triasulfuron (Amber) EPA Grants Conditional Registration 7/92
triasulfuron (Amber) July 10, 1992
EPA'S DECISION TO CONDITIONALLY REGISTER "AMBER"
In February, 1992, the Agency issued a two-year conditional registration
for triasulfuron, also known as Amber. This was in response to Ciba-Geigy
Corporation's application for registration and petition for tolerances for
Amber submitted to the Agency in June, 1988. Amber is a selective
sulfonylurea herbicide intended to control annual and perennial weeds. It is
to be applied by ground or by air to wheat, barley, and follow cropland in
either the spring or the fall .
The Agency's risk/benefit assessment of Amber, required by FIFRA, found
that the data base for adverse effects to human health, as well as birds, fish
and other marine organisms is essentially complete, and does not indicate this
chemical is likely to pose unreasonable adverse effects. The only identified
potential adverse effect of Amber is damage to non-target plants
(phytotoxicity) which may occur through drift of if contaminated ground water
were used for irrigation purposes. At this time, the weight of evidence does
not show that Amber is likely to pose unreasonable risks and the product was
During the two-year period of registration, the registrant will complete
further studies of the chemical's fate and effects. In addition, the
registrant has agreed that at the end of the two-year registration period, if
the leaching potential for Amber is the same or greater than the current
status following the review of additional data, any subsequent registrations
for this chemical will be permitted only in states with an EPA-approved State
Management Plan (SMP) in place. In the meantime, the registrant is under the
obligation to work with the states in which Amber is registered for use to
develop specific SMPs.
During the review of the Registrant's data, the Agency had several
concerns focusing on data gaps and Amber's leaching potential into ground
water. Since its registration, several state officials have expressed
concerns and stated that the Agency's decision on Amber shows a lack of
commitment to the Pesticides and Ground Water strategy and pollution
prevention. These concerns and issues are discussed later in this paper.
The Office of Pesticide Programs has prepared this paper to highlight the
Agency's rationale for the decision to issue a conditional registration for
Amber. Specifically, the paper will cover the following areas:
-- EPA's evaluation of Ciba-Geigy's application to register Amber
-- Options the Agency considered in making the decision
-- EPA's final decision on registration
-- Registration conditions and special restrictions
-- Concerns and Issues raised regarding the registration of Amber
EPA'S EVALUATION OF CIBA-GEIGY'S APPLICATION
The Agency bases registration decisions for new pesticides on its
evaluation of test data provided by applicants. Required studies include
testing to show whether a pesticide has the potential to cause adverse effects
in humans and the environment. Potential human risks include acute reactions
such as toxic poisoning, or skin and eye irritation, as well as possible long-
term effects like cancer, birth defects, or reproductive system disorders.
Evaluation of environmental risks take into account the fate and transport of
the pesticide through the environment and potential adverse effects to non-
Summarized below are the basic conclusions EPA reached in evaluating the
data and proposed label restrictions provided by Ciba-Geigy in its application
to register Amber:
-- All data requirements for both the technical and the formulation have been
-- All data requirements for the proposed food uses have been satisfied in
support of the establishment of tolerances.
Health Effects Data:
-- Toxicological data was reviewed and determined to be sufficient to support
unconditional registration of Amber for food uses. The data submitted
showed that Amber is not carcinogenic or mutagenic, and did not cause
reproductive or developmental toxicity under testing conditions.
A reference dose (Rfd) was established, based-on subtle chronic effects
observed in long-term animal tests.
Ecological Effects Data:
-- Data requirements to support registration for a terrestrial food crop use
were satisfied. Based on review of required studies, the Agency concluded
that Amber is practically nontoxic to birds, fish, aquatic invertebrates,
honey bees, estuarine species, and only slightly toxic to mysid shrimp and
-- The requirements for non-target plant data were partially satisfied by the
applicant. However, the Agency is concerned with a potential increase in
hazard to nontarget plants, and has determined that Non-target Area
Phytotoxicity testing will be needed. The Agency has reserved these
requirements until protocols are developed.
