REPORT
of the
ADVISORY COMMITTEE ON 2,4,5-T
to
THE ADMINISTRATOR
of the
ENVIRONMENTAL PROTECTION AGENCY
Submitted, May 7, 1971
-------
CONTENTS
Page
Membership of the Advisory Committee 1
Introduction 3
I. Factors Influencing Exposure to Man 8
A. Patterns of use of 2,4,5-T 8
B. Fate in soil, air, water and plants 9
Fate of 2,4,5-T 9
Fate of TCDD 14
References cited in Section I A and B 18
C. Fate in animals 23
Fate of 2,4,5-T 23
Fate of TCDD 25
References cited in Section I C 26
II. Toxicity of 2,4,5-T and TCDD in Animals and Man 28
A. Nonteratogenic toxicity 28
of 2,4,5-T 28
of TCDD 33
References cited in Section II A 34
B. Teratogenic Potential of 2,4,5-T 37
1. Scope of embryotoxicity 37
2. Data from laboratory animals 39
2,4,5-T in rats 41
TCDD in rats 45
2,4(5-T in mice 46
TCDD in mice 47
2,4,5-T in hamsters 48
TCDD in hamsters 49
2*4,5-T in rabbits 49
2,4,5-T in sheeps 49
2,4,5-T in rhesus monkeys 49
Summary of data on laboratory animals 50
3. Human exposure during pregnancy 51
Vietnam 51
Summary of Vietnam data on
Human Embryotoxicity 57
Globe, Arizona 58
Swedish Lapland 59
References cited in Section II B 60
-------
III. General Conclusions
64
IV. Recommendations 66
V. Statement of views of Dr. Theodor D. Sterling
entitled, "Objections to and Modifications of
the Final Report and Recommendations of the
2,4,5-T Advisory Committee". 68
VI. List of Persons conferring with the Committee 76
-------
-1-
MEMBERSHIP of the ADVISORY COMMITTEE
James G. Wilson, Ph.D., Chairman
Roswell K. Boutwell, Ph.D.
Donald E. Davis, Ph.D.
Frank N. Dost, DVM
Professor of Research Pediatrics and
Anatomy, Children's Hospital Research
Foundation and College of Medicine,
University of Cincinnati, Ohio
Professor of Oncology, McArdle
Laboratory for Cancer Research,
University of Wisconsin Medical Center
Madison, Wisconsin
Alumni Professor, Department of
Botany and Microbiology, Auburn
University, Auburn, Alabama
Associate Professor of Veterinary
Medicine, Science Research Institute,
and Environmental Health Sciences
Center, Oregon State University,
Corvallis
Wayland J. Hayes, Jr., M.D.,Ph.D. Professor of Biochemistry, Department of
Biochemistry, University School of
Medicine, Nashville, Tennessee
Harold Kalter, Ph.D. Professor of Research Pediatrics,
Children's Hospital Research
Foundation and College of Medicine,
University of Cincinnati, Ohio
-------
-2-
Ted A. Loomis, M.D., Ph.D.
Arthur Schulert, Ph.D.
Theodor D. Sterling, Ph.D.
David L. Bowen
Professor Pharmacology and State
Toxicologist, Department of Pharmacology,
University of Washington School of
Medicine, Seattle
President, Environmental Science and
Engineering Corp. and Associate
Professor of Biochemistry, Vanderbilt
University School of Medicine,
Nashville, Tennessee
Professor, Dept. of Applied Mathematics
and Computer Science, Washington
University, St. Louis, Missouri
Secretariat to Advisory Committee
Environmental Protection Agency
-------
-3-
INTRODUCTION
On October 29, 1969, the President's Science Advisor, Dr. Lee A.
DuBridge, announced that a series of coordinated actions was being taken
by several governmental agencies to restrict the use of the herbicide
2,4,5-trichlorophenoxyacetic acid (2,4,5-T). This was precipitated by
release a few days earlier of the findings of a large-scale screening
study of a number of pesticides and industrial chemicals conducted by
Blonetics Research Laboratories In which it was found that mice and
rats treated during early pregnancy with large doses of 2,4,5-T gave
birth to defective offspring.
The announcement, together with reports of an increased occurrence
of birth defects by South Vietnamese newspapers during June and July
1969, elicited far-reaching reactions from governmental agencies,
segments of the scientific community, various lay groups concerned with
environmental problems, and from the public communications media.
Government-sponsored panels of experts, special commissions set up by
scientific organizations, hearings before subcommittees of the U.S.
Senate, and conferences attended by representatives from industry,
government, and universities examined available data and heard expert
opinions. None of these groups, however, was able to provide 'a
generally acceptable answer to the central question of whether 2,4,5-T,
as currently produced and used, constituted a risk for human pregnancy.
At least one reason for failure to reach a satisfactory resolution of
the issue was the paucity of reliable, scientific evidence.
Additional animal experiments performed early in 1970 confirmed
that the purest available sample of 2,4,5-T, given in large doses to
-------
-4-
pregnant mice, did indeed result in the delivery of some malformed
offspring. The question then becomes one of whether, or to what extent,
such animal data could be extrapolated to man. On April 14, 1970, an
attitude of caution was expressed by the Secretary of Health, Education
and Welfare, who advised the Secretary of Agriculture that: "In spite
of these uncertainties, the Surgeon General feels that a prudent course
of action must be based on the decision that exposure to this herbicide
may present an imminent hazard to women of child-bearing age." Accord-
ingly, on the following day the Secretaries of Agriculture, of Health,
Education, and Welfare and of Interior jointly announced the suspension
of the registration of 2,4,5-T for: "I. All uses in lakes, ponds or on
ditch banks. II. Liquid formulations for use around the home, recreation
areas and similar sites." (USDA-PRD PR 70-1, 20 Apr. 1970) A notice for
cancellation of registration was issued on May 1 for: "I. All granular
2,4,5-T formulations for use around the home, recreation areas and similar
sites. II. All 2,4,5-T uses on crops intended for human consumption."
(USDA-PRD PR 70-13, 1 May 1970) All registrants of 2,4,5-T were advised of
these actions, and two of the registrants, Dow Chemical Company and Hercules
Incorporated, exercised their right under Section 4.c. of the Federal Insect-
icide, Fungicide and Rodenticide Act (7 U.S.C. 135 et seq.) to petition for
referral of the matter to an Advisory Committee.
The National Academy of Sciences supplied a list from which was
selected a nine-member Advisory Committee of scientists with appropriate
qualifications from universities and research institutes over the country.
At its first meeting on February 1 and 2, 1971, the Advisory Committee
was given a charge which in substance asked that it: 1) consider all
-------
-5-
relevant facts, 2) submit a report and recommendations regarding registra-
tion for certain uses of 2,4,5-T, and 3) state the reasons or bases for
these recommendations. It was the concensus of the Committee that the
central issue was whether use of the herbicide does in fact constitute an
imminent health hazard, especially with respect to human reproduction.
Accordingly, the Committee has undertaken to examine all available infor-
mation and to evaluate its relevance to the potential hazard of human
exposure during pregnancy.
During the intervening months since restrictions were placed on the
use of 2,4,5-T a number of additional studies have been carried out on
several animal species and a few reports on human exposure during pregnancy
have been further evaluated. Although the new data have not answered all of
the questions that have been or could be raised, they have undoubtedly pro-
vided a more substantial basis for making a scientific judgment about poss-
ible effects of this herbicide on prenatal development than previously
existed. In undertaking such judgment the Committee has taken into account
certain considerations that seem appropriate to the issue, as follows: 1)
As is frequently the case, available data are insufficient for a definitive
statement of conditions under which a specified risk might occur, assuming
that freedom from risk is ever attainable. 2) Since most chemicals under
suitable laboratory conditions could probably be demonstrated to have
teratogenic effects, and certainly all could be shown to produce some toxic
effects if dosage were raised high enough, it would not be reasonable to
consider the demonstration of toxic effects under conditions of greatly
elevated dosage sufficient grounds for prohibiting further use of a partic-
ular chemical. 3) Benefits are to be expected from the continued use of
-------
-6-
2,4,5-T. The necessity of making a value judgment of benefit vs. risk,
therefore, must be accepted, not only for this herbicide, but for numerous
valuable drugs, some natural nutrients, and many other chemicals, some of
which are known to be teratogenic in laboratory animals. The risk vs.
benefit judgment for a particular herbicide or drug can be evaded only if
it can be shown that another compound is equally as efficient and involves
less risk. This presupposes that the risk potential of a substitute herb-
icide is at least as well known as that of the original (in this case
2,4,5-T), a fact that may be difficult or impossible to ascertain. The
substitution of a relatively unknown pesticide for an older one with known
adverse effects is not a step to be taken lightly. Even with steadily
improving methods for safety evaluation of new chemicals it is impossible
to anticipate all of the conditions and permutations of use that could
result in undesirable effects.
The task of making a judgment about the central question of hazard
to human pregnancy is complicated by still other considerations. Although
herbicides are of economic benefit to man, their use is not without possible
hazard to the environment and to other aspects of human welfare. In various
connections questions have been raised about: 1) damage to non-target
plants caused by spray drift or by movement in water, 2) damage to sub-
sequently planted sensitive crops owing to herbicide persistence in the soil,
and 3) acute or chronic toxicity to man or other animals aside from that
related to pregnancy. In addition, there is some concern that traces of the
chemical or its contaminants in food may cause unsuspected effects in man or
that minute amounts in the environment may adversely affect untested species
in the ecosystem.
-------
-7-
It is scientifically impossible to prove that a chemical is without
hazard. Pesticide regulations now require that new agents be tested for
acute and chronic toxicity, mutagenicity and carcinogenicity. These tests
may involve the use of two or more species of animals taken through several
generations and the examination of thousands of individuals. Since it is
necessary to extrapolate from effects in test animals to man and since
species are known to differ in sensitivity to chemicals, the permissible
residue levels in food must always be many-fold below the minimal effect
level for the species tested. Concern that some unexpected detrimental
occurrence may outweigh the benefit of a pesticide has doubtless been
heightened by the finding that DDT residues in the environment have adverse-
ly affected reproduction in certain predatory avian species that are at the
top of their food chains and, as a consequence, ingest large accumulations
of this persistent compound.
With these considerations in mind the Advisory Committee has exam-
ined all available information relating to factors that may influence
human exposure to 2,4,5-T and the toxic reactions, nonteratogenic as well
as teratogenic, such exposure of man and other animal species may entail.
-------
-8-
I. FACTORS INFLUENCING EXPOSURE TO MAN.
Human exposure to an environmental chemical such as 2,4,5-T
depends on 1) pattern of usage, i.e., how widely and frequently
applied and in what amounts, and 2) its fate in the environment, i.e.,
does it accumulate or is it degraded as fast as applied.
A. Patterns of use.
The chloro-phenoxy herbicides 2,4-D and 2,4,5-T have been widely
used to control broad-leaved weeds for over 20 years. Because 2,4,5-T
is more expensive than 2,4-D (2,4-dichlorophenoxyacetic acid) it has
been primarily used to control woody plants and a few herbaceous
species against which it is more effective than 2,4-D, and because of
the cost difference, commercial formulations containing 2,4,5-T are
usually mixtures of the two herbicides. In 1964 the uses of 2,4,5-T
were: rights-of-way - 49%, non-farm forests - 10%, hay, pasture, and
rangelands - 7%, all other farm uses - 12%, lawns and turf - 7%,
federal agencies - 6%, and other miscellaneous uses - 9%.—^ The total
domestic use at that time was about 9 million pounds and incomplete
information indicates that this value may also be approximately correct
for 1969
Most of the 2,4,5-T used is applied as a spray to foliage.
Lesser amounts are sprayed on the trunks and branches of dormant trees,
injected into the bases of trees, poured or sprayed into frills around
the trunks of trees, or sprayed or painted on newly cut stumps of trees.
Amine salts of 2,4,5-T dissolved in water are most often used when the
herbicide is applied to foliage and esters dissolved in oil are most
-------
-9-
often used when it is applied to bark. The spray concentrations
usually vary between 0.1 and 2.5% and the rates of application are
usually between 0.5 and 8 lb per acre, depending on the size and
sensitivity of the plants being treated. Higher rates and concentra-
tions have been used in Vietnam for military purposes.
On domestic rice, 0.50 to 1.25 lb per acre of 2,4,5-T is used in
3/
5 to 7 gal of water- , applied from the air wh.en the rice is 7 to 9
weeks old, has emerged from the water, and is*standing erect.
Directions for the use of 2,4,5-T warn against allowing it to drift
onto susceptible plant species and require that the herbicide not be
allowed to contaminate water used for irrigation or domestic purposes.
B. Fate in soil, air, water and plants.
When 2j4,5-T is applied as a spray, the great bulk of the herbicide
and any contaminant it may contain, e.g., 2,3,7,8-tetrachlorodibenzo-
paradioxin (TCDD), are deposited on the foliage of the plants, on the
ground in the immediate vicinity or, in the case of rice, on the
impounded water. Much smaller amounts may be inserted into the air or
settle on streams of water and by either means be carried many miles
from the site of application. After 2,4,5-T and TCDD are applied,
however, each moves through the biosphere and accumulates or degrades
according to its own chemical and physical properties. The fate of
2,4,5-T has been more extensively studied than that of TCDD.
Fate of 2,4,5-T. Once the herbicide reaches the soil it is
immediately subjected to physical and chemical actions that continually
reduce the amount remaining at the site of application. These actions
include degradation by soil microorganisms, leaching and surface
-------
-10-
movement in water, volatilization, movement by wind, and photochemical
decomposition. The persistence of 2,4,5-T is influenced by its rate of
application and by various climatic and edaphic factors, and occurs most
rapidly under conditions that are optimal for the growth of soil micro-
organisms.—^ At least two bacterial isolates, Mycoplano sp. and Achro-
mobacter ay.— — — — and one actinomycete, Streptomyces virldochromogenea^
from soil are known to metabolize 2,4,5-T. Brevibacterlum sp. has been
shown to cometabolize 2,4,5-T to a product tentatively identified as 3,5-
dichlorocatechol™^. Norris—^ found that 2,4,5-T was decarboxylated in
the litter of the forest floor and had a half-life of approximately 40 days.
