United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-94-017
September 1994
R.E.D. FACTS
Pesticide
Reregistration
Use Profile
Disodium
cyanodithioimido-
carbonate (DCDIC)
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 reregi strati on, 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 reregi strati on, EPA announces this and
explains why in a Reregi strati on Eligibility Decision (RED) document. This
fact sheet summarizes the information in the RED document for reregi strati on
case 3065, disodium cyanodithioimidocarbonate or DCDIC.
Disodium cyanodithioimidocarbonate or DCDIC is a microbicide/
microbistat used in water treatment systems. Specifically, it is used as an
industrial biocide and slimicide to control slime-forming bacteria, algae and
fungi in food processing water systems (cane and beet sugar mills), pulp and
paper mill water systems, other commercial/industrial water cooling systems,
and secondary oil recovery injection water. DCDIC is formulated as a soluble
concentrate/liquid, and is applied through use of a measuring container,
metering pump or drip-feed device.
Current use practice limitations prohibit discharge of effluent containing
DCDIC into sewage systems without notifying the sewage plant authority,
and into lakes, streams, ponds, estuaries, oceans or public waters except in
accordance with an NPDES permit.
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Regulatory
History
Human Health
Assessment
DCDIC was registered in the U.S. as early as 1957 for use as an
industrial bactericide and slimicide. EPA issued a reregi strati on Phase 4 Data
Call-In (DCI) in September 1992, requiring product chemistry, toxicology,
ecological effects and environmental fate data. Currently, 57 pesticide
products are registered which contain the active ingredient DCDIC.
Toxicity
DCDIC generally is of moderate acute toxicity but causes eye irritation
and has been placed in Toxicity Category I (indicating the greatest degree of
acute toxicity) for this effect. DCDIC is in Toxicity Category II for acute oral
and primary dermal effects, and Toxicity Category III for acute dermal and
inhalation effects. (Toxicity Category I indicates the greatest degree of acute
toxicity and Category IV the least.)
In a subchronic toxicity study using rats, dermal irritation was observed
at all doses but systemic effects were noted only at the highest dose levels.
No gross internal organ effects were observed at any dose.
In two developmental toxicity studies using rabbits and rats, DCDIC
caused both maternal and fetal effects at and above mid-dose. No definitive
determination could be made as to whether the fetal effects observed were
caused by DCDIC directly or occurred indirectly as a result of maternal
toxicity.
DCDIC was not mutagenic in two out of three required studies.
Although EPA does not believe that there is a genetic risk, the Agency is
requiring that the third study be repeated as confirmatory information.
Dietary Exposure
Food additive tolerances (maximum limits for residues in processed
foods) have been established by the Food and Drug Administration (FDA) for
the sugar beet and sugar cane mill uses of DCDIC (please see 21 CFR
173.320). EPA defers to FDA regarding this dietary exposure to DCDIC.
Additional food additive tolerances have been set for residues of DCDIC in
food grade paper, paperboard (21 CFR 176.300) and adhesives (21 CFR
175.105). However, these uses are neither active nor supported for
reregi strati on.
Occupational and Residential Exposure
Pesticide handlers-mixers, loaders and applicators—may be exposed to
DCDIC when adding it to the metering pumps and measuring containers of
food processing or industrial water systems.
EPA's exposure assessment, which considered combined dermal and
inhalation exposure, indicates that the highest risk appears to result from the
open pour application of this pesticide to cooling tower water. The margin of
exposure (MOE) for this use pattern is only 38, significantly less than the
100-fold margin believed to be acceptable. However, due to the worst-case
assumptions involved in the analysis, the actual risk to workers is expected to
be at least 10% less, making the MOE 380 or more. Risks of developmental
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toxicity to workers are expected to be low when appropriate protective
equipment and clothing are used.
To mitigate acute as well as chronic toxicity hazards during open
pouring of DCDIC, use of personal protective equipment (PPE) is required
including protective eyewear, chemical resistant gloves, footwear, socks, a
long-sleeved shirt, long pants and a respirator.
Post-application exposure is minimal posing negligible risk to workers.
Residential exposure and risk to homeowners are not expected, based on the
pesticide's use patterns.
Human Risk Assessment
Although DCDIC has two food uses (sugar beets and sugar cane), both
are under FDA's purview. EPA defers to FDA regarding DCDIC's dietary
risk.
The open pouring method of applying DCDIC to cooling tower water
appears to pose the greatest risk of developmental toxicity to applicators.
However, EPA's worst case exposure assessment probably results in an
overestimate of risk; the actual risk to workers is expected to be low when
appropriate protective equipment and clothing are used, as required by the
RED document. Post-application exposure and risk are likely to be minimal.
Residential exposure and risk to homeowners are not anticipated based on
DCDIC's use patterns.
