SAB-EC-87-012
UNITEDSTATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
Decenter 19, 1986
OFFICE Of
THE ADMINISTRATOR
Honorable Lee M. Thonas
Administrator
U. S. Environmental Protection
Agency
401 M Street, S. W.
Washington, D. C. 20460
Dear Mr. Thomas:
The Science Advisory Board's (SAB) National Dioxin Study Review
Subcommittee has completed its review of EPA's draft National Dioxin Study
and is pleased to transmit its principal scientific conclusions and recon-
mendations to you. The Subcommittee met in public session on Septernber 8-9
to review the adequacy of the scientific assumptions* methodologies and
conclusions of the Study* It subsequently submitted its draft report to
the SAB Executive Conmittee which it on Decanter 18th.
The Subcommittee conmends the Environmental Protection Agency and
its personnel for the preparation of a comprehensive* informative and
well written document. Many of the sample collection techniques and the
required analytical methodologies were, and still are* state-of-the-art.
With seme revisions that are identified in this report* the thoroughness
of the Study and quality of the data are scientifically supportable,
given our understanding of current knowledge.
The Subcommittee consensus is that the statistical interpretations
and extrapolations are, with seme corrections noted in the attached
report, generally adequate.
There are basically four objectives of the Study. One of the main
objectives was to "the associated risks to humans and the environment*
The other objectives included a study of the extent of contamination,
M^lenentation of site clean-up efforts* and the evaluation of a variety
of disposal and regulatory alternatives* Considering the logistical and
financial constraints, the Study generally met the latter objectives but
failed to properly address the risk assessment aspect. To perform risk
assessment_for one tier and not the others, is inconsistent. EPA should
delete the Tier 4 risk assessment altogether to ensure consistency with the
entire study. Any specific risk assessment developed for a combustion
source or category of sources for any particular EPA decision making
activity should undergo peer review.
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The objective of studying the risks of dioxin contanination to the
non-human environment was not adequately addressed in the report* To
the extent available, results obtained by the EPA (or fran other
scientifically valid studies) on the bi©accumulation by fish of 2,3,7,8-
containing tetra-, penta-, hexa-, and heptachlorodibenzo-£-dioxins relative
to that of other dioxin congeners (that do not contain the 2,3,7,8-
ehlorination pattern) should be included. Results on the fish bioaccumu-
lation of dioxins that are present in sediments and fly ash should also
be added if such data are available. Lastly, to the extent that the EPA
has such results, information ©n the toxicity of dioxins to different
fish species should be included. At the very least, the inclusion of
such a discussion of these ecotoxicological endpoints would demonstrate
that the Agency is cognizant of the need to fully study risks of dioxin
exposure to the environment.
EPA and the Food and Drug Administration (FD&) propose different values
for acceptable TOD concentrations in fish that are consumed by hunans.
Since this issue is crucial to the Great Lakes studies, it is difficult
to understand why the two have "agreed to disagree". The Subcom-
mittee recommends further discussions with the FDA prior to submitting
this study to Congress.
The Study does not clearly state how one characterizes a site with
respect to TCDD contamination (i.e. from a sampling perspective). It
would be useful to include a sentence or two that would address (a) how
many samples are required, (b) whether surface wipe samples or cores are
better, and the problems with each approach, With respect to the second
sampling method, a straightforward calculation could be made to account
for all TCDD being in the upper endr for example, the top 0.5 cm. of a 4
inch core. Hi is calculation would reduce some of the uncertainty as to
what constitutes a contaminated and thus, by inference, a
contaminated site. This comment is directed across several tier efforts
where soil or sediment samples were taken.
In general, EPA's limited conclusions appear to be supported by the
results of the survey. Hie Subcommittee believes that additional
conclusions may be drawn. While it appears that "off-site" migration of
polychlorinated dibenzo-p_-dioxins (PCDDs) and polychlorinated dibenzofurans
(PCDFs) is minimal, there is evidence of widespread accumulation of
these cotipounds at low levels in human tissues.
