Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov

Dithiopyr
Interim Registration Review Decision
Case Number 7225
December 2020
JL-
Approved by:
Mary Elissa Reaves, Ph.D.
Acting Director
Pesticide Re-evaluation Division
Date:	12-08-2020

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Table of Contents
I.	INTRODUCTION	3
A.	Summary of Dithiopyr Registration Review	4
B.	Summary of Public Comments on the Proposed Interim Decision and Responses	5
II.	USE AND US AGE	8
III.	SCIENTIFIC ASSESSMENTS	9
A.	Human Health Risks	9
1.	Risk Summary and Characterization	10
2.	Human Incidents and Epidemiology	13
3.	Tolerances	13
4.	Human Health Data Needs	13
B.	Ecological Risks	13
1.	Risk Summary and Characterization	14
2.	Ecological Incidents	17
3.	Ecological and Environmental Fate Data Needs	17
C.	Benefits	17
IV.	INTERIM REGISTRATION REVIEW DECISION	18
A.	Risk Mitigation and Regulatory Rationale	18
1.	Updated Labeling for Water Soluble Packages	18
2.	Enforceable Spray Drift Management	18
3.	Environmental Hazards	19
4.	Herbicide Resistance Management	20
5.	Label Clarifications	21
B.	Tolerance Actions	21
C.	Interim Registration Review Decision	21
D.	Data Requirements	21
V.	NEXT STEPS AND TIMELINE	22
A.	Interim Registration Review Decision	22
B.	Implementation of Mitigation Measures	22
Appendix A: Summary of Risk Mitigation for Dithiopyr	23
Appendix B: Labeling Changes for Dithiopyr Products	24
Appendix C: Endangered Species Assessment	29
Appendix D: Endocrine Disruptor Screening Program	30
2

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
I. INTRODUCTION
This document is the Environmental Protection Agency's (hereafter noted as EPA or the
Agency) Interim Registration Review Decision (ID) for dithiopyr (PC Code 128994, case 7225),
and is being issued pursuant to 40 CFR  155.56 and  155.58. A registration review decision is
the Agency's determination whether a pesticide continues to meet, or does not meet, the standard
for registration in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The Agency
may issue, when it determines it to be appropriate, an interim registration review decision before
completing a registration review. Among other things, the interim registration review decision
may determine that new risk mitigation measures are necessary, lay out interim risk mitigation
measures, identify data or information necessary to complete the review, and include schedules
for submitting the necessary data, conducting the new risk assessment and completing the
registration review. Additional information on dithiopyr, can be found in EPA's public docket
(EPA-HQ-OPP-2013-0750) at www.reeulations.eov.
FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandates the
continuous review of existing pesticides. All pesticides distributed or sold in the United States
must be registered by EPA based on scientific data showing that they will not cause
unreasonable risks to human health or to the environment when used as directed on product
labeling. The registration review program is intended to make sure that, as the ability to assess
and reduce risk evolves and as policies and practices change, all registered pesticides continue to
meet the statutory standard of no unreasonable adverse effects. Changes in science, public
policy, and pesticide use practices will occur over time. Through the registration review
program, the Agency periodically re-evaluates pesticides to make sure that as these changes
occur, products in the marketplace can continue to be used safely. Information on this program is
provided at http://www.epa.eov/pesticide-reevaluation. In 2006, the Agency implemented the
registration review program pursuant to FIFRA  3(g) and will review each registered pesticide
every 15 years to determine whether it continues to meet the FIFRA standard for registration.
EPA is issuing an ID for dithiopyr so that it can (1) move forward with aspects of the registration
review that are complete and (2) implement interim risk mitigation (see Appendices A and B).
The Agency is currently working with the U.S. Fish and Wildlife Service and the National
Marine Fisheries Service (collectively referred to as, "the Services") to develop methodologies
for conducting national threatened and endangered (listed) species assessments for pesticides in
accordance with the Endangered Species Act (ESA)  7. Therefore, although EPA has not yet
fully evaluated risks to federally listed species, the Agency will complete its listed species
assessment and any necessary consultation with the Services for dithiopyr prior to completing
the dithiopyr registration review. Likewise, the Agency will complete endocrine screening for
dithiopyr, pursuant to the Federal Food, Drug, and Cosmetic Act (FFDCA)  408(p), before
completing registration review. See Appendices C and D, respectively, for additional information
on the listed species assessment and the endocrine screening for the dithiopyr registration
review.
3

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Dithiopyr is a pyridine-based class 3 herbicide according to the Weed Science Society of
America (WSSA),1 with selective toxicity to broadleaf weeds. While most herbicides in the
pyridine group are in class 4 and work as synthetic auxins (plant hormones), dithiopyr works by
inhiting microtuble assembly. It is registered for use on the following sites: residential,
recreational, and commercial turf (including sod farms), landscape, field grown, and container-
grown ornamentals, Christmas trees, rights of ways, and non-crop areas such as
fencerows/hedgerows and airports/landing fields. Dithiopyr products are formulated as an
emulsifiable concentrate, flowable concentrate, granule, ready-to-use liquid, soluble concentrate,
or wettable powder. Dithiopyr is applied via backpack sprayer, foam applicator, granule
applicator, handgun, ground sprayers, and spreader.
This document is organized in five sections: the Introduction, which includes this summary and a
summary of public comments and EPA's responses; Use and Usage, which describes how and
why dithiopyr is used and summarizes data on its use; Scientific Assessments, which summarizes
EPA's risk and benefits assessments, updates or revisions to previous risk assessments, and
provides broader context with a discussion of risk characterization; the Interim Registration
Review Decision, which describes the mitigation measures necessary to address risks of concern
and the regulatory rationale for EPA's ID; and, lastly, the Next Steps and Timeline for
completion of this registration review.
A. Summary of Dithiopyr Registration Review
Pursuant to 40 CFR  155.50, EPA formally initiated registration review for dithiopyr with the
opening of the registration review docket for this case. The following summary highlights the
docket opening and other significant milestones that have occurred thus far during the
registration review of dithiopyr.
	December 2013- The Dithiopyr Preliminary Work Plan (PWPj, Dithiopyr Human Health
Assessment Scoping Document in Support of Registration Review, and the Registration
Review Problem Formulation for Dithiopyr were posted to the docket for a 60-day public
comment period.
	July 2014- The Final Work Plan (FWP) for dithiopyr was issued. Comments were
received from dozens of lawn care operators, vegetation management specialists, and
university extension specialists attesting to the benefits of dithiopyr use. Comments
were also received from the FIFRA Endangered Species Task Force (FESTF) with
respect to data compensation for FESTF data. The Center for Biological Diversity
(CBD) submitted comments on EPA's obligations under ESA. The comments did not
result in changes to the data needs or the registration review timeline presented in the
FWP.
'Wccdscicncc.org. 2013. http://www.weedscience.ore/summarv/Herbicide.aspx. Date Accessed. June 6, 2013 or
WSSA link. https://wssa.net/wp-content/nploads/WSSA-Herbicide-SOA-2(	t
4

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
	November 2014- A Generic Data Call-in (GDCI-128994-1426) for dithiopyr was issued
for data needed to conduct the registration review risk assessments. All data
requirements have been satisfied, except the non-guideline (OECD 237) honey bee
larvae acute oral toxicity study.
	August 2018- The Agency announced the availability of Dithiopyr: Human Health
Draft Risk Assessment for Registration Review and the Dithiopyr: Preliminary
Ecological Risk Assessment for Registration Review to the dithiopyr docket for a 60-day
public comment period. Two comments were received during the comment period from
Corteva AgriScience (formerly Dow AgroSciences), the technical registrant, and the
U.S. Department of Agriculture. These comments did not directly result in changes to
the risk assessments. However, thyroid weight of evidence and benchmark dose
information submitted in January 2020 resulted in revisions to the human health risk
assessment. The ecological risk assessment was also revised to correct a unit
conversion error for aquatic invertebrates.
	June 2020- The Agency announced the availability of the Proposed Interim Registration
Review Decision (PID) in the docket for dithiopyr, for a 60-day public comment period
which opened on September 2, 2020 and closed on November 2, 2020. Along with the
PID, the following documents were also posted to the dithiopyr docket:
o Dithiopyr: Revised Human Health Risk Assessment for Registration Review,
dated May 29, 2020.
o Dithiopyr: Revised Draft Ecological Risk Assessment for Registration Review,
dated May 28, 2020.
o Dithiopyr: Response to Comments and Transmittal of Data Evaluation Recordfor
Non-guideline Groundwater Monitoring Study, dated March 30, 2020.
o Response to Public Comments on the Preliminary Ecological Risk Assessment
for Dithiopyr, dated August 6, 2019.
o Dithiopyr: Response to Comments from the United States Department of
Agriculture on the Preliminary Ecological Risk Assessment for Registration
Review, dated June 16, 2020.
o Response to Public Comments on the Draft Human Health Risk Assessment for
Dithiopyr, dated May 29, 2020.
o Dithiopyr Use, Usage, Benefits and Impacts of Potential Mitigations, dated
June 17, 2020.
	December 2020 - The Agency has completed the dithiopyr ID and will post it in the
dithiopyr registration review docket (EPA-HQ-OPP-2013-0750).
B. Summary of Public Comments on the Proposed Interim Decision and Responses
During the 60-day public comment period for dithiopyr PID, which opened on September 2,
2020 and closed on November 2, 2020, the Agency received six public comments. Comments
were received from the United States Department of Agriculture (USDA), Harrell's, LLC,
5