Environmental
Assessment
Environmental Fate
The secondary oil recovery use of DCDIC normally would require
extensive data regarding potential ground water impacts. However, properly
encased injection wells preclude contact between materials placed down the
well and any aquifer in the area; so EPA believes the chemical is not likely to
present a hazard to ground water through this use. Other aquatic industrial
uses carry National Pollutant Discharge Elimination System (NPDES) permit
restrictions, limiting industrial discharges to acceptable levels for each site.
Ecological Effects
DCDIC is practically nontoxic to birds, no more than slightly toxic to
freshwater and estuarine/marine fish, and moderately to highly toxic to
aquatic/estuarine invertebrates.
Ecological Effects Risk Assessment
Because of its current use patterns, DCDIC is not likely to be found at
levels of concern in the terrestrial environment, or to pose risks to birds.
EPA used a Tier Ic Estimated Environmental Concentration (EEC)
model to assess residue levels occurring immediately downstream from
industrial discharge sites. High exposure and typical exposure scenarios were
developed for each use site. Typical exposure case EECs do not exceed levels
of concern for any use sites; however, high exposure case EECs exceed levels
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Additional Data
Required
Product Labeling
Changes Required
of concern for aquatic invertebrates at some industrial cooling towers and
sugar mills. Thus, freshwater aquatic invertebrates may be at risk from
effluent at high exposure sites. Similarly, estuarine and marine aquatic
invertebrates may be at risk from effluent at high exposure industrial cooling
tower and oil recovery sites.
While the use of DCDIC as a pesticide is regulated by EPA's Office of
Pesticide Programs (OPP) under the federal pesticide law, FIFRA, the
discharge of effluent containing DCDIC to surface waters is regulated under
the NPDES permit program administered by EPA's Office of Water (OW)
with the states. The NPDES process takes local conditions into account in
issuing permits for the discharge of pollutants to bodies of water. EPA's OPP
and OW will share information and cooperate in overseeing the use of
biocides such as DCDIC.
Endangered Species
The high exposure case scenarios described above exceed the levels of
concern for endangered fish at certain industrial sites, and those for
endangered aquatic invertebrates at all sites. Effluent containing DCDIC
should not be discharged into aquatic habitats where endangered species are
known to live.
EPA is working with the U.S. Fish and Wildlife Service to develop a
program to identify pesticides whose use may cause adverse impacts on
threatened and endangered species, and to implement mitigation measures that
will eliminate the adverse impacts. This program will require labeling that
directs users to county-specific bulletins for information about use restrictions
to protect endangered and threatened species in the county.
The generic data base for DCDIC is substantially complete. However,
for confirmatory purposes, EPA is requiring an additional mutagenicity study
and data indicating the products of hydrolysis. The Agency also is requiring
product-specific data, including product chemistry and acute toxicity studies,
as well as revised Confidential Statements of Formula and revised labeling for
reregi strati on.
All end-use products containing DCDIC must comply with EPA's
current pesticide product labeling requirements. In addition:
Effluent Discharge Statement - All end-use (and manufacturing use)
products that may be contained in an effluent discharged to the waters of the
U.S. must bear the following revised effluent discharge statement:
"Do not discharge effluent containing this product into lakes, streams,
ponds, estuaries, oceans or other waters unless in accordance with the
requirements of a National Pollutant Discharge Elimination System
(NPDES) permit and the permitting authority has been notified in
writing prior to discharge. Do not discharge effluent containing this
product to sewer systems without previously notifying the local sewage
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treatment plant authority. For guidance contact your State Water Board
or Regional Office of EPA."
PPE Requirements - All end-use product labels must bear the following
statement:
"For open pouring of this product, workers must wear eyewear,
chemical-resistant gloves, footwear, socks, long-sleeved shirt, long
pants and a respirator with either an organic-vapor-removing cartridge
with a prefilter approved for pesticides (MSHA/NIOSH approval
number prefix TC-23C) or a canister approved for pesticides
(MSHA/NIOSH approval number prefix TC-14G)."
Regulatory
Conclusion
The use of currently registered products containing DCDIC in
accordance with approved labeling will not pose unreasonable risks or adverse
effects to humans or the environment. Therefore, all uses of pesticide
products containing DCDIC are eligible for reregi strati on.
Although there is some concern about potential effects on aquatic
organisms exposed to effluent from industrial use of DCDIC, discharge of
such effluent generally will not cause unreasonable adverse effects on the
environment. EPA's OPP and OW will share information to improve the
regulation of DCDIC's use at specific sites across the country.
Products containing DCDIC 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, and after the other active ingredients in these products also are
determined to be eligible for reregi strati on.
For More
Information
EPA is requesting public comments on the Reregi strati on Eligibility
Decision (RED) document for DCDIC 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 DCDIC 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 reregi strati on program, the
DCDIC RED, or reregi strati on of individual products containing DCDIC,
please contact the Special Review and Reregi strati on 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
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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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