12/
Loos— has thoroughly reviewed degradation of phenoxyalkanoic acids, in-
cluding 2,4,5-T. Loss of all phytotoxicity of 2,4,5-T applied to the soil
13/
was reported to occur 3 to 6 months after application.— No chemically
detectable amounts of 2,4,5-T were found in the soil 1 year after an
application of 2 lb per acre and only very small amounts were found 3 to 7
months after application.—^ Although the rate of disappearance varies,
there have been no reports of carry-over of 2,4,5-T from one year to the
next, indicating that no build-up in the soil would result from recommended
rates of treatment repeated annually.
When phenoxy herbicides were first introduced, highly volatile esters
were available and farmers were inexperienced in their use, there were
several instances in which the drift through air produced severe injury to
sensitive crops, usually in adjoining fields or more rarely at some distance
from the point of application* Owing to accumulated experience and the
institution of regulations regarding the conditions under which applications
can be made, as well as the removal of the volatile esters from the market,
-------
-11-
injury to crops Is now unusual. The elimination of drift sufficient to
injure most crop plants, however, does not eliminate the possibility of
drift that can be detected chemically.
Some of the 2,4,5-T applied as spray can be transported in the
atmosphere as droplets of spray, as the gaseous phase of 2,4,5-T, or
adsorbed on dust or other particulate matter in the air. In a survey in
the State of Washington, 2,4,5-T was detected 9 days out of 99 at Pullman,
in average concentration in positive samples of 0.045 pg/m . At Kennewlck
it was found 14 days out of 102 at average concentration in positive samples
3 14/
of 0.012 yg/m — . In Cincinnati, Ohio, 0.04 ppm was found adsorbed on
15/
dust in a trace of rain— presumably from applications in Texas. Photo-
chemical degradation would be expected to occur in the air, particularly at
high altitudes and in dry climates where ultraviolet radiation is highest.
Kearney et al.—^ report that exposure of 5 and 10 ppm water solutions of
2,4,5-T to ultraviolet light from a 450 watt Hanovia lamp greatly reduced
the 2,4,5-T present within 5 minutes. It is not possible to extrapolate
accurately from these data to the rate of decomposition in sunlight, but
it is obvious that photochemical degradation could play a significant role.
Probably most of the 2,4,5-T that gets Into the air very soon either settles
out or is washed out by rain and thereby is returned to soil and water.
There is no evidence to suggest that 2,4,5-T remains in the air for more
than a few weeks after insertion.
Measurable quantities of 2,4,5-T could enter water in several ways,
e.g., by inadvertent direct spraying, from surface leaching of treated
soils and plants, or in rain that falls through air containing 2,4,5-T;
but undoubtedly most of it is washed from treated plants and soil.
-------
-12-
Apparently the amounts are usually quite small since only 28 of 322 water
samples taken in western states, where 2,4,5-T Is widely used for brush
control, were shown to contain 2,4,5-T^^ in concentrations ranging from
0.01 to 0.07 ppb. In closely controlled watershed studies in Waynesville,
North Carolina, no 2,4,5-T was found in any sample of run-off from an area
one-fourth of which was treated with 2 lb of 2,4,5-T per acre in 1968 or
18/
1969— . When one-fourth the area was treated with 4 lb per acre some herb-
icide was found in the water after the first and second rain storms, but the
highest concentration found was 0.048 ppm in run-off water during a storm
that occurred 8 days after application of the herbicide. No 2,4,5-T was
found in the last sample collected that day or in those collected on
subsequent days.
Few data are available on the rate of disappearance of 2,4,5-T from
water. It would be expected to be adsorbed on clay particles or adsorbed by
aquatic species within a few days. The concentration of picloram, a con-
siderably more persistent herbicide than 2,4,5-T in most situations, decreased
from 0.965 ppm to 0.129 ppm in 3 weeks in a test in which it was applied at
19 /
the rate of 4 lb per acre to a pond—^ . All available data suggest that the
amount of 2,4,5-T entering water is quite low and that it does not remain in
the water very long.
Absorption, translocation, and metabolism of 2,4-D and 2,4,5-T by
plants have been extensively investigated. Most investigations have dealt
with 2,4-D, but numerous studies have involved both and it is apparent that
their behavior in plants is similar. Ready absorption of 2,4,5-T by leaves,
r , , 20/21/22/23/24/25/ .
stems, and roots of plants is known to occur. •— Once
absorbed 2,4,5-T may either move upward in the xylem or bidirectionally in
-------
-13-
the phloem. Some 2,4,5-T is absorbed by the leaves, transported down the
22/
stem and Into the roots, and excreted by the roots into soil solution— .
Decarboxylation of 2,4,5-T has been demonstrated in a number of plant
12/
speciea-—. The varied sensitivity of different species to 2,4,5-T may be
25/
attributable in part to different rates of metabolism. Slife et al.—
found only traces of unidentified metabolites 8 days after applying *^C-
carboxyl-labeled 2,4,5-T to wild or cultivated cucumber plants, both species
susceptible to 2,4,5-T. Basler and associates—^—'' applied ^C-carboxyl-
labeled 2,4,5-T to excised blackjack oak leaves. They found no decarboxyl-
ation but did find that an average of 59% of the 2,4,5-T was broken down in-
to three major unidentified metabolites in 24 hours. Morton^^ reported
that 80% of 2,4,5-T applied to mesquite was metabolized in 24 hours. Fitz-
29/
gerald et al.— identified 2,4,5-trichlorophenol as a common metabolic
product of 2,4,5-T in sweetgum and southern red oak but found that no 2,4,5-
trichloroanisole was formed. Morton et al.—^ have studied the metabolism
of various formulations of 2,4,5-T by beardgrass, little bluestem, and side-
oats gramma and observed only moderate effect of formulation and species on
the rate of metabolism. Half-life values in green tissues ranged from 1.6
to 2.9 weeks. In one experiment using radioactive 2,4,5-T ester and silver
beardgrass, little bluestem, and dallis grass, alcohol extracts of green
tissue taken 1 week after application contained no 2,4,5-T ester, 50% 2,4,5-T
acid, and 50% unknown radioactive metabolite.
Authorization to use 2,4,5-T on food crops depends on demonstrating
that no residue exists in the edible product at harvest. The following
studies illustrate the amounts of 2,4,5-T that may persist in food crops at
various intervals after treatment. When 2,4,5-T was applied to apples as a
-------
-14-
spray concentration of 40 ppm, residue In the fruit had fallen to 0.004 ppm
in 22 days.—^ The application of 2,4,5-T to blueberries at 1 lb per acre
resulted in a concentration in the fruit of 0.05 to 0.33 ppm 44 days after
31/
application although none was found 733 days after application.—' No detect-
able 2,4,5-T (sensitivity » 0.01 ppm) was found in rough rice 50 days after
applying 2.25 lb per acre of 2,4,5-T.—^ The rice straw contained 0.18 to
1.04 ppm 2,4,5-T 50 days after but none 84 daj's after application.
Further evidence that very little 2,4,5-T gets into food is seen
in results of assays of raw agricultural products and in the Market Basket
Survey samples. From about 10,000 food and feed samples examined from 1964
through 1969 only 25 contained trace amounts of 2,4,5-T (less than 0.1 ppm)
and only two contained measurable amounts, 0.19 ppm in a sample of milk in
33/
1965 and 0.29 ppm in a sample of sugar beets in 1966.— Furthermore, of
the 134 total diet samples involving 1600 food composites (Market Basket
Survey) analyzed from 1964 through April 1969, only 3 contained 2,4,5-T.
Two were dairy products containing 8 to 13% fat with 0.008 and 0.19 ppm in
the fat. A single meat, fish and poultry composite from Boston consisting
of 17 to 23% of fat was found to contain 0.003 ppm 2,4,5-T on a fat basis.—^
34/35/
It is concluded from the foregoing that: 1) The herbicide 2,4,5-T
does not accumulate in any compartment of the biosphere. 2) The risk of
human exposure to 2,4,5-T in food, air or water is negligible.
Fate of TCDD. Under present conditions of manufacture this con-
taminant is usually present in 2,4,5-T at less than 1 ppm, thus Insuring
that very little TCDD is inadvertently applied with 2,4,5-T. Like 2,4,5-T
any contaminating TCDD would be deposited on the leaves of treated vegetation
-------
-15-
or on soil and water in the vicinity, although as indicated for 2,4,5-T,
smaller amounts could enter air or water and be carried some distance from
the site of application. Water transport, however* is sharply limited by
36 /
the fact that the solubility of TCDD in water is only 0.2 ppb.— As a
consequence it would tend to remain on the surface of plants and soil at
the site of application.
Photochemical decomposition of TCDD has been studied at Dow Chemical
37/ 38/
Co.—' and the United States Department of Agriculture.— Exposure of
1.02 mg of TCDD in 100 ml of water-saturated chloroform to ultraviolet
light at 35°C caused 50 to 100% degradation in 2.5 hours. The Department
of Agriculture, using a sunlamp with a peak emission at 310 nm, irradiated
TCDD dissolved in methanol and found it to have a half-life of 3.5 hours.
Rapid decomposition was also reported in natural sunlight when approximately
5 ml of a 24-ppm methanol solution of TCDD was sealed in glass tubes and
exposed to 7,000 to 9,000 footcandles of sunlight, with a half-life of
approximately 5 hours, virtual disappearance in 48 hours, and none detect-
able after 72 hours. Similar rates of decomposition, however, were not
observed when the TCDD was placed on the surface of dry soil where irradia-
tion for 96 hours with a sunlamp (maximum energy at 310 nm) did not cause
any significant loss by either photodecomposition or volatilization. The
same was true for wet soil irradiated for 6 hours.
Interactions of TCDD with soil have also been studied by the United
States Department of Agriculture.—^ When TCDD was placed on the surface
of five very different soils and subjected to leaching with water, the
TCDD did not move into any of the soils, probably because of its very
low water solubility. Similarly, in leaching experiments using soil thin-
-------
-16-
layer chromatographic technique, no TCDD moved from the spot of origin in
OQ j
either a Hagerstown silty clay loam or a Norfolk sandy loam.—' It would
thus appear that most of t-h* chemical falling on the soil surface would
remain there. The fate of TCDD mechanically incorporated into soil has
39/
been investigated by the Department of Agriculture.— Radiolabeled TCDD
was mixed into soil at the rates of 1, 10, and 100 ppm and soil extracts
radio-assayed 20, 40, 80, and 160 days after application. The amount of
radioactive material (probably TCDD) in the soil decreased 15 to 20% in
160 days, indicating that this compound was very slowly degraded in the
soil and could persist for more than a year.
The possibility that TCDD incorporated in the soil might be absorbed
by plants has been studied .-25/ Soybean and oat plants were grown on Lake-
land sand containing 0.06 ppm radiolabeled TCDD, which is 40,000 times the
amount that would appear in soils treated with 2 lb per acre of 2,4,5-T
containing 1 ppm TCDD. Less than 0.2% of the available TCDD was absorbed
by either type of plant, with radioactivity reaching a peak at 10 days at
which time it measured about 0.12 ppm in oats and 0.05 ppm in soybeans on
a dry weight basis, then it declined to an insignificant level at 40 days.
The most likely source of plant contamination by the TCDD present
as a contaminant in commercial 2,4,5-T is by way of foliar application.
When radioactive TCDD was applied to the surface of leaves™^ no material
was translocated from the site of application on the plant; but about 40
percent of the applied TCDD could be leached from the surface of the
leaves by water, probably because the TCDD was added with a surfactant.
This suggests that surface contamination could be the source of a very
small TCDD residue in leafy food plants, but 2,4,5-T is not used on such
-------
-17-
plants. Even if 2,4,5-T containing 1 ppm TCDD were applied to such plants
at the rate of 2 lb per acre, the resultant TCDD contamination would be at
the extremely low level of 0.224 yg per m on the exposed surface.
It is concluded from the foregoing that: 1) There, is no indication
that TCDD accumulates in air, water or plants, although ic «ri#it accumulate
in soils after heavy application of a highly contaminated sample of 2,4,5-T.
2) Direct application of 2,4,5-T containing TCDD could result in minute
quantities of the latter remaining on the surface of foliage. 3) Less
than 0.2% of TCDD in soil is known to be absorbed into plants.
-------
-18-
References Cited In Section I A and 6
1. USDA, 1970. Report and tables on domestic use of 2,4,5-T, 1964
and 1966. Supplied by Production Resources Branch, Farm
Production Economics Division, April, 1970.
2. Byerly, T.C., 1970. Use of 2,4,5-T in the United States. Letter
from Dr. Byerly to Senators Magnuson and Hart.
3. Dow, 1970. Petition, Part III, Item 3. Specimen labels for VEON
245. The Dow Chemical Co.
4. De Rose, H.R. and A.S. Newman, 1947. The comparison of the
persistence of certain plant growth-regulators when applied to
soil. Soil Sci. Soc. Amer. Proc., 12:222-226.
5. Bell, G.R., 1957. Some morphological and biochemical characteristics
of a soil bacterium which decomposes 2,4-dichlorophenoxyacetic
acid. Canad. J. Microbiol,, 821-840.
6. Bell, G.R., 1960. Studies on a soil Achromobacter which degrades
2,4-dichlorophenoxyacetic acid. Canad. J. Microbiol., j&:325-337.
7. Steenson, T.I. and M. Walker, 1958. Adaptive patterns in the
bacterial oxidation of 2,4-dichloro- and 4-chloro-2-methylphen-
oxyacetic acid. J. Gen. Microbiol., l8:692r-697.
8. Walker, R.L. and A.S. Newman, 1956. Microbial decomposition of
2,4-dichlorophenoxyacetic acid. Appl. Microbiol., 4^.201-206.
9. Bounds, H.C. and A.R. Colmer, 1965. Detoxification of some
herbicides by Stteptomyces. Weed Sci,, 13:249-252.
10. Horvath, R.S., 1971. Microbial cometabolism of 2,4,5-trichloro-
phenoxyacetic acid. Bulletin of Environmental Contamination and
Toxicology, ^5:537-541.
-------
-19-
11. Norris, L.A., 1970. Degradation: of herbicides in the forest floor,
p, 397-411. In: Youngberg, C.T. and C.B. Davey, Tree Growth and
Forest Soils. Oregon State Univ. Press, Corvallis. 527 p.
12. Loos, M.A., 1969. Fhenoxyalkanoic acids, p. 1-49, In: P.C.
Kearney and D.D Kaufman. Degradation of Herbicides. Marcel
Dekker, Inc., New York. 394 p.