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
SiteOne Landscape Supply, the Scotts Company, LLC, the National Association of Landscape
Professionals (NALP) and an anonymous commenter. Substantive public comments are
summarized below, along with the Agency's responses. The Agency thanks all commenters and
has considered all comments in the development of this ID.
Comments submitted by the United States Department of Agriculture (EPA-HQ-OPP-
2013-0750-0077)
Comment: USDA provided some general information on the use and benefits of dithiopyr.
USD A generally supported proposed language in the dithiopyr PID that address spray drift
mitigation, environmental hazards for pollinators, surface and groundwater advisories, and
herbicide resistance management measures.
USDA noted that in the PID, the Agency asked for stakeholder feedback and information on
dithiopyr's behavior in vegetative matter and potential persistence in compost. USDA also noted
that the Agency implied that dithiopyr poses risks in recycled organic products (i.e., compost,
mulch, or manure) because it is in the pyridine class of herbicides. USDA was concerned with
the Agency's assumption since there have been no compost incidents of record and no evidence
to suggest that dithiopyr might be persistent in such materials. USDA noted there are current
dithiopyr product labels (e.g., EPA Reg. No. 62719-542) that already contain use restrictions for
treated plant materials: "Do not use clippings from treated turf for mulching around vegetables or
fruit trees."
USDA compiled comments from representatives in the professional landscape industry and weed
scientists and none of the experts interviewed had heard of a single case where dithiopyr had
been implicated as contaminant of green manure and other recycled plant materials. USDA
suggested that there is no realistic risk of dithiopyr contaminating recycled organic materials
based on its use pattern and current turf management best practices and urged the Agency to
reflect this on product labels until there is reliable evidence for a plausible exposure pathway of
concern.
USDA also commented on the proposed environmental hazard language for pollinators which
refers to indirect risks to pollinators from the use of herbicides. USDA urged the Agency to
consider whether such language is warranted for herbicides such as dithiopyr that have relatively
small ranges of activity on weeds that are not generally pollinator attractive and given dithiopyr's
specific use pattern and minimal risks to pollinators.
EPA Response: The Agency appreciates the information provided by USDA concerning the
benefits of dithiopyr as well as additional stakeholder feedback on the compost issue. Dithiopyr's
behavior in vegetative matter and potential persistence in compost is still an uncertainty. While
synthetic auxin herbicides (WSSA class 4) such as aminocyclopyrachlor, aminopyralid,
clopyralid, and picloram have reported compost incidents, it is unknown if this issue may affect
herbicides with other modes of action. The Agency is working to develop a method to screen
herbicides for potential compost contamination concerns. The Agency did not propose compost
labeling for dithiopyr and is not requiring any compost labeling as part of this ID. USDA's
concern focuses on the fact that EPA merely considered the compost issue in relation to
6

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
dithiopyr. The Agency reserves the right to consider and assess potential effects to non-target
plants in relation to any pesticide.
The Agency is retaining the nontarget organism advisory (which USDA refers to as the
environmental hazard for pollinators), as this statement is added for all pesticides that are toxic to
plants. As an herbicide, dithiopyr may impact pollinator forage and habitat through spray drift.
There are use sites that may contain pollinator forage: ornamentals, rights of ways, and
residential/industrial turf.
Comments Submitted by Harrell's, LLC (EPA-HQ-OPP-2013-0750-008Q) and SiteOne
Landscape Supply (EPA-HO-QPP-2013-0750-0078)
Comment: Harrell's, LLC, a manufacturer and distributor of fertilizer and turf pesticide
products noted the importance of dithiopyr as a preemergent herbicide in the turf and ornamental
market. Dithiopyr has low odor, is non-staining, and provides effective control of crabgrass.
Harrell's further noted that the Agency's PID sought public comment on the potential for
dithiopyr residues to be present in compost source materials, including green waste composed of
grass clippings. Harrell's is not aware of any concerns related to residues of dithiopyr in green
waste. Harrell's suggested that placing restrictions on grass clippings from dithiopyr treated turf
would be costly and place an undue burden on homeowners living in communities that require
collection of grass clippings. Harrell's noted that any decision to manage grass clippings from
turf treated with dithiopyr should be based on science with conclusive evidence of persistence in
compost. Harrell's stated that premature restrictions would place an unnecessary and costly
burden on turf managers and consumers and on the entire composting industry.
SiteOne Landscape Supply supported the continued availability of dithiopyr as an herbicide in
the turf and ornamental markets. SiteOne noted the benefits and importance of dithiopyr in the
lawn care sector for selective control of weeds and as an additional herbicide tool for users in a
weed resistance management program. SiteOne noted it was not aware of any concerns for
residues of dithiopyr in compost materials and encouraged the Agency not to add compost
restrictions.
EPA Response: The Agency appreciates the concerns about potential compost restrictions and
the benefits information provided by Harrell's and OneSite and has considered these comments
in the development of this ID. As noted previously, the Agency did not propose any compost
restriction labeling for dithiopyr in the PID nor is compost labeling being added as part of this
ID.
Comments submitted by the Scotts Company, LLC (EPA-HQ-OPP-2013-0750-0076)
Comment: The Scotts Company sought clarification on the necessary labeling for residential
consumer products. The Scott's Company noted that the mode of action and other resistance
management information is not applicable to residential consumer products.
EPA Response: The Agency agrees with the Scotts Company that mode of action information
and other resistance management labeling is not necessary for residential consumer products.
7

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
The Agency appreciates the information provided and has added clarification to the Appendix B
label table.
Comment Submitted by National Association of Landscape Professionals (NALP) (EPA-
HO-QPP-2013-0750-0082)
Comment: The National Association of Landscape Professionals noted the importance of
dithiopyr to the lawn care and landscaping industry. NALP stated their appreciation of the
agency's efforts to understand the lawn care industry's use pattern and application methods.
Herbicides such as dithiopyr allow landscape professionals to maintain their customer's
properties in a manner that maximizes environmental benefits while using the least amount of
pesticide inputs possible. NALP also provided some general information on the use and benefits
of dithiopyr, as well as how dithiopyr is typically applied by lawn and landscape professionals.
NALP supported the adoption and implementation of turfgrass best management practices that
guide practitioners to reduce the amount of pesticides that are used on turf. NALP also noted
that professional landscapers do not use grass clippings as mulch. NALP stated that the retention
of grass clippings created during the mowing process is encouraged because it recycles nutrients.
In addition, customers dislike it when mowers deposit clippings in plant beds because the
clippings are unattractive, straw colored, and odiferous.
EPA Response: EPA thanks NALP for its comments on the dithiopyr PID. The agency agrees
that the education of applicators and land managers on turf best management practices are
important.
II. USE AND USAGE
Products containing dithiopyr are registered to control grasses and broadleaf weeds on landscape,
field, and container grown ornamentals, including Christmas trees, located in ornamental
gardens, parks, golf courses, and residential areas; on turf sites (residential and institutional
lawns, athletic fields, commercial sod farms, and golf course turf); and uncultivated
nonagricultural areas including roadsides, utility rights-of-way, railways, and industrial areas.
There are no food or feed uses for dithiopyr. Dithiopyr's mode of action is to inhibit the
formation and function of microtubulin resulting in the disruption of normal cell division of
susceptible plants [classified as a group 3 herbicide by the WSSA], Affected plants do not grow
and develop through their normal cycle of vegetative growth followed by reproduction
(flowering and seed setting) and roots are stunted and fail to function.
Registered formulations of dithiopyr include emulsifiable, flowable, and soluble concentrates,
dry flowable, wettable powder, granular, and ready-to-use products, as well as impregnated
mulches. Products are applied via groundboom sprayer, drop or rotary spreader, and manually or
mechanically pressurized hand sprayer equipment. No products are applied via chemigation
applications; chemigation applications are prohibited on some, but not all registrations. Aerial
applications are not prohibited on labels, but there are no specific label directions on how to
apply dithiopyr products using aerial application equipment. It is expected that ground
8

