United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-94-026
September 1994
R.E.D. FACTS
Bentazon
Pesticide
Registration
Use Profile
Regulatory
History
All pesticides sold or distributed in the United States must be registered
by EPA, based on scientific studies showing that they can be used without
posing unreasonable risks to people or the environment. Because of advances
in scientific knowledge, the law requires that pesticides which were first
registered years ago be reregistered to ensure that they meet today's more
stringent standards.
In evaluating pesticides for reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human health
and environmental effects of each pesticide. The Agency imposes any
regulatory controls that are needed to effectively manage each pesticide's risks.
EPA then reregisters pesticides that can be used without posing unreasonable
risks to human health or the environment.
When a pesticide is eligible for reregistration, EPA announces this and
explains why in a Reregistration Eligibility Decision (RED) document. This
fact sheet summarizes the information in the RED document for reregistration
case 0182, bentazon, which includes bentazon technical and sodium bentazon,
the active ingredient in end-use pesticide products.
Bentazon, also known by its trade name Basagran, is a selective herbicide
that is used after seedlings have emerged to control broadleaf weeds and sedges
among food and feed crops including alfalfa, beans, corn, peanuts, peas,
peppers, peppermint, rice, sorghum, soybeans and spearmint. Bentazon also
is registered for use on ornamental lawns and turf. Most bentazon used in the
U.S. (73%) is applied to soybean crops.
Bentazon may be applied either aerially or using ground equipment
(except to lawns and turf, which may be treated using ground equipment only).
Formulations include a flowable concentrate and a soluble concentrate/liquid.
Use practice limitations prohibit applying bentazon through any type of
irrigation system; discharging effluent containing the product into sewage
systems or bodies of water; using treated plants for feed or forage; and treating
crops/sites within 30 to 75 days of harvest or 12 to 50 days of grazing.
EPA issued a Registration Standard for bentazon in September 1985
(NTIS #PB86-159563). An August 1990 Data Call-in (DCI) required
additional data on terrestrial and aquatic animal effects, environmental fate,
toxicology, residue chemistry, and plant protection. Products currently
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registered contain bentazon alone or in combination with atrazine.
Human Health
Assessment
Toxicity
Bentazon is slightly acutely toxic by the oral, dermal and inhalation
routes, and has been placed in Toxicity Category III (the second-to-lowest of
four categories) for these effects. It is a skin sensitizer in guinea pigs.
In a subchronic toxicity study using rats, bentazon caused a variety of
effects at the highest dose tested including reductions in body weight gain, an
increase in blood clotting times, and increased kidney and liver weights.
A chronic toxicity study in beagle dogs produced adverse effects at the
two highest dose levels including clinical signs of toxicity, anemia-like changes
in blood, depressed body weight gains, intestinal inflammation and congestion
of the small intestine and spleen.
In two combined chronic toxicity and carcinogenicity studies using rats
and mice, bentazon caused no compound-related increases in tumors.
Numerous other adverse effects were observed at the highest dose levels,
however, including effects on blood clotting and to the testes, pancreas and
liver, changes in kidney, thyroid and pituitary gland weights, reduced body
weight gain, and hemorrhage in the liver and heart. Based on these studies,
bentazon was classified as a "Group E" carcinogen, that is, a compound that
shows evidence of non-carcinogenicity for humans.
In a developmental toxicity study using rats, bentazon did not cause
maternal toxicity but at the highest dose tested caused an increase in
postimplantation loss and effects on bone development in fetuses. In rabbits,
bentazon caused some evidence of both maternal toxicity and developmental
toxicity. In a reproductive toxicity study using rats, at the highest dose levels,
bentazon caused a decrease in body weights of pups during lactation and
reductions in food consumption and weight gain, as well as kidney and liver
effects in parents. Bentazon is not mutagenic.
Dietary Exposure
People may be exposed to residues of bentazon through the diet.
Tolerances or maximum residue limits have been established for raw
agricultural commodities including various types of beans, corn, mint, peanuts,
peas, peppers, rice, sorghum and soybeans (please see 40 CFR 180.355(a));
for animal commodities including milk, eggs, and the fat, meat and meat
byproducts of cattle, goats, hogs, poultry and sheep (see 40 CFR 180.355(b);
and for the processed commodity spent mint hay (see 40 CFR 186.375). A
tolerance for rice hulls is proposed. EPA has reassessed the existing bentazon
tolerances and found that several changes and corrections are needed, as
explained in the RED document.
EPA has assessed the acute and chronic dietary risks posed by bentazon.
In the chronic risk analysis, the Agency used a Reference Dose (RfD), or
amount believed not to cause adverse effects if consumed daily over a 70-year
lifetime, of 0.03 mg/kg bwt/day (milligrams/kilogram of bodyweight/day).
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This RfD is based on a No Observed Effects Level (NOEL) of 3.2 mg/kg
bwt/day established in the dog feeding study described earlier, plus an
uncertainty factor of 100. For the overall U.S. population and 22 subgroups,
exposure from all current tolerances represents 2.2% of the RfD. The
exposure level of the most highly exposed subgroup, non-nursing infants less
than one year old, represents 8.1% of the RfD. Based on these estimates,
chronic dietary risk is not of concern.