Given current knowledge, the Agency may have identified most of the
significant sources of PCDD and PCDP contanination and/or exposure.
sources have been treated in more detail than others, but most have
been studied to seme extent. However* the SubcOTmittee believes that new
will probably be discovered in the near future as more knowledge
is gained on the various mBchanisrs of the formation of chlorinated
dioxins and furans. This may result in the recognition of previously
undetected "routes and rates of to humans and the environment.
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Based upon the limited survey of selected combustion sources in Tier
4, it is not possible to accurately quantitate the potential environmental
input of dioxins and furans from this category for the purposes of the
National Dioxin Study. However* for the types of facilities tested,
annual loadings can be roughly estimated. The specific sources sanpled
represent a selection of combustion facilities. Hiile it is not known
how many similar facilities exist in the U. S., approximate estimates
would provide a range for evaluation.
Because of the large number of combustion facilities, and the increasing
reliance on incineration for waste management , Tier 4 sources renain an area
of concern. The ubiquitous presence of low levels of 2,3,7,8-TCDD in
Americans suggests that combustion sources are responsible at least in
part for this general "background" contamination. Investigators in other
countries have reached the same conclusion. The Science Advisory Board is
currently evaluating this and other issues as they pertain to nunicipal
waste combustion.
The Subcarcmittee its appreciation for the opportunity to
review the National Dioxin Study. Attached to this letter are more
specialized technical cements that pertain to certain sections of the
Study- The Subcommittee requests a formal Agency response to the scientific
advice it has provided, or discussion of the reasons for those issues where
the advice is "not accepted. It would particularly appreciate this response
at the time the Agency formally transmits the final study to the Congress.
Sincerely,
Robert
National Dioxin Study Review Subcatwnittee
Science Advisory Board
Norton Nelson, Chairman
Executive Committee
Science Advisory Board
Enclosure
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I. General Scientific Conrrgnts on the National Dioxin Study;
For each of the seven tiers (representing different sources and
routes of potential contamination and exposure) EPA developed a sampling
plan that involved two basic stages; (1) selection of sites, and (2)
selection of material at the selected sites. The principal statistical
issues concern these latter two issues? and the analysis and interpretation
of the resulting measuranents.
In the first stage, selection varied fron complete coverage (Tiers 1,
la, 2, 2a) through random selection from a list (Tier 7), judgment based
selection of Tiers 4 and 5, and combinations of randan and judgment
selection (Tiers 3 and 6). The within site sampling plans involved
primarily judgment, sometimes supplemented with randan sanples. The
sampling plans used in the various tiers appear to represent well chosen
ccnpronises between what was convenient (but of limited scientific value
because of uncertainty about how the sample compares to the whole) and
what was ideal (but not always feasible because of the time and resources
required). The findings have, by and large, been allowed to speak for
themselves in the report via detailed site-by-site descriptions, with a
minimum of formal statistical analysis. The Subcommittee believes this
is a scientifically appropriate approach.
Because of the great differences between the various tiers, in terms
of both prior knowledge and the sampling plans used in the National Dioxin
Study, the degree of uncertainty that remains varies somewhat from tier
to tier.
The main text of the report emits much detail and background infor-
mation, which is acceptable because it enhances the readability of the
document. References to the detailed material, however, would be helpful.
For example, the discussion of the important question of "What happened to
dioxin in the environment?" is found in Appendix B of NDS 3567. A reference
to this material in Section 1.3 of the main text would improve the document.
A number of homologues of the PCDDs and PCDFs are present in parts per
trillion (ngAQ) concentrations in the tissue of the general
population of the United States and other countries, Octachlorodibenzodioxin
and octachlorodibenzofuran may reach conentrations in the low parts per
billion (ugAg) range. It that those homologues of the PCDDs and
PCDFs where the 2,3,7,8 positions are occupied by chlorines are preferentially
stored in hunans (Grahwi et al., 1985; and Hobson, 1985; Nygren et
al., 1985; Patterson et al.f in press; et al., 1984; Ryan et al.,
1985,- Ryan and Schecter, 1985; Schecter et al., 1985).