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
applications would be the most likely method of application given typical practices and the
nature of the use sites.
Dithiopyr is used primarily in the professional turf and ornamental markets as a pre-emergence
herbicide, but can be used for post-emergence control of some weeds as well. Usage data are
available for the following categories: lawn herbicides (i.e., those applied by homeowners),
institutional turf facilities, golf courses, lawn care operators, turf farms, and roadway rights-of-
ways. Usage data suggests that most usage of dithiopyr is by lawn care operators who maintain
turf through application of fertilizers and pesticides in residential, commercial, and industrial
areas. In 2013, 609,000 pounds of dithiopyr were applied by lawn care operators2 on a national
level to residential, commercial, and industrial lawns. In 2016, consumers applied about 48,000
pounds of dithiopyr to residential lawns3. The second largest use category is use on golf course
turf. Data from 2013 shows 117,000 lbs of dithiopyr were applied on golf courses2 on a national
level. Additionally, dithiopyr was used on institutional turf facilities, with about 69,000 pounds
dithiopyr used in 20131 on a national level. Usage of dithiopyr was minimal on roadway rights of
ways.4
For additional information on the use and usage of dithiopyr, see the document entitled Dithiopyr
Use, Usage, Benefits and Impacts of Potential Mitigations, which is available in the public
docket.
III. SCIENTIFIC ASSESSMENTS
A. Human Health Risks
A summary of the Agency's human health risk assessment is presented below. The Agency used
the most current science policies and risk assessment methodologies to prepare a risk assessment
in support of the registration review of dithiopyr. For additional details on the human health
assessment, see the Dithiopyr: Human Health Draft Risk Assessment for Registration Review and
the Dithiopyr: Revised Human Health Draft Risk Assessment for Registration Review which are
available in the public docket.
The 2018 Dithiopyr: Human Health Draft Risk Assessment for Registration Review applied a
10X database uncertainty factor (UF) for lack of a comparative thyroid assay (CTA). Risks of
concern were identified in the 2018 assessment for chronic dietary exposure, residential post-
application exposure, and occupational handler exposure. Since the 2018 risk assessment, new
information allowed the Agency to refine its risk assessment and reduce the UF to IX.
2	Kline and Company. 2014. Professional Turf and Ornamental Markets for Pesticides and Fertilizers 2013: U.S.
Market Analysis and Opportunities. [Accessed February 2020.]
3	Non-Agricultural Market Research Proprietary Data. 2017a. Studies conducted and sold by a consulting and
research firm. Report on Consumer Markets for Pesticides and Fertilizers. [Accessed February 2020.]
4	Non-Agricultural Market Research Proprietary Data. 2017b. Studies conducted and sold by a consulting and
research firm. Report on Industrial Vegetation Management of Pesticides. [Accessed April 2020.]
9

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
The revised human health draft risk assessment was updated to reflect these changes. Therefore,
there are no risks of concern for dietary, residential post-application, aggregate, or occupational
handler exposures.
1. Risk Summary and Characterization
An acute dietary risk assessment was not needed because no endpoint attributable to a single
exposure was observed for dithiopyr and, as a result, potential acute dietary risks are not
expected.
A chronic dietary risk assessment was conducted. The 2018 human health risk assessment noted
that chronic dietary risk estimates were above the Agency's LOC. The chronic dietary risk
estimates were equal to 680% of the cPAD for the general U.S. population and equal to 1,700%
of the cPAD for all infants < 1 year old (where risk estimates above 100% are of concern).
Infants <1 year old was the population subgroup with the highest exposure. The Agency
assessed the maximum application parameters on dithiopyr labels (3 applications at 0.5 lb ai/A
and 90-day retreatment interval).
Since the issuance of the 2018 human health risk assessment, a revised human health risk
assessment was completed in 2020 to reflect the decision to reduce the database UF from 10X to
IX and reflect new benchmark dose (BMD) information to further inform the dietary risk
assessment. When the database UF is reduced to IX, the revised dietary risk estimates are not of
concern for all population subgroups, except for the most at risk population subgroup, all infants

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
ai/A, with 90-day retreatment interval). Some labels note different application parameters than
those modeled (e.g., 6 applications, 5 week retreatment interval, with a maximum yearly
application rate of 1.5 lb ai/A/year). However, variations in the frequency of applications or the
interval between applications is not expected to change the dietary risk conclusion as long as the
maximum yearly application rate remains at 1.5 lb ai/A/year.
Residential Handler Risks
For residential handlers, dermal exposure was not assessed since no dermal hazard was
identified. Inhalation exposure was assessed and all scenarios yielded inhalation margins of
exposure (MOEs) that were not of concern. The MOEs range from 67,000 to 19,000,000. The
original LOC was 1,000 in the 2018 human health risk assessment, the revised 2020 risk
assessment reflects a revised LOC of 100. However, the risk conclusions have not changed.
Residential Post-Application Risks
Residential post-application dermal exposure was not assessed since no dermal hazard was
identified. Post-application incidental oral exposure was assessed for applications to lawns and
turf from both liquid and granular formulations. The 2018 human health risk assessment
identified post-application risks to children 1 to 2 years old from hand-to-mouth exposure from
treated lawns/turf. Residential post-application MOEs for children (aged 1 to <2 years old)
ranged from 610 to 300,000. The lowest MOE of 610 was potentially of concern (the LOC was
1,000). The 2020 risk assessment was updated to reflect a change in the database UF from 10X
to IX, and the LOC changed from 1,000 to 100. With the change in the LOC, residential post-
application risk estimates are no longer of concern.
Aggregate Risks
Aggregate risk combines risks from food, drinking water, and residential exposure. In the 2018
risk assessment, an acute aggregate assessment was not required because no endpoint attributable
to a single exposure was identified. A short-term aggregate risk assessment was not performed
because risks of concern were identified for all drinking water exposure scenarios. The 2018
chronic aggregate risk assessment considers exposures to dithiopyr from drinking water only,
and was equal to the chronic dietary risk estimates, which were of concern.
Since 2018, the acute aggregate assessment remains unchanged and is still not required due to
lack of an appropriate endpoint for this scenario. The revised 2020 human health risk assessment
reflects a new short-term aggregate assessment for both adults and children. The short-term
combined (drinking water and residential exposures) assessment results in MOEs of 2,000 and
430 for adults and children, respectively, and are not of concern (LOC=100).
Since revised chronic aggregate risk estimates are equal to the revised chronic dietary risk
estimates, chronic aggregate risks are no longer of concern based on the characterization
provided earlier.
11

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Non-Occupational Spray Drift Risks
Off-target movement of pesticides can occur via spray drift. Spray drift can deposit on surfaces
where contact with residues can eventually lead to indirect exposures (e.g., children playing on
lawns where residues have deposited next to treated fields). In the 2018 assessment, a spray drift
assessment was conducted assuming the highest labeled application rate (0.5 lb ai/A). Incidental
oral risk estimates were calculated for children 1-2 years old, the highest exposed population
subgroup. Risk estimates were not of concern at the field edge for aerial, airblast, and
groundboom applications. MOEs ranged from 2,600 to 4,600, where the original LOC from the
2018 risk assessment is 1,000.
The revised 2020 human health risk assessment has been updated to reflect a change in the LOC
from 1,000 to 100. In the revised 2020 assessment, spray drift exposure and risk were not
quantified because direct risk estimates for residential and turf exposures are considered
protective of this scenario for both adults and children. MOEs from the turf residential post-
application assessment were not of concern; therefore, there are no non-occupational spray drift
risks of concern.
Cumulative Risks
The Agency has not made a common mechanism of toxicity finding as to dithiopyr and any other
substances and dithiopyr does not appear to produce a toxic metabolite produced by other
substances. Therefore, the Agency has not assumed that dithiopyr has a common mechanism of
toxicity with other substances for this assessment.
Occupational Handler Risks
Occupational handlers are individuals involved in the pesticide application process. A
quantitative dermal risk assessment was not required since there is no dermal hazard for
dithiopyr. Only inhalation risks were assessed. The 2018 risk assessment identified occupational
handler risks of concern for the following scenario: mixing/loading water soluble packets for
aerial application, where the MOE is 880 (where MOEs below the LOC of 1,000 are of concern).
The revised 2020 human health risk assessment reflects a change in the LOC from 1,000 to 100.
With the revised LOC of 100, all scenarios yielded MOEs that do not represent risks of concern.
The occupational handler MOEs range from 880 to 2.7 million.
Occupational Post-Application Risks
Occupational post-application dermal exposure was not assessed for dithiopyr because there is
no dermal hazard identified. Technical dithiopyr is classified as being in Toxicity Category IV
via the dermal route and Toxicity Category IV for skin irritation potential. Chemicals in these
categories are assigned a 12-hour restricted entry interval (REI). The current REI on the labels is
12 hours and is adequate to protect agricultural workers from post-application exposure to
dithiopyr.
12

