United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
Research and Development
EPA 600/S6-82-003F Sept. 1984
Project Summary
Carcinogen Assessment of
Coke Oven Emissions
The final report summarized herein is
a source document developed primarily
for use by the Office of Air Quality
Planning and Standards, United States
Environmental Protection Agency, to
support decision-making regarding
possible regulation of coke oven emis-
sions as a hazardous air pollutant.
In the development of the assessment
document, the scientific literature was
inventoried and key studies were
evaluated. The carcinogenicity and
related characteristics of coke oven
emissions are qualitatively identified.
Measures of dose-response relation-
ships relevant to ambient exposures
and adverse health responses in the
prospective observed environmental
levels are also discussed.
This Project Summary was developed
by EPA's Office of Health and Environ-
mental Assessment, Washington, DC,
to announce key findings of the research
project that is fully documented in a
separate report of the same title Jsee
Project Report ordering information at
back).
Introduction
Coke is a porous, cellular carbon
residue produced from the carbonization
of soft (bituminous) coal and used
primarily in the steel industry's blast
furnaces to make iron that is subsequent-
ly refined into steel.
A typical coke oven is 10 to 22 feet high,
36 to 55 feet long, and approximately 18
inches wide. A coking facility generally
contains several batteries and each
battery consists of 20 to 100 ovens. The
coking cycle begins with the introduction
of coal into the coke oven (charging) by
means of a mechanical larry car which
operates on rails on top of the battery.
During the charging process the lids on
the charging holes are removed and the
oven is placed under steam aspiration.
This operation limits the escape of gases
from the oven during charging so that
they can be collected in the byproduct gas
collector main for subsequent processing.
Following the heating of the coal at 1046°C
(1900°F) to 1100°C (2000°F) for 16 to 20
hours, the doors on each side of the oven
are removed, and the coke is pushed by a
mechanically operated ram into a railroad
car called the quench car. The quench car
is then moved down the battery to a
quench tower where the hot coke is
cooled with water.
where the hot coke is cooled with water.
The reactions taking place in the coke
oven can be characterized in three parts.
In the first step, coal breaks down at
temperatures below 700°C (1292°F) to
primary products consisting of water,
carbon monoxide, carbon dioxide, hydro-
gen sulfide, olefins, paraffins, aromatic
hydrocarbons, and phenolic-containing
and nitrogen-containing compounds. The
second step occurs when the primary
products react as they pass through the
hot coke and along the heated oven walls
at temperatures above 700°C (1292°F).
This step results in the formation of
aromatic hydrocarbons and methane; the
evolution of hydrogen; and the decompo-
sition of nitrogen-containing compounds,
hydrogen cyanide, pyridine bases, ammo-
nia, and nitrogen. The third step is the
formation of hard coke by the progressive
removal of hydrogen.
Human exposure to coke oven emis-
sions occurs as a result of emissions
released during the charging, coking
(door, topside port, and offtake system
leaks), and pushing operations. During
these operations large quantities of
sulfur dioxide, organic vapors, particu-
lates, and coal tar pitch volatiles absorbed
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to particulates can be emitted to the
atmosphere. A detailed list of constitu-
ents found in coke oven emissions is
given in the final report.
The Occupational Safety and Health
Administration (OSHA) set a comprehen-
sive standard for coke ovens emissions (29
CFR 1910.1029). This OSHA standard
included requirements for exposure
monitoring; medical surveillance; use of
respirators, protective clothing, and
equipment; training and education; and
hygiene facilities and practices. The
permissible exposure limit (PEL) as
defined by the standard is an 8-hourtime-
weighted average of 150 mg/m3 of the
benzene soluble fraction of total panicu-
late matter.
Summary
Qualitative Assessment
The production of coke by the carboni-
zation of bituminous coal leads to the
atmospheric release of chemically com-
plex emissions from coke ovens. The toxic
constituents include both gases and
respirable paniculate matter of varying
chemical composition. The emphasis in
this document is on the toxic effects of the
paniculate phase of the coal tar pitch
volatiles (CTPV) emitted from coke ovens,
principally becuase this fraction contains
polycyclic organic matter; however, the
document also discusses the potential
carcinogenic and/or cocarcinogenic
effects of aromatic compounds (e.g.,
beta-naphthylamine, benzene), trace
metals (e.g., arsenic, beryllium, cadmium,
chromium, lead, nickel), and gases (e.g.,
nitric oxide, sulfur dioxide), which are
also emitted from coke ovens.
The literature contains an extensive
epidemiologic study of coke oven workers
conducted at the University of Pittsburgh
which showed that workers exposed to
coke oven emissions are at an increased
risk of cancer. A dose-response relation-
ship was established in terms of both
length of employment and intensity of
exposure according to work area; i.e., at
the top or the side of the coke oven. The
relative risk of lung, trachea, and bron-
chus cancer mortality in 1975 was 6.94
among Allegheny County, Pennsylvania
coke oven workers who had been em-
ployed five or more years through 1953
and worked full-time topside at the coke
ovens. By comparison, side oven workers
employed more than five years and
followed through 1975 had a relative risk
of 1.91, while nonoven workers employed
more than 5 years had a relative risk of
1.11. Deaths from malignant neoplasms
at all sites were also found to be dose-
related among the Allegheny County
workers. Among non-Allegheny County
coke oven workers employed more than
five years at time of entry to the study
(1951-1955), the relative risk in 1975 of
cancer of the lung, trachea, and bronchus
was 3.47 for full-time topside, 2.31 for
mixed topside and side oven, and 2.06 for
side oven. Although adequate smoking
data were not available for either the
Allegheny County or non-Allegheny
County workers, it is not likely that
differences in smoking habits could be of
sufficient magnitude to negate the dose-
response effect. In addition to elevated
mortality from cancer at all sites, and
elevated mortality from cancer of the
lung, trachea, and bronchus, there was
significant (P < 0.05) excess kidney
cancer mortality amoung white coke oven
workers in Allegheny County (relative risk
in 1975 of 8.50 for those employed five
years or more through 1953 and 5.42
years for those ever employed through
1953). Prostate cancer mortality was
found to be elevated significantly (P <
0.05) for the nonwhite non-Allegheny
County coke oven workers ever employed
or employed for five years or more
(relative risks of 2.45 and 3.59 respectively
in 1975) and for all workers at the coke
ovens in Allegheny County ever employed
through 1953 (relative risk of 1.67 in
1975).
