Potential Health Hazards
from Electrical Equipment
Fires or Failures
February 24, 1986
Foreword
Current Intelligence Bulletins (CIB's) are reports issued by the National
Institute for Occupational Safety and Health (NIOSH), Centers for Disease
Control, Atlanta, Georgia, for the purpose of disseminating new scientific
information about occupational hazards. A CIB may draw attention to a
hazard previously unrecognized or may report new data suggesting that a
known hazard is either more or less dangerous than was previously thought.
CIB's are prepared by the staff of the Division of Standards Development and
Technology Transfer, NIOSH (Robert A. Taft Laboratories, 4676 Columbia
Parkway, Cincinnati, Ohio 45226) and are distributed to representatives of
organized labor, industry, public health agencies, academia, and public
interest groups as well as to those federal agencies, such as the Department
of Labor, which have responsibilities for protecting the health of workers.
It is our intention that anyone with the need to know should have ready
access to the information contained in these documents; we welcome
suggestions concerning their content, style, and distribution.
Because of the recent attention given to human exposure to polychlorinated
biphenyls (PCB's), polychlorinated dibenzofurans (PCDF's), polychlorinated
dibenzo-p-dioxins (PCDD's), and related compounds resulting from electrical
equipment fires or failures, we think it necessary to present a review of
the pertinent data and a summary of findings related to the potential human
health hazards of these compounds. Because the voluminous literature on
PCB's, PCDF's, and PCDD's has been compressed in this bulletin, it is
suggested that readers wanting additional details of the reported studies
consult the appended references.
[signature]
J. Donald Millar, M.D., D.T. P.H. (Lond.)
Assistant Surgeon General
Director, National Institute for
Occupational Safety and Health
Centers for Disease Control
Abstract
Numerous fire-related incidents involving electrical equipment containing
polychlorinated biphenyls (PCB's) have resulted in widespread contamination
of buildings with PCB's and, in some cases, with polychlorinated
dibenzofurans (PCDF's) and polychlorinated dibenzo-p-dioxins (PCDD's),
including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Emergency response
personnel, maintenance or cleanup workers, or building occupants may be
exposed to the compounds by inhalation, ingestion, or skin contact.
In experimental animal studies, exposure to PCB's, PCDF's, or PCDD's has
resulted in various effects, including decreased body weights, hepatic
lesions, thymic atrophy, and adverse reproductive effects, at a wide range
of exposure concentrations. In addition, PCB's and TCDD have been shown to
be carcinogenic in rats and mice. Humans exposed to PCB's, PCDF's, or
PCDD's have developed chloracne, gastrointestinal disturbances, elevated
serum enzyme and triglyceride levels, and numbness of the extremities.
Epidemiologic studies of humans exposed to PCB's or PCDD's including TCDD
are suggestive of an association between exposure to these compounds and
increased incidences of cancer.
Based on existing evidence, the National Institute for Occupational Safety
and Health (NIOSH) continues to recommend that PCB's and TCDD be regarded as
potential human carcinogens in the workplace. Existing evidence also
suggests that PCDF's may pose a risk to human health. Therefore, NIOSH
recommends that occupational exposure to PCB's, PCDF's, and PCDD's resulting
from electrical equipment fires or failures be controlled to the lowest
feasible limit, and that workers involved in decontamination activities use
all necessary protective measures to prevent exposure.