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
2.	Human Incidents and Epidemiology
A search for human incidents was conducted in 2018 in preparation for risk assessment. From
January 1, 2013 to March 1, 2018, there were two incidents (classified as moderate severity)
reported for dithiopyr alone in the main Incident Data System (IDS). There were four
additional incidents involving pesticide products containing dithiopyr co-formulated with
another pesticide. A search was conducted in aggregate IDS. From January 1, 2012 to April 28,
2017, there were a total of 36 incidents reported involving dithiopyr. Thirty-three of these
incidents were classified as minor severity and three had no or unknown severity.
A query of the Center for Disease Control's National Institute for Occupational Health
(CDC/NIOSH) SENSOR-Pesticides database, identified a total of 25 cases involving dithiopyr
from 1998 to 2014. Seven cases involved a single active ingredient and eighteen cases involved
multiple pesticides. Fifteen cases occurred in occupational settings and ten cases were
residential. Six cases were moderate in severity and 19 cases were low in severity.
Based on the low frequency and severity of incident cases reported for dithiopyr, in both the
Main and Aggregate IDS and SENSOR-Pesticides, there does not appear to be a concern at this
time that would warrant further investigation. The Agency will continue to monitor the incident
information and if a concern is triggered, additional analysis will be conducted.
3.	Tolerances
Dithiopyr is not registered for use on food or feed crops; therefore, there are no tolerances
established.
4.	Human Health Data Needs
A guideline 875.1000 turf transferable residue study for dithiopyr was previously identified as a
data gap. However, since no risks of concern resulted from the existing turf uses, the Agency
does not anticipate requiring this study to support registration review.
B. Ecological Risks
A summary of the Agency's ecological risk assessment is presented below. The Agency used the
most current science policies and risk assessment methodologies to prepare a risk assessment in
support of the registration review of dithiopyr. For additional details on the ecological
assessment for dithiopyr, see the May 28, 2020 document, Dithiopyr: Revised Draft Ecological
Risk Assessment for Registration Review, which is available in the public docket.
EPA is currently working with its federal partners and other stakeholders to implement an
interim approach for assessing potential risk to listed species and their designated critical
habitats. Once the scientific methods necessary to complete risk assessments for listed species
and their designated critical habitats are finalized, the Agency will complete its endangered
13

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
species assessment for dithiopyr. See Appendix C for more details. As such, potential risks for
non-listed species only are described below.
1. Risk Summary and Characterization
Terrestrial Risks
Mammals
Risk quotients (RQs) for mammals are not of concern on an acute exposure basis. Chronic RQs
were calculated assuming upper-bound estimates of residues in food items, and the maximum
application parameters: three applications of dithiopyr at 0.5 lb ai/A, with a 90-day interval
between applications. Dose-based chronic RQs exceed the level of concern (LOC) of 1 and
ranged from 0.2-36.9 for all uses. Chronic dietary-based RQs also exceed the LOC of 1 and
ranged from 0.4 to 5.8 for all uses. Dietary-based RQs directly compare the pesticide
concentration consumed by the animal in the diet to the estimated concentration on food items.
The dose-based RQs account for the fact that small animals need to consume more food relative
to their body weight than large animals and that differential amounts of food are consumed
depending on the water content and nutritional value of food.
The Agency refined the mammalian exposure assessment by considering mean estimates of
residue levels in food items (e.g., mean Kenaga estimates). RQs are lower when using mean
Kenaga estimates. Dose-based RQs (0.1-11) and dietary-based RQs (0.1-1.7) based on mean
Kenaga estimates still exceed the chronic LOC of 1.
Since one of the formulations of dithiopyr is granular, the Agency estimated chronic risk to
mammals consuming granules. Risk estimates based on consuming granules takes into account
the number of granules that must be consumed to achieve the no observable adverse effect
concentration (NOAEC). The Agency determined that a small mammal would need to consume
between 110,000 small granules and 2,000 large granules to reach the toxicity threshold. These
numbers are >100% of the daily diet of an animal that eats seeds as the main part of its diet,
therefore risks from consumption of granules is estimated to be low.
Distances where risk extends from the edge of the field were calculated by considering spray
drift exposures. If applications at the maximum single application rate, 0.5 lb ai/A, are made via
high boom ground spray with very fine to fine droplets, risks to mammals extend 95 feet from
the edge of the treated field. If applications at the same rate are made via high boom and fine to
medium coarse droplets, risks would extend 20 feet from the edge of the field.
A bioaccumulation analysis for mammals consuming fish contaminated with dithiopyr did not
identify risks of concern for most scenarios, except for large river otters which slightly exceed
the LOC of 1(RQ=1.1).
Birds. Reptiles, and Terrestrial-Phase Amphibians
The Agency has not identified acute or chronic risks of concern for birds, reptiles, or
14

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
terrestrial-phase amphibians exposed to dithiopyr. Therefore, there are no risks of
concern.
Terrestrial Invertebrates (honeybees)
No potential acute risks of concern to adult bees from acute contact or oral exposure were
identified (acute contact RQ for adults=0.02; LOC is 0.4). Overall, there are uncertainties for
acute risk to honeybee larvae and chronic honeybee risk due to the absence of the majority of the
Tier 1 bee toxicity data.
Additional data may be necessary to fully evaluate risks to non-target terrestrial invertebrates,
especially pollinators. Although EPA identified the need for certain data to evaluate potential
effects to pollinators when initially scoping the registration review for dithiopyr, the problem
formulation and registration review GDCI for dithiopyr were both issued prior to the EPA's
issuance of the June 2014 Guidance for Assessing Pesticide Risks to Bees5. This 2014 guidance
lists additional pollinator studies that were not included in the dithiopyr registration review DCI.
Therefore, EPA is currently determining whether additional pollinator data are needed for
dithiopyr. If the Agency determines that additional pollinator exposure and effects data are
necessary for dithiopyr, then EPA will issue a DCI to obtain these data. The pollinator studies
that could be required are listed in Table 1 below.
Table 1: Potential Pollinator Data Requirements
()( Sl>l (iiiiilclinc #
Study Doseriplion
Tier 1*
850.3020
Acute contact toxicity study with adult honey bees
850.3030
Honey bee toxicity of residues on foliage
Non-Guideline (OECD 213)
Honey bee adult acute oral toxicity
Non-Guideline (OECD 237)
Honey bee larvae acute oral toxicity
Non-Guideline (OECD 245)
Honey bee adult chronic oral toxicity
Non-Guideline (OECD 239)
Honey bee larvae chronic oral toxicity
Tier 2*
Non-Guideline
Field trial of residues in pollen and nectar
Non-Guideline (OECD 75)
Semi-field testing for pollinators
Tier 3*
850.3040
Full-Field testing for pollinators
' The need for higher tier tests for bees will be determined based upon the results of lower tiered tests and/or other
lines of evidence and the need for a refined pollinator risk assessment.
*The following bee studies have been submitted and are acceptable: guideline 850.3020 honeybee adult acute
contact toxicity and non-guideline honeybee adult acute oral toxicity. Guideline 850.3030 honeybee toxicity of
residues on foliage is not needed because the tier I adult acute contact RQs were not of concern.
5 Available at https://www.epa.gov/sites/production/files/20.1.4-
06/docnments/pottinator risk assessment guidance 06 .1.9 14.pdf
15