Extracts of a topside coke oven sample
and a sample obtained from a coke oven
collecting main were shown to have skin
tumor initiating activity in initiation-pro-
motion studies in SENCAR mice. Coal tar,
a condensate from coke oven emissions,
was shown to be a skin carcinogen in
several animal studies. Coal tar aerosols
have been found to cause tumors of the
lung in mice. Numerous other animal
studies have shown constituents of coke
oven tar and coke oven emissions to be
carcinogenic.
Mutagenicity tests on the complex
mixture of solvent-extracted organics of
coke oven emissions were positive in
bacteria. A complex mixture from the
coke oven collecting main was mutagen-
ic in bacteria and mammalian cells in
vitro. In addition, a number of components
identified in coke oven emissions are
recognized as mutagens and/or carcino-
gens. Cell transformation was found in
Balb/C 3T3 mouse embryo fibroblasts
and Syrian hamster embryo cells treated
with solvent-extracted organics of air
particulates collected topside of a coke
oven; however, these studies involve
possibly significant contamination of the
sample with ambient air particulates.
Quantitative Assessment
Several approaches are available to
estimate the human lifetime respiratory
cancer death rate from a continuous expo-
sure of 1 yug/m3 of the benzene soluble
organics (BSD) extracted from the
particulate phase of CTPV from coke
ovens emissions.
Using a Weibull-type model, the
estimated risk due to a 1 //g/m3 unit
exposure ranges from 1.30 x 10"8 for the
95% lower-bound zero lag-time assump-
tion to 1.05 x 10~3 for the 95% upper-
bound 15-year lag-time assumption.
Using a multistage-type model,the maxi-
mum likelihood estimates for the risk due
to unit exposure range from 1.76x10"6for
the zero lag-time case to 6.29 x 10~4 for
the 15-year lag-time case.
Since it is not known whether either of
these models reflects the true dose-
response relationship at low doses, a
range of estimates from zero to an upper
bound is a more appropriate indicator of
potenial risk. To obtain this upper bound,
a linearized modification of the multistage
model is used, giving a unit risk value of
1.26 x 10~3 as the highest potency
amongst the four lag-time data sets. The
lower bound of the range approaches
zero.
A composite unit risk estimate is
obtained from the multistage 95% upper-
bound estimates for each of four lag-
times by taking their geometric mean.
This results in a composite estimate of
6.17x10~4, which is regarded as the most
plausible upper-bound estimate.
It should be noted that the ranges of
these results do not reflect the total
uncertainty connected with these esti-
mates. Other factors that could change
the results, such as cigarette smoking
rates and sex-race sensitivity differences,
were not accounted for due to lack of
sufficient information.
Conclusions
Coke oven workers were found to be at
an excess risk of mortality from cancer at
all sites, and from lung cancer, prostate
cancer, and kidney cancer as a result of
exposure to coke oven emissions. These
risks may have been enhanced by
smoking but are not believed to have been
confounded by smoking. Both an extract
from a coke oven main and coal tar, a
condensate of coke oven emissions, were
found to be carcinogenic in animal skin
painting studies. In multiple experiments,
mice exposed to coal tar aerosol devel-
oped lung tumors. Sample extracts from a
coke oven topside sample and coke oven
main initiated tumor formation in initia- (
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ion-promotion studies in mice. Coke
oven door emissions were found to be
mutagenic in bacteria. Numerous con-
stituents of coke oven emissions are
known or suspected carcinogens.
The findings of this document consti-
tute sufficient evidence for carcinogeni-
city in humans, and sufficient evidence for
carcinogenicity in experimental animals
if the International Agency for Research
on Cancer (IARC) criteria were used for
the classification of carcinogens. There-
fore, coke oven emissions would be
classified in IARC category 1, meaning
that this mixture is carcinogenic to
humans.
Using a linearized multistage model
and averaging the upper-bound estimates
from multiple data sets, the most plausible
upper-bound unit risk estimate is approx-
imately 6.2 x 10~". This value is the
estimated individual lifetime risk associ-
ated with a continuous exposure of 1
/ug/m3 of coke oven emissions in ambient
air.
This Project Summary was prepared by staff of the Carcinogen Assessment
Group, Office of Health andEnvironmentalAssessment, USEPA, Washington,
DC 20460.
Herman J. Gibb is the EPA Project Officer (see below).
The complete report, entitled "Carcinogen Assessment of Coke Oven Emissions,"
(Order No. PB 84-170 182; Cost: $19.00, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
U S GOVERNMENT PRINTING OFFICE, 1984—759-015/7830
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