In a series of 59 control adipose tissue sanples from the general
population, 2,3,7,8 tetrachlorodibenzodioxin could be identified in all
samples. .The mean concentrations were 6»4 parts per trillion (ugAg) ^nd
the range 1.4-20.2 parts per trillion, ugAg (Patterson et al., in press).
Other investigators have reported similar means and ranges. Thus, like
fish, many human adipose tissue samples seem to contain trace amounts of
these chemicals (Ryan et al., 1984). These data indicate that widespread
low-level contamination has occurred.
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Combustion sources produce solids, either as bottom ash or fly ash
(much of the latter is collected in the stack by control devices such as
bag houses or electrostatic precipitators). Ash may also contain concen-
trations of dioxins and furans. Therefore, envirorroental inputs of
dioxins and furans fron ash represent another potentially significant
source of these substances fron ccmbustion facilities.
II. Specific Editorial/Technical Coments on the National Dioxin Study
Tier I
1-2,1.1. The first paragraph states that over 500 treated cases of
toxic effects were alleged to be associated with the Seveso accident.
This statement should be deleted and replaced by one that places into
perspective not only data on acute dermititis which had resulted frcm
burns received by the simultaneous release of caustic materials, but also
the significance and quality of data on ismunotoxicity, neurotoxicity and
reproductive effects.
1-8,1.2.2. The Study states that the EPA Carcinogen Assessment Group
(CAG) has determined that 2,3,7,8 TCDD is a probable human carcinogen.
The Study should contain an explanation of the criteria used by the CAG
to determine whether a chanical is a probable human carcinogen and whether
these criteria are still the same as they were when the document was
written, and whether any more recent evidence further supports or challenges
this conclusion.
1-8,1.3.2a. EPA should expand the section on nonhuian toxicity. It
fails to mention that sane CDD and CDF congeners differ in their ability
to produce certain endpoints of toxicity. There are presently insufficient
data to detemine whether the toxic effects of various congeners are
additive, synergistic or antagonistic. Therefore, the sentence, "In
addition, more limited data suggests that effects are additive and not
synergistic81 should be deleted or substantiated with references.
1-8,1.3.2b. The Study should state that incidence of mild chloracne
has been observed in humans in Nitro, Ifest Virginia for at least a decade
after exposure to 2,3,7,8-TCDD.
I-1T,1.3.3. The Study assunes that only when knowing the concentration
of hortologous groups is it appropriate to assume equal probability of the
occurrence of each of the congeners in the group. This asswnption is not
supported by data on pyrolysis products.
1-15,1.42. Clarification of the stated detection limits is required.
Due to the uncertainity associated with the term, the analytical method
quantitation limit, may be appropriate in this report. Mien defining the
quantitation limit, the operational constraints (i.e., ten times the
signal to'noise ratio) should be stated.
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Hie Study should present more detail of the quality assurance/quality
control program throughout the test. The reader should be able to readily
determine the level of accuracy and precision.
Tier_2
11-9,2.2.3. Has sampling conducted in the spring of 1986?
11-21,2.3. If "little11 means than 1 part per billion (ppb),
it should be stated.
' 11-22, para.2., line 2 and figure 2.3. Under "No further action", the
number of sites in the text and the figure do not agree (22 sites text versus
23 sites figure).
11-29 and 30, Table 2.2. Millmaster Onyx and Baird and McGuide.
The kinds of sanples analyzed are omitted.
Table 2-3. The Centers for Control (CDC) has two types of
to health questions in contaminated areas: health advisories
health assessments. Not all items listed in table 2-3 are health
advisories. The heading of the tables should be changed to "Dioxin sites
reviewed by ATSDR/CDC." "Advisory" should be changed to "Reconraendation."
Tier I_II
111-3,3.1.1. The Study should more specifically state the criteria
to determine if a site was contaninated. If one soil sanple had
than 1 ppbf or one fish sanple had less than 1 ppt of 2,3,7,8-TCDD,
the entire site considered uncontarainated?