Background
Physical and Chemical Properties of Polychlorinated Biphenyls (PCB's)
Polychlorinated biphenyls (PCB's)* comprise a class of nonpolar chlorinated
hydrocarbons with a biphenyl nucleus in which any or all of the hydrogen
atoms have been replaced by chlorine.1
Commercial PCB's are mixtures of
isomers of chlorinated biphenyls exhibiting varying degrees of
chlorination. Although there are 209 possible positional chlorobiphenyl
isomers, only 100 individual isomers are likely to occur at significant
concentrations in commercial PCB mixtures.2
In pure form, the individual chlorobiphenyl isomers are colorless crystals,
but the commercial mixtures are liquid due to depression of the melting
points through interaction of the individual isomers.3
The physical and
chemical properties of the individual isomers vary widely according to the
degree and to the position of chlorination. The PCB compounds have low
solubilities in water (0.007 to 5.9 milligrams per liter)3 and low vapor
pressures (10-6 to 10-3 millimeters. of mercury at 20°C).1 PCB's are
soluble in most of the common organic solvents, oils, and fats. The
compounds are stable to acids and alkali and are resistant to oxidation but
are subject to photodechlorination when exposed to sunlight (spectral region
above 290 nanometers).1
Use of PCB's in Electrical Equipment
Commercial products containing PCB's were widely distributed between 1957
and 1977, when large quantities of PCB's were manufactured in the United
States and marketed under the trade name Aroclor. The Aroclor products
were designated by numbers such as 1221, 1242, 1248, 1254, and 1260, with
the last two digits representing the approximate percent by weight of
chlorine in the mixtures. Aroclor 1016, however, contained 41%
chlorine.1
Properties of PCB's such as thermal stability, nonflammability, and
dielectric capability resulted in their use in electrical capacitors and
transformers. Electrical capacitors (small and large) contained nearly 100%
PCB's.4 Small capacitors containing
0.1-0.6 pound of PCB's were commonly
used in household appliances such as television sets, air conditioners, and
fluorescent light fixtures, and have been estimated to have service lives
of at least 10 years.5
Based on Environmental Protection Agency (EPA)
estimates that 10% of the small PCB capacitors (<3 pounds of dielectric
fluid) are removed from service annually,4 approximately 350 million of
the capacitors were still in use in 1984. Large capacitors, with a PCB
content of more than 3 pounds, have been used in electrical substations,
within buildings, and on utility poles. The latest available information
indicates that there were approximately 3.3 million large PCB capacitors in
service in 1981.4
In transformers containing PCB'S, the dielectric fluid generally consists of
60-70% PCB's4 and up to 40%
chlorinated benzenes.6
Trade names of PCB askarels (the generic term used to refer to a broad class of nonflammable,
synthetic, chlorinated hydrocarbon insulating liquids) formulated in the
United States include Pyranol,® Inerteen,® and
Noflamol,®7 The volume of
fluid in transformers ranges from 40 to 1,500 gallons.8 PCB transformers
have been used mainly in or near buildings where the proximity of electrical
equipment to people and/or property warranted the use of a fire-resistant
dielectric fluid. According to EPA estimates, at the end of 1984 there were
approximately 107,000 PCB transformers in use or in storage for reuse,9
including approximately 77,600 PCB transformers used in or near commercial
buildings (e.g., office buildings, shopping centers, hospitals, and schools).10
In 1976, the United States Congress enacted the Toxic Substances Control Act
(TSCA) (Public Law 94-469), which gave the EPA authority to control the
production and use of chemicals in the United States. Under Section 6(e) of
TSCA the manufacture, processing, distribution in commerce, and use of PCB's
after January 1, 1978 was prohibited; however, the EPA may, by rule, allow a
particular use of PCB's to continue. In 1982, the EPA issued a final rule
on the use of PCB's in electrical equipment. This rule permits the use of
certain electrical equipment containing PCB's (e.g., small capacitors, large
capacitors, and transformers) to continue under specified conditions for
their remaining useful service lives.4 In 1985, the EPA issued a final
rule on the use of PCB's in electrical transformers. The use of high
secondary voltage network PCB transformers in or near commercial buildings
(approximately 7,400 transformers) after October 1, 1990, is prohibited.
Low secondary voltage network and high secondary voltage radial PCB
transformers in or near commercial buildings (approximately 70,200
transformers) must be equipped with enhanced electrical protection devices
by October 1, 1990, to avoid overheating from sustained electrical faults.10
Potential for Exposure to PCB's and Related Compounds Following Electrical
Equipment Fire or Failure
Fire-related incidents are defined as incidents involving electrical
equipment containing PCB's in which sufficient heat from any source causes
the release of PCB's from the equipment casing. In soot-producing incidents
an actual fire occurs in or near the PCB-containing electrical equipment
eventually resulting in exposure of the PCB's to extremely high temperatures
and in the formation and distribution of a black, carbonaceous material.
