United States	Press Office (A-107)
Environmental Protection	Washington DC 20460
&EPA Environmental
TUESDAY, APRIL 29, 1980	O'Neill (202) 755-0344
EPA ASKS FOR MORE	Barbara Blum, Deputy Administrator of the U.S.
HERBICIDE 2,4-D	Environmental Protection Agency, announced today that
the Agency is requesting additional information from
manufacturers to determine whether 2,4-D, a widely
used herbicide, is safe for humans and the environment.
"We have made this decision following a review of
health-effects studies of 2,4-D," Blum said. "The
review showed that significant information gaps exist
on the effects of 2,4-D, preventing a definite
conclusion on the safety of the herbicide.
"We will ask the manufacturers of the weed killer to
commence the studies to provide the missing evidence."
Blum said that if the manufacturers fail to notify EPA
within 90 days that they will provide the necessary
information, EPA will use a stringent new provision of
the pesticides law, Section 3
Companies that hold EPA permission to produce concentrated
or "technical" 2,4-D include Dow Chemical Co., Midland,
Michigan; Monsanto Chemical Co., St. Louis; Diamond Shamrock
Corp., Dallas; PBI Gordon Corp., Kansas City, Kansas; Thompson-
Hayward Chemical Co., Kansas City, Kansas; and AmChem Products,
Inc., Ambler, Pa.
"EPA conducted its review of health-effects studies on 2,4-D
because of increasing citizen concern about the high level
of exposure to 2,4-D around the country and because of its
chemical similarity to the dioxin-contaminated herbicides,
2,4,5-T and Silvex," Blum said.
There also has been concern because 2,4-D was a component --
along with 2,4,5-T -- in Agent Orange, the defoliant used by
the military in Vietnam. Although never approved by EPA for
civilian use in the United States, its use in Vietnam has
resulted in numerous claims of adverse health effects to
American military personnel. These claims are now under
investigation by the Veterans Administration.
EPA, about a year ago, imposed an emergency ban on many
major uses of 2,4,5-T and Silvex. More recently, the agency
opened hearings to determine whether all uses of these
chemicals should be banned on grounds that they can cause
cancer, birth defects and miscarriages.
EPA's review of 2,4-D studies showed that the evidence of
adverse health effects weighs far more heavily against
2,4,5-T than against 2,4-D.
"For one thing," said Blum, "there is no evidence at this
time that 2,4-D contains any form of dioxin, the contaminant
in 2,4,5-T associated with cancerous tumors and birth defects."
Blum stated that "Toxicity studies of 2,4-D have either
showed that significant adverse effects were unlikely at
expected human exposure levels, or they were inconclusive,
or they were not conducted in a manner acceptable by today's
scientific standards."
At this point, she said, the agency, while taking no action
restricting use of the chemical, will require the manufacturers
of 2,4-D to provide additional information in the areas of
oncogenicity (tumor inducing), reproductive effects (particularly
effects to the fetus), and metabolism in animals. She said
EPA also plans to conduct certain reproductive studies on
2,4-D in its own laboratories while awaiting the industry
In addition, EPA will consult with its Scientific Advisory
Panel during its May 28-30 meeting to determine if there are
additional studies necessary to determine the safety of
2,4 -D. Following the findings of the Scientific Advisory
Panel, the agency will formally specify to the manufacturers
what studies are needed.
Details of the agency's review of the health effects information
on 2,4-D are in the attached fact sheet.
# # #

April 1980
2,4-D is one of the most widely used herbicides in
the United States. There are approximately 1,500 products
containing 2,4-D registered with EPA, and more than 70
million pounds of the active ingredient are distributed
annually. The term "2,4-D" refers to the phenoxy herbi-
cide 2,4-dichlorophenoxy acetic acid and its 35 derivative
salt and ester forms. 2,4-D is used to control broadleaf
weeds in a variety of places including home lawns, cereal
and grain crops, commercial areas, commercial turf, rights-
of-way, and forests.
Public concern about the potential adverse health effects
of 2,4-D has intensified since the emergency suspension of
2,4,5-T and Silvex in March 1979. This concern stems
primarily from 1) the chemical similarity of 2,4-D and
2,4,5-T as phenoxy herbicides, and 2) the question of 2,4-D
dioxin-contamination, especially contamination with tetrachloro-
dioxin, a manufacturing contaminant in 2,4,5-T, which causes
cancer and miscarriages. Due to the chemical similarity of
2,4-D and 2,4,5-T, the public has expressed concern about
the potential for cancer and miscarriages from the use of
2,4-D. There is also concern because the controversial
military defoliant Agent Orange, used in Viet Nam, was
composed of 2,4,5-T and 2,4-D. Agent Orange was never
registered by EPA for civilian use in the United States. Its
use in Viet Nam by the U.S. military has resulted in claims
of adverse health effects to American military personnel.
The Veterans Administration is studying these claims.
Prompted by these concerns and EPA's need to resolve the
questions surrounding the use of 2,4-D, the Agency initiated
a review of the available information on the potential health
effects of 2,4-D. Thi-S review wa conducted in part to
determine if the herbicide should be reviewed under the RPAR
process (Rebuttable Presumption Against Registration) or if
another regulatory action was appropriate.
II. Agency Review and Conclusions
Based on the results of this review, EPA has concluded that
a) the presently available information on the potential
adverse health effects of 2,4-D does not support a regulatory
action to remove 2,4-D products from the market; b) information
from scientifically valid studies does not indicate that the
continued use of 2,4-D poses an imminent hazard or unreasonable
adverse effect when used according to label precautions and
direction for use; and c) the Agency should act quickly and
vigorously to obtain better toxicological information on
\ - r/

These conclusions are based on these following
cons iderat ions:
1.	Ther<=> is no evidence available at this time that
indicates 2,4-D contains any form of dioxin. This includes
the tetrachloro-dioxin (TCDD), which is a manufacturing
contaminant of 2,4,5-T and causes cancer and miscarriages.
TCDD is not theoretically expected to be found in 2,4-D.
The manufacturing processes and starting chemicals from
which 2,4-D and 2,4,5-T are made are not the same.
Although other much less toxic dioxins are theoretically
possible in 2,4-D, they have not been found despite
thorough chemical analyses.
2.	Because products containing 2,4-D have been
registered for use since the 1940's, most of the scientific
data submitted to support the product registrations now
on the market were developed many years ago. While some
of these studies are scientifically valid, many others do
not meet today's standards for scientific testing. As a
result, there are significant information gaps in several
areas including cancer-potential, reproductive effects,
neurotoxicity, and metabolism in animals.
3.	The studies most pertinent to the question of
tumor-causing potential (oncogenicity) of 2,4-D were
considered inadequate and inconclusive. No valid
conclusions could be drawn one way or another from the
4.	Almost all animal tests conducted on the potential
reproductive effects of 2,4-D show that, unlike 2,4,5-T
with its contaminant TCDD, there is a no-effect level for
injury to the fetus (fetotoxiciy) from 2,4-D. A no-effect
level in animal studies is the dose level below the
lowest dosage that produces observable adverse effects.
At comparable dose levels, 2,4-D induces less serious
fetotoxic effects than 2,4,5-T contaminated with TCDD.
In tests with rats, 2,4,5-T with its TCDD contamination
caused resorptions of the fetus (dissolution of the unborn
animal) at very low levels. This effect was virtually
non-existent in rats fed 2,4-D at the same dose levels.
Because of the significance of fetotoxic effects and because
several of the reproductive tests on 2,4-D were found to be
scientifically deficient, new tests will be needed before sound
conclusion can be made.
5.	The scientific evidence available at this time
does not indicate the potential human exposure is sufficient
to result in human health effects.

6.	The most vigorous authority available to EPA under
the pesticide law to fill information needs is a new section
of FIFRA (Federal Insecticide Fungicide Rodenticide Act)
passed in 1978. This provision, known as 3(c)(2)(B), allows
EPA to request any additional data from pesticide registrants
that is considered necessary to maintain the registration of
existing products. The Agency can immediately require the
manufacturers to develop the data where gaps exist. The
registrants have 90 days to show that they are complying.
Their product registrations may be summarily suspended if they
fail to meet the Agency's conditions. No other action could
obtain this information any faster. EPA is putting the data
requirements into final form and they will be issued to the
registrants after review by our Scientific Advisory Panel.
These scientific experts will review and comment on the data
requirements to assure that they will provide the information
EPA needs to more definitively answer the questions on potential
health effects of 2,4-D.
7.	Based on a review of the toxicology data (see section
IV below), and a review of the risks of other pesticide chemicals
now undergoing regulatory action, the Agency believes that the
risks of several other pesticides are higher and better documented
than those associated with 2,4-D. To put the review of these
other higher priority chemicals aside in order to devote EPA
resources to taking action against 2,4-D would not, in the
Agency's opinion, best serve the public interest.
III. Additional Actions
In addition to requiring several important studies of
the manufacturers on 2,4-D, EPA will also:
1.	Conduct several tests on reproductive effects (through
our Office of Research and Development) of several derivatives
of 2,4-D in order to quickly get new information and have a
good basis for comparison with the company-produced data.
2.	Continue its ongoing review of forest pest control
practices. This review will evaluate all chemical and non-
chemical controls to identify the most environmentally protective
ways to control forest pests. The Agency believes that a
piecemeal approach to forest chemical regulation only leads
to confusion, both to the industry and to the public. Unless
we review the whole range of possible controls, examining
one chemical at a time only gives rise to questions about
the chemicals which would be used to replace those examined and
prohibited from use.
3.	Review all new data as it comes in to determine if
a change in our regulatory posture is warranted. This includes
evaluating the results of new animal tests as well as looking
into reported incidents involving human exposure to the chemical.

4.	Continue to support field tests to measure exposure
to 2,4-D during the present growing season.
5.	EPA is informing the Inter-Agency Work Group,
established by the White House to study the possible long-term
effects of Agent Orange, of the actions being taken. EPA will
also share its scientific findings with this committee.
IV. Toxicology Background
The potential hazard of a chemical is usually measured
in laboratory animal tests. Animals are given doses of
a chemical over a specific time period. Scientists attempt
to derive from most of these tests a "no observable effect
level" (NOEL) -- the dose level below the dosage where
effects are first observed. From the animal tests and
NOEL's, the potential effects on humans and other animals
can be estimated. A set of brief definitions is provided
below to permit better understanding of the subseguent
discussion of toxicological findings.
A. General terms
1.	Acute oral toxicity (LD50) - this test determines
the dose level which produces death in half
the test animals after a single oral dose
(short-term test). Used to predict the near-
term toxicity of the chemical immediately upon
contact with people or other non-target animals.
2.	Chronic feeding tests - animals are fed for
most their life span (usually greater than 18
months in rodents) in order to determine the
dose level which shows no toxic effect in test
animals. This is the test from which the NOEL
is (usually) derived.
3.	Oncogenicity testing - animals fed relatively
large doses of the test chemical for their life
span (usually 18 months to 2 years in rodents)
to try to induce tumors. These tests are used
to predict whether the chemical may pose a
cancer hazard.
4.	Reproductive testing - these tests evaluate the
effects of the chemical on the fertility of both
the male and female parents by exposing the
animals for a period of time before breeding.
The tests also measure the possible effects of
the chemical on the pregnant female and the
fetuses through several generations. (The
test with rodents through 3 generations runs
approximately 14 months.)

5.	Teratology testing - these tests evaluate the
effects of the chemical on fetuses by exposing
pregnant females during the short period of time
that the fetus is most susceptible to congenital
nta 1 f ormh t i on. Teratogenic effects include cleft
palate, central nervous system deformities, eye
and limb deformities, and internal organ malfunction.
These are considered to be life-threatening
effects that put the animal at a disadvantage
for surviving in its environment.
6.	Fetotoxicity - fetotoxic effects can be seen in
either the reproduction or teratology tests.
Toxicity may be seen in the exJtreme form as
fetal death or as less severe problems, such
as delayed formation of bones, reduced body
weights at birth, or edema (abnormal fluid
accumulation in the tissue). Most fetotoxic
effects appear to be reversible once exposure
to the test chemical is curtailed. Therefore
most fetotoxic effects are cons idered . to
be less serious than teratogenic effect s, with
the exception of fetal death.
B. Summary of Toxicology Review
Most of the data in EPA files on the potential health
effects of 2,4-D are centered on the acid form, even though
there are many derivatives, such as salts and esters. This
is because the many forms of 2,4-D metabolize to the acid
form in the environment and in the body. The discussion of
animal data below, therefore, concerns the acid form of
2,4-D unless otherwise noted.
1.	Acute toxicity - low to moderate. The potential
for immediate poisonings from contact with the
chemical is unlikely.
2.	Neurotoxicity - There is little definitive
information on the possible neurological effects
of 2,4-D. In several reported cases of impaired
nerve function, it was not known if the individuals
were peculiarly sensitive to that type of effect
or were exposed to other toxic materials.
3.	Reproductive effects (effects on the unborn) -
Tests have been conducted on rats, mice and
hamsters to evaluate the possible reproductive
effects of 2,4-D. In almost all testSj no observable
effect level has been established. 2,4-D causes
some of the less serious fetotoxic effects, such
as edema (swelling of tissues) at the lower dose
levels tested, and causes life-threatening birth
defects (skeletal malformations) and cleft
palates only at the very high levels tested.

Based on the no observable effect levels 1n the animal
studies, EPA estimates that the level of exposure
in a "worst case" situation (eg. a person standing
directly under a spray plane) would be 500 to 1000
times less than the dose level that might cause an
Much of the data available to judge these effects
was generated by old study protocols, has deficien-
cies in the test methods, and needs clarification
by further study.
EPA also reviewed summaries of tests conducted in
the Soviet Union which state that some derivatives
of 2,4-D produced adverse effects on unborn animal
fetuses at much lower levels than indicated by the
data in EPA's files. These summaries could not be
used in the Agency's review because the identity
of the test material, and its impurities, was unclear,
and because there were no numerical data to back up
the summary conclusions. In some cases tests need
to be done on specific derivatives of 2,4-D.
4.	Oncogenicity (potential for causing tumors) -
Several rodent studies have been conducted to date.
The tests were conducted a decade ago and are con-
sidered to be inadequate and inconclusive by today's
scientific standards. New studies on rodents are
needed .
5.	Mutaqeni ci ty (inheritable effects) - The vast
majority of the mutagenicity studies conducted
on 2,4-D are negative. However, there are three
positive studies. Taken as a group, the results
of the studies can be described as inconsistent
and inconclusive. A new series of tests being
conducted by the Department of Health, Education,
and Welfare will be reviewed by EPA when they
are completed.
6- Epidemiology - No epidemiological studies of human
health effects from 2,4-D exposure have been com-
pleted. However, EPA is currently investigating
reports about alleged adverse effects from potential
chemical exposure in several parts of the country.
EPA will be looking at the results of those studies
and will decide in the near future about additional
field work.

V. Exposure to 2,4-D
There are at least three ways that the average citizens
might come into contact with 2,4-D - through the diet, during
home use, and drift of the herbicide from nearby use.
a)	Diet
The EPA has set tolerances for residues of 2,4-D in
various food crops. The Food and Drug Administration (FDA)
routinely samples a variety of foods (the Market Basket
Survey) which FDA considers to be representative of the
average American diet. Samples are analyzed for pesticide
residues. During the period of 1974 to 1977, no 2,4-D
residues were found in any of the products surveyed.
However, during the 1965 to 1977 period, a variety of other
food products were analyzed, of which about 1.1% were
positive for 2,4-D in very minute quantities that were well
below EPA's tolerance (allowable residue) levels.
b)	Home use
There are currently a number of registered home-use
products which contain 2,4-D in a variety of formulations.
Exposure to the herbicide in home-use situations will
depend to some extent on the specific formulation used.
If care is exercised by the homeowner in adhering to the
directions for use and precautionary statement on the
label, exposure to 2,4-D should be low.
c)	Drift
"Drift", the airborne transport of pesticide materials
to a non-target area, is a common source of exposure.
Sometimes, a pesticide will drift during application,
depending on climatic conditions (temperature, wind speed),
type of formulation used, terrain (forests, mountains),
and type of application method used (aerial, ground spray).
Several States have imposed restrictions on 2,4-D use in
order to cut down on drift potential.
Once on the ground or target crop, the herbicide may
become airborne again by the process of vaporization. This
particular type of drift has been the subject of intensive
research by the producers of 2,4-D. Since the introduction
of less volatile forms of the herbicide over the last few
years, this kind of drift has become much less extensive.

VI. Environmental Persistence
2,4-D is not a persistent pesticide. Breakdown of the
herbicide begins almost immediately after application at
a rate dependent on several environmental factors such
as temperature, humidity and medium (air, soil, crop,
water). The rate of loss (commonly referred to as the
half-life) is a measure of the time required for half of the
substance to- be degraded or lost.
On sprayed vegetables, the half-life varies from 1-3
weeks depending on geographic location, climatic conditions,
vegetation type, application technique and formulation used.
In soil, the half-life varies from several days to 2
weeks, depending on acidity, soil type and amount of rain.
In water, the half-life varies from a few days to several
months "depending on factors such as oxygen concent rat ion,
acidity, light intesity, water temperature and formulation-

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