Interim Evaluation, cf Health Risks Associated with
Emissions of Tetrachlorinated Dioxins
From i'.unicical Waste Resource Recoverv Facilities
Move-mber 1981 .
.**•
Background
Concern has been raised within the United States regarding
the possible emission of trace amounts of highly toxic organic
pollutants as *a consequence of the large scale combustion of
municipal wastes for recovery of energy. Such resource recovery
facilities are also referred to.as municipal waste combustors.
The concern first came to a focus at the Herapstead Resource
Recovery Corporation (HRRC) facility in He.mpstead, Long Island,
where in 1979 the owners and operators of the plant permitted
SPA to sample its emissions. Subsequent analyses indicated that
tetrachlcrodibenzc-p-dioxins (TCDDs), including 2,3,7,3-TCDD,
were present. However, due to the nature of the sampling method
and the operating conditions of the -plant at the time, only a :
qualitative statement could be made on the presence of these
materials. Based on these findings the Agency concluded that
more rigorous testing would-be required in order to quarltitate1
the results.
3y the time this qualitative information was becoming
available, the Exposure Evaluation Division (EED) of the Office
of Pesticides and Toxic Substances (OPTS) had already initiated
-------
a oilot study of emissions front two other municipal waste conbus-
tors in the United States. In addition, the Office of Solid
Waste (OSW) had begun a series of similar studies to determine
whether or not ootential problems existed at other municipal
*" *^
waste combustors. The analytical results from five plants are
now available.
Even before the above data became available to the Agency,
a considerable amount of information had been accumulated by
scientists working on similar and related facilities outside the
United States. In 1979 a report appeared OP. the analysis of a
number of micro-pollutants,, including TCDDs, in fly ash from five
municipal incinerators in The Netherlands, Canada, and Japan
(Siceman, et. al, 1979). This was followed in the next year by
an investigation of fly ash and stack emissions from four
municipal incinerators in Italy (Cavallaro, et al, 1930) and
by an extensive review (Lustenhouwer, et al, 1930) on the amounts
of micro-pollutants found in. the fly ash of various municipal
incinerators in Europe. Amplification of this information was
provided in testimony presented during EP.Vs cancellation hearings
on the herbicide 2,4,5-T (Hutzinger, 1980). Each of these inves-
tigators reported TCDDs in the emissions and fly ash of muni-
cipal incinerators.
The Agency's review of the foreign" data did not suggest the
existence of any problem that called for precipitous action due to
the emission of TCDDs associated with the combustion of municipal
-------
wastes. The Agency continued its program of systematic testing
at municipal waste ccmbustors in order to assess the domestic
situation more completely.
Mow that the S?A-generate~d emissions data from American
*^
municipal waste combustors are available, it is appropriate to
publish an interim assessment of the toxic effects which could
conceivably be associated with TCDDs emissions from municipal
waste combustors in this country.
Overview
The human health implications associated with the emission
of TCDDs from five municipal waste combustors have been assessed.
The evaluation was based, on the information available on the
estimated levels of the exposure that people living near municipal
waste combustors are likely to experience, and on estimates of
health hazards associated with TCDDs. The Hempstead, Long Island
plant is not one of the five analyzed as the EPA data for this
plant are r.ot sufficient to support a quantitative evaluation.
Exposure information on TCDDs was obtained by field sampling
of stac>: emissions from the five municipal waste combustors,
followed by complex chemical analyses for TCDDs. To obtain an
estimate of the amount of TCDDs that were emitted into the atmo-
sphere, it was necessary to collect and analyze both the flue-gas
and the particulate materials as TCDDs have a tendency to firmly
adhere to small particles (Lustenhouwer, e_t a_l, 1980).
-------
- 4 -
Computer modeling was used to derive approximate exposure
levels experienced by the population as a result of the dilution
and dispersion that takes place as the flue-gas and particulate
material make their way ,to ground-level after stack emission.
Estimates of the risk to human health from these TCDDs
emissions were obtained by extrapolating from animal data on the
basis of an important assumption. The levels of exposure are
far below those causing acute (short term/ high dose) effects- in
v-
animals. Therefore, this assessment focuses on chronic (long
term, low dose) effects with an emphasis on the two most sensitive
toxic effects seen in animals: reproduction and carcinogenicity.