13. Kearney, P.C., R.G. Nash and A.R. Isensee, 1969. Persistence of
pesticide residues in soils, p. 54-67. In: Chemical Fallout:
Current Research in Persistent Pesticides, ed. M.W. Miller and
George G. Berg, Chas. C. Thomas, Ft. Lauderdale, Florida.
14. Bamesberger, W.L. and D.R. Adams, 1966. Organic pesticides in
the environment. Adv. Chem. Ser., 60. ACS Publ. Wash., D.C.
15. Weibel, S.R., R.B. Weidner, J.M Cohen and A.G. Christianson, 1966.
Pesticides and other contaminants in rainfall and runoff. J. Amer.
Water Works Assn., 58:1075-1084.
16. Kearney, P.C., E.A. Woolson, J.R. Plimmer and A.R. Isensee, 1969,
Decontamination of pesticides in soils. Residue Reviews, 29:137-149.
Edited by F. Gunther. Springer-Verlag, New York.
17. Manigold, D.B. and J.A. Schulze, 1969. Pesticides In Water -
Pesticides in Selected Western Streams. A Progress Report.
Pesticide Monit. J., jj; 124-135.
18. Sheets, T.J., 1970. Watershed studies with 2,4-D, 2,4,5-T and
picloram. Communication from George Irving, Jr.» to T.C. Byerly,
April 3, 1970. (ARS Contract 12-14-100-893 <34)).
19. Hoffman, G.O., E.D. Robinson and M.G. Merkle, 1969. Loss of picloram
into surface and ground waters. Weed Science Soc. of Amer., Abstract
75. Supplemented by personal communcation from M.G. Merkle.
-------
-20-
20. Basler, E., 1962. Penetration, movement, and behavior of herbicides
in plants. Proc. Southern Weed Conf., 15;8-15.
21. Fisher, C.E., C.H. Meadors and R. Behrens, 1956. Some factors that
influence the effectiveness of trichlorophenoxyacetic acid in
killing mesquite. Weed Sci., ^:139-147.
22. Hurtt, W., W.A. Wells and C.P.P. Reid, 1970. Foliar uptake and root
exudation of picloram and 2,4,5-T by selected woody species. Weed
Sci. Soc. Amer., Abstract 145.
23. Morton, H.L., E.D. Robinson and R.E. Meyer, 1967. Persistence of
2,4-D, 2,4,5-T and dicamba in range forage grasses. Weeds 15:268-271.
24. Perry, P.W. and R.P. Upchurch, 1968. Growth analysis of red maple
and white ash seedlings treated with eight herbicides. Weed Sci.,
16:32-37.
25. Slife, F.W., J.L. Key, S. Yamaguchi and A.S. Crafts, 1962.
Penetration, translocation and metabolism of 2,4-D and 2,4,5-T in
wild and cultivated cucumber plants. Weed Sci., 10:29-35.
26. Basler, E., 1964. The decarboxylation of phenoxyacetic acid
herbicides by excised leaves of woody plants. Weed Sci., 12:14-16.
27. Basler, E., C.C. King, A.A. Badiei, and P.W. Santelmann, 1964. The
breakdown of phenoxy herbicides in blackjack oak. Proc. Southern
Weed Conf., 17:351-355.
28. Morton, H.L., 1966. Influence of temperature and humidity on foliar
absorption, translocation, and metabolism of 2,4,5-T by mesquite
seedlings. Weed Sci., 14:136-141.
-------
-21-
29. Fitzgerald, C.H., C.L. Brown and E.G. Beck, 1967. Degradation of
2,4,5-trichlorophenoxyacetic acid in woody plants. Plant Physiol.
42:459-460.
30. Edgerton, L.J. and D.J. Lesk, 1963. Determination of residues of
2,4,5-trichlorophenoxyacetic acid in apples by radioisotopes and
gas chromatographic methods. Proc. Am. Soc. Hort. Sci., 83:120-125.
31. Trevett, M.F., 1964. A request for approval of a contact method of
applying 2,4-D and 2,4,5-T for control of woody weeds in Maine
lowbush blueberry fields. Unpublished data. Cited in Dow
communication dated Jan. 19, 1971.
32. Syracuse University Research Corporation, 1970. 2,4,5-T residues in
rough rice and straw. Unpublished data. Cited in Dow communication
dated January 19, 1971.
33. Duggan., R.E., 1971. Memorandum to Way land J. Hayes. Unpublished.
March 12, 1971.
34. Corneliussen, P.E., 1969. Pesticide residues in total diet samples.
Pesticide Monit. J., .2:140-152.
35. Duggan, R.E., H.C. Barry, and L.Y. Johnson, 1967. Pesticide residues
in total diet samples. Pesticide Monit. J., 1^:2-12.
35a, Martin, P.J. and R.E. Duggan, 1968. Pesticide residues in total
diet samples. Pestiicde Monit. J., ,1:11-20.
36. Dow, 1970. Petitions, Part III, Item 20. Solubilities of 2,4,7,8-
tetrachlorodibenzo-p-dioxin. The Dow Chemical Co., December 8,
1964 (Revised April 1970).
37. Dow, 1970. Petitions, Part III, Item 19. The degradation of
2,3,7,8-tetrachlorodibenzo-p-dioxin by ultraviolet light. The
Dow Chemical Co., May 1970.
-------
-22-
37a. Lynn, G.E., 1971. Photodegradatlon of 2,3,7,8-tetrachlorodibenzo-
p-dloxln. Unpublished work by Dow Chemical. Letter dated
February 1, 1971.
38. USDA, 1970. Progress report on dioxin research. IV. Unpublished
report dated March 25, 1970.
39. Kearney, Philip C., 1970. Chlorinated dioxin research. Presented
before a Joint Meeting on Pesticides, United Kingdom, Canada,
United States. November 5.
-------
-23-
C. Fate in Animals
Fate of 2,4,5-T. Information on absorption, distribution, and
metabolism of 2,4,5-T is not extensive. The most thorough studies are
1/2/
those reported by Erne — — who demonstrated that the triethanolamine
and alkaline salts of 2,4,5-T and 2,4-D were readily absorbed, distri-
buted and eliminated from the body. Rats and pigs given single doses of
100 mg/kg of the amine salt showed plasma half-life values of 3 and 10
hours respectively. Residues in kidney, liver, lungs and spleen some-
times exceeded plasma levels, but there was little indication of penetra-
tion into brain or adipose tissues. The compounds were excreted mainly
via the kidney. With repeated administration plasma levels decreased and
excretion rates increased. Up to 20% of the material in blood was In
erythrocytes. As with single doses, little was found in adipose tissue or
in the central nervous system. Placental transfer was found to be rapid
in swine. Tissue half-times ranged from 5 to 30 hours and were lowest in
rats. There was no apparent retention of either 2,4-D or of 2,4,5-T after
repeated administration.
3/
According to St. John et al.,— when a cow was given 450 mg of
2,4,5-T acid divided among four daily doses, all of the administered
material was excreted in the urine as the salt within 6 days. Zlelinski
4/
and Fishbein— found that a dose of 100 mg/kg of 2,4,5-T in mice was lost
from the body more slowly than were several other herbicides, with disappear-
ance rates ranging between 1 and 4JK of the original dose per hour.
The rate of excretion of 2,4,5-T in man is unknown, but It seems to
be slower than that of 2,4-D. A man who committed suicide with a mixture
of the two compounds had substantial concentrations -of 2,4,5-T in all
organs analyzed but no 2,4-D in any organl/.
-------
-24-
Using massive doses it is possible experimentally to exceed the
ability of domestic animals to eliminate 2,4,5-T and thereby to produce
measurable residues in their tissues. Four or more 250 mg doses of
2,4,5-T given to sheep produced levels of 33 to 113 ppm in fat and
40 to 100 ppm in muscle. The residues were 99% or more in the acid
form regardless of whether the acid form or an ester was fed §1 The
fchemical form of the agent, however, may influence its deposition.
Oral administration of the propylene glycol or butyl ether esters of
2,4,5-T to yearling cattle for 32 weeks at rates of 0.15 and 0.75
mg/kg/day produced no residues greater than those occasionally found
in untreated controls. Subsequently Clark et al., —^ fed 2,4,5-T,
2,4-D and Silvex (2,4,5-trichlorophenoxy propionic acid) to sheep and
cattle at several dietary concentrations for 28 days. Sheep receiving
2000 ppm 2,4,5-T in the diet were found to have muscle tissue residues
of 1.0 ppm when treatment was terminated, and no detectable residue
8/
7 days later. Newton and Norris — analyzed tissues from deer that
had ranged over reforested land treated with 2,4,5-T and found essentially
no residues.
Several factors limit the intake of 2,4,5-T by domestic animals
and man following recommended use of the compound, namely, low rate of
application and breakdown by plants, animals, photochemical degradation
and soil microorganisms. Owing to both the limited nature of prescribed
use and the decomposition that occurs in the environment, 2,4,5-T almost
never reaches a detectable level in human drinking water or food (see
Section I B, pp. 11 and 14). Examination of approximately 11,600 samples
of food offered for retail sale in the United States revealed only five
-------
-25-
with measurable residues, the highest concentration being 0.29 ppm.
9/10/11/
The highest level in potable water was 0.00007 ppm .
12/
Fate of TCDD. Piper and Rose — have reported a preliminary
study of the tissue distribution and disposition of ^C-labeled TCDD
administered as a single oral dose of 0.05 mg/kg to male rats. The
biological half-time for this dose was approximately 20 days, and fecal
excretion accounted for the greater part of the TCDD removal. Three days
after administration 3.1% of the total dose per gram was recovered from
liver and 3.0% of the total dose per gram was contained in fat. The
residual radioactivity in these tissues was not identified and therefore
cannot be assumed to be TCDD. The fact that 8.3% of the dose was
14
recovered from CO2 in expired air indicated that some of the TCDD was
completely metabolized.
The Dow Chemical Co. has recently provided comparative solubility
data on TCDD and p.p'DDT at 24°C, as follows:
FPM of Solvent
TCDD p.p'DDT
corn oil 28 86,000
lard oil 44 86,000
water 0.0002 0.001
Although suggesting a petitioning toward fat, these data clearly indicate
that, unlike DDT, TCDD is so insoluble in fat that it would not be expected
to accumulate in body fat depots in appreciable amounts.
It is concluded from the foregoing that: l) 2,4,5-T is rapidly
excreted in all animals studied using doses in the range of those likely
to be encountered in the environment; 2) 2,4,5-T is not known to be
accumulated in any animal tissues or product used for human food;
-------
-26-
3) 2,4,5-T has been detected in animal tissues or products used for human
food very infrequently and then only in minute quantities; 4) limited data
Indicate that TCDD is also eliminated, at least some by metabolic breakdown,
with a half-life of 20 days; and 5) the solubility of TCDD in fat is limited
which would preclude appreciable accumulation in body fat.
References Cited in Section I C
1. Erne, K., 1966. Distribution and elimination of chlorinated
phenoxyacetic acids in animals. Acta. Vet. Scand., 7:240-256.
2. Erne, K., 1966. Animal metabolism of phenoxyacetic herbicides.
Acta. Vet. Scand., 7^:264-271.
3. St. John, L.E., D.G. Wagner and D.J. Lisk, 1964. Fate of atrazine,
Kuron, Silvex and 2,4,5-T in the dairy cow. J. Dairy Sci.,
47:1267-1270.
4. Zielinski, W.L., Jr. and L. Fishbein, 1967. Gas chromatographic
measurement of disappearance rates of 2,4-D and 2,4,5-T acids and
2,4-D esters in mice. J. Agr. Food Chem., 15:841-844.
5. Curley, A., 1971. Personal communication to Mayland J. Hayes.
6. Clark, D.E., J.S. Palmer and C.H. Ayala, 1970. Residual and
toxicological aspects of 2,4,5-T and an ester in sheep and cattle.
Presented at the meeting of the Pesticide Division, American
Chemical Society and Chemical Institute of Canada, Toronto,
May 28, 1970.
7. Clark, D.E., H.R. Crookshank, R.D. Radeleff and J.S. Palmer, 1971.
Tissue residues of chlorophenoxy acid herbicides in cattle and
sheep. Am, Chem. Soc. Meeting, April 2, 1971.
-------
-27-
6. Newton, M. and L.A. Norris, 1968. Herbicide residues in blacktail
deer from forests treated with 2,4,5-T and atrazine. Western
Soc,. Weed Sci., Proceedings pp. 32-34.
9. Corneliussen, P.E., 1969. Pesticide residues in total diet samples.
Pest. Moult. J., 1}140-152. (Mar.)
10. Duggan, R.E., H.C. Barry and L.Y. Johnson, 1967. Pesticide residues
in total diet samples. Pest. Monit. J., U2-12. (Sept.)
11. Martin, R.J. and R.E. Duggan, 1968. Pesticide residues in total
di£t samples. Pest. Monit. J.,. 1:11-20. (Mar.)
12. Piper, W.N. and J.Q. Rose, 1971. The excretion and tissue
distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the rat.
Unpublished report from Dow Chemical Co. dated March 18, 1971.
-------
-28-
II. TOXICITY OF 2,4,5-T AND TCDD IN ANIMALS AND MAN
Currently available commercial preparations of 2,4,5-T can be
characterized as having at least 95% 2,4,5-T with less than 0.5 ppm
TCDD and no other toxicologically significant compound. Many earlier
studies on the adverse effects of 2,4,5-T employed preparations
containing considerably greater concentrations of TCDD than this, and
others used 2,4,5-T samples of unspecified purity. Toxicological
studies utilizing 2,4,5-T preparations which were not known to conform
to the standards suggested above, nevertheless, have some value because
any error attributable to larger amounts of TCDD would have been toward
the conservative side, that is, would have suggested greater toxicity
than if a purer 2,4,5-T had been used.
A. Nonteratogenic Toxicity.
Of 2,4,5-T. Among the earlier reports of 2,4,5-T toxicity that
did not fully identify the composition of the product under
investigation were the studies of Drill and Hiratzka^ in which oral
LD5q for dogs was estimated to be in excess of 100 mg/kg, and of Rowe
2/
and Hymas— in which the oral to various rodents was found to be
greater than 350 mg/kg. Drill and Hiratzka found no adverse effects in
dogs which were fed 2,4,5-T five times a week for 90 days at dosage
levels of 2.5 and 10 mg/kg. Four dogs were treated at a level of 20
mg/kg 2,4,5-T and died at 11, 49, 59 and 75 days after the first dose.
Rowe and Hymas reviewed the toxicologic information available on 2,4,5-T
at that time, and concluded that the acute lethal oral toxicity, in terms
-------
-29-
of and-19/20 confidence limits, of 2,4,5-T was for male rats 500
(391-640) mg/kg; for male mice, 389 (245-619); guinea pigs, male and
female, 381 (307-472); chicks, male and female, 310, (211-456). The
latter authors also used various commercial formulations of the butyl,
isopropyl and amyl esters of 2,4,5-T in single oral-dose animal-feeding
experiments in rats, chickens and guinea pigs and reported LD^q levels
with 19/20 confidence limits which were all greater than those listed
above. They concluded that oral administration of 2,4,5-T could be
tolerated without adverse effects in doses only slightly smaller than
those which caused toxic effects and stated that this fact demonstrates
that 2,4,5-T has a low degree of chronicity. Palmer and Radeleff—^
found that the propyl glycol butyl ether ester of 2,4,5-T was lethal to
one sheep after 369 daily oral doses of 100 mg/kg and to another sheep
after seven doses of 250 mg/kg. A single cow also succumbed to the
latter dose. The triethylamine salt of 2,4,5-T caused no observed
effect (sheep) after 481 doses of 100 mg/kg/day. The propionic acid butyl
ether ester of 2,4,5-T was lethal to a sheep after 11 daily doses of
100 mg/kg orally and lethal to a cow after 29 such doses. Five daily
250 mg/kg oral doses also killed a cow. Fifty mg/kg/day orally had no
effect after 73 days.
In 1969 an investigation of the carcinogenicity in mice of 120
pesticides and herbicides^; 2,4,5-T was among the compounds tested
which did not cause significant increase in tumors after oral adminis-
tration. The purity or dioxin content of the sample was not described.
This represents the only report of long-term treatment with 2,4,5-T
other than the few farm animals mentioned above. The dose was the maximum
-------
-30-
tolerated dose (zero mortality) determined with single doses, 6 dally
doses, and finally 19 daily doses. The dosage was given by stomach
tube at 21.5 mg/kg from the end of the first through the fourth weeks
and thereafter it was mixed in the diet at 60 ppm of food and continued
until 18 months of age. It Is presumed that all animals survived the
18 month test period although this was not stated in the publication.
Johnson^ has reported acute oral, single dose toxicity studies
on commercial 2,4,5-T in which the LDjq for 2,4,5-T was 500 mg/kg in the
rat and 380 mg/kg in the guinea pig. Ninety-day feeding studies with
2,4,5-T containing 0.5 ppm TCDD were recently reported by McCollister
and Kociba.—^ The acid form was administered to groups of 10 male and
10 female rats at 100, 30, 103 and 0 mg/kg/day. No significant adverse
effects were observed in the groups receiving doses at or below 30
mg/kg/day, but those receiving 100 mg/kg/day showed a depression of
body weight gain, a decrease in food intake and elevated alkaline
phosphatase levels. The males showed slightly increased serum
glutamic-pyruvic transaminase levels and slight decreases in red blood
cell counts and hemoglobin levels. Histological evidence of toxicity
were minor and inconsistant. In an earlier experiment at Dow Chemical Co
the mono-, di-, and tripropylene glycol butyl ether esters of 2,4,5-T
were administered orally to rats over a similar 90-day period at doses
as high as 186 mg of 2,4,5-T acid equivalent per kg per day. At the
highest dose and at 62 mg/kg/day of acid equivalent various evidences of
toxicity developed, but no adverse manifestations attributable to the
agent were detected at dosages of 18,6 or 6.2 mg/kg/day.
8 /
The Dow Chemical Co.— has prepared an extensive health inventory
of 126 manufacturing personnel in an effort to identify adverse effects
-------
-31-
of inhaled 2,4,5-T. The inhalation rate of the agent was estimated to
be 1.6 to 8.1 mg/day per worker, depending on the work assignment, for
periods of up to three years and at total career exposures in excess
of 10,000 mg. The survey indicates that no illness was associated with
2,4,5-T intake. Specifically there was no increase in skin ailments
or of alkaline phosphatase or SGPT levels as compared with controls
having no exposure to 2,4,5-T.
The result was entirely different in a plant where the 2,4,5-T
produced contained a high proportion of dioxin. The latter plant was
9 /
studied by Bleiberg-' in 1964 and again six years later by Poland
et al.-i^ who also reviewed earlier studies in factories in other
countries where TCDD had been a problem. Poland and associates
reported on 73 employees whose health was found to be improved
compared to that of workers in the plant six years earlier. Eighteen
percent of the men had suffered moderate to severe chloracne, the
intensity of which correlated significantly with the presence of
residual hyperpigmentation, hirsutism, and eye irritation and with a
high score on a test indicating a manic reaction. The chloracne did not
correlate with job location or duration of employment at the plant or with
coproporphrin excretion. One of the men had uroporphyrinuria but,
unlike the situation six years earlier, no porphyria could be found.
Systemic illness such as may be produced by TCDD was markedly less
than that reported in previous studies of 2,4,5-T plants and probably no
greater than expected in unexposed men of the same age.
Dogs and rats tolerate oral intake of 2,4,5-T at a rate of 10
mg/kg/day or higher without detectable clinical, biochemical, or
pathological change. The tolerance limit of people is not known but
-------
-32-
no injury was detected in workers with the highest recorded, prolonged
exposure in a factory making low-dioxin 2,4,5-T, i.e., 8.1 mg/man/day
or about 0.11 mg/kg/day®/. In view of the small and highly infrequent
occurrence of residues of 2,4,5-T in human food (see Section IB), it
is clear that exposure from this source is too small to measure
accurately. Thus, although it is impossible to estimate how much
greater the 2,4,5-T exposure of workers is than the exposure of the
general population, it is clearly much greater than the corresponding one
for DDT—In fact, exposure to 2,4,5-T is trivial even for persons
who daily eat unpolished rice.
The very small number of cases in which human ingestion of 2,4,5-T
led to clinical illness offer no information on the minimal dosage of
the compound that is toxic to man. In animals, however, the toxicity
of 2,4,5-T is similar to that of 2,4-D, consequently some information
on 2,4-D is of interest. When 2,4-D was investigated as a possible
treatment for disseminated coccidiodomycosis, the patient had no side-
effects from 18 intravenous doses during 33 days; each of the last 12
doses in this series was 800 mg (about 15 mg/kg) or more, the last
being 2000 mg (about 37 mg/kg). A 19th and final dose of 3600 mg
(67 mg/kg) produced mild symptoms-^-^ • Suicidal ingestion of a
quantity of 2,4-D as a single dose known to be greater than 6500 mg
13 /
(in excess of 90 mg/kg) was fatal— •
Butler"*'—has reviewed Fish and Wildlife Service studies of
pesticide and herbicide effects on marine organisms. Several 2,4,5-T
derivatives were examined (TCDD content was not known). A 96-hour
exposure of oysters to the polyglycol butyl ether esters of 2,4,5-T at
a concentration of 0.14 ppm in the water caused a 50^ decrease in shell
-------
-33-
growth rate, with recovery in one week. The 24-hour LD^q of this ester
to juvenile estar^ine fish was 0.32 ppm. A concentration of 2,4,5-T
acid at 2 ppm caused no decrease in growth after 96 hours. A level of
50 ppm 2,4,5-T was not lethal to juvenile mullet and killifish in 48
hours, and 1 ppm was without effect on shrimp in 48 hours. It is thus
apparent that aquatic species tolerate higher concentrations of 2,4,5-T
than have been reported in water samples taken from heavily sprayed
areas (see Section I B, pp. 11-12).
It is concluded from the foregoing that: 1) most species tested
can survive a single oral dose in excess of 100 mg/kg and several,
excepting the dog, can survive daily treatment for a number of days at
this level or higher; 2) dogs die after 11 to 75 doses at the rate of
20 mg/kg/day and rats show toxic signs at repeated daily doses of
100 mg/kg; both species tolerate 10 mg/kg/day without detectable
effect; 3) no proven instance of toxicity associated with 2,4,5-T
intake in man has been found in industrial or agricultural workers
known to have had repeated, relatively high levels of exposure to
2,4,5-T of low dioxin content; and 4) the safety factor for the general
population is estimated to be several orders of magnitude greater than
that of 2,4,5-T factory workers.
Of TCDD. TCDD has been recognized as a contaminant of commercial
preparations of 2,4,5-T for several years; however, there has been no
extensive study of its toxicity. According to Johnson!^/ the acute
LD^q for TCDD is 0.022-0.045 mg/kg in the rat and 0.0006 mg/kg in
the guinea pig. Because of the high potency of this compound in
the guinea pig, these experiments were repeated and confirmed by
-------
-34-
Dow Chemical Co. Some information on the toxicity of TCDD is available
from a study of TCDD teratogenic effect in the rat (see Section II B,
p. 44). No evidence of clinical effect on the dams was found at doses of
0.0005 mg/kg/day, although embryotoxicity appeared in litters of females
given 0.000125 mg/kg/day. Some vaginal hemorrhage was caused by 0.002
mg/kg/day and 0.008 mg/kg/day caused pallor and debilitation.
As far as occupational exposure is concerned, it is clear that any
danger of 2,4,5-T formulations resides in their TCDD content. The primary
manifestation of industrial TCDD intoxication is chloracne, an easily
detected, in fact highly disfiguring, dermatitis. It is significant that
this condition has not been a problem in factories producing 2,4,5-T
with a low content of TCDD, nor among persons who apply the herbicide as
a part of their regular occupation. It is therefore highly unlikely
that exposure to traces of TCDD will have any effect on persons who use
2,4,5-T formulations occasionally or who merely encounter possible traces
of it in the environment.
Data are too limited for a firm conclusion but there is no evidence
to suggest that TCDD as a contaminant in 2,4,5-T is likely to be encountered
by animal or man in sufficient dosage to cause toxic reactions.
References Cited in Section II A
1. Drill, V. A. and T. Hiratzka, 1953. Toxicity of 2,4-dichlorophenoxy-
acetic acid and 2,4,5-trichlorophenoxyacetic acid. A Report on
Their Acute and Chronic Toxicity in Dogs. AMA Arch. Indust. Hyg.
Occup. Med., _7:61-67.
-------
-35-
2. 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 livestock associated with their use. Am. ,J. Vet. Res., 15:622-629.
3. Palmer, J.S. and R.D. Radeleff, 1964. The toxicologic effects of
certain fungicides and herbicides on sheep and cattle. Ann. N.Y.
Acad. Sci., 111:729-736.
4. Xnnes, J.R.M., B.M. Ulland, M.G. Valerio, L. Petrucelli, L. Fishbein,
E.R. Hart, A.J. Pallotta, R.R. Bates, H.L. Falk, J.J. Gart, M. Klein,
1. Mitchell and J. Peters, 1969. Bioassay of pesticides and
industrial chemicals for tumorigenicity in mice: A preliminary note.,
J. Nat'l Cancer Inst., 42:1101-1114.
5. McCollister, Susan, B. and R.J. Kociba, Sept. 18, 1970. Results of
90-day dietary feeding study on 2,4,5-trichlorophenoxyacetic acid
(2,4,5-T) in rats. Dow Chemical Co. Internal report.
6. Johnson, J.E. Paper presented at Symposium of Institute of
Biological Sciences, Bloomington, Indiana, August 26, 1970.
7. Dow Chemical Co., Internal communication, Nov. 27, 1961. Results
of 90-day dietary feeding studies on Dowanol 97B ester 2,4,5-T in
rats.
8. Dow Chemical Co., letter with attachment from C.G. Kramer to
J.E. Johnson, April 7, 1970 (see Dow Petition).
9. Bleiberg, J., M. Wallen, R. Brodkin and I. Applebaum, 1964. Industrially
acquired porphyria. Arch. Derm., 89:793-797.
10. Poland, A.P., D. Smith, G. Metter and P. Possick, 1971. A health
survey of workers in 2,4-D and 2,4,5-T plant, with special
attention to chloracne, porphyria cutanea tarda, and psychologic
parameters. Arch. Environ. Health, 22:317-327.
-------
-36-
11. Laws, E.R., Jr., A. Curley and F.J. Biros, 1967. Men with intensive
occupational exposure to DDT. Arch. Environ. Health, 15:766-775.
12. Seabury, J.H., 1963. Toxicity of 2,4-dichlorophenoxyacetic acid for
man and dog. Arch. Environ. Health, ]j202-209.
13. Nielsen, K., B. Kaempe and J. Jensen-Holm, 1965. Fatal poisoning
in man by 2,4-dichlorophenoxyacetic acid (2,4-D): Determination
of the agent in forensic materials. Acta Pharmacol. Toxicol.,
22:224-234.
14. Johnson J.E., 1970. Symposium ox: Possible Public Health Implications
of Widespread use of Herbicides, AIBS Meeting, August 26, 1970.
15. Butler, P.A., 1963. Pesticide-Wildlife studies; A review of fish
and wildlife service investigations; Circular 167. Commercial
Fisheries Investigations.
16. Butler, P.A., 1964. Pesticide-wildlife studies, 1963; A review
of Fish and Wildlife Service investigations during the calendar
year, circular 199. Commercial Fisheries Investigations.
-------
-37-
B, The Teratogenic Potential of 2,4,5-T
1. Scope of embryotoxicity. Teratology is the science dealing
with the causes, mechanisms, and manifestations of deviant structural
or functional development. Such deviation can be the result of mutation
in which case the defect may be transmitted by heredity, or it may be
induced by unfavorable environmental conditons during the developmental
period: usually during the formative stages of the embryo, less often
during functional maturation of the fetus, and possibly even during the
final stages of development postnatally.
Many types of adverse factors in the environment have been shown
to initiate abnormal development when applied during pregnancy in
laboratory animals, including: certain dietary deficiencies (mostly of
vitamins); many classes of chemicals, including some drugs; various
physical factors such as ionizing radiation, drastic temperature changes,
and alterations in atmospheric gases; a few viral infections; some
maternal endocrine and metabolic imbalances; and undoubtedly some
combinations of these.
Relatively few of these experimentally demonstrated teratogenic
agents have been shown to be effective in man. High doses of ionizing
radiation such as are used in therapy for cancer or emanate from
nuclear explosions are well known to be teratogenic when applied during
early human pregnancy. Two infectious agents, rubella and cytomegalic
viruses, have been clearly implicated. Three types of drugs - thalidomide,
folic acid antagonists, and androgenic hormones - have been established
as causes of malformations in man and a few others are suspected but are
not at this time proven to be teratogenic. Maternal metabolic diseases
-------
-38-
such as endemic cretinism, diabetes, phenylketonuria, and adrenal hyper-
plasia account for a small percentage of human developmental disease. One
environmental pollutant, methylmercury, proved to be teratogenic for man
when it reached high concentrations in certain water Japan from which
fish were eaten as a large part of the diet.
Adverse effects on development are difficult to evaluate because
they vary greatly in degree and type. Collectively these effects can
be designated as embryotoxic because they most often have their inception
in the embryo and include such manifestations of toxicity as lethality,
teratogenicity, prenatal growth retardation, and postnatal functional
deficiencies. Few attempts are made to evaluate functional deficiency
except as it may be reflected in postnatal survival data. On the other
hand embryolethality, teratogenicity, and growth retardation can under
laboratory conditions be readily detected and quantitated. Difficulty
is often encountered, however, when all three toxic manifestations are
simultaneously evaluated, since the phenomena involved are rarely
affected to the same degree by a given embryotoxic agent. Although most
chemical substances probably could be shown to be teratogenic under
suitable experimental conditions and all could be shown to have some toxic
effects when dosage is sufficiently high, some would be more strongly
teratogenic, others would be predominantly embryolethal, whereas still
others would tend mainly to cause intrauterine growth retardation.
While these toxic manifestations vary directly with dosage, they may not
show parallel dose-response effects. Any one of the three may begin to
appear at a somewhat lower dose than either of the others. Lethality is
probably the most variable from one agent to another, sometimes appearing
at low doses and increasing slowly as dosage is increased, sometimes
-------
-39-
appearing abruptly at doses already causing considerable teratogenicity
and growth retardation. Teratogenicity is probably the most predictable
of the three in' that it usually has an easily demonstrable no-effect
range of dosage and a steep dose-response curve once teratogenicity
begins.
These variations in embryotoxic manifestations are particularly
troublesome when it is necessary to establish the highest no-detectable-
effect or the lowest effect level of dosage. A level that has no detec-
table teratogenic effect may already be in the effect range for lethality
or growth retardation. The solution to this dilemma requires either that
one form of embryotoxicity be selected as the criterion of interest or
that the one showing the lowest effect level arbitrarily be accepted in
setting tolerance limits. Such complications have been encountered in
attempting to evaluate 2,4,5-T results, particularly in those experiments
in which data on all embryotoxic manifestations were not reported. In
some experiments only results pertaining to teratogenicity were given and
In these cases dose-response evaluation had to be limited accordingly.
For others, the Advisory Committee has tried to extrapolate the data in
such a way as to approximate a no-effect level, i.e., the largest dose
at which no increased lethality, teratogenicity, or growth retardation
occurred.
2. Data from laboratory animals. In 1964, the National Cancer
Institute contracted with Bionetics Research Laboratories to perform
screening studies for carcinogenicity and teratogenicity on a number of
pesticides and industrial chemicals. The results, released in October
1969, indicated that of the 53 compounds examined, 2,4,5-T in particular
showed embryotoxicity in two stocks of mice at a dose of 113 mg/kg/day
-------
-40-
when given for several days during organogenesis. Cleft palate, cystic
kidneys, intestinal hemorrhage and fetal mortality occurred in higher
percentages of treated than of control animals although a clear dose-
response relation was not evident at lower doses. The results have been
reviewed elsewhere UU and published in summary form and therefore
require no extensive discussion here. Certain inconsistencies in the
data likewise need no comment because the sample 2,4,5-T used
in the Bionetics study is known to have been contaminated with 27 + 8
ppm of TCDD and the results can no longer be considered a valid indi-
cation of the teratogenicity of the herbicide. This contaminant
itself has since been shown to have teratogenic and embryolethal properties,
as will be discussed later. Despite the limitations of the original
Bionetics study, it served two useful functions, in: 1) highlighting
the possibility that herbicides may cause previously unknown adverse
effects on nontarget organisms, including mammals, and 2) emphasizing
the need for more thorough safety evaluation of such compounds before
they are approved for widespread use.
The discovery that the contaminant TCDD was present in the herbicide
used in the Bionetics study made it necessary to determine whether the
reported teratogenicity was caused by 2,4,5-T or TCDD. Additional
studies relating to this question have been completed at the Dow Chemical
Company, the Food and Drug Administration, the National Institute for
Dental Research, the National Institute of Environmental Health Sciences,
the Department of Agriculture Animal Disease and Parasite Research Division,
the Food and Drug Directorate of Canada, Bionetics Research Laboratories, and
-------
-41-
the Children's Hospital Research Foundation of Cincinnati, on rats, mice,
hamsters, rabbits, sheep and rhesus monkeys using samples of 2,4,5-T
containing known concentrations of TCDD as well as relatively pure samples
of TCDD.
These studies are summarized below, species by species and separately
for 2,4,5-T and TCDD, Insofar as the original reports permits, data are
summarized on maternal toxicity, e.g., death or failure to show normal
weight gain during pregnancy; as well as on embryotoxicity and fetal
toxicity, e.g., prenatal death teratogenesis, intrauterine growth
retardation, and perinatal signs of other toxicity. It is recognized
that fetal death, either individual or as whole litters may also reflect
maternal toxicity, and therefore may be difficult to interpret.
2,4,5-T in rats. Sprague-Dawley rats at Dow Chemical Co. were
fed 1, 3, 6, 12, or 24 mg/kg/day of 2,4,5-T containing 0.5 ppm of TCDD
on days 6 through 15 of pregnancy No maternal death or reduced
maternal weight gain during pregnancy was noted. There was also no
increase in prenatal mortality, only slight impairment of fetal growth
in a few cases ac the 24 mg/kg dosage, and no malformations. The poor
ossification of the 5th sternebra noted in some cases was probably a
sign of mild transient retardation of skeletal development and of no
known significance. Pregnant rats of the same stock were fed 50 or 100
mg/kg/day of "commercial production grade" 2,4,5-T containing 0.5 ppm
TCDD on days 6 through 15 of gestation, or 100 mg/kg/day on days 6
through 10 The only effects observed after the lower dose were
intestinal hemorrhage in one of 203 offspring and a slight increase in
-------
-42-
frequency of delayed ossification of skull bones. The larger dose
produced 83% maternal death and early death (resorption) of the entire
litters in most of the surviving pregnant animals. Surviving offspring
were reduced in size but had no anomalies except delayed ossification of
skull bones, and this retardation was overcome within three ^eeks after
birth.
Sprague-Dawley rats at the National Institute of Dental Research ^
were given orally 60, 80, 100, or 120 mg/kg/day of 2,4,5-T containing 0.4 ppm
TCDD over various periods of consecutive days during the middle third of
gestation. Maternal toxicity data were not reported. No treatment greatly
increased the intrauterine mortality rate and many had no effect. Prenatal
growth retardation was not mentioned. Apparently the offspring were
examined only for external malformations and those of the oral cavity.
Very few with such defects were found (7 of 1500 from females treated
at susceptible periods). A mixture of 2,4,5-T and 2,4-D produced one case
of cleft palate. To rule out the possibility that the chemical might
not be reaching the fetus, millipore filters soaked with 0.05, 0.1, 0.11,
or 0.125 mg 2,4,5-T were applied to amniotic sacs on day 12, 13, 14, 15, or
16 of gestation. Of 68 fetuses surviving to the time of examination two
had cleft palate, one had a tail defect, four had limb defects, and others
were small or edematous. A second study of this type yeilded one possible
limb defect and four possible tail defects in 68 survivors.
Rats of the FW-49 stock in Germany recently were given 25, 50, 100,
or 150 mg/kg/day of 2,4,5-T (containing £0.02 ppm TCDD) on days 6
12/
through 15 of gestation (cited by Tschirley —' ) . Macro-and Microscopic
examination revealed no signs of teratogenicity even with the highest
-------
-43-
dosages. There was an increase in the prenatal mortality beginning at
the 50 mg/kg dose and a reduction in the mean fetal weight beginning at
the 100 mg/kg dose. Complete details of the study were not given.
Charles River rats at the National Institute of Environmental Health
13/14/15/
Sciences received samples of 2,4,5-T CO.5 and 30 ppm TCDD) at
the rate of 10 to 80 mg/kg/day orally or subcutaneously on days 6 through
15 of gestation, or 2,4,5-T (£ 0.05 ppm TCDD) at the rate of 150 mg/kg/day
subcutaneously on days 14 and 15 of gestation. The 80 mg/kg dose was
stated to be the maternal 1D^^ dose but data were not presented. The
80 and 150 mg/kg doses caused a reduction in maternal weight gain and
increased prenatal mortality, but fetal weight was unaffected. A low
incidence of fetal kidney anomalies was noted, but could not be attributed
with confidence to the treatment. In addition, pregnant females were
fed 50 mg/kg of 2,4,5-T (< 0.05 ppm TCDD) and allowed to deliver. The
offspring examined periodically for 3 weeks postnatally during which
time mortality, weight gain, and general development did not differ from
those of control animals.
16/
Wistar rats at the Food and Drug Directorate of Canada — were
fed dosages of 25, 50, 100, and 150 mg/kg/day of 2,4,5-T acid or of
2,4,5-T butyl ester containing ^0.5 ppm TCDD on days 6 through 15 of
gestation. No apparent adverse effects on pregnant females were noted,
but fetal weight was reduced. At the largest dosage there was an
apparent increase in the frequency of "spontaneously occurring" skeletal
anomalies. The largest dose of the acid form killed 3 of 8 pregnant
females and reduced maternal weight gain but lower doses were without
maternal toxicity. Intrauterine death was increased at 50 mg/kg and
was pronounced at larger dosages, at which levels weight of surviving
-------
-44-
fetuses was reduced. At the higher doses there was also increased
skeletal variations some of which did not occur spontaneously in
controls. Postnatal survival of young was not adversely affected
by maternal dosage with 100 mg/kg. The 2,4^5-T butyl ester was without
effect.
The foregoing rat experiments all involved repeated daily treatment
of pregnant females with 2,4,5-T. The possibility exists, that owing
to maternal homeostatic mechanisms, e.g., inducation or inhibition of
metabolic enzymes, the most sensitive teratological test would be one
involving a single treatment during early organogenesis. To test this
possibility rat experiments were carried out at the Institute of
Developmental Research, Children's Hospital Research Foundation of
17/
Cincinnati — . Using a sample of 2,4,5-T containing 0.5 ppm of TCDD,
groups of pregnant Wistar rats were treated by gavage on day 9 of
gestation with doses of 100, 200 or 400 mg/kg in 0.2% carboxymethyl-
cellulose. Day 9 is generally regarded as the time at which the rat
embryo is teratogenically most susceptible.
Whole Litters continuing to dav 20
Dose Days of
mg/kg treatment
litters
resorbed
Total
implants
% dead or
resorbed
mean wt.of
survivors
% survivors
malformed
Control^ none
0/40
509
5.4
3.7 gin
1.9
Control 9
0/45
558
7.2
3.8
0.8
20 7-13
0/11
170
8.8
3.7
0.7
100 9
0/11
170
9.0
3.7
1.9
200 9
0/11
156
11.5
3.8
5.1
400 9
2/10
122
25.4
3.2
11.0
Cumulative untreated control over past 4 years.
^Cumulative vehicle treated control (per gavage) over past 4 years.
%ypes of malformations: anophthalmia, microphthalmia, curly or short
tail, hydronephrosis, ectopic testes, agnathia.
-------
-45-
The data in the accompanying table indicate that a single dose of 100
mg/kg at a highly sensitive time in rat embryogenesis did not cause an
increase in abnormal development or a decrease in intrauterine growth
but did cause a slight increase in intrauterine death. This effect was
accentuated at higher doses and a moderate increase in malformations above
control levels was also noted. Intrauterine growth was affected only at
400 mg/kg, a dose sufficient to cause severe embryotoxicity as evidenced
by complete resorption of 2 of the 10 whole litters.
In summary, it appears that rat strains vary considerably in their
susceptibility to the embryotoxic effects of 2,4,5-T. A low level of
teratogenicity may appear in some strains when repeated dosage exceeds
100 mg/kg/day, or single dosage on day 9 is at 200 to 400 mg/kg of maternal
weight. Some increase in intrauterine death and decrease in intrauterine
growth, as well as maternal toxicity, was sometimes noted at lower daily
dosage, e.g., 50 mg/kg.
TCDD in rats. Rats have been treated during pregnancy with TCDD in
18/
appreciable dosage in only two laboratories. At the Dow Chemical Co.
pregnant Sprague-Dawley rats received 0.00003, 0.000125, 0.0005, 0.002,
or 0.008 mg/kg/day of dioxin (91% TCDD) orally on days 6 through 15 of
gestation. Only one maternal death occurred and maternal weight gain
was depressed only by the largest doses. Prenatal mortality was greatly
increased at the 0.002 mg/kg dosage and all fetuses were killed at the
0.008 mg/kg level. Petal weight was greatly reduced at 0.002 mg/kg and
somewhat reduced at lower doses, Only two offspring had possible malforma-
tions of the tail and limbs. Edema and intestinal hemorrhage were observed
in some offspring of females treated with 0.000125, 0,0005, or 0.002 mg/kg.
9/
In a second Dow study — pregnant rats of a stock of unstated origin received
-------
-46-
by an unstated route 50 rag/kg/day of "pure" 2,4,5-T (probably containing
0.05 ppm TCDD) to which was added 0.00001, 0.00003, 0.00006, 0.000125,
0,0005, or 0.001 mg/kg/day of TCDD on days 6 through 15 of gestation.
Cleft palate occurred in ten litters, mostly in those receiving the
2,4,5-T plus 0.0005 or 0.001 mg TCDD. The frequency of offspring with
cleft palate, as well as procedural details and toxicity were not
described.
Charles River rats at the National Institute of Environmental Health
14/
Sciences — received TCDD subcutaneously 0.0005 mg/kg/day on days 6
through 10 of gestation, or 0.002 mg/kg/day on days 9 and 10 or 13 and
14 of gestation. No malformations or excessive fetal mortality were
noted; but various possible kidney anomalies and several instances of
intestinal hemorrhage occurred. Thus, TCDD given to pregnant rats
caused embryolethality and occasional teratogenicity at doses below the
maternal toxic level.
2,4,5-T in mice. Mice of CD1, C57BL/6J and DBA/2J strains received,
subscutaneously, 50, 100, 113, 125, or 150 rag/kg/day of 2,4,5-T containing
-------
-47-
anomalies, types unspecified, was increased above the low level of
background occurrence by the 2,4,5-T containing 0.05 ppm TCDD,
but not by the 2,4,5-T containing 0.5 ppm TCDD. In general, these mice
showed a low level of teratogenicity at 100 mg/kg/day during embryogenesis,
and some embryolethality and decreased fetal weight at lesser doses.
Moore found no appreciable difference in teratogenic and embryolethal
potential between 2,4,5-T as free acid and its butyl, isooctyl and butyl
ether esters at approximately molar equivalent dosage in-niice.
Mice of the NIH all—purpose albino stock were given subcutaneously
113 mg/kg/day of 2,4,5-T containing 0.4 ppm TCDD or 113 mg/kg/day of
a mixture containing 50% 2,4,5-T and 40% 2,4-D ("Orange") usually on
days 6 through 14 of gestation at the National Institute of Dental
Research Cleft palate occurred in 9 of 141 offspring, but no
data regarding maternal toxicity and other fetal effects were reported.
In a recent study made by the Bionetics Research Laboratories,
commissioned by Hercules Incorporated, CD1 mice were injected subcut-
aneously on days 6 through 15 of gestation with 100 mg/kg/day of 2,4,5-T
supplied by the Dow Chemical Co. and Hercules Inc. No maternal death
seems to have occurred and maternal weight gain was unaffected. Intra-
uterine mortality was not increased but mean fetal weight was slightly
reduced. The only malformation that occurred was cleft palate and its
frequency was 11.1% (27/243) with the Dow sample and 1.3% (3/235) with
the Hercules sample. Both products had <0.5 ppm TCDD.
TCDD in mice. TCDD given to mice at 0.001 or 0.003 mg/kg/day
subcutaneously on days 6 through 15 of gestation did not affect fetal
mortality, maternal weight gain, or fetal weight, but did produce low
frequencies of cleft palate in the three mouse lines used in the
-------
-48-
Natlonal Institute of Environmental Health Sciences study A3/JA/ •
In one experiment 2,4,5-T (100 mg/kg) and TCDD (0.001 mg/kg) given
together apparently produced no greater frequency of cleft palate than
when each was given alone. TCDD greatly increased the background rate
kidney anomalies, especially in C57BL mice. Thus the limited data
indicate that TCDD has some teratogenic potential in mice at doses even
lower than those causing appreciable intrauterine death.
2,4,5-T in hamsters. Golden hamsters of a commercially obtained
stock were treated orally on days 6 through 10 of gestation with 20-100
mg/kg/day of 2,4,5-T from seven sources, at the Food and Drug Administra-
20/21/
tion Four of the samples contained 45, 2.9, 0.5 and 0.1 ppm
TCDD, respectively, and three contained no detectable TCDD. Information
on maternal toxicity was not given. Petal mortality was greatly increased
by the TCDD-containing 2,4,5-T samples and its frequency was usually
directly related to both 2,4,5-T dosage and dioxin content; but it was
also moderately high and dose-related after 2,4,5-T containing no detect-
able dioxin. The mean weight of surviving fetuses was unaffected or only
mildly so for the different samples. A low to moderate incidence of
gastrointestinal hemorrhage was observed, but this was probably not
developmental in origin. Malformations were noted in offspring exposed
to 2,4,5-T containing TCDD or not, but their frequency was usually higher
after 2,4,5-T containing dioxin than after 2,4,5-T that did not. No
malformations were produced by 2,4,5-T alone below the 100 mg/kg dose,
whereas all dosages of dioxin-containing 2,4,5-T produced malformations.
Very few malformations (cleft palate, 2 cases, and ectopic heart, 1 case)
resulted from use of dioxin-containing 2,4,5-T, and only at 100 mg/kg.
-------
-49-
The most frequent defects, poorly characterized as "bulging eyes" and
"poor head fusion", occurred in low percentage (15.8% and 11.4%, respect-
ively) after 2,4,5-T with or without TCDD. Some apparent discrepancies
were present in the calculations of the malformation rates. In addition
150 mg/kg/day of a recrystalized and extracted 2,4,5-T was used 22J and
produced a high fetal mortality rate but no malformations.
TCDD in hamsters. Hamsters were given dioxin (21% tri, 53%
tetra CDD) orally at 0.00013, 0.002 or 0,0091 mg/kg/day on days 6
22/
through 10 of gestation at the Food and Drug Administration — . Maternal
toxicity was not mentioned. Mean fetal weight was reduced only at the
two highest dosages. Eye anomalies and prenatal mortality were most
frequent at the highest dose. Gastrointestinal hemorrhage was noted at
the 0.0005 and 0.002 mg/kg doses.
2,4,5-T in rabbits. New Zealand white rabbits were treated orally
with 10, 20, or 40 mg/kg/day of 2,4,5-T containing 1 ppm TCDD on days
6 through 18 of gestation at Dow Chemical Co. —^. No deaths of
pregnant females occurred, and maternal weight gain and fetal mortality
and weight were unaffected. No congenital malformations were noted and
developmental variations were not increased in frequency.
2,4,5-T in sheep. Sheep were fed 100 mg/kg/day of Dow production
2,4,5-T or of Dow production 2,4,5-T propyleneglycolbutylether ester on
days 14 through 36 of pregnancy at the Department of Agriculture Animal
9/
Disease and Parasite Research Division ~~ . Two of 19 ewes died on days
35 and 36 of pregnancy, but their fetuses were normal. The other 17
delivered normal offspring at term. No further details were provided.
2,4,5-T in rhesus monkeys. The Poisons and Pesticides Board of
-------
-50-
23/
Sweden has commissioned a study in pregnant rhesus monkeys —' at doses
of 5, 10, 20 and 40 mg/kg given three times per week for 4 weeks between
days 20 and 48 of gestation. The sample of 2,4,5-T contained 0.5 ppm of
TCDD. Twelve fetuses removed by hysterotomy at 100 days of gestation
from females treated with one of the three lower doses (4 pregnancies
each dose), were developmentally normal and fell within the range, of
weight for untreated fetuses of this age. Two of 4 pregnant females
treated with the highest dose yielded normal fetuses and the other 2
have not been hysterotomized at this writing but are still pregnant.
One-femal treated at this level aborted on day 61 of gestation and the
conceptus was too macerated for examination. Abortion rate among
untreated females in this colony is about 1% prior to day 100 of gestation.
Summarizing available data on exposure of pregnant laboratory
animals, it is notable that rats were used most often and under the
widest variety of conditions. Pregnant females of several stocks
received orally administered low-dioxin-content 2,4,5-T in doses up to
400 mg/kg for durations varying from single treatment to periods includ-
ing much of embryonic development. In the studies in which dosage was
kept below the toxic level for the pregnant females malformed offspring
rarely occurred, and at higher dosages only a low teratogenic potential
was revealed. Results of rat studies with TCDD were variable. In two
of three experiments very few malformed young occurred, but in the third
an appreciable incidence of cleft palate was reported.
Mice proved to be more susceptible than the other species to the
embryotoxic effects of both 2,4,5-T and TCDD. Both compounds produced
low to moderate frequencies of cleft palate in all stocks tested but
-------
-51-
they did not appear to be more teratogenic when given together than
when given separately. Hamster studies with large doses of 2,4,5-T
containing no detectable or low concentrations of dioxin (0.1 and 0.5
ppm) produced significant fetal mortality but relatively few instances
(14/760 = 1.8%) of maldevelopment. Trials with high-dioxin-content
2,4,5-T (2.9 and 45 ppm) also caused appreciable fetal mortality but
moderate frequencies of anomalies (16/209 = 7.6%).
Based on these data it can be concluded that: 1) doses of low-
dioxin-content 2,4,5-T and of TCDD below the level producing maternal
toxicity were without significant effect on prenatal development,
producing little or no embryotoxicity in rats, rabbits, hamsters, sheep,
and rhesus monkeys, and 2) these chemicals were more embryotoxic in mice,
producing a low to moderate frequency of a specific malformation, cleft
palate. The significance of the finding that TCDD in mice increased
certain anomalies of the kidney, which occurred in low frequency in
controls, can only be resolved by further investigation.
3. Human exposure during pregnancy. Reports have appeared in
the news media that the use of 2,4,5-T was associated with an increased
occurrence of congenital malformations and/or stillbirths in human beings
in Vietnam; Globe, Arizona; and Sweden.
Vietnam. Because of the increased use of several defoliating
chemicals by the United States Military in South Vietnam during the past
several years, particular concern was aroused by the reports in Viet-
namese newspapers between June 26 and July 5, 1969 of human birth defects
attributed to these chemicals. Two surveys have been undertaken to
evaluate the situation. One was conducted by Dr. R. T. Cutting, U. S.
-------
-52-
Army Medical Research Team (Walter Reed Army Institute of Research),
Dr. Tran Hun Phuoc, Ministry of Health, Government of the Republic of
Vietnam, and three collaborators from the Military Assistance Command,
24/
Vietnam. A report was issued in December 1970 — and will be referred
to here as the Army report. A second survey was recently made by the
Herbicide Assessment Commission (HAC) of the American Association for
the Advancement of Science, consisting of Drs. M. S. Meselson, A. H.
25/26/
Lesting and J. D. Constable
The Army study surveyed obstetrical records mostly for the years
1960-69 of 22 provincial, district, and maternity hospitals in 18 cities
and other areas in various geographical localities. In most hospitals
the records consisted of daily summary ledgers, prepared by the chief
midwives, and contained such relevant information as the age and parity
of the mothers and the sex, weight, and general condition at birth of
the babies. Space was provided for additional remarks concerning
maternal or infant complications. In three hospitals such ledgers were
not kept but instead individual records were available. In the hospital
yielding the largest number of births, the Tu-Du Maternity Hospital in
Saigon, as system of automatic data processing existed, which provided
for separate recording of numerous categories of malformations.
Almost half a million births were included in cumulative records,
and the overall recorded stillbirth and congenital malformation rates
for the entire period were found to be 33.7 and A.9 per 1000 livebirths,
respectively. Attempts were made to analyze the information by geograph-
ical area, by year, and by intensity of herbicide spraying. The findings
can be summarized as follows. (1) In four geographical regions - capital,
-------
-53-
coastal, interior, and delta - the rates per 1000 livebirths of still-
birth and congenital malformation were 32.5 and 5.8, respectively, in
the capital area, and 36.7 and 2.9 in the three remaining areas. The
differences in these rates may be attributable to better maternal and
neonatal care, or to more competent or thorough examination for congenital
malformations in the capital area. (2) The rates for stillbirths de-
clined and for congenital malformations remained unchanged during this
10-year period. (3) The only differences in these rates between the
years 1960-65 and 1966-69, periods of relatively light and heavy defoliant
spraying, respectively, was a downward trend (from 36.1 to 32.0 for still-
births, and from 5.5 to 4.5 for congenital malformations). (4) There
were no consistent differences between heavily and lightly defoliant-
sprayed areas.
For the most part, however, the possibility of meaningful inter-
pretations of the results of the Army study were precluded by their
several limitations. First, it is obvious that only a fraction of the
total births that occurred during these years were included in the records
examined by the survey team. The report states that "RVN [Republic of
Vietnam] officials estimate that currently only 70% of all births are
reported to the MOH [Ministry of Health]" (emphasis added). The«New York
Times Encyclopedic Almanac for 1971 (p. 877) gives the estimated popula-
tion of South Vietnam for 1970 at 18 million and the birth rate as 35-
42 per 1000 population, which would yield between 630,000 and 750,000
27/
births in 1970 — . The last complete year for which records were
examined by the Army survey, 1969, yielded a total of 87,153 births.
Also the births that were included in the Army survey were far
-------
-54-
from evenly distributed throughout the country, the three capital-area
hospitals contributing over 67% of the total. In addition, the Chinese,
27/
who comprise a significant fraction of the population (over one million)— ,
were probably completely omitted since, as was stated by the Army report,
they did not attend the hospitals surveyed. Finally, any hope of relating
the results to variations in the degree or geographical region of herb-
icide spraying was frustrated by a number of factors. For example, changes
in the local practices of referring difficult obstetrical cases to pro-
vincial hospitals, determined by availability of trained personnel in the
centers, and increasing with gradual improvement in transportation and
security, probably greatly influenced stillbirth and malformation rates in
specific hospitals.
Probably most significant was the fact that populations most
heavily exposed to 2,4,5-T were those most likely to be underrepresented
in the Army survey or to be inadequately dealt with when recorded. Thus,
as the HAC report stated, the bulk of 2,4,5-T used in Vietnam was sprayed
in relatively remote and sparsely populated areas; the population directly
exposed to 2,4,5-T probably did not exceed 5% and may have been 1% or less
of the total population of Vietnam; and very likely a significant pro-
portion of the exposed population consisted of Montagnard people, whose
births usually did not occur in hospitals and rarely were included in
medical records or statistics. It is equally probable that other remote
and lightly populated areas were similarly underrepresented and incom-
pletely recorded.
The Army survey noted that during 1960-69 there was a countrywide
downward trend in the stillbirth rate. But, as was pointed out in the
-------
-55-
HAC report, this was heavily influenced by data from the capital area,
in which 67.8% of all the surveyed livebirths occurred, and which
generally experienced little or no exposure to 2,4,5-T. Deducting the
capital area data and considering only data from the other parts of
the country apparently reverses the trend, giving stillbirth and
malformation rates for 1960-65 (years of no or light spraying) and
1966-69 (years of heavy spraying) of 31.9 and 2.3, and 38.4 and 3.1,
respectively. This would seem to indicate that in the remoter areas,
where exposure could have been intense, stillbirth and malformation
rates increased during years when spraying was heavy. A possible
explanation for these apparent differences was provided by the HAC
report, in noting that more complete recording and increased referral
of difficult pregnancies from the countryside to the provincial hospitals
occurred in these years. A more likely explanation, however, is that
in recent years, as a larger and larger proportion of births was
registered (e.g., number recorded in noncapital areas in 1960-65 was
37,951; in 1966-69, 113,358) a larger proportion of stillbirths was
ascertained and a more complete examination for and/or recording of
congenital malformations was made.
Particular attention was directed by the HAC reports to the records
for the Tay Ninh Provincial Hospital, because although "the total number
of directly exposed Vietnamese to 2,4,5-T is probably low, the northern
portion of Tay Ninh has been heavily defoliated and the rivers draining
the areas of defoliation run through the remainder of the province and
are a source of fish for some of the population." Examining records
that were apparently not available to the. Army survey, the HAC found that
-------
-56-
in 1968-69 the stillbirth rate recorded at the Tay Ninh City Provincial
Hospital was 68.5, which they believed to be a higher rate than that
found anywhere else by the Army survey. Although this is true, it should
be noted that in two provincial hospitals, Qui Nhon, for which records
only for 1966-69 were available, and Da Lat (nonpaying patients) during
1960-65, the stillbirth rates were not far below this, being 62.7 and
61.4, respectively.
The HAC also discovered how unreliable the records were regarding
congenital malformations, since they noted that not a single malformation
was recorded for the 2551 births in 1969 in the Tay Ninh Provincial
Hospital, and on questioning the midwives it was learned that although
a fair number of deformities had been seen none were reported. Another
hospital, at Vung Tau, during most of 1968-70 reported no congenital
malformations in 6198 births and a much lower stillbirth rate than did
the Tay Ninh Hospital, yet it closely bordered and included in its
referral area a zone of intense defoliation.
A further point needing critical scrutiny is the finding by the
HAC of an apparent increased prevalence of children with spina bifida
and isolated cleft palate among admissions to the Saigon Children's
Hospital, the former increasing from 0.7% in 1959-66 to 2.1% in 1967-68,
and the latter from 0.5% in 1959-65 to 2.6% in 1966-68. It should be
emphasized that the figures do not pertain to incidence at birth, but to
the percentage of malformed children admitted to this Hospital some time
after birth for operative care. It should also be stated that at least
77.5% of all the admissions in 1959-69 came from Saigon or nearby areas
in which defoliation was not practiced. Again the most likely explanation
-------
-57-
of the apparent sudden rise in prevalence of these two malformations is
more thorough examination and increased referral for surgical repair.
Supporting this probability is the fact, noted by the Army Report, that
the frequency of congenital malformations recorded in the capital area
hospitals was much higher (although it varied greatly among the three
hospitals) than in the remainder of the country, a fact in turn attribut-
able to availability of more complete and competent medical services and
personnel in the former than in the latter. ¦
Summarizing the Vietnam data on human embryotoxicity, it can be
said that (1) the sample of births surveyed was from year to year a
variable but usually very small fraction of the total number, (2) it
was quite unrepresentative of the geographic and ethnic distributions,
(3) the heavily sprayed and otherwise exposed areas were greatly under-
represented, and (A) the birth records were not trustworthy and, there-
fore, the rates of stillbirth, and especially of congenital malformation,
derived from them were equally unreliable. For example, the overall
congenital malformation rate found in South Vietnam, 4.91 per 1000 live-
births, is about half of what was reported in other studies in various
oh. i
parts of Asia — , and possibly a quarter of what might actually exist at
term. A further indication that the newborn children were not carefully
examined is the absence of Down's syndrome in the list of specific mal-
formations compiled by the Army survey, despite the fact that some Oriental
populations have been reported to have an incidence of this condition not
28/
unlike that in Western populations .
Finally there is, and can be, no precise knowledge or reasonable
approximation of the exposure to 2,4,5-T experienced by pregnant
-------
-58-
Vietnaraese women, including what amounts they ingested or absorbed and
when this may have occurred during pregnancey. Thus, any attempt to
relate birth defects or stillbirths to herbicide exposure is predestined
to failure. It can only be concluded that the birth records that have
been surveyed, and probably any that will be surveyed in the future, for
South Vietnam for the period 1960-1970 cannot answer positively the
questions about possible adverse prenatal effects following human exposure
to 2,4,5-T. It must be emphasized, however, that the searches that have
been made almost certainly would have revealed any marked increase in the
incidence of birth defects or the introduction of a striking defect such
as that produced by thalidomide. In spite of considerable effort, no such
occurrences were found.
29 /
Globe, Arizona was another site of human exposure — . The herb-
icides used in the Kellner Canyon-Russell Gulch spray project near Globe
were, in 1965 and 1966 the isooctyl esters of 2,4-D and 2,4,5-T, in 1968
an ester of Silvex (2,4,5-TP), and in 1969 about 97% Silvex (3680 lb) and
almost 3% 2,4,5-T esters (Hercules Co., 30 gal.). The reports of harmful
effects to animals and people from the spraying began during and after
the 1969 spraying. Those concerning possible reproductive and embryonic
effects consisted of two miscarriages by a woman, one in April and the
other in December 1969; a number of stillbirths of kids; and one mis-
carriage in a goat. Two other alleged cases consisted of a deformed goat
approximately 5 years old, and therefore born before any herbicide spraying
in the area (incidentally the defects were not of developmental origin),
and a chicken with a slipped tendon which was incubated 4 miles from the
sprayed area and after the spraying occurred in 1969. In all likelihood
none of these reported effects was due to the sprayings. Competent
-------
-59-
medical and agricultural experts have been unable to find evidence of
adverse effects on either human or animal reproduction that could be
attributed to the defoliants applied during the Kellner Canyon-Russell
Gulch spray project.
Swedish Lapland. Swedish government defoliation projects to
improve the quality of forests in Lapland have been associated in the
public press with the occurrence of human malformations and abortion
among reindeer. The chlorophenoxy acids 2,4-D and 2,4,5-T were used in
routine fashion for a number of years without reports of untoward
effects until the spring of 1970 when several instances of unexplained
death and abortion among reindeer were attributed to use of these
compounds. A group of scientific experts has investigated these claims
30/
for the National Poisons and Pesticides Board — and has failed to
find a substantial basis for relating the toxic manifestations in these
animals to ingestion of herbicides. Subsequently two instances of con-
genital malformations in human infants have been attributed to alleged
exposure of pregnant women during application of the herbicides. Highly
competent medical scientists at the Institute of Hygiene and the
Teratological Laboratories of the Karolinska Institute of Stockholm and
at the Institute of Human Genetics at MUnster, Germany have beeh unable
to find temporal or clinical evidence to suggest that the occurrence of
these human birth defects was more than coincidentally related to defol-
iating operations in Sweden.
-------
-60-
References Cited in Section II B
1. Report of the Secretary's Commission on Pesticides and their
Relationship to Environmental Health. U.S. Department of Health,
Education, and Welfare, Washington, D.C. 1969.
2. Report on 2,4,5-T of the Panel on Herbicides of the Office of Science
and Technology, April 1971.
3. Courtney, K.D., D.W. Gaylor, M.D, Hogan, H.L. Falk, R. R. Bates,
and I. Mitchell, 1970. Teratogenic evaluation of 2,4,5-T.
Science 168:864-866.
A. Klingman letter to DuBridge, December 22, 1969. 2,4,5-T Advisory
Committee Exhibit 5.
5. Emerson, J.L., D.J. Thompson, C.G. Gerbig and V.B. Robinson, 1970.
Teratogenic study of 2,4,5-trichlorophenoxyacetic acid in the rat.
Toxic. Appl. Pharmacol., JL7_: 317 (abstract).
6. Emerson, J.L., D.J. Thompson, R.J. Strebing, C.G. Gerbig and
V.B. Robinson, 1971. Teratogenic studies of 2,4,5-trichloro-
phenoxyacetic acid in the rat and rabbit. Food Cosmet. Toxicol.,
in press.
7. Thompson, D.J., J.L. Emerson and G.L. Sparchu, 1971. Study of the
effects of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) on rat and
rabbit fetal development. Teratology, in press.
8. Sparschu, G.L., F.L. Dunn, R.W. Lisowe and V.K. Rowe, 1971.
Study of the effects of high levels of 2,4,5-trichlorophenoxy-
acetic acid (2,4,5-T) on rat fetal development. Unpublished study.
-------
-61-
9. Johnson, J. E., 1970. The public health Implications of widespread
use of the phenoxy herbicides and picloram. Presented at the
Symposium on Possible Public Health Implications of Widespread Use
of Pesticides, American Institute of Biological Sciences,
Bloomington, Indiana, August 26, 1970.
10. King, C. T. G. , 1971. Teratogenicity studies of 2,4,5-T and 2,4-D.
Unpublished report, February 25, 1971.
11. King, C. T. G., E. A. Horigan, and A. L. Wilk, 1971. Screening of
the herbicides 2,4,5-T and 2,4-D for cleft palate production.
Teratology, in press.
12. Tschirley, F. H., 1971. Report on status of knowledge regarding
2,4,5-T. Submitted by the USM to the EPA, March 5, 1971. 2,4,5-T
Advisory Committee AE-20.
13. 2,4,5-T Advisory Committee Exhibits I-13a, 1-14, and 1-15.
14. Courtney, K« D. and J. A. Moore, 1971. Teratology studies with
2,4,5-T and tetrachlorodioxin. Submitted to Toxic. Appl. Pharmacol,
15. Moore, J. A. and K. D. Courtney, 1971. Teratology studies with the
trichlorophenoxyacid herbicides 2,4,5-T and Silvex. Teratology,
in press.
16. Khera, K. S., B. L. Huston and W. P. McKinley, 1971. Pre- and
postnatal studies on 2,4,5-T, 2,4-D, and derivatives in Wistar
rats. Toxic. Appl. Pharmacol., in press.
17. Wilson, J. G., 1971. Unpublished data.
18. Sparschu, G. L., F. L. Dunn and V. K. Rowe, 1970. Teratogenic
study of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the rat. Toxic.
Appl. Pharmacol., 17^:317 (abst.).
-------
-62-
19. Moore, J. A., 1971. Personal communication to 2,4,5-T Advisory
Committee.
20. Collins, T. F. X., and C. H. Williams, 1971. Teratogenic studies
with 2,4,5-T and 2,4-D in the hamster. Teratology, in press,
21. Collins, T. F. X., and C. H-. Williams, 1971. Teratogenic studies
with 2,4,5-T and 2,4-D in the hamster. Unpublished studies.
2,4,5-T Advisory Committee AE-16.
22. Effects of 2,4,5-T on Man and the Environment. Hearings before
the Subcommittee on Energy, National Resources, and the Environment
of the Committee on Commerce, U. S. Senate, April 7 and 15, 1970.
Serial 91-60, p. 354.
23. Wilson, J. G. Preliminary report submitted to Swedish Poisons and
Pesticides Board, April 19, 1971.
24. Cutting, R. T., T. H. Phuoc, J. M. Ballo, M. W. Benenson, and C. H.
Evans. 1970. Congenital malformations, hydatidiform moles, and
stillbirths in the Republic of Vietnam 1960-1969. Govt. Printing
Office, Washington, D. C.
25. Meselson, M. S., A. H. Westing and J. D. Constable, 1970. Background
Material Relevant to Presentations at the 1970 Annual Meeting of
the AAAS. Herbicide Assessment Commission of the American
Association for the Advancement of Science. Revised January 14,
1971.
26. Summary of presentations by the Herbicide Assessment Commission of
the American Association for the Advancement of Science, Chicago,
Illinois, December 29, 1970.
27. Foster, L., and M. Harth, eds., 1971. The New York Times Encyclo-
pedic Almanac 1971. New York Times, New York.
-------
-63-
28. Kikuchi, Y., H. Oishi, A. Tonomura, K. Yamada, Y. Tanaka, T.
Jurita and E. Matsunaga, 1969. Translocation Down's syndrome In
Japan: its frequency, mutation rate of translocations and parental
age. Jap. J. Human Genet., 14:93-106.
29. Binns, W., C. Cueto, B. C. Eliason, H. E. Heggestad, G. H. Hepting,
P. F. Sand, R. F. Stephes, and F. H. Tschirley, 1970. Investigation
of Spray Project near Globe, Arizona. Investigation Conducted
February 1970. 2,4,5-T Advisory Committee AE-15.
30. Rapport frSm en expertgrupp, 1971. Fenoxisyror, granskuing av
aktuell information, Giftnamnden, Stockholm,
-------
-64-
GENERAL CONCLUSIONS
The Advisory Committee on 2,4,5-T has accepted as its primary
objective the evaluation of hazards to human reproduction of continued
use, under appropriate regulations, of the herbicide 2,4,5-T. Toward
this end it has examined all available information pertinent to a
scientific consideration of the subject.
The level of human exposure depends on rate of application of the
herbicide, balanced against the rate at which it is removed from the
environment. Current patterns of usage of 2,4,5-T and its known fate
in various compartments of the environment, including the plant and
animal foods of man, are such that any accumulation that might constitute
a hazard to any aspect of human health is highly unlikely.
Special note has been taken of the toxic contaminant TCDD. The
limited data now available indicate that this dioxin is not as rapidly
degraded in the environment as is 2,4,5-T, but modern methods for the
manufacture of the herbicide are capable of routinely producing a
product with such a low level of contamination as to eliminate the
likelihood of human toxicity from exposure to TCDD. Manufacturing
standards must, however, be subject to continued monitoring.
Much of the general toxicity attributed to 2,4,5-T in the past
now appears to have been caused by the contaminant TCDD. The herbicide
when essentially free of this contaminant, e.g. 1 ppm, has relatively
low toxicity for all animal forms in which it has been tested.
Particular attention was given to the teratogenic potential of
-------
-65-
both 2,4,5-T and TCDD. Acceptable data are now available on the
embryotoxicity of 2,4,5-T in 6 mammalian species, mouse, rat, hamster,
rabbit, sheep and rhesus monkey. None of these showed adverse effects
at dosage of 40 rag/kg/day of maternal weight.
The mouse appears to be more sensitive than the other forms
studied in that it shows a low level of teratogenicity (cleft palate)
at 100 mg/kg/day given throughout organogenesis, whereas hamster and
rat required higher dosage to obtain comparable effects. It is likely
that all species could be caused to show some embryotoxicity if 2,4,5-T
dosage were raised high enough, a fact already well known for many
prevalent environmental chemicals such as aspirin, caffein, nicotine
and organic mercury.
The dioxin contaminant TCDD also has been shown to have a low
teratogenic potential at doses in excess of 0.001 mg/kg, but this dosage
level is virtually impossible with currently produced 2,4,5-T. No
evidence has been found of significant potentiative interaction between
2,4,5-T and TCDD.
No evidence has been found of adverse effects on human reproduction
in three separate locations, namely Vietnam; Globe, Arizona; and Sweden,
where pregnant women have allegedly been exposed to high levels of
2,4,5-T.
On the basis of these observations, it is concluded that, as
presently produced and as applied according to regulations in force
prior to April 1970, 2,4,5-T represents no hazard to human reproduction.
-------
-66-
RECOMMENDATIONS
The Advisory Committee on 2,4,5-T after careful consideration of
available information on potential hazards to man, particularly as
regards reproductive functions, of continued, regulated use of 2,4,5-T,
recommends the following:
1. That registration for use of 2,4,5-trichlorophenoxyacetic acid
and its esters be restored to the status existing prior to April 1970,
with the following exceptions.
2. That certain specific limitations and qualifications be added
to the previously existing registration, as follows:
a. A permissible residue or not more than 0.1 ppm of 2,4,5-T
on the edible parts of food products &nd in potable water for human
consumption be accepted. It is recognized that very few foods
tested to date have contained this level of residue, but it is
probable that some of the reports of no residue in the past were
due to limited sensitivity of the analytical method. In view of
recent and future advances in methodology, which tend to make zero
residues of anything increasingly unlikely, a more realistic
policy would be the setting of safe tolerance limits at this time.
b, A limit of 0.5 ppm of contamination with 2,3,7,8-
tetrachlorodibenzo-p-dioxin be set for existing inventories of
2,4,5-T, except as specified in item c. below, and a limit of 0.1
ppm of contamination with this dioxin be established in all future
production of 2,4,5-T. Surveillance should be maintained by
requiring that a manufacturer submit a reference sample and a
certified analysis of each future production lot to the Environmental
Protection Agency.
-------
-67-
c. All formulations to be used around the home and in
recreational areas as of present date should be limited to 0.1 ppm
of the dioxin, TCDD, and also should bear a conspicuous warning,
e.g., "This compound may be dangerous to pregnant women and animals
and its use must be such as to reduce the possibility of exposure
to an absolute minimum".
3. That existing deficiencies in information relative to possible
accumulation in the soil and possible magnification in the food chain
of the dioxin TCDD be rectified by specific research directed to this
end, with these questions to be subjected to scientific review within
three years of the present date and yearly thereafter until these
questions are resolved,
4. That additional post-registration monitoring for adverse
effects of agricultural chemicals be established, to include both
surveillance for such effects in man and domestic and wild animals, as
well as consideration of the applicability of new methodology that may
be evolved for specialized testing, e.g., for carcinogenesis,
mutagenesis or teratogenesis.
Date: May 7, 1971
~
James G. Wilson, Ph.D
-------
-68-
Objections to and Modification of
the Final Report and Recommendations of the
2,^,5-T Advisory Committee
The report by the 2,U,5-T Advisory Committee is basically an accurate
statement of the present state of information; however, it falls short of
being completely fair in its evaluation of the evidence on which conclusions
are based. It is true that considerable uncertainty exists about the tera-
togenic potential of 2,^,5-T (and of its impurities) especially for the
small doses at vhich man may make effective contact with this suDstance. On
the other hand, the report is overoptimistic in assessing the implications
of data so that it may veil underestimate what dangers may lurk in the
unrestricted use of 2,11,5-T. Particularly:
The data do not necessarily justify a conclusion that there is a
level at which TCDD is not teratogenic.
There is an unjustified certainty that Vietnam birth records do
not show teratogenic effects.
The report fails to consider the consequences of the (admitted)
uncertainty about the fate of TCDD in the food chain and in tissue.
The report does not weigh risk vs. benefits, as it was charged to do.
The report presumes to lecture the scientific community on the wis-
dom of instituting a "permissible residue" of substances thought
to be teratogenic.
The report is overoptimistic in believing that recommendations for
needed research will be followed by industry or by public agencies
once a decision has been rendered to restore 2,'i,5-T to unrestricted
use.
-------
-69-
We can only conclude that the Surgeon General was Justified in feeling
that a prudent course of action must be "based on the decision that exposure
to this herbicide may present an imminent hazard to women of childbearing
age. Hence, we can only recommend that the registration of 2,1|,5-T be
suspended and/or cancelled for use around the home, recreation areas, and
similar sites and on all crops intended for human consumption. However, the
use of 2,U,5-T may be permitted under certain conditions for uses in fores-
tration and rights-of-way providing:
1. That the limit be set of 0.1 ppm of contamination with 2,3,7>8-
tetrachlorodibenzo-p-dioxin for all future production of 2,U,5-T.
(However, the use of present inventories may be permitted until
used up providing the amount of contaminant in them does not
exceed .5 ppm of the dioxin TCDD.)
2. That 2,1»,5-T be applied no more often than once a year at any one
site.
3. That 2,^,5-T be applied with proper caution so that it will not
contaminate other areas where it may come into human contact.
We also recommend that this action be reviewed again when the existing
deficiencies in information relative to possible accumulation in the soil and
possible magnification in the food chain of the dioxin TCDD have been recti-
fied by specific research directed toward that end.
It is always difficult to make decisions in the face of uncertainty. The
insufficient data makes the work, of the committee very difficult. The fact
that ours is the view of the minority ought to strengthen the impression that
the committee labored honestly and conscientiously to deduce the best recom-
mendations from a confused aggregate of observations.
5/5/71
Theodor D. Sterling
-------
-70-
Additional Comments
It Is Hot Quite Certain at What Dose TCDD Has Mo Effect
The report gives the impression that 2,1+,5-T shows a teratogenic
effect uniformly at high doses only. One reason for that impression is
that most investigations concentrate on doses of 100 mg/kg or more so that
data are lacking to a large extent on how much of teratogenic effects could
show up at smaller doses. Yet, there are a number of studies that do show
definite effects for doses of less than 100 mg/kg of weight.* Also, the
dose effect of 2,U,5-T depends largely on its impurities, especially on
TCDD. The experiments which provide the basic animal data and the analysis
of these data unfortunately were not done with the sophistication necessary
to throw light on the effect of 2,1+,5-T and TCDD at very low doses. Many
of the reports presented no more than tables of group means, and some even
presented pages and pages of undigested numbers on individual observations.
It is difficult to draw any final and firm conclusion from data such as
these. Nevertheless, there are sufficient instances where teratogenic
* For example, on rabbits increased resorption and diminished fetal weight
reported by Emerson, J. L., Thompson, D. J,, Gerbig, C. G., and Robinson,
V. B.: Teratogenic Study of 2,5-Trichlorophenoxyacetic Acid in the
Rabbit, The Dow Chemical Co., Zionsville, Indiana.
A number of instances are cited by Epstein, S. S., of the Children1s
Cancer Research Foundation, Inc. and Harvard Medical School, Boston,
Mass., U/1V70, Subject: Teratogenic effects of 2,U,5-T formulations.
Another example is the study on hamsters by Courtney, K. D., Moore, J. A.,
Gay lor, D. W., Hogen, M. D., Falk, H. L.: E'.unmary Teratogen Study NIEHS.
-------
properties have been observed at lover doses than 100 mg/kg so that the
question whether there is a zero effect for some dose is not easily answered.
A case in point is the data included in this report by the chairman of the
committee. The experiment provides for doses of 100, 200, and U00 mg/kg
but only tests at one single low dose, that of 20 mg/kg, although the effect
of a dose at this low level is of utmost importance. Also, there are no
control animals. Cumulative experience with untreated controls over the
past four years and cumulative vehicle treated controls (per gavage) over
the past four years are used as controls. Given our knowledge of variation
in experiments, it is difficult to understand why this important experiment
was performed without a concurrent control. Yet, per cent dead or resorbed
fetuses show a trend toward lower dose which is still detectable at 20 mg/kg.
(Whether or not we think of this effect as large or small will depend on
whether or not we are willing to accept Control 1. or Control 2. of that
study.) Taking these factors into consideration, it becomes difficult to
see how the report can conclude that "doses of low-dioxin-content 2,U,5-T and
of TCDD below the level producing maternal toxicity were without significant
effect on prenatal development producing little or no embryo-toxicity in
rats, rabbits, hamsters, sheep, and rhesus monkeys" (page 50, Final Draft).
If anything, the conclusion ought to have read that, despite the small
amount of data present, some of it does point to teratogenicity at lower
doses.
The Uncertainty About the Vietnam Human Data Does Not Mean
These Data Show Mo Effects of 2th%5-T on Stillbirth and Malformation
2,lj,5-T was used extensively in Vietnam for defoliation. Unfortunately,
birth records show a confused and confusing picture of what happened to mal-
formation in Vietnam during the years in which defoliation efforts increased
-------
-72-
and how stillbirth rates compare between regions that are heavily defoliated
and regions that sire not. The Array survey notes that during 1966 to 1969
there was a countryvide downward trend in the stillbirth rate. But the HAC
report points out that this conclusion was heavily influenced by data from
the capitol area in which 67.8 per cent of all live births surveyed occurred
and which, in addition, generally experienced little or no exposure to
2,U,5-T. Deducting the capitol area data and considering only that from other
parts of the country, reverses the trend and results in lower stillbirth
and malformation rates for 1960-65 (years of no or light spray) than for
1966-69 (years of heavy spraying). Also, HAC found that the I96O-69
stillbirth rates recorded at Tay Ninh City Provincial Hospital, a hospital
which was in a region heavily defoliated and through which rivers draining
areas of defoliation run, had a recorded stillbirth rate of 68.5, which they
believe to be higher than that found anyvhere else.
The 2,i»,5~T Advisory Committee report goes into the unreliability of
all the human data that comes from Vietnam in great detail. It is true
that the instances cited might easily have created a spurious impression of
an increased stillbirth rate for the defoliated regions or periods. However,
the opposite might be just as true. Factors could just as easily have worked
to hide a large stillbirth rate than to spuriously create one. If we
already speculate, we might just as easily speculate the other vay. Tlius,
the best we can say is that these data do not definitely show an effect of
defoliation. However, they do show an effect which has to be explained away.
It is up to the committee to register our doubts, but it is unseemly to
spend page after page denying the reality of the Vietnam observation in the
face of the careful report by a select committee of the American Association
for the Advancement of Science.
-------
-73-
The Report Fails to Consider the Uncertainty
About the Fate of TCDD
It is not possible to produce 2,1»,5-T without impurities, especially
the dioxin TCDD. These impurities have been shown to be toxic and terato-
genic in the extreme, (in fact, the recommendations of the report to restrict
the permissible level of TCDD in 2,U,5-T and to monitor this restriction is
in recognition of its hazard.)
While 2,4,5-T is quickly eliminated from the soil by biological and
other actions, the same cannot be said of TCDD. The report notes that TCDD
might accumulate in the soil from one year to the next. There is also
evidence that a small amount of the soil's TCDD is absorbed by plants. But
there is no information on the concentration of TCDD in the food chain at
this level, nor is there information as to vhat extent TCDD may be stored
by animal tissues. Again, the report speculates that TCDD is not stored to
a significant extent because it is not easily soluble in oils. However,
may it not be stored by other tissues besides fat, and, in fact, may it not
be stored more by animal fatty cells than in oils? (There is some evidence
that TCDD, when digested, finds its way to every tissue in the body.)
There is no question but that some doubts exist in the minds of the
committee on this point. The recommendations acknowledge these doubts and
ask that the deficiency in information relative to possible accumulation in
the soil and possible magnification in the food chain of the dioxin TCDD
be rectified by specific research directed to this end, with this question
to be subjected to scientific review within three years of the present date
and yearly thereafter until these questions are resolved (Section 3 of Final
Draft Recommendations).
-------
-74-
We find it difficult to go along with this reasoning. After recent
experience with DDT and with mercury, it would be reckless to leave such
questions in abeyance while approving the unrestricted use of 2,1+,5-T.
Nothing would be lost by waiting two or three years while this question
can be settled. On the other hand, a great deal of damage may be created
if the committee restores 2,U,5-T to its normal use while hoping that further
research will justify our confidence in having made a correct guess. More-
over, the restriction of 2,U,5-T from regular use would work as a powerful
motive, spurring industry and concerned government agencies to seek to settle
this important question by initiating appropriate studies. Yet, at the same
time, the use of 2,U,5-T could be maintained in all those instances where
contamination of food or people would be unlikely.
Considering the Risk/Benefit Equation
A curious situation emerges in evaluating the benefit of 2,1*,5-T. It
is apparently of major value in its nonfarm uses, especially for forestry
and road clearance, where it can be applied sparingly and with a great deal
of expertise. Also, in forestration 2,U,5-T may be reapplied only every
few years. The other uses in or near food crops and around the home repre-
sent less frequent areas of application but may expose very large numbers of
individuals to 2,^,5-T, to its impurities, and to its residues. Thus, it
is not true that all uses of 2,U,5-T are equivalently beneficial.
Many of the nonfarm uses of 2,li,5-T clearly have national benefit. On
the other hand, the use of 2,H,5-T for the growing of crops, especially
rice, is basically of benefit to a few farm industries because it increases
the yield per acre of cultivated ground. Since there are available raany
acres that are not now cultivated, there docs not appear to be a national
-------
-75-
urgency to support that limited use of 2,kt5-T until important questions
about buildup of TCDD have been settled. Similarly, the use of 2,lt,5-T
for grazing land is of relatively small benefit for a small number of
people. Finally, although the use of 2,U,5-T around the house may be
thought of as of national importance, adequate alternate means for home
gardening do exist, so that it may be best to avoid for the moment the
possible risk of direct contact with man.
Theodor D. Sterling
5/5/71
-------
-76-
LIST OF PERSONS CONFERRING WITH THE COMMITTEE
Mr. Harold G. Alford> PRD
Dr. Theodore Byerly, USDA
Mr. Robert L. Caswell, PRD
Dr. Cipriano Cueto, PRD
Dr. K. D. Courtney, NIEHS
Mr. Charles Dunn, Hercules Incorporated
Mr. Blaine Fielding, OGC
Dr. John Frawley, Hercules Incorporated
Dr. Dan Gaylor, NIEHS
Dr. R. E. Johnson, EPA, OP
Mrs. Joan Katz, Attorney representing Harrison Wellford, et al.
Dr. Albert Kolbye, FDA
Mr. John Kuniholm, Hercules Incorporated
Mr. D. D. McCollister, Dow Chemical Company
Dr. I. A. Mitchell, Office of Surgeon General
Dr. J. A. Moore, NIEHS
Dr. David P. Rail, National Cancer Institute
Mr. George Robertson, OGC
Dr. Virgil Robinson, Dow Chemical Company
Mr. V. K. Rowe, Dow Chemical Company
Dr. Jessie Steinfeld, Surgeon General
Mr. Paul Whiteaker, PRD
------- |