PCB's have been identified in soot following numerous electrical equipment
fires.11-17 Polychlorinated dibenzofurans
(PCDF's)11-15,17-20
and polychlorinated dibenzo-p-dioxins
(PCDD's)12-15,17-20 have also been
identified following this type of fire-related incident. Laboratory studies
have confirmed that PCDF's and PCDD's are formed from the pyrolysis of PCB's21-24 or
chlorobenzenes25 at temperatures ranging from 500° to 700°C
(932° to 1292°F).
In addition to PCDD's and PCDF's, other polychlorinated hydrocarbons have
been identified in soot from electrical equipment fires. Polychlorinated
biphenylenes,13,26
polychlorinated pyrenes,26 and polychlorinated
diphenyl ethers18 have been detected in soot
samples collected following capacitor or transformer fires.
Fire-related incidents in which soot is not produced have occurred from the
release of PCB's through the pressure relief valves of overheated
transformers.27-31 The pressurized release
of hot PCB vapors can entrain considerable quantities of liquid PCB's forming a
fine aerosol. Documented safety valve releases of PCB's from transformers
demonstrate that the aerosol can be distributed to areas beyond the transformer vault by
convective air
currents.27,28,30,31 Although PCB's manufactured in the
United States contained up to 2 micrograms of PCDF's per gram of PCB's
(µg/g),32 recent evidence indicates that additional PCDF's may be
formed as a result of the sustained high temperatures in non-soot-producing
incidents.31
Air, soot, and surface values for PCB's, PCDF's, PCDD's, 2,3,7,8-tetrachlorodibenzofuran
(TCDF), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
measured following fire-related incidents in the United States are presented
in Table 1.
An example of each type of fire-related incident involving PCB transformers
is described in the Appendix.
Exposure Limits
The Occupational Safety and Health Administration (OSHA) promulgated its
permissible exposure limits (PEL) of 1 milligram per cubic meter of air
(mg/m3) for chlorodiphenyl products containing 42% chlorine and
0.5 mg/m3 for chlorodiphenyl products containing 54% chlorine determined
as 8-hour time-weighted average (TWA) concentrations35 based on the 1968
Threshold Limit Values (TLVs) of the American Conference of Governmental
Industrial Hygienists (ACGIH).36 The TLVs, which have remained unchanged
at 1 mg/m3 (42%) and 0.5 mg/m3 (54%)
through 1985,37 are based on the
prevention of liver injury in exposed workers.38 The ACGIH Short Term
Exposure Limits (STEL) for chlorodiphenyls are 2 mg/m3 and 1 mg/m3 for
42% and 54% chlorine products, respectively. The OSHA PEL and the ACGIH TLV
and STEL values include a "Skin" notation which refers to the potential
contribution to overall exposure by the cutaneous route, including the
mucous membranes and eyes, by either airborne or direct skin contact with
PCB's.37
TABLE 1.
Concentrations of PCB's and Related Compounds Following Fire-Related Incidents
in the United Statesa
a - Values represent the highest measurements reported b - Micrograms per cubic meter (µg/m3) c - Micrograms per 100 square centimeters (µg/100 cm2) d - None detected, ND e - Values expressed as nanograms per square meter (ng/m2) f - Values represent total tetrachlorinated forms only h - Values represent results obtained in the presence of interfering chemicals i - Values reported as µg per wipe sample (area undefined)
Note:
Cap = Capacitor
Caps = Capacitors
Tran = Transformer
The National Institute for Occupational Safety and Health (NIOSH) recommends
that exposure to PCB's in the workplace be limited at or below the minimum
reliable detectable concentration of 1 µg/m3 (using the recommended
sampling and analytical methods) determined as a TWA for up to a 10-hour
workday, 40-hour workweek. The NIOSH recommended exposure limit (REL) was
based on the findings of adverse reproductive effects in experimental
animals, on the conclusion that PCB's are carcinogens in rats and mice and,
therefore, potential human carcinogens in the workplace, and on the
conclusion that human and animal studies have not demonstrated a level of
exposure to PCB's that will not subject the worker to possible liver injury.39
Toxicity
Results of Animal Studies
Effects of PCB's, PCDF's, and PCDD's
In general, the toxic responses observed in animals treated with PCB's,
PCDF's, or PCDD's are similar, but the potencies of individual compounds
vary according to the degree and position of chlorination. The tetra-,
penta-, and hexa-chlorinated isomer groups exhibit greater toxicity than the
other chlorinated forms.40-42 Dibenzofuran and dibenzo-p-dioxin
compounds with chlorine at positions 2, 3, 7, and 8 are particularly toxic43-45
The lethal doses in milligrams per kilogram of body weight (mg/kg)
for 50% (LD50) of the animals tested by the single oral administration of
PCB's, TCDF, or TCDD in four animal species are presented in Table 2.