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Terrestrial and Wetland Plants
The Agency has identified potential risks to non-target terrestrial plants from the use of
dithiopyr, as expected for an herbicide. Runoff and spray drift RQs ranged from 0.4 to 21.3 for
liquid foliar applications (where the LOC=l). Spray drift only RQs ranged from 0.2 to 1.9. For
granule applications, RQs ranged from 0.2 to 19.4 and exceeded the LOC of 1.
The distance from the edge of the field to reach below the toxicity threshold was calculated using
spray drift modeling. Distances from the edge of the field vary depending on the droplet size and
release height. For ground application at high boom (4 ft release height) using very fine to fine
droplets, the distance to below the toxicity threshold reaches up to 407 ft. With low boom (2 ft
release height) and fine to medium/coarse droplets, the distance to below the toxicity threshold is
up to 82 ft.
Aquatic Risks
Fish and Aquatic-Phase Amphibians
No potential acute or chronic risks of concern for freshwater fish and estuarine/marine fish
exposed to dithiopyr have been identified. Fish are surrogates for aquatic-phase amphibians, and
no risks of concern are expected for this taxon.
Aquatic Invertebrates
Risks to freshwater invertebrates are not of concern.
No acute risks of concern were identified for saltwater invertebrates. Chronic RQs exceed the
LOC slightly for saltwater invertebrates for nursery and rights-of-way use, RQs are 1.1 and 1.3
respectively (where the LOC is 1).
Benthic invertebrates are those residing at the bottom of water bodies or in the sediment. No
acute risks of concern were identified for freshwater benthic invertebrates exposed to dithiopyr.
Chronic risk RQs for freshwater benthic invertebrates from nurseries and rights-of-way use
slightly exceeded the chronic LOC of 1.0, RQs ranged from <0.01 to 1.29.
In the 2018 ecological risk assessment, risks to saltwater benthic invertebrates were identified.
However, an error in the endpoint used for risk calculation was found and the Agency has
recalculated saltwater benthic invertebrate RQs. Acute RQs for saltwater benthic invertebrates
ranged from 0.3 to 0.7 and slightly exceed the acute LOC of 0.5. Chronic RQs for saltwater
benthic invertebrates were not of concern. Revised RQs are posted in the docket in the
Dithiopyr: Revised Draft Ecological Risk Assessment for Registration Review.
Aquatic Plants
The Agency has identified risk to aquatic vascular plants. RQs ranged from 0.4 to 3.1 exceeding
the LOC of 1.0 for most uses. No potential risks of concern were identified for aquatic non-
vascular plants.
16

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
2.	Ecological Incidents
A search of the Incident Data System (IDS) was conducted on March 8, 2018 in support of the
risk assessment. Incidents are categorized according to the likelihood that use of dithiopyr was
associated the incident, and the classification categories are: unrelated, unlikely, possible (i.e.,
the pesticide possibly could have caused the incident but there are other possible explanations),
probable (i.e., circumstances indicate that the pesticide was the cause, but confirming evidence is
lacking), and highly probable (i.e., pesticide was confirmed as the cause through reliable
evidence). From the time at which the Agency began requesting incident reports until March 8,
2018, when a search was conducted, 32 non-target plant incidents have been reported; two were
classified as "possible" and 30 incidents were classified as "probable". One of the incidents was
considered a registered use at the time of the incident, two involved accidental misuses, and the
legality of use was undetermined in 28 incidents. Two of the incidents involved additional
pesticides mixed with dithiopyr. Overall, most reported incidents are from use on golf course turf
and involve damage to grass. The aggregate incident database for dithiopyr contains 38 incidents
(7 minor fish and wildlife and 31 minor plant incidents), but no additional information is
available for those incidents.
The Agency will continue to monitor ecological incident information as it is reported to the
Agency. A detailed analysis of these incidents will be conducted if reported information
indicates concerns for risk to non-target organisms.
3.	Ecological and Environmental Fate Data Needs
The Agency issued a generic data call-in notice (GDCI-128994-1426) in December 2014. The
environmental fate and ecological effects data requirements have been satisfied, except for the
non-guideline larval honeybee acute oral toxicity study, which is considered outstanding. The
Agency did not call-in the entire suite of bee studies in the GDCI, therefore, the Agency is
evaluating the need for additional bee studies. No other data requirements are anticipated for
registration review at this time.
C. Benefits
Dithiopyr is predominantly used in golf courses and in the professional turf management sector
(e.g., lawn care). Dithiopyr can be used to treat a variety of problematic weed species such as
crabgrass, barnyardgrass, goosegrass, foxtails, carpetweed, chickweed, henbit, prostrate
knotweed, and redroot pigweed.
In golf course settings, dithiopyr is applied to fairways, roughs, tee boxes, and putting greens.
Major weeds targeted are crabgrass, spurge, oxalis, and bluegrass. Dithiopyr provides niche
benefits for post-emergent crabgrass control in warm-season turf grass. It provides effective
control on crabgrass up to the 5-leaf stage, which is the leading weed species in golf courses.
Dithiopyr also provides benefits in the lawn care sector for selective control of weeds. In lawn
care, it is used for both pre- and post-emergence control of crabgrass in established lawns and
ornamental turf. Similar to golf course settings, crabgrass is the leading weed targeted by lawn
care operators.
17

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
There are other herbicides used in turfgrass for both pre- and post-emergence weed control, such
as ethofumesate, indaziflam, mesotrione, pronamide, and sulfentrazone. Dithiopyr provides an
additional tool for users in a weed resistance management program.
Additional information on benefits is available in the Dithiopyr Use, Usage, Benefits and
Impacts of Potential Mitigations, available in the docket (EPA-HQ-OPP-2013-0750).
IV. INTERIM REGISTRATION REVIEW DECISION
A. Risk Mitigation and Regulatory Rationale
The Agency has determined that there are no human health risks of concern for dithiopyr. The
Agency is requiring updated labeling for products packaged in water soluble bags to meet current
standards. As discussed in Section III of this document, potential risks of concern were identified
primarily to mammals, as well as aquatic and terrestrial plants. Slight RQ exceedances were also
noted for aquatic invertebrates. Risk to non-target organisms may be outweighed by the niche
benefits of dithiopyr use in turf management. To address the potential ecological risks, the
Agency is requiring mandatory spray drift management language and updated environmental
hazards and water advisories. In discussions with the Agency on May 20, 2020 the technical
registrant, Corteva AgriScience, agreed to the risk mitigation measures with minor editorial
comments. The labeling changes for dithiopyr are not likely to adversely impact stakeholders.
All mitigation measures are detailed in Appendices A and B.
1.	Updated Labeling for Water Soluble Packages
Dithiopyr is formulated in water soluble packages (WSP). The Agency has recently updated
labeling instructions for products formulated in water soluble packaging to meet current labeling
standards. This language includes updated mixing instructions, updated handling instructions,
and updated engineering controls statement. Details of these label changes are set forth in
Appendix B.
2.	Enforceable Spray Drift Management
The Agency is requiring enforceable spray drift mitigation language be included on all dithiopyr
product labels for products applied by liquid spray application to reduce off-target spray drift and
establish a baseline level of protection against spray drift that is consistent across all dithiopyr
products. Reducing spray drift through a number of labeling elements, including droplet size,
release height, and wind speed restriction for groundboom will reduce the extent of dithiopyr
environmental exposure and risk to non-target plants and animals. Although the Agency is not
making a complete endangered species finding at this time, these labels label changes are
expected to reduce the extent of exposure and may reduce risk to listed species whose range
and/or critical habitat co-occur with the use of dithiopyr. The spray drift language is intended to
be mandatory, enforceable statements and supersede any existing mandatory language already on
product labels covering the same topics. The mandatory spray drift management measures that
are necessary as determined by the Agency are as follows:
18