Environmental Fate and Ground-Water Data:
-- The data requirements for environmental fate and ground water were only
partially complete. These requirements include: photodegradation in soil,
mobility in soil, and confined accumulation studies on rotational crops.
The data requirements for terrestrial field dissipation and spray drift
studies were not satisfied either. These studies had numerous deficiencies
and must be repeated.
-- Ciba-Geigy voluntarily submitted an interim small-scale ground-water
monitoring study, conducted at a highly vulnerable site in Kansas. They
also submitted results of PRZM simulation modeling based on the conditions
at the small-scale ground-water study site. Based on the ground-water
monitoring study results, the modeling results submitted by the registrant,
and the Agency's own modeling results, EPA concluded that Amber may
leach to ground water at concentrations of up to a few ppb annually at
sites with permeable soils and shallow ground water. Further, the
submitted data were inadequate to determine whether leaching to ground
water is likely at less vulnerable sites.
Proposed Labeling Restrictions:
-- Ground Water Advisory: In its application, Ciba-Geigy proposed a label for
Amber bearing a ground-water advisory statement and several timing and
geographical restrictions such as "Use Amber to control weeds in wheat,
barley, and fallow cropland in the following 18 States only: AZ, CO, ID,
KS, MN, MO, MT, ND, NE, NM, NV, OK, OR, SD, TX, UT, WA, AND WY." The
statements are to ensure that Amber is to be used on dryland cereals and
fallow fields only.
-- Spray Drift: The proposed label also included precautions to minimize
drift and address weed resistance to sulfonylurea herbicides. These
statements are similar to labels of previously registered sulfonylurea
In making the final decision, EPA considered the following major options,
subject to a combination of conditions:
-- Register Amber
Subject to conditions such as:
-- Requiring appropriate label restrictions (i.e., adding a ground
water advisory, allowing ground applications only, etc.)
-- Filling data gaps (i.e., soil mobility, spray drift, etc.)
-- Requiring additional monitoring studies
-- Requiring SMPs, when EPA finalizes guidance documents
-- Reevaluating the data base for the entire sulfonylurea class of
-- Do Not Register Amber
-- Until all data gaps are filled
-- Until the sulfonylurea class of compounds are reevaluated
EPA'S FINAL DECISION
After evaluating Ciba-Geigy's application, the Agency concluded that
granting a registration for Amber is unlikely to result in unreasonable
adverse effects during the next two years. At the same time, due to gaps in
data available, the Agency is unable to determine that granting a registration
to Amber for a period in excess of two years would not result in unreasonable
adverse effects on the environment. There is more the Agency needs to know
about Amber, the other sulfonylurea pesticides, and ground-water protection
measures before the Agency could determine that long-term registration of
Amber would not pose unreasonable risks to the environment.
Therefore, EPA issued a two-year conditional registration that permits
the use of Amber on wheat, barley and fallow cropland but with several
labeling restrictions and special conditions to address the issues that came
up in evaluating the registrant's application.
REGISTRATION RESTRICTIONS AND SPECIAL CONDITIONS:
The restrictions and special conditions EPA imposed on Amber's
conditional registration are listed below:
-- States: The following statement authorizing its use only in 18 western
states with generally dry growing seasons appears on the label: "Use Amber
to control weeds in wheat, barley, and fallow cropland in the following
states only: AZ, CO, ID, KS, MN, MO Atchison, Barton, Bates, Buchanan,
Cass, Holt, Jackson, Jasper, McDonald, Newton, Platte, and Vernon
counties only), MT, ND, NE, NM, NV, OK, OR, SD, TX, UT, WA, AND WY.
Do not use Amber in the San Luis Valley of Colorado, in sections of WA and
OR west of the Cascade Mountains, or in Benton County, WA. In WA,
abide by all sulfonylurea aerial application rulings in effect by the
Washington Department of Agriculture."