Mice, rats, guinea pigs, and monkeys displayed progressive weight loss with
death occurring up to several weeks after administration of a single lethal
dose of PCB's, TCDF, or TCDD. Few other overt signs of toxicity were
observed in mice, rats, and guinea pigs. Monkeys exhibited facial edema,
loss of eyelashes and fingernails, and acneform skin
eruptions.46,48
Prominent histopathologic findings included: hepatic lesions in mice43
and rats,53 hyperplasia of the urinary tract epithelial tissues and
lymphoid hypoplasia in,46,48
and thymic atrophy in all four
animal species.
Adverse reproductive effects in experimental animals have been observed in
response to PCB's (rats, rabbits, monkeys, dogs, and pigs),39, TCDD (mice
and rats,54 and TCDF
(mice).55,56
Rats and mice exposed to PCB's39
or TCDD54 have developed liver cancers. No studies regarding the
carcinogenicity of PCDF's in animals have been reported.
Effects of Soot Containing PCB's, PCDF's, and PCDD's
A composite sample of soot collected following a transformer fire in
Binghamton, New York in 1981, contained 5,000 µg PCB's/g, 48 µg TCDF/g,
and 1.2 µg TCDD/g. Single oral administration to guinea pigs of the soot
in aqueous methylcellulose or of a benzene extract of the soot in the same
aqueous vehicle produced LD50 values of
410 and 327 mg/kg, respectively.
Single oral administration of TCDD in aqueous methyl cellulose or in corn
oil produced LD values of 19 and 2.5 µg/kg, respectively. Animals
surviving for 42 days after administration of the soot showed dose-related
evidence of decreased weight gain and kidney weight, thymic atrophy,
increased serum triglycerides, goblet cell hyperplasia of pancreatic
interlobular ducts, and metaplasia of salivary gland interlobular duct
epithelium. In rabbits, dermal application of the saline-moistened soot or
of a benzene extract of the soot at a dose comparable to 500 mg soot/kg body
weight for 24 hours produced hypertrophy of centrilobular hepatocytes in 50%
of the rabbits at the end of the 65-day observation period. No signs of
overt toxicity were observed in the rabbits, except dermal inflammatory
reactions noted in rabbits treated with the soot extract.57.
The dermal
LD50 of TCDD in rabbits is 275 µg/kg,47
while the dermal minimum
lethal dose of PCB's (as Aroclor 1260) is from 1.26 to 2.00 grams/kg.58
Because the measured amounts of TCDF and TCDD in the soot were low, other
congeners may have contributed to the toxic effects observed in guinea pigs
and rabbits.16,57
In a subchronic toxicity study, the total soot contained in food that was
consumed in 90 days by guinea pigs was 1.2, 22, 55, or 275 mg soot/kg body
weight. A fifth group of guinea pigs was terminated after 32 days (total
consumption of 400 mg soot/kg body weight) because mortality had reached
35%. The intensities of the toxic responses were dose-related, but no signs
of toxicity were detected in guinea pigs with a total consumption of l.2 mg
soot/kg body weight.59
Human Health Effects
Several cases of chloracne, hyperpigmentation, gastrointestinal
disturbances, elevated serum enzyme and triglyceride levels, and numbness of
the extremities have been reported among people exposed to
PCB's39,60,61
or PCDD's.54,62
Comparative human and animal studies indicate that
PCDF's were the main causative agents of similar symptoms reported in
individuals who ingested cooking oil Is contaminated with PCB's and
PCDF's63
There is suggestive evidence of associations between increased incidences of
cancer and exposure to PCB's,64 to PCB's containing significant
PCDF's,65,66
and to phenoxyacetic herbicides contaminated with PCDD's including
TCDD.67,68 However, definite causal relationships between exposure and
carcinogenic effects in humans remain unclear due to the inadequately
defined populations studied and the influences of mixed exposures.