The fundamental assumption that was made was that if TCDDs
are a human carcinogen, or if they pose a health hazard due to
adverse reproductive effects in humans, then these effects will
be manifested at the same relative dose levels as observed in the
recorted animal studies, taking the relative body surface of
animals and humans into account. The inclusion of this
assumption is essential in the interpretation of the significance
that animal data may have with regard to any human experience.
The exposure data and the health hazard information on TCDDs were
then combined in a number of mathematical models to estimate
the risk associated with human exposure to TCDDs emitted from
municipal waste combustors.
-------
Toxicitv Data-
Althouqh there are a total of 22 tetrachlorodibenzo-o-dioxin
(TCDD) isomers, the 2,3,7,3-TCDD isomer has been subjected to the
most extensive testing. While a variety of studies point to a
range of effects produced by this material, the appearance of
adverse reproductive and carcinogenic effects at very low doses
in chronic feeding studies in animals has generated special
interest and concern.
The effects of a combination of isomers is difficult to
•=?
assess, but a conservative assumption is that all of the
isomers are as toxic as 2,3,7,8-TCDD. There are biochemical
reasons, supported by some 'experimental data (Poland, et. a_l,
•
1979), to suggest that the mechanism of toxic action of 2,3,7,3-
TCDD is associated with the chlorine atoms on the lateral ring
positions (positions 2, 3, 7. and 3). In fact, there is no
evidence to indicate that any of the isomers are more toxic than
2,3,7,3-TCDD.
Data on the other chlorinated dioxir.s were insufficient to
be included in this interim assessment.
A. Reproductive effects of 2,3,7,8-TCDD
2,3,7,3-TCDD has been investigated and shown to have
reproductive effects in numerous animal studies. In one
of the most recent studies, a three-generation study in
rats (Murray, et, a_l, 1979), adverse reproductive effects
appeared inconsistently in the different generations
at the lowest dose tested (0.001 ug TCDD /kg /day),
-------
although this nay be at or very close to the "no-observed
-effect level" (HOED. Human epidemiological
studies in this area are limited in number and
statistical power; those that have been conducted do not
demonstrate clear exposure-related effects.
3. Carcinogenicity of 2,3,7,8-TCDD
Bioassays have demonstrated that 2,3,7,8-TCDD is an
animal carcinogen in rats and mice (Kociba, et al.,- 1978;
national Cancer Institute, 1980), under the test conditions
imposed. The information with respect to human exposure
is less conclusive. Epidemiological studies of cohorts
of workers engaged in chlorophenol production and use,
and their exposure to TCDDs in this country (Zack and
Suskind, I960; Cook, et al, 1980), suggest that any overall
carcinogenic effect on humans is small. A significant
excess of stomach cancer, however, has been reported in a
similar cohort of German workers (Theiss, e_t al, 1931).
In addition, a recent series of reports (P.ardell and
Sandstrom, 1979; Eriksson, et al, 1981; Honchar and
Halperin, 1981; Cook, 1931) indicate that soft tissue
sarcomas (a form of cancer) may be associated with long
term exposure to phenoxy herbicides which contain 2,3,7,8-
TCDD. The human information available from the Seveso,
Italy explosion in 1976 has not indicated that the local
populations have developed any excess of cancer. However,
-------
-. 7 -
it nay.be too early to evaluate the long term effects
from this exposure (Reggiani, 1980) in view of the short
period of time that has'elapsed since the Seveso incident
and the generally longer latency period for cancer develop-
ment, itore definitive work to address, this question has
*^ -
been initiated by the National Institute of Occupational
Safety and Health (MIOSH) and the National Cancer Institute
(MCI).
Exposure Data
There are* about 40 municipal waste corabustors in the
country. A. large number of additional units are under consider-
ation for construction, some of them involving very different
technologies. Consequently, the recently obtained emission
data from the stacks of five municipal waste combustors cannot
be said to characterize totally the industry today nor what
the industry is likely to become (see Tables 1 and 2). However,
the data can give some indication of current conditions and
what niicht ce expected in the future as data collection, proceeds.
In order to analyze these data more completely, information is
needed on the interaction between the various factors that may
affect the output of dioxins from municipal .waste combustors.