-- Drift Statements: The following statement appears on the label:
"Drift from aerial applications of the herbicide is likely to result in
damage to plants adjacent to the treatment site. This damage can occur at
levels below the concentrations that can be detected with chemical
analysis." This statement is accompanied by label restrictions for aerial
application to reduce drift specifying conditions, methods, and equipment
that reduce drift potential including maximum spray and pressure, nozzle
types, minimum spray volume, spray boom configuration, spray boom length
relative to wing length, aircraft height and aircraft types.
-- Ground-Water Advisory: The following ground water advisory statement
appears on the label: "Amber has been identified in ground water sampling
from a field research study conducted under vulnerable conditions. There is
the possibility that Amber may leach through soil to ground water,
especially where soils are coarse and ground water is near the surface.
Consult with pesticide state lead agency or local agricultural agencies for
information regarding soil permeability and aquifer vulnerability in your
-- Additional Statements: The following additional statements appear on the
label as well: (1) Do not use in chemigation systems; (2) Do not apply
when rain in expected within 24 hours; (3) Rainfall or irrigation,
particularly when it occurs soon after Amber application, will promote the
movement of Amber residues through the soil profile.
Conditions of Registration:
-- State Management Plans: During the period of registration, Ciba-Geigy has
agreed to work with the states in which the pesticide will be used to
develop specific state management plans. The company also agreed that at
the end of the two year registration period, if the leaching potential for
Amber appears to be the same or greater than the current status following
the review of additional data on this pesticide, any subsequent
registration for this chemical will require the label to state that "use of
Amber is permitted only in states which have an EPA approved State
Management Plan in place."
-- Data Requirements: Ciba-Geigy has agreed to update the following
supplemental studies: Soil Mobility Study, Soil Photodegradation Study and
the Confined Rotational Crop Study. In addition, the company has agreed to
generate the following studies that have been identified by the Agency as
data gaps: Spray Drift Study (field), Spray Drift Study (droplet),
Terrestrial Field Dissipation, Small Scale Prospective Ground Water
Monitoring Study, and Tier III Phytotoxicity Studies (aquatic and
-- Voluntary Cancellation: Ciba Geigy has agreed to voluntarily cancel the
registration at expiration date and to waive all hearing rights. Thus an
EPA action will not be necessary if the data are not satisfactory.
CONCERNS AND ISSUES RAISED:
In reviewing the manufacturer's application, EPA had several areas of
-- Several data gaps existed in the information presented by Ciba-Geigy which
must be filled to warrant final registration of this compound. The
Registrant is required as a condition of registration to conduct the
following studies and testing:
Bioaccumulation in fish;
Soil mobility study;
Soil photodegradation study;
Rotational crops confined accumulation study;
Spray drift studies;
Terrestrial field dissipation;
Tier III nontarget phytotoxicity testing.
-- Amber had been shown to leach to ground water under certain vulnerable
hydrogeological conditions. Since there are no known health risks
associated with the chemical, contamination of drinking water is not an
issue. However, leaching may pose a potential ecological risk to non-target
plants if such ground water were applied to the plants through irrigation.
-- Based on laboratory data, the potential for Amber to leach does not appear
greatly different from that of the other herbicides of this class -- the
sulfonylureas -- some of which have been registered since the mid-1980's.
EPA is not aware of any phytotoxic damage attributed to ground water
contaminated by a sulfonylurea chemical. The Agency believes that the risk
is low for ground water contamination associated with the crop and
geographic limitations imposed by the conditional registration.
-- Further, Amber is likely to be used primarily as an alternative to
currently-registered sulfonylurea pesticides. Registration of Amber is not
expected to result in a significant increase in the amount of sulfonylurea
products used during the next two years.
-- The data submitted by the Registrant for spray drift had numerous
deficiencies and did not provide sufficient information to determine if the
proposed label restrictions will minimize drift to non-target plants during
aerial applications. EPA has required additional drift studies for Amber as
a condition of its registration.
Level Playing Field:
-- The Agency has previously registered other sulfonylureal products for
pesticidal use, however, we have not been consistent in imposing data
requirements concerning registration of this class of compounds. During the
period of Amber's conditional registration, the Agency plans to examine the
potential risks of drift and groundwater contamination from use of Amber as
well as the other sulfonylureal products.
