Protection ' EPA-600/6-81-003
Agency September 12, 1980
&EPA Research and
Development
RISK ASSESSMENT ON
(2,4,5-TRICHLOROPHENOXY) ACETIC ACID (2,4,5-T)
(2,4,5-TRICHLOROPHENOXY) PROPIONIC ACID
2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD)
Prepared for
Office of the General Counsel
U.S. Environmental Protection Agency
Prepared by
Office of Health and
Environmental Assessment
Washington DC 20460
Carcinogen Assessment Group
U.S. Environmental Protection Agency
Region 5, Library (5PL-16)
230 S. Dearborn St eet, Room 1670
Chicago, IL 60604
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TECHNICAL REPORT DATA
(Please read Instructions on tlie reverse before completing/
1. REPORT NO.
EPA-600/6-81- 003
3 RECIPIENT'S ACCESSION NO
4. TITLE AND SUBTITLE
5 REPORT DATE
Risk Assessment on (2,4,5-Trichlorophenoxy) Acetic Acid
(2,4,5-T)-, (2,4,5-Trichloroohenoxv^ Prom'nnir Ar-M
(Silvex). 2.3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD)
September 12, 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOFUS)
Carcinogen Assessment Group
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Carcinogen Assessment Group
Office of Health and Environmental Assessment
Environmental Protection Agency
Washington, D.C. 20460
10. PROGRAM ELEMENT NO
11. CONTRACT/GRANT NO
In-house
12. SPONSORING AGENCY NAME AND ADDRESS
Office of the General Counsel
Environmental Protection Agency
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Response/Assessment
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Carcinogenic responses have been induced in mice and rats at low doses of
TCDD. TCDD has been shown to be a cancer promoter. These results, together
with the strongly suggestive evidence in epidemiology studies, constitute
substantial evidence that TCDD is likely to be a human carcinogen. It
appears that TCDD is a more potent carcinogen than aflatoxin BI which is one
of the most potent carcinogens known. The levels of TCDD (contained as an
unavoidable contaminant of the 2,4,5-T) used in the 2,4,5-T studies
apparently were too small to produce an observable response in those
experiments. The lack of a statistically significant tumor incidence in most
of the studies on the 2,4,5-T product may be attributed to the very low
levels of TCDD in the product relative to the levels at which it produced
carcinogenic effects in rats and mice, as well as to deficiencies of those
studies. However, since TCDD is a carcinogen, any product containing TCDD,
including 2,4,5-T and silvex, can be considered to pose a human carcinogenic
hazard. Furthermore, a rat study on specially purified 2,4,5-T provides
highly suggestive evidence that essentially pure 2,4,5-T may be a human
carcinogen. Quantitative assessments have been calculated for the
carcinogenic risk posed to humans.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI F)old:Group
8. DISTRIBUTION STATEMENT
NTIS - Release to Public
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
276
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
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THE CARCINOGEN ASSESSMENT GROUP'S
RISK ASSESSMENT ON
(2,4,5-TRICHLOROPHENOXY)ACETrC-ACID (2,4,5-T)
(2,4,5-TRICHLOROPHENOXY)PROPIONIC ACID (SILVEX)
2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD)
September 12, 1980
PARTICIPANTS
Elizabeth L. Anderson, Ph.D.
Larry D. Anderson, Ph.D.
Steven Bayard, Ph.D.
David Bay!iss, M.S.
John R. Fowle III, Ph.D.
Bernard H. Haberman, D.V.M., M.S.
Charalingayya B. Hiremath, Ph.D.
Chang S. Lao, Ph.D.
Robert McGaughy, Ph.D.
Charles Poole, M.P.H.
Dharm V. Singh, D.V.M., Ph.D.
Todd W. Thorslund, Sc.D.
Peter Voytek, Ph.D.
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CONTENTS
SUMMARY AND CONCLUSIONS
Qualitative Risk Assessment ....... . .............. "1
Quantitative Risk Assessment of 2,4,5-T, silvex, TCDD ......... 6
QUALITATIVE RISK ASSESSMENT
I. Introduction ............... ............... 8
II. Metabolism .............................. 10
Metabolism of (2,4,5-Trich1orophenoxy)Acetic Acid
(2,4,5-T) ........................... 10
Metabolism and Storage of
2,3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD) ........... 11
Aryl Hydrocarbon Hydroxylase (AHH)
Induction Studies With TCDD .................. 13
Covalent Binding of TCDD with Macromolecules ............ 15
III. Mutagenicity ............................. 17
Mutagenicity of 2,4,5-T ...................... 17
Mutagenicity of TCDD ........................ 21
Conclusion ............................. 23
IV. Toxicity ................................ 24
Animal Toxicity ........................... 24
Toxicity of 2,4,5-T ...................... 24
Toxicity of TCDD ........................ 25
Toxicity of 2,4,5-T, 2,4,5-Trichlorophenol ,
and TCDD in Humans ....................... 27
V. Carcinogenic! ty ............................ 29
Carcinogenicity of 2,4,5-T in Mice ................. 29
Muranyi-Kovacs et al . (Oral) Mouse Study ............ 29
Muranyi-Kovacs et al . (Subcutaneous) Mouse Study ........ 31
Innes et al . (Bionetics Laboratories) (Oral) Mouse Study .... 33
Innes et al . (Bionetics Laboratories)
(Subcutaneous) Mouse Study ................. 35
Carcinogenicity of 2,4,5-T in Rats ................ 36
Kociba et al . (Oral) Rat Study ................. 36
Leuschner et al . (Oral) Rat Study ........ > ...... 44
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REFERENCES 137
APPENDICES 145
A. Dose-related Mortality Estimates in Kociba's TCDD Rat Study (Tables).
B. Pathologic Evaluations of Selected Tissues from the Dow Chemical
TCDD and 2,4,5-T Rat Studies by Robert A. Squire, Associates, Inc
(Summary Tables)
C. Leuschner Histopathologic Testicular Tumors in Rat (Historical
Control Data) .
D. Leuschner Histopathologic Report on Tongue in 2,4,5-T Rat Study . . .
E. Memo from Wade Richardson Concerning the Telephone Conversation
with Leuschner
F. Memorandom and report from Dr. David Severn, Hazard Evaluation
Division, Office of Pesticide Program Exposure. Assessment of
2,4,5-T, Silvex and TCDD
G. Methods for Determining the Unit Risk Estimates for Air Pollutants. .
111
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SUMMARY AND CONCLUSIONS
QUALITATIVE RISK ASSESSMENT
(2,4,5-Trich1orophenoxy)Acetic Acid (2,4,5-T)
(2,4,5-Trichlorophenoxy)acetic acid, widely known as 2,4,5-T is used as a
vegetation growth regulator and herbicide. "Agent Orange," a defoliant used
extensively by the U.S. Army in Vietnam, is a mixture of equal amounts of
2,4,5-T and (2,4-dichlorophenoxy)acetic acid. In 1970, amid growing concern
about the teratogenic effects of 2,4,5-T, the EPA cancelled the registration of
the compound for uses "around the home, recreation areas, and similar sites" and
"in crops intended for human consumption." Before some uses were suspended in
1979, it was used primarily to clear vegetation along powerlines, highways,
pipelines, and railroad rights-of-way, and on range, pasture, and forestlands.
The commercial preparation of 2,4,5-T contains 2,3,7,8-tetrachlorodibenzo
-p-dioxin (TCDD) as an unavoidable impurity present at a concentration of
approximately 0.05 ppm. TCDD is considered extremely toxic.
.2,4,5-T is readily absorbed by several mammalian species, including man, and
is excreted unchanged - mostly in urine.
The available information about the mutagenic activity of 2,4,5-T is
considered to be limited. 2,4,5-T is indicated to be a weak mutagen in
Drosophila and, under acidic conditions, showed mutagenic effects in
Saccharomyces cerevisiae.
Tests for the chronic carcinogenicity of 2,4,5-T were performed by several
investigators. Two studies were carried out with Sprague-Dawley rats, one by
the Dow Chemical Company (Kociba et al. 1979) and one by F. Leuschner (1979),
Laboratorium fur Pharmakologie und Toxikologie, Hamburg, Germany. The Dow study
showed an increased incidence of carcinoma of the tongue in male rats dosed with
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et al. (1969) (Bionetics Laboratories 1968) conducted two studies using mice,
one oral and the other subcutaneous. These studies were found to be inadequate
to assess the carcinogenicity of si 1 vex.
Dow Chemical Company performed two feeding studies, a 2-year feeding study
on rats and a two year feeding study on dogs which were summarized by Mullison
(1966) and Gehring and Betso (1978). These have been found to be inadequate to
rule out the carcinogenicity of silvex.
2,3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD)
Probably one of the most toxic chemicals known to man is
2,3,7,8-tetrachlorodibenzo-p-dioxin. The major source of its environmental
contamination is from the pesticidal uses of 2,4,5-T, 2,4,5-trichlorophenol, and
silvex.
In small amounts, TCDD is a potent inducer of arylhydrocarbon hydroxylase in
mammals. This is a complex enzyme system that consists of epoxidase,
epoxidehydratase, and glutathione transferase. The enzyme epoxidase is known to
mediate the formation of epoxides, which are potentially active carcinogenic
metabolites. TCDD can be metabolized in mammalian species via the epoxide to
dihydodiol and further conjugates with glutathione. Persistent residues of
TCDD were found in liver and fat in a 2-year feeding study in rats. Significant
covalent binding of TCDD to protein has been demonstrated by two investigators.
Covalent binding of TCDD with DNA is less significant in liver cells.
Currently available studies on the mutagenicity of TCDD are inconclusive.
Two bacterial systems, Escherichia coli and Salmonella typhimurium (without
metabolic activation), exhibited positive mutagenic activity. However, in
another study of Salmonella typhimurium (with and without metabolic activation),
the results were negative. '
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In a companion mouse study by the National Cancer Institute (1980a), male
and female B6C3F1 mice were given TCDD by gavage at dose levels of 0.01, 0.05,
and 0.5 ug/kg/week for males and 0.04, 0.2, and 2.0 ug/kg/week for females.
TCDD induced statistically significant increased incidences of hepatocellular
carcinomas in the high dose males and females, and thyroid tumors, subcutaneous
fibrosarcomas, and histiocytic lymphomas in females.
In a study by Pi tot et al. (1980), TCDD has been shown to be a potent liver
cancer promoter. In a study by Kouri et al. (1978), TCDD has been shown to be a
cocarci nogen.
Epidemiologic Studies
Several epidemiologic studies have been conducted which are relevant to the
assessment of the carcinogenicity of 2,4,5-T, silvex, and TCDD. Two Swedish
epidemiological case-control studies (Hardell and Sandstrom 1979, Erikson et al.
1979) reported a very strong association between soft tissue sarcomas and
occupational exposure to phenoxyacetic acid herbicides and/or chlorophenols.
These studies indicated approximately five to sevenfold increases in the risk of
developing soft tissue sarcomas among people exposed to phenoxyacetic acids only
in comparison to people not exposed to these chemicals. Another Swedish
case-control study (Hardell et al. 1980) provides suggestive evidence of an
increased risk of developing lymphomas resulting from occupational exposure to
phenoxyacetic acids.
Two cohort studies, one by Axel son et al. (1980) and the other by Thiess and
Frentzel-Beyme (1977) provide suggestive evidence that phenoxyacetic acids
and/or TCDD increases the risk of stomach cancer in humans.
Four other cohort studies by Ott et al. (1980), Riihimaki et al. (1978),
Zack and Suskind (1980), and Cook et al. (1980) did not indicate fcn increased
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The assessment of risk from TCDD exposure covers only the herbicide
applicators and dietary exposure to beef, milk, deer, and elk. For unprotected
workers, the upper limits of lifetime risk of induced cancers are in many cases
as high as or in the 10" 3 range. For the general population exposed to beef
contaminated with TCDD, the upper limit of risk for the estimated exposure is
2.4 x 10~6. For local populations consuming only beef which is contaminated
with TCDD, the risk is much greater, as high as 1.9 x 10~4 for the estimated
exposure. For local populations consuming only milk and other dairy products
which are contaminated with TCDD, the risk is 4.7 x 1C1-4. For deer and elk
meat contaminated with TCDD, risks to the local population are no greater than
Id'4 for 12 meals a year.
The upper limit of dietary risk associated with estimated exposures to
2,4,5-T in contaminated rice and milk were in the 10~7 range for a high
consumer eating only contaminated rice or an average consumer drinking only
contaminated milk.
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The structure of the four compounds is shown in Figure 2 below.
Cl
2,4,5-trichlorophenol
(2,4,5-TCP)
0 - CH2 - COOH
-Cl
Cl-
Cl
(2,4,5-trichlorophenoxy)acetic acid
(2,4,5-T)
CT
2,3,7,8-tetrachlorodibenzo-p-dioxin
(TCDD)
0 - CH2 - CH2 - COOH
rCl
(2,4,5-trichlorophenoxy)propionic acid
(silvex)
Figure 2. Structure of TCDD and TCDD-containing compounds.
2,4,5-T is used as a growth regulator and herbicide. The herbicide "Agent
Orange," used extensively by the U.S. Army as a defoliant in Vietnam, is a
mixture of equal amounts of 2,4,5-T and (2,4-dichlorophenoxy)acetic acid. In
1970, amid growing concern about the teratogenic effects of 2,4,5-T, the EPA
cancelled registration of the compound for uses "around the home, recreation
areas, and similar sites" and "on crops intended for human consumption." Until
EPA suspended certain uses in 1979, it was used primarily to clear vegetation
along power!ines, highways, pipelines, and railroad rights-of-way, and on range,
pasture, and forest!ands.
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2,4,5-T is more tc ic to dogs than to rats.
Five male human volunteers ingested a single 5 mg/kg dose of 99% pure
2,4,5-T containing 0.05 ppm TCDD (Gehring et al. 1973). The plasma concentration
of 2,4,5-T increased rapidly and peaked at 57 ug/ml following 7 hours of
administration. The subsequent clearance rates from the plasma and body were of
first order, situated numerically between the Pates for dogs and for rats. The
2,4,5-T was actively secreted in the urine. It was concluded that 2,4,5-T is
eliminated fairly unchanged from the human body. The volume distribution in
humans was smaller than for test animals. In humans, 65% of the compound
remaining after 24 hours was present in plasma, and 99% of this was reversibly
bound to protein.
In conclusion, 2,4,5-T is readily absorbed by several mammalian species
including man, and excreted mostly in the urine.
METABOLISM AND STORAGE OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD)
In a 1976 study by Rose et al., Sprague-Dawley rats were given either a
single oral dose of 1.0 ug 14C-TCDD/kg (98% pure with 2%
trichlorodibenzo-p-dioxin) or repeated oral doses of 0.01, 0.1, or 1.0 ug
!4C-TCDD/kg/day, 5 days per week, for 7 weeks.
The authors monitored the fate of 14C-TCDD in rats after single oral
administration and found that, on the average, 83% of the dose was absorbed.
Twenty-two days after the single oral dose, concentrations of ^C-activity
were retained mainly in the liver (1.26% of dose) and fat (1.25% of dose). The
half-life of ^C following a single oral dose was 31 _+ 6 days, which followed
first order kinetics. Most of the ^C-activity was detected in feces and not
in urine or expired air, which indicates that TCDD and/or its metabolites are
eliminated via the bile.
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TABLE 1. CONCENTRATIONS OF TCDD IN RAT LIVER AND FAT
AFTER 2 YEARS OF FEEDING
Dose
0.001 ug/kg
0.01 ug/kg
0.1 ug/kg
Concentration
in liver^
540
5,100
24,000
Concentrations
in fata
540
1,700
8,100
aparts per trillion
ARYL HYDROCARBON HYDROXYLASE (AHH) INDUCTION STUDIES WITH TCDD
TCDD causes toxic effects, which are discussed in Section V of this
document. The biochemical lesions underlying the observed toxicologic effects
of TCDD are not known, but certain enzyme systems have been shown to change when
animals are exposed to non-lethal doses of TCDD (Hook 1975). In particular,
hepatic microsomal mixed-function oxidases seem to be highly responsive to TCDD.
AHH is one of the microsomal mixed-function oxidase enzyme systems
responsible for the oxidative metabolism of many exogenous and endogenous
compounds, including many polycyclic aromatic hydrocarbons (Poland and Glover
1973, Kouri 1976). The metabolic oxidation of these compounds proceeds via
transient chemically reactive intermediates, including epoxides (Kouri 1976).
The AHH enzyme system is induced by a wide variety of drugs and polycyclic
aromatic hydrocarbons, including the steroid hormones, benzo(a)pyrene and
3-methylcholanthrene, as well as TCDD and compounds that structurally resemble
TCDD, i.e., polychlorinated biphenyls, 2,3,7,8-tetrachlorodibenzofuran,
3,4,3',4'-tetrachloroazoxybenzene, and 3,4,3',4'-tetrachloroazobenzene (Poland
and Glover 1976b, Goldstein et al. 1977, Kouri et al. 1973).
Kouri et al. (1973) correlated induction of AHH by 3-methylcholanthrene
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COVALENT BINDING OF TCDD WITH MACROMOLECULES
There are two relevant studies that deal with the interaction of
2,3,7,8-tetrachlorodibenzo-p-dioxin with macromolecules. In the first study by
Guenthner et al. (1979), covalent binding of TCDD metabolites to cellular
macromolecules was measured in vitro after incubation of tritiated TCDD with
methylcholanthrene-induced B6C3F1 mouse microsomes, NADPH, and deproteinized
salmon DNA. The ratio of amount of DNA to the amount of protein in the reaction
vessel was 4:1. After incubation, the DNA was reisolated and treated with
DNase, phosphodiesterase, and alkaline phosphatase. TCDD metabolite-nucleoside
adducts were isolated by sephadex LH2Q column chromatography. The
radioactivity equivalent to TCDD that binds with DNA was 0.074 p mole/mg. When
DNA was incubated with proteinase before being applied to the sephadex column,
more than 80% of the covalently bound TCDD metabolites were removed, leaving
only 0.016 p mole/mg of TCDD-equivalent radioactivity bound to DNA.
The amount of covalently bound TCDD equivalent to microsomal protein was
20.6 p moles/mg, indicating this binding occurred approximately 1,000 to 2,000
times more readily than the binding to DNA.
In the second study, Poland and Glover (1979) examined the in vivo covalent
binding of TCDD (or metabolites) to rat 1iver macromolecules. In this study,
tritium labeled 3[H]TCDD, 95% chemically pure, was used (the impurity
consisted of radiolabeled trichloro- and pentachlorodibenzo-p-dioxin). A dose
of 7.5 mg/kg [1,6 3H]TCDD with specific activity of 39 Ci/mmole was
administered intraperitoneally to Sprague-Dawley rats (approximately 90
uCi/rat). The dose level and duration of the experiment was selected on the
basis of an acute toxicity study to obtain highest hepatic concentrations
without substantial hepatic toxicity. The livers of the animals were pooled and
15
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III. MUTAGENICITY
MUTAGENICITY OF 2,4,5-T
The mutagenicity of 2,4,5-T was evaluated by Ercegovich et al. (1977),
employing the procedure of Ames using five strains of Samonella typhinurium
without activation. The authors concluded that 2,4,5-T is non-mutagenic.
Anderson and Styles (1978) reported that 2,4,5-T at concentration ranges
from 4 to 2500 ug per plate did not cause reversions in any of the four strains
of Samonella typhimurium (TA 1535, TA 1538, TA 98, and TA 100) with or without
microsomal activation. Several other investigators have reported negative
responses with 2,4,5-T in bacterial test systems which have been summarized in a
review by Grant (1979). Zetterberg (1978) found that 2,4,5-T increased the back
mutation frequency in the histidine defective strain of Saccharomyces cerevisiae
at pH values below 4.5, by approximately 300 fold at 40 mg/ml and 5000 fold at
60 mg/ml. However, the percent of survivors at the lower concentration was less
than S% and at the higher concentration less than 0.1%. The author concluded
that 2,4,5-T is unlikely to cause mutations in a near neutral environment but
oral administration may increase the risk of somatic mutation in the gastric
tract where pH values are as low as 1.2. The 2,4,5-T used in these studies
contained less than 1 ppm dioxins.
Majumdar and Golia (1974) fed Drosophila melanogaster males 1000 ppm 2,4,5-T
for 15 days and found a small increase in the percentage of sex-linked recessive
lethals by 0.61% over controls values of 0.05%. The herbicide was reported to
contain no detectable amount of dioxin. Similar findings by Magnusson et al.
(1977) also showed 2,4,5-T to be weakly mutagenic in Drosophila. In a parallel
experiment, the known mutagen ethylmethanesulfonate at 250 ppm increased the
incidence of sex-linked Tethals by 13.65%. The CAG evaluated the negative
17
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count, desquamated tubules, and aberrant cells in the germinal epithelium.
These effects persisted after exposure was terminated. Chromosomal aberrations
were also observed during chronic dosing. The authors' methodology appears to
be inadequate, however, and thus no valid conclusions can be drawn from this
study. Majumdar and Hall (1973) reported that intraperitoneal injections of
2,4,5-T (containing no measurable amount of TCDD) into gerbils at concentrations
of 350 mg/kg for 5 days produced 8.2, 4.6, and 1.8 percent incidences of
chromatid gaps, chromatid breaks, and fragments, respectively, in bone marrow
cells. Control values were given as 1.0* for gaps, 0.2% for breaks, and 0.2"
for fragments. When the animals were treated at lower doses, no significant
increases in chromosomal abnormalities were observed. Jensen and Renberg (1976)
performed cytogenetic tests on mice injected with 2,4,5-T at 100 mg/kg. They
reported no increase over control values in incidences of micronuclei in
polychromatic or normochromatic erythrocytes, or polychromatic cells 24 hours or
0 days after the injection of the chemical. They were unable to confirm the
cytogenic effect reported by Majumdar and Hall (1973), but pointed out that they
used extremely high doses which might cause toxic effects leading to cell death
and chromosomal fragmentation.
Renner (1979) reported that 2,4,5-T induces a weak positive response in the
SCE test using Chinese hamster bone marrow cells. Four SCE's per cell were
observed in the control animals compared to 7/cell at 100 mg/kg and 8/cell at
250 mg/kg. This report cannot be evaluated, however, because no information is
provided concerning the route of administration, the number of animals used, the
number of cells scored per animal, the purity and source of the compound, and
whether or not the test was repeated.
Kilian et al. (1975) examined lymphocytes for chromosomal aberrations in
industrial workers exposed to 2,4,5-T in a Midland Michigan plant and compared
19
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MUTAGENICITY OF TCDD
Hussain et al. (1972) n -orted positive results in three microbial test
systems using a 99% pure TCDD sample obtained from the Food and Drug
Administration (FDA). Reversion to streptomycin independence in Escherichia
coli Sd-4 occurred with high frequency at a concentration of 2 ug
TCDD/ml. Reversion at the histidine locus of Salmonella typhimurium TA 1532
occurred at concentrations between 2 to 3 ug/ml. This indicates that TCDD
produces frameshift mutations by intercalation between base-pairs of DMA. A
doubling in the frequency of prophage-induction was observed in E. coli K-39
exposed to TCDD. These studies were not performed with metabolic activation,
indicating that TCDD is a direct-acting mutagen.
Seiler (1973) classified TCDD as a strong mutagen (where the ratio of number
of revertants from treated plates per 10^ bacteria divided by the number of
spontaneous revertants per 10^ bacteria is greater than 10) in the TA 1532
Salmonella strain which detects revertants through frameshift mutations.
However, this report did not give the source or purity of TCDD, the
concentration used in the assay, the toxicity of the compound where mutagenic
activity occurs, or whether microsomal activation was necessary.
However, McCann (personal communication) tested TCDD to be negative in the
standard plate test with strain TA 1532, with and without microsomal activation,
and Nebert et al. (1976) also reported that TCDD was not mutagenic in the
Salmonella in vitro assay. The differences between these laboratory results and
those discussed above could be due to several factors such as treatment
protocols, solubility problems of TCDD, and the high toxicity of this compound.
The Food and Drug Administration conducted a somatic in vivo cytogenetics
screening study on TCDD in rats and got negative results (Green 1975). Separate
experiments were performed with five multiple intraperitoneal doses or a single
21
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soil analysis to be greater than 10 ug/kg. Similar conclusions were reached by
Tuchmann-Duplesis (1977). Reports by both Reggiani (1977) and Tuchmann-Duplesis
(1977) state no increase in abnormal cytological changes in tissues of aborted
fetuses or in maternal blood in the Seveso zone during the exposure incidence to
TCDD. However, these findings are poorly documented and complete experimental
procedures and design used to evaluate the data were not available.
Furthermore, it appears from these reports that only gross macroscopic
alterations were sought and not microscopic lesions which are more difficult to
assess. Such lesions are very dangerous in that they may survive and be carried
to future generations.