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
	Applicators must not spray during temperature inversions.
	For groundboom applications, the applicator must only apply with the release height
recommended by the manufacturer, but no more than 4 feet above the ground or crop
canopy. Boomless ground sprayers (e.g., those for roadside applications) and fixed-height
ground boom sprayers are exempt from the required 4 ft release height since coarser
droplet sizes are likely to be used with these types of equipment.
	Applicators are required to select the nozzle and pressure that deliver a medium or
coarser droplet size (ASABE S572.3).
	Do not apply when wind speeds exceed 15 miles per hour at the application site.
Mandatory wind speed restrictions complicate weed and crop management by reducing the
available time to make applications and make it more likely that a grower may need to alter pest
control plans. However, dithiopyr is primarily used in residential and commercial landscapes
with mixtures of many plant species in the general application area. Areas to be treated tend to be
small and applications must be precise to avoid damage to non-target plants. Therefore, the
impacts of the drift reduction requirements may be minimal to these users because they
correspond to common practice.
The Agency is also requiring standardizing all advisory spray drift language on dithiopyr product
labels. Registrants must ensure that any existing advisory language left on labels does not
contradict or modify the new mandatory spray drift statements noted in this ID, once effective.
For the advisory spray drift language to be incorporated on dithiopyr labels, see Appendix B.
In addition to including the spray drift restrictions on dithiopyr labels, all references to
volumetric mean diameter (VMD) information for spray droplets are to be removed from all
dithiopyr labels where such information currently appears.
3. Environmental Hazards
Non-target Organism Advisory
The Agency is adding a non-target organism advisory. The protection of pollinating organisms is
a priority for the Agency. Risk to pollinators from the use of dithiopyr is uncertain. It is possible
that pollinators may be exposed to dithiopyr from residues in pollen or nectar through spray drift.
Bees may also be exposed to pollen and nectar through uptake into treated plants (e.g.,
ornamentals) or blooming weeds present in residential lawns. This may negatively impact forage
and habitat of pollinators and other non-target organisms. It is the Agency's goal to reduce spray
drift whenever possible and to educate growers on the potential for indirect effects on the forage
and habitat of pollinators and other non-target organisms. Therefore, EPA a non-target organism
advisory language is necessary to be placed on dithiopyr labels to address this potential concern:
"This product is toxic to plants and may adversely impact the forage and habitat of non-target
organisms, including pollinators, in areas adjacent to the treated site. Protect the forage and
habitat of non-target organisms by following label directions intended to minimize spray drift."
19

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Water Advisories
Dithiopyr has fate properties which indicates that it may persist in both surface and groundwater.
Therefore, the Agency has determined that it is necessary to add groundwater and surface water
advisories to warn users of the potential for groundwater/surf ace water contamination. The
water advisories are as follows:
Groundwater Advisory.
"This chemical has properties and characteristics associated with chemicals detected in
groundwater. This chemical may leach into groundwater if used in areas where soils are
permeable, particularly where the water table is shallow."
Surface Water Advisory.
"This product may impact surface water quality due to runoff of rainwater. This is especially true
for poorly draining soils and soils with shallow ground. This product is classified as having a
high potential for reaching a surface water via runoff for several weeks after application."
4. Herbicide Resistance Management
On August 24, 2017, EPA finalized a Pesticide Registration Notice (PRN) on herbicide
resistance management4. Consistent with the Notice, EPA is requiring the implementation of
herbicide resistance measures for existing chemicals during registration review, and for new
chemicals and new uses at the time of registration. In registration review, herbicide resistance
elements will be included in every herbicide ID.
The development and spread of herbicide resistant weeds in agriculture is a widespread problem
that has the potential to fundamentally change production practices in U.S. agriculture. While
herbicide resistant weeds have been known since the 1950s, the number of species and their
geographical extent, has been increasing rapidly. Currently there are over 250 weed species
worldwide with confirmed herbicide resistance. In the United States, there are over 155 weed
species with confirmed resistance to one or more herbicides.
Management of herbicide resistant weeds, both in mitigating established herbicide resistant
weeds and in slowing or preventing the development of new herbicide resistant weeds, is a
complex problem without a simple solution. Coordinated efforts of growers, agricultural
extension, academic researchers, scientific societies, pesticide registrants, and state and federal
agencies are required to address this problem.
EPA is requiring measures for the pesticide registrants to provide growers and users with
detailed information and recommendations to slow the development and spread of herbicide
resistant weeds. This is part of a more holistic, proactive approach recommended by crop
consultants, commodity organizations, professional/scientific societies, researchers, and the
registrants themselves.
20

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
5. Label Clarifications
Some dithiopyr labels do not provide adequate information on application parameters. A number
of products are missing maximum yearly application rates. In discussions with the technical
registrant, Corteva AgriScience, on May 20, 2020, the maximum yearly application rate being
supported is 1.5 lb ai/A for all use sites. The Agency has determined that it is necessary for this
information to be added to existing labels where missing. Labels that may be missing this
information include EPA Reg. Nos. 279-9540, 8660-159, and 83822-1.
B.	Tolerance Actions
Dithiopyr is not registered for use on food crops; therefore, there are no tolerances and no
anticipated tolerance actions for dithiopyr.
C.	Interim Registration Review Decision
In accordance with 40 CFR  155.56 and  155.58, the Agency is issuing this ID. Except for the
Endocrine Disruptor Screening Program (EDSP) and the Endangered Species Act (ESA)
components of this case, the Agency has made the following ID: (1) no additional data are
required at this time; and (2) changes to the affected registrations and their labeling are needed at
this time, as described in Section IV. A and Appendices A and B.
In this ID, the Agency is making no human health or environmental safety findings associated
with the EDSP screening of dithiopyr, nor is it making a complete endangered species finding.
Although the Agency is not making a complete endangered species finding at this time, the risk
mitigation described in this document is expected to reduce the extent of environmental exposure
and may reduce risk to listed species whose range and/or critical habitat co-occur with the use of
dithiopyr. The Agency's final registration review decision for dithiopyr will be dependent upon
the result of the Agency's ESA assessment and any needed  7 consultation with the Services
and an EDSP FFDCA  408(p) determination.
D.	Data Requirements
All data required as part of registration review (GDCI-128994-1426) have been submitted,
except for a non-guideline (OECD 237) honeybee larval acute oral toxicity study. The Agency
will work with the registrant to ensure the submission of this study. No additional data are
anticipated to be needed to be called-in for this registration review at this time. The Agency will
consider requiring submission of additional pollinator data as a separate action.
21

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
V. NEXT STEPS AND TIMELINE
A.	Interim Registration Review Decision
A Federal Register Notice will announce the availability of this ID for dithiopyr. A final decision
on the dithiopyr registration review case will occur after: (1) an EDSP FFDCA  408(p)
determination, and (2) an endangered species determination under the ESA and any needed  7
consultation with the Services.
B.	Implementation of Mitigation Measures
Once the Interim Registration Review Decision is issued, the dithiopyr registrants must submit
amended labels that include the label changes described in Appendices A and B. The revised
labels and requests for amendment of registrations must be submitted to the Agency for review
within 60 days following issuance of the Interim Registration Review Decision in the docket.
Registrants must submit a cover letter, a completed Application for Registration (EPA form
8570-1) and electronic copies of the amended product labels. Two copies for each label must be
submitted, a clean copy and an annotated copy with changes. In order for the application to be
processed, registrants must include the following statement on the Application for Registration
(EPA form 8570-1):
"I certify that this amendment satisfies the requirements of the Dithiopyr Interim Registration
Review Decision and EPA regulations at 40 CFR Section 152.44, and no other changes have
been made to the labeling of this product. I understand that it is a violation of 18 U.S.C. Section
1001 to willfully make any false statement to EPA. I further understand that if this amendment is
found not to satisfy the requirements of the Dithiopyr Interim Registration Review Decision and
40 CFR Section 152.44, this product may be in violation of FIFRA and may be subject to
regulatory and/or enforcement action and penalties under FIFRA."
Within the required timeframe, registrants must submit the required documents to the Re-
evaluation section of EPA's Pesticide Submission Portal (PSP), which can be accessed through
EPA's Central Data Exchange (CDX) using the following link: https://cdx.epa.gov/. Registrants
who wish to send paper copies of amended products labels should contact Veronica Dutch
(dutch.veronica@epa.gov) to make the necessary arrangements for paper delivery.
22

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Appendix A: Summary of Risk Mitigation for Dithiopyr
Registration Review Case#: 7225
PC Code: 128994
Chemical Type: Herbicide
Chemical Family: Pyridine
Mechanism of Action: Inhibition of microtubule assembly
Affected
Population(s)
Source of Exposure
Route of Exposure
Duration of
Exposure
Potential Risk(s)
of Concern
Required Actions
Comment
Mammals
Residues at site of
application, spray
drift
Ingestion
Chronic
Growth
Enforceable spray drift
management measures
Risks are limited to the
site of application and 20
ft from the edge of the
treatment area with
revised spray drift labeling
Aquatic
Invertebrates
Spray Drift
Runoff
Residues in surface
water
Chronic
Survival,
reproduction, and
growth
Enforceable spray drift
management measures

Aquatic Plants
Spray Drift and
Runoff
Foliar absorption
Root uptake
N/A
Growth
Enforceable spray drift
management measures

Non-target
Terrestrial Plants
Spray Drift
Foliar absorption
Root uptake
N/A
Growth
Enforceable spray drift
management measures
Risks extend to 148 ft
from the edge of the
treatment area with
revised spray drift labeling

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Appendix B: Labeling Changes for Dithiopyr Products
Description


Label Language for Dithiopyr Products

Placement on Label
End Use Products
Site of Action Group
Number

Note to registrant:
	Include the name of the ACTIVE INGREDIENT in the first column
	Include the word "GROUP" in the second column
	Include the SITE OF ACTION CODE in the third column (for herbicides this is the Site of Action)
	Include the type of pesticide (/'. e., HERBICIDE) in the fourth column.
Front Panel, upper right
quadrant.
All text should be black,
bold face and all caps
on a white background,
except the mode of
[Applies to all products
except those for
residential consumer
use.]