-- At the end of two-years, the Agency expects to be in a better position to
determine the risks of drift and ground water contamination associated with
the use of Amber and the other sulfonylureal pesticides and whether
additional actions need to be taken to mitigate those risks.
Several state official have expressed concerns and raised a number of
issues with the Agency's decision to register Amber. The Agency considered
many of these during the process of registering Amber. Beyond those issues
and concerns listed above, states expressed concern regarding the following:
Consistency with Pesticides and Ground-Water Strategy:
-- A state official has noted that the decision to register Amber appears to
directly contradict EPA's Pesticides and Ground-Water Strategy which
indicates the need for a strong emphasis on prevention. Additionally, the
Agency seems to be showing an unwillingness to use the registration
process for pollution prevention.
-- EPA believes that the Amber decision is consistent with the Agency's
ground water protection policies as well as the mandates of pesticide law
-- In both the Pesticides and Ground-Water Strategy and the Agency's overall
"Strategy for the 1 990's", it is a central premise that, given the
localized nature of ground water, prevention should be achieved by the
states taking a lead role in tailoring risk reduction measures to local
-- EPA policy does not advocate federal programs or prohibitions as the
method of first resort for dealing with a pesticide which may pose
potential risks to ground water. Rather, the Agency has stressed the
identification of potential risks, and affirmed the states' lead role in
identifying vulnerable ground waters and taking localized measures to
reduce risks, such as designating wellhead protection areas or designing
state management plans for pesticides.
-- Regarding the pesticide registration process, the Pesticide Strategy does
describe denial of registration for a new chemical as an-available option,
but only if the overall weight of evidence shows that the potential risks
probably can not be adequately managed through labeling, restricted use
classification or SMPs.
-- Under the risk/benefit standard of FIFRA, the existence of an endpoint of
concern is not sufficient by itself to determine whether a pesticide should
be registered. Instead, FIFRA requires that any registration decision take
into account the full range of risk and benefit considerations on a case-
by-case basis .
State Management Plans (SMPs):
-- State officials have raised a question as to whether the Agency should
withhold a registration for a new pesticide like Amber until SMPs are
available to be implemented. Cost implications for developing SMPs for
each new compound that leaches to ground water was also raised.
-- The Pesticides Strategy does envision that some new chemicals in the future
are likely to be registered on condition that approved SMPs will be in
-- EPA is not in a position to set such a condition now, however, since most
states are in the early stages of developing generic SMPs and final
guidance on SMPs has yet to be issued. Moreover, in the case of Amber, EPA
has not made a final decision that SMPs will be necessary; the registrant
may rebut our concern by submitting additional studies.
-- EPA has strongly encouraged the registrant to work with states to develop
SMPs for Amber, since this is a likely outcome. Our intention is to have
the registrant actively support this method of keeping their product on the
market, and to get a start on designing SMPs now so that it will be an
available option two years from now. The registrant's involvement should
ease the potential burden to the states that choose to pursue development
of SMPs for Amber, if indeed they are required in the future.
-- Regarding general cost implications for developing SMPs for new compounds
identified as leachers, it is not appropriate to assume that each new
chemical with leaching potential will require an SMP. The risks and
benefits for each new chemical will be evaluated on a case-by-case basis
and the range of EPA's regulatory options considered, including restricting
use or requiring the development of an SMP.
Coordination with the Office of Water:
-- A state official has asked the extent to which the Office of Water is
consulted regarding registration decision for new products which are found
to have a high leaching potential.
-- In matters pertaining to ground-water policy, including specific pesticide
registration decisions, there needs to be coordination between the
pesticides and water offices. The Office of Ground Water and Drinking Water
(OGWDW) is represented on the pesticide working groups that are pursuing
implementation of the Pesticides and Ground-Water Strategy.
-- In the case of Amber, since there was no concern about health risks for
Amber, the pesticide program consulted minimally with the water office.
We will ensure in the future that the water office, specifically, OGWDW, is
consulted more fully on specific decisions, such as Amber, that raise
relevant policy issues.