The firefighters and other workers involved in the Binghamton transformer
fire cleanup have been followed through a medical surveillance program.
Medical evaluation of these workers approximately one year after the fire
showed slight increases in serum PCB levels but no observable adverse health
effects from this exposure.69 Selected workers
from this study group
have been found to have elevated adipose tissue levels of PCDF's and
PCDD's70
and associated histologic changes in the liver.71 Further
monitoring of this population is in progress.
Recommendations
There are several classifications for identifying a substance as a
carcinogen. Such classifications have been developed by the National
Toxicology Program (NTP),72 the International Agency for Research on
Cancer (IARC,73 and OSHA in its "Identification, Classification, and
Regulation of Potential Occupational Carcinogens" 29 CFR 1990,74 also
known as "The OSHA Cancer Policy." NIOSH considers the OSHA classification
the most appropriate for use in identifying potential occupational
carcinogens.* ,74
Because exposure to PCB's or TCDD has been shown to
produce malignant tumors in rats and mice, they meet the OSHA criteria.
Therefore, NIOSH continues to recommend that PCB's and TCDD be considered as
potential human carcinogens in the workplace. Limited evidence from animal
and human studies suggests that PCDF's may also pose a risk to human
health. As prudent public health policy, NIOSH recommends that occupational
exposure to PCB's, PCDF's, and PCDD's resulting from electrical equipment
fires or failures be controlled to the lowest feasible limit.
As a result of fire-related incidents involving PCB-containing electrical
equipment, emergency response personnel, maintenance and cleanup workers,
and building occupants may be at risk of exposure to PCB's, PCDF's, and
PCDD's. The following recommendations are intended to minimize worker
exposure to these compounds and reflect experiences NIOSH personnel and
others have gained in responding to such incidents. These recommendations
focus primarily on PCB transformer fires, although many of the
recommendations apply to other types of fire-related incidents involving
PCB's.
Recognition of Potential Hazard
Emergency response personnel should be informed of the presence of
PCB-containing electrical equipment and of the potential health hazards
associated with exposure to emissions from such equipment. All workers
should understand that exposure can occur through inhalation, ingestion, and
skin absorption (by direct contact or by contact with contaminated surfaces,
clothing, and equipment) and recognize that exposure to some of these
compounds may result in long term health effects.
Required registration of PCB transformers with local fire departments10
is intended to assure early recognition of the potential hazards when a
fire-related incident occurs. The registration for each transformer should
include: building location; location of transformers) within or near the
building; transformer serial number, manufacturer, and kilovolt/amperage
rating; and total volume and generic composition of the dielectric fluids.
This information should be readily accessible to those persons responsible
for the health and safety of emergency response personnel and others who may
come into contact with PCB transformers.
To assist in the identification of PCB transformers the effective use of
signs and labeling should be instituted. While labeling of PCB transformers
is required (using the mark "ML"),10 additional signs and labels should
be placed in areas near the location of a PCB transformers).
The number of emergency response personnel or cleanup workers entering a
potentially contaminated area(s), (e.g., interior of the building or
transformer vault) should be limited. This action would minimize the number
of workers exposed and would reduce the amount of protective clothing and
equipment potentially contaminated.
Assessment of Exposure
Contamination assessment is necessary to determine the extent and relative
degrees of contamination of an area following a fire-related incident.
NIOSH's Occupational Exposure Sampling Strategy Manual is useful in
developing appropriate strategies to monitor worker exposure to PCB's and
related pyrolysis products.75 Air and surface wipe samples should be
collected in all areas potentially contaminated by the incident. Air
sampling should include both the particulate and vapor phase. Wipe samples
should be taken on both vertical and horizontal surfaces. Additional
samples may include residual fluid in the transformer, fluid deposited in
the vault, or soot. Air and surface wipe samples should be analyzed for
PCB'S, tetra- through octa-chloro homologs of PCDF and PCDD, and the
respective 2,3,7,8-tetrachloro isomers. Detailed descriptions of sampling
and analytical techniques for PCB's may be found in the NIOSH Manual of
Analytical Methods.76,77 Sampling procedures and sensitive methods for
the analyses of PCDF's and PCDD's have been developed by the New York State
Department of Health16,78
Personal Protective Clothing
All workers who may be exposed to PCB's, PCDF's, and PCDD's should be
equipped with chemical protective clothing to ensure their protection. In
the selection of protective clothing, consideration should be given to the
utilization of disposable apparel because of life uncertainty of
decontamination of reusable clothing.
