 1254
11097-69-1
54
4.96
327
Aroclor 1260
11096-82-5
60
6.30
372
Aroclor 1262
37323-23-5
62
6.80
389
Aroclor 1268
11100-14-4
68
8.70
453
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