111-3,3.1.2. In the discussion of Tier 3 no mention is made of the
"...additional 325 potential Tier 3 facilities..." described on page 10
of the final draft report "The National Dioxin Study Tiers 3,5,6,7" (NDS
3567). The existence of these 325 additional potential Tier 3 facilites
means that Tier 3 might be twice as large as is indicated in NDS-OTC.
The present state of knowledge about 325 facilities should be
clarified to enable the reader of NDB-FTC to have an accurate appreciation
of the uncertainty concerning the potential contribution of sources in
Tier 3.
III-4, 3.1.3, The numbers given on page III-4 are not consistent.
In the first paragraph of section 3,1.3 results, the Study states that
"Soil contamination...was found at four of the statistically selected
sites." However, in the third paragraph, the Study of "the five
statistically selected contaminated sites." (NDC-3567, page 13, suggests
that 5 of 41 sites were contaminated,) Similarly, paragraph 2 says
that 5 of the regionally selected sites were oontOTinated, yet paragraph
3 of- "..sfour of the six contaminated regionally selected sites...".
111-5,3.1.3. The statement that "it is estimated that 8+6 percent
of facilities in the FATES data base may be contaminated," needs
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clarification. Use percentages apparently refer to the population of 312
sites fron which the statistical smple was drawn. Thus, they translate
to 25 _+ 19, or between 6 and 44 contaminated sites. Hie previous comment
(111-3,3.1.2) becones important here? if similar percentages apply to the
325 "additional potential Tier 3 facilities," then the number of contaminated
sites is roughly twice as large. If there is reason for confidence that
similar percentages do not apply because of specific relevant differences
between the 312 sites and the 325 "potential" sites, this should be made
clear. Otherwise, the possibility that the "8 + 6 percent" applies to
more than 600 sites (not only to the 312) should be acknowledged.
The assunption that the seven missing eligible sanple sites are not
contaminated should be justified somewhere* The parenthetic explanation,
"(based on their physical characteristics)", is insufficient. Can EPA provide
a reference to where a fuller analysis and explanation justifying the
assunption can be found? If not, the cautious reader may vie 11 decide
that the higher figures given in Table C-2 of NDS-3567 (p. C-4), i.e. 10
+_ B percent (31 _* 25 contaminated sites), more reasonable? and the
skeptic might even the other extrane assntptlon of all seven missing
sites contaminated, leading to 20 + 10 percent, or 31 to 93 sites contam-
inated. It might be best to estimate the total number of sites like the
seven missing ones (where there has been extensive grading and/or paving)
and frankly acknowledge that only educated guesses can be made about the
amount of contamination at such sites. The population of 312 would be
reduced by this amount, and new estimates of the percent contaminated
would be required.
One additional point is that the estimation is not the ruraber of
sites that are contaniinated, but the number that would be joundjbo
be jxantaminated if they were all sampled using the procedures and
techniques of this Study. For every site at which contamination is
present there is some probability that EPA's investigation procedures
would lead to a false negative finding because of variability involved In
choosing where to take samples as well as because of processing and
analytical errors. We that this probability is low for heavily
contaminated sites, but not necessarily low for marginal ones. On the
other hand, the probability of false positives would appear to be much
lower and might well be negligible.
111-18,3.1.5 The second conclusion not sean to agree with page
I1-7, where it is stated that 13 sites fron Tiers 3-7 have been referred.
The statement given in section 3.1.5 is not at all clear? does it wply
that al^ remaining Tier 3 facilities have referred?