In the acute dietary risk analysis, EPA used a NOEL derived from the
developmental toxicity study in rats, described earlier. The subgroup of most
interest in terms of developmental toxicity, females aged 13 and above (women
of child bearing age), have a margin of exposure (MOE) of 500. This means
they receive approximately 1/500* the amount that represents the NOEL in
animals. Thus, acute dietary risk from bentazon is not of concern.
Occupational and Residential Exposure
Based on current use patterns, workers may be exposed to bentazon
during and after applications in agricultural and other settings. The Agency
was concerned about developmental toxicity effects resulting from this
exposure. Margins of Exposure (MOEs) were estimated for short and
intermediate term exposure scenarios involving mixing, loading and applying
bentazon using both ground and aerial application methods. The resulting
MOEs ranged from 1,714 to 100,000; all are well over 100, the margin
regarded as acceptable from a safety standpoint. Therefore, the personal
protective equipment (PPE) required for early entry is the minimum PPE
required under the Worker Protection Standard (WPS): coveralls, chemical-
resistant gloves, shoes and socks.
The risk to homeowners who handle bentazon is expected to be lower
than that of people who handle the pesticide occupationally.
Human Risk Assessment
Bentazon is slightly acutely toxic by all routes (Toxicity Category III)
and is a skin sensitizer. It is classified as a "Group E" carcinogen—a chemical
showing evidence of non-carcinogenicity to humans, but causes some
developmental toxicity effects in rats and rabbits.
Bentazon is used on a variety of food crops, and people may be exposed
to residues through their diets. Based on EPA's acute and chronic dietary risk
assessments, however, dietary exposure to the bentazon uses supported for
reregistration is not of concern.
Although the Agency has concerns about possible developmental toxicity
effects among workers exposed to bentazon, these concerns are minor based
on our assessment that worker risks are low. There are no concerns that
warrant the establishment of personal protective equipment (PPE) requirements
beyond those required by the Worker Protection Standard (WPS) or appearing
on existing product labels for non-WPS uses.
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Environmental Environmental Fate
AsSGSSITIGnt Dissipation of bentazon is dependent on microbe-induced degradation,
leaching and surface water runoff. Bentazon is moderately resistant to
degradation in aerobic mineral soils. Degradation in aquatic environments is
dependent on photolysis. Degradation in soil is controlled by processes
involving microbes in the presence of oxygen. Bentazon has a low binding
affinity to soil and therefore may leach into ground water and runoff into
surface waters. Leaching did not appear to be a major route of dissipation in
field studies, however. Bentazon dissipates rapidly under typical use
conditions.
The soil degradates of bentazon include AIBA, which is very mobile but
not persistent, and N-methylbentazon which is not mobile. These compounds
should not pose a threat to ground water.
Environmental Fate Assessment
EPA concludes that, in addition to surface runoff, leaching through the
soil profile also is a major route of dissipation for bentazon in the environment.
Bentazon exceeds levels of concern for ground water quality, and also may
impact the quality of surface water. Possible chronic effects of long-term
drinking water exposure prompted EPA's Office of Water to establish a
lifetime Health Advisory (HA) of 20 parts per billion (ppb), which will likely
be increased to 200 ppb soon. However, bentazon is not regulated under the
Safe Drinking Water Act (SDWA), no Maximum Contaminant Level (MCL)
has been established, and water supply systems are not required to sample or
analyze for its residues.
Bentazon has been detected in well water in four out of eight states
sampled including California (with the greatest number of detections, extending
over 11 counties), Florida, Missouri and Virginia. EPA is requiring a small-
scale prospective ground water monitoring study to establish the conditions
under which bentazon is prone to leach to ground water during normal
agricultural use. The Agency also is requiring a ground water label advisory
for bentazon to minimize its adverse effects on ground water. The registrant
has agreed to prepare educational materials for end users, dealers and
distributors regarding ground and surface water protection.
EPA also is requiring spray drift studies as confirmatory information,
and in the future may require drift-related labeling statements for bentazon
products applied aerially to agricultural crops.
Ecological Effects
Bentazon is slightly toxic to birds on an acute oral and subacute dietary
basis, and exceeds the level of concern for avian chronic effects. Bentazon is
slightly toxic to small mammals on an acute basis, and is practically nontoxic
to honeybees. Bentazon also is practically nontoxic to cold and warm water
fish, aquatic invertebrates and estuarine/marine organisms. Bentazon poses a
low risk to aquatic plants but may represent a hazard to terrestrial and semi-
aquatic plants.
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Additional Data
Required
Product Labeling
Changes Required
Ecological Effects Risk Assessment
EPA concludes that the use of bentazon as an herbicide will not pose a
serious environmental threat. Bentazon poses a chronic reproductive health
risk to birds. However, the registrant has agreed to lower the maximum
seasonal application rate from four to two pounds per acre, to reduce the
potential for this risk. Although it is slightly toxic to birds and small mammals
on an acute and subacute basis, bentazon is expected to pose minimal
acute/subacute risks to both endangered and nonendangered birds and mammals
as a result of its current uses. Since it is a herbicide, bentazon is expected to
pose a risk to non-target terrestrial and semi-aquatic plants near treated sites.
No hazard to aquatic animals or honeybees is anticipated.
EPA is requiring additional generic product chemistry, residue
chemistry, toxicology, environmental fate and ecological effects studies to
confirm its regulatory assessments and conclusions regarding bentazon. The
Agency also is requiring product-specific data including product chemistry and
acute toxicity studies, revised Confidential Statements of Formula (CSFs) and
revised labeling for reregistration.
All bentazon end-use products must comply with EPA's current pesticide
product labeling requirements. The following statements, some of which may
be on some existing product labels, are now required on all labels as specified
below.
Environmental Hazard Statement
Non-residential end-use product labeling must bear the following
statement for crayfish and catfish commercial farms:
"For terrestrial uses only, do not apply directly to water, or to areas
where surface water is present or to intertidal areas below the mean high
water mark. Do not contaminate water when disposing of equipment
washwater or rinsate."
Ground Water Label Advisory
To minimize bentazon contamination of ground water, the following
statement is required on all end-use product labeling:
"This chemical is known to leach through soil into groundwater under
certain conditions as a result of agricultural use. Use of this chemical in
areas where soils are permeable, particularly where the water table is
shallow, may result in ground water contamination."
Worker Protection Requirements
• The following entry restriction is required for all non-WPS occupational
uses of bentazon:
"Do not enter or allow others to enter the treated area until sprays have
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dried."
• The following entry restriction is required for all homeowner products:
"Do not allow persons or pets to enter the treated area until sprays have
dried."
• The following labeling statements are required for all bentazon products
intended primarily for occupational use, including uses both within and not in
the scope of the WPS.
Application Restrictions:
"Do not apply this product in a way that will contact workers or other
persons, either directly or through drift. Only protected handlers may
be in the area during application."
Engineering Controls:
"When handlers use closed systems, enclosed cabs, or aircraft in a
manner that meets the requirements listed in the Worker Protection
Standard (WPS) for agricultural pesticides (40 CFR 170.240(d) (4-6), the
handler PPE requirements may be reduced or modified as specified in the
WPS."
User Safety Requirements:
"Follow manufacturer's instructions for cleaning/maintaining PPE. If
there are no such instructions for washables, use detergent and hot water.
Keep and wash PPE separately from other laundry."
User Safety Recommendations:
"Users should wash hands before eating, drinking, chewing gum, using
tobacco, or using the toilet."
"Users should remove clothing immediately if pesticide gets inside.
Then wash thoroughly and put on clean clothing."
"Users should remove PPE immediately after handling this product.
Wash the outside of gloves before removing. As soon as possible, wash
thoroughly and change into clean clothing."
• Because bentazon is a skin sensitizer, the following statement must be
placed in the "Hazards to Humans and Domestic Animals" section of the
Precautionary Statements on the labeling of all end-use products:
"This product may cause skin sensitization reactions in some people."
Reduction in Application Rate
All bentazon labels must be amended to reflect a maximum seasonal
application rate of 2 Ibs ai/a (2 pounds active ingredient per acre).
Products Registered for Residential Use Only
The following label statement is required for all products intended for use
on lawns and turf:
"Do not apply directly to water. Do not contaminate water when
disposing of equipment washwater or rinsate."
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Regulatory
Conclusion
For More
Information
The use of currently registered pesticide products containing bentazon in
accordance with approved labeling will not pose unreasonable risks or adverse
effects to humans or the environment. Therefore, all uses of these products are
eligible for reregistration.
Bentazon products will be reregistered once the required confirmatory
generic data, product-specific data, revised Confidential Statements of Formula
and revised labeling are received and accepted by EPA.
Products that contain the active ingredient atrazine in addition to
bentazon will be reregistered when atrazine also is eligible for reregistration.
EPA is requesting public comments on the Reregistration Eligibility
Decision (RED) document for bentazon during a 60-day time period, as
announced in a Notice of Availability published in the Federal Register. To
obtain a copy of the RED document or to submit written comments, please
contact the Pesticide Docket, Public Response and Program Resources Branch,
Field Operations Division (7506C), Office of Pesticide Programs (OPP), US
EPA, Washington, DC 20460, telephone 703-305-5805.
Following the comment period, the bentazon RED document will be
available from the National Technical Information Service (NTIS), 5285 Port
Royal Road, Springfield, VA 22161, telephone 703-487-4650.
For more information about EPA's pesticide reregistration program, the
bentazon RED, or reregistration of individual products containing bentazon,
please contact the Special Review and Reregistration Division (7508W), OPP,
US EPA, Washington, DC 20460, telephone 703-308-8000.
For information about the health effects of pesticides, or for assistance
in recognizing and managing pesticide poisoning symptoms, please contact the
National Pesticides Telecommunications Network (NPTN). Call toll-free 1-
800-858-7378, between 8:00 am and 6:00 pm Central Time, Monday through
Friday.
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