Included among these are the .nature of the combustible materials,
temperature, flow rate, process, stack heights, local topography,
and/or combustion chamber design.
-------
- a -
In the present estimates, the relation between the emission
data and the maximum concentration to which people in the sur-
rounding area are likely to be exposed has been obtained-throuch
a theoretical air dispersion model, PTMAX (EPA, 1977). This
computer program calculates the location and magnitude of the
maximum short term (1 hour) concentration in the area around
the stack. Data from the five sampled sites provided the
input. Basically, the results show.the ground concentration
to be a slowly varying function of stack height, temcerature,
«*
diameter, and exit velocity. To obtain annual maximum average
ground level concentrations, reasonable, if rough, estimates
were made on the assumption that the maximum annual average
concentration is 1/40 of" the maximum hourly concentration (see
Table 3) (Tikvart, 19SI). While there is no guarantee that the
results of future studies (some are already in progress and
will continue through FY 32) will fall within these ranges,
the current data can be used to suggest the range of variations
that is expected to be encountered.
Toxicity and Exposure Assumptions
Emission data can be used with other data to estimate
potential human exposure to TCDDs from municipal waste combustion
sources. However, many unanswered questions relating to TCDDs1
toxicity and exposure remain. Since there are insufficient data
to answer these important questions and because this information
is needed to assess the risk to people breathing emissions from
-------
- 9 -
the stack, the Agency has adopted a series of assumptions which
are designed to represent the "worst case" possible. Some of
these questions and related assumptions are presented below:
1. What are the tpxicological properties of the different
TCDD isomers? (There are considerable experimental
data on the properties of 2,3,7,3-TCDD, but relatively
little on the other 21 isomers. The evidence that
does exist, however/ suggests that they may be less
toxic than 2,3,7,8-TCDD.)
In the absence of data the assumption is:
The carcinogenic properties and reproductive effects
of all TCDDs are the same as that of 2,3,7,8-TCDD.
2. Given the'concentration and composition of TCDDs mea-
sured in emissions from a stack, what are the resulting
air concentrations and compositions at ground level to
which people would be exposed? In the absence of data
the assumption is:
The PTMAX air dispersion model (EPA 1977) and the
factor used to convert to the annual concentration,
adequately represent the transport of the emissions
to ground level. The composition of emission produces
found at ground level is identical to the composition
(but not the concentration) in the stack.
-------
- 10 -
3. How does the ground level concentration vary relative
to the position from the stack? In the absence of
data the assumption is:
All of the exposed population is subjected to the
maximum average annual concentration found at the
point of concentration.
4. How do the TCDD concentrations in the air behave when
they- are breathed by humans? (The TCDDs in the stack
gases are generally associated with particulate matter
from which they are difficult to remove in the labora-
tory) . In accord with available data (ICR?, 1963)
the assumption is:
Seventy-five percent of the inhaled particles are
retained in the body.
In the absence of data the assumption is:
All the TCDDs that are retained in the respiratory
tract are biologically available to the organism.
5. How often and for how long will people be subject to a
given level of exposure? (The lifetime of municipal
waste combustors is approximately 30 to 40 years.)
Even given this approximation, the following is assumed;
The copulation is exposed to this maximum average
annual concentration from the source for 24 hours a
dav throuchout a 70 year lifetime.
-------
- 11 -
6. What is the relative sensitivity of man versus the
animals used in these studies?
In the absence of data the assumption is:
Man is of comparable sensitivity to animals for
reproductive and carcinogenic effects, taking body
surface areas into account.
Health Risk Estimates
The health risk estimates were calculated using a variety
of mathematical models - linearized multi-stage (Crump, 1981):
probit, logit, Weibull and gamma multi-hit (Food Safety Council,
1980) - which were applied to the rat carcinogenicity data
(Kociba, 1978) and the TCDDs exposure data associated with the
emissions from municipal waste combustors". The results from
the models were consistent in estimating low risks.
Potential reproductive effects were assessed by comparing
the calculated levels of exposure from TCDDs to the lowest
level tested in animals (Murray, et al, 1979). The anticipated
levels of TCDDs to which humans may be exposed are far below
the level used in the animal study.