Tier_jl
-€»
In better to assess the risk of conbustion related airborne TCDD to
humans, ore" needs to know how much TCDD is emitted into the atmosphere
at a representative^number of sources. Experience from sampling trace
metal emissions from sources such as coal fired steam plants, incinerators,
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and smelters has taught the scientific camuinity that, while annual
loadings can be roughly estimated for the types of facilities tested,
each source exhibits a wide range of temporal variability and each type
of source can be very much different in the chemical characteristics of
its emissions. of the shorter term variability may be "smoothed"
by using a longer period of smpling., However, the Subcomnittee believes
that the 13 ccmbustion sources do not adequately represent the rest of
available TCDD air anission sources in the U. S. The muribers do notff for
example, permit a calculation ©f the annual U. S. TCDD emissions into the
atmosphere from stationary combustion sources. A second in calculating
human health risks involved modeling the atmospheric dispersion of the
emitted TCDD using some unspecified nodel* This kind of exercise has
been quite comon for SO2 and 804. What these msdeling efforts have
taught is that, with appropriate meteorological data, it is possible
to do a reasonably good job of estimating the yearly average air
concentration, but daily, weekly, or even monthly predictions (especially
^plurae touchdowns") are not satisfactory* Hence, it would be very doubtful
that the ""average* calculated TCDD air concentration accurately reflect
to humans,
Ccmbustion sources produce solids, either as bottom or fly ash
(rajch of the latter is collected in the stack by control devices such as
bag houses or electrostatic precipitators). Ash may also contain
concentrations of dioxins and furans- Therefore, environmental inputs of
dioxins and furans from ash represent another potentially significant
source of these substances from ccmbustion facilities.
Because of the large number of conbustion facilities, and increasing
reliance on incineration for waste management, Tier 4 sources remain of
concern. The ubiquitous presence of low levels of 2f3r7r8-TCDD in
Americans suggests that ccmbustion sources are responsible at least in
part for this general "background" contanination. This has been the
conclusion of investigators in other countries as well.
It is not clear whether the risk calculations frcm stack emissions
are based on CDDs and CDFs in the gas only, or whether they also
Include particulates. If they are on particulates, the hunan dose
would depend on particle size, and only a small portion of these
materials would actually be inhaled.
Sampling results and physleo-chanleal data Indicate that TCDD In air
should be mainly associated with micron-to-submlcron aerosols* Yet the
air dispersion of ccmbustion related TCDDs was modeled as a vapor.
Atmospheric removal efficiencies of vapors and particles may differ
considerably, rendering results from the model calculations In the document
suspect.
Hhile it is ^asonable to expect that most of the emitted TCDD is
associated with 1-2 micron or submieron si^ed particles* it is not clear
at all how available this compound is to transfer into the himan lung.
These weaknesses in arriving at estimates increase the scientific
difficulty of perfoming risk assessment. To develop a risk assessment for
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this tier and not the other tiers creates an inconsistency for the entire
Study. H»A should* therefore; delete the Tier 4 risk assessment entirely.
Any specific risk assessment developed for a conbustion source or category of
sources for any particular EPA decision making activity should undergo peer
review.
TierJS
111-19,3.2.2. A major source of uncertainty in Tier 5 concerns the
size of the tier. However, this becomes a matter of practical importance
only if the levels of contamination in Tier 5 are great enough to be of
concern.
The soil sanples were comprised of a four inch plug of material. If
the corpounds of interest were in only the first centimeter or less, EPA
could have greatly underestimated the reported concentrations in the
fraction roost biologically available to humans (hand-to-mouth, reintrainment
of dust). EPA data which shows dioxins to be relatively trarobile in soils
suggest that this may be the case. In the absence of nore specific
information, the Agency should develop calculators that assume only 1 to
10 millimeters contaminationf and it should examine the findings and
conclusions relative to the results.
HI-28,3.2.4. The fifth finding nay be misleading the text
inplies only 4 contaminated sites. Also 111-20, 3,2.3 that 15
sites were contaninated, not 13.
111-35, Table 3.2. Sans A. R. Desna Data are missing. To the table
should be addeds Soil, 465 samples, 1 positive, 3 ppt 2,3,7,8-TCDD.
Tier 6
111-30, 3.3.2. EPA did not consider one chemical product, the
production of chlorophenol fron chlorobenzene, although there is a chemical
site in Niagara Falls, New York where a significant of contamination
with dioxins, including 2,3,7,8-TCDD, is asociated with this product*
111-41, 3.3.4. Findings and conclusions should be examined relative
to the Subconnittee's coments presented above.
Tier 7
^Background sites" in the Tier 7 effort is probably not a
designation. The word "background" has a different implication than what
the authors tried to accomplish with their site selection strategy.