Outer protective garments should consist of a zippered coverall with
attached hood and draw string, elastic cuffs, gloves, and closure boots. If
exposure to soot is anticipated, workers should wear outer coveralls made of
a nonwoven fabric such as spunbonded Tyvek® to exclude particulates. If
exposure to liquids or to both soot and liquids is anticipated, or if the
form of the contaminants is unknown, the outer coveralss should be made of
chemically resistant materials such as Saranax®-coated
Tyvek or Viton®-coated neoprene. Gloves and boots should be made of neoprene,
nitrile, butyl rubber, or Viton which have been shown to be resistant to
permeation by PCB's.70,80 For personal comfort workers may wear inner
garments consisting of cotton coveralls, undershirts, undershorts, gloves,
and socks. Inner garments should be disposed of after use because small
amounts of contaminants may be transferred in removing outer garments.79
All disposable clothing should be placed in approved containers and disposed
of according to EPA disposal procedures.40
Respiratory Protection
The use of respiratory protection for those involved in cleanup operations
requires that a respiratory protection program be instituted which, at a
minimum, meets the requirements of 29 CFR 1910.13481 and that the
respirators selected be approved by the Mine Safety and Health
Administration (MSHA) and by NIOSH. The respiratory protection program
should include training of workers regarding the proper use, fit testing,
inspection, maintenance, and cleaning of respirators. The program should be
evaluated regularly.
Where a risk of exposure to airborne contaminants exists, such as when
visible quantities of soot are to be removed, workers should wear a
self-contained breathing apparatus with a full facepiece operated in pressure-demand
or other positive pressure mode. Alternatively, a
combination supplied air respirator, with full facepiece, operated in pressure-demand or
other positive pressure mode and equipped with auxiliary
positive pressure self-contained air supply can be used. When cleanup
operations have advanced to a point where airborne PCB's can no longer be
detected, air-purifying full facepiece respirators equipped with a high
efficiency particulate air filter and organic vapor cartridge should be
used, as a precaution, until final decontamination is completed.82
Decontamination and Worker Protection Programs
In general, decontamination procedures must provide an
organized process in which the extent and degree of contamination are systematically reduced.
This should include procedures that take into account containment,
collection, and disposal of contaminated solutions and residues generated
during the incident and cleanup. Separate facilities should be provided for
decontamination of large equipment. The EPA's Guide for Decontaminating
Buildings, Structures, and Equipment at Superfund Sites provides information
for developing a decontamination strategy.83
Each stage of decontamination, such as gross decontamination and repetitive
wash/rinse cycles, should be conducted separately, either by using different
locations or by spacing in time. Personnel decontamination locations should
be physically separated from the contaminated area(s) to prevent
cross-contact and should be arranged in order of decreasing level of
contamination. Separate entry/exit routes and locations should be well
marked and controlled. Access to the decontamination area should be
separate from the path between the contaminated and clean areas. Dressing
stations for entry should be separate from redressing areas for exit.
All reusable clothing and equipment should be grouped according to perceived
degree of contamination (i.e., high, moderate, or low) and thoroughly
cleaned. Decisions concerning decontamination end points are often based on
the lack of visible contamination; however, the absence of observable
surface contamination does not necessarily indicate the absence of
contaminants absorbed into the material. Reusable clothing and equipment
should, therefore, be analyzed for residual contamination before reuse or
storage.
Soot from transformer fires is typically black, friable, carbonaceous
material. Preliminary cleanup of the areas visibly contaminated with soot
should involve dry vacuuming of both horizontal and vertical surfaces with a
vacuum cleaning system equipped with a high efficiency particulate (HEPA)
filter.
