904 PCBs AND ASSOCIATED AROMATICS
benzenes. A faulty electrical cable caught fire and fell onto
an energized askarel transformer. The transformer circuit
breaker failed and allowed the unit to remain energized for
at least three hours. Approximately 30 gallons of Aroclor
1242 leaked from the transformer during the fire.
Soot laden smoke issued from the sidewalk grating
adjacent to the building for about three hours and contami-
nated the switch gear room and some areas of the adjacent
parking garage. The fire activated a ventilating air system
within the building which was designed to draw air from the
ground level intake to the first and second basements and to
various retail stores on the plaza level as well as to floors
2 through 6 of the Steuart Street Tower. Dry wipe samples
showed contamination of about 720 μ g TCDF/100 cm^2 and
the building was closed.
The maximum concentrations of PCBs and PCDFs in air
were calculated on the basis of measured component ratios.
For example, the ratio of 2,3,7,8-TCDF to PCBs was found
to be about 1 : 240,000 in air inside the vault but 1:160,000
in air on the 21st floor. Note that PCDDs were not formed
because there were no chlorobenzenes used in the dielectric
liquid. Analysis of the soot collected in the vault showed
the presence of the same classes of compounds as found in
the Binghamton incident. The conversion of PCBs to PCDFs
seemed to have occurred with approximately the same effi-
ciency as in Binghamton.The cost of cleanup was close to $20,000,000 with
one additional million dollars spent to replace the electri-
cal equipment in the vault. The largest civil suit was that
brought by the Fire Department for $100 million.
In September 1983, a fire occurred in a transformer vault
under the plaza on the same block as the First National Bank
building in Chicago. Smoke issued from a sidewalk grating for
about 45 min. but, fortunately, significant PCB contamination
was limited to the vault. It was estimated that 1–4 gallons of
dielectric fluid were pyrolyzed but, interestingly, no PCDFs
or PCDDs were detected in the soot. Cleanup costs were esti-
mated to be $50,000–$100,000 and no civil damage suits were
filed.
The known costs of the fire related incidents described in
Table 34 has led the EPA to assess an average clean-up cost per
incident of $20,000,000. PCDFs and PCDDs are recognized as
ubiquitous environmental contaminants. The following Table
37 shows the background contamination levels in two office
buildings in Boston, MA. Neither building had been involved
in an electrical transformer failure. Two sets of data are shown,
one for high skin contact areas and one for elevated horizontal
surfaces. A high skin contact area is taken to mean one in which
a person might have prolonged direct dermal contact such as
desks, tables, counters and file cabinets. Elevated horizontal
surfaces are those six feet or more above the floor such as the
tops of storage cabinets or bookshelves. Background levels ofTABLE 36
Determination of PCB : PCDF ratios were used to calculate maximum air concentrationsLocation PCB mg/m^3Total TCDF^1
pg/mg^32,3,7,8-TCDF^2
pg/m^3Fan Room (B2) 2.7 100 11
Switchgear Room (B2) 16 580 67
Transformer Vault 556 20,000 2,300
Garage (B2) 3.2 120 13
Woodshop (B1) 3.0 110 12
Outside Vault
Perimeter 1.3 48 5.4
Clean Areas <1.0 <37 <41 Based on a worst-case ratio of PCB : Total TCDF 27,000.(^2) Based on a worst case ratio of PCB : 2,3,7,8-TCDF 240,000.
TABLE 37
Background concentrations of PCDFs and PCDDs in Office Buildings
PCDFs ng/m^2 PCDDs ng/m^2
Mean Range Mean Range
High Skin Contact 0.98 0.5–1.9 12 4.1–42
Elevated Horizontal 2.4 0.47–5.4 40 2.8–146
Overall 1.7 0.47–5.4 26 2.8–146
J.R. Kominsky and C.D. Kwoka^.^87 Background levels of PCBs have been investigated
by NIOSH. Their data are shown in Table 32 for comparison.
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