The TOD on fish is difficult to interpret in terras of what
extrapolations can be made to other fish. Data are now available
on other 'chlorinated hydrocarbons in fish, especially with respect to
different age, weight, sex, time of year, and species. Concentration
distribution functions could be constructed fron these data and used in
conjunction with the TCDD data for a more meaningful interpretation.
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A perusal of the physico-chemical data in the main document as well
as in the tier background documents indicates that sane of these values
could be updated. Recent iteasurements on the aqueous TCDD solubility and
vapor pressure at 25°C arei Cg = 6 x 10"11 noless/L - 1.93 x 1CT5 jng/L =
19.3 ng/L (ppt); jr3 - 7.4 x ID"10 torr = 9.47 x 1CT13 atn. This leads to
a Henry's Law constant, H = 1.6 x 10"-* atro-nAnoles"!, which is 8-10 times
different than the one reported in these documents.
111-43, 3.4*2. Fish. Itore detailed Infonnation on the sanpling
protocol should be provided to clarify that 4 fish samples per site
were analyzed and, if the first one (a whole, bottom feeding fish) was
negative, the other 3 samples were not analyzed. (See the National
Dioxin Study, Tiers 3,5,6, and 1, April, 1986, Page 41, para. 3.)
Additionally, EPA should specify the criteria for a positive sample for
TCDD eontatti nation (greater than 1 ppt?}.
111-45, 3.4.3. para. 2. The Study should state whether the maximum
concentrations presented were for whole fish or filets,
111-45, para. 3. it demonstrated statistically that fish sampled
fron the Great Lakes were larger than those sampled from inland waters?
II1-46, para. 2. The statement on page II1-46 appears to take
exception to the acceptable level of 25 ppt TCDD in fish (under certain
restrictions) by the FDA. Hi is page indicates that consumption of
fish containing 25 ppt TCDD may pose an upper bound human cancer risk of
25 X 10~4, a high risk according to current regulatory practice. If
the Agency maintains its position that consuming fish containing 1 ppt of
fish may pose an unacceptable risk (1 x 10"^) the implications to freshvrater
comercial and sport fishery may be far reaching.
I1-48, 3.4.5. Hie Study acknowledges that the fish data may be a
cause for human health concern, but it ignores the potential significance
of data in estimating the prevalence of 2,3r7r8-TCDD in the environ-
ment. The fish tissue data may actually represent a better indicator of
the prevalence of,2,3,7,8-TCDD than the soil samples, particularly since
the top five inches of soil were collected and blended. The various
bodies of water from which fish were sampled in this Study may serve as
integrators of the inputs into their respective watersheds and the fish,
in turn, serve to integrate the bioavailable 2,3,7,8-TCDD which has
accumulated over time in water and sediments. The final report to Congress
should discuss the relevance of the fish data in estimating the distribution
of 2,3,7,8-TCDD and the apparent inconsistencies between these data and
the soil data.
111-53, Figure 3.6. EPA should dhange the title of this figure to
"Distribution of 2,3,7,8-TCDD Concentrations in Hhole Fish Samples Fran
Different Locations8*.
I11-59 to II1-71, Tables 3-6 and 3-7. Results for Great Lakes fish
are not included in any of the tables, whereas fish from statistically
selected and regionally selected sites are included. This emission should
be corrected. Msof if possible, the type of fish sampled at
each site should be added to the tables.
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ltoxic_JEguiyalengy Factors
The Science Advisory Board formed a Dioxin Toxic Equivalency Factor
Subcommittee to conduct a review of the assumptions and principles used
by EPA in developing interim toxic equivalency factors for mixtures of
CDDs and CDFs. Drs. Huggett, Kimbrough, Neal and Silbergeld participated
in that review which occurred on September 8-9, 1986. The National
Dioxin Study Subcommittee did not, therefore, conduct a separate scientific
review of iPA's toxic equivalency factor methodology.
The Subccraruttee recognizes that agencies need to regulate human
exposures to mixtures of chlorinated dioxins and furans, some ocmponents
of which have not been examined for chronic toxicity. The Subcommittee
reconmends that the Agency use toxicity equivalence factors as an interim
risk management tool, clearly stating in the document that the procedure
contains a number of limitations.
Research
VI-6,6.4. The Study states that studies are being proposed to
enable predictions of dioxin uptake into plants and thereafter into the
food chain» Most scientists recognize that plants do not take up these
types of compounds, with the possible exception of root vegetables.
VI-8, 6.5. EPA should identify a ramber of other studies that were
funded using Superfund resources. These includes
1. Missouri Dioxin Study
Chemical wastes, including dioxin orginating fron the NEPACCD/
Syntex plant in Verona, Missouri, contaminated some 36 sites in Missouri.
Present and former residents at one site (the Quail Run Mobile Hone Park,
as well as a group of unexposed persons for conparison) were given a
conprehensive examination to provide information on possible health
effects from environmental exposure to dioxin* Results have been published
in the Journal of the Anerican Medical Association (JAMA) in 1986.
2. In a subgroup of this study, a medical follow-up examination was
completed for study participants who were found to have evidence of
imnunologie abnormalities and who elected to participate in the follow-up
examinations. Analysis of the test results is in progress.
3. Missouri Dioxin Adipose Tissue Study
The purpose of this study is to measure adipose and serum levels
of dioxin (TCDD5 in populations potentially to dioxin., Study
authors think that body burden measurements of TOT) will provide inportant
information concerning the toxicology and epidemiology of chronic environ-
mental exposure to TCDD. The study will examine TCDD levels in adipose
tissue and serum from individuals exposed to dioxin. Preliminary results
were presented at Dioxin '86 in Fukuoka, Japan and have been published in
Patterson et al., JAMA, 256: 2683-2686, 1986.
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4. Reproductive Outcome Study at Missouri Dioxin Sites
This study Is designed to provide information concerning possible
adverse reproductive outcomes related to long-term environmental exposure
in 9 residential areas in Missouri where waste oil mixed with dioxin
was sprayed on roads for dust control beginning in May 1971. In phase I,
the rates of adverse reproductive outcomes for the approximately 400
births frctn 1971 to 1982 to women to dioxin will be ccnpared to
rates for an and race-matched control group. In Phase II, the medical
records of all obstetrical and pediatric hospitals in the state will be
surveyed to determine the background rate of malformations for Missouri.
As of June 25* 1986 the authors have completed all data collection
for I and II. Analysis of the data collected during Phases I and
IIf in terras of exposure to TCDD, has begun. The authors have prepared a
first draft of the Phase I report and submitted it to Centers for Disease
Control staff for review. Preliminary analysis of the Phase I data has
not demonstrated statistically significant rates of abnormalities among
births in women to dioxin. Plans for a Phase III Quality Control
smple have been completed; medical records for 50 infants in 15 hospitals
will be selected at random for a complete medical records review as
quality control for Phase I and II data.
5. NIQSH/CDC Mortality Study of Workers Exposed to Dioxin
The purpose of this study is to determine the mortality outcome
of U. S. production workers exposed to dioxin contaminated chenicals.
This includes approximately 6*000 workers from 14 facilities throughout
the U. S. Investigators are testing 4 specific null hypotheses that
there is no association of exposure to dioxin contaminated products and
death due to soft tissue sarcoma, lynphoma, stomach cancer and liver
cancer.
Through January-March, 1986, a submission was made for vital status
follow-up to the National Death Index (NDI) and to the Health Care Financing
Administration (HFCA). The review of medical records for information on
chloracne has been completed for all 14 plants. Investigators have also
received large amounts of data concerning analyses of dioxin from one to
two sources that %*ere slow in responding. One major source of analytic
data has not yet produced the information, though it is expected to be
received during the third quarter of 1986.
6. Pilot Study
Hie CDC's Center for Environmental Health has conducted a pilot
health study in residents who predominantly carae from Tines Beach* Missouri.
(Arch. Environ, Health 41:16-22, 1986).
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References
Graham, M., Hileman, F., Kirk, D., l
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