Summary
An evaluation of the public health considerations related
to TCDDs emissions has been made by applying the various mathe-
matical models to the data.from the five US sites under the
many combinations of assumptions that must be made in analyzing
-------
- 12 -
the data. Those estimates suggest that the present emissions
levels of TCDDs from the five municipal waste combustorg
described in this report do not present a public health hazard
for residents living in the immediate vicinity. . In addition,
the health risk estimates presented in the assessment indicate
that as long as emission levels of TCDDs do not greatly exceed
the emissions measured at the five US sites evaluated in this
interim assessment, there should be no reason for concern. This
•i»-
conclusion is valid for all toxicological effects (including
reproductive and cancer) for which the available animal and
human data have been analyzed.
This is an interim report and EPA intends to periodically
monitor representative resource recovery facilities such as these
for emissions of TCDDs. EPA will take steps to regulate TCDDs
emissions if it appears necessary. However, at the present
time, this need has not been demonstrated.
-------
References
/ Cavaliaro, A.', et al. 1980. Chemosphere, 9_, 611.
Cook, R.R., et al. 1980. J. Occup. !1ed. , 22, 530.
Cook, R.R. 1981. Lancet/ 618.
Crump, K.S. 1981. "An Improved Procedure for Low Dose
* -
Carcinogenic Assessment from Animal Data".- MISHS
Contract No. MIH S-S-77-22. J. Environ. Path, and Tox. £, 675
/x-Eiceman, G.A. , et al. 1979. Anal. Chem. , 51,f 2343.
Srikson M., et al. 1981. J. Ind. tied., 38, 27.
EPA. 1977. ^Guidelines for Air Quality Maintenance Planning
and Analysis". Vol. 10 (Revised): Procedures for Evaluating
Air Quality Impact of New Stationary Sources.
Food Safety Council. 1980. Final report of the
Scientific Committee.
Hardell, L. and A. Sandstrom. 1979. Br. J. Cancer, 3_9, 711.
Honchar, ?. and W.E. Ealperin. 1981. Lancet, 268.
Hutzinger, 0. 1930. Testimony submitted to EPA administrative
hearings on the cancellation, of 2,4,5-T and silvex.
International Commission on Radiation Protection (ICR?)
Publication No. 10 Report of Committee IV. 1968. 3.
Kociba, R.J., et al. 1978. Tox. Appl. Pharm., 4±, 279.
Lustenhouwer, J.W.A., et al. 1980. Chemosphere, .9, 501.
Murray, F.J., et al. 1979. J. Appl. Pharm, 5£, 241.
National Cancer Institute. 1980. Publication
Number (NIH) 80-1757 and 80-1765.
-------
- 2 -
Poland, A., et al. 1979. Ann. NY Acad. Sci., 32®.' 214'
Reggiani, G. 1980. Oral testimony in EPA 2,4,5-T Cancellation
Hearings, Transcript pages 16-761 - 16766.
Theiss, A.M., efc al. 1981. In press.
Tikvart, J. 1981. Personal Communications with Randolph
ChrisTnon.
Zack, J.A, and R.R. Suskind. 1980. J. Occup. Med, 22, H-
-------
TABLE 1
RANGE OF STACK CONCENTRATIONS
Pollutant(s) Range (ng/dscm~)
2,3,7,8-TCDD MDh - 3.5C
TCDDsd ND - 3.5
a - ng = 10~^ grams; dscm = dry standard cubic meter
•*:
b - "I7D" not detected at a detection limit of 0.25 ng/dscm.
c - The analytical method used could not distinguish 2,3,7,8-TCDD
from several of the other TCDD isorners. It is recognized
that some molecular forms may be co-eluting with the 2,3,7.3
f
isomer; therefore this value could be an overestimate of the
amount of 2,3,7,3-TCDD actually present.
d - "TCDDs" includes any and all of the tetrachlorodibenzo-?-dioxin
isomers present.