DITHIOPYR
GROUP
3
HERBICIDE
action code, which
should be white, bold
face and all caps on a
black background; all
text and columns should
be surrounded by a
black rectangle.
HERBICIDE
RESISTANCE
MANAGEMENT:
Weed Resistance
Management
Include resistance management label language for herbicides from PRN 2017-1 and PRN 2017-2
(httDs://\Yww.CDa.aov/DCSticidc-rcaistration/DCSticidc-rcaistration-noticcs-Ycar)
Directions for Use, prior
to directions for specific
crops under the heading
"WEED
RESISTANCE-
MANAGEMENT"
[Applies to all products
except those for
residential consumer
use.]






Non-target Organism
Advisory
"NON-TARGET ORGANISM ADVISORY: This product is toxic to plants and may adversely impact the forage
and habitat of non-target organisms, including pollinators, in areas adjacent to the treated site. Protect the forage and
habitat of non-target organisms by following label directions intended to minimize spray drift. For further guidance
and instructions on how to minimize spray drift, refer to the Spray Drift Management section of this label."
Enviromnental Hazards
Groundwater
Advisory
"This chemical has properties and characteristics associated with chemicals detected in groundwater. This chemical
may leach into groundwater if used in areas where soils are permeable, particularly where the water table is
shallow."
Enviromnental Hazards
Surface Water
Advisory
"This product may impact surface water quality due to runoff of rainwater. This is especially true for poorly
draining soils and soils with shallow ground. This product is classified as having a high potential for reaching
surface water via runoff for several weeks after application."
Enviromnental Hazards
24

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Description
Label Language lor l)ilhiop\r Producls
Placement on Label



Application Rate
Clarification
"Do not apply more than 1.5 lb ai/A of dithiopyr per year." "Maximum single application rate at 0.5 lb a.i./A".
Directions for Use
Additional Required
Labelling Action
[Applies to all products
delivered via liquid
spray applications.]
Remove information about volumetric mean diameter from all labels where such information currently appears.
Directions for Use
Label Language for
pesticide products in
Water- Soluble
Packaging (WSP)
intended to be diluted
directly in a spray
tank prior to
application
Instructions for Introducing Water Soluble Packages Directly into Spray tanks:
"Water Soluble Packages (WSPs) are designed to dissolve in water. Agitation may be used, if necessary, to help
dissolve the WSP. Failure to follow handling and mixing instructions can increase your exposure to the pesticide
products in WSPs. WSPs, when used properly, qualify as a closed mixing/loading system under the Agricultural
Worker Protection Standard [40 CFR 170.607(d)].
Handling Instructions
Follow these steps when handling pesticide products in WSPs.
1.	Mix in spray tank only.
2.	Handle the WSP in a manner that protects package from breakage and/or unintended release of contents.
If package is broken, put on PPE required for clean-up and then continue with mixing instructions.
3.	Keep the WSP in outer packaging until just before use.
4.	Keep the WSP dry prior to adding to the spray tank.
5.	Handle with dry gloves and according to the label instructions for PPE.
6.	Keep the WSP intact. Do not cut or puncture the WSP.
7.	Reseal the WSP outer packaging to protect any unused WSP(s).
Mixing Instructions
Follow the steps below when mixing this product, including if it is tank-mixed with other pesticide products. If being
tank-mixed, the mixing directions 1 through 9 below take precedence over the mixing directions of the other tank
mix products. WSPs may, in some cases, be mixed with other pesticide products so long as the directions for use of
all the pesticide product components do not conflict. Do not tank-mix this product with products that prohibit tank-
mixing or have conflicting mixing directions.
1.	If a basket or strainer is present in the tank hatch, remove prior to adding the WSP to the tank.
2.	Fill tank with water to approximately one-third to one-half of the desired final volume of spray.
Directions for Use
25

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Description
l.ahcl Language lor l)ilhiop\r Producls
Placemen! on l.ahcl

3.	Stop adding water and stop any agitation.
4.	Place intact/unopened WSP into the tank.
5.	Do not spray water from a hose or fill pipe to break or dissolve the WSP.
6.	Start mechanical and recirculation agitation from the bottom of tank without using any overhead
recirculation, if possible. If overhead recirculation cannot be turned off, close the hatch before starting
agitation.
7.	Dissolving the WSP may take up to 5 minutes or longer, depending on water temperature, water hardness
and intensity of agitation.
8.	Stop agitation before tank lid is opened.
9.	Open the lid to the tank, exercising caution to avoid contact with dusts or spray mix, to verify that the WSP
has fully dissolved and the contents have been thoroughly mixed into the solution.
10.	Do not add other allowed products or complete filling the tank until the bags have fully dissolved and
pesticide is thoroughly mixed.
11.	Once the WSP has fully dissolved and any other products have been added to the tank, resume filling the
tank with water to the desired level, close the tank lid, and resume agitation.
12.	Use the spray solution when mixing is complete.
13.	Maintain agitation of the diluted pesticide mix during transport and application.
14.	It is unlawful to use any registered pesticide, including WSPs, in a manner inconsistent with its label.

Engineering Controls
for pesticide products
in WSP intended to be
diluted directly in a
spray tank prior to
application
For Toxicity Category I and II products:
"ENGINEERING CONTROLS STATEMENT
Water soluble packets, when used correctly, qualify as a closed mixing/loading system under the Worker
Protection Standard [40 CFR 170.607(d)]. Mixers and loaders handling this product while it is enclosed in
intact water soluble packets may elect to wear reduced PPE of long-sleeved shirt, long pants, shoes, socks, a
chemical-resistant apron, and chemical-resistant gloves. When reduced PPE is worn because a closed
system is being used, handlers must be provided all PPE specified above for "applicators and other
handlers" and have such PPE immediately available for use in an emergency, such as a spill or equipment
break-down."
For Toxicity Category III and IV products:
"ENGINEERING CONTROLS STATEMENT
Water soluble packets, when used correctly, qualify as a closed mixing/loading system under the Worker
Protection Standard [40 CFR 170.607(d)]. Mixers and loaders handling this product while it is enclosed in
intact water soluble packets may elect to wear reduced PPE of long-sleeved shirt, long pants, shoes, socks.
When reduced PPE is worn because a closed system is being used, handlers must be provided all PPE
specified above for "applicators and other handlers" and have such PPE immediately available for use in an
emergency, such as a spill or equipment break-down."
Precautionary
Statements
under the "Personal
Protective Equipment"
section
26