Final cleanup methods should include washing surfaces with alkaline27 or
nonionic84 synthetic detergents in water. The addition of a caustic
agent, such as trisodium phosphate, may help to remove grease deposits,
floor waxes, and furniture polishes. Waxed and polished surfaces tend to
absorb contaminants from the air. Cleaning with organic solvents is useful
for nonporous electrical and mechanical equipment where contact with
water-based cleaning fluids may damage the equipment. Organic solvents,
such as kerosene, mineral spirits, and trichlorotrifluoroethane, may carry
contaminants deeper into porous materials and should not be used on these
surfaces. Complete decontamination of porous surfaces, such as concrete and
masonry surfaces in vaults, may not be possible; therefore, application of
an elastomeric, abrasion- and flame-resistant sealant may be required.
Post-Decontamination Testing
The adequacy of the decontamination effort should be determined by followup
sampling and analysis of the contaminated areas and reusable protective
equipment. This testing should be conducted as each area is decontaminated
and again after the entire facility has been cleaned. Decontamination
guidelines for the cleanup of specific buildings following fires involving
PCB transformers83,85 have been proposed by the New York State Department
of Health,86 the New Mexico Expert Advisory Panel,87 the California
Department of Health Services,88 and the San Francisco Department of
Health.89
Medical Surveillance
A medical surveillance program should be established to prevent (or to
attempt to detect at an early stage) adverse health effects in workers
resulting from exposure to PCB's or related compounds. Medical and work
histories, including previous exposure to PCB's or other toxic agents,
should be taken for each worker prior to job placement and updated
periodically. The physician responsible should be provided with information
concerning the adverse health effects from exposure to PCB's and related
compounds and an estimate of the worker's potential exposure, including any
available workplace sampling results and a description of all protective
clothing or equipment the worker may be required to use.
The examining physician should direct particular attention to the skin,
liver, and nervous system as these are the most likely targets of exposure
to PCB's and related compounds. Blood determinations which reflect liver
function may be useful. Measurement of blood PCB's may also be useful but
should not be interpreted as a sensitive indicator of acute exposure.
Adipose tissue levels of PCB's, PCDF's, and PCDD's are indicative of total
body burden, but these tissue samples are not routinely available. Further
studies of exposed populations will permit more definitive medical
monitoring recommendations.
*"'Potential occupational carcinogen means any substance, or combination or
mixture of substances, which causes an increased incidence of benign and/or
malignant neoplasms, or a substantial decrease in the latency period between
exposure and onset of neoplasms in humans or in one or more experimental
mammalian species as the result of any oral, respiratory or dermal exposure,
or any other exposure which results in the induction of tumors at a site
other than the site of administration. This definition also includes any
substance which is metabolized into one or more potential occupational
carcinogens by mammals" (29 CFR 1990.103). [return to text]
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APPENDIX
Reports of Fire-Related Incidents Involving PCB Transformers
Fire in a Multi-Story Office Building in Binghamton, New York
On February 5, 1981, an electrical fire occurred in the switchgear adjacent
to a PCB transformer in the basement mechanical room of the Binghamton State
Office Building. The transformer contained 1,060 gallons of askarel
consisting of Aroclor 1254 (65%) and a mixture of tri- and tetra-chlorinated
benzenes (35%). A ceramic bushing on the transformer cracked during the
fire, resulting in the release of approximately 180 gallons of askarel onto
the floor near the fire. The smoke was distributed by convection throughout
the building through an open vertical shaft that extended from the
mechanical room to the top of the building. The shaft contained the duct
for the exhaust air from the restrooms on all the floors. The shaft and
ducts were not airtight and allowed smoke and soot to contaminate the work
areas of the building air conditioning ducts, false ceiling areas, and
elevator shafts.13
Analyses of the soot revealed significant concentrations of PCB'S, PCDF'S,
TCDF, PCDD'S, TCDD, and polychlorinated
biphenyls.13,16,90