-------
TABLE 2
RANG5 OF STACK PA3AF1ETSRS
REPRESENTED 3Y THE FIVE COKBL'STQRS TESTED
•
<^
Parameter Range
Stack Height (meters) 10 - 75
Stack Temperature (Centigrade) 139 - 232
-------
TA3LS 3
RANGE OF ANNUAL MAXIMUM AVERAGE GROUND LEVEL CONCENTRATIONS
OF* DIOXIM ISOMSRS
ESTIMATED FOR FIVE US SOURCES SAMPLED TO DATS
USING PTMAX COMPUTER AI3 DISPERSION MODEL3
Pollutant (s) Range (ng/m3)b
-------
Unitea States Press Office £-107)
Environmental Protection Washington DC 20460
Agency
invifonmenta!
R-153
FOR RELEASE: THURSDAY, NOVEMBER 19, 1931
INTERIM SPA EVALUATION FINDS NO
DIOXIN HAZARD AT RESOURCE
RECOVERY FACILITIES
U.S. Environmental Protection Agency Deputy
Administrator John W. Hernandez, Jr. today said that an
interim evaluation of resource recovery facilities at five
locations indicates that tetrachlorinated dioxin emissions
from the combustion of municipal wastes are "far below the
level of a credible health risk."
The interim evaluation was made from data collected on
municipal resource recovery facilities in Arkansas,
Illinois, Iowa, Florida, and Ohio. EPA said there are
about 40 resource recovery combustors in the United States
and that a number of additional units are being planned,
some of them involving very different technologies.
The interim data do not totally represent the industry,
although the data do give some indication of current
conditions, and what might be expected in the future.
"The approach used in EPA's analysis," Dr. Hernandez
said, "is extremely conservative, in that the assumptions
err on the side of public health protection. The
conclusions reached concerning public health risks are
(more)
-------
R-168
-2-
lifcely to be applicable to similar facilities when those
facilities are properly designed, constructed and
operated."
Hernandez cautioned that EPA has not developed anything
*»
that should be interpreted as an emissions standard for
tecrachlorinaced dioxins, nor should the levels measured at
the five facilities be interpreted as an upper boundary in
terms of setting emissions limitations.
"Setting*, such a standard would involve a long and
complex rulemaking process which, given the results of our
interim analysis, is not deemed to be necessary,"
Hernandez said. "The agency intends to periodically
monitor representative resource recovery facilities/"
he added, "and if we find that the emissions are
significantly greater than those evaluated in this
assessment, we will consider the need for regulatory
action."
Concern first arose at the Hempstead Resource Recovery
Corporation facility in Hempstead, N.Y. In 1979 the
operators of the plant permitted EPA to begin sampling
emissions. However, in an unrelated action, the village of
Herapstead, late in 1979, ordered the facility closed
because of odor problems. It has not been reopened. The
Hempstead facility is not included in the interim
evaluation because EPA had not collected
sufficient data before the facility was closed.
(more)
-------
-3-
There are a tocal of 22 different forms (isomers) of
tetrachlorinated dioxins; only the cetrachlorodibenzo-o-dioxin
(2,3,7,3-TCDD) isomer has been subjected to extensive
testing. EPA said there is no scientific evidence that any
*&•
of the isomers are more toxic than 2,3,7,8-TCDD.
Therefore, for the purposes of the interim evaluation, EPA
said it made the conservative assumption that all the
isomers are as toxic as 2,3,7,8-TCDD.
Since there are insufficient data to completely answer
questions relating to TCDD's toxicity and exposure, and
because this information is needed to assess the risk to
people breathing emissions from the stack, SPA said it
conducted its analysis by adopting a series of assumptions
designed to represent the "worst case" possible.
The specific isomer, 2,3,7,8-TCDD has been shown to
have effects on the reproductive systems of various animal
species. Bioassays have demonstrated that 2,3,7,8-TCDD is
an animal carcinogen in rats and mice. Existing
epidemioloyical studies do not demonstrate clear
exposure-related reproductive effects, in humans. "Other
epidemiological studies suggest an association between
exposure to 2,3,7,8-TCDD and certain types of human cancer.
Further studies are underway to address this question. In
its assessment EPA assumes that all of the tetrachlorinated
dioxir.s found in the emissions were carcinogenic.
(For further information on technical aspects of the
evaluation, contact Dr. Don Barnes, senior science advisor,
Office of Pesticides and Toxic Substances,
tel. (202)382-2897.)
R-16 8
------- |