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Description
l.ahcl Language lor l)ilhiop\r Producls
Placement on l.ahcl
Spray Drift
Management
Application
Restrictions for
products that are
applied as liquids and
allow ground boom
applications
"MANDATORY SPRAY DRIFT MANAGEMENT
Ground Boom ADDlications:
	User must only apply with the release height recommended by the manufacturer, but no more than 4 feet above
the ground or crop canopy.
	Applicators are required to select the nozzle and pressure that deliver a medium or coarser droplet size (ASABE
S572).
	Do not apply when wind speeds exceed 15 miles per hour at the application site.
	Do not apply during temperature inversions."
Directions for Use, in a
box titled "Mandatory
Spray Drift
Management" under the
heading "Ground Boom
Applications"
Spray Drift
Management
Application
Restrictions for
products that are
applied as liquids and
allow boom-less
ground sprayer
applications or fixed
height groundboom
sprayer applications
"MANDATORY SPRAY DRIFT MANAGEMENT
Boomless Ground ADDlications:
	Applicators are required to select the nozzle and pressure that deliver a medium or coarser droplet size (ASABE
S572).
	Do not apply when wind speeds exceed 15 miles per hour at the application site.
	Do not apply during temperature inversions."
Directions for Use, in a
box titled "Mandatory
Spray Drift
Management" under the
heading "Boomless
Ground Applications"
Advisory Spray Drift
Management
Language for all
products delivered via
liquid spray application
"SPRAY DRIFT ADVISORIES
THE APPLICATOR IS RESPONSIBLE FOR AVOIDING OFF-SITE SPRAY DRIFT.
BE AWARE OF NEARBY NON-TARGET SITES AND ENVIRONMENTAL CONDITIONS.
IMPORTANCE OF DROPLET SIZE
An effective way to reduce spray drift is to apply large droplets. Use the largest droplets that provide target pest
control. While applying larger droplets will reduce spray drift, the potential for drift will be greater if applications
are made improperly or under unfavorable environmental conditions.
Controlling Droplet Size - Ground Boom (note to registrants: remove if ground boom is prohibited on product
labels)
	Volume - Increasing the spray volume so that larger droplets are produced will reduce spray drift. Use the highest
practical spray volume for the application. If a greater spray volume is needed, consider using a nozzle with a higher
flow rate.
	Pressure - Use the lowest spray pressure recommended for the nozzle to produce the target spray volume and
droplet size.
	Spray Nozzle - Use a spray nozzle that is designed for the intended application. Consider using nozzles designed to
reduce drift.
Directions for Use, just
below the Spray Drift
box, under the heading
"Spray Drift Advisories"
27

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Description
l.ahel Language Idi- l)ilhiop\r Producls
Placemen! (III l.ilhol
BOOM HEIGHT - Ground Boom (note to registrants: remove if ground boom is prohibited on product labels)
For ground equipment, the boom should remain level with the crop and have minimal bounce.
SHIELDED SPRAYERS
Shielding the boom or individual nozzles can reduce spray drift. Consider using shielded sprayers. Verify that the
shields are not interfering with the uniform deposition of the spray on the target area.
TEMPERATURE AND HUMIDITY
When making applications in hot and dry conditions, use larger droplets to reduce effects of evaporation.
TEMPERATURE INVERSIONS
Drift potential is high during a temperature inversion. Temperature inversions are characterized by increasing
temperature with altitude and are common on nights with limited cloud cover and light to no wind. The presence of
an inversion can be indicated by ground fog or by the movement of smoke from a ground source or an aircraft smoke
generator. Smoke that layers and moves laterally in a concentrated cloud (under low wind conditions) indicates an
inversion, while smoke that moves upward and rapidly dissipates indicates good vertical air mixing. Avoid
applications during temperature inversions.
WIND
Drift potential generally increases with wind speed. AVOID APPLICATIONS DURING GUSTY WIND
CONDITIONS.
Applicators need to be familiar with local wind patterns and terrain that could affect spray drift."	
Advisory Spray Drift
Management
Language for products
that are applied as
liquids and allow
boom-less ground
sprayer applications
"SPRAY DRIFT ADVISORIES
Boomless Ground Applications:
 Setting nozzles at the lowest effective height will help to reduce the potential for spray drift.'
Directions for Use, just
below the Spray Drift
box, under the heading
"Spray Drift Advisories"
Advisory Spray Drift
Management
Language for all
products that allow
liquid applications with
handheld technologies
"SPRAY DRIFT ADVISORIES
Handheld Technology Applications:
 Take precautions to minimize spray drift."
Directions for Use, just
below the Spray Drift
box, under the heading
"Spray Drift Advisories"
28

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Appendix C: Endangered Species Assessment
In 2013, the EPA, along with the Fish and Wildlife Service (FWS), the National Marine
Fisheries Service (NMFS), and the United States Department of Agriculture (USDA) released a
summary of their joint Interim Approaches for assessing risks to endangered and threatened
(listed) species from pesticides6. These Interim Approaches were developed jointly by the
agencies in response to the National Academy of Sciences' (NAS) recommendations that
discussed specific scientific and technical issues related to the development of pesticide risk
assessments conducted on federally threatened and endangered species.
Since that time, EPA has conducted biological evaluations (BEs) on three pilot chemicals
representing the first nationwide pesticide consultations. These initial consultations were pilots
and were envisioned to be the start of an iterative process. The agencies are continuing to work
to improve the consultation process. For example, advancements to the initial pilot interim
methods have been required based on experience conducting the first three pilot BEs. Public
input on those required revisions is currently being considered.
Also, a provision in the December 2018 Farm Bill included the establishment of a FIFRA
Interagency Working Group to provide recommendations for improving the consultation process
required under section 7 of the Endangered Species Act for pesticide registration and
Registration Review and to increase opportunities for stakeholder input. This group includes
representation from EPA, NMFS, FWS, USDA, and the Council on Environmental Quality
(CEQ). Given this new law and that the first nationwide pesticide consultations were envisioned
as pilots, the agencies are continuing to work collaboratively as consistent with the congressional
intent of this new statutory provision. EPA has been tasked with a lead role on this group, and
EPA hosted the first Principals Working Group meeting on June 6, 2019.
Given that the agencies are continuing to develop and work toward implementation of
approaches to assess the potential risks of pesticides to listed species and their designated critical
habitat, the ecological risk assessment supporting this ID for dithiopyr does not contain a
complete ESA analysis that includes effects determinations for specific listed species or
designated critical habitat. Although EPA has not yet completed effects determinations for
specific species or habitats, for this ID, EPA's evaluation assumed, for all taxa of non-target
wildlife and plants, that listed species and designated critical habitats may be present in the
vicinity of the application of dithiopyr. This will allow EPA to focus its future evaluations on the
types of species where the potential for effects exists once the scientific methods being
developed by the agencies have been fully vetted. Once that occurs, these methods will be
applied to subsequent analyses for dithiopyr as part of completing this registration review.
6 fattPs://www.epa.gov/enda!igered~species/drafi~revised~metfaod~natlonat4evet~endangered~species~risk~assessment~
process
29

-------
Docket Number EPA-HQ-OPP-2013-0750
www.regulations.gov
Appendix D: Endocrine Disruptor Screening Program
As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse
outcomes from exposure to chemicals. Collectively, these studies include acute, sub-chronic and
chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental,
reproductive, and general or systemic toxicity. These studies include endpoints which may be
susceptible to endocrine influence, including effects on endocrine target organ histopathology,
organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss,
and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and
chronic studies that assess growth, developmental and reproductive effects in different
taxonomic groups. As part of its most recent registration decision for dithiopyr, EPA reviewed
these data and selected the most sensitive endpoints for relevant risk assessment scenarios from
the existing hazard database. However, as required by FFDCA  408(p), dithiopyr is subject to
the endocrine screening part of the Endocrine Disruptor Screening Program (EDSP).
EPA has developed the EDSP to determine whether certain substances (including pesticide
active and other ingredients) may have an effect in humans or wildlife similar to an effect
produced by a "naturally occurring estrogen, or other such endocrine effects as the Administrator
may designate." The EDSP employs a two-tiered approach to making the statutorily required
determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a
chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal
systems. Chemicals that go through Tier 1 screening and are found to have the potential to
interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA
will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2
testing is designed to identify any adverse endocrine-related effects caused by the substance and
establish a dose-response relationship between the dose and the E, A, or T effect.
Under FFDCA  408(p), the Agency must screen all pesticide chemicals. Between October 2009
and February 2010, EPA issued test orders/data call-ins for the first group of 67 chemicals,
which contains 58 pesticide active ingredients and 9 inert ingredients. The Agency has reviewed
all the assay data received for the List 1 chemicals and the conclusions of those reviews are
available in the chemical-specific public dockets. A second list of chemicals identified for EDSP
screening was published on June 14, 2013,7 and includes some pesticides scheduled for
Registration Review and chemicals found in water. Neither of these lists should be construed as a
list of known or likely endocrine disruptors. Dithiopyr is not on either list. For further
information on the status of the EDSP, the policies and procedures, the lists of chemicals, future
lists, the test guidelines and the Tier 1 screening battery, please visit EPA website.8
In this ID, EPA is making no human health or environmental safety findings associated with the
EDSP screening of dithiopyr. Before completing this registration review, the Agency will make
an EDSP FFDCA  408(p) determination.
7	See http://www.regiilafions.gov/#idocuinentDetait;D=EPA~HO~OPPT~2009~0477~0Q74 for the final second list of
chemicals.
8	https://www.epa.gov/endocrine-dismption
30

-------