Based on analyses of dry surface wipe samples, horizontal surfaces showed higher
levels of contamination than vertical surfaces.17 In soot samples
obtained from 11 floors of the building, the absolute amounts of the tetra-
through octa-chlorodibenzofuran (CDF) isomer gifts varied from sample to
sample, but the relative proportions with respect to the amount of PCB in
the soot were consistent. The ratio of PCDF to PCB averaged 0.067 + 0.026
(+ one standard deviation).16
Air samples collected on the seventh floor after cleanup of most of the
surface soot deposits contained 292 picograms of total tetra-CDF per cubic
meter of air (pg/m3) including 26 pg TCDFF/m3
and 5 pg total
tetra-chlorodibenzo-p-dioxin (CDD)/m3 including 3 pg
TCDD/m3,16
The cleanup of the Binghamton building has been complex and costly. The
building remains closed to normal use pending complete cleaning and
renovation. Criteria for reoccupancy are being considered by the New York
State Department of Health Expert Advisory Panel based on toxicity studies
in guinea pigs using the soot from the building, on chemical analyses of the
soot, and on published toxicologic studies of TCDD.86
Electrical Malfunction in an Office Building in Santa Fe, New Mexico
On June 17, 1985, an electrical malfunction occurred in a transformer
located in the basement transformer vault in the main building of the New
Mexico State Highway Department Office Building. The transformer contained
245 gallons of askarel consisting of Aroclor 1260 (87%) and a mixture of
tri- and tetra-chlorinated benzenes (13%). The electrical malfunction
caused the transformer to overheat resulting in the release of vaporized
askarel through the safety valve which continued until the unit was
de-energized (approximately 65 minutes after initial detection). There was
no fire, but charred (blistered) paint on the transformer casing indicated
that the temperature of the casing may have approached 316°C (600°F).
The emission products were distributed throughout the 2-story building by
convective air currents and by mechanical transfer via the heating,
ventilating, and air conditioning systems. Because the emitted vapor
condensed as it reached cooler temperatures, the askarel apparently "rained"
in the heavily contaminated rooms adjacent to and above the basement
transformer vault.
Air, fluid, and surface wipe samples were collected within 7 days of the
incident. Airborne concentrations of PCB's in the main building were
41.94 µg/m3 inside the vault, 0.34-25.87 µg/m3 in other basement
areas, 1.00-19.45 µg/m3 in first floor areas, and 0.73-5.96 µg/m3 in
second floor areas. PCDF's were detected at concentrations ranging from
10.4 to 501.6 µg/m3 including 0.9-56.2 pg TCDF/m3. Airborne PCDD's
ranged from 7.1 to 21.0 pg/m3 but TCDD was not detected.
The surface concentrations of PCB's were as high as 280,000 /µg/l00 cm2
in basement areas, 98,000 µg/100 cm2 in first floor areas, and
190 µg/l00 cm2 in second floor areas. PCDF'S, TCDF, and PCDD's were
present in surface wipe samples from areas of the basement and first floor,
but TCDD was not detected. Surface wipe samples from second floor areas
were not submitted for measurement of the pyrolysis product.31
The New Mexico PCB Expert Advisory Panel convened on July 16, 1985, to
propose air and surface cleanup guidelines for the building. The guidelines
were based on the potential risk of cancer resulting from exposure to PCB'S,
PCDF'S, and PCDD'S. Animal studies on the carcinogenicity of TCDD were used
to estimate the potential cancer risks. It was also necessary to make
certain judgments and assumptions regarding the toxicity of the related
compounds and the potential for exposure to occupants of the building. The
guidelines are intended to maintain the risk of developing cancer below one
in one million for a person spending the rest of his/her working lifetime in
the building. The Panel recommended cleanup levels of 2 pg TCDD
equivalents/m3 of air and 1 ng TCDD equivalents/m2 of surface area.
Values for other PCDF and PCDD isomer groups can be converted to TCDD
equivalents using the following conversion factors:
To Convert Values to TCDD Equivalents
PCDF's
Factor
PCDD's
Factor
TCDF
0.33
TCDD
1.0
Other tetra-CDF's
0.0
Other tetra-CDD's
0.0
Penta-CDF's
0.17
Penta-CDD's
0.5
Hexa-CDF's
0.005
Hexa-CDD's
0.02
Hepta-CDF's
0.0005
Hepta-CDD's
0.0
Octa-CDF's
0.0
Octa-CDD's
0.0
Concentrations of these compounds can be converted to TCDD equivalents by
multiplying the measured values by the appropriate conversion factor. The
TCDD equivalents can then be summed and compared to the guideline values.
The Panel did not establish cleanup guidelines for PCB's on
surfaces.87
Copies of this and other NIOSH documents are available from: