United States Prevention, Pesticides EPA-738-F-95-006A
Environmental Protection And Toxic Substances June 1995
Agency (7508W)
R.E.D. FACTS
Terbuthylazine
PGStJCJdG All pesticides sold or distributed in the United States must be
R0TGClistration 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
appropriate 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 2645, terbuthylazine.
USG ProfilG Terbuthylazine is an algicide, microbicide and microbiostat used to
control slime-forming algae, fungi, and bacteria. It is registered for use in
commercial and industrial water cooling systems, and in residential and
commercial ornamental ponds, fountains and aquaria. Terbuthylazine is
formulated as a soluble concentrate/liquid, and is applied as a continuous
feed or intermittent slug treatment, using either open pouring or closed
system methods.
Use practice limitations currently require users to preclean systems
before applying the pesticide, and prohibit: discharge of effluent containing
the pesticide into sewage systems without notifying the sewage treatment
plant authority; discharging effluent containing the pesticide into lakes,
streams, ponds, estuaries, oceans, or public waters; use where treated
water will come into contact with lawns, trees, shrubs, or other desirable
plants since injury may result; and using water from treated systems for
irrigation or spraying of agricultural crops, lawns, or ornamental plants, or
for watering cattle, goats, hogs, horses, poultry or sheep, or for human
consumption.
-------
Regulatory
History
Human Health
Assessment
Initially, in 1975, terbuthylazine was registered as a herbicide in the
U.S., and several tolerances for residues in food and feed were established.
However, since no end-use products were registered for these uses, the
tolerances were revoked in 1992. Meanwhile, in 1986, algicide and
microbicide/microbistat end-use products were registered. EPA has issued
four Data Call-In notices for terbuthylazine. Five products currently are
registered.
Toxicity
Terbuthylazine generally is of relatively low acute toxicity. It has
been placed in Toxicity Category III, the second-to-lowest of four
categories, for acute oral, dermal, and inhalation effects. Terbuthylazine is
mildly to moderately irritating to the eyes, and slightly irritating to the skin,
and has also been placed in Toxicity Category III for these effects. It is not
a skin sensitizer.
In a subchronic toxicity study using rats, terbuthylazine caused
decreased body weight gain as well as decreased thymic, kidney and liver
weights. A study using rabbits resulted in decreased body weight gain and
food consumption, and mortality in one female. In another rabbit study, all
the animals developed difficulty in breathing, piloerection, sedation, curved
body posture, dermal irritation, and decreased body weight gain and food
consumption.
In chronic toxicity and carcinogenicity studies using mice and rats,
decreases in body weight gain and food consumption were observed. Two
studies using mice and rats caused no increase in tumors. However, a third
study using rats caused an increased incidence of testicular tumors in males
and mammary gland carcinomas in females, but only at a dose at which
excessive systemic toxicity also was observed. Based on this study, EPA's
Carcinogenicity Peer Review Committee has classified terbuthylazine as a
Group D carcinogen—one for which there is inadequate evidence to
determine carcinogenicity in humans.
Terbuthylazine caused no signs of developmental toxicity in a study
using rabbits. However, in a study using rats, maternal toxicity was
observed as reduced body weight gain and food intake, and developmental
toxicity was observed in the litter as a lack of bone formation in one toe.
Reproductive toxicity data is not available, but will be required if food uses
are proposed in the future. Available studies indicate that terbuthylazine is
not mutagenic.
Dietary Exposure
Dietary exposure to terbuthylazine is not expected since no products
with food uses currently are registered.
-------
Occupational and Residential Exposure
Workers may be exposed to terbuthylazine during applications in
commercial/industrial settings. In addition, workers may be exposed to this
pesticide after application, while cleaning or maintaining water cooling
towers, and other people (including children) may be exposed while wading
or swimming in treated ornamental ponds or fountains. Because of the use
patterns and dilution factors involved, however, EPA believes that post-
application exposure to terbuthylazine in both commercial and residential
settings is minimal.
Since terbuthylazine is associated with developmental toxicity effects,
EPA assessed the risks to workers who apply this pesticide using the open
pouring method compared to the metering pump method. The Agency
found that the risk to commercial applicators who routinely use the open
pouring method is unacceptable. Margins of Exposure (MOEs) for these
workers are very low for both typical and high use rates, both short- and
intermediate-term. However, MOEs for workers using closed pump
systems are well above 100, the margin generally considered acceptable.
MOEs for workers using both open pouring and metering pump methods in
residential settings also are acceptably high.
EPA therefore is prohibiting commercial applications of terbuthylazine
using the open pouring method, and is requiring use of closed systems along
with certain personal protective equipment (PPE), to reduce exposure and
risk to acceptable levels for all commercial uses.
Human Risk Assessment
Terbuthylazine is of relatively low acute toxicity, and is classified as a
Group D carcinogen because there is inadequate evidence to determine its
carcinogenicity in humans. However, it is associated with developmental
toxicity in a study using rats.
Terbuthylazine has no food-related uses at present so dietary exposure
is not of concern. However, workers are exposed while applying this
pesticide in commercial/industrial and residential settings, using open
pouring and closed system methods. EPA has found that the risk to
commercial/industrial workers using open pouring methods is unacceptable.
The Agency is prohibiting open pouring methods for commercial/industrial
uses of terbuthylazine, and requiring use of closed systems with PPE in
commercial/industrial settings.
Environmental Environmental Fate
AsSGSSITIGnt Terbuthylazine is stable to hydrolysis, and to aqueous photolysis. It
degrades very slowly under aerobic aquatic conditions, and will persist
under most aquatic conditions.
-------
Risk Mitigation
Additional Data
Required
Ecological Effects
Terbuthylazine is practically nontoxic to birds on an acute and
subacute dietary basis. However, it is moderately toxic to both cold and
warm water fish, slightly toxic to aquatic invertebrates, and highly toxic to
estuarine/marine invertebrates from acute exposures. Terbuthylazine is
expected to be phytotoxic to aquatic plants because it belongs to the triazine
family (which includes many herbicides), is released to waterways, and
dissipates slowly in the environment.
Ecological Effects Risk Assessment
No significant risks to birds or mammals are expected from use of
terbuthylazine. Although terbuthylazine is moderately toxic to fish and
slightly toxic to freshwater invertebrates, these species are not expected to
be at risk under typical use and exposure scenarios. In high exposure
situations, however, levels of concern for high risk, restricted use, and
endangered species are met or exceeded. Because its use patterns are not
associated with estuarine or marine environments, significant risk to
estuarine/marine invertebrates is not expected. Phytotoxicity to aquatic
plants is anticipated, and EPA has required relevant studies as confirmatory
data.
EPA is requiring the following risk mitigation measures for
terbuthylazine, as discussed earlier:
° To reduce risks to commercial/industrial applicators, EPA will
prohibit open pouring methods and require that only closed system methods
of application, with specified PPE, be used for commercial application of
terbuthylazine.
° To adequately mitigate potential risks to fish, freshwater invertebrates,
and aquatic plants from release of effluent to waterways:
• EPA will coordinate regulatory oversight of terbuthylazine under
FIFRA, the federal pesticide law administered by the Agency's Office
of Pesticide Programs, and the National Pollutant Discharge
Elimination System (NPDES) administered by the Office of Water in
conjunction with the states.
• EPA will require compliance with the Endangered Species
Protection Program when it goes into effect.
The generic database supporting terbuthylazine is substantially
complete. Confirmatory data measuring the toxicity of this pesticide to
aquatic plants were recently required of registrants, and must be submitted
to EPA by January 1996. 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.
-------
Product LabGling All terbuthylazine end-use products must comply with EPA's current
ChanQGS pesticide product labeling requirements, and with the following:
Red UJ r0d Effluent Discharge Labeling Statements
All end-use products that may be contained in an effluent discharged
to the waters of the U.S. or municipal sewer systems must bear the effluent
discharge labeling statements described in PR Notice 93-10.
Other Labeling Requirements
Except where indicated otherwise, the following statements must
appear on all end-use products containing terbuthylazine that are intended
primarily for industrial use:
Application Restrictions:
For products intended for industrial use:
"Open pouring of this product is prohibited."
"Mixing, loading, and application must be with a closed system (one
that prevents the chemical from contacting handlers or other persons)
and during handling of the chemical personal protective equipment
must be worn. Personal protective equipment includes a long-sleeved
shirt, long pants, shoes, socks, and chemical-resistant gloves. A
chemical-resistant apron must be immediately available during loading
and application and must be worn in case of a leak, spill, or other
exposure to the concentrate. "
For products intended for homeowner use:
"Persons that mix, load, or apply this product must wear a long-
sleeved shirt, long pants, shoes, socks, and chemical-resistant gloves. "
User Safety Requirements:
"Follow manufacturer's instructions for cleaning/maintaining Personal
Protective Equipment. If no such instructions for washables exist, use
detergent and hot water. Keep and wash personal protective
equipment 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 personal protective equipment immediately
after handling this product. Wash the outside of gloves before
removing. As soon as possible, wash thoroughly and change into
clean clothing."
Currently registered pesticide products containing the active ingredient
Conclusion terbuthylazine, labeled and used as specified in the RED document, will not
pose unreasonable risks or adverse effects to humans or the environment.
-------
Therefore, all uses of these products are eligible for reregistration.
Terbuthylazine products will be reregistered once the required product
specific data, revised Confidential Statements of Formula, and revised
labeling are received and accepted by EPA.
For MOTG EPA is requesting public comments on the Reregistration Eligibility
Information Decision (RED) document for terbuthylazine 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.
Electronic copies of the RED and this fact sheet can be downloaded
from the Pesticide Special Review and Reregistration Information System at
703-308-7224. They also are available on the Internet on EPA's gopher
server, GOPHER.EPA.GOV., or using ftp on FTP.EPA.GOV, or using
WWW (World Wide Web) on WWW.EPA.GOV.
Printed copies of the RED and fact sheet can be obtained from EPA's
National Center for Environmental Publications and Information
(EPA/NCEPI), PO Box 42419, Cincinnati, OH 45242-0419, telephone
513-489-8190, fax 513-489-8695.
Following the comment period, the terbuthylazine RED document also
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 terbuthylazine RED, or reregistration of individual products containing
terbuthylazine, 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.
------- |