CONCLUSIONS
There is some evidence that 2,4,5-T appears to be a weak mutagen causing
point mutations. The best evidence for this is in Drosophila and Saccharomyces
cerevisiae. However, evidence in Saccharomyces cerevisiae indicates the potency
of the mutagenic effect may be related to the ionization of the carboxyl group
of 2,4,5-T and is increased under more acidic conditions. At the present time,
epidemiological evidence and cytogenetic studies for mutagenicity concerning
TCDD are inconclusive. Also, the reported effects of TCDD as a "frameshift
mutagen" are inconsistent. Because TCDD is structurally similar to acridines
which produce frameshift mutations by intercalation in the DNA base-pairs, it is
recommended that the ability of TCDD to induce forward mutations in systems such
as mammalian cells in culture and the sex-linked recessive lethal tests in
Drosophilj be examined. Also, it is recommended that the mutagenic activity of
TCDD be re-tested in bacteria using a series of both strains which detect
frameshift and base-pair mutations.
23
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Toxicitv of TCDD
TCDD is one of the most toxic chemicals known to man. Oral LDso values,
shown in Table 3, range from 0.6 ug/kg orally for the male guinea pig to 275
ug/kg dermally for the rabbit. Deaths typically occur about a week or more
after treatment.
Poland et al. (1971) cite a study in which rapid death in guinea pigs
followed dermal application of the tarry residues from TCDD synthesis. When
rabbit ears were painted with soil extracts contaminated with TCDD,
hyperkeratosis and liver pathology were observed in the rabbits (Kimbrough
1974).
Kociba et al. (1978) conducted a 2-year chronic toxicity and oncogenicity
study of TCDD in rats. In this study, the animals were maintained for 2 years
on diets supplying 0.1, 0.01, and 0.001 ug TCDD/kg/day. Aside from carcinogenic
effects, ingestion of 0.1 ug/kg/day caused increased mortality, decreased weight
gain, slight depression of erythroid parameters, increased urinary excretion of
porphyrins and delta-aminolevulinic acid, along with increased serum activities
of alkaline phosphatase.
In chronic and acute oral TCDD toxicity studies on several animal species,
the liver, thyraus, and spleen have consistently been the target organs. Liver
damage, including necrotic and degenerative changes, lipid accumulation, and
increased liver weight, have been observed in mice, rats, and guinea pigs
following TCDD treatment (Vos et al. 1974, Jones and Greig 1975, Gupta et al.
1973, Goldstein et al. 1973, Kimmig and Schultz 1957). Liver damage was
markedly greater in rats receiving a comparable dose (Gupta et al. 1973). It
has been suggested that the fatty liver observed in mice may result from the
starvation and loss of body weight that occur following TCDD treatment, or may
be due to the induction of mixed-function oxidases (Jones and Greig 1975).
25
-------
Atrophy of the thymus and spleen has also consistently be n found in
laboratory animals (Yos et al. 1974, Kociba et al. 1975, Gup: et al. 1973).
Yos et al. (1973) reported that cell-mediated immunity was suppressed in guinea
pigs and mice in TCDD-induced lymphoid depleted thymuses. Thigpen et al. (1975)
found that mice receiving 1 ug/kg or more of TCDD by stomach tube once a week
for 4 weeks had increased susceptibility to Salmonella infection. Female
monkeys fed TCDD for 9 months showed hypocellularity of the bone marrow and
lymph nodes as well as hypertrophy, hyperplasia, and metaplasia of the bronchial
tree, epithelium, bile ducts, pancreatic ducts, and salivary gland ducts (Allen
et al. 1977).
Other effects of TCDD ingestion include suppression of reproductive function
in rats (Kociba et al. 1975) and disturbance of the hematopoietic system with
occasional hemorrhaging in monkeys, rats, and mice (Allen et al. 1977, Kociba et
al. 1975, Vos et al. 1974). TCDD interferes with the biosynthetic pathway of
heme by inducing delta-ami no!evulinic acid synthetase ( -ALA), which results in
hepatic porphyria in mice and rats (Goldstein et al. 1976). Increased urinary
excretion of uroporphyrins has been observed in rat feeding studies (Kociba et
al. 197', Goldstein et al. 1976).
TOXICITY OF 2,4,5-T, 2,4,5-TRICHLOROPHENOL, AND TCDD IN HUMANS
The most consistently reported toxic effect of 2,4,5-T,
2,4,5-trichlorophenol, and TCDD to humans is chloracne, a disfiguring and
long-term dermatitis. This has occurred in 2,4,5-T factory workers (Bauer et
al. 1961, Poland et al. 1971), 2,4,5-trichlorophenol workers (Kimmig and Schulz
1957, Bauer et al. 1961, Bleiberg et al. 1964, Goldmann 1972), and laboratory
workers accidentally exposed to TCDD (Oliver 1975). It has also been observed
in exposed populations following the accidental production of TCDD in'exothermic
27
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V. CARCINOGENICITY
CARCINOGENICITY OF 2,4,5-T IN MICE
Muranyi-Kovacs et al. (Oral) Mouse Study (1976)
Inbred C3Hf and XVII/G strains of mice were used. They were given 100
mg/liter of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) in drinking water for
2 months, beginning at 6 weeks of age. (The 2,-4,5-T product contained less than
0.05 ppm of 2,3,7 8-tetrachlorodibenzo-p-dioxin.) Thereafter, mice were given
2,4,5-T mixed with a sterile, commercial diet (UAR 1136) at concentrations of 80
ppm. It was not stated whether these levels represented maximum tolerated
values. However, the authors indicated that this dose was 1/40 of the 1050.
The mice were examined weekly for their general health and for the presence
of tumors. They were allowed to die or were killed in extremis. Complete
necropsies were performed and grossly altered organs were examined
histologically. The urinary bladder was distended with fixative in mice
suspected of having lesions.
C3Hf control male mice survived an average of 630 days; treated male mice,
511 days (P = 0.001); control females, 680 days; and treated females, 620 days.
Survival times for XVII/G control male mice were 521 days; for treated male
mice, 583 days; control females, 569 days; and for treated females, 641 days
(P = 0.01).
Tumor presence in C3Hf female mice ingesting 2,4,5-T is indicated in Table
4. The results show that 12 of 25 C3Hf female mice (48%) ingesting 2,4,5-T
developed tumors of all types, as compared to 9 of 44 control female mice (21")
(P = 0.03). No other strain-sex combination yielded statistically significant
values, as evidenced by the data in Tables 4 and 5. Benign and malignant tumors
were considered together in this study. The authors stated that the "hepatomas"
29
-------
and lung tumors, which were carcinomas and a"!veologenic adenomas, occurred in
the same proportions in control and treated mice. Treated C3Hf females had
several tumors at sites not found in the controls. The authors reported a
significant increase in total tumors in one strain and one sex of rats at one
dose level. In reaching this conclusion, they used the Peto method and
distinguished between incidental and nonincidental tumors.*
To clarify questions concerning the design, execution, and interpretation of
•i
this study, the CAG communicated with the principal author at the Curie
Foundation, Marseilles, France, From this discussion and from the published
account of this discussion it is concluded that: 1) this study was very
insensitive because insufficient numbers of animals were used in the treatment
groups; 2) the care of the animals was inadequate; 3) because the dose used, 80
ppm, was only 1/40 of the 1050, and appears to be less than the maximum
tolerated dose; 4) histologic examination of all animal tissues was not
performed; and 5) only macroscopically altered tissues were examined
histologically. In addition, the author recommended that more adequate studies
be conducted in a greater number of species.* Because of the severe deficiencies
in the study, the CAG concluded that this study does not provide significant
evidence for either the carcinogenicity or non-carcinogenicity of 2,4,5-T.
Muranyi-Kovacs et a!. (Subcutaneous) Mouse Study (1977)
In this study, the authors administered 2,4,5-T to two strains of mice, C3Hf
and XVII/G. Subcutaneous injections were given at 10 mg/kg of body weight in an
*These results are not considered to be evidence of an oncogenic response
because there is no valid basis for grouping tumors at all sites or for
distinguishing between incidental and nonincidental tumors. The author did not
report any increases in tumors for any specific target site. ,
31
-------
Innes et al. (Bionetics Laboratories 1968) (Oral) Mouse Study (1969)
The maximum tolerated dose of 2,4,5-T* was given to two hybrid strains of
mice, (C57BL/6 x C3H/Anf)Fi, B6C3F1 designated as "strain X," and (C57B/6 x
AKR)Fi, B6AKF1 designated as "strain Y." There were 18 treated mice and 18
untreated control mice of each strain and each sex. Each day, beginning at 7
days of age, 21.5 mg/kg of 2,4,5-T in 0.5* gelatin was administered by stomach
tube. After weaning at 28 days of age, 60 ppm of 2,4,5-T was mixed directly in
the diet and provided ad libitum. Treatment was continued for approximately 18
months.
At this time mice were killed and grossly examined both internally and
externally in the areas of the neck glands and the thoracic and abdominal
cavities. Histologic examination of major organs and all grossly visible
lesions was performed. Thyroid glands were not examined. The postmortem
results are given in Tables 7 and 8.
The results of the oral mouse study indicate that there was no significant
difference between the 2,4,5-T-treated and control groups of mice with respect
to tumors at specific sites, or total number of tumor bearing animals. This
study, however, does not provide significant evidence for the
non-carcinogenicity of 2,4,5-T because of certain defects in its design. The
use of small numbers of animals and the duration of the study, which was only 18
months rather than the entire lifetime, made the study relatively insensitive
for detecting an oncogenic effect.
* The Bionetics study did not report the level of TCDD contamination in the
2,4,5-T used. The 2,4,5-T used in a reproductive study conducted at
approximately the same time as the Bionetics study was reported to contain 30
ppm TCDD. It is possible that the contaminant of 2,4,5-T used in the Bionetics
study was the same as that of the 2,4,5-T used in the reproductive study.
However, this conclusion is far from certain without actual chemical analysis of
the 2,4,5-T used in the Bionetics study.
33
-------
Innes et al. (Bioneti'cs Laboratories 1968) (Subcutaneous) Mouse Study (1969)
2,4,5-T in dimethysulfoxide (DMSO) was given as a single subcutaneous
injection (215 mg/kg) to two strains of male and female mice (same strains as in
the oral study) at approximately 28 days of age. The mice were observed for
approximately 18 months. At that time mice were killed and examined grossly,
both internally and externally, in the areas of the neck, glands, and thoracic
and abdominal cavities. Histologic examinations of all major organs, as well as
all grossly visible lesions, were made. Thyroid glands were not examined. The
authors stated that histopathologic data did not show a statistically
significant difference between the 2,4,5-T-treated and control groups either
with respect to tumors at specific sites, or total number of tumor-bearing
animals. However, this study suffered from the same deficiencies as the Innes
et al. oral study. In addition, single subcutaneous dose studies are considered
to be highly insensitive for detecting an oncogenic response. Therefore, the
CAG does not consider this study to provide significant evidence of the
non-oncogenicity of 2,4,5-T.
35
-------
TABLE 9. CUMULATIVE MORTALITY DATA OF MALE RATS MAINTAINED ON DIETS
CONTAINING 2,4,5-T FOR 2 YEARS
Dose Level (mg/kg/day)
0
No. dead
(% dead)
30 10
No. dead No. dead
(% dead) (% dead)
3
No. dead
(% dead)
Original no.
in group
Days on test
0-30
31-60
61-90
91-120
• 121-150
151-180
181-210
211-240
241-270
271-300
301-330
331-360
361-390
391-420
421-450
451-480
481-510
511-510
541-570
571-600
601-630
631-660
661-690
691-720
721-728
Total no. of
rats studied
86
0
0
1(1,
1(1,
1(1,
1(1.
1(1,
1(1.
1(1.
2(2,
2(2,
2(2.
2(2.
5(5,
6(7.
9(10.
10(11.
16(18.
23(26.
32(37,
47(54.
67(77.
74(86.
77(89.5)
79(91.7)
.2)
.2)
.2)
.2)
.2)
.2)
.2)
.3)
.3)
.3)
.3)
.8)
.0)
.5)
.6)
.6)
.7)
.2)
.6)
.9)
.0)
50
0
0
0
0
0
0
0
0
0
0
0
0
2(4,
2(4.
2(4.
4(8.
6(12,
8(16,
11(22,
16(32.
19(38.
24(48.
27(54.0)3
32(64.0)3
39(78.0)a
.0)
.0)
.0)
.0)
.0)
.0)
.6)
.0)
.0)
.0)3
50
0
0
0
0
0
0
0
0
1(2
1(2
1(2
1(2
2(4
2(4
4(8
9(18
12(24
22(44
24(48
29(58
37(74
38(76.0)
42(84.0)
45(90.0)
46(92.0)
0)
0)
0)
0)
0)
0)
0)
0)
0)3
0)a
0)a
0)3
0)3
50
0
0
0
0
0
0
0
0
0
0
0
1(2.0)
2(4.0)
3(6.0)
4(8.0)
6(12.0)
10(20.0)
12(24
14(28
23(46
30(60
32(64
34(68
38(76
40(80
0)
0)
0)
0)
0)3
0)3
0)a
0)3
86
50
50
50
^statistically significant difference from control values by Fisher s
Exact Probability Test, P < 0.05.
37
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TABLE 11. STRATIFIED SQUAMOUS CELL CARCINOMA OF THE TONGUE OF SPRAGUE-DAWLEY
RATS FED WITH PURIFIED 2,4,5-T
Males
Females
Kociba
2,4,5-T
Controls
1/83
0/83
2
30
(P-va1ue)a
4/49
(P = 0.063)
1/49
(P = 0.371)
,4,5-T dosage
10
0/46
0/48
in mg/kg/day
3
Test for
1/50 <
0/48
Trendb
0.03
N.S.C
upvalues determined by Fisher s Exact Test lone-tailed)
bCochran's test for trend, one-tailed, scoring = 0, 1, 2, 3,
CN.S. = not significant at P = 0.05.
The increase in squamous cell carcinoma of the tongue in males at the 30
mg/kg/day dose level is marginally statistically significant (P = 0.063). Also,
the dose-related trend for the incidence of tongue tumors in males is
statistically significant in the Cochran-Armitage Test (P < 0.03).
Examination of male Sprague-Dawley rats in the Dow studies (Spartan
substrain) for historical controls found the following incidence of squamous
cell carcinomas of the tongue as illustrated in Table 12 (taken from selected
Tables provided to EPA by Dow which summarize the results of six Dow studies).
39
-------
cell carcinomas of the tongue in high dose males and 1 was in a control male
(Goodman 1980).
The increase in squamous cell carcinomas of the tongue in males at the 30
mg/kg/day dose level is statistically significant (P = 0.025) compared to
matched controls when using Drs. Squire's and Goodman's diagnoses. These
results provide highly suggestive evidence of the carcinogenic!ty of essentially
pure 2,4,5-T.
41
-------
The question arises whether these squamous cell carcinomas of the tongue
could have been induced by any TCDD contamination which was present below the
level of detection. Assuming TCDD was present at the level of detection (0.33
ppb), the amount of TCDD daily intake in the 2,4,5-T was estimated at less than
10 pg/kg/day. A second long-term TCDD study by Kociba (1978) on TCDD in
Sprague-Dawley rats, also showed increased squamous cell carcinoma of the tongue
in males. The results from the TCDD study are shown in Table 14.
TABLE 14. KOCIBA (1978) STUDY ON TCDD IN MALE SPRAGUE-DAWLEY RATS
pg/kg/day TCDD
Site Control 100,000 10,000 1,000
Tongue-stratified 0/76a 3/50 1/50 1/50
squamous cell carcinoma
Fisher's Exact Test (one-tailed) P = 0.06 N.S.b N.S.b
Test for trend exact test P = 0.01
aOn1y 76 of 85 tongues were examined microscopically.
bN.S. = not significant at P = 0.05.
Two exact probability tests both show statistical significance at the P =
0.06 level. The high dose response of 3/49 tumors at 100 ng/kg/day is
significant at the P = 0.06 level, and the exact test for trend has a P-value
= 0.01. Thus, the Kociba TCDD study provides suggestive evidence of a
carcinogenic effect in the tongues of males.
A comparison of the two Kociba studies at comparable TCDD dose levels for
comparable effects can only be made approximately. At 30/mg/kg/day 2,4,5-T, the
43
-------
only acetone in the diet. A fresh diet was prepared every 7 days.
Additional groups of 60 male and 60 female Sprague-Dawley rats served as
untreated controls. Rats in this group were supplied at 6 weeks of age by the
same source that had supplied the FQ generation of the three-generation study.
During the experiment, clinical signs, body weights, and consumption of food and
water, were monitored at regular intervals. Urinalyses were performed and
hematological and clinical chemistry parameters were determined for 10 rats from
each group at regular intervals. The same rats were used for measurements
throughout the experiments; the authors found no effects attributable to 2,4,5-T
in any of these observations. At 13 weeks, 10 rats were sacrificed from each
group and examined leaving 50 animals of each sex for long-term exposure. Rats
that died, were moribund, or killed during the experiment, and all surviving
rats killed after 130 weeks, were necropsied. All major tissues of all animals,
except for tissues of the survivors dosed at 3 mg/kg/day, were examined
histopathologically.
The authors reported that they found no evidence that the test compound had
a toxic or carcinogenic effect on either male or female rats. The type and
incidence of lesions observed were considered normal in old-age breeding rats of
the test strain. However, a statistically significant increase in interstitial
cell tumors of the testes in the high dose group of males (P = 0.014), as well
as a significant dose-related trend (P < 0.01) for these tumors was observed
when comparison is made to the incidence of these tumors in the pre-mix control
animals (Table 15). The significance of these results disappeared when
comparison was made to the untreated control group, which had an incidence of
testicular tumors higher than that in the high dose group. The incidence of
testicular tumors in the untreated controls (22/50 or 44%) is very significantly
higher (P < 0.01, using a one-tailed Fisher Exact Test) than that in the pre-mix
45
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TABLE \5. INTERSTITIAL-CELL TUMORS OF TESTES IN MALE RATS
Dose
untreated
control s
pre-mix
controls
10/mg/kg/day
group
30 mg/kg/day
group
Rats with
tumors
22/50
6/50
12/50
16/50
Percent animals
P-Va1uea with tumors
44%
12%
N.S.b 24%
0.014 32%
bN.S. = not significant at P * 0.05.
This study suffers from the following limitations: 1) the maximum tolerated
dose was apparently not used; 2) the observed testicular tumors are often
associated with old-age with variable incidences; 3) testicular masses were
reported in 14/28 of the animals exposed at the low dose (3 mg/kg/day), but only
six of these masses were diagnosed microscopically; and 4) the difference in the
incidences of testicular tumors in the two contol groups makes interpretation of
the significance of the testicular tumor incidence in treated groups uncertain.
In conclusion, the significance of the results concerning the incidence of
testicular tumors is uncertain. In addition, this test cannot be considered a
valid negative study of 2,4,5-T because the highest dose used was less than the
maximum tolerated dose. This reduced the sensitivity of the test for detecting
the possible oncogenic effects of 2,4,5-T.
The tongue, which was a site of increase in tumor incidence in the Kociba
studies was not initially examined microscopically in the Leuschner study.
Therefore, the CAG requested the histopathological examination*of tongue lesions
47
-------
days of age and continuing until they reached 28 days of age. At that time, 121
ppm of si 1 vex was administered daily in the diet. This study was carried out
for approximately 18 months. Mice were housed by sex, up to six in a cage, and
were given food and water ad libitum. All animals were observed daily for
clinical signs and weighed weekly. The doses administered were the maximum
tolerated doses, which had been selected from pre-chronic toxicity studies
performed before the initiation of the chronic study. The moribund mice were
killed, necropsied, and selectively examined microscopically, while surviving
animals were killed at approximately 18 months and necropsied. Heart, lungs,
liver, spleen, kidneys, adrenals, stomach, intestines, genital organs, and
tissue masses were placed in formalin. They were later sectioned, stained with
hematoxylin and eosin, and examined microscopically. All but five mice, three
B6C3F1 male and two B6AKF1 male or female, survived 18 months. Table 16
identifies the types of tumors and the groups in which they were found.
TABLE 16. TUMORS IN MICE EXPOSED ORALLY TO SILYEX
Type of Tumor
Reticul urn-cell sarcoma, type A
Pulmonary adenoma
Hepatoma
Mammary adenocarcinoma
Angioma
Gastric papilloma
Adrenal cortical adenoma
B6C3F1
M
1
1
5
0
1
0
0
Mice
F
1
0
0
1
0
2
0
B6AKF1
M
0
1
0
0
0
0
0
Mice
F
0
0
0
0
0
0
1
49
-------
were a number of deficiencies in this study: 1) only one subcutaneous injection
was given, 2) the number of animals in the treatment group (18) was too small,
and 3) the experiment was terminated after only 18 months. Because of these
deficiencies, the test was relatively insensitive for detecting an oncogenic
effect of si!vex.
Dow Chemical Company (Oral) Rat Study, summarized in Mullison (1966) and Gehring
and Betso (1978)
Groups of Wister rats (30 males and 30 females in each group) were fed diets
containing 0.0, 0.03, 0.003, and 0.001% Kurosol®SL (potassium salt of si!vex)
for up to 24 months. Administration of the test compound began at 50 days of
age. Animals were sacrificed at 12 and 18 months so that the group sizes at the
end of the 2-year study could not have been more than 21 or 22 per sex; they may
have been even smaller. However, the size of the groups at the end of the study
cannot be exactly determined since no data were provided on the extent to which
animals, other than the ones sacrificed, died before the end of the study.
There was no evidence of a toxic effect or reduced survival in female rats
administered any dose compared to controls. Therefore, it does not appear that
the females were administered the maximum tolerated dose. Since high dose males
exhibited a significant decrease in average body weights, it appears that they
were administered a maximum tolerated dose.
No significant increase in tumors was reported. However, because small
groups of animals were used and the maximum tolerated dose was apparently not
used in the high dose females, this study cannot be considered as significant
evidence of the non-carcinogenicity of si!vex in rats.
51
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CARCINOGENICITY OF TCDD IN RATS AND MICE
Kociba et al. (Oral) Rat Study (1977. 1978)
Although this study was reported in published form in Toxicology and Applied
Pharmacology (1978), a fuller version was submitted in an unpublished report
(Kociba et al., Dow Chemical Company, September 28, 1977).
In this study, groups of 50 Sprague-Dawley rats (Spartan substrain) of each
sex were maintained for up to 2 years on diets providing 0.1, 0.01, or 0.001
ug/kg/day TCDD. Vehicle control groups comprised 86 animals of each sex. The
test was appropriately conducted with the high dose group at a level which
induced signs of tissue toxicity, reduced weight increments in both sexes, and
shortened lifespans in female rats. Clinical tests performed at intervals
during the study monitored organ specific toxicity, particularly of the liver.
Pathologic examinations included histopathologic evaluation of all major tissues
in both the high dose and control animals, but only of selected tissues
identified as possible target organs and suspect tumors in lower dose groups.
This approach is suitable for the identification of a carcinogenic effect, but
does not determine actual tumor incidences in all groups except in those organs
identified as target organs. It, therefore, is adequate to define dose-response
relationships only in these target organs. Tissues examined from most animals
in all dose groups included liver, lungs, kidneys, urinary bladdar, tongue,
brain, testes/ovaries, and prostate/uterus. For these tissues, a quantitative
analysis can be performed using the actual number of tissues examined
histopathologically for animals at risk. For other tissues (excluding skin,
mammary glands, and nasal turbinates/hard palate), actual tumor incidence cannot
be evaluated for the two lower doses. For skin and mammary glands, the number
of animals necropsied is the appropriate denominator to determine incidence,
because detection of these tumors is based on observation of the tumor at
53
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female rats at doses of 0.1 nd 0.01 ug/kg/day (2200 and 2 D ppt in the diet,
respectively). The increase of hepatocellular carcinomas alone, in the high
dose females, was also highly significant. In addition, at the highest dose
level, TCDD induced a statistically significant increase in stratified squamous
cell carcinomas of the hard palate and/or nasal turbinates in both males and
females, squamous cell carcinomas of the tongue in males, and keratinizing
squamous cell carcinomas of the-lungs (highly significant) in females (tumor
incidences reported in Tables 17, 18, and 19).
TABLE 17. HEPATOCELLULAR CARCINOMAS AND HEPATOCELLULAR
HYPERPLASTIC NODULES IN FEMALE SPRAGUE-DAWLEY RATS MAINTAINED ON
DIETS CONTAINING TCDD
Dose level Rats with
Rats
with
ug/kg/day hepatocellular hepatocellular
hyperplastic carcinomas9
nodules
0 8/86 (9%)
0.001 3/50 (6%)
(22 ppt)
0.01 18/50 (36%)
(210 ppt)
0.1 23/48 (48%)
(2200 ppt)
1/86
0/50
2/50
11/48
(P = 5
(1%)
(0%)
(4%)
(23%)
.6 x 10-5)
Total number
of rats wi th
both types
of tumors3
9/86 (10%)
3/50 (6%)
18/50 (36%)b
(P = 4.37 x 10'4)
34/48 (71%)
(P = 9.53 x 10-13)
aP-values calculated using the Fisher Exact Test (one-tailed).
&Two rats had both hepatocellular carcinomas and hyperplastic nodules.
55
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Dr. Robert Squire, pathologist at the Johns Hopkins University Medical
School and consultant to the CAG, evluated the histopathological slides from Dow
Chemical Company's 2-year rat feeding studies on
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by Kociba et al. Dr. Squire and his
associates examined all livers, tongues, hard palates, and nasal turbinates, and
lungs available from TCDD study. His histopathological findings, as well as Dr.
Kociba's histopathological evaluations, are summarized in Tables 20 and 21 and
Appendix B. Although there are some differences between the diagnoses of Kociba
and Squire, the conclusions about the target organ for cancer induction, and the
dose levels at which induction occurred are the same whether Squire's or
Kociba's diaanoses are considered.
57
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TABLE 21. DRS. SQUIRE'S AND KOCIBA'S REVIEW OF DOW TCOD ORAL RAT STUDY (8/15/80)
Sprague-Dawley Rats - Spartan Substrain (2 yrs.)
MALES
in
10
Tissues and Diagnoses
Nasal Turbi nates/Hard
Palate squamous cell
carcinomas
0
(control)
S K
0/55 0/51
Dose Levels (ug/kg/day)
0.001 0.01 0.1
S K S K S
1/34 1/34 0/26 0/27 6/30
K
4/30?
Tongue
Squamous cell
carcinomas
0/77
2/44
1/49
(P = 1.36 x ID"3)
3/44 3/42
(P = 4.60 x 10-2) (p = 4.34 x
Total - 1 or 2 above
(each rat had at
least one tumor above)
0/77
2/44
S = Dr. Squire's histopathologic analysis
K = Dr. Kociba's histopathologic analysis
1/49
9/44
(P = 6.28 x 10-5)
-------
TABLE 22. INCIDENCE OF PRIMARY TUMORS IN MALE RATS
ADMINISTERED TCDD BY GAVAGE
Type of tumor
Vehicle
control
Low Dosea
0.01
ug/kg/week
Mid Dosea
0.05
High Dose3
0.5
Subcutaneous tissue
Fibrosarcoma
Liver
Neoplastic nodule
or hepatocellular
carcinoma
Adrenal
Cortical adenoma
Thyroid
Follicular cell
adenoma
3/75 (4%) 1/50 (2%) 3/50 (6*)
7/50 (14%)
P = 0.048
0/74 (0%) 0/50 (0%) 0/50 (0%) 3/50 (6%}
6/72 (8%) 9/50 (18%) 12/49 (24%) 9/49 (18%)
1/69 (1%) 5/48 (10%) 6/50 (16%) 10/50 (20%)
P = 0.042 P = 0.021 P = 0.001
Thyroid
Follicular cell
adenoma or carcinoma 1/69 (2%) 5/48 (10%) 8/50 (16%) 11/50 (22%)
P = 0.042 P = 0.004 P < 0.001
dP-va"lues calculated using the Fisher Exact Test.
In female rats, a statistically significant increase of each of the
following tumors was found in the high dose group: hepatocellular carcinomas
and neoplastic nodules (P = 0.001), subcutaneous tissue fibrosarcomas (P =
0.023), and adrenal cortical adenomas (P = 0.039) as shown in Table 23.
These results confirm the carcinogenic effect observed in the Kociba et al
(1978) study using Sprague-Dawley (Spartan substrain) rats.
61
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Van Miller et al. (Oral) Rat Study (1977)
Male Sprague-Dawley rats weighing approximately 60 grams each were used.
There were 2 rats in each cage and 10 rats in each group. Rats ingested ground
chow for only 2 weeks. They were then given 2,3,7,8-tetrachlorodibenzo-p-dioxin
(TCDD) in the following concentrations: 0, 1, 5, 50, 500 parts per trillion
(ppt, 10~12 gram TCDD/gram food); and 1, 5, 50, 500, and 1000 parts per
billion (ppb, 10~9 gram TCDD/gram food). Rats ingested the diets with TCDD
for 78 weeks, and thereafter were kept on a control diet. Laparotomies were
performed on all surviving rats at the 65th week and biopsies were taken from
all tumors observed. Surviving rats were killed at 95 weeks.
Food intake was significantly lower in rats ingesting 50, 500, or 1000 ppb
TCDD than in the controls, and they lost weight. All of the rats in the dose
groups died between the second and fourth weeks of treatment. The food intake
for rats receiving the other dose levels was similar to that of the controls.
Weight gain was significantly less for rats given 5 ppb TCDD. TCDD intake and
mortality of rats are shown in Table 24.
TABLE 24. TCDD INTAKE AND MORTALITY IN RATS
Dose3
0 ppt
1 ppt
5 ppt
50 ppt
500 ppt
1 ppb
5 ppb
Weekly
(ug/kg
—
0.
0.
0.
0.
0.
2.
dose per rat
body weight)
« « •
0003
001
01
1
4
0
Week of
first death
68
86
33
69
17
31
31
Number of rats
dead
6/10
2/10
4/10
4/10
5/10
10/10
10/10
at 95th week
(60%)
(20%)
(40%)
(40%)
(50%)
(100%)
(100%)
aRats at 50, 500, and 1000 ppb dose levels were all dead within four
week s.
63
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TABLE 25. BENIGN AND MALIGNANT TUMORS IN RATS INGESTING TCDD
Dose3
0
1 ppt
5 ppt
50 ppt
500 ppt
1 ppb
5 ppb
Benign
0
0
1
2
2
0
8
Mai ignant
0
0
5
1
2
4
2
Number of
tumors
0
. 0
6C
36
4f
5h
IQi
»
Number of rats
with tumors
0/10 (0%)b
0/10 (0%}
5/10 (50%)d
3/10 (30%)
4/10 (40%)§
4/10 (40%)
7/10 (70%)
aRats at dose levels 50, 500, and luOO ppb were all dead within four
weeks.
b40 male rats used as controls for another study, received at the same
time and kept under identical conditions, did not have neoplasms when killed at
18 months.
cl rat had ear duct carcinoma and lymphocytic leukemia
1 adenocarcinoma (kidney)
1 malignant histiocytoma (retroperitoneal)
1 angiosarcoma (skin)
1 Leydig cell adenoma (testis)
^Three rats died with aplastic anemia.
el fibrosarcoma (muscle)
1 squamous cell tumor (skin)
1 astrocytoma (brain)
fl fibroma (striated muscle)
1 carcinoma (skin)
1 adenocarcinoma (kidney)
1 sclerosing seminoma (testis)
90ne rat had a severe liver infarction.
nl rat cholangiocarcinoma and malignant histiocytomas (retroperitoneal)
1 angiosarcoma (skin)
1 glioblastoma (brain)
1 malignant histiocytoma (retroperitoneal)
il rat had squamous cell tumor (lung) and neoplastic nodule (liver)
2 cholangiocarcinoma and neoplastic nodules (liver)
3 squamous cell tumors (lung)
1 neoplastic nodule
65
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Toth et al. (Oral) Mouse Study (1979)
This study investigated the carcinogenicity of TCDD in Swiss mice.
Ten-week-old outbred Swiss /H/Riop mice were used. TCDD was administered in a
sunflower oil vehicle by gavage to groups of 45 male mice once a week at doses
of 7.0, 0.7, and 0.007 ug/kg body weight for a year (groups 9, 10, and 11,
respectively, in Table 27). Matched male vehicle controls were administered
sunflower oil once a week. Matched controls to a companion study investigating
the carcinogenicity of (2,4,5-trichlorophenoxy)ethanol (TCPE) contaminated with
low levels of TCDD, were administered carboxymethyl cellulose (the vehicle used
in that study) once a week. Two untreated controls were also maintained.
This study appears to be generally well-conducted. However, the
administration of TCDD over a period of only one year, which is far short of the
life expectancy of the mice used, made the study relatively insensitive.
Animals were followed for their entire lifetimes. Autopsies were performed
after spontaneous death or when the mice were moribund, and all organs were
examined histologically. Sections were stained with hematoxylin and eosin for
light microscopy. Pathological findings were evaluated and analyzed
statistically. The findings-of the TCDD study and the comparison study on TCPE
are given in Table 27 (reproduced from the journal in which this study is
reported).
Analysis of the results of this study focused on the incidence of liver
tumors in the groups treated with TCDD and the incidence of these tumors in the
matched controls (group 12) and in the males in the three other control groups.
Males in groups 3 and 8, the two untreated control groups, had 26% and 33% liver
tumors, respectively (P > 0.20). The carboxymethyl cellulose male controls
(group 7) had 33% (32/96) liver tumors. No significant differences in liver
«
tumors were observed when males in all four control groups were compared to each
67
-------
other (P > 0.05). Nevertheless, there was evidence that the incidence of liver
tumors in the control groups was associated with the average lifespan in the
respective groups. The two groups that had less than 600 days average survival
(groups 3 and 12) had the fewest liver tumors (26% and 18%, respectively). On
the other hand, the two groups that had an average survival of greater than 600
days (groups 7 and 8), had 33% liver tumors each. The test for linear trend
(tumors vs. days of average survival) was not quite significant (P = 0.065).
Among the three treatment groups (groups 9, 10, and 11), the middle dose
(0.7 ug/kg) showed the highest incidence of liver tumors (21/44 = 48%). This
incidence was significantly higher than the incidence of liver tumors in either
the sunflower oil controls (P < 0.01) or the pooled controls (all four control
groups combined) (P < 0.025).
The highest dose group (7.0 ug/kg) had an increased incidence of liver
tumors compared to the matched sunflower oil controls (13/43 = 30") but this
increase was not statistically significant (P = 0.11). The incidence of liver
tumors in the high dose group was comparable to that of the pooled controls.
The highest dose group, however, had a much reduced average survival in
comparison to any of the control groups (only 424 days compared to 577, 588,
615, and 651 days in the four control groups). This poor survival may have
accounted for the lack of a statistically significant increase in liver tumors
in the high dose group. Furthermore, if time-to-tumor data had been available,
it is highly likely that the high dose group would have shown a significant
decrease in time-to-tumor compared to the controls. Therefore, the increase in
liver tumors that was observed in the high dose group in comparison to the
matched control group, although not statistically significant, is considered to
be consistent with an oncogenic effect.
69
-------
thyroid follicul ar-cell adenoma, and cortical adenoma or carcinoma were also
observed in the high dose group (Table 29).
The incidence of liver tumors observed in this study confirms the earlier
observation of an increase in liver tumors in the male mouse study performed by
Toth et al. (1979).
TABLE 28. INCIDENCE OF PRIMARY TUMORS IN MALE MICE
ADMINISTERED TCDD BY GAVAGE
Type of tumor
Vehicle
control
Low dose
0.01
ug/kg/week
Mid dose
0.05
High dose3
0.5
Liver
Hepatocellular
adenoma
7/73 (10%) 3/49 (6%) 5/49 (10%) 10/50 (20%)
Liver
Hepatocellular
carcinomas
Liver
Hepatocellular
adenoma and
carcinomas
8/73 (11%) 9/49 (18%) 8/49 (16%)
15/73 (21%) 12/49 (24%) 13/49 (27%)
17/50 (34%)
P = 0.002
27/50 (54%)
P < 0.001
dP-values calculated using the Fisher Exact Test.
71
-------
Other Related Studies
Pitot et al. Prr otion Study in Rats (1980) --
Pi tot et al. (1980) investigated the hypothesis that development of
hepatocellular carcinomas of the liver with chronic administration of TCDD was
the result of the promoting activity of TCDD on cells already initiated by
dietary or other environmental carcinogens. The manuscript of this study has
been submitted to Cancer Research for publication.
In this study, a two-stage model of hepatocarcinogenesis was used.
Twenty-four hours after a partial hepatectomy (to cause cell proliferation),
female Sprague-Dawley rats were divided into seven groups (Table 30). The
animals in groups 1, 5, 6, and 7 received diethylnitrosamine (DEN). The rats in
group 1 were then maintained on a standard laboratory diet for 32 weeks. The
rats in groups 2 and 3 received no DEN, but starting one week after hepatectomy
received biweekly subcutaneous injections of 0.14 or 1.4 ug/kg of TCDD in corn
oil for a period of 28 weeks (TCDD was 98.6* pure and provided by Dow Chemical
Co.). Groups 5 and 6 received DEN, and one week later were initiated on a
regimen of 14 biweekly injections of 0.14 and 1.4 ug/kg of TCDD. The animals in
group 4 received 0.05% sodium phenobarbital in the diet starting one week after
partial hepatectomy for 28 weeks, and the animals in group 5 received DEN and
one week later were also administered 0.05* sodium phenobarbital in the diet for
the duration of the experiment. At the end of the experiment, rats were killed
and sections of the liver were removed and frozen on solid C02. Serial
sections of the frozen blocks of liver were cut and stained consecutively for
glucose-6-phosphatase (GSPase), canalicular ATPase,Y-glutamyl transpeptidase
GGTase) with haematoxylin and eosin. The number of enzyme-altered foci were
determined from photographs of histochemically stained sections.
Hepatocarcinomas were diagnosed by standard histopathological criteria.
73
-------
The results presented in Table 30 showed that the number of foci with single
enzyme changes, the number of foci with multiple enzyme changes, and the total
liver volume affected, substantially increased with the administration of TCDD.
No carcinomas were detected in four rats treated with DEN only, but five of
seven rats treated biweekly with TCDD at 1.4 ug/kg in addition to DEN had
hepatocellular carcinomas, and six of seven rats had hepatocellular carcinomas
or hepatocellular neoplastic nodules with a statistical significance
(P = 0.0075). Three of five rats treated biweekly with TCDD at 0.14 ug/kg in
addition to DEN had hepatocellular neoplastic nodules (P = 0.083). Rats
receiving only TCDD after partial hepatectomy showed no significant increase in
enzyme-altered foci and no neoplasia.
The results of this study provide evidence that TCDD acts as a potent
promoter in this two-stage model of hepatocarcinogenesis, causing increased
neoplasia and increases in enzyme-altered foci at exceedingly low levels.
National Cancer Institute Skin Painting Study in Mice (1980b) --
This cancer bioassay of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for
possible carcinogenicity was tested by the Illinois Institute of Technology
under a contract sponsored by the National Cancer Institute (NCI) in
Swiss-Webster mice. In this study, groups of 30 male and female Swiss-Webster
mice were used. TCDD in acetone suspension was applied to skin of mice 3 days
per week for 104 weeks. Male mice received 0.001 ug TCDD per application while
the female mice received 0.005 ug TCDD per application.
In another experiment, the same number of animals were pretreated with one
application of 50 ug 7,12-dimethylbenz(a)anthracene (DMBA*) in 0.1 ml acetone
*DMBA obtained from K and K Laboratories (Cleveland, Ohio). Its purity was
not evaluated by NCI but stated by the manufacturer to be at least 95%.
75
-------
Berry et al. Skin Painting Study in Mice (1978, 1979) --
Berry et al. (1978) applied TCDD in acetone solution at 0.1 ug/mouse twice
weekly for 30 weeks to the skin of 30 female Charles River CD-I mice after
initiation with a single dermal application of the known skin carcinogen DMBA in
acetone. After 30 weeks of promotion with TCDD, no papillomas were observed on
the DMBA-initiated mice. In the positive controls, DMBA-initiated mice were
treated with 12-0-tetradecanoylphorbol-13-acetate (TPA) for 30 weeks; 92% of
these mice developed tumors.
Berry et al. (1979) also studied the effects of treatment with TCDD and
7,12-dimethylbenz(a)anthracene (DMBA) in a two-stage tumorigenesis bioassay in
mouse skin. In this study, tumors on the shaved skin of female CD-I mice were
initiated by topical application of DMBA and were promoted with TPA.
Pretreatment with TCDD markedly inhibited the initiation of tumors by DMBA. The
effects were greatest when TCDD was applied 3 to 5 days before initiation and
were negligible when it was applied only 5 minutes before initiation. The
inhibition was almost complete (94 to 96») when a single dose of 1 ug of
TCDD/mouse was applied, but was only slightly less effective (89%) when the dose
was reduced to 10 ug/mouse. The time course of the inhibitory effects was
closely parallel to the time course of induction of arylhydrocarbon hydroxylase
in the skin of the mice. It was also associated with substantial reduction in
the covalent binding of the DMBA metabolite to DMA and RNA, but with no change
in their binding to protein.
The same authors also reported inhibitory effects of TCDD on the initiation
of mouse skin tumors by benz(a)pyrene (BAP), although the effect was not as
large (maximum 65%) with BAP as with DMBA.
77
-------
After treatment, the mice were observed for 36 weeks, during which time they
were palpated weekly for the presence of tumors; latency was calculated when the
subcutaneous tumors became 1 cm in diameter. Only tumors characterized
histologically as fibrosarcomas at the site of inoculation were considered. It
is unclear whether or not these were the only tumor types observed. The term
"carcinogenic index" used by the authors was defined as the percentage of tumor
incidence 8 months after treatment divided by the average latency in days
multiplied by 100. No details were given of the number of animals in each group
at the start of each experiment but the numbers dying in the first 28 days and
the numbers at risk (surviving 36 weeks) were tabulated. The results of this
study are shown in Tables 32 and 33.
No subcutaneous tumors were observed in controls or in mice treated with
TCDD alone. In B6 (responsive) mice, the administration of TCDD did not
significantly enhance the induction of tumors by MCA. However, in both
experiments involving D2 (nonresponsive) mice, the administration of TCDD
simultaneously with MCA appeared to enhance the carcinogenic response. The
"carcinogenic index" increased from 1 to 6 in groups treated with MCA alone to
14 in the group treated subcutaneously with TCDD at 1 ug/kg, and 13 to 15 in the
groups treated intraperitoneally with TCDD at 100 ug/kg. The authors concluded
that TCDD acts as a cocarcinogen. They speculated that it may act by local
induction of AHH at the site of inoculation.
A more appropriate statistical analysis would be a comparison of tumor
incidence in TCDD-treated groups with tumor incidence in corresponding MCA-
treated groups within the same experiment. The results of this analysis are
given in Table 34.
From these results, the CAG concluded that the experiment adequately
79
-------
TABLE 33. EFFECT OF INTRAPERITONEAL OR SUBCUTANEOUS ADMINISTRATION OF TCDO GIVEN 2 DAYS BEFORE OR SIMULTANEOUS
WITH SUBCUTANEOUS ADMINISTRATION OF MCA ON TUMORIGENESIS IN D2 MICE
(KouM et al. 1978)
Treatment
No.
of mice
dying because
-2 days
None
l.p. p-dloxane
1.p. TCDD (100 ug/kg)
None
None
None
None
None
None
None
None
0 days of treatment
s
s
s
1
i
1
s
s
s
s
s
.c.
.c.
.c.
.p.
.p.
.p.
.c.
.c.
.c.
.c.
.c.
MCA
f1CA
MCA
p-d1oxane x s.c. MCA
TCDD (100 ug/kg) + s.c. MCA
TCDD (1 ug/kg) + s.c. MCA
p-dioxane + s.c. MCA
TCDD (100 ug/kg)
TCDD (100 ug/kg + s.c. MCA
TCDD (1 ug/kg)
TCDD (1 ug/kg + s.c. MCA
0
10
35
5
38
22
2
8
18
2
2
No. of mice
at risk for ''
tumors
30
40
65
45
62
78
68
42
82
48
98
No. of
' mice with
tumors
3
4
9
5
17
8
8
0
46
0
21
1 of mice
with tumors
10
10
14
11
27
10
12
,0
,&
0
21
Average
latency
(days)
177
194
145
176
183
162
180.
145
154
Carcino-
genic Index
6
5
10
6
15*
6
6
-
383
14a
aThese carcinogenic Index values lie outside the 99% confidence interval.
-------
demonstrated tt-•> enhancement by TCDD of tumor induction when TCDD was
administered s- lultaneously with MCA at the higher dose (100 ug/kg). The
reported results at the lower dose (1 ug/kg) are not statistically significant
unless the reduction in latency is taken into account, which is difficult to do
rigorously. Despite defects in reporting (failure to specify the initial number
of animals in each group and to report tumor incidence by sex), the results
provide convincing evidence that TCDD acts as a cocarcinogen. The failure of
TCDD to induce tumors when administered alone was not unexpected since only a
single dose was administered and the duration of the study was very short (36
week s).
83
-------
TABLE 35. COMPARISON OF DOSE LEVELS OF TCDD IN 2,4,5-T* STUDIES
WITH RESPECT TO THE TCDD STUDY IN MICE WHERE POSITIVE TUMOR
INCIDENCE WAS OBSERVED
Study
Strain of mouse
Route Dose-level
2,4,5-T TCDD
mg/kg/day ug/kg/day
Tumors observed
(Innes)
Bionetics
FI hybrid of
C57bl/6 and
C3H/AWf (Strain
"A") or "X"
diet
0.27
FI hybrid of
C57B1/6 and
AKR (Strain "Y1
or "B")
diet
0.27
Muranyi-
Kovacs
NCI
Toth
(Innes)
Bionetics
Muranyi-
Kovacs
XVIIG diet 12
C3Hf diet 12
B6C3F1 gavage
Maleb
B6C3F1 gavage
Femal eb
Swiss male gavage
"A or Y" subcutaneous. 215 mg/kg
(one dose only)
"Y or B"
XVIIGi subcutaneous 10(4 doses only)
C3Hf 10(4 doses only)
6.0 x lO'4
6.0 x 10'4
1.42 x ID'3
7.1 x ID'3
7.1 x 10-2 +
5.7 x 10-3
2.85 x ID'2
0.285 +
1.0 +
0.1 +
0.001
6.4
(one dose only)
5 x 10'4 (4 doses only)
5 x 10~4 (4 doses only)
aTCDD contaminant in 2,4,5-1
30 ppm--Innes et al. Study (assumed in this analysis, see page 32)
0.05 ppm--Muranyi-Kovacs et al. Study
0.05 ppm--Leuschner et al. (German Study)
0.33 ppb--Dow Chemical Company Study
bCarcinogenic in male and/or female.
85
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Potency of TCDD
The carcinogenic potency of TCDD is greater than that of aflatoxin B]_,
which is one of the most potent carcinogens known. This conclusion comes from a
comparison of the tumor incidence in male Fischer rats (Wogan et al. 1974),
which were fed 50 ppb of aflatoxin BI, with the incidence of the same tumor
type in female Sprague-Dawley rats (Kociba et al. 1977) fed 0.1 ug/kg/day
(2.2 ppb). The potency of each of these compounds was estimated by calculating
the slope of the linear one-hit model for these compounds. The slope (B) is
calculated according to the following formula:
B = 1 In (1 - Pr)
d = dose inducing carcinogenic effect in the respective studies on TCDD and
aflatoxin.
Pc = tumor incidence in control animals in the respective studies.
P = tumor incidence in treated animals in the respective studies at dose d.
This calculation was made on the basis of the lowest dose level at which
TCDD or aflatoxin BI caused a significant increase in hepatocellular
carcinomas, the incidence of hepatocellular carcinomas at the respective dose
levels, and the spontaneous incidence of this type of cancer in the control
animals of each study.*
Table 37 shows that TCDD is more potent than aflatoxin by a factor of
0.110/0.032 = 3.45. On this basis, it is estimated that TCDD is a more potent
carcinogen than aflatoxin BI roughly by a factor of three.
AWogan et al. are not clear on their histologic classification of
preneoplastic lesions. Therefore, only carcinomas were selected for calculating
B.
87
-------
The question arises as to whether the carcinogenic action of TCDD by itself
such as exhibited in the Kociba et al. and the N, '. studies on rats and mice
could be due to the action of TCDD as a carcinogen and/or a promoting agent.
There is evidence that TCDD can be metabolized to a reactive electrophilic
metabolite which could react with DNA and thereby produce genetic damage of the
sort that is associated with the induction of cancer. However, the reactivity
of this metabolite is extremely high with cellular proteins and, to date, the
degree of interaction with DNA that has been demonstrated is low. This may be
peculiar to the tissues that have been examined for this reaction so far but may
not be generally applicable to the reaction of TCDD with DNA in the body.
Furthermore, TCDD has a chemical structure which makes it likely that it could
intercalate into DNA and also act as a genotoxic carcinogen. Promoting agents,
when administered alone, characteristically produce a relatively small increase
in the occurrence of tumors and these tumors are of the sort that occur
spontaneously. This is not characteristic of TCDD, particularly in relation to
its ability to induce squamous carcinomas of the lung and of the hard palate and
nasal turbinates. Squamous carcinomas of the lung are exceedingly uncommon in
the rat in contrast to adenomas of the lung. For these reasons, the CAG
believes that it is prudent, given the present state of knowledge, to regard
TCDD as a complete carcinogen as well as a promoting and cocarcinogenic agent.
89
-------
Two case-control studies were conducted, the first in northern Sweden
(referred to below as Study A), and tne second in the southern part of the
country (Study B). The frequencies of exposure to the substances of primary
interest are shown in Table 39. In the north, occupational exposure to
phenoxyacetic acids took place in both forestry and agricultural work. In the
south, these exposures were predominantly agricultural. The phenoxyacetic acids
to which exposure occurred consisted predominantly of 2,4,5-T and 2,4-D in both
studies. Exposure to 2,4,5-T in the absence of 2,4-D was rarely reported in
either study. Exposure to chlorophenols, which contain chlorinated
dibenzodioxin impurities (Levin et al. 1976), occurred mostly in sawmill work
and paper pulp production. Very few persons reported joint exposure to both
phenoxyacetic acids and chlorophenols in these studies.
Of the two phenoxyacetic acids to which exposure predominantly occurred
(2,4,5-T and 2,4-D), only 2,4,5-T is known to be contaminated with TCDD. There
are two published oncogenicity studies on 2,4-D, one in rats (Hanson et al.
1971) and the other in mice (Innes et al. 1969). These studies are inadequate
to assess the carcinogenicity of 2,4-D. In study B, a relative risk of 4.9 (90%
confidence interval 1.6 - 11.1)* was found in relation to exposure to phenoxy,
acid herbicides other than 2,4,5-T (2,4-0, MCPA, mecoprop, dichloroprop).
Relative risks in relation to the three major categories of exposure are
shown in Table 40.** Studies A and B indicate a risk of developing soft tissue
*Test-based method of Miettinen (1976); chi-square statistic, no continuity
correction.
**In the analyses considering phenoxyacetic acids only and chlorophenols
only, persons exposed to the other category of substances were excluded. In
study A, the three persons exposed to both chlorophenols and phenoxyacetic acids
were included in all comparisons.
91
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sarcomas among workers exposed to phenoxyacetic acids only, chlorophenols only,
or phenoxyacetic acids and/or chlorophenols several times higher than among
persons not exposed to these chemicals. In each comparison, the point estimate
of relative risk is high and unlikely to have resulted by chance alone.
Little is known of the etiology of soft tissue sarcoma, so the consideration
of confounding in these studies is largely a hypothetical matter. Age, sex, and
place of residence were eliminated as possible confounding factors in the
selection of controls.* Because of the high correlation between exposure to the
substances of interest and employment in agriculture and forestry, a reasonable
hypothesis could be developed that some unknown factor present in these
occupations was responsible for the elevated relative risks.
To test this hypothesis, it is possible to calculate the relative risk in
relation to phenoxyacetic acid exposure in Study B, restricting the analysis to
workers within agriculture and forestry. The result is a relative risk of 6.1
(90* confidence interval 2.4 to 15.4). This finding strongly suggests that a
confounding risk factor for soft tissue sarcoma distributed throughout
agriculture and forestry work was not responsible for the overall increase in
risk found in relation to phenoxyacetic acid exposure.
*Controls were matched individually to cases on the basis of these factors,
Unmatched analyses are presented in Table 40 for the sake of simplicity. The
matched-method relative risks for exposure to phenoxyacetic acids and/or
chlorophenols were 6.2 (90% confidence interval 3.4-11.2) in Study A and 5.1
(90% confidence interval 2.8-9.3) in Study B.
93
-------
supported by the occurrence of individual cases of soft-tissue of sarcoma,
usually a relatively rare form of cancer, in two cohort studies of workers
exposed to TCDD and trichlorophenol. Therefore, the studies provide a strong
suggestion that phenoxyacetic acid herbicides, chlorophenols, and/or TCDD are
carcinogenic in humans.
MALIGNANT LYMPHOMA
A separate series of clinical observations at the Department of Oncology in
Umea, Sweden (Hardell 1979) led the researchers to conduct a case-control study
of malignant lymphoma in relation to phenoxyacetic acids, chlorophenols, and
other organic compounds (Harden et al. 1980). Approximately one-third of the
cases in this study were patients with Hodgkin's disease; the remainder of the
lymphomas were non-Hodgkin's forms. MacMahon (1966) and, more recently,
Gutensohn and Cole (1980) have stated that late adult-onset Hodgkin's disease
and the other forms of lymphoma are likely to share similar etiologies.
This study employed essentially the same methods and achieved results
closely comparable to the soft tissue sarcoma studies: fivefold to sixfold
relative risks in relation to phenoxyacetic acids and chlorophenols considered
separately or together. In addition, an elevated relative risk was found in
connection with exposure to organic solvents such as benzene, trichloroethylene,
and styrene. In the published report, the methods and results were incompletely
documented, especially the possibility of confounding by exposure to the organic
solvents. The researchers indicate that an additional report of this study is
in preparation.
Other research has tentatively suggested that lumberjacks may be at
increased risk of lymphoma (Edling and Granstam 1980). In addition, the Zack
I
and Suskind study of workers exposed to TCDD found three deaths from cancers of
S5
-------
following a minimum period of cancer induction -- in this case, 10 years from
first exposure. The results are shown in Table 41. Expected deaths were
derived from Swedish national mortality rates specific for age, sex, and
calendar year.
TABLE 41. STOMACH CANCER MORTALITY IN A GROUP OF SWEDISH RAILROAD WORKERS
EXPOSED TO HERBICIDES, 10 OR MORE YEARS FROM ONSET OF EXPOSURE
Exposure
category
Phenoxy acids
Mini tro i e
Amitrole and
phenoxies
Stomach
Observed
2
n
1
cancer deaths
Expected
0.33
n ?n
U.£U
0.18
Relative
risk
6.1
5.6
90% confidence
interval
1.1-19.1
0.3-26.4
Source: Axel son et ai. (1980)
The estimate of relative risk of stomach cancer for workers with primary
exposure to phenoxyacetic acids, but not amitrole, is 6.1. Although this
estimate is based on small numbers, the one-tailed Poisson test suggests that it
is not likely to have arisen by chance alone (P = 0.044).
The group of all workers with exposure to the phenoxyacetic acids,
including those who also had amitrole exposure, had a relative risk of stomach
cancer of 5.9 (90% confidence interval 1.6-15.2, three observed stomach cancer
deaths, 0.51 expected).
The other study showing increased stomach cancer mortality is the follow-up
of 75 workers exposed to TCDD during and after a 1953 runaway reaction at a
trichlorophenol manufacturing facility in Ludwigshafen, Federal Republic of
-------
OTHER STUDIES
Four additional cohort studies have examined cancer mortality rates in
groups of workers exposed to phenoxyacetic acids and/or TCDD. These are a study
of Dow Chemical Company 2,4,5-T production workers (Ott et al. 1980), a study of
Finnish phenoxyacetic acid herbicide applicators (Riihimaki et al. 1978), and
two studies in which trichlorophenol production- workers were exposed to TCDD:
the previously mentioned Nitro study (Zack and Suskind 1980) and study of Do*
Chemical Company employees (Cook et al. 1980).
As noted above, the Mitro study showed a suggestive increase in lymphatic
and hematopoietic cancer mortality. In addition, the Nitro study and the study
by Cook et al. each included a single death from soft-tissue sarcoma.
The CAG has determined that three of these studies as evidenced by the
extremely small numbers of expected cancer deaths in each, have such low
statistical power that they cannot be taken as strong evidence of the absence of
increased carcinogenic risk in the groups of people studied. In the Nitro
study, 9.04 deaths from all malignant neoplasms and only 0.5 from stomach cancer
were expected. If the researchers had allowed for a minimum period of cancer
induction, these figures would have been even lower. In the study by Ott et
al., only 2.6 deaths from all malignant neoplasms were expected with allowance
for a 10-year minimum induction perod. The study by Cook et al., with only 1.6
expected deaths from all forms of cancer without allowance for a minimum
induction period, had the lowest chance of detecting an effect of all three
studies.
Statistically, the study of Finnish herbicide applicators is inconsistent
with the results of the Swedish and West German cohort studies. Without regard
for induction periods, this study reported 34.5 expected deaths from all
i
malignant neoplasms. The study, therefore, appears powerful enough to detect
99
-------
that exposure to 2,4,5-T and/or TCDD may also increase the risk of malignant
lymv oma and stomach cancer in hum is. Published studies that have not shown
increases cancer mortality among workers exposed to 2,4,5-T and/or TCDD have low
statistical power and, therefore, do not provide strongly contradictory
evidence.
101
-------
presently in use which conform to commonly accepted principles of chemistry and
biology would give risk estimates within this range, we feel that their
employment would not provide any additional useful information.
This risk assessment is based on two main elements: 1) a mathematical model
for extrapolation of animal to human dose-response was developed which can be
utilized to estimate risk given an average lifetime exposure to the herbicides,
and 2) estimates of the lifetime average exposure to various use patterns of the
herbicides were made.
The mathematical model is based on the rationale explained in the
"Carcinogen Assessment Group's Method for Determining the Unit Risk Estimate for
Air Pollutants," July 31, 1980 (Appendix G). All the experimental animal data
for 2,4,5-T and TCDD considered in the employment of the model are fully
explained and the results obtained are given in the next section.
The estimated human exposures from the use'Of these herbicides were supplied
to the CAG by the Hazard Evaluation Division (HED) of the Office of Pesticide
Programs of EPA and is attached as Appendix F. These estimates were used as
given except for the changing of units to mg/kg body wt/day, the appropriate
unit for the mathematical model. All of the qualifications, liabilities,
assumptions, and reservations about the exposure estimate expressed in the HED
document should be kept in mind in evaluating CAG's risk assessment since they
naturally apply to all situations where the exposure estimates are utilized.
Also, quantitative estimates of risk were made for only certain uses and
routes of exposure of commercial 2,4,5-T and silvex. The CAG's analysis is
confined to those situations where HED had sufficient information to generate an
exposure estimate.
Risks are estimated below for exposure to workers in forestry, range and
brush control, rice-weed control, on rights-of-way, and for exposure to the
general population and local populations through the diet by contaminated food.
103
-------
parameters of the multistage model, the upper bound linear component, and the
human linear component are all shown for each data set.
In Table 59, the final human slope estimate is given for each data set. The
maximum slope factor for all the data sets are 1.82 x 10'2 (mg/kg/day)'1 for
2,4,5-T and 4.25 x 1Q5 (mg/kg/day)'1 for TCDD which are used in the risk
estimation of all subsequent risk.
The slope for TCDD for 2,4,5-T spray applicators may be converted to be used
for exposure given in terms of 2,4,5-T by multiplying the assumed TCDD
contamination rate of 2,4,5-T, 4 x 10'8, by 4.25 x 10$, the slope for TCDD,
giving a value of 1.70 x 10~2 (mg/kg/day)'1.
Under these assumptions an estimate of the lifetime probability of cancer
for an applicator due to exposure to a lifetime average exposure of x mg/kg/day
of commercial 2,4,5-T is
where B]_ = is the maximum converted human slope for TCDD and 63 = is the
maximum human slope for 2,4,5-T alone, or
0.0182)x = i . e-0.0352x
For applicator exposure to silvex, the risk equation in that case is related
only to the TCDD contaminant
P = 1 - e-Bl x = i . e-0.017x
As discussed in detail in the exposure document, the TCDD contaminant of
both 2,4,5-T and silvex is assumed to be present at 40 ppb only for the sprayer
105
-------
Uses 2,4,5-T:Si1vex ratio
Range! and/pasture 10:1
Forestry 100:1
Rice 1000:1
Rights-of-way 10:1
FORESTRY
For forestry sprayers, risks based on measured exposure are shown in Table
60. Lavy gives the exposure as total dose based on the actual clearance of
2,4,5-T from 21 workers. Based on total hours exposed per year and total worker
population exposed and an assumed 40 year working life, a total lifetime
exposure was estimated and lifetime cancer risks have been extrapolated. The
upper limits on these lifetime risks range from 10"4 to 10" 3 with the
highest risk associated with the aerial mixer-loaders, 2.7 x 10~3. The small
number of workers exposed, however, results in a very small number of cases per
year, even under the assumption of a 40-year working lifetime. Furthermore, the
above analysis does not assume protective clothing.
RANGE AND BRUSH CONTROL
Based on estimated exposure for unprotected range sprayers, Table 61 shows
upper limits on lifetime risks of 10~6 to 10'4, with the highest risk of 1.7
x 10-4 to the mixer/loaders. With only 200 of-these estimated, however, the
estimated annual case rate is essentially 0. The risk to each of the 20,000
backpack sprayers is estimated to be 3.5 x 10~6.
RICE-WEED CONTROL
Based on the measured exposure from the forestry workers, adjusted for
application rates of the active ingredient 2,4,5-T, the estimated^! fetime risks
are presented in Table 61. These estimated risks for unprotected workers are
107
-------
2,4,5-T at a higher rate, up to the legal limit of 4 Ib/acre, both the residues
and associated risks would be correspondingly higher.
Based on the 4.2 ppt TCCD contamination level in beef fat and a beef
consumption of approximately 100 Ib/person/year, HED estimates that TCDD dietary
intake from beef for the general population is approximately 0.4 pg/day. For the
local population consuming only contaminated beef, dietary intake could be as
high as 31 pg TCDD/person/day assuming a 5-year treatment cycle.
Likewise, for milk contamination, assumption of 4.2 ppt TCDD in fat of
grazing cows would project to as much as 74 pg TCDD/day dietary intake for local
populations or for those consuming only contaminated dairy products.
Measurements of silvex in milk assumed similar for 2,4,5-T, yield exposure
estimates of 7.1 ng/kg/day 2,4,5-T for the local population.
Based on the above exposure estimates Table 62 shows that the upper limit
risk estimates for beef contamination at the above estimated exposures are
1.9 x 10-4 for -the local population and 2.4 x 10~6 for the general
population. For the general population this gives an upper limit number of
cases of 7.5/year. For milk and dairy products the upper limit risk estimate
for estimated exposures is 4.7 x 10"4 for the average consumer of only
contaminated products.
DEER AND ELK
HED has estimated the dietary intake from TCDD contaminated deer and elk
meat to be between 0.14-9.3 pg/kg/meal for deer and 0.05-20.5 pg/kg/meal for
elk. All consumption is assumed to be by the local population of hunters and
their families. The maximum projected risks based on 12 meals per year for life
are 1.3 x 10~4 for deer and 2.9 x 10'5 for elk. These are presented in
i
Table 63. More or less consumption would lead to corresponding increases or
decreases in risk.
109
-------
For contaminated deer and elk meat, risks to the local population are no greater
than 10~4 for 12 meals a year.
The upper limit of dietary risk associated with estimated exposure to
2,4,5-T in contaminated rice and milk were in the 10~7 range for a high
consumer eating only contaminated rice or an average consumer drinking only
contaminated milk.
Ill
-------
TABLE 43. DOW (DR. KOCIBA) TCDD ORAL RAT STUDY (1978) WITH DR. R. SQUIRE'S REVIEW
Female Sprague-Dawley Rats - Spartan Substraln (2 yrs.)a
FEMALES
Tissues and Diagnoses
0
[control)
Dose Levels (ug/kg/day)
0.001 0.01
0.1
Dow (Kociba) Analysis
1. Lung
Keratlnizing squamous
cell carcinoma 0/86
2. Nasal Turbinates/Hard Palate
Stratified squamous cell.
carcinoma (Revised diagnoses
2/19/79) 1/54
3. Liver
Hepatocellular hyperplastic
nodules/hepatocel1ular
carcinoma 9/86
0/50
0/49
0/30
3/50
1/27
18/50
(2 had both)
(P = 4.37 x 10-4)
7/49
(P = 6.21 x 10-4)
5/24
(P = 9.46 x 10-3)
34/48
(P = 9.53 x 10-13)
Total 1, 2, or 3 above
(each rat had at least
one tumor above)
9/86
3/50 18/50 34/49
(P = 4.37 x 10-4) (p = 2.13 x 10-12)
aAverage body weight of female rat = 450 grams.
(continued on following page)
-------
TABLE 44. NCI TCDD (GAVAGE) BIOASSAY (#80-1765)
Osborne-Mendel Rats (2 yrs.) W = 700 g
MALES3
Thyroid
Folllcular cell
adenoma carcinoma
Dose Levels (ug/kg/wk)
Tissues and Diagnoses
1. Adrenal
Cortical adenoma^
vehicle
control
0
6/72
low
0.01
9/50
(P = 0.093)
N.S.c
medium
0.05
12/49
(P = 0.015)
high
0.5
9/49
1/69
5/48
(P = 0.042)
8/50
(P = 0.004)
11/50
(P = 2.84 x ID'4)
^Subcutaneous combined fibroma or flbrosarcoma - not significant.
biological significance of this tumor in old age rats 1s questionable, since it is commonly
observed in control rats and is associated with the aging process.
CN.S. = Not significant.
-------
TABLE 46. NCI TCDD (GAVAGE) BIOASSAY (#80-1765)
B6C3F1 MICE (2 yrs.) W = 48 g
MALES
Tissue and Diagnosis
Liver
Hepatocellular
adenoma or carcinoma
vehicle
control
0
15/73
Dose Levels (ug/kg/wk)
low medium
0.01
12/49
0.05
13/49
high
0.5
27/50
(P = 1.31 x ID'4)
-------
TABLE 48. DOW (DR. KOCIBA) 2,4,5-T ORAL RAT STUDY (1978)WITH DR. SQUIRE'S REVIEW
Sprague-Dawley Rats - Spartan Substrain
MALES3
Dose Levels (mg/kg/day)
Tissue and Diagnosis
0 3 10 30
(control)
Dow (Dr. Kociba) Analysis
Tongue
Stratified squamous
cell carcinoma
1/83
1/50
0/46
(P
4/49
= 0.063)
Dr. R. Squire's Review
10 Tongue
Squamous cell carcinoma 1/83 1/50& 0/46& 5/48
(P = 0.025)
aAvjrage weight of male rat = 600 grams
bDr. Squire examined all slides from the middle and low dose described by Dow (original report) as
exhibiting any lesions, but did not review tongue slides that Dow described as having no lesions. The
incidence numbers for low and medium dose levels in this table represent this combined review incidence
(i.e., Dow's tongue diagnoses confirmed by Dr. Squire).
-------
TABLE 50. CURVE FIT OF THE MULTISTAGE MODEL PARAMETERS TO EXPERIMENTAL DATA BY STUDY AND PATHOLOGIST.
LINEAR PARAMETER ^, MAXIMIZED TO GIVE UPPER 95% LIMIT q*
Compound TCDD
Study Dow
Sex-species Male rat
Weight (wa) 600 gm
Tumor sites (one or more)....Nasal turbinates/hard palate - squamous cell carcinoma
Tongue - squamous cell carcinomas
Pathologist - Squire
Exposure Level (mg/kg/day) 0 1 x 10~6 1 x 10~5 1 x 10~4
+r/n 0/77 2/44 1/49 9/44
+r = number of animals with one or more of the tumors
n = total number of animals examined
_j
ro
EstimatedGoodness of fit
multistage parameters qo qi q2 qs qt X^
When all dose groups
are used 0.015 1.05 x 1Q3 0 109.40 x 109 3.53 x Ifl3 3.90 (d.f.=l)
When the highest dose
group is not used Above fit is satisfactory
When"the two highest dose
groups are not used
q? the maximum linear component from the model with adequate goodness of fit (P > 0.01) = 3.53 x
q* = q* (70/Wg)1/3 = 1.73 x 104, the upper 95% limit one-hit slope factor associated with
human dose response.
-------
TABLE 52. CURVE FIT OF THE MULTISTAGE MODEL PARAMETERS TO EXPERIMENTAL DATA BY STUDY AND PATHOLOGIST.
LINEAR PARAMETER ^, MAXIMIZED TO GIVE UPPER 95X LIMIT qf
Compound TCDD
Study Kociba - Dow
Sex-species Female rat
Weight (wa) 450 gm
Tumor sites (one or more)....Liver, lung, hard palate, or nasal tubinates
Pathologist - Squire
ro
CO
Exposure level (mg/kg/day(
0
1 x 10-6
1 x 10-5
When all dose groups
are used
0.26 1.25 x 104
0
0
1 x 10-4
+r/n
+r - number of anima
n = total number of
Estimated
multistage parameters
Is with
animal
qo
16/86
one or more of
s examined
0.01) =
q* = q* (70/Wg)1/3 = 4.25 x 105, the upper 95% limit one-hit slope factor associated with
human dose response.
'.90 x 104~
-------
TABLE 54. CURVE FIT OF THE MULTISTAGE MODEL PARAMETERS TO EXPERIMENTAL DATA BY STUDY AND PATHOLOGIST.
LINEAR PARAMETER qp MAXIMIZED TO GIVE UPPER 95% LIMIT qf
Compound JCDD
Study NCI
Sex-species Female rat
Weight (wa) 450 gm
Tumor sites (one or more)....Liver tumor
Pathologist - NCI Reviewed
Exposure level (mg/kg/day) 0
1.43 x 10~6
7.14 x 10"6
7.14 x 10~5
+r/n
5/75
1/49
3/50
14/49
+r = number of animals with one or more of the tumors
n = total number of animals examined
ro
tn
Estimated
multidtage parameters
12
Goodness of fit
When all dose groups
are used
0.05
0
5.65 x 107 0
6.09 x 103
1.44 (d.f.=2)
When the highest dose
group is not used
Above fit is satisfactory
When the two highest dose
groups are not used
q* the maximum linear component from the model with adequate goodness of fit (P < 0.01) = 6.09 x 103
q* = q* (70/Wj,)1/3 = 3.28 x 104, the upper 95% limit one-hit slope factor associated with
human dose response.
-------
TABLE 56. CURVE FIT OF THE MULTISTAGE MODEL PARAMETERS TO EXPERIMENTAL DATA BY STUDY AND PATHOLOGIST.
LINEAR PARAMETER ^, MAXIMIZED TO GIVE UPPER 95% LIMIT qf
Compound TCDD
Study NCI
Sex-species Female mice
Weight (wa) 40 gm
Tumor sites (one or more)....Subcutaneous tissue-fibrosarcoma, hematopoietic system lymphoma, or leukemia;
Liver-hepatocellular adenoma or carcinoma; Thyroid-follicular cell adenoma
Pathologist - NCI Reviewed
Exposure level (mg/kg/day) 0 5.71 x 10~6 2.86 x 10~5 2.86 x 10-4
+r/n 22/74 20/50 19/48 31/47
+r = number of animals with one or more of the tumors
n = total number of animals examined
EstimatedGoodness of fit
multistage parameters qg qi q2 93 qf X2
When all dose groups
are used 0.41 2.38 x 103 0 0 3.78 x 103 1:20 (d.f.=2)
When the highest dose
group is not used Above fit is satisfactory
When the two highest dose
groups are not used
q* the maximum linear component from the model with adequate goodnes of fit (P < 0.01) = 3.78 x 103
q* = q* (70/Wg,)1/3 = 4.56 x 104, the upper 95X limit one-hit slope factor associated with
human dose response.
-------
TABLE 58. CURVE FIT OF THE MULTISTAGE MODEL PARAMETERS TO EXPERIMENTAL DATA BY STUDY AND PATHOLOGIST.
LINEAR PARAMETER q^ MAXIMIZED TO GIVE UPPER 95% LIMIT qf
Compound 2,4,5-T
Study Dow
Sex-species Male rats
Weight (wa) 600 gm
Tumor sites (one or more)....Tongue
Pathologist - Squire
Exposure level (mg/kg/day)
10
30
+r/n
1/83
1/50
0/46
5/48
+r = number of animals with one or more of the tumors
n = total number of animals examined
Estimated
multistage parameters qg
Goodness of fit
X2
Ql
q2
When all dose groups
are used
0.01
3.51 x 10~6 3.72 x ID'3
Ot94 (d.f.=2)
When the highest dose
group is not used
Above fit is satisfactory
When the two highest dose
groups are not used
(\i the maximum linear component from the model with adequate goodness of fit (P < O.OT) = 3.72 x 10"
q* = q* (70/Wg)1/3 = 1.82 x 10'2, the upper 95% limit one-hit slope factor associated with
hOman dose response.
-------
TABLE 60. LIFETIME PROBABILITY OF INDUCED CANCER FOR 2,4,5-T AND SILVEX APPLICATORS BASED ON
2,4,5-T MEASURED EXPOSURE3 CALCULATED ON AN HOURLY BASIS
CO
Use pattern Exposed group Dose average
(number mg/kg/hr^
for 2,4,5-Tb) 2,4,5-T
(hrs/yr)
RiskC
mg/kg/day Lifetime
Lifetime 2,4,5-T
2,4,5-T (pure)
Risk<*
Lifetime
based on
TCDD
Total
Lifetime Average
risk cases/yre
commerical Total
(2,4,5-T) 2,4,5-T plus
contaminant
Forestry
1. Aerial
2.
Ground broad-
cast
a. Tractor
mistblower
b. Backpack
sprayer
aCompared to
Pilots (73)
Mixer/Loaders
(73-145)
Supervisors (--)
Fl aggers ( — )
Mixer/Loaders (180)
Driver (90)
Supervisor ( — )
Applicator (300)
Mixer- supervisor
0.015(200)
0.062(800)
0.004(800)
0.003(800)
0.020(480)
0.013(240)
0.006(480)
0.021(800)
0.003(800)
4.6
7.6
4.9
3.7
1.5
4.8
4.4
2.6
3.7
x ID'3
x ID'2
x ID'3
x 1C-3
x 10-2
x 10-3
x 10-3
x 10-2
x 10-3
skin absorption, potential exposure through
8.4 x
1.4 x
9.0 x
6.7 x
2.7 x
8.7 x
8.1 x
4.7 x
6.7 x
105
10-3
10-5
TO-5
io-4
10-5
10-5
io-4
10-5
the lungs was
7.8 x
1.3 x
8.4 x
6.3 x
2.5 x
8.2 x
7.5 x
4.4 x
6.3 x
10-5
ID-3
10-5
IO-5
io-4
10-5
10-5
io-4
10-5
considered
1.6 x
2.7 x
1.7 x
1.3 x
5.2 x
1.7 x
1.6 x
9.1 x
1.3 x
negligibly
silvex
lO'4 <10-3
10-3 o.06
io-4
io-4
10~4 0.001
10-4 <10-3
io-4
IO-4 0.004
10-4
small by Lavy1 s
measurements.
^Figures from HED (Appendix F) .
1
mg/kg/year for
40 years = 40 year
Numbers exposed for silvex given
x 1 life
71.3 years
x 1
36b
year
days
= 1.54 x
in text.
io-5
mg/kg/day 1
ifetime.
4 5-T Slooe = 1 82 XrlQ"2 (mg/kg/day)-1, from Table 59.
ito. Slope = 4.25'x 105 (mg/kg/day)-r, from Table 59. This risk is for the TCDD contaminant of both 2,4,5-T
and silvex.
eTotal expected cases 2,4,5-T plus silvex divided by 71.3.
-------
TABLE 61. (continued)
U>
CJ
Use pattern
Rights-of-way
1. Aerial
2. Ground
a. Selective
Basal
b. Cut
Stump
c. Mixed
Brush
d. Railroad
e. -Electric
Power
Exposed group Dose average
(number for mg/kg/hr
2,4,5-T) 2,4,5-T
(hrs/yr)
Pilots (25)
Mixer/loaders
(25-50)
Applicators
(1380)
Applicators (60)
Handgun
applicators (270)
Truck/Boom
applicators (180)
Crew (of four)
(110)
Applicators (400)
0.060(400)
0.240(400)
0.084(1,000)
0.053(500)
0.079(660)
0.005(660)
0.066(260)
0.080(660)
mg/kg/day
Lifetime
2,4,5-T
3.7
1.5
1.3
4.1
8.0
5.1
2.6
8.1
x 10-2
x 10-1
x 10-1
x 10-2
x lO-2
x lO-3
x 10-2
x 10-2
Risk
Lifetime
2,4,5-T
(pure)
6.7
2.7
2.3
7.4
1.5
9.2
4.8
1.5
x ID'4
x 10-3
x 10-3
x 10~4
x ID'3
x 10-5
x 10-4
x 10-3
Total
Risk Lifetime Average
Lifetime risk cases/yr
based commerical Total
on TCDD 2,4,5-T 2,4,5-T plus
contaminant silvex
6.3
2.5
2.2
6.9
1.4
8.6
4.5
1.4
x lO'4
x 10-3
x 10-3
x 10-4
x 10"3
x 10~5
x 10~4
x 10-3
1.3
4.8
4.5
1.4
'
2.9
1.8
9.3
2.9
x 10-3
x 10-3
x 10-3
x 10-3
x 10~3
x 10-4
x 10-4
x 10-3
<10-3
O.D04
0.091
0.001
0.005
<10-3
0.002
0.017
See notes on previous tables.
-------
TABLE 63. ESTIMATED INTAKE OF TCDD FROM CONTAMINATION OF DEER AND ELK MEAT
BY ANIMALS FORAGING ON 2,4,5-T TREATED LAND
ALSO, ESTIMATED LIFETIME CANCER RISKS
Deer Elk
Dietary intake
pg/kg bw/day for one meal 0.14 - 9.3 0.05 - 20.5
Assumed meals/year* 12 12
Equivalent daily dose
pg/kg/bw/day 0.0046 - 0.3058 0.0016 - 0.6740
Estimated risk 2.0xlQ-6-1.3xlO-4 6.8xlQ-7-2.9xlO-5
*For higher or lower consumption, the risk will vary proportionately.
135
-------
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Berry, D.L., J. DiGiovanni, M.R. Jachau, W.M. Bracken, G.L. Gleason, and T.J.
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chemicals in a two-stage mouse skin. Tumorigenesis Assay. Res. Com. in
Chem. Path, and Pharmacol. 20(1):101-108.
Berry, D.L., T.J. Slaga, T. DiGiovanni, and M.R. Jachau. 1979. Studies with
chlorinated dibenzo-p-dioxins, polybrominated biphenyls and polychlorinated
biphenyls in a two-stage sustem of mouse skin tumorigenesis: potent
anti-carcinogenic effects. Ann. NI.Y. Acad. Sci. 320:405-414.
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chemicals. I. Carcinogenic study. Prepared for the National Cancer
Institute. (Innes et al. 1979 publication is abstracted from this report).
Bleiberg, J., M. Wallen, R. Brodkin, and I. Applebaum. 1964. Industrially
acquired porphyria. Archives for Dermatology 89:793-797.
Carter, C.D., R.D. Kimbrough, J.A. Liddle, R.E. Cline, M.M. Zack, W.R. Barthel,
R.E. Koehler, and P.E. Philips. 1975. Tetrachlorodibenzodioxin: an
accidental poisoning episode in horse arena.. Science 188:738-740.
Clement Associates. May 15, 1979. Exposure, toxicity, and risk assessment of
2,4,5-T/TCDD. Prepared for EPA under contract no. 68-01-5095.
Cohen, G.M., N.M. Bracken, R.P. Iyer, D.L. Berry, J.K. Selkirn, and J.J. Slaga.
1979. Anti-carcinogenic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on
benzo(a)pyrene and 7,12-dimethylbenz(a)anthracene tumor initiation and its
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137
-------
Goodman, D.G., 1980. Histopathologic tables concerning The Dow Chemical Company
2,4,5-T and TCDD studies.
Grant, W. 1979. The genotoxic effects of 2,4,5-T. Mutat. Res. 65:83-119.
Green, S. 1975. Cytogenetic evaluation of several dioxins in the rat.
14th Annual Meeting Society of Toxicology. March 9-13, 1975.
Green, S., F. Moreland, and C. Sheu. May 1977. Cytogenetic effect of
2,3,7,8-tetrachlorodibenzo-p-dioxin on rat bpne marrow cells. FDA By-Lines.
6:292-294.
Guenthner, T.M., J.M. Fysh, and D.W. Nebert. 1979.
2,3,7,8-tetrachlorodibenzo-p-dioxin: Covalent binding of reactive metabolic
intermediates principally to protein in vitro. Pharmacology 19:12-22.
Gupta, B.N., J.G. Vos, J.A. Moore, J.G. Zinkl, and B.C. Bullock. 1973.
Pathological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in laboratory
animals. Environ. Health Perspect. 5:125-140.
Gutensohn, N. and P. Cole. 1980. Epidemiology of Hodgkin's disease. Sem.
Oncol. 7:92-102.
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toxicity of 2,4-dichlorophenoxy acetic acid in rats. Toxicol. Appl.
Pharmacol. 20:122-129.
Hardell, L. 1977. Malignant mesenchymal tumors and exposure to phenoxyacids: a
clinical observation. Lakartidningen 74:2753-2754 (translation).
Hardell, L. 1979. Malignant lymphoma of histiocytic type and exposure to
phenoxyacetic acids or chlorophenols. Lancet 1:55-56.
Harden, L., and A. Sandstrom. 1979. Case-control study: soft-tissue sarcomas
and exposure to phenoxyacetic acids or chlorophenols. Br. J. Cancer
39:711-717.
Hardell, L., M. Eriksson, and P. Lenner. 1980. Malignant lymphoma and exposure
to chemical substances, especially organic solvents, chlorophenols, and
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Hay, A. 1976. Seveso: the aftermath. Nature 263:538-540.
Hook, G.E., J.R. Haseman, and G.W. Lucier. 1975.
2,3,7,8-tetrachlorodibenzo-p-dioxin induced changes in the hydroxylation of
biphenyl by rat liver microsomes. Pharmacol. 24:335-340.
Hussain, S., L. Ehrenberg, G. Lofroth, and T. Gejvall. 1972. Mutagenic
effects of TCDD on bacterial systems. Ambio. 1:32-33.
139
-------
Kouri, R.E. 1976. Relationship between levels of aryl hydrocarbon hydroxylase
activity and susceptability to 3-methylcholanthrene and benzota]
pyrene-induced cancers in inbred strains of mice. C rcinogenesis 1:139-151.
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I.S. Owens, and D.W. Nebert. 1978. 2,3,7,8-tetrachlorodibenzo-p-dioxin as
a cocarcinogen causing 3-methylcholanthrene-initiated subcutaneous tumors in
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Leuschner, F., A. Lueschner, F. Hubscher, W. Dontenwill, and P.V. Rogulja.
Apr. 9, 1979. Chronic oral toxicity of 2,4,5-T. Batch No. 503, Control No.
153574 b. called for short - 2,4,5-T in Sprague-Dawley (SIV 50) rats.
Laboratorium Fur Pharmakologie und Toxikologie.
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dibenzodioxin. Br. J. Ind. Med. 30:276-283.
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Amer. J. Epidemic!. 103:226.
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National Cancer Institute. 1980a. Bioassay of 2,3,7,8-tetrachlorodibenzo-p-
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Bethesda, MD.
141
-------
Rasmuson, B., and H. Svahlin. 1978. Mutagenicity tests of 2,4-dlchlorophenoxy
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27:190-192.
Reggiani, G. 1977. Medical problems raised by the TCDD contamination in
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Occupational Health in the Chemical Industry. Sept. 5-10, 1977.
Renner, H.W. 1979. Monitoring of genetic environmental risk with new
mutagenicity tests. Ecotoxicology and environmental safety 3:122-125.
Riihimaki, V., S. Asp, A.M. Seppalainen, and S. Hernberg. 1978.
Symptomatology, morbidity, and mortality of experience of chlorinated
phenoxy acid herbicide (2,4-B; 2,4,5-T) sprayers in Finland. A clinical and
epidemiological study. Working paper for an IARC working group meeting on
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Jan. 10-11, 1978.
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The fate of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) following single or
repeated oral doses to rats. Toxicol. Appl. Pharmacol. 36:209-226.
Rothman, K.J. and J.D. Boice. 1979. Epidemiologic analysis with a programmable
calculator. Bethesda, Maryland: National Institute of Health, NIH
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Rowe, V.K., and T.A. Hymas. 1954. Summary of toxicological information on
2,4-D and 2,4,5-T type herbicides and an evaluation of the hazards to
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Emerson, and C.G. Gerrbig. 1973. Toxicity of chlorinated
dibenzo-p-dioxins. Environ. Health Perspect. 5:87-98.
Seller, J. 1973. A survey on the mutagenicity of various pesticides.
Experientia 29:622-623.
Thiess, A.M., and R. Frentzel-Beyme. 1977. Mortality study of persons exposed
to dioxin following an accident which occurred in the BASF on 13 November
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press).
Thigpen, J.E., R.E. Faitt, E.E. McConnell, and J.A. Moore. 1975. Increased
susceptibility to bacterial infections as a sequelae of exposure to
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Infection and Immunity
12:19-1324.
Toth, K., S. Somfai-Relle, J. Sugar, J. Bence. 1979. Carcinogenic!ty testing
of herbicide 2,4,5-trichlorophenoxy ethanol containing dioxin and of pure
dioxin in Swiss mice. ,
143
-------
APPENDIX A
TABLE III-7. CUMULATIVE MORTALITY OF MALE RATS
(KOCIBA ET AL. 1977)
ug/kg/day TCDD
Time (end of 30-day period) N=
1-7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Controls
(86),
0.0
0.0
0.0
0.0
2.3
5.8
7.0
10.5
12.8
16.3
18.6
24.4
31.4
41.9
48.8
58.1
69.8
77.9
82.6
0.1
(50)
0.0
2.0
4.0
4.0
4.0
8.0
12.0
18.0
18.0
20.0
28.0
34.0
44.0
46.0
62.0
74.0*
78.0
84.0
90.0
0.01
(50)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
4.0
14.0
22.0
28.0
34.0
46.0
54.0
68.0
76.0*
84.0
88.0
92.0
0.001
(50)
2.0
2.0
2.0
2.0
2.0
2.0
2.0
4.0
14.0
14.0
24.0
44.0*
50.0
56.0
60.0
68.0
74.0
76.0
78.0
*Interval of greatest difference, D, in cumulative mortality curves of
controls and treatment group. None of the differences were statistically
significant (Kolmogorov-Smirnov test, P > 0.05).
A-l
-------
TABLE II1-9. MALES: INTERVAL MORTALITY RATES
Days
40-30
31-210
211-240
241-270
271-300
301-330
331-360
391-420
421-450
451-480
481-510
Control
d/1
0/86
0/86
0/86
0/86
0/86
2/86
3/84
3/80
2/77
3/75
2/72
rate
0.000
0.000
0.000
0.000
0.000
. 0.023
0.036
0.038
0.026
0.040
0.028
0.1 ug/kg/day
d/1
0/50
0/50
1/50
1/49
0/48
0/48
2/48
3/44
0/41
1/41
4/40
rate
0.000
0.000
0.020
0.020
0.000
0.000
0.042
0.068
0.000
0.024
0.100
0.01 ug/kg/day
d/1
0/50
0/50
0/50
0/50
0/50
0/50
0/50
2/50
5/48
4/43
3/39
rate
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.040
0.104
0.093
0.077
0.001 ug/kg/day
d/1
1/50
0/49
0/49
0/49
0/49
0/49
0/49
/
1/49
5/48
0/43
5/43
rate
0.020
0.000
0.000
0.000
0.000
0.000
0.000
0.020
0.104
0.000
0.116
(continued on following page)
-------
TABLE 111-10. FEMALES: INTERVAL MORTALITY RATES
>
Days
0-150
151-180
181-240
241-270
271-300
i
331-360
361-390
391-420
421-450
451-480
481-510
511-540
Control
d/1
0/86
1/86
0/85
0/85
0/85
0/85
0/85
2/85
0/83
3/83
5/80
2/75
3/73
rate
0.000
0.012
0.000
0.000
0.000
0.000
0.000
0.024
0.000
0.036
0.063
0.027
0.041
0.1
d/1
0/50
0/50
0/50
1/50
1/49
2/48
4/46
2/42
3/40
1/37
2/36
3/34
3/31
ug/kg/day
rate
0.000
0.000
0.000
0.020
0.020
0.042
0.087
0.048
0.075
0.027
0.056
0.088
0.097
0.01
d/1
0/50
0/50
0/50
0/50
1/50
0/49
1/49
0/48
2/48
2/46
3/44
0/41
1/41
ug/kg/day
rate
0.000
0.000
0.000
0.000
0.020
0.000
0.020
0.000
0.042
0.044
0.068
0.000
0.024
0.001
d/1
0/50
0/50
0/50
0/50
0/50
0/50
, 2/50
0/48
1/48
2/47
1/45
3/44
2/41
ug/kg/day
rate
0.000
0.000
0.000
0.000
0.000
0.000
0.040
0.000
O.O'I
0.043
0.022
0.068
0.049
(continued on following page)
-------
Preliminary Report
APPENDIX B
PATHOLOGIC EVALUATIONS OF SELECTED TISSUES FROM
THE DOW CHEMICAL TCDD & 2,4,5-T RAT STUDIES
Submitted to
Cancer Assessment Group
The Environmental Protection Agency
Washington, DC 20460
August 15, 1980
Robert A. Squire Associates, Inc.
1515 LaBelle Avenue
Ruxton, Maryland 21204
B-l
-------
DOW 2.^.5-T CHRONIC TOXICTTY STUDY IN MALE RATS
TUMOR INCIDENCE SUMMARY TABLE
CONTROL LEVEL HIGH DOSE LET/EL
INTEGUMENTARY SYSTEM
Skin/Subcutis»
Fibroma J/86 3/50
Carcinoma 1/86 1/50
Lipsarcoma 1/50
Malignant Fibrous Histiocytoma 2/86
Calcifying Epithelioma 1/86
Squamous Cell Papilloma 2/86 1/50
Squamous Cell Carcinoma 1/86
HEMATOPOISTIC SYSTEM
Lymph node:
Carcinoma, metastatic 1/50
Lymphoma 1/50
Malignant Schwannoma, metastatic 1/86
C-cell Carcinoma, metastatic 1/86
Thymus:
Malignant Schwannoma, metastatic 1/51
Spleen:
Lymphoma 1/86
Multi sites:
Lymphona 2/86
CIRCULATORY SYSTEM
Heart:
Endocardial Sarcoma 1/50
B-3
-------
1U1
DOW 2.4,5-T CHRONIC TOXICITY STUDY IN MALE RATS
TUMOR INCIDENCE SUMMARY TABLE
ENDOCRINE SYSTEM
Pituitary
NERVOUS SYSTEM
Brain:
CONTROL LEVEL HIGH DOSE LEVEL
Chromophobe Adenoma 15/80 9/49
Chromophobe Carcinoma 7/80 2/49
Adrenal:
Pheochromocytoma 37/84 19/49
Cortical Adenoma 8/84 7/49
Cortical Carcinoma 1/84
Ganglloneuroma 1/49
Thyroid:
C-cell Adenoma 4/85 6/47
C-cell Carcinoma 2/85
Parathyroid:
Chief Cell Adenoma 1/43
REPRODUCTIVE SYSTEM
Testes:
Interstitial Cell Tumor 2/86
Mammary Gland:
•
Adenocarcinoma 1/50
Fibroadenoma 1/86 1/50
Astrocytoma 1/86 1/50
Granular Cell Tumor 1/50
Cranial Nerve:
Schwannoma 1/86
B-S
-------
'5
-.1
"i
i
£'•*
ROBERT \. SQU1PJE ASSOCIATES, INC.
1515 Lcf-elle Avenue
Ruxlon, //orylcnd 21204
(301)821-0054
-August 26, i960
Er. Bernard Habamaa :_ ;
Cancer Ascecsnsrit Grcup
Office- of Heeith and 2r.vironnental
Assessasr.t.
U.S. Eavlrcr^ental Protectijan Agency
Washiaeton, 2C 20^60-
Dear Dr. K^isr
As p^er C*JT s-grsensr.t, KB examined tissues £rcs only the
control and high dcse ordinals fron the Dow 2,^,5-T two year
rat study. Sir.ca finding the ons additional carcinoma in ths
ton/jus of ths high dose nale, however, I did exaains tongues
froa aJ.l _xLe= in all dose groups in which there ware any
pathologic alterations reported "by Dow patholoj-ists, Ky
fir. din ^agreed >d.th thcca of DOK pr.tholcgists in thit I
found no additional nooplaso^s aaong ths slides examined.
Sincerely,
Robort A. Squire,
Ph.D.
cot Richard E
RAS/ek
'' j
,v
B-7
-------
APPENDIX C
ABORATOR1UM FUR PHARM AKOLOGIE UND TOX1KOLOC,:
PROFESSOR no r. LOUSCIINI K
COPY
D-2104 Hamburg 92, January 17th, 1980
Mr.J.Guy Gwynne
Consul
Amerikanisches Generalkonsulat
Handelsabteilung
Alsterufer 27
D-2000 Hamburg 36
Dear Mr. Gwynna,
today I am allowed to answer to the questions which arose
with the telex from EPA, referring to 'The Chronic Oral Toxicity
of 2,4,5-T, batch No. 403, control No. 1535746 - called for short
'2,4,5-T' - in Sprague-Dawley (S1V 50) Rats with special attention
to Carcinogenic Properties' as follows:
A) 2,4,5-T (untreated rnt:;) 2,4,5-T (ficetono-t rc.n ed
rats)
fibroma (thorax) 1 female none
fibroma (abdomen) 2 males none
1 female
fib-roma (uterus) none 1
fibroma (mamma) none 1 female
fibroma (limb) none- 1 male
interstitial cell
tumour = testes 22 animals 6 niiinwls
A1 - A4) Historical (untreated control rats, no further cxporietife
with acetone-treated animals; all historical studies 2 to
3 years before examinations with 2,4,5-T)
•
A1) adenofibroma
(mamma) 6 of 50 females
interstitial cell
tumour (testes) 20 of 50 animals
A2) fibroma (limb) 3 males and 1 females of each 90 animals
interstitial cell
tumour 24 of 90 animals
- 2 -
' C-l
ANSCHR1PT: PRANCOPER STR. 6«b • D-3104 H-\ M B U R C 92 (N E U G R A D E N) . T EUCPO N : (0401 701 SO 21 . 23 . 7362^35
EXPRESSGUTSTATIO;-: HAM DU n C-UAK nu RG
* »*" f i"*>wTn. HAMBURGER SPAHK ASSP ini.7. son ins io> . KONTO.NR.
-------
•j -
D) The tongue was examined n-.te rosco-pic.:,' 1 ly together with larynx jn
pharynx. These investigar'\>ns did .I»L show pnt ho logical changes
therefore no histologica i i-:-:anui:.il i o-is were carried out. Siri.it
muscular tissue was take" from sKo] <.-;:al muscle.
E) The diet was analyzed for 2,/»,5-!-?tability at 6 dates and tue
results were as follows:
Date
19.07.76
30.11.77
6.03.78
1
i 29.05.78
i 30.08.78
Dosage
nig/kg
b.w.
3
10
30
3
10
30
3
10
30
3
10
30
3
10
30 .
3
10
30
Nominal
"4e>
32
112
299
47
165
6 SO
48
168
430
48
103
460
48
160
480
48
160
480
value Actual va
/kg standardised diet
33
11.5
340
45.6
167. H
496.0
42.9
152.6
435.5
47.8
168.2
440. 1
45.8
139.3
434.9
48.7
164.1)
516.0
25.10.78
F) Mortality rates 2,4,5-T (mean value of males plus females)
untreated rats = 75% acetone-treated rats = 71%
FI-
FA) Historical Mortality rates (F1-F4 = analogue to A1-A4)
untreated rats
F1) 71%
F2) 64%
F3) 75%
F4) 70%
i
G) The authors will give the permittance for these examinations.
Please ask the sponsor for his agreement, this is not yet ;it. hand
We hope that you got complete informations on all points out of the
telex of EPA and remain at vpur disposal for further informations.
With kind regards .
-------
APPENDIX D
LABORATORIUM FUR PHARMAKOLOGIE UND T OXIKOLOGIE
PROFESSOR DR. t. LEUSCHNER
HISTOPATHOLOGICAL EXAMINATIONS IN THE TONGUE
Appendix to
'Chronic oral Toxicity of 2,4,5-T, batch no. 503,
control no. 153574 b - called "2,4,5-T" - in
Sprague-Dawley(SIV 50) rats'
(date of final report: April 9th, 1979)
- with special attention to carcinogenic properties -
Senior Pathologist:
Prof.Dr.med.W.Dontenwill
August 6th, 1980
D-l
FJLANCOPER SIR. S8b • D-2I04 HAMBURG 93 (N EUGRAB ENJ • TELBPONi (0«| 701 iO 21 • 23 • 798 23 25
-------
- 2 -
Apart from these two findings no changes could be seen. The
variation of the epithelial thickness was, as normal, more
marked at the basis of the tongue. A semiquantitative compari-
son did not show signs for demonstrated hyperplasia. No dys-
plasia, papilloma or carcinoma were found.
D-3
-------
LABORATORIUM FUR PHARMAKOLO GIE UNO TOXIKOLOGIE
PROFESSOR OH. t. LEUSCHNER
QUALITY ASSURANCE STATEMENT
Based on a quality assurance review, it was concluded that this
report accurately reflects the data for the
'Histopathological Examination in the Tongue'
Appendix to: Chronic oral Toxicity of 2,4,5-T,
batch no. 503, control, no. 153574 b - called
"2,4,5-T" - in Sprague-Dawley(SIV 50) rats
(date of final report: April 9th, 1979)
- with special attention to carcinogenic properties -
Approved and
Franz Htibscher Date
Director of QAU
D-5
FRANCOPER STR. S«b • D-2104 HAMBURG 92 (NEUCRABEN) • TELEFONi (040) 7015011-23 • 79« 15 :j
-------
APPENDIX E
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
OFFICE OF
RESEARCH AND DEVELOPMENT
SUBJECT: Clarification of Telephone Convservation with Dr. Leuschner
FROM: Wade Richardson ••U/l'Jt- /• f&d^c,L^
Office of Health and Environmental Assessment (RD-689)
TO: Charalingayya Hiremath, Ph.D.
Carcinogen Assessment Group (RD-689)
In early August, at CAG's request, I made an overseas telephone call to
Dr. Leuschner in Germany and asked if he would be willing to cut histological
sections of the tongues from male rats in his two year chronic toxicity stuay
on 2,4,5-T. I first indicated that the Agency preferred that horizontal
sections be cut. However, when Dr. Leuschner expressed preference to cut
longitudinal sections, I indicated to him that I would again discuss with the
appropriate people in the Agency how they felt the sections should be cut and
then call him back to confirm the nature of the Agency's request. Due to some
misunderstanding, it appears that longitudinal sections had already been cut
by the time I called Dr. Leuschner back confirming the Agency's wish that
horizontal sections be cut.
E-l
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APPENDIX F
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
3ATE September 12, 1980
SL;E.,ECT Exposure Assessment for 2,4,5-T, Silvex and TCDd
"cv Acting Chief, Environmental Fate Branch, HED
~° Elizabeth Anderson
Carcinogen Assessment Group (RD-683)
Attached is the Exposure Assessment for 2,4,5-T, silvex and TCDD,
David J. Severn, Ph.D.
cc: P. E. McGrath
F-l
EPA Form 1320-6 (Rev. 3-76)
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QUANTITATIVE ASSESSMENT OF EXPOSURE TO 2,4,5-T, SILVEX AND TCDD
INTRODUCTION
As part of its risk-benefit balancing procedures, the
Agency generally attempts to estimate potential human exposure to
pesticides in quantitative terms. The ultimate objective of these
assessments is to develop numerical estimates of the amount of
exposure that certain segments of the population may experience
as a result of pesticide use. These exposure data are combined
with toxicity information to generate an overall risk assessment.
The risk assessments are then used to predict potential health
effects based on the toxicologic effects of the pesticide in
question.
This document provides some quantitative estimates of exposure
to 2,4,5-T, silvex, and TCDD for use in the cancellation hearings.
These estimates are based as far as possible on observed residue
levels in the environment. However, while these estimates are
expressed as numerical values, they are in fact much less precise
than their numerical nature would imply. This is because the
available data are meager, because conditions (spray techniques,
weather, etc.) are so variable, and because many assumptions have
to be utilized in order to arrive at the estimates. This intro-
duction describes some of the reservations which apply to the
numerical estimates presented in this assessment, and comments on
the limitations on the use and interpretations of this information.
F-3
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-iii-
treated and other indicators of the probable extent of contam-
ination are subject to many uncertainties- In particular, the
numerical values for the populations at risk are highly uncertain.
This is because information on population demographics, whether
or not related to pesticide use, is not well developed.
The uncertainties described above are common, in varying
degrees, to all exposure assessments, including these assess-
ments for 2,4,5-T, silvex and TCDD. In sum, although Agency
scientists have a high degree of confidence about much of the
empirical data which form the basis for this analysis, they are
far less confident about other information. The quantitative
exposure estimates for the populations at risk are limited by
these uncertainties.
Exposure Analysis
The starting point for exposure assessment for pesticides
is descriptive information on pesticide release and distribution
to the different environmental compartments such as air, water,
soil, and animal and plant tissues during application. In
addition, 2,4,5-T and silvex are known to move from sites of
application to non-target areas under some conditions of
application.
This qualitative information on potential sources of human
exposure is supported by analytical chemical data showing that
residues of these chemicals are present subsequent to application,
F-5
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-V-
Even when some data are available for one kind of application,
there may be uncertainty as to whether those data are applicable
to other applications which may occur under different conditions.
For example, residue data collected during springtime application
in the Pacific Northwest may not properly describe the amount
and distribution of chemicals under different environmental
conditions at a different time of the year. Often, the only data
available are data derived from laboratory studies, with little
or no field data to verify that the laboratory data accurately
describe the residue levels which might be present under field
conditions.
Further, each of the several different human exposure
pathways provides a different kind of exposure potential. Even
when some empirical residue data on a given route of exposure
are available, there are often uncertainties concerning the
generalization of those data to other routes of exposure. These
uncertainties are a particular concern when estimating exposure
to chemicals such as TCDD which appear to pose risks at very low
levels of exposure.
In attempting to generalize to "average" or "typical" use
patterns, the Agency has encountered a wide variety of practices,
which were very difficult to address. An example is the appli-
cation rate to be used when rangeland vegetation is spot treated.
Despite the fact that the USDA-EPA States Report (Ref. 2) notes a
F-7
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-Vll-
The exposures which have been quantified in this document
are as follows:**/
1) Occupational exposure to 2,4,5-T, silvex, and TCDD.
2) Dietary exposure of the general population and local
populations to TCDD residues in beef and local populations to
TCDD residues in dairy products resulting from the use of
2,4,5-T and silvex on rangeland and pasture.
3) Dietary exposure of local populations to TCDD residues
in deer and elk resulting from the forestry use of 2,4,5-T and
silvex.
4) Dietary exposure of the general population and local
population to silvex residues in rice, apples, pears, prunes,
and sugar (from sugarcane) resulting from the use of silvex on
these food products.
5) Dietary exposure of the general population and local
populations to 2,4,5-T and/or silvex residues in rice resulting
from the use of 2,4,5-T and silvex on rice.
Finally, the available data relating to some uses of 2,4,5-T
and silvex are inadequate even to begin assessing potential
human exposure. For some situations, no monitoring information is
known to the Agency, and in other situations the available data
**/ The Agency is still evaluating and generating monitoring
da"ta which were not utilized in these quantitative assessments.
The Agency may utilize these data as they are developed.
F-9
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- 1 -
ESTIMATION OF OCCUPATIONAL EXPOSUPE TO 2,4,5-T, SILVEX, AND TOD
Introduction
This analysis provides a quantitative human exposure V estimate for
2,4,5-T, silvex, and dioxin in terms of absorption by the body of these
chemicals under normal agricultural working conditions.
Human exposure estimates are made on the basis of chemical analyses of
dermal and inhaled concentrations of the chemical or chemicals, and if
the information is available, on the basis of the amount of chemical(s)
or their metabolites excreted by the body (e.g. in the urine). **/
In the case of the pesticides and contaminant under consideration, there
are experimental data available on the occupational exposure to pesticide
applicators and farmworkers applying 2,4,5-T under actual use conditions.
These data consist of dermal, inhalation, and urinary concentrations of
2,4,5-T obtained from the field application of 2,4,5-T in forestry and
rice***. Exposures to 2,4,5,-T frcm other uses and to silvex and TCDD for
all uses were estimated by extrapolation and will be discussed below.
The term "exposure", as used in this paper, refers to the amount of
chemical absorbed by the body.
**
During the past four years, since the initiation of the RPAR process,
the Hazard Evaluation Division has estimated occupational exposures
to many pesticides. In some cases data on dermal and inhalation
exposure were available for these estimates. In other cases, these
data had not been generated, necessitating extrapolations from infor-
mation on other pesticides (with similar application techniques) for
purposes of the exposure estimate.
*** Experimental data of the type required for this analysis were found
only for 2,4,5-T. Consequently, exposure to silvex and TCDD was calcu-
lated on the basis of extrapolations frcm the 2,4,5-T data as explained
in the text.
F-ll
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- 3 -
T«o ether studies reported in the literature V provided confirmatory
information en 2,4,5-T absorption by humans.
The information enabling us to estimate the absorption of 2,4,5-7 by occu-
paticnally exposed individuals is contained in the field study conducted
by Lavy on fbresty applicators (Kefs .14,15). The study was designed to
measure 2,4,5-T exposure to pesticide vorkers applying this pesticide
in the forest by three different methods:
a aerial (helicopter)
0 ground application by tractor-driven mist blower •
* ground application by backpack sprayers
Twenty-one individuals (including two females) participated in this study.
The subjects were engaged in normal pesticide application activities (e.g.
piloting a helicopter: driving a tractor and handling pesticide application
equipment; mixing pesticides by dilution, etc.) A cannercial product con-
taining 2,4,5-T Ssteron5, was applied at day "0" at a rate of 2 Ibs a.e./A*
* ShafiX et al. (Ref.24) report an average of 2.4 me 2,4,5-T/l of urine
in 5 spray operators engaged in 2,4,5-T application. Jfo spray history or
total excretion is given, so it is iirrcssible to calculate total ex-
posure from this experiment. As a matter of fact, the purpose of the
reported study was to develop analytical methodology rather than measure
exposure.
Simpson et al. (Ref.25), in a very brief summary paper, reported urinary
levels of 2,4,5-T in pesticide applicators handling this herbicide rang-
ing fron 0.160 mg/1 to 1.740 mg/1. These incomplete results make it
inpossible to calculate total body burden from 2,4,5-T exposure.
a.e. - acid ecuivalent.
F-13
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- 5 -
.. .absorbed, since urinary excretion nay not be complete at termination
of the experiment, riowever, calculation of the absorbed dose of 2,4,5-T
based on phacziacokinetic analysis... is not dependent en total excretion
and can, therefore, provide a more realistic estimate of the absorbed
dose." Ramsey et al. have chosen maxirnun estimated doses of 2,4,5-T
obtained from three different kinetic equations (Ref.19, p. 20).
>fe have used Ramsey's adjusted data based on Lavy's study (Sefs.14,15) in
estimating occupational exposure. Results for forestry application of
2,4,5-T are tabulated in the last colunn of Table 1, giving the average
experimental dose expressed as mg/kg body weight/hour. From Tables 2-A
and 3-A it may be seen that seme individual values varied widely. For
example, the ranges for pilots were 0.005 - 0.024 mg/kg/hour and backpack
applicators, 0.009 - 0.036 mg/kg/hcur.
Lavy (Refs.14,15) provides experimental data only for forestry uses of
2,4,5-T. Therefore, exposure estimates for uses on rice, rangeland,
pasture, and rights-of-way were calculated by comparing application rates,
occupations, ani application techniques with the corresponding figures in
forestry use, assuming that exposure would be directly proportional to the
application rate. It was further assumed that the difference in applica-
tion rate was the only variable factor which would result in differences
of applicator exposure for each type of occupational group. For example,
the rate used for aerial application of 2,4,5-T in range and pasture is
F-15
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- 7 -
TABLE 1
Estimated Sxrcsure of Pesticide Arolicators
and Farmworkers to 2,4,5-T
Estimated
Use Pattern
Application
Execsed GrcuD Rate1 (Ib/A)
No. Exposed Exposure*-
Persons1 (hrs/yr)
Averace
Exscsure^
(zc/kc/hr)
TOHESTKf
1.
2.
1.
2.
Aerial
Ground Broadcast
a. Tractor
Mistblcwer
b. Backpack
Sprayer
Aerial
Ground Backpack
Aerial
Pilots
Mixer /Loaders
Flaggers
Supervisors
Mixer/Loader
2
2
2
2
2
Tractor/operator/vorker 2
Supervisor
Applicators
Mixer/ Supervisor
RANGE
Pilots
Mixer /Loaders
Flaggers
Applicators
Pilots
Mixer /Loader
Flaggers
2
1.6
1.6
AND PASTURE
1.0
1.0
1.0
0.6
RICE
1.0
1.0
1.0
73
73-145
___ 3
3
90-133
90
3
300
3
130
130-260
800
20,000
307
307
6500-9500
200
800
800
830
483
240
480
830
330
75
100
25
83
12
43
0.6
RIGHTS-OF-War
1.
Aerial
Pilots
Mixer /Loaders
3.0
8.0
25
25-50
400
400
0.015
0.062
0.003
0.004
0.020
0.013
0.006
0.021
0.005
0.0084
0.0314
0.0024
0.0084
O.OOS4
0.0304
0.0024
0.0604
0.2404
2. Ground
a. Selective
b. Cut Stump
c. Mixed Brush
d. teilroad
e. Electric
Power
Applicators (hand) • 6.4
Basal
Applicators (hand) 4.0
Applicators (hand) 6.0
Truck boon Applicators 0.8
Crew of Four 5.(avg)
Applicators (hand)
S.(avg)
1383
60
273
178
114
400
1000
530
660
660
264
66O
0.0 S44
0.0 S34
0.0794
0.0054
0.0664
0.0834
1. See Table 1-A
2. Reference 19. Calculated dose levelsr received by EPA on February 14, 1979;
* 16? [30,000/26]; See also Table 2-A for raw data.
3. ( ) indicates that the number of individuals cannot be estimated.
4. These values were extrapolated as explained in the text.
F-17
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- 9 -
prudent to review these experimental studies and kinetic derivations in
greater detail. Curing the cross examination testimony of Dr. Nisbet,
several experimental deficiencies in the Lavy studies (Refs.14,IS) were
discussed and included apparently incomplete or variable urine collect-
ion and failure to correct urine volumes according to creatinine levels.
The Agency is presently engaged in an independent analysis of the pharra-
cokinetic treatment of Lavy's field data. After this review has been
completed, the exposure estimates nay have to be revised appropriately.
KCLMODIN-HEEMAN STLTY
Recently, another study fron Sweden on the exposure of two tractor crews
to 2,4,5-7 has cone to cur attention (Pef.13). The study consisted of
the surveillance of t>o work crews of 2 individuals each. They applied a
ircurture of phenoxy herbicides in a forest for one work week and 2-4 hrs/
day spraying time using a Qullvik* ftorest Tractor equipped with a fan
sprayer. 31cod and urine samples were analyzed before application of
the herbicide, once or twice during the application period, and at 12, 24,
and 36 hours after the last application. Urine samples were not taken
at regular intervals during the study, making it less reliable for the
estimation of total exposure than Lavy's study (Refs.14,15). Lavy showed
that even a 6 day period is insufficient for ccnplete elimination of 2,4,5-T
fron the body. Thus, it is quite certain that Rslncdin' s results are en
* The ;rake of the Swedish tractor is mentioned because the difference in
exposure between Swedish and U.S. workers may be due to equipment differences.
F-19
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- 11 -
The exposure by Grew II in Kclrodin's study appears to be 3 to 6 tines
higher than that of Crew I. The reason fcr this nay possibly be explair.ec
by the different working conditions during pesticide application by
Crews I and II. Crew I changed work clothes each evening and their tractor
had a partially protected seat. Cn the other hand, the mixer/worker of
Crew II only charged his shirt in the middle of the week. Also, the tractor
for Crew II had a completely open seat. In addition, the mixer/vorker for
Crew II, \»ho also performed the job of rcw leader, cculd have received
spray each time the tractor turned, as cculd the tractor driver, depending
en the direction of the wind. Table 3 summarizes and compares the results
of the exposure to 2,4,5-T of the two work crews in Kblncdin's study.
TABLE 3
EXPOSURE TO 2,4,5-T*
Crew - kg Spray time Total mg me/kg
No. Ferscn Cccuoaticn BW (hrs/dav) excreted * mg/kg-5W SW/h**
I
II
KK
LJ
IZO
JG
Mixer/worker
Tractor Driver
Mixer/worker
Tractor Driver
70
80
75
62
2-4
2-4
2^
2-4
hours
hours
hours
hours
9.
30
8.85
36
57
.0
.75
0.
0.
o.
0.
13
11
48
93
0.
0.
0.
0.
01
01
03
06
Appropriate: 2-3 kg Al/ha (equivalent to about 2 Ib/A) 330 g/liter 2,4-D and
170 g/liter 2,4,5-T. This calculates to about 0.66 Ib./A 2,4,5-T
CrSW I Jeans, shirt; changed work clothes before evening meal.
Tractor has partially protected seat. The sprayed areas
were marked by KK.
CHEW II Jeans and shirt; ISO was the mixer and changed shirt once.
JG was the tractor driver. LEO was "row leader." (A perscn
who marks the row to direct tractor-driver). When the tractor
turned, he cculd get spray liquid on his body. Tractor driver
cculd also receive spray on his body, since tractor had a
completely open seat.
* Peference 13.
** Based on 1.5 L urine/day; see Table 2 for tabulations. '
*** Average 3x5 =15 hrs/week spray time.
F-21
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- 13 -
2. We are not av^re of any information regarding the rate of cerral
absorption by nan of TCDD relative to 2,4, 5-T. In the absence of
this information, v« are assuming for the purpose of estiisating
exposure that TCDD and 2,4,5-T are absorbed at the same rate.*
3. TCDD exposure resulting fron 2,4, 5-T application nay be estimated
by applying concentration factors obtained by direct analysis of
2,4, 5-T formulations. Lavy reported that TCDD v«es present in
the Esteron* product used in his study (Kefs. 14,15) at a level
of 0.04 pom (4 x lO"9). Manufacturer's voluntary specifications
of current 2,4,5-T production claim TCBD concentrations of 0.1 ppm
or less.** Thus, TCDD exposure may be estimated by multiplying
2,4, 5-T exposure for each applicator group by a factor ranging
from 4 x 10"3 to 1 x lO"7.***
4. Estimates for number of exposed individuals and annual hours of
exposure due to silvex use can be made by using conversion
factors based on ratios of 2,4,5-T treated acres to silvex treated
acres for different uses as shown in Table 5; these ratios range
fron 1/10 to 1/1000.
* Another assumption is that the concentration of TCDD relative to
2,4,5-T does not change fron the time it is formulated until it is
deposited on the skin of the occupation*lly exposed personnel.
** There are some manufacturers v»ho claim that their 2,4,5-T products
contain 0.02 ppm or even less dioxin.
*** Since the concentrations of TCDD in 2,4,5-T and silvex are approx-
imately the same, the same factors may be used in estimating ex-
posure to TCDD resulting fron silvex applications. The same number
of persons exposed to 2,4,5-T or silvex are, therefore, assumed to be
exposed to TCDD. Moreover, the annual hours of exposure of a person
to 2,4,5-T and/or silvex are assumed to be the same as his annual
hours of exposure to TCDD.
F-23
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-15-
each type of applicator would increase by a factor of SCO over cur estimate
of total number of annual exposure hours estimated to occur at the time of
suspension.
Similar projections for increase in total number of exposure T-curs to
either 2.4,5-T, silvex, or TCDD might be made if the extent of use of
2,4,5-T or silvex approached the maximum possible market for commercial
forest land (factor = 500), rice land (factor of 10), or rights-of-<*ay
(factor • 200) (ref. 17).
SIM4ARY OF OCCUPATIONAL EXPOSURE
Based on the Lavy study, which measured 2,4,5-T levels in the urine of
applicators who applied 2,4,5-^T, as veil as on a pharmacckinetic analysis
by Ramsey of these experimental data, we have estijrated applicator exposure
to 2,4,5-T, silvex and TCDD resulting from a number of uses of 2,4, 5-T
and silvex. These estimates are provided in Table 1.
Because of several factors, the exposure estimates made in this document
are subject to considerable uncertainty. Some of the more important factors
are:
1. It is possible that the degree of care to avoid exposure which
was exercised by the applicators in the Lavy study may not be typical
of that used in routine 2,4,5-T or silvex applications.
2. The applications in the Lavy study were conducted under essentially
windless conditions and on relatively level terrain. At higher
wind velocities or different terrain (roll- j hills or mountains)
exposure rares may be quite different
3. In estimating TCDD exposure, it was necessary to extrapolate
from data - 2,4,5-T exposure. In so doing, it was assumed that
TCDD was t ;rbed by the body with an efficiency equal to that
of 2,4,5-T. In fact, TCDD may be absorbed at rates considerably
different than those of 2,4,5-T.
F-25
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- 17 -
ESTIMATES CF KLMAN sxpcsuas TO BEEF AND MILK
Mi^R.T£D wns TCDD
BACXGCUND
The estimates of human exposure to TCDD from contaminated beef and railX
which are developed in this document are based on a two-oart study (here-
after called phase one and phase two, respectively) initiated under the
Dicxin Implementation Plan in 1975. These studies were designed to deter-
mine possible residues of TCDD in the fat and livers of cattle grazing on
range land treated with 2,4,5-T (ref.26).
Animals from selected farms in Missouri, Kansas, Texas and Oklahoma were
taken to commercial slaughter houses, where samples of fat and liver were
collected. Alcng with historical information, these samples were forward-
ed to the Toxicant Analysis Center, at Bay St. Icuis, Mississippi, for
extraction, cleanup, and encoding, preparatory to chemical analysis for
tetrachlorodibenzo-p-dioxin (TCDD) by various analytical collaborators
(ref.26).
The phase one samples were taken in FebruaryAiarch, 1975, and the phase
two samples in November/ December, 1975, fron cattle grazing on forage
treated with 2,4,5-T in May, 1974 and May,. 1975, respectively. In both
parts of the study, the application rates varied from farm to farm, rang-
ing from 1/2 to 4 Ib 2,4,5-T active ingredient/A (3 Ib/A maximum applic-
ation rate in phase two). In addition, the percentage of acreage actu-
ally treated varied from 20% to 100%.
Agricultural practices appear to have been about the same as those in
use today. Herbicide (2,4,5-T) was aerially applied (with occasional
ground spot -treatment) to control undesirable vegetation on grazing
F-27
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- 19 -
There is also the possibility that the dioxin residues in these fat samples
might not be representative of the residues in all cattle allowed to graze
on 2,4,5-T-treated land. Since this study contains the most reliable
field data currently available, however, it is assumed that these residues
are representative of the residues which would result from typical
2,4,5-T-use on range land in the United States. Further, it is reasonable
to extend the conclusions regarding 2,4,5-T use to the use of silvex on
pasture land, since the use practices for the two herbicides are very
similar, and both contain comparable amounts of TCDD.
Another uncertainty concerns the amount of treated vegetation actually
ingested by the exposed cattle. Since the percentage of 2,4,5-T-treated
grazing lands varied widely from farm to farm (from 20% to 100%), cattle
might have had the opportunity of ingesting differing percentages of
both treated and untreated vegetation, depending upon the grazing acreage
in which they were allowed to feed. Since the exact situation on each
farm is unknown, it is assumed that 100% of the diet of these cattle
consisted of contaminated vegetation, that is, cattle fed selectively
on the treated areas, rather than grazed indiscriminately, and consumed
no supplementary (uncontaminated) feed or forage. This assumption was
made because there appears to be a better correlation between average
application rate and average residue levels when it is assumed that
animals grazed solely on treated vegetation, rather than on both treated
and untreated vegetation.
It is therefore assumed that the dietary intake of forage in the cattle
frcm this study consisted of only treated forage. If these cattle.actually
ingested significant quantities of forage from untreated areas, or supple-
mented their diets with uncontaminated feed or grain, then it is highly
F-29
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- 21 -
corrections were made to the data sunmarized in Tables A-4 or A-5.
The preliminary results of phase two are sunmarized in the Table A-5.
However, these data have been included for comparison only and will
not be incorporated into the dietary estimate because only two samples
were taken from animals grazing on land treated at the highest applica-
tion rate (3 Ib./acre). Residues of TCDD found in the adipose tissues
of these cattle ranged from ND(limits of detection ranging from 7 to 14
ppt) to 34 ppt in the 2 Ib/A group, but were all nondetected in the 3/4
Ib/A group (with limits of detection of 7-14 ppt). Although of a preli-
minary nature, these results are of the same order of magnitude as those
found in phase one.
ASSIGNED RESIDUE VALUES
Since many of the positive samples tended to occur at levels just above
the limit of detection of current methodology (especially in the cattle
from farms treated at the lower application rates), it is likely that the
samples reported as containing no detectable TCDD actually contained TCDD
residues, at or below the level of detection. Therefore, some assumptions
were made in order to deal with these kinds of results.
Residues were detected in a majority of the samples in the 3 Ib/A group.
This strongly suggests that the ND samples of this set may have contained
residues at, or very close to the limit of detection.
Average residue values were estimated from the results in Table A-4 by
averaging the test results for each sample, as follows:
a. Only samples which satisfy the criteria used by the Dioxin Moni-
toring Program (Table A-7) have been included in the calculations.
F-31
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- 23 -
seems reasonable to assign values equal to the limit of detection to the
"non-detected" samples in this group.
Using the average residue values (which include the assigned positive
values for "ND" test results) we find a strong correlation between the
rate of applied 2,4,5-T (dosage) and the TCDD residues found in the beef
fat. These data are summarized in Table 6. A similar correlation has
been observed by Jensen, et al_. (ref .10) in a study where cattle were fed
forage which had been contaminated with various amounts of 2,4,5-T (con-
taining unspecified, but presumably the same, concentration of TCDD). The
observed level of TCDD residues in the adipose tissue appeared to be
directly proportional to the added 2,4,5-T in the daily diet. Based on
Jensen's observations, it seems reasonable to expect that the level of
TCDD in adipose tissues resulting from ingestion of forage contaminated
with 2,4,5-T or silvex (and consequently TCDD) would be directly proport-
ional to the rate of application of 2,4,5-T or silvex to that forage.
Therefore, it seems reasonable to assign residue values (to samples
which did not have detectable TCDD residues) in some proportion to
the amount of 2,4,5-T or silvex used on the forage fed to the cattle.
The sensitivity of the method for each particular sample must also be
taken into account. Since about 70% of the samples from the 3 Ib/A rate
showed measurable residues, all ND samples were reported as positive at
the level of sensitivity. Samples from fields treated at lower rates
were scaled down proportionally (see footnote on page 22).
Finally, Young (ref.32), Zweig (ref.33), and others have observed that
the development of increasingly sensitive methods of analysis have
permitted detection of residues at continually lower levels, where few
F-33
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- 25 -
measurable levels for long periods of time (half-life of 1 year or
longer), at or near the soil surface, as shown by Young (ref.32), and
Kearney (ref.ll) and others. These observations suggest that roots
(subthatch) and upper layers of soil in range land and pastures treated
with either 2,4,5-T or silvex may constitute a significant reservoir
for the TCDD consumed by grazing animals. Thus TCDD residues, either in
soil or on vegetation, may account for residues observed to occur in
beef animals grazing on 2,4,5-T -treated range land and pasture.
DIETARY INTAKE OF CONTAMINATED BEEF
The reported usage of 2,4,5-T on range land and pasture (ref.2) varies
between 1/4 and 2 Ib/A, depending on the area of the country, the
target vegetation, and other parameters. Rangeland uses of 2,4,5-T are
sutrnarized in Table 7. In phase one of the beef study, application of
2,4,5-T on some of the farms studied exceeded these rates (up to 4 Ib/A)
This raises the possibility that some grazing land is treated at levels
considerably higher than the levels reported in Reference 2.
Table 7
Summary of 2,4,5-T-Treated Rangeland*
Method of Target Application
Application Vegetation Rate (Ib/A)
Aerial
Aerial
Aerial
Aerial
Ground
Ground
Mesquite/shinnery oak
Mesquite/shinnery oak
Mesquite/shinnery oak
Oak Savannah
Mesquite
Oak Savannah
1
1/2
1/4
2
1/2
2
Acres Treated
Per Year
137,000
500,000
400,000
541,000
75,000
60 ,000
Total Rangeland Treated Annually 1,713,000
* Data from Tables 17 and 18, reference 2.
Using the data from Table 7, the weighted mean application rate was
calculated and found to be 1 Ib/A. This represents an "average"' use
F-35
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- 27 -
e. The percentage of home slaughter beef is estimated .o be about
0.9%.
f. Therefore, total beef consumed from home slaughter, raised on
tr ted land is...
80-137 million Ibs. x 0.009 = 720,000 to 1,230,000 Ibs.
g. Since about 720,000 to 1,230,000 pounds of contaminated beef could
be consumed at an average rate of 100 Ibs/person/year, it is
estimated that between 7,200 and 12,300 persons might consune
only contaminated beef (containing 4.2 ppt TCDD in the adipose
tissues).
Beef, consumed at 100 Ibs/person/year is equivalent to 124 grams/person/
day (approximately 1/3 pound). Assuming beef to contain about 15%
(Ref. 18b) fat, a typical daily intake would be about 19 grams of conta-
minated fat. Based on 4.2 ppt of TCDD residues in beef adipose tissue
resulting from the application of 1-lb/A 2,4,5-T to rangeland, an average
intake of 90 pg TCDD/person/day would be predicted, assuming all beef to
be contaminated. This number represents the dietary intake by a population
whose total beef intake was contaminated (hone slaughter). Exposure to
local populations would be expected to be proportionally higher, if
higher rates of application were used (labels permit treatment up to
4 Ib/acre).
The average intake of TCDD by local populations consuming TCDD-
contaminated beef would be expected to be about 80 pg/person/day during
the first year following application of 2,4,5-T or silvex to grazing
lands at 1 Ib/A. Reference 2 reports retreatment no more frequently than
once every 5 years. Since it is known that TCDD declines in soil with
a half-life of at least one year (Ref. 11, 32) cattle could reasonably
Based on data provided by Schmitt (ref.23), dietary intake of beef,
liver and veal would be about 112 grams/day, which agrees well with
Lee's data (ref.17), which is based on more recent information.
F-37
-------
- 27b -
The following is an estimate >f the dietary intake by the U.S. population
at large of TCDD from contaminated beef. As shown under "d" above, the
estimated volume of beef from animals grazing on 2,4,5-T or silvex-treated
areas ranges from 80 to 137 million pounds dressed weight. The total U.S.
production of beef is estimated to be 21.4 billion pounds. Thus, the
total amount of contaminated beef produced in any one year is estimated
to range from 0.4 to 0.6% of the total U.S. beef production*. The
dietary exposure of the general population to TCDD from contaminated
beef, therefore, is estimated to range from 0.3 to 0.5 pg TCDD/day.
It should be noted that only a very small percentage of grazing land is
treated annually with 2,4,5-T or silvex. If the use of these herbicides
were to increase, residues in grazing cattle might reasonably be expected
to increase proportionately.
INTAKE OF TCDD FROM OCOTAMINATED MILK
We have no information on whether or not it is valid to estimate possible
residues of TCDD in the milk of dairy cattle, extrapolated from the TCDD
residues in the adipose tissues of beef cattle. It is unclear whether
These estimates are based on the amount of beef cattle produced
on grazing land treated with 2,4,5-T or silvex during one
calendar year. However, if the assumption that cattle acquire TCDD
residues by ingestion of contaminated soil is correct, then the real
possibility exists that cattle could continually ingest quantities
of TCDD over many years. Thus, the total amount of contaminated beef
produced annually might be considerably higher than these figures.
This is especially true in light of the very long half life of TCDD
in soil and low soil mobility which \vould tend to ensure continued
dosing of grazing cattle for a number of years following herbicide
application.
If 2,4,5-T or silvex were to be used on all grazing land, to the max-
imum extent permitted by the label, (which is highly unlikely) intake
of TCDD could be expected to increase to 60 - 100 pg/day (200 x 0.3
to 200 x 0 .5 pg TCDD/day).
F-39
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- 29 -
cattle could be expected to contain about 0.17 ppt TCDD*. If the typical
dietary intake of dairy products** consists entirely of TCDD-contaminated
milk and milk products (containing about 43 grams of fat), then the level
of TCDD would then be 190 pg TCDD/day from these dairy products. Exposure
to local populations would be expected to be proportionally higher, if
higher application rates were used***.
DISCUSSION MD CONCLUSIONS
Assuming recent usage patterns for 2,4,5-T and silvex, the general popu-
lation would be expected to consume approximately 0.5 pg TCDD/day from
contaminated beef. Local populations (i.e. home slaughterers) whose
dietary consumption of beef consists of only contaminated beef are estim-
ated to consume 80 pg TCDD/day, on the average. Although difficult
to identify, there may be local populations whose dietary consumption
of milk and dairy products consists only of contaminated milk and dairy-
products. Tnis group is estimated to consume up to about 200 pg TCDD/day.
There might, theoretically, be local populations consuming only contamin-
ated beef and only contaminated milk and dairy products. They are estim-
ated to consume about 300 pg TCDD/day. Levels of 300 pg TCDD/day might
be reached for the general population if all range land and/or all past-
ures were treated with 2,4,5-T or silvex. However, this scenario is
highly unlikely.
* 4.2 ppt TCDD (Table A) x 0.04 = 0.17 ppt TCDD
** Schmitt (ref.23) estimates the daily intake of Milk and Dairy Products
to be about 550 grams, equivalent to about 43 gm of fat. See Table
5-A for computation.
u**
The label permits application of 2,4,5-T at rates up to 4 lb//A.
F-41
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- 31 -
into account, one would tend-to underestimate the exposure to the general
population.
Another factor which should be noted is the camion practice*
of fattening calves and yearlings in feeding lots prior to slaughter.
Ingestion of presumably uncontaminated forage and/or grain might tend
to dilute residues of TCDD in the adipose tissues. The exact pharma-
cokinetic mechanisms which apply here are unknown. Since none of the
animals in this study were sent to feed lots, their residues were not
diluted by this subsequent feeding. Not taking this factor into account
would tend to overestimate the exposure.
We are aware of the fact that a significant number of beef cattle
avoid the feedlots and are sent directly to slaughter. Therefore,
dioxin in the meat of these animals would not become diluted by
addition of non-contaminated fat. An example of this practice is
a local product, Giant Lean. We do not have any data on hand indicating
the percentage of beef cattle which are in this category.
F-43
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- 33 -
sented by this particular item of food. The food factor is ba *3 on the
average food intake of 1.5 kg per day by an 18-year old U.S. IT. ie.
If the percentage of food crops sprayed were to increase, the exposure of
the general population to 2,4,5-T and silvex residues in these crops would
increase proportionately. For purposes of setting an upper limit, estimates
of potential exposure have also been made for the hypothetical situation
in which 2,4,5-T and silvex are used to the permissible maximum acreage
on food crop, consistent with the pesticide labeling. Although it seems
unlikely that 2,4,5-T and silvex would be used to the maximum extent
permissible, unforeseeable factors could markedly change current usage
patterns so that at least an intermediate exposure might occur.
Exposure to residues of silvex and 2,4,5-T in secondary sources (meat,
milk, and eggs) may occur as a result of livestock feeding on treated
grasslands and rice by-products such as hay, straw, and hulls and poultry
feeding on rice by-products. In addition, exposure to silvex and 2,4,5-T
residues in fish may occur as a result of run-off from rice fields treated
with these herbicides. A quantitative estimate of exposure to 2,4,5-T
and silvex residues in milk and other dairy products has been made for
special situations. Although a quantitative evaluation of the exposure
to silvex and 2,4,5-T residues via other secondary sources cannot be
made at this time, a qualitative discussion follows in a later section.
5ILVEX RESIDUES IN THE HUMAN DIET
The results of the dietary analysis for silvex are given in Tables 8 and
9. Table 8 gives a range for the dietary intake by the general population
estimated frcm residues actually found on the treated crops (where known),
F-45
-------
- 35 -
Table 9 provides a range for the dietary intake by the general population
in the hypothetical situation of maximal treatrjent of the crops consistent
with the labeling. This situation, although highly unlikely, gives an
estijaated maximum level of dietary exposure from presently registered
uses of silvex.
TABLE 9
MBOMJM ESTIMATED DETATCf EXPOSURE TO SILVEX
Possible^ Percent? Focc^- Rate of Dietary
Residues Crop Factor Ingestion Exposure
Crop (pcb) Treated (%) (Go/day) (nc/kg SW/dav)
Rice
Sugar
Plums
Apples
12-100
100
100
42-100
100
243
12
100
0.55 0
3.64
0.13
2.54 1
Total:
.10^3.82
1.31
0.023
.60-3. 8L
43.3-35.2
1.42-11.71
18.72
0.334
22.86-54.43
ng/kg HW/day
1 Data from Table 8.
2. Figures represent maxirxm acreage treatable consistent with the
labeling. Estimates for sugar and plums utilized information
provided in Hef. 17.
3. U.S. Production of cane sugar (1977-1979) =2.6 million short tons.
Total sugar consumption = 11 million short tons, cane and beet sugar,
Ref. 34
The raaxiCTjn treatable crops are 100% of all U.S. grown rice, sugar cane,
and apples, but only 12% of plums (including prunes), and 1D% of pears.
•
Of all plums (including prunes) only Italian prunes are listed on the
pesticide label treatment with silvex, representing 12% of all plums
grown in the U.S. Silvex may be used only on Anjou pears, correspond ing
to 10% of all pears grown in the U.S. The dietary exposure estimates
shown in Table 9 might also represent the levels of exposure under
recent use practices for certain local populations which could conceivably
consume exclusively contaminated foods of each of the four types considered.
F-47
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- 37 -
DIETARY SCPOSvJRS F3CM PII^
Table 9 reflects the feet that only sane plans (Italian prunes) are
treated with silvex, accounting for the fact that the maximm treatable
crop is only 12% (the percent of total U.S. plan production consisting
of Italian plans). Based on our review of current EPA files it dees net
appear that analyses of silvex residues on plans or prunes have been
performed. We, therefore, assume that residues may be present at the
interim tolerance of 0.1 ppn.
DIETARY INTAKE FROM PEARS
Silvex is applied to Anjou pears trees after harvest. Therefore,
any residues of silvex appear in the following years crop. The Agency
has no record of silvex analyses on pears. Based on the post-harvest
use pattern, we do not believe that a strong possibility exists for
silvex residues to occur in pears and have, therefore, excluded pears
Iran the dietary exposure estimate.
DIETARY EXPOSURE FROM APPLES
Vfe are aware of a study dealing with treatment of apples with silvex
(Ref. 6) In this study, Mclntcsh apples were treated on the tree with
a 20 pan solution of silvex (according to label instructions) and were
analyzed for silvex residues at different daily intervals up to harvest
time, after 2 weeks storage, and 4 months' storage (Ref .6). The following
results were obtained.
Silvex Silvex Residues
Residues* After Storage for...
At Harvest 2 weeks 4 ncnths
Unwashed apples 32 ppb 42 ppb 35 ppb
Washed apples 27 ppb 26 ppb 16 ppb
* 14 days after last application
F-49
-------
- 39 -
In order to translate these data to possible silvex residues in milk from
cows grazing on treated pastures, a study by Bjerke, et al. (Ref. 4) proved
helpful.
Bjerke, et al. (Ref. 4) showed that feeding milk cows 1000 ppm of silvex
in their daily feed resulted in an average of 100 ppb residues of silvex
in the milk at steady state.
If we assume, therefore, that the environmental fate of silvex and 2,4,5-T
are similar, we can use the data of Bovey and Baur (Ref. 5) to estimate
(by interpolation) the amount of 2,4,5-T, and, therefore, silvex residues,
which vjould remain on treated grass 1 week after the last application
(There is a 1 week restriction of dairy animals entering silvex-treated
pastures). This value of 50 ppm of silvex in feed, is equivalent to about
5 ppb (0.005 ppm) of silvex residues in milk, based on an extrapolation
of experimental data (Ref. 4). This extrapolated value is below the
sensitivity of the method (0.05 ppm). The average male ingests about 500
g of milk and dairy products (ref.23) per day, expressed as of fluid
mil)-. At 5 ppb in the milk, therefore, a person consuming only milk
from dairy animals grazing on pastures recently treated with silvex
would ingest 2.5 ug of silvex daily.
2,4,5-T DIETARY EXPOSURE
There are potentially two major sources of dietary intake of 2,4,5-T
from food:
1) the direct application of 2,4,5-T to rice
2) indirect exposure from meat, milk, poultry, and eggs derived from
chicken and livestock fed on contaminated feed.
Beef and dairy cattle may graze on rangeland and pasture that has
I
been treated with 2,4,5-T. This possibility is exemplified by the obser-
F-51
-------
- 41 -
similar half-lives), we may estimate the following dietary exposure to
2,4,5-T for the general population frcm the si1vex data on contaminated
rice:
Possible residue: 12 ppb
Percent crop annually treated: 10.9% (Jtef.17)
Food Factor: 0.55(Ref,23)
Estimated Rate of Ingestion: 0.011 ug/day/person
Therefore, the estimated dietary exposure, based on recent usage patterns
would be 0.154 ng/kg/day, based on 70 kg body weight.
If the hypothetical, but highly unlikely, situation case may be considered,
in which all rice is treated with 2,4,5-T, the dietary exposure of the
general population would increase to 1.40 ng/kg/day. This might also
represent the exposure for certain limited populations which might
eat contaminated rice exclusively.
We might also consider the possibility that certain ethnic groups could
eat up to 10 times as much rice as the general population and might,
therefore, be exposed to between 1.5 and 14 ng/kg/day, a ten-fold
increase in exposure.
F-53
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- 42 -
The program in the Northwest was coordinated by Michael Watson, a toxicol-
ogist with EPA's Region X office. Dr. Watson anlisted the assistance of
Mr. Feade Brown (Chief, Game Management, Washington Department of Game,
Olympia, Washington) and Mr. Jerry MacLeod (Biologist, Oregon Department
of Fish and Wildlife, Portland, Oregon) who supervised the sample collect-
ion and quality assurance (Refs.29,30)
Dr. Watson provided the appropriate sampling protocol to be used; in
addition, he supplied all necessary equipment (which had been rigorously
cleaned in the laboratory to avoid precontamination with dioxins), so
that the deer and elk adipose tissues could be reliably sampled. Complete
capture records were required for each sarrple.
Following their collection, the adipose tissue samples were frozen within
24 hours, shipped to Dr. Watson under refrigeration and held in deep
freeze for approximately one year (until 11l\4/78). At that time they
were shipped to the EPA Toxicant Analysis Center, in Bay St. Louis,
F-55
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- 44 -
Table 11
ScnitErv of Deer and SIX Data3
ReDortecb TCDD - ccc
Animal
deer
deer
deer
elk
elk
elk
elk
elk
TAC *
WA-D-1
WA-D-4
WA-3-8
WA-S-2
WA-S-4
WA-2-5
WA-S-7
WA-S-8
RT?
SD(2)C
HEP
7*
9
21
12
SDd
54
WSJ
ND^
NA
!JA
21
ND^
NDd
63
Animal
deer
deer
deer
elk
elk
elk
elk
Rercrted0 TCD - cot
TAC *
OR-0-1
CR-D-5
CR-D-6
OR-S-7
OR-^-8
OR-2-9
OR-2-11
RTP
SD(4)
12
7
24
4
5
SD(2)
WSJ
vffid
31 «
14
29
SID (10)
ND(8)
ND(8)
3D Not Detected(see Table A-7 for DIP Criteria)
NA Not Analyzed due to limited amount of sample.
a. rtef.l.
b. Corrected for recovery losses
c. Parenthetic values are limits of detection for the analysis.
d. Recoveries below 50%. Saroles to be rerun.
TAC » Toxicant Analysis Center (EPA Lab. in Bay St. Louis, MS)
RTP = EPA Lab at Research Triangle Park, M.C.
VJSU » Wright State University, Dayton, OH
The results of the analyses of the Washington elk indicated much higher
residues of TCDD in the fat, with average values of 9, 12, 21 and 61 pet.
The simple .T.ean for this group of san^les was 26 pot. Of the ten results,
three sanples require reanalysis due to low recoveries, and one sarola
was not run due to limited size. The high values were ccnfirnied by both
analytical laboratories (21 & 21 ppt, and 54 & 69 ppt).
The results of the analyses of the Oregon Elk showed residues of TCD in
3 of 4 adipose sanples, with average values of 5, 7, 7 and 26.5 ppt
TCD. The mean for this group of sanples V >»ould be 21 ppt. Of the
See footnote on page 42.
F-57
-------
- 46 -
Table 12
Dietary Intake of TC1D Fran Contaminated Deer or Elk
TCDD in TOD in Dietary Intake**/
Animal Fat (pot) Meat (pot)* (pa/person/day) pc/kg bw/day***/
DEER NDC2-13) - 31 0.08 - 5.27 9.9 - 65D 0.14 - 9.3
ELK ND(0.8-2S)- 68 0.03-11.56 3.7-1430 0.05-20.5
*/ Assumes 4% - 17% fat, depending on season. Computed range
is the lowest percentage fat multiplied by lowest limit of
detection to the highest percent fat nultiplied by the
highest detected residues. Thus 2:0.04 =0.08; 31.tD.17 «
5.27; 0.85(0.04 » 0.03; 68*0.17 « 11.56
**/ Assumes deer and elk meat is consumed at the same rate as
beef is consumed (124 gms/person/day.).
/ Assumes a 70 kg person
*•*•»
Thus, a person consuming contaminated deer meat once a month (or for a
period of 12 days following the hunting season), for example, could
possibly ingest from 1.7 to 111 pg 2,3,7,8-TCD/kg-3W/ year. Similarly, a
person consuming contaminated elk meat could, at that rate, ingest from
0.6 to 246 pg 2,3,7,8-TC:DAg BW/year.
An informal survey of ten persons was taken during June, 1983 (Ref.9)
to determine typical consumption of deer and elk meat. The 10 people
contacted resided in Oregon, and reported having deer and/or elk meat
on hand. One person consumed venison 4 times a week until all meat on
hand was goner six people consumed venison or elk meat about once a
week; the other three persons consumed venison or elk about once every
two weeks, until the meat -was gone. Typical consumption of this group of
people seemed to be about once a week. It is not known whether any other
persons were contacted who did not have game on hand, or whether this
group of persons were selected because it was suspected that they were
likely to have game en hand. . ,
F-59
-------
- 48 -
1 Accession 49. Sunrary of Deer and Elk Study. 1/23/83. EPA Exhibit
No. 199.
2. Anonymous. 1979. The Biologic and Eccnonic Assessment of 2,4,5-T. A
Report of the USDA-States-EPA 2,4,5-T RPAR Assessment Team, Feb. 15,
1979. Chapter 5, 1-212.
3. Baur, J.R., R.W. Bcvey and J.D. Smith. Eierbicide Concentrations in
Live Oak Treated with Mixtures of Picloram and 2,4,5-T. Vfeed Science.
17(4). 567-570. October, 1969.
4. Bjerke, 2. L., J. C. Herman, P. W. Miller, and J. H. Wetters (1972).
Residue Study of Phencxv Herbicides in Milk and Cream, J. Agric.
Focd Chem. 20_, 963-967."
5. Bovey, R.W. and J.R. Baur. Persistence of 2,4,5-T in Grasslands of
Texas. Bull. Env, Contam. Toxicol. 8(4). 229-233. 1972.
6. Cochrane, W.P., Greenhalgh, R., and Lconey, N.E. (1976). Canadian
J. of Plant Sci., 207-210.
7. Devine, J. M. (1970), Report from the Syracuse University Research
Corp., "Silvex Residues in Rough Rice and and Straw", Life Sciences
Division, Pesticide Analysis Laboratory, pg. 11-17.
8. Durham, W.F.and H. R. Wolfe, 1962. Measurements of the Exposure of
Workers to Pesticides. Bull. WHD, 26, 75-91.
9. Green, G. Letter to G. Streisinger dated June 12, 1980.
10. Jensen, D.J, R.A. Hummel, N.H. Mahle, C.W. Kocher and H.S. Kiggins.
A Residue Study on Beef Cattle Consuming 2,3,7,8-Tetrachlorcdibenzo-p-
Dioxin (TCDD). July 19, 1978, Unpublished. (EPA Exhibit No.159).
11. Kearney, Phillip C., Edwin A. Wbolson, and Charles P. Ellington, jr.
Persistence and Metabolism of Chlorodioxins in Soils. 2nv. Sci. Tech.
6(12). Novenfcer, 1972. (EPA Exhibit No. 149)
12. No reference.
13. Kolmodin-Hedman, 3., K Erne, M. Hakansson, and A. Engqvist 1979.
Vetenskaplig Skriftserie, 17, 26 pp.
14. Lavy, T.L. 1979. Project Completion Report to National Forest Pro-
ducts Association. Measurement of 2,4,5-T Exposure of Forest 'Workers.
F-61
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- 50 -
28. Vferscn, M. Sunrary: Rationale and Study Design for Proposed TCTS
Analysis of Region X Elk and Deer Adipose Tissue Sarrsples. 9 A 3/78.
29. Watson, M. Lettar to Mr. Reade Brown dared 10 fl.7/77
30. Watson, M. Letters to Mr. Jerry MacLeod dated 10 AO and 10A7/77.
31. Vfolfs, K.R., J.?., Armstrong, D.C. Staiff, S.W. Copier, and W.F. Durham,
1975. Exposure of Apple Thinners to Parathion Residues Arch. Ervir.
Contam. and Toxicol. 3_, 257-267.
32. Young, Alvin L., Cross Examination Testimony, FIFSA Docket 4 415 et.al.
10131-10133. Wednesday, July 23, 1980.
33. 3weig, 3. Direct Testimony (EPA Exhibit No.203)
34. lygadlo, L. SFSD. Memo to G. Zweig on SA3/S3
F-63
-------
eraoMH
1.578
1 , 578
1,578
1.060
292
292
292
200
200
200
0.6
03
m
m
6
6
6
8
RICE
2
2
O.6
0.5-2
0.5-2
0.5-2
0.5-2
1
1
I
10
10
3
10
6
6
130
130-260(2)
tt)0 (4)
20.000
307(5)
307(5)
6500-9500 (5)
6
8
8
8
2
8
0.6
75
100
25
80
12
48
0.6
-------
- 54 -
*lt should be noted that we are more certain about cur estimate of the
total nunber of exposure-hours for each specified use and use pattern
than we are about the exact nunber of individuals in each group and the
nunber of hours worked by each individual.
Since for each occupational group. . .
total 3 exposure hrs5 * f of workers*3 x average T hrs worked or exccsedc
even if (b) and (c) were in error, they >ould vary inversely and (a) would
not chance appreciably.
SPECIFIC EXPLANATIONS OF TABLE A-l
Column 3 - Total Acreace
This number is taken from tables or the text of Part 5 of the Report, rc
exarole, the first figure under aerial forest, 876,000 A, is found in
Table 12, p. 5-95 of the report.
Colurra 4 and 5 - Acreace Treared/tJnit Tine - Duration of Trea-c^em
These nurbers are usually found in the text or in the " Calculation Sunnary"
of the Report. This is an estimated average based on the descriptive
portion of the Report or the Calculation Surmar/ Table, rcr exarrple, on
?. 5-92 of the Report it is stated that it may take 10-30 minutes to
treat 30 acres by helicopter. As stared in Calculation Sunnary No. 1,
one site of up to 1 3D acres usually 1-3 hours to treat -with herbicide.
Based on this specific information we have chosen 60 A/hour as the acreage
treated per unit tdje and 2hrs/cay as the duration of treatment.
Column 6 , Application Hates
Application rates are found in the text of the Report or in Calculation
Sunnary tables. When a ranee is given (e.g., 1.5-3 lb/A) the approximate
F-67
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- 56 -
usually are listed as being exposed for 2 hours/work day. The mixer-lead-
ers in aerial application ara engaged in the leading and taxing cf pesti-
cides during the actual application period (2 hours) but are assumed to
be working en other tasks throughout the workday (6-3 hours) without a
chance of clothes. Thus, we believe that the workers will be exposed to
2,4,5-T during the entire work day by contact through the skin from wet,
pesticide-contaminated, work clothes.
Column 10
Annual Exposure = Days/yr. (Col.7) x daily exposure (Col.9).
SPECIFIC DATA POINTS AMD ASSLT-PTTCNS*
Forestry - Air Application
Total Acreage - 376,500A (Table 12, p. 5-95).
Acreage Treated - ISOA/day; usually 1-3 hours (Calc. Surmary No.l).
Application Rats - 1.5-3 Ibs/A (Calculation SuTrrrary So. 1)
Days per year - ICO days (Table 10, p. 5-90)
e.g. Pacific Coast (pine release): Fab-March,
May-Cur.e and July-Sept
Daily Exposure - As disojssed previously, the assumption is mace that
the pilots are exposed 2 hours/day based on actual
flight time and change clothes at the completion of
the flight. Cn the other hand, the mixer-loaders
are assumed to remain in the field engaged in other
tasks, wearing contaminated apparel during the
normal working day of 3 hours. Therefore, exposure
is estimated at 2 hrs/day for pilots and 3 hrs/day
for mixer-loaders.
Forastry-3 round Broadcast (Tractor-applied)
Total acreage: 140,COOA (Table 12, pp. 5-100).
Application Rate; 2-3 Ibs/A (Table 14).
Acreace Treated: 5-8 A/hour (p. 5-99).
* All other data points are found in Table 1.
F-69
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- 58 -
Aerial Application (continued)
Days /year: Pilots and Mixer/Leaders: 1-4 wks., 10 days (avg)
(p. 5-111}
Flacperson: about 3 davs (assumes -4000 A farm at
1200A/day
Daily exposure: It is assumed that the pilots change clothes
after each flight period, making a total of 6
hours exposure. The other workers are assuned
to retain the same work clothes durirsg an 3-hr
workday, resulting in 3 hours of exposure.
Sxscsed Peculation; Assunirsg the average ranch to be of 40COA
size and 2 flag persons per ranch, it is
ated that (1,600,000: 4000) X 2 - 800 flag
persons will be employed. Other peculations
were estinated by the calculation shewn on p. 52.
Ranee and Pasture
Backpack Sprayer:
Total Acreage: 1,060 ,000 A (excluding mesquite, table 13,
Acreage; 3-5A/day (p. 5-113)
Duration of Treatrient; Shrs/cay
Rate: 0.5-2 Ibs/A (Table 13); weighted average: O.S Ib/A
Rics
The best available information is that 97% rice treatment is by air
(Report, p. 5-142).
Total acreace; 292,OOOA (p. 5-144)
Treated Acreage; 46A/35min or approximately SOAA^our (p. 5-148)
Duration of Treatment;
Calculated 2 hours/day and 6 days/year for pilots and Icadnen.
Calculated 0.5 hrs/year for flagperscns.
F-71
-------
- 60 -
b. Cst_Stmp (calculation Sumary 3)
Total Acreage; 9,901 A
Dosage; 3.2 Ib/A - 4.6 Ib /A
Average: 4 Ib /A
Duration of traatnient
34.7 weeks or 173 days / year
Application time: 6 hrs / day
Application rate; 0.3 A/hr
(based on estimate)
No. of workers exposed;
10,000
3 x 173 » 20 work craws
Crews made up of 2 spravmen
1 truck driver-fflixer
Total » 60 persons
(Sunrary Table 3_ lists 75 exposed personnel; this mist Lnclude 1 supervisor,
•who is net included in our estinatss. We also assure
that all persons are exposed during entire 5 hour r*ork day)
c. Mixed 3rush - Handcun (Caleolation Sumsry 9)
Total Acreage; 29,400 A
Treated Acreage: 0.5 A/hr
6 hour day
3 A/ day
Duration of Annual treatngrtt; 110 days
Srocsed Peculation: 89 v»ork crews consisting of 4 persons
Total: 356 persons
(Note: There is an error in Calculation Surmary 9; should
be 39 work crews instead of 39, as written.)
F-73
-------
- 62 -
6 hrs / cay
110 days / year
rctal ncs. of persons;
Driver / mixer-loader
2 spraynen
Nos. of crews;
44,000 » 133
330
Total TJOS. individijals = 400
F-75
-------
- 64 -
USE
TAELE A-3
Estimated Cccupaticral Expcsur1
EXPOSED WORKER VCRKER
ACTIVITY NUMBER
s to 2,4,5-T
AVG. AMDUOT
ABSORBED
(ac/fcs/hr)
GICUP
AVERAGES
(nn/kc/hr)
AERIAL
II
I*
II
II
II
H
II
II
II
GRCLMD
it
II
II
II
II
II
II
H
..
11
Pilot - Microfoii
Pilot - Raindrop
Mixer - Microfoii
" - Raindrop
Suu'r - Microfoii
"
" - Raindrop
Flagnan - Microfoii
H 11
H ii
„
Mixer/Leader - Tractor
Driver - Tractor
II — W
Sup'r -
Applicator - Bactoack
,.
: :
„
i,
Mi xer/ Supervisor
12
17
13
18
14
19
15
16
20
21
11
' 10
9
3
7
6
5
4
3
2
1
.005
-- . .024
.061
.063
.004
.004
.006
.XI
.002
.002
.020
.014
.012
.006
.024
.014
.009
.014
.026
.036
.005
.015
1
.062 |
.004
.003
.020
.013
.006
.021
.005
F-77
-------
(DOR
(8) OK
(DOT 'U)6
(OQK
(8) OK
(8)OK
(OT)OK
(frDOK
( OT) ON
(CD a;
( OT) OK
(OT)OK
(OT)ON
(OT)OK
(8) as
(OT)CK
(OT)OK
(8)*C '(8)Te
(I) OK
(DON
(8) OK
(OT)£T '(OT)eT
(OT)OK
(8) OR
(OT)OK
(Ot)OK
(L) TT 'UU
(i)8 '(L)I
(OT)OK
TE-IIVH
8 2- IKS
1Z-IKB
9Z-IKE
EZ-IIVS
t'T-IIVH
TT-IIVH
OT-nvi
H9£-:iYE
9E-UVE
H£t-IIVS
SE-HVE
frE-IIVH
it-nva
9^-IPtfS
^z-rrvB
TZ-IIV5
OZ-IKH
8T-IIVH
iT-IIVE
9T-IIV3
ZT-HVH
e-iivs
9-HVH
z-iiva
T-IKH
6-IIVS
c-nvE
t-IKB
Z/T
e/T
Z/T
2/T
Z/T
Z/1
Z/T
Z/T
We
We
We
We
We
2
z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
e
e
">S^.?l1SfI) 5SS (SSUS*
BsnpTsaj-
- 99 -
-------
- 68 -
Table A-7
Criteria Used by the Dicxin Mcnitcrinc ?iu>jijir
"o Confirm TCDD Residues
1 . Canillary colum GC/H5MS retention time of reference standard
2,3,7,8-TCSD.
2. Co-Injection of sample fortified with 37ci-TCDD a™3 2,3,7,3-TCTD
standard.
3. Correct molecular ion chlorine isotope ratio {m/e 320 and m/e 322).
4. Capillary col am GC/KEMS which give siirultaneous multiple icn mon-
itoring response (:n/e 320, m/e 322 and m/e 323) for TC2D.
5. M/e 320 and ra/e 322 MS response greater than 2.5 x noise level.
6. Recoveries of added TC3D must be between 50 and 120%
F-81
-------
APPENDIX G
THE CARCINOGEN ASSESSMENT GROUP'S
METHOD FOR DETERMINING THE UNIT RISK ESTIMATE
FOR AIR POLLUTANTS
PARTICIPATING MEMBERS
Elizabeth L. Anderson, Ph.D.
Larry Anderson, Ph.D.
Dolph Arnicar, B.A.
Steven Bayard, Ph.D.
David L. Bayliss, M.S.
Chao W. Chen, Ph.D.
John R. Fowle III, Ph.D.
Bernard Haberman, D.Y.M., M.S.
Charalingayya Hiremath, Ph.D.
Chang S. Lao, Ph.D.
Robert McGauchy, Ph.D.
Jeffrey Roser.^latt, B.S.
Dhann V. Singh, D.V.M., Ph.D.
Todd W. Thorslund, Sc.D.
t. Albert, M.D.
Chairman
July 31, 1980
G-l
-------
with an incidence determined by the extrapola* on model discussed below.
A. Choice of Model
There is no really solid scientific basis for any mathematical extrapolation
model which relates carcinogen exposure to cancer risks at the extremely low
concentrations that must be dealt with in evaluating environmental hazards. For
practical reasons such low levels of risk cannot be measured directly either by
animal experiments or by epidemiologic studies. We must, therefore, depend on
our current understanding of the mechanisms of carcinogens for guidance as to
which risk model to use. At the present time the dominant view of the
carcinogenic process involves the concept that most agents which cause cancer
also cause irreversible damage to DMA. This position is reflected by the fact
that a very large proportion of agents which cause cancer are also mutagenic.
There is reason to expect the quanta! type of biological response that is
characteristic of mutagenesis is associated with a linear non-threshold
dose-response relationship. Indeed, there is substantial evidence from
mutagenesis studies with both ionizing radiation and a wide variety of chemicals
that this type of dose-response model is the appropriate one to use. This is
particularly true at the lower end of the dose-response curve; at higher doses,
there can be an upward curvature probably reflecting the effects of multistage
processes on the mutagenic response. The linear non-threshold dose-response
relationship is also consistent with the relatively few epidemic!ogical studies
of cancer responses to specific agents that contain enough information to make
the evaluation possible (e.g., radiation induced leukemia, breast and thyroid
cancer, skin cancer induced by arsenic in drinking water, liver cancer induced
by aflatoxin in the diet). There is also some evidence from animal
experiments that is consistent with the linear non-threshold model (e.g., liver
G-3
-------
Equivalently,
A(d) = 1 - exp C-(qid +
where
A( d) = P(d) - P(o).
1 - P(o)
is the extra risk over background rate at dose d.
The point estimate of the coefficients q-f, 1 = 0, 1, 2, ..., k and
consequently the extra risk function A(d) at any given dose d is calculated by
maximizing the likelihood function of the data.
The point estimate and the 955 upper confidence limit of the extra risk A(d)
are calculated by using the computer program GLOBAL 79 developed by Crump and
Watson (1979). The calculation proceeds as follows: Let Lo be the maximum
value of the log-liklihood function. The 955 upper confidence limit for the
extra risk A{d) has the form
Au(d) = 1 - exp C-(q!*d + q2d2
where q| is calculated by increasing q^ to a value qj,* such that when
the log-liklihood is reroaximized subject to this fixed value qj* for the
linear coefficient, the resulting maximum value of the log-likelihood LI
satisfies the equation
2 (Lo - L!) = 2.70554
where 2.70554 is the cumulative 90% point of the chi-square distribution with
one degree of freedom, which corresponds to a 95* upper limit (one-sided). The
G-5
-------
point of the chi-square distribution with f degree of freedom, where f equals
the number of dose groups minus the number of non-zero multistage coefficients.
SELECTION AND FORM OF DATA USED TO ESTIMATE PARAMETERS IN THE EXTRAPOLATION
MODEL
For some chemicals, several studies in different animal species, strains,
and sexes each run at several doses and different routes of exposure are
available. A choice must be made of which of the data sets from several studies
to use in the model. It is also necessary to correct for metabolism differences
between species and absorption factors via different routes of administration.
The procedures used in evaluating these data are consistent with the approach of
making a maximum-likely risk estimate. They are listed below.
1. The tumor incidence data are separated according to organ sites or tumor
types. The set of data (i.e., dose and tumor incidence) used in the model is
the set where the incidence is statistically significantly higher than the
control for at least one test dose level and/or where the tumor incidence rate
shows a statistically significant trend with respect to dose level. The :ta
set which gives the highest estimate of the lifetime carcinogenic risk q^*
is selected in most cases. However, efforts are made to exclude data sets which
produce spuriously high risk estimates because of a small number of animals.
That is, if two sets of data show a similar dose-response relationship and one
has a very small sample size, the set of data which has larger sample size is
selected for calculating the carcinogenic potency.
2. If there are two or more data sets of comparable size which are identical
with respect to species, strain, sex, and tumor sites, the geometric mean of
the exponent g(d), estimated from each of these data sets and evaluated at a
specific dose d, is used for risk assessment. The geometric mean of numoers
G-7
-------
Then, the lifetime average exposure is
L x
Often exposures are not given in units of mg/day and it becomes necessary to
convert the given exposures into mg/day. For example in most feeding studies
exposure is in terms of ppm in the diet. In this case the exposure in mg/day is
m * ppm x F x r
where ppm is parts per million in the diet of the carcinogenic agent and F is
the weight of the food consumed per day in kgms and r is the absorption
fraction. In the absence of any data to the contrary r is assumed to be equal
to one. For a uniform diet the weight of the food consumed is proportional to
the calories required which in turn is proportional to the surface area or
2/3rds power of the weight, so that
m a-ppm x v£/3 x r or
m a ppm
As a result, ppm in the diet is often assumed to be an equivalent exposure
between species. However, we feel that this is not justified since the
calories/kg of food is very different in the diet of man compared to laboratory
animals primarily due to moisture content differences. Instead we use an
empirically derived food factor f = F/W which is the fraction of a species bosy
G-9
-------
Case 1
Agents that are in the form of participate matter or virtually completely
absorbed gases such as S02 can reasonably be expected to be absorbed
proportional to the breathing rate. In this case the exposure in mg/day .-nay be
expressed as '
m = I x x r
where
I = inhalation rate per day in m3
v » mg/m3 of the agent in air
r = the absorption.fraction
The inhalation rates, I, for various species can be calculated from the
observations (FASEB 1974) that 25 gra mice breathe 34.5 liters/day and 113 gm
rats breathe 105 liters/day. For mice and rats of other weights, W (in
kilograms), the surface area proportionality can be used to find breathing rates
in rn^/day as follows:
For mice, I = 0.0345 (W/0.025)2/3 m3/day
For rats, I = 0.105 (W/0.113)2/3 tip/day
For humans, the values of 20 m^/dayt is adopted as a standard breathing rate
(ICRP 1977).
The equivalent exposure in mg/V/2/3 for these agents can be derived from
the air intake data in way analogous to the food intake data.
"From "Recommendation of the International Commission on Radiological
Protection", page 9, the average breathing rate is 107 cn° per 3 hour wcr<
^ay and 2 x 10' cm3 in 24 hours.
6-11
-------
concentration in ppm or ug/nr3 in experimental animals is equivalent to the
same concentration in humans. This is supported by the observation that the
minimum alveolar concentration that is necessary to produce a given "stage" of
anesthesia is similar in man and animals (Dripps, et al. 1975). When the
animals were exposed via the oral route and human exposure is via inhalation or
vice-versa, the assumption is made, unless there is pharmacokenetic evidence to
the contrary, that absorption is equal by either exposure route.
5. If the duration of experiment (Le) is less than the natural lifespan of
the test animal (L), the slope qi* or more generally the exponent g(d) is
increased by multiplying a factor (L/Le)3. We assume that if the average
dose, 0, is continued, the age specific rate of cancer will continue to increase
as a constant function of the background rate. The age specific rates for
humans increases at least by the 2nd power of the age and often by a
considerably higher power as demonstrated by Doll (1971). Thus, we would expect
the cumulative tumor rate to increase by at least the 3rd power of age. Using
this fact we assume that the slope q^* or more generally the exponent g(d),
would also increase by at least the 3rd power of age. As a result, if the slope
qi* Cor g(d)] is calculated at age Le, we would expect that if the
experiment had been continued for the full lifespan, L, at the given average
exposure, the slope q^* [or g(d)] would have been increased by at least
(L/le)3.
This adjustment is conceptually consistent to the proportional hazard model
proposed by Cox (1972) and the time-to-tumor model considered by Crump et al.
(1979) where the probability of cancer at age t and dose d is given by
P(d,t) = 1 - exoC-f(t) x g(d)l
6-13
-------
ESTIMATION OF UNIT RISK BASED ON HUMAN DATA
If human epidemiology studies and sufficiently valid exposure information
are available for the compound, they are always used in some way. If they show
a carcinogenic effect, the data are analyzed to give an estimate of the linear
dependence of cancer rates on lifetime average dose, which is equivalent to the
factor BH« If they show no carcinogenic effect when positive animal evidence
is available, then it is assumed that a risk does exist but it is smaller than
could have been observed in the epidemiology study, and an upper limit of the
cancer incidence is calculated assuming hypothetically that the true incidence
is just below the level of detection in the cohort studied, which is determined
largely by the cohort size. Whenever possible, human data are used in
preference to animal bioassay data.
In human studies, the response is measured in terms of the relative risk of
the exposed cohort of individuals compared to the control group. In the
analysis of this data it is assumed that the excess risk, or relative risk minus
one, R(XI) - 1, is proportional to the lifetime average exposure, Xj., and
that it is the same for all ages. It follows that the lifetime risk in the
general population exposed to a lifetime average concentration X2, P(X2), is
equal to [RfX^ - l]X2/Xi multiplied by the lifetime risk'at that site in
the general population. The unit risk estimate is the value of P when X2 is 1
ug/m^. Except for an unusually well documented human study, the confidence
limit for the excess risk P is not calculated, due to the difficulty of
accounting for the uncertainty inherited in the data (exposure and cancer
response).
G-15
-------
REFERENCES
Albert, R.E.,. et al. 1977. Rationale developed by the Environmental Protection
Agency for the assessment of carcinogenic risks. J. Nat! . Cancer Inst.
58:1537-1541.
Cordle, F.t P. Corneliussen, C. Jellinek, B. Hackley, R. Lehman, J.
Mclaughlin, R. Rhoden, and R. Shapiro. 1978. Human exposure to
polychlorinated biphenyls and polybrominated biphenyls. Environ. Health
Perspect. 24:157-172.
Cox, C.R. 1972. Regression model and life tables. J. Roy. Stat. Soc. B
34:187-220.
Crump, K.S., H.A. Guess, and L.L. Deal. 1977. Confidence intervals and test of
hypotheses concerning dose-response relations inferred from animal
carcinogenic!ty data. Biometrics 33:437-451.
Crump, K.S. 1979. Dose-response problems in carcinogenisis. Biometrics
35:157-167.
Crump, K.S., W.W. Watson. 1979. GLOBAL 79. A fortran program to extrapolate
dichotomous animal carcinogenicity data to low dose. Nat!. Inst. of
Environ. Health Science. Contract No. l-ES-2123.
Crump, K.S. 1980. An improved procedure for low-dose carcinogenic risk
assessment from animal data. J. of Environ. Pathology and Toxicology (in
preparation).
Doll, R. 1971., Weibull distribution of cancer. Implications for models of
carcinogenesis, J. Roy. Statistical Soc. A 13:133-166.
Dripps, Robert D., J.E. Eckenhoff, and L.D. Yandam. 1977. Introduction to
anesthesia, the principles of safe practice. 5th Ed. W.B. Saunders Company,
Phil. Pa. pp. 121-123.
FASEB. 1974. Biological Data Books, 2nd ed. Vol. III. Edited by Philip L.
Altman and Dorothy S. Dittiuen. Federation of American'Societies for
Experimental Biology. Bethesda, MD. Library of Congress No. 72-87738.
Guess, H., et al. 1977. Uncertainty estimates for low dose rate extrapolations
of animal carcinogenicity data. Cancer Res. 37:3475-3483.
Interagency Regulatory Liaison Group. 1979. Scientific bases for identifying
potential carcinogens and estimating their risks. Feb. 6, 1979.
International Commission on Radiological Protection. 1977. Recommendation of
the International Commission on Radiological Protection, Pub. No. 26,
adopted Jan. 17, 1977. Pergammon Press, Oxford, England.
Mantel, M., and M.A. Schneiderman. 1975. Estimating "Safe Levels, A Hazardous
Undertaking. Cancer Res. 35:1379-1386.
G-17
-------
CORRECTIONS TO CARCINOGEN ASSESSMENT GROUP'S RISK ASSESSMENT
ON 2,4,5-T, SILVEX, AND TCDD
(Dated September 12, 1980)
Page
Line
Present
Should Be
104
106
106
106
109
109
110
110
110
111
115
116
116
120
130
131
132
133
134
135
137
1
18-19
18
21
18
18
9
19
last
4
3
Table 49
Table 59
7
11
10
6
9
9
ae
that apply 2,4,5-Tx
the applicators
Pg. 13
exposures
4.7 x. lO-4
high consumer group
as high as or
4.7 x 10-4
were
Females
Revised Table attached
Revised Table attached
8.4 x 105
210-4
4.8 x 10-3
Local population*
pg/kg/bw/day
4.7 x 10-4
are
(omit)
the 2,4,5-T applicators
Pg. 14
exposure
4.5 x 10-4
local population
(omit)
4.5 x ID'4
is
delete footnote b
Females3
Delete footnote and
replace with:
Subcutaneous
combined fibroma or
fibrosarcoma not
significant
8.4 x ID'5
< 10-4
5.2 x 10-3
(omit *)
pg/kg bw/day
4.5 x 10-4
-------
TABLE 49. CURVE FIT OF THE MULTISTAGE MODEL PARAMETERS TO EXPERIMENTAL DATA BY STUDY AND PATHOLOGIST
LINEAR PARAMETER q1§ MAXIMIZED TO GIVE UPPER 95% LIMIT q*
Compound TCDD
Study Kodba - Dow
Sex-speci es Mai e rat
Weight (wa) 600 gm
Tumor sites (one or more) Tongue - squamous cell carcinomas
Nasal turbinates/hard palate - stratified squamous cell carcinoma
Pathologist - Kociba
Exposure level (mg/kg/day) 0 1 x 10~6 1 x 10-5 1 x 10~4
+r/n 0/76 2/49 1/49 3/42
+r = number of animals with one or more of the tumors
n = total number of animals examined
Estimated Goodness of fit
multistage parameters qg Ql (\2 93 ° O.Ol) ="3.01 x
qh = ^i (70/wa)l/3 = 1.47 x 104, the upper 95% limit one-hit slope factor associated with
human aose response.
-------
TABLE 59.
l_ \Ji w
Compound
Species
Study
Sex
Pathologist Human Slope Estimate qfj
CJ
o
TCDO Rat Dow Male
Female
NCI Male
Female
Mice NCI Male
Female
Kociba
Squire
Kociba
Squire
NCI - Reviewed
NCI - Reviewed
NCI - Reviewed
NCI - Reviewed
1.47 x 104
1.73 x 104
2.52 x 105
4.25 x 105*
2.43 x 104
3.28 x 104
1.33 x 105
4.56 x 104
2,4,5-T
Rat
Dow
Male
Kociba
Squire
1..65 x 10-2
1.82 x 10-2*
*Values used in risk analysis
o ro w a
i-1- o c\ GQ
O H- .
P CO O
0*1 • 3 TO
O -j
• o o- <
CC - H-
K-l ft! M
t- 4 t-
cr i - r<
o .r d
cr> 3 £ :j
C T rt
cr> ro ^ p-
O rf t_i
CD C' >-d
c+ t^ i
S'fS-
O (_
B o
CTl >>»
^ OtJ